PHYSICAL DIFFERENCES BETWEEN FORWARDS AND
BACKS IN AMERICAN COLLEGIATE RUGBY PLAYERS
MICHAEL B. LA MONICA,1 DAVID H. FUKUDA,1 AMELIA A. MIRAMONTI,1 KYLE S. BEYER,1
MATTAN W. HOFFMAN,1 CARLEIGH H. BOONE,1 SATORU TANIGAWA,2 RAN WANG,1
DAVID D. CHURCH,1 JEFFREY R. STOUT,1 AND JAY R. HOFFMAN1
1
2
Institute of Exercise Physiology and Wellness, Sport and Exercise Science, University of Central Florida, Orlando, Florida; and
Faculty of Health and Sport Sciences, University of Tsukuba, Ibaraki, Japan
ABSTRACT
La Monica, MB, Fukuda, DH, Miramonti, AA, Beyer, KS,
Hoffman, MW, Boone, CH, Tanigawa, S, Wang, R, Church,
DD, Stout, JR, and Hoffman, JR. Physical differences between
forwards and backs in American collegiate rugby players. J
Strength Cond Res 30(9): 2382–2391, 2016—This study examined the anthropometric and physical performance differences
between forwards and backs in a championship-level American
male collegiate rugby team. Twenty-five male rugby athletes
(mean 6 SD; age 20.2 6 1.6 years) were assessed. Athletes
were grouped according to position as forwards (n = 13) and
backs (n = 12) and were evaluated on the basis of anthropometrics (height, weight, percent body fat [BF%]), cross-sectional
area (CSA), muscle thickness (MT), and pennation angle (PA) of
the vastus lateralis (VL), maximal strength (1 repetition maximum
[1RM] bench press and squat), vertical jump power, midthigh
pull (peak force [PF] and peak rate of force development
[PRFD]), maximal aerobic capacity (V_ O2peak), agility (pro agility,
T test), speed (40-m sprint), and a tethered sprint (peak velocity
[PV], time to peak velocity, distance covered, and step rate and
length). Comparisons between forwards and backs were analyzed using independent t-tests with Cohen’s d effect size. Forwards were significantly different from backs for body weight
(90.5 6 12.4 vs. 73.7 6 7.1 kg, p , 0.01; d = 1.60), BF%
(12.6 6 4.2 vs. 8.8 6 2.1%, p # 0.05; d = 1.10), VL CSA (38.3
6 9.1 vs. 28.7 6 4.7 cm3, p , 0.01; d = 1.26), 1RM bench
press (121.1 6 30.3 vs. 89.5 6 20.4 kg, p # 0.05; d = 1.17),
1RM squat (164.6 6 43.0 vs. 108.5 6 31.5 kg, p , 0.01; d =
1.42), PF (2,244.6 6 505.2 vs. 1,654.6 6 338.8 N, p ,
0.01; d = 1.32), PV (5.49 6 0.25 vs. 5.14 6 0.37 m$s21,
p # 0.05; d = 1.04), and step length (1.2 6 0.1 vs. 1.1 6
0.1 m, p # 0.05; d = 0.80). V_ O2peak was significantly (p #
0.05, d = 21.20) higher in backs (54.9 6 3.9 ml$kg$min21)
Address correspondence to David H. Fukuda, [email protected].
30(9)/2382–2391
Journal of Strength and Conditioning Research
Ó 2016 National Strength and Conditioning Association
2382
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than in forwards (49.4 6 4.4 ml$kg$min21). No differences in
agility performance were found between position groups. The
results of this study provide descriptive information on anthropometric and performance measures on American male collegiate
championship-level rugby players offering potential standards for
coaches to use when developing or recruiting players.
KEY WORDS athletic performance, anthropometrics, sports,
strength, speed, power
INTRODUCTION
R
ugby union (RU) is a contact sport requiring highintensity intermittent activity played over 80 minutes, consisting of two 40-minute halves (23,45).
Competitive RU is characterized by frequent
high-intensity bouts of sprinting, accelerations, scrummaging, line-outs, tackling, rucking, and mauling interspersed
with periods of lower-intensity aerobic activity (e.g., walking
and jogging) (41,45). In addition, critical physical characteristics such as lean body mass, low body fat, maximal strength
and power, aerobic capacity, agility, and in-match tactical
skills have been identified in European, African, and Oceanic
RU players (14,21,23,41).
