Sports Med 2005; 35 (3): 213-234 0112-1642/05/0003-0213/$34.95/0 REVIEW ARTICLE 2005 Adis Data Information BV. All rights reserved. Challenges in Understanding the Influence of Maximal Power Training on Improving Athletic Performance John Cronin1 and Gord Sleivert2 1 2 New Zealand Institute of Sport and Recreation Research, Auckland University of Technology, Auckland, New Zealand Human Performance Laboratory, Faculty of Kinesiology, University of New Brunswick, Fredericton, New Brunswick, Canada Contents Abstract . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 213 1. Seminal Training Practice and Research . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 214 2. Power-Load Spectrum . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 215 2.1 Upper Body . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 216 2.2 Lower Body . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 219 3. Power and Performance: Cross-Sectional Research . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 220 3.1 Upper Body . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 222 3.2 Lower Body . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 222 3.2.1 Cyclic versus Acyclic Assessment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 222 3.2.2 Absolute versus Relative Power Output . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 224 3.2.3 Maximum Power versus Power Output . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 224 3.2.4 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 226 4. Power and Performance: Training Studies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 226 5. Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 232 Abstract The ability to optimise muscular power output is considered fundamental to successful performance of many athletic and sporting activities. Consequently, a great deal of research has investigated methods to improve power output and its transference to athletic performance. One issue that makes comparisons between studies difficult is the different modes of dynamometry (isometric, isokinetic and isoinertial) used to measure strength and power. However, it is recognised that isokinetic and isometric assessment bear little resemblance to the accelerative/ decelerative motion implicit in limb movement during resistance training and sporting performance. Furthermore, most people who train to increase power would have limited or no access to isometric and/or isokinetic dynamometry. It is for these reasons and for the sake of brevity that the findings of isoinertial (constant gravitational load) research will provide the focus of much of the discussion in this review. One variable that is considered important in increasing power and performance in explosive tasks such as running and jumping is the training load that maximises 214 Cronin & Sleivert the mechanical power output (Pmax) of muscle. However, there are discrepancies in the research as to which load maximises power output during various resistance exercises and whether training at Pmax improves functional performance is debatable. There is also some evidence suggesting that Pmax is affected by the training status of the individuals; however, other strength variables could quite possibly be of greater importance for improving functional performance. If Pmax is found to be important in improving athletic performance, then each individual’s Pmax needs to be determined and they then train at this load. The predilection of research to train all subjects at one load (e.g. 30% one repetition maximum [1RM]) is fundamentally flawed due to inter-individual Pmax differences, which may be ascribed to factors such as training status (strength level) and the exercise (muscle groups) used. Pmax needs to be constantly monitored and adjusted as research suggests that it is transient. In terms of training studies, experienced subjects should be used, volume equated and the outcome measures clearly defined and measured (i.e. mean power and/or peak power). Sport scientists are urged to formulate research designs that result in meaningful and practical information that assists coaches and strength and conditioning practitioners in the development of their athletes. 1. Seminal Training Practice and Research Power can be defined as the amount of work produced per unit time or the product of force and velocity. The development of power and its transference to performance has been the source of interest and discussion for years. Initially, coaches and strength and conditioning practitioners debated the merits of using various loads for the development of power. From the literature there appeared two schools of thought, one that was Western in origin and espoused the use of lighter loads (<50% one repetition maximum [1RM]) for improving power output and athletic performance, whereas Eastern bloc coaches and trainers proposed that heavier loads (50–70% 1RM) were superior. For example, Counsilman[1] a sport scientist and swimming coach, argued that athletes needed to move light loads at high speed, as fast movements activated the fast fibres. Conversely, slow training recruited fibres with slow contraction characteristics, which was thought counter-productive to power training. Similarly, Behm,[2] in discussing the use of surgical tubing for a tennis power programme, suggested that this should be combined with traditional weight training incorporating loads of not more than 50% 2005 Adis Data Information BV. All rights reserved. 1RM. Higher tensions would inhibit the ability of muscles to move quickly, which was thought a fundamental prerequisite of power training. In contrast, some coaches have thought heavier loads are necessary for improved power production. Poprawski[3] compared the strength power results of Edward Sarul, 1983 World Champion in the shotput, to nine well trained shot-putters, which included >21m throwers. While Sarul was slightly stronger than the group average in the bench press (1.4%), snatch (7.9%), power clean (5.3%) and squat (7.8%), the major differences occurred in tests of speed and power at heavy loads in those respective exercises. For example, Sarul’s snatch velocity ranged from 4.13% faster at 20kg than the average to 22.13% faster at 80kg. Similarly, his squat velocity was 2.74% greater at 40kg but 25.71% greater at 140kg. These findings led Poprawski[3] to conclude that movement velocities at higher loads (50–70% 1RM) were critical determinants of athletic success in athletes and training emphasis should be placed on moving lighter loads (50% 1RM) quickly, rather than just striving to lift more weight. Spassov[4] in a discussion of programme design for athletes, stated that experts believe loads of 50–70% 1RM performed at a maximal rate, develop explosive power. Sports Med 2005; 35 (3) Maximal Power Training and Improving Athletic Performance Verkhoshansky and Lazarev[5] in a discussion of Eastern bloc principles for the training of speed and strength believed also that loads of 50–70% 1RM were necessary for the development of ‘explosive strength’. Tidow[6] suggested that heavy loads might be equally as effective as light loads for stimulating fast motor unit activity, as the fastest high threshold units need to be recruited to lift heavy loads. This dichotomy as to which loads (light vs heavy) best maximise power development remains topical and is still the source of much research, but clearly there was a dichotomy of opinion between Eastern and Western bloc power training philosophies. One approach to solving this dichotomy is to study the relationship between force and velocity, since power is the product of both these variables. It is well known that as load increases, the force output of muscle in concentric contractions increases with a concomitant decrease in the velocity of shortening. This phenomenon is known as the force-velocity relationship of muscle.[7] It is thought that maximum power output is the product of optimum force and optimum shortening velocity. For isoinertial contractions, it has been suggested that maximum power output occurs at approximately 30% of maximum shortening velocity or at approximately 30% of maximum isometric force.[7,8] Many researchers have endorsed such loading for maximising power output[9,10] citing the research of Edgerton et al.,[11] Faulkner et al.[12] and Kaneko et al.[13] as support for the utilisation of such loads. However, closer scrutiny of this research leaves one thinking that such conclusions are somewhat misleading. For example, Faulkner et al.[12] certainly reported peak powers at approximately one-third of maximal shortening velocity; however, they do not state at what relative force peak power output occurs (the reader having to extrapolate this information from the graphs provided). Whether power differs significantly across the power-force spectrum is, therefore, unclear. In fact, the power profile of slow and mixed muscles appears similar across loads of 15–50% maximum isometric force.[12] Furthermore, whether such findings are applicable to whole muscle or biarticular movement is questionable. For 2005 Adis Data Information BV. All rights reserved. 215 example, Edgerton et al.,[11] discussing the effects of muscle architecture, depicted maximum power output (Pmax) occurring at a range of isometric forces depending whether the knee extensors (45%), knee flexors (59%), plantar flexors (35%) and dorsiflexors (53%) were studied. These differences were attributed to different fibre lengths that make determination of Pmax difficult, as Pmax is related to fibre shortening velocity, which in turn is related to the number of sarcomeres arranged in series (fibre length). In fact, Edgerton et al.[11] concluded that the complication of variable fibre lengths makes any conclusion regarding power per unit of muscle weight per muscle group of limited value. It would seem some of the previous assumptions made by other authors, based on these research findings, are misplaced. Additionally, it would seem that studying the power output of whole muscle in vivo would have greater practical significance to athletes, coaches and trainers. The power outputs across a spectrum of loads (power-load spectrum) using dynamic multiarticular exercises similar to those used during weight training need to be examined, the results of which should give a greater appreciation of the load that maximises mechanical power output in a functional context. 2. Power-Load Spectrum When studying the power-load relationship, one must be cautious of extrapolating findings from the literature since some research has investigated the power-load relationship indirectly. That is, the relationship between load and power has been investigated, but the load that maximised power output was not reported. For example, using subjects from a weight-training class, Mastropaolo[14] measured power output across loads of 20–100% 1RM. It was reported that subjects were tested using a benchpress motion, although the figure depicting the exercise appears to be a shoulder-press machine. Nonetheless, power profiles based on this movement are detailed in graphical form and the authors concluded (without any apparent statistical support) that the load maximising power output occurred at 40% 1RM. However, loads from 40% to 60% 1RM apSports Med 2005; 35 (3) 216 Cronin & Sleivert pear very similar in power output. Making such interpretations without statistical analysis is problematic. The findings of another often-cited paper that investigated the power-load relationship[13] also need to be interpreted with caution. In this study, 20 male subjects were allotted to four training groups based on their maximum isometric strength. They trained their elbow flexors using either isotonic (0%, 30% or 60%) or isometric (100%) contractions. Peak power of the elbow flexors during concentric muscle actions was observed at intermediate movement velocities of approximately 30% of maximum shortening velocity and 30% of maximum isometric strength.