During a rugby match, each team fields 15 players at
a time, which can be divided into 2 distinct positional groups
consisting of 8 forwards and 7 backs (23,41). Forwards are
responsible for regaining and maintaining possession of the
ball, which requires strength and power when driving forward with aggressive tackling in the scrum, ruck, and maul
(41). Forwards have been shown to spend more time in
rucks, mauls, and high-intensity static activities than backs
and have been categorized as the taller, heavier athletes
(16,41). In particular, forwards have been shown to spend
46.2% of their time “jogging” (10,21). When compared with
backs, forwards spend more time in lower speed zones (6–12
km$h21), endure a greater number of impacts (+60% than
backs) (15), participate in more tackles, tackle assists, and
rucks, all while carrying the ball into the opposition more
frequently during a game (33). Meanwhile, the backs obtain
possession of the ball from the forwards, accelerate from
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rucks, mauls, and scrums, evade opposing players, and carry
the ball down the field to create scoring opportunities (41).
Backs have been characterized as the shorter, lighter athletes
with greater demands placed on running (16,21,23). Regardless of position, the majority of moderate to intense accelerations during an elite RU game have been observed in
surges of 4–6 seconds while athletes perform at an overall
work-to-rest ratio of 1:5.7 (15). Specifically, backs have
shown to be quicker over shorter distances (4), cover greater
distances in a match because they cover a higher relative
percentage of their distance by sprinting (+35.4% than forwards), and are more ambulatory at low intensities during
a game (10). Hence, backs have been shown to possess
greater relative aerobic capacity (16,21,23). In fact, backs
have shown to enter high speeds (.20 km$h21) almost
twice as often as forwards (15). Despite notable differences
in speed between forwards and backs (4,51), additional variables, such as muscle architecture and running kinematics,
may help explain these discrepancies. Game analysis has
reported that RU athletes primarily perform between 80
and 95% HRmax with the largest relative portion spent
within 80–90% HRmax for backs (42.2% of the time during
a game) and within 90–95% HRmax for forwards (35.7% of
the time during a game) (15).
Rugby is one of the world’s most popular sports and the
fastest growing team sport in the United States (53). Rugby,
within American Universities, is considered an emerging
sport for women and is a National Collegiate Athletics Association (NCAA)-sponsored varsity sport for female athletes
(29). However, male collegiate athletes in the United States
play on university club teams without scholarships or NCAA
regulation (58). According to USA Rugby, over 300 American universities, with 128 in division I-AA, field club teams
with male athletes vying for national championship titles
across 3 divisions (58). Despite, the emergence of rugby at
the collegiate level, research in this area is lacking compared
with other sports (39). Relatively old data exist outside the
United States, in male (6,36,56,57) and female rugby players
(49). Recently, research has been conducted negatively correlating the relationship between explosive-isometric squat
force (r = 20.50) and jump height (r = 20.62) with sprint
performance (20 m) in collegiate male rugby players in the
United Kingdom (55). Nonetheless, additional and more current research in collegiate rugby athletes is warranted.
From a global perspective, it has been demonstrated that
anthropometrics, vertical jumping ability, agility, strength, and
speed momentum, but not speed times, develop across age
categories in RU players (4,18). In addition to maturation,
body mass, strength, and power may discriminate between
levels of competition (high school to professional ranks) in
which the larger, stronger, and more powerful athletes are
present at the higher levels in Oceanic nations (3). Alternatively, body fat percent was the only distinguishable indicator
between semiprofessional and amateur Portuguese RU players
(17). Within American RU, Maud (36) characterized a club
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team with traditional athletic performance tests (anthropometrics, skinfolds, V_ O2max on a treadmill, vertical jump, sit
and reach test, 1 repetition maximum [1RM] bench and leg
press, and anaerobic capacity), but failed to highlight speed
and agility tests. Maud and Schultz (37) investigated anthropometrics in US national RU players finding that the forwards
were the taller, heavier, had greater lean mass, and greater
body fat percent (BF%), whereas Carlson et al. (11) reported
somatotype differences in US national RU players finding that
forwards displayed endomesomorphic features, whereas
backs had more ectomorphic features. Despite morphological
distinctions among forwards and backs, muscle architecture
has not been explored in RU athletes and may offer a potential
explanation for differences in performance. In addition to the
aforementioned performance variables, forwards have shown
to have greater anaerobic power and capacity (37), whereas
backs have outperformed forwards in repeated jumps in place,
“clap” push-ups, and standing vertical jump (11).
To the best of our knowledge, research describing
anthropometrics and physiological performance characteristics on American male college rugby athletes is lacking.
Given the numerous demands of a RU athlete, components
of physical fitness are likely specific to the positional
demands during a match (51). Thus, the primary aim of
this study was to describe the physical characteristics of
a championship-level American male collegiate rugby
team. The secondary aim of this study was to examine
and characterize differences between forwards and backs
in American collegiate rugby with a comprehensive testing
protocol. Lastly, a tertiary aim was to physically benchmark collegiate level players against other rugby playing
nations with various standards of competition. It was
hypothesized that the forwards will be heavier, larger,
and stronger, whereas the backs will be lighter, quicker,
and more aerobically fit.
METHODS
Experimental Approach to the Problem
A cross-sectional study design was used to compare
forwards and backs in anthropometrics (height, body mass,
and BF%), endurance (V_ O2peak), muscle architecture
(cross-sectional area [CSA], muscle thickness [MT], and
pennation angle [PA]), strength and power (1RM bench
press and squat, countermovement jump [CMJ], and isometric midthigh pull [IMTP]), speed and agility (40 m, pro
agility, T test), and anaerobic sprint performance (tethered
sprint). Subjects completed all assessments on 5 nonconsecutive days over the course of the preseason. On a subject’s first day of testing, anthropometrics, body
composition, ultrasound, CMJ, IMTP, and a familiarization
trial of the tethered sprint were measured, with 10–15 minutes of rest between performance measures. Aerobic
capacity and strength testing (squat/bench press 1RM)
were completed on the second and third days of
testing, respectively. On the fourth day of testing, field
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Physical Differences between Forwards and Backs
(speed and agility) testing was completed with 10–15 minutes of recovery in between tests, and on the fifth day of
testing, the tethered sprint trial was conducted. This
approach allowed for a descriptive analysis and a comparison among forwards and backs.
Subjects
Twenty-five male collegiate rugby athletes with an age range
of 18 to 24 years (age: 20.2 6 1.6 years; height: 1.8 6 0.1 m;
mass: 82.4 6 13.2 kg) volunteered to participate in this study.
The study approved by the university institutional review
board as a retrospective analysis (IRB #: SBE-14-10579).
Testing was completed over the course of the preseason,
and volunteers were grouped by their position as either forwards (n = 13) or backs (n = 12), and had an average of 2.2 6
2.2 years of competitive rugby experience. However, not all
members of the rugby team were able to complete all measures. Members who were injured and were unable to complete
specific performance testing were still allowed to participate in
the tests they were physically capable of performing.
Procedures
Anthropometrics. Anthropometrics consisted of height,
weight (measured on a force plate [AccuPower; AMTI,
Watertown, MA, USA]) with shoes, and BF%. Body mass
was measured to the nearest 0.1 kg. Body composition was
assessed by skinfold analyses (Lange Skinfold Caliper;
Creative Health Products, Ann Arbor, MI, USA). Skinfolds
were taken at 3 sites (chest, abdominal, and thigh) (30) and
BF% was calculated using the Brozek equation (50). The
same researcher performed all skinfold assessments.
Aerobic Capacity. A continuous graded exercise test was
performed on a motorized treadmill (Desmo S; Woodway
USA, Inc., Waukesha, WI, USA) to determine maximal
oxygen consumption (V_ O2peak). Before testing, each participant was fitted with a heart rate monitor (Polar FS1; Polar
Electro, Inc., Lake Success, NY, USA) to record their heart
rate. Participants began with a warm-up at a self-selected
speed for 5 minutes. The initial speed, in the first stage,
was individualized and determined by their estimated 5k
pace. The first 3 stages were 2 minutes in length, whereas
subsequent stages were 1 minute. After the first stage, the
speed increased 1 mile per hour and then one half mile per
hour in the next 2 stages. During the subsequent stages, the
speed remained constant, whereas the incline increased 1%
every minute until the participant was unable to maintain the
speed or until volitional fatigue. Open-circuit spirometry
(TrueOne 2400; Parvo Medics, Inc., Sandy, UT, USA) was
used to estimate V_ O2peak (ml$kg21$min21). Participants
wore a mask (V2 Mask; Hans Rudolph, Inc., Shawnee, KS,
USA) that stabilized a 1-way valve (2700 Series Body Style
Saliva; Hans Rudolph, Inc.) around their mouth. Oxygen and
carbon dioxide was analyzed through a sampling line after
the gases passed through a heated pneumotach and mixing
chamber. Oxygen (O2), carbon dioxide (CO2), ventilation
2384
the
(V_ E), and respiratory exchange ratio were monitored continuously and expressed as 15-second averages with the highest
15-second average reported as V_ O2peak in L$min21. Previous work in our laboratory has shown the test-retest reliability for V_ O2peak to be intraclass correlation coefficient (ICC)
= 0.96, SEM = 1.4 ml$kg$min21 (46).