[13] These authors justifiably chose to examine the effects of three loads on Pmax. However, such a design does not mean that 30% 1RM is the load that maximises power output. The load that maximised power output could be anywhere between 30–60% of maximum isometric force, yet many authors[9,10] continue to cite this study as support for light loads (30%) producing maximal mechanical power output. Furthermore, uniarticular motion was examined in this study and untrained subjects were used, which limits generalisability to athletic populations. Also, maximal mechanical dynamic power output was reported based on a percentage of maximal isometric force with no estimates of power in relation to the actual dynamic exercises used in strength training (e.g. squat and bench press) or the athletic performance itself. It is quite likely that the force at which Pmax occurs differs, if expressed relative to a dynamic strength measure (% 1RM). Based on these observations, it seems that the assumption of many authors that a 30% 1RM load maximises power output remains problematic. Investigating the power-load spectrum using dynamic (isoinertial) multiarticular motion would appear to have greater practical significance to strength and conditioning practitioners and sport scientists alike. 2.1 Upper Body The upper-body mean and peak power outputs associated with a spectrum of loads can be observed 2005 Adis Data Information BV. All rights reserved. in table I. In all cases, derivatives of the bench press have been used to study the power-load relationship. As can be observed from table I, the loads reported to optimise Pmax are similar irrespective of subject training status, age and the type of bench-press motion used. Most studies report a band in which Pmax occurs, some research also indicating that loads either side of this band are not significantly different.[15,16] It would seem then that the majority of research reports loads of 30–70% 1RM as the intensities that maximise mean and peak power output. Three observations from table I appear noteworthy. First, greater power outputs are associated with the professional and semi-professional rugby league players, which is no doubt a function of their greater body mass, training status (maximal strength) and, therefore, greater relative loads used for the calculation of Pmax. For example, Baker et al.[15] reported mean body mass and 1RM of 92.0 ± 11.1kg and 129.7 ± 14.3kg, respectively, whereas Cronin et al.[16] reported 89 ± 2.5kg and 86.3 ± 13.7kg, respectively, for club rugby players. Nonetheless the band of loads that maximised mean power output was very similar, although ironically it appears that the Pmax of the better trained (greater maximal strength) rugby league players occurred at a lower percentage of their 1RM. Secondly, it may be that the load that maximises peak power is slightly greater than the load that maximises mean power output. The findings for the lower body (see table II) would certainly support this contention. Thirdly, and related to the first point, it would appear that Pmax may be transient and is affected by the strength status of the population being studied. Mayhew et al.[17] reported that 12 weeks of weight training increased power at a fixed absolute load (Pmax increased). Presumably, as the athletes became stronger, the absolute load became lighter and consequently could be lifted with greater speed. Thus, the increase in Pmax from 40% to 50% 1RM was due to a 10% increase in maximal strength. However, this does not seem the case when relative loads are used. Baker et al.[15] found that the percentage 1RM that maximised power output was significantly lowSports Med 2005; 35 (3) Study Subjects Power measure Maximum power output (% 1RM or load) Maximum power output (W) [mean ± SD] Baker[18] 22 M professional rugby league players (NRL) 27 M college-aged players (SRL) Concentric-only BP throw across loads 40, 50, 60, 70 and 80kg NRL: 70kg (51% 1RM) SRL: 60kg (55% 1RM) NRL: 600 ± 83 SRL: 502 ± 78 Baker et al.[15] 31 professional and semi-professional rugby league players Concentric-only BP throw across loads 40, 50, 60, 70 and 80kg 55% 1RM 46–62% 1RMa 598 ± 99 Cronin et al.[16] 27 M club rugby players Concentric and rebound BP and concentric and rebound BP throws across loads of 30, 40, 50, 60, 70 and 80% 1RM 50–70% 1RM 211–356 Izquierdo et al.[19] 26 middle-aged (mean age 42y) and 21 elderly M (mean age 65y) Concentric only and stretch-shorten cycle BP across loads of 0, 30, 45, 60 and 70% 1RM 30–45% 1RM for both age groups 237–293 Izquierdo et al.[20] 70 M weightlifters, middle-distance runners, handball players, cyclists and controls Concentric only BP across loads of 30, 40, 50, 60, 70, 80, 90 and 100% 1RM 30–45% 1RM 200–391 2.82–4.86 W/kg Newton and Wilson[21] 45 M with at least 6mo bench-press training experience Rebound BP throws across loads of 10, 20, 30, 40, 50, 60, 70, 80, 90 and 100% 1RM 30–40% 1RM Newton et al.[9] 17 M exercise science students with 6mo weight training experience Concentric only and rebound BP throws across loads of 15, 30, 45, 60, 75 and 90% 1RM 30–45% 1RM Bemben et al.[22] 31 M college students Rebound BP across loads of 30, 40, 50, 60, 70 and 80% 1RM 50% 1RM Cronin et al.[16] 27 M club rugby players Concentric and rebound BP and concentric and rebound BP throws across loads of 30, 40, 50, 60, 70 and 80% 1RM 50–60% 1RM 40–70% 1RMa Mayhew et al.[17] 21 M college students Rebound BP across loads of 30–80% 1RM 40% 1RM preintervention 50% 1RM after subjects increased strength Siegel et al.[23] 25 M college students BP across loads of 30, 40, 50, 60, 70, 80 and 90% 1RM 40–60% 1RM Mean power output 560–563 Maximal Power Training and Improving Athletic Performance 2005 Adis Data Information BV. All rights reserved. Table I. Loads that maximised mean and peak power output for the upper body Peak Power Output Similarly effective to loads that maximised power output. b Extrapolated from graph. 1RM = one repetition maximum; BP = bench press; M = male; NRL = national rugby league; SRL = student rugby league. ~500b 217 Sports Med 2005; 35 (3) a 463–626 218 2005 Adis Data Information BV. All rights reserved. Table II. Loads that maximised mean and peak power output for the lower body Study Subjects Power measure Maximum power output (% 1RM) Maximum power output (W) [mean ± SD] Baker et al.[24] 32 professional and semi-professional rugby league players JS across loads of 40, 60, 80 and 100kg – system mass 55–59% 1RM 47–63% 1RMa 1851 ± 210 Izquierdo et al.[19] 26 middle-aged M (mean age 42y) and 21 elderly M (mean age 65y) Concentric only and stretch-shorten cycle halfsquats across loads of 0, 30, 45, 60 and 70% 1RM 60–70% 1RM for both age groups 391–486 Izquierdo et al.[20] 70 M subjects – weightlifters, middledistance runners, handball players, cyclists and controls Concentric only half-squats across loads of 30, 40, 50, 60, 70, 80, 90 and 100% 1RM 45–60% 1RM 385–755 5.5–9.43 W/kg Sleivert and Taingahue[25] 30 M rugby, rugby league and basketball players SS and TS across loads of 30, 40, 50, 60 and 70% 1RM SS: 30–60% 1RM TS: 30–60% 1RM 7.32 ± 1.34 W/kg 7.07 ± 1.25 W/kg Weiss et al.[26] 31 M fitness-trained lifters Concentric-only parallel squats across loads of 30, 60 and 90% 1RM 30% 1RM 1011 ± 100 Bourque and Sleivert[27] 16 males (eight power [six volleyball, two badminton], eight endurance athletes) Parallel concentric JS across loads of 0, 30, 40, 50, 60, 70% 1RM Body mass included Mean: 14% 1RM Mode for power athletes 0% 1RM; mode for endurance athletes 30% 1RM Mean: 5216 ± 1234 Power: 6117 ± 867 Endurance: 4315 ± 808 Esliger and Sleivert[28] 21 (11 M and 10 F) volleyball and basketball players Parallel concentric JS across loads of 30, 40, 50, 60, 70 and 80% 1RM 63% 1RM 1766 ± 479 Siegel et al.[23] 25 M college-aged students Squats across loads of 30, 40, 50, 60, 70, 80 and 90% 1RM 50–70% 1RM ~950b Sleivert and Taingahue[25] 30 M rugby, rugby league and basketball players SS and TS across loads of 30, 40, 50, 60 and 70% 1RM SS: 30–60% 1RM TS: 50–70% 1RM 17.10 ± 3.15 W/kg 17.58 ± 2.85 W/kg Stone et al.[29] 10 subjects with a range of training experience (7wk to >15y) JS and CJ across loads of 10, 20, 30, 40, 50, 60, 70, 80, 90 and 100% 1RM Weakest subjects: 10% 1RM Strongest subjects: 40% 1RM JS: 3482 ± 443 CJ: 3785 ± 376 JS: 5635 ± 2577 CJ: 5391 ± 2566 Thomas et al.[30] 19 untrained F Double leg-press 56–78% 1RM 404 ± 22 31 M fitness-trained lifters Concentric only squats (parallel) 60% 1RM 1711 ± 188 Mean power output Peak power output Weiss et al. a Similarly effective to loads that maximised power output. b Extrapolated from graph. 1RM = one repetition maximum; CJ = countermovement jump; F = females; JS = jump-squats; M = males; SS = split jump-squats; TS = traditional jump-squats. Cronin & Sleivert Sports Med 2005; 35 (3) [26] Maximal Power Training and Improving Athletic Performance er in professional compared with state and cityleague college-aged rugby league players (see table I). Reanalysed data from Baker’s previous research confirmed this finding, the strongest national league players used significantly lower resistances of 47% 1RM compared with the 54% 1RM of less strong national league players.[31] It would seem as athletes become stronger they can produce greater power outputs with any absolute load, but the ability to produce power at a given percentage of their 1RM remains similar as relative resistances increase proportionally to maximum strength levels. 2.2 Lower Body In terms of the lower body, the mean and peak power outputs associated with a range of loads can be observed in table II. The power outputs are reported for a greater variety of movements compared with the upper body, and female power outputs are also represented. The research of Thomas et al.[30] reported a higher Pmax (56–78% 1RM) than most other research, which could be attributed to the subject’s untrained status, female sex or the different movement used (double leg press). However, in terms of the squat and its derivatives, no clear trends are observable between training status, sex, age or type of exercise used. Most studies report a ‘bandwidth’ of loads that maximise power output. Also, unlike in upper-body exercises, peak power has been reported in some instances to occur with no extra load on the bar (unweighted) or only a light load (10–20% 1RM).