Muscle Architecture. During testing sessions, participants
underwent a noninvasive ultrasound examination of the
quadriceps musculature as described previously (7). Participants were asked to lay supine on an examination table with
both legs fully extended for a minimum of 15 minutes to
allow fluid shifts to occur. Afterward, participants were asked
to lay on their side with both knees and ankles stacked on
top of each other with a 108 bend in the knee. Images of the
vastus lateralis (VL), in the dominant leg, were captured on
the midline halfway between the greater trochanter and lateral epicondyle. The following measurements were obtained
from the images of the VL muscle: PA, MT, and CSA. All
measures were obtained by passing a 12-MHz linear probe
(General Electric LOGIQ P5; General Electric, Wauwatosa,
WI, USA) coated with water-soluble transmission gel (Aquasonic 100; Parker Laboratories, Inc., Fairfield, NJ, USA) over
the surface of the thigh at the predetermined anatomical
locations. Images of muscle CSA were captured using
extended field-of-view ultrasonography, whereas MT and
PA were captured using B mode ultrasonography. For all
images, gain was set at 50, dynamic range was set at 72 to
optimize spatial resolution, and depth was fixed at 5 cm4.
Further analyses of all ultrasound images were performed
using ImageJ (version 1.45s; National Institutes of Health,
Bethesda, MD, USA) to quantify CSA, PA, and MT. To
ensure consistency, the same investigator performed all
ultrasound measurements and analyses. Intraclass correlation coefficient and SEM were as follows: CSA (ICC =
0.96; SEM = 0.792 cm3), MT (ICC = 0.85; SEM = 0.080
cm), and PA (ICC = 0.93; SEM = 0.4418).
Strength Tests. Maximal strength testing was performed on
the squat and bench press using a barbell and a squat rack
(Power Rack, Power Lift; Conner Athletics Products, Inc.,
Jefferson, IA, USA). The 1RM tests were performed using
methods previously described by Hoffman (27) and Miller
(40). Before beginning the test, each participant completed
a general and specific warm-up. The general warm-up consisted of riding a cycle ergometer for 5 minutes at their preferred resistance. The specific warm-up consisted of 10 body
weight squats, 10 alternating lunges, 10 walking knee hugs,
and 10 walking butt kicks. Each participant performed 2
warm-up sets using a resistance that was approximately
40–60% for 5–10 repetitions and 60–80% for 3–5 repetitions
of their estimated maximum, respectively. The third set was
the first attempt at the participant’s 1RM. If the set was
successfully completed, then weight was added (5–10% for
squat and 2.5–5% for bench press) and another set was
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attempted. If the set was not successfully completed, then
the weight was reduced and another set was attempted. A
3- to 5-minute rest period was provided between each 1RM
attempt. This process of adding and removing weight was
continued until a 1RM was reached (within 5 maximal
attempts) (40). Attempts that did not meet the range of
motion criterion, as determined by the researcher, were
discarded. The bar placement for the bench press was a grip
slightly wider than the shoulder width, and the motion
criteria for the bar was to touch the chest without any
excessive arching of the back or bouncing of the weight.
The bar placement for the squat was selected by the participant with feet slightly wider than the shoulder width
and toes pointed slightly outward. The motion criteria for
the squat were to descend to where the thighs were parallel
with the floor and ascend until full knee and hip extension.
A researcher, located lateral to the participant, provided
a verbal signal “up” to ensure proper range of motion. All
1RM tests were completed and motion criteria was established under the supervision of Certified Strength and Conditioning Specialist.
Countermovement Jump and Isometric Midthigh Pull. Vertical
jump power was assessed on a force plate (AccuPower;
AMTI). Participants were instructed to perform 3 maximal
CMJ attempts with their hands placed on their hips to
eliminate the effect of an arm swing. All 3 jumps were
performed consecutively with 1 minute of rest between each.
The participants were asked to reset themselves after each
jump in the starting position and to proceed when ready.