[27] Bourque and Sleivert[27] recently reported power results much higher and at lighter relative loads than other studies in the literature that have reported lower peak power to occur at heavier relative loads. This is because body mass has been included as part of the resistance the athletes are propelling in the jump-squat. When using ballistic motion such as jump-squats, it is thought appropriate to use system mass to calculate loading intensity, as the subject must propel themselves as well as the bar. Excluding body mass from the equation decreases the total mass component of force, therefore, decreasing total power output. Baker et al.[24] also included body mass in their power 2005 Adis Data Information BV. All rights reserved. 219 calculation and, consistent with the results of Bourque and Sleivert,[27] their calculated mean power values are much higher than other mean power values reported in the literature. The relative load at which they reported mean power to be maximal was, however, much higher than that reported in Bourque and Sleivert’s study and consistent with the other literature. Nevertheless, it should be noted that Baker et al.[24] did not measure power output at loads lighter than 40kg on the bar, so it seems likely that mean power could have been higher at lighter loads using this method of calculation. Other studies have used different calculations to study the load-power relationship. Sleivert and Taingahue[25] calculated net power as force exerted into the bar by the subject: (bar weight + [bar mass × acceleration by subject]) × velocity of bar. It appears that Izquierdo et al.[20] and Weiss et al.[26] calculated power output by simply using bar mass relative to 1RM. The variety of methods used to calculate the power output makes inter-individual comparisons between studies difficult. Clearly a standard method for calculating power in resistance training movements needs to be agreed upon. In the meantime, researchers and practitioners should be aware of the implications resulting from including or excluding body mass in power calculations for exercises occurring in the vertical plane. It seems reasonable to include body mass as part of the resistance athletes are working against for exercises occurring in the vertical plane. If body mass is not taken into account when calculating the load for subjects/athletes, inappropriately heavy loads may be selected for jumpsquats. For upper-body exercises, only a fraction of body mass is propelled, therefore, the load-power relation is potentially different and mean and peak power are likely to occur at higher relative loads. Besides incorporating body mass into the power calculations, there are two other reasons why both Baker et al.[24] and Bourque and Sleivert[27] reported high power outputs in trained power type athletes. First, jump-squats were used in both these studies, and ballistic motion of this type has been shown to increase power output compared with traditional weight-training movements as used by Izquierdo et Sports Med 2005; 35 (3) 220 al.[20] and Weiss et al.[26] where there is no projection of oneself or the bar.[16,32] Secondly, specific neuromuscular adaptations (higher maximal strength or maximum velocity of contraction) may have influenced Pmax. In the recent dissertation of Bourque and Sleivert,[27] the major difference in jump-squat power between power and endurance athletes was the ability of the power athletes to increase the velocity of movement at light loads. Endurance athletes could not increase the velocity of movement and, therefore, power decreased markedly as load decreased. As stated earlier in this section, the method of calculating Pmax has a large influence on both absolute power values and the power-load relationship. Additionally, the relative load that maximises peak power appears higher than the load that maximises mean power. Furthermore, it seems that these factors may be influenced by the type of exercise performed.[25,30] The previously discussed results of Edgerton et al.[11] (see section 1) would support such a contention given that Pmax occurred at different isometric forces depending whether the knee extensors (45%), knee flexors (59%), plantar flexors (35%) or dorsiflexors (53%) were used. Therefore, different exercises (muscle groups) may conceivably have differential power outputs. However, Sleivert and Taingahue[25] explain the differences in maximal peak power between the split and traditional jump-squats reported in their study as being a result of the different starting position of both exercises. That is, the 1RM for the low start position of the traditional squat (149.5 ± 22.6kg) was significantly less than for the split squat (206.6 ± 34.4kg). As a result of the low start position of the traditional squat, the load was difficult to move initially, but comparable velocities to the split squat were achieved later in the lift. Through the range of movement in which peak power occurred, both squats had similar bar velocities and absolute loads, although relative loads were very different. Therefore, traditional squat peak power was maximal at a higher relative load to that of the split squat. It was concluded that the prescription of maximal power training using different exercises and ranges should 2005 Adis Data Information BV. All rights reserved. Cronin & Sleivert detail the loading parameters specific to each individual exercise and that this be based on 1RM assessment similar to the range of motion being prescribed for power training. Qualifying this statement, prescription of the load that optimises Pmax needs to be determined for each individual per exercise. Research reports the mean response (% 1RM = Pmax) for the population being studied, but the ‘bandwidth’ approach to reporting Pmax adopted by most research suggests that there is a range of loads that maximise power output or more likely that there are large inter-individual differences in Pmax. 3. Power and Performance: Cross-Sectional Research Theoretically, the best improvements in athletic tasks that involve significant power output (jumping, sprint, agility and lunge performance) would be gained by training at the load that maximised an individual’s power output using an exercise similar to their athletic activity. However, this presumes that power is the best predictor of athletic performance and, therefore, it is training to improve power output that will best facilitate improved performance. Such an assumption may be misplaced principally because of the diversity of strength/power measures, flawed methodologies and misrepresented research findings. For example, literature dealing with the development of power tends to mix terminology using such terms as power, rate of force development (RFD), explosive strength (maximum force/time to achieve maximum force) and/or impulse interchangeably. One needs only to read some reviews in this area to observe the confusion, power has been associated with the ability to exert great force in a short amount of time (impulse)[33] and confused with explosive strength or rate of force development.[34] Newton and Kraemer,[35] in considering methods to increase muscular power, devote much of their discussion to the importance and development of RFD. Sapega and Drillings,[36] in a discussion of the confusion that abounds concerning the measurement of power, detail how one group of authors have calculated peak power by dividing peak torque by the duration of the contraction and Sports Med 2005; 35 (3) Maximal Power Training and Improving Athletic Performance 221 Table III. Intercorrelation matrix between traditional strength and power measures and Zatsiorsky’s measures of explosive strength[40]a IES IES RC SG AG MP PP MF PF I100 RC 0.84 SG 0.85 0.68 AG 0.80 0.76 0.55 MP 0.75 0.43 0.76 0.54 PP 0.74 0.45 0.73 0.60 0.99 MF 0.80 0.55 0.62 0.52 0.88 0.85 PF 0.86 0.61 0.69 0.63 0.92 0.90 0.99 * I100 0.80 0.54 0.53 0.51 0.89 0.86 0.99 0.99 * MS 0.81 0.56 0.69 0.57 0.85 0.83 0.94 0.94 0.94 a MS * * * * * * * * All correlations are statistically significant at p ≤ 0.05. AG = acceleration gradient; I100 = impulse at 100ms; IES = index of explosive strength; MF = mean force; MP = mean power; MS = maximal strength; PF = peak force; PP = peak power; RC = reactivity coefficient; SG = starting gradient; * indicates 100% perfect correlation. two other studies have used initial RFD as measures of power.[36] Misused terminology and misrepresented research findings are also prevalent in the literature. In a study of 8–12RM weight training performed at different execution speeds, Young and Bilby[37] described their two power measures as maximum RFD and jump height. Neither measure is representative of power output. Indeed, leg power is generally not strongly correlated to jump height and there are limitations in extrapolating results from functional tests such as vertical jump to reflect power. Additionally, some research findings have been interpreted erroneously and, as such, conclusions about power development are questionable. For example, the work of Schmidtbleicher and Buehrle[38] has been used as justification for the use of high loads for the development of power.[9,15] However, this study only measured the changes in maximum force and RFD, and changes in these strength qualities are not necessarily representative of changes in power. Clearly, in each of these cases, different strength capabilities are being investigated or discussed, each representative of different regions of the force-time curve as opposed to power the product of force and velocity. Each of these strength qualities conceivably needs to be developed in a different manner to power. For example, the relationship between traditional measures of force and power, and measures of explosive strength (index of explosive strength, re 2005 Adis Data Information BV. All rights reserved. activity coefficient, start-gradient and accelerationgradient)[39] can be observed from table III. The relationship of these measures of explosive strength to more traditional measures of force and power suggest that the measures of explosive strength for the most part measure different strength qualities than more traditional measures. In particular, the reactivity coefficient (r = 0.43–0.61) and A-gradient (r = 0.52–0.63) have less of their variance explained by force and power. Progressing this contention, it may be that the predilection of research and conditioning practice on improving power may be misplaced. That is, strength qualities such as impulse, RFD or explosive strength may better predict athletic performance and hence it is the development of these qualities that research and strength training should focus on. Further confounding the understanding of power assessment and development is the practical significance of mean and peak power output. The importance of these two variables, their relation to different athletic activities and their development is not well documented and for the most part poorly understood. The first part of this section will critique the literature that has investigated the relationship between power and athletic performance. Thereafter, the relationship between other strength capabilities and athletic performance will be discussed in an effort to clarify the importance of Pmax in improving athletic performance. Sports Med 2005; 35 (3) 222 Cronin & Sleivert 3.1 Upper Body There is a paucity of data concerning the relationship between power measures and upper-body functional performance. This may be a result of the difficulty of finding a suitable upper-body test that is as widely accepted as sprinting or jumping. However, tasks such as throwing shot-puts, balls or unloaded barbells have been used in the literature. For example, Mayhew and colleagues[41-43] have examined the relationship between bench-press power and shot-put throw in a number of studies. They found that bench-press power output using an absolute load of 20kg (~40% 1RM) was non-significantly correlated (r = 0.38) to seated shot-put throw for 64 female college athletes.[42] For 40 college football players, Mayhew et al.[41] found that the seated shotput throw was significantly correlated to benchpress absolute power (r = 0.51) and relative power output (r = 0.66) assessed using a load of 60% 1RM. Mayhew et al.[43] also reported that none of the changes in seated shot-put distance were significantly correlated to increases in bench-press power output (loads 30–80% 1RM) at the conclusion of a 12-week training study. It would seem that the strength of the relationship between power output and seated shot-put throw could possibly be influenced by the mass of the bench-press load, the mass of the shot-put, and the strength and sex of the subjects. Baker[31] found that Pmax was significantly related (r = 0.46) to an incline bench-press throw (20kg), an exercise deemed to indicate upper-body speed capabilities. Pmax explained only 21% of the variance associated with the so-called functional performance measure. It also should be noted that power outputs associated with absolute loads of 40 and 60kg were significantly related to the performance measures (r = 0.42–0.50). Cronin and Owen[44] investigated whether chest-pass distance was related to various strength and power measures of the upper body as measured by a bench-press throw (10kg) on a Smith machine. A significant relationship between maximal strength (r = 0.71), mean power (r = 0.77), peak power (r = 0.80) and impulse (r = 0.81) and the chest pass were reported. It seems that impulse is 2005 Adis Data Information BV. All rights reserved. equally effective in explaining the shared variance between strength/power measures and the performance measure. However, it should be noted that Pmax was not determined in this study but rather the power outputs associated with a concentric-only bench-press throw (10kg) were calculated. 3.2 Lower Body In terms of the lower body, the manner in which power has been calculated and the variety of exercises used to assess power make comparisons between studies difficult (see table IV). As a result, the importance of power as a determinant of athletic performance is difficult to disentangle. One approach to clarify the role of power as a predictor of athletic performance is to discuss power assessment within certain frameworks noting thereafter whether the literature supports such a contention. 3.2.1 Cyclic versus Acyclic Assessment Theoretically, tests of power output that are cyclic in nature, involve the stretch-shorten cycle (SSC) and include horizontal as well as vertical motion should better predict performance in tasks such as running and agility performance. The MargariaKalamen step test is one of the more widely used tests used to calculate anaerobic power: power = (subject mass [kg] × 9.8 N/kg × 1.02 [vertical distance between test stairs])/time taken to ascend test stairs. Significant correlations (r = –0.43 to –0.71) were reported between power and sprint and agility performance using this test, only when power output was expressed relative to mass (see Mayhew et al.,[42] table II). The highest correlation was reported between the 36.5m (40-yard) dash time and the step test. This makes sense as theoretically the greater the approach velocity during the test, the greater the vertical velocity and, therefore, power output. However, there is still a great deal of unexplained variance (50–81%) between the step test and the measures of performance. Some studies have reported that approach velocity and power output are only moderately correlated[50] and, therefore, it has been speculated that something more than vertical velocity accounts for power production. The shared variSports Med 2005; 35 (3) Subjects Power measure Performance measure Baker and Nance[45] 20 professional rugby league players Loaded jump-squats across loads of 40, 60, 80 and 100kg Absolute (W) Relative (W/kg) 10m sprint time 40m sprint time r –0.02 –0.52 –0.02 –0.52 Chelly and Denis[46] 11 M handball players Average hopping power Average treadmill power (W/kg) Average treadmill power Maximal track running velocity 0.66* 0.20 (NS) 0.73* Driss et al.[47] 18 M volleyball players Anaerobic power (Pmax) on cycle (6 sec) expressed as W/kg Vertical Jump 0.75** Kukolj et al.[48] 24 well conditioned M PE students Average leg power per kg of body mass from continuous jumping protocol according to Bosco et al.[49] 0–15m time 15–30m time 0.03 (NS) 0.26 (NS) Mayhew et al.[50] 53 football players Anaerobic power (W) Anaerobic power (W/kg) Margaria-Kalamen step test 9m (10yd) dash time 36.5m (40yd) dash time Agility – modified Missouri State agility run 0.16 (NS) –065* 0.21 (NS) –071* 0.22 (NS) –0.43* Meckel et al.[51] 20 F track athletes 10 recreationally trained F Wingate anaerobic test (30 sec): maximum power (W/kg) 100m sprint from standing start –0.88 Nesser et al.[52] 20 sportsmen Wingate 10 sec anaerobic test: anaerobic power (W/kg) 40m sprint time –0.46* Sleivert and Taingahue[25] 30 M rugby league, rugby, and basketball players Split squat Traditional squat 5m time 5m time MP: –0.68** PP: –0.65** MP: –0.64** PP: –0.66** Thomas et al.[30] 19 untrained F Double leg-press peak power output Vertical jump Sprint 36.5m (40yd) 0.73 (p < 0.004) 0.14 (p < 0.573) Young et al.[53] 18 footballers CMJ (power) 20m straight sprint 4 × 20m sprints bouncing football or changing direction (agility) 0.66 (NS) to to to to –0.08 (NS) –0.61* –0.17 (NS) –0.76* CMJ = counter-movement jump; F = females; M = males; MP = mean power; NS = not significant; PE = physical education; Pmax = maximal power output; PP = peak power; * p < 0.05; ** p < 0.001. 223 Sports Med 2005; 35 (3) Study Maximal Power Training and Improving Athletic Performance 2005 Adis Data Information BV. All rights reserved. Table IV. Relationship between measures of power and performance for the lower body 224 Cronin & Sleivert ance between the power and performance measures would certainly support such a contention. Other studies that have used cyclic SSC assessment include Chelly and Denis[46] who used a treadmill sprint test and Kukolj et al.[48] who used continuous jumping protocol. The best single predictor of maximal running velocity was treadmill forward leg power (r = 0.73) in Chelly’s study; however, this only accounted for 53% of the variance. Kukolj et al.[48] found no significant relationship between their power measures and sprint times. Another test of anaerobic power that is cyclic in nature but does not involve SSC motion is the Wingate cycle test. Three studies[47,51,52] used the power output from the Wingate test to predict jump and sprint performance. Once more the diversity in testing procedures is apparent, even when the same test is used. All three studies calculated power output over different time periods. Furthermore Driss et al.[47] determined Pmax and used this measure for comparisons, Nesser et al.[52] used peak power during their 10-second work bout and Meckel et al.[51] used the highest work performed during any 5-second work interval. The variety in outcome measures between studies also makes comparisons difficult and it is no wonder a wide range of correlations between power and performance measures were reported (r = –0.46 to –0.88). From the studies represented in table IV it appears that the power outputs associated with cyclic type motion do not predict performance any better than acyclic measures. 3.2.2 Absolute versus Relative Power Output It may be that power needs to be normalised to body mass for power output to be truly representative of the power needed to run and jump. Once more, the literature is confusing. Two studies[45,46] have represented their power outputs in absolute (W) and relative (W/kg) terms. The absolute power outputs of Baker and Nance[45] were not significantly related to 10 or 40m sprint performance; however, when expressed relative to body mass, significant relationships were reported (r = –0.52 to –0.76), likely because body mass must be accelerated in sprinting. However, some of the findings of Chelly and Denis[46] are the antithesis of Baker and 2005 Adis Data Information BV. All rights reserved. Nance[45] with the absolute power values being the only measures significantly related to maximal velocity in a 40m sprint. Both studies investigated the relationship between power output and sprint times of athletes over fairly similar distances, the differences in dynamometry (jump-squats vs treadmill sprints) being the major difference between studies. It should be pointed out that in the study of Chelley and Denis,[46] although relative power was not correlated to maximal running velocity, it was strongly correlated to sprint acceleration (r = 0.80). Of the other studies that expressed power output relative to body mass, the results were mixed with high,[51] moderate,[47] low[52] or non-significant relationships[48] to measures of performance reported. There appears to be no clear consensus as to the importance of normalising power output to body mass for predicting performance. Also, most normalised power outputs (the exception being Meckel et al.[51]) explained <57% of the common variance associated with the performance measure. Meckel et al.[51] studied a very large group (n = 30) of mixed sprint ability (mean 100m time ranged from 11.1 seconds in the fastest group [n = 10] to 14.2 seconds in the slowest group [n = 10]). Heterogeneity of subjects may have contributed to the high correlations reported. 3.2.3 Maximum Power versus Power Output The low shared variance between power output and performance measures reported previously may be due to the fact that most of the studies have not determined Pmax for the assessment that is predicting the performance measure. Baker and Nance[45] reported that Pmax/kg was significantly related to 10m (r = –0.56) and 40m (r = –0.76) sprint performance. However, the strength of these correlations were very similar to the correlations associated with other loads and in the case of 10m sprint performance, the correlations between Pmax and speed were lower than the correlations reported for some of the other loads. Driss et al.[47] also determined Pmax for a 6-second sprint test on a cycle at different braking forces. The braking force that maximised Pmax was recorded and related to functional performance (vertical jump). Unlike Baker and Nance,[45] the other Sports Med 2005; 35 (3) Maximal Power Training and Improving Athletic Performance power outputs associated with various loads and subsequent relationships were not reported in this study, therefore, conclusions cannot be made as to the significance of the load that optimises Pmax in relation to other loads. In both studies, however, Pmax accounted for <58% of the shared variance between the performance measures. It appears that none of these frameworks clarify the importance of power output or Pmax as predictors of performance more so than the other. Given the great variety of assessment techniques, it might have been expected that one type of assessment may predict performance to better effect. This was not the case, the greatest shared variance between a measure of power and performance being 77% and most coefficients of determinations approximately 50% or less. It may be that power is not an important determinant of performance and other strength measures may be of equal or greater importance or power measurements have not be appropriate for the performance. It has been suggested that for activities that require fast force production (100–300ms) such as throwing, jumping and sprinting,[6] that the rate at which force is developed is the most important determinant of athletic success.[54] Wilson et al.[55] investigated the relationship of a series of isometric, concentric and SSC rate of force development tests performed in an upright squat position to sprinting performance. Of the 20 force-time variables generated using a modified Smith machine over a force platform, the concentric force at 30ms was the only measure significantly correlated to sprint performance (r = –0.616) and, in addition to concentric maximum RFD, were the only measures able to effectively discriminate between good and poor performers.[55] The authors emphasise the superiority of concentric RFD tests over and above isometric and SSC RFD tests and suggest their inclusion in sport science test batteries. It should be remembered, however, that concentric RFD and force at 30ms explained <38% of the variance associated with 30m sprint performance. Furthermore, this type of methodology does not clarify whether power is a better predictor of athletic performance, as power was not 2005 Adis Data Information BV. All rights reserved. 225 measured. Reviewing research that has investigated the ability of a variety of strength and power measures to predict athletic performance, may give better insight into the importance of power as a determinant of athletic success. Cronin et al.[40] assessed the strength, power and explosive strength of the leg musculature on a supine squat and related these measures to lunge performance (lunge foot contact times: 0.354 sec + 0.063). The only significant strength predictors of lunge performance were all explosive strength measures (index of explosive strength [r = 0.62], reactivity coefficient [r = 0.61], starting gradient [r = 0.69] and acceleration gradient [r = 0.59]). Maximal strength, mean and peak power were not significantly related to performance of this movement.[40] In another study, Sleivert and Taingahue[25] investigated the relationship between sprint start performance (5m sprint time) and strength and power variables determined from concentric jump-squats in 30 male athletes. Both average and peak power expressed relative to body mass were significantly related to 5m sprint time (r = –0.64 to –0.68). Force (r = 0.59) and bar velocity (r = 0.40) were also significantly related to 5m sprint time. However, with the exception of peak force, these relationships were much less substantial than those demonstrated for average and peak power. During the sprint start, the body had to be accelerated rapidly from stationary and the propulsive impulse was large, so there may have been a greater reliance on high force production as opposed to high movement velocity. Young et al.[56] using a similar methodology to Wilson et al.[55] investigated the relationship between 27 strength and power measures and the sprinting performance of 20 elite junior track and field athletes (11 males and 9 females). There was no mention whether the pooling of the male and female subjects were investigated for bipolar distribution (by sex), which can result in artificially high correlations. Therefore, the magnitude of the correlations need to be interpreted with caution. Young and colleagues[56] assessed vertical jumping movements utilising purely concentric, SSC and isometric contractions performed over a force platform, found Sports Med 2005; 35 (3) 226 Cronin & Sleivert that concentric strength measures were the best predictors of sprint performance. The best predictors of starting performance (time to 2.5m) were all obtained from a concentric-only jump-squat and included three force measures (maximum dynamic strength/weight [r = –0.86], force in 100 ms/weight [r = –0.73], maximum force [r = –0.72] and one power measure (average power/weight [r = –0.74]). The single best predictors of maximum sprinting speed were the force relative to bodyweight generated after 100ms from the start of the concentric jump movement (r = –0.80) and maximum force (r = –0.79). Average power relative to bodyweight was also strongly related to maximum velocity (r = –0.79). Together, the findings of these studies suggest that for many types of activities, various rates of force development and maximal force measures may be as predictive of performance as measures of maximal power. The magnitude of these relationships appear to depend upon the kinetics and kinematics of the performance in question, and specificity of neuromuscular demand appears to be a critical factor in determining the strength or power attribute that best predicts performance. It should be remembered, however, that just because a strength or power attribute is related to performance, that does not necessarily indicate that training that particular attribute will enhance performance. 3.2.4 Summary Implicit in the small number of meaningful correlations and large amount of unexplained variance in the data of table IV is that sport scientists need to formulate better methods, models and theories to contribute significantly to knowledge that is useful to athletes and their coaches in terms of power and performance. It has been suggested that sport scientists adopt a specific functional term to denote the ability to perform high-velocity explosive forcegenerating movements and limit the term ‘power’ to its correct usage as defined by Newtonian mechanics.[36] Whether this is necessary is debatable. It may be that the preoccupation of correlational studies to find the best power predictors of functional performance is fundamentally flawed. First, one power measure cannot adequately express or provide insight 2005 Adis Data Information BV. All rights reserved. into all the mechanisms responsible for performance of a task. Secondly, other factors such as strength measures, body mass, flexibility and leg length will have diverse effects on the statistical models. Based on these results, it is suggested that the sports trainer, sport scientist or clinician should not rely solely on a single power measurement to predict performance or readiness to return to activity after injury. Rather, research needs to determine the influence of these other factors on athletic performance. It may be that several factors in combination with power measures will provide the best predictive capabilities of functional performance. Therefore, the challenge is to develop assessment batteries that provide insights into the key mechanisms responsible for the performance of a task. It must also be remembered that a significant relationship to performance does not imply that a particular strength or power attribute, when loaded during training, will enhance performance. Only longitudinal data from training studies can provide information regarding optimal training methods, if indeed optimal methods exist. 4. Power and Performance: Training Studies Research that has investigated the development of power is typified by a great deal of variation in the methodological approaches used. The scope of this variation makes comparisons difficult and hence definitive conclusions practically impossible. For example, the vast majority of research has been relatively short in duration (8–12 weeks) and, therefore, the application of findings to long-term training is questionable as the influence of neural and morphological mechanisms change with training duration.[57] Research in this area is also typified by a wide spectrum of loading parameters that include differences in: • volume • intensity (% 1RM) • total work output • tempo of concentric-eccentric contractions • frequency • rest/recovery time – density • type of contractions. Sports Med 2005; 35 (3) Maximal Power Training and Improving Athletic Performance 227 Further confounding our understanding in this area are the modes of dynamometry used and variety of strength power measures reported. These issues have been discussed in section 3. Finally, many different muscle groups have been studied, limiting the ability to generalise results, especially in the case of uni- and bi-articular muscles. To discuss each of these limitations is outside the scope of this article. However, a brief mention will be made of some issues that are thought influential to subsequent discussion. with plyometric training on a variety of performance measures. Conversely Komi et al.[61] compared the effect of heavy-load training versus light-load training combined with explosive jump training on various performance measures. Any performance changes, however, cannot be attributed to a load effect as one treatment group has incorporated additional plyometric training. Unfortunately this type of methodology is not uncommon and as such does not offer insight into specific loading intensities that affect power and performance. First, a clear understanding of each research methodology needs to be realised, so as the interpretation and application of their findings are not misrepresented. For example, the study of Schmidtbleicher and Buerhle[38] compared the effects of three types of training regimes (maximum load [90–100% maximal voluntary contraction, MVC], power load [45% MVC] and hypertrophy load [70% MVC]) on various neuromechanical and morphological variables. In terms of tracking these changes, an isolated isometric elbow extension movement was used. Consequently, power was not assessed as no movement took place. Furthermore, isometric and dynamic contractions have been shown to differ in terms of their physiology and neuromechanics.[58] Similarly, the findings of Hakkinen et al.[59] are used to support the use of light-load explosive jump training for power development. However, there were no other training or control groups cited in this paper and the changes in performance from the 24 weeks of training were tracked by measuring isometric force and various force-time parameters. These articles, however, are often quoted in power training literature even though power has not been measured. The application of such findings for improving the power of multi-articular dynamic motion would appear problematic on a number of counts. Further confounding our understanding of the effects of resistance training on the development of power is the preponderance of research using novice weight trainers or students as subjects (see table V). This is due to the accessibility of such subjects to researchers. Novice subjects and/or student populations are generally easy to access and it is easy to have a control group in such designs. However, it is more problematic to find a suitable cohort of subjects from an athletic population and practically impossible to ask a group of athletes to cease training and act as controls. Nonetheless, it has been shown that novices respond in a generic manner to a very broad range of resistance training stimuli.[62,63] Thus, the validity of generalising findings from novice subjects to athletes with experience in weight training needs to be done so with caution as the findings may in fact be compromised by the trainability of the novice subjects. Another common methodological problem when studying the effect of load is that authors combine training methods, which make the effects of the independent variable impossible to disentangle. For example, Lyttle et al.[60] investigated the effects of maximal power training (30% 1RM) versus heavyload training (6–10RM or 75–83% 1RM) combined 2005 Adis Data Information BV. All rights reserved. Volume is commonly expressed as the total product of repetitions, sets and load (% 1RM). Equating by volume is the most common method by which research compares the effect of load on various outcome measures. Alternative methods include equating with total time under tension as measured by electromyographic (EMG) activity or total mechanical work performed.[67] A great deal of research has failed to equate loading between training protocols in any form[38,65,69,70] and, as a result, the findings of such research must also be interpreted with caution especially if the effect of load is being investigated. For example, Harris et al.[65] studied the effects of different training protocols on well trained subjects. One group used heavy-load squats Sports Med 2005; 35 (3) 228 Cronin & Sleivert Table V. Studies that have examined the effect of load on power output and performance Study Subjects Cronin et al.[64] 21 F provincial netball players (1) 60% 1RM with no recent weight-training (2) 80% 1RM experience (3) Control Equivolume training for 10wk Training loads used Mean and peak power Netball throw velocity Power and performance measures Harris et al.[65] 51 university football players with at least 1y of weighttraining experience (1) 30% 1RM (2) 80% 1RM (3) Com 30% and 80% 1RM Not equivolume – 13wk Average VJ power Peak VJ power Standing long jump MK step test Agility test 30m sprint McBride et al.[66] 26 athletic men with 2–4y strength-training experience (1) 30% 1RM (2) 80% 1RM (3) Control Equivolume training for 8wk Peak power 20m sprint time Agility T-test Moss et al.[67] 31 well trained PE students (1) 15% 1RM (2) 35% 1RM (3) 90% 1RM Equivolume training for 9wk Power-load spectrum Scmidtbleicher and Haralambie[68] 30 M PE students (1) 30% MVC (2) 90–100% MVC (3) Control Equivolume training for 8wk No power measures Maximal speed of push-off movement Schmidtbleicher and Buehrle[38] 59 M students (1) 45% MVC (2) 70% MVC (3) 90–100% MVC Not equivolume – 12wk No power measures No performance measures Wilson et al.[69] 64 subjects with 1y weighttraining experience (1) 30% 1RM No measures of power (2) 6–10RM = 75–83% 1RM JS Ht (3) Plyometric CMJ Ht (4) Control Sprint and cycle tests Not equivolume – 10wk 1RM = one repetition maximum; CMJ = counter-movement jump; Com = combined training; F = females; Ht = height; JS = jump-squat; M = males; MK = Margaria-Kalamen step test; MVC = maximal voluntary contraction; PE = physical education; VJ = vertical jump. of 80–85% 1RM (high force [HF]), one with lighter load squats of approximately 30% 1RM (high power [HP]), and one with a combination (COM) of training methods. Subjects were instructed to perform all lifts as explosively as possible although not actually jump. Pre- and post-training tests included: 1RM squat, 1RM one-quarter squat, 1RM mid-thigh pull and various tests of speed and jump height. After 9 weeks of training it was observed that performance changes reflected contraction force specificity. That is, the COM and HF groups increased 1RM strength significantly more than the HP group (24.7%, 21.9% and 9.6% for COM and HF and HP, respectively, average increase across squat and one-quarter squat 1RM). However, for some low-force, high-velocity measures of functional performance such as the 2005 Adis Data Information BV. All rights reserved. standing long jump, significantly greater increases in the HP (3.45%) group than COM (1.63%) or HF (1.29%) groups were observed. These differential training effects are interesting; however, it may be that the noted training effects were not due to the different kinematics and kinetics characteristics of the various training protocols, but rather the different training volumes of each group. Wilson et al.[69] is an often-quoted study that experiences the same problem. These researchers examined the effects of three different training modes on strength and power outputs over the course of 10 weeks of training. Previously trained subjects were divided into three subject groups. One trained with traditional ‘heavy’ (6–10RM) squats (TR), one with jump-squats at Pmax (around 30% of Sports Med 2005; 35 (3) Maximal Power Training and Improving Athletic Performance maximum isometric force [MP]) and one with plyometric unloaded depth jumps (0.2–0.8m [PL]). Tests before and after the training period included sprint time, vertical jump height and peak power in a 6-second cycle test. The results indicated that the MP training group demonstrated the best overall improvements in functional performance. Increases in countermovement jumps (17.6%) and jumpsquats (15.2%) were significantly greater than the TR (4.8% and 6.3%) and PL (10.3% and 6.5%) groups. They concluded after a training study that compared heavy weight training (6–10RM), plyometric training (drop jumps from 0.2–0.8m) and maximum power training (30% 1RM) that the Pmax training produced the best overall results.[69] Once more, intensity and volume have not been equated and, therefore, it is impossible to disentangle the training effects. That is, the results from such studies are difficult to interpret as the reported differences between various training protocols may in fact be contaminated by differences in training volume, rather than the specific kinematic and kinetic characteristics of the different loading intensities. Making conclusions about the efficacy and/or adaptations of various training protocols that are not equated in some manner would appear highly questionable. Further complicating our understanding in this area is that changes in performance may be related to the movement pattern used rather than differences in loading intensity. For example, in the Wilson et al.[69] article, it may be that the superior performance of the maximum power groups was not due to training at the ‘optimal load’ but rather that jump-squat training (ballistic training) offers greater movement pattern specificity than more traditional strengthtraining methods. Traditional strength-training techniques in which a bar is held at the completion of the motion have been criticised due to large decelerations during the concentric phase, proportional to the load and, therefore, velocity of movement.[32,71] Strength training that allows the projection of the load avoids this problem by allowing the athlete to accelerate the bar throughout a greater range of movement. Such training has been described as ‘bal 2005 Adis Data Information BV. All rights reserved. 229 listic’ strength training[35] and is thought superior to traditional strength-training methods as the velocity and acceleration/deceleration profiles better approximate the explosive movements used in athletic performance.[21,32] Careful consideration also needs to be given to the type of isoinertial assessment used in training studies, as assessments must balance between being specific to the functional task whilst being sufficiently different from training so that it does not advantage one of the training groups. For example, it can reasonably be expected that a group training with heavy loads would achieve greater improvements in 1RM than a group training with lighter loads. Therefore, assessments should either include tests across a range of loads or at a ‘neutral’ load that will not bias the results for any particular group. Finally, all the papers cited in table V experience a basic but fundamental problem if the effect of training at Pmax is to be established. No paper has established Pmax for their respective subjects, the training load selected has been based on previous research. The perils of such an approach have been discussed throughout this paper with many findings such as Edgerton et al.,[11] Faulkner et al.,[12] Kaneko et al.,[13] Schmidtbleicher and Buehrle,[38] misinterpreted and/or misrepresented. The dangers of such an approach are further reinforced if tables I and II are observed, that is which load (% 1RM) should be used as Pmax for a training study. If the effects of Pmax training are to be understood, Pmax needs to be determined specific to the population and training exercise used. The power loads selected for study have mostly been based on research (e.g. Kaneko et al.[13]) that cites the superiority of lighter loads (30–45% 1RM). Tables I and II and previous discussions of research such as that of Kaneko et al.[13] would suggest that this is not advisable practice. Only one study[64] based their selection of Pmax on their own previous research using similar athletes and assessment equipment to their original research.[16] In this study, the effects of heavy-load training (80% 1RM) and maximum power training (60% 1RM) on the power and chest-pass performance of semi-elite netball players were compared. Sports Med 2005; 35 (3) 230 Cronin & Sleivert Significantly greater mean and peak power outputs (40% 1RM bench-press throw) were observed for the heavy-load group; however, no significant differences in chest-pass throw velocity between training groups were found. However, it should be noted that the players had little or no weight-training experience. The types of problems described in this section are symptomatic of research in this area, the reader having to be discerning in their choice of literature to shape their knowledge and practice. To gain a true appreciation of the effect of load on power development, research methodologies need to equate the load lifted in some manner. Ideally, well trained subjects should be trained at different loads (% 1RM), the effects of which need to be reported as changes in mean and/or peak power and/or changes in functional performance. Unfortunately, the number of studies that have adopted such an approach are few (see table V) and, as mentioned previously, none of these studies determined or trained at Pmax. Therefore, the importance of Pmax remains a mystery. Nonetheless, two studies seem to have resolved some of the limitations highlighted in previous sections and may offer insights into optimising the load selected during resistance training strategies to develop maximal power and enhance performance. [67] Moss et al. had three groups of subjects train the elbow flexors of the non-dominant arm while the dominant arm served as a control. The three groups trained at 90% 1RM for two repetitions (G90), at 35% 1RM for seven repetitions (G35) and at 15% 1RM for 15 repetitions (G15), respectively. All groups trained with three to five sets and were equated for total time under tension based on EMG activity (muscle activation). Subjects were encouraged to perform each lift as fast as possible, but the weight was held rather than projected. Measurements before and after the study included 1RM and various force and power outputs. Power was tested across a range of loads from 2.5kg to 90% 1RM and increased for all loads tested in G90 and G35. An increase in a lighter range of loads from 15% to 50% 1RM was observed for G15. The increases in power output were not significantly different between the 2005 Adis Data Information BV. All rights reserved. three groups at loads ≤50% 1RM but for the higher loads (70% and 90% 1RM) the increase was significantly larger for G90 and G35 compared with G15. In essence, the findings illustrate loads of 35% and 90% 1RM were equally effective in improving power output across a spectrum of loads. Another study investigating the effects of heavy(80% 1RM) versus light-load (30% 1RM) training on strength, power and speed in experienced weight trainers was conducted by McBride et al.[66] Jumpsquats were used for both training and testing, and groups were equated for volume using sets × repetitions × load (%RM). After 8 weeks of training, both groups increased 1RM significantly (10.17% and 8.23% for 80% 1RM and 30% 1RM groups, respectively) with no significant difference between groups. Similarly, there were no significant between-group differences in peak force, peak power or jump height pre- and post-training. Of the three sprint (5, 10 and 20m sprint time) and agility (T-test time) measures, the 30% 1RM training proved superior to 80% 1RM training on only one measure (10m sprint time). The results of these two studies suggest that there is very little difference in the effects of heavy- and light-load training in terms of power and performance. The lack of a differential training effect in these studies using quite different loads may be explained if training velocity and actual movement velocity of a task are compared. For example, the velocities attained during a concentric-only bench-press throw and a rebound bench-press throw on a modified Smith-Press machine can be observed from figure 1.[64] Such motion has been reported to more closely simulate the velocity and acceleration profiles associated with throwing.[32] The velocity profiles obtained from these 27 male athletes are similar to those recorded in other research of this kind.[9,32] For sports-specific motion that uses muscles similar to the bench press the comparison of actual movement velocity to training velocity make for interesting analysis. Ritzdorf[72] details release velocities of 13 m/sec for the shot-put motion. Average release velocities of 11.98 m/sec for the chest pass of semi-elite female netball players have also been Sports Med 2005; 35 (3) Maximal Power Training and Improving Athletic Performance 231 1.1 Concentric bench-press throw Rebound bench-press throw 1.0 Average velocity (m/sec) 0.9 0.8 0.7 0.6 0.5 0.4 0.3 0.2 0.1 0 30 40 50 60 70 80 Percentage 1RM Fig. 1. Average velocities and standard deviations associated with the concentric bench-press throw and the rebound bench-press throw over a range of loading intensities (30–80% one repetition maximum [1RM]). reported.[64] Furthermore, other studies (as reported by Ritzdorf[72]) have reported that the segment velocities (shoulder, elbow and hand) combined to produce racquet head velocities of approximately 30 m/sec for the tennis serve. It would seem that there are clear differences between the velocities associated with the most common strength-training loading intensities (30–80% 1RM) and the actual movement velocity of a sport-specific task. There is no doubt that resistance strength training can improve functional performance. However, the importance of load in terms of velocity specificity would appear questionable, due to the disparity between the actual movement velocities of most athletic tasks and the training velocities achieved during weight training. It may be that load is not as important as many think and other factors may be more important to better develop and explain improvement to functional performance. For example, as suggested in section 3, it may be that rate of force development rather than power output is a more important determinant of athletic success. Newton and Kraemer[35] stated that heavy loading (70–120% 1RM) does not improve the maximum rate of force development, rather exercises such as explosive jump training using resistances of 30–60% 1RM best increase the ability to 2005 Adis Data Information BV. All rights reserved. rapidly develop force. This assertion must be interpreted cautiously as Schmidtbleicher and Buehrle[38] found the greatest improvements in RFD resulted from maximum load training (90–100% MVC) as opposed to maximum power (45% MVC) training (34% and 11% improvements, respectively). It should be remembered that rate of force development can be independent of external movement velocity. In addition, maximal rate of force development and motor unit activation in a maximum effort contraction is relatively constant for an individual and is generally not influenced by the external load or speed of movement.[73] In Schmidtbleicher and Buehrle’s study[38] both groups were instructed to develop their contractions as fast as possible. It may be that irrespective of load and limb velocity, the repeated intent to move ‘explosively’ is the important stimulus for muscular adaptation. The findings of Behm and Sale[74] support such a notion, as they found that regardless of the actual velocity of movement (isometric versus isokinetic), it was the intention to execute a high-velocity movement, which resulted in high-velocity adaptation and substantial increases (26%) in rate of force development. Along these lines, it has been recently shown with surface electromyography, that at loads between 30–80% Sports Med 2005; 35 (3) 232 Cronin & Sleivert 1RM, power, force and velocity values differ, but muscular activation is similar during maximal effort ballistic jump-squats.[19] Thus, when the intent to move is maximal, any differences in training effects due to loading differences are likely due to differences in the mechanical stimuli at the muscle, not activation differences. 5. Conclusions Many problems have been magnified throughout this article that currently exist within this field of study. From the use of fundamental definitions and terminology to training studies, the literature appears hewn with confusion and methodological problems. It is hoped that this article has eliminated some of this confusion and clarified the type of research needed if we are to advance our knowledge and practice on the importance of maximising power output and its transference to athletic performance. Sport scientists are urged to formulate research designs that result in meaningful and practical information that assists coaches and strength and conditioning practitioners in the development of their athletes. In summary, it is apparent there is a need for a great deal more research on the importance of training at Pmax and whether it advantages athletic performance over and above other loading intensities. First, the importance of Pmax to athletic performance needs to be established. It must be remembered that power is only one aspect that affects performance and it is quite likely that other strength measures may be equally if not more important for determining the success of certain tasks. The coach and/or sport scientist must be aware of this and identify those strength qualities that are critical determinants of their athletic activity and thereafter devise appropriate assessment strategies and training programmes so as these determinants are improved in a systematic fashion. It is suggested that instead of using a correlational analysis that a regression approach be used to find predictor models that include other anthropometric and physiological (including other strength qualities) measures. As such, a battery of two or more tests may predict athletic perform 2005 Adis Data Information BV. All rights reserved. ance to better effect and direct assessment and conditioning practice in a more efficient and systematic fashion. If Pmax is found to be important, then each individual’s Pmax needs to be determined and they then train at this load. The predilection of research to train all subjects at one load (e.g. 30% 1RM) is fundamentally flawed due to inter-individual Pmax differences, which may be ascribed to factors such as training status (strength level) and the exercise (muscle groups) used. Pmax needs to be constantly monitored and adjusted as research suggests that it is transient. In terms of training studies, experienced subjects should be used, volume equated and the outcome measures clearly defined and measured (i.e. mean power and/or peak power). Until training studies address the limitations discussed throughout this paper, the best and safest course of action for those interested in improving the power output of muscle may be to use a mixed training strategy using both heavy and light loads. Realising that all human movement is an integration of force and velocity, such an approach is intuitively appealing. That is, most sports involve a mixture of activities that span the force-velocity capability of muscle. For example, the shot-putter has to drive their quite sizeable mass through the circle before throwing a relatively light shot-put. Rugby players not only have to wrestle and tackle each other but also kick and throw a ball. Intuitively, it would seem prudent to continuously adjust the resistances used for power training, as athletic performance is typified by many force-velocity characteristics. Furthermore, as one of the principles of training is variation (periodisation) this approach would seem most logical. Acknowledgements No sources of funding were used to assist in the preparation of this review. The authors have no conflicts of interest that are directly relevant to the content of this review. References 1. Counsilman JE. The importance of speed in exercise. Athletic J 1976; 56 (9): 72-5 2. Behm DG. Surgical tubing for sport and velocity specific training. Nat Strength Cond Assoc J 1988; 10 (4): 66-70 Sports Med 2005; 35 (3) Maximal Power Training and Improving Athletic Performance 3. Poprawski B. Aspects of strength, power and speed in shot put training. Nat Strength Cond Assoc J 1987; 9 (6): 39-41 4. Spassov A. Special considerations when programming for strength and power for athletes: part 1. Nat Strength Cond Assoc J 1988; 10 (4): 58-61 5. Verkhoshansky YV, Lazarev VV. Principles of planning speed and strength/speed endurance training in sports. Nat Strength Cond Assoc J 1989; 11 (2): 58-61 6. Tidow G. Aspects of strength training in athletics. N Studies Athl 1990; 1: 93-110 7. Hill AV. The heat of shortening and the dynamic constants of muscle. Proc R Soc Lond 1938; 126: 136-95 8. Josephson RK. Contraction dynamics and power output of skeletal muscle. Annu Rev Physiol 1993; 55: 527-46 9. Newton R, Murphy A, Humphries B, et al. Influence of load and stretch shortening cycle on the kinematics, kinetics and muscle activation that occurs during explosive upper-body movements. J Appl Physiol 1997; 75: 333-42 10. Toji H, Suei K, Kaneko M. Effects of combined training loads on relations among force, velocity, and power development. Can J Appl Physiol 1997; 22 (4): 328-36 11. Edgerton VR, Roy RR, Gregor RJ, et al. Morphological basis of skeletal muscle power output. In: Jones NL, McCartney N, McComas AJ, editors. Human muscle power. Champaign (IL): Human Kinetics; 1986: 43-63 12. Faulkner JA, Claflin DR, Cully KK. Power output of fast and slow fibres from human skeletal muscles. In: Jones NL, McCartney N, McComas AJ, editors. Human muscle power. Champaign (IL): Human Kinetics, 1986: 81-93 13. Kaneko M, Fuchimoto T, Toji H, et al. Training effect of different loads on the force-velocity relationship and mechanical power output in human muscle. Scand J Sports Sci 1983; 5: 50-5 14. Mastropaolo JA. A test of the maximum-power stimulus theory of strength. Eur J Appl Physiol 1992; 65: 415-20 15. Baker D, Nance S, Moore M. The load that maximizes the average mechanical power output during explosive bench press throws in highly trained athletes. J Strength Cond Res 2001; 15 (1): 20-4 16. Cronin JB, McNair PJ, Marshall RN. Developing explosive power: a comparison of technique and training. J Sci Med Sport 2001; 4 (1): 59-70 17. Mayhew JL, Johns RA, Ware JS, et al. Changes in absolute upper body power following resistance training in college males. J Appl Sport Sci Res 1992; 6 (3): 187 18. Baker D. Comparison of upper-body strength and power between professional and college-aged rugby league players. J Strength Cond Res 2001; 15 (1): 30-5 19. Izquierdo M, Ibanez J, Gorostiaga E, et al. Maximal strength and power characteristics in isometric and dynamic actions of the upper and lower extremitiesin middle aged and older men. Acta Physiol Scand 1999; 167: 57-68 20. Izquierdo M, Hakkinen K, Gonzalez-Badillo JJ, et al. Effects of long-term training specificity on maximal strength and power of the upper and lower extremities in athletes from different sports. Eur J Appl Physiol 2002; 87: 264-71 21. Newton R, Wilson G. The kinetics and kinematics of powerful upper body movements: the effect of load. In: Bouisset S, Metrai S, Monod H, editors. XIVth international series on biomechanics. Champaign (IL): Human Kinetics, 1993: 936-7 22. Bemben MG, Rohrs DM, Bemben DA, et al. Effect of resistance training on upper body strength, power and performance. J Appl Sport Sci Res 1991; 5 (3): 162-71 2005 Adis Data Information BV. All rights reserved. 233 23. Siegel JA, Gilders RM, Staron RS, et al. Human muscle power output during upper- and lower-body exercises. J Strength Cond Res 2002; 16 (2): 173-8 24. Baker D, Nance S, Moore M. The load that maximizes the average mechanical power output jump squats in power trained athletes. J Strength Cond Res 2001; 15 (1): 92-7 25. Sleivert GG, Taingahue M. The relationship between maximal jump-squat power and sprint acceleration in team sport athletes. Eur J Appl Physiol 2002; 87: 264-71 26. Weiss LW, Fry AC, Magu B, et al. Relative external loads eliciting maximum concentric force and power during noncountermovement squats. National Strength and Conditioning Association National Conference XXV; 2002, Las Vegas 27. Bourque S, Sleivert GG. Determinants of load at peak power during maximal effort squat jumps in endurance and power trained athletes [dissertation]. Fredericton: University of New Brunswick, 2003 28. Esliger DW, Sleivert GG. The neuromechanics of maximal effort squat jumps [dissertation]. Fredericton: University of New Brunswick, 2003 29. Stone MH, O’Bryant HS, McCoy L, et al. Power and maximum strength relationships during performance of dynamic and static weighted jumps. J Strength Cond Res 2003; 17 (1): 140-7 30. Thomas M, Fiatarone MA, Fielding RA. Leg power in young women: relationship to body composition, strength and function. Med Sci Sports Exerc 1996; 28 (10): 1321-6 31. Baker D. A series of studies on the training of high-intensity muscle power in rugby league football players. J Strength Cond Res 2001; 15 (2): 198-209 32. Newton RU, Kraemer WJ, Hakkinen K, et al. Kinematics, kinetics and muscle activation during explosive upper body movements. J Appl Biomech 1996; 12: 31-43 33. Hedrick A. Literature review: high speed resistance training. Nat Strength Cond Assoc J 1993; 15 (6): 22-30 34. Haff GG, Potteiger JA. A brief review: explosive exercise and sports performance. Strength Cond J 2001; 22 (3): 13-20 35. Newton R, Kraemer W. Developing explosive muscular power: implications for a mixed methods training strategy. Strength Cond J 1994; 6: 36-41 36. Sapega AA, Drillings G. The definition and assessment of muscular power. J Orthop Sports Phys Therapy 1983; 5 (1): 7-19 37. Young BW, Bilby EG. The effect of voluntary effort to influence speed of contraction on strength, muscular power, and hypertrophy development. J Strength Cond Res 1993; 7 (3): 172-8 38. Schmidtbleicher D, Buehrle M. Neuronal adaptation and increase of cross-sectional area studying different strength training methods. In: Jonsson B, editor. Biomechanics. Champaign (IL): Human Kinetics, 1987 39. Zatsiorsky VM. Science and practice of strength training. Champaign (IL): Human Kinetics, 1995 40. Cronin JB, McNair PJ, Marshall RN. Lunge performance and its determinants. J Sports Sci 2003; 21: 49-57 41. Mayhew JL, Bemben MG, Piper FC, et al. Assessing bench press power in college football players: the seated shot put. J Strength Cond Res 1993; 7 (2): 95-100 42. Mayhew J, Bemben M, Rohrs D, et al. Specificity among anaerobic power tests in college female athletes. J Strength Cond Res 1994; 8 (1): 43-7 Sports Med 2005; 35 (3) 234 43. Mayhew JL, Ware JS, Johns RA, et al. Changes in upper body power following heavy-resistance strength training in college men. J Sports Med 1997; 18: 516-20 44. Cronin J, Owen G. Upper body strength and power assessment in women using a chest pass. J Strength Cond Res 2004; 18 (3): 401-4 Cronin & Sleivert 61. Komi PV, Suominen H, Heikkinen E, et al. Effects of heavy resistance and explosive-type strength training methods on mechanical, functional, and metabolic aspects of performance. In: Komi PV, editor. Exercise and sport biology. Champaign (IL): Human Kinetics Publishers, 1982: 91-102 45. Baker D, Nance S. The relation between running speed and measures of strength and power in professional rugby league players. J Strength Cond Res 1999; 13 (3): 230-5 62. Chestnut JL, Docherty D. The effects of 4 and 10 repetition maximum weight-training protocols on neuromuscular adaptations in untrained men. J Strength Cond Res 1999; 13 (4): 353-9 46. Chelly SM, Denis C. Leg power and hopping stiffness: relationship with sprinting performance. Med Sci Exerc Sports 2001; 33 (2): 326-33 63. Hakkinen K. Neuromuscular and hormonal adaptations during strength and power training. J Sports Med Phys Fitness 1989; 29 (1): 9-26 47. Driss T, Vandewalle H, Monod H. Maximal power and forcevelocity relationship during cycling and cranking exercises in volleyball players. J Sports Med Phys Fitness 1998; 38: 286-93 64. Cronin JB, McNair PJ, Marshall RN. Velocity specificity, combination training and sport specific tasks. J Sci Med Sport 2001; 4 (2): 168-78 48. Kukolj M, Ropret R, Ugarkovic D, et al. Anthropometric, strength and power predictors of sprinting performance. J Sports Med Phys Fitness 1999; 39 (2): 120-2 49. Bosco C, Rusko H, Hirvonen J. The effect of extra-load conditioning on muscle performance in athletes. Med Sci Exerc Sports 1986; 18 (4): 415-9 50. Mayhew JL, Piper FC, Schwegler TM, et al. Contributions of speed, agility and body composition to anaerobic power measurement in college football players. J Appl Sport Sci Res 1989; 3 (4): 101-6 51. Meckel Y, Atterbom H, Grodjinovsky A, et al. Physiological characteristics of female 100 metre sprinters of different performance levels. J Sports Med Phys Fitness 1995; 35: 169-75 52. Nesser TW, Latin RW, Berg K, et al. Physiological determinants of 40-meter sprint performance in young male athletes. J Strength Cond Res 1996; 10 (4): 263-7 53. Young W, Hawken M, McDonald L. Relationship between speed, agility and strength qualities in Australian Rules football. Strength Cond Coach 1996; 4 (4): 3-6 65. Harris GR, Stone MH, O’Bryant HS, et al. Short-term performance effects of high power, high force, or combined weighttraining methods. J Strength Cond Res 2000; 14 (1): 14-20 66. McBride JM, Triplett-McBride T, Davie A, et al. The effect of heavy- vs light-load jump squats on the development of strength, power, and speed. J Strength Cond Res 2002; 16 (1): 75-82 67. Moss B, Refsnes PF, Abildgaard A, et al. Effects of maximal effort strength training with different loads on dynamic strength, cross-sectional area, load-power and load-velocity relationships. Eur J Appl Physiol 1997; 75: 193-9 68. Schmidtbleicher D, Haralambie G. Changes in contractile properties of muscle after strength training in man. Eur J Appl Physiol Occup Physiol 1981, 228 69. Wilson GJ, Newton RU, Murphy AJ, et al. The optimal training load for the development of dynamic athletic performance. Med Sci Sports Exerc 1993; 25 (11): 1279-86 54. Schmidtbleicher D. Training for power events. In: Komi PV, editor. Strength and power in sport. Boston (MA): Blackwell Scientific Publications, 1992: 381-95 70. Newton RU, Kraemer WJ, Hakkinen K. Effects of ballistic training on preseason preparation of elite volleyball players. Med Sci Sports Exerc 1999; 31 (2): 323-30 55. Wilson GJ, Lyttle AD, Ostrowski KJ, et al. Assessing dynamic performance: a comparison of rate of force development tests. J Strength Cond Res 1995; 9 (3): 176-81 71. Elliott BC, Wilson GJ, Kerr GK. A biochemical analysis of the sticking region in the bench press. Med Sci Sports Exerc 1989; 21 (4): 450-62 56. Young W, McLean B, Ardagna J. Relationship between strength qualities and sprinting performance. J Sports Med Phys Fitness 1995; 35 (1): 13-9 72. Ritzdorf W. Strength and power training in sport. In: Elliot B, editor. Training in sport. New York: John Wiley and Sons, 1998: 189-237 57. Moritani T. Time course of adaptations during strength and power training. In: Komi PV, editor. Strength and power in sport. Boston (MA): Blackwell Scientific Publications, 1992: 266-78 73. Sale D, MacDougall D. Specificity in strength training: a review for the coach and athlete. Can J Appl Sport Sci 1981; 6 (2): 87-92 58. Wilson GJ, Murphy AJ. The use of isometric tests of muscular function in athletic assessment. Sports Med 1996; 22 (1): 19-37 59. Hakkinen K, Komi PV, Alen M. Effect of explosive type strength training on isometric force- and relaxation-time, electromyographic and muscle fibre characteristics of leg extensor muscles. Acta Physiol Scand 1985; 125: 587-600 60. Lyttle AD, Wilson GJ, Ostrowski KJ. Enhancing performance: maximal power versus combined weights and plyometrics training. J Strength Cond Res 1996; 10 (3): 173-9 2005 Adis Data Information BV. All rights reserved. 74. Behm D, Sale D. Intended rather than actual movement velocity determines velocity-specific training response. J Appl Physiol 1993; 74 (1): 359-68 Correspondence and offprints: Assoc. Prof. John Cronin, New Zealand Institute of Sport and Recreation Research, Auckland University of Technology, Private Bag 92006, Auckland 1020, New Zealand. E-mail: [email protected] Sports Med 2005; 35 (3)
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