Vertical jump peak power, in watts, was measured from the
best jump performance.
The maximal IMTP measured the rate of force development (RFD) and peak force (PF). The midthigh position
was determined for each participant before testing by
locating the knee and hip joints. The participants were
instructed to assume their preferred midthigh clean pull
position (26) with self-selected hip and knee angles. The
height of the barbell, inside a squat rack (Power Rack,
Power Lift; Conner Athletics Products, Inc.) was adjusted
up or down to make sure it was in contact with the midthigh. The participants were instructed to pull as hard and
as fast as possible and to continue the maximal effort until
they were told to relax. All participants were instructed to
relax before the command “GO!” to avoid precontraction.
Each trial lasted for 6 seconds with 3–5 minutes in between
trials. The force-time curve for each trial was recorded by
a force plate (AccuPower; AMTI) with a sample rate of
1,000 Hz. Each participant was allotted 3 maximal attempts. Peak force was determined as the highest force
value achieved during the 6-second isometric test subtracted by the participant’s body weight in Newtons. The
peak RFD was determined as the highest rate of change in
force measured across a 20-millisecond sampling window,
as recommended by Haff et al. (26). The sampling window
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started from the moment the force detected exceeded the
force generated by their body mass. Intraclass correlation
coefficient and SEM were as follows: CMJ (ICC = 0.99;
SEM = 196.55 W), PF (ICC = 0.95; SEM = 227 N), and
RFD (ICC = 0.90; SEM = 2,025 N$s21).
Speed and Agility Measures. All field tests were conducted
outdoor on an artificial turf field during 2 clear, dry days
(temperature: 25.5–27.28 C; relative humidity: 71–76%; wind:
0.89 m$s21).
40-m Sprint
Participants performed two 40-m sprints with 5 minutes of
rest between each sprint. All times were recorded with
a hand-held stopwatch (Robic SC-505W stopwatch;
Marshall-Browning International Corp., Hilton Head Island,
SC, USA) and started upon the participant’s first movement
(40). Each participant used a 2-point stance in an area
marked off by a cone and a line and sprinted through a second cone 40 m straight ahead. The faster of the 2 sprints was
recorded. The same researcher performed timed all sprints.
The test-retest reliability for the 40-m sprint ranges from
0.89 to 0.97 (40).
T Test
The T test (Figure 1) was performed as previously described
(40). Each participant sprinted in a straight line from
a 2-point stance (cone A) to a cone 9 m away (cone B).
The participant then side-shuffled to the left, without crossing the feet, to another cone 4.5 m away (cone C). After
touching the cone, the participant side-shuffled to the right
to a third cone 9 m away (cone D) before side-shuffling back
to the middle cone (cone B) and back-pedaling to the starting position (cone A). Participants performed 2 trials with
3 minutes between each trial. The fastest time was recorded.
The same researcher timed all T test measures and started
the timer on the participant’s first movement (40). The testretest reliability for the T test ranges from 0.93 to 0.98 (40).
Pro Agility
The protocol for the Pro Agility test (Figure 2) was followed
as previously described (40). Three lines, each separated by
5 m, were marked on the field. The participant straddled the
middle line (A) and sprinted to and touched 1 line (B; 4.5 m
away), then changed direction and sprinted to and touched
the far opposite line (C; 9 m away). The participant then
reversed direction and sprinted through the starting point
(A). All participants were instructed to sprint through the
finish line. Participants performed 2 trials in the same direction with 3 minutes of rest between each trial. The same
investigator timed all pro agility tests and started the timer
on the participant’s first movement (40). The test-retest reliability for the Pro Agility test is 0.91 (40).
Tethered Sprint
Participants performed a 1-minute maximal effort tethered
sprint on a nonmotorized treadmill (Force 3; Woodway
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Physical Differences between Forwards and Backs
SEM from our laboratory for
total distance are 0.77 and
4.94 m, respectively, and for
PV are 0.74 and 0.22 m$s21,
respectively.
Statistical Analyses
Figure 1. Schematic illustration of the T test.
USA, Inc.). Participants completed 1 familiarization trial
before the actual testing day. Participants began with
a warm-up at a self-selected speed for 5 minutes on
a motorized treadmill and were then instructed to
perform 3 submaximal tethered sprints on the nonmotorized treadmill for 4–6 seconds to conclude the warmup. After a 3- to 5-minute rest, participants were
instructed to accelerate and sprint as quickly as they
can for 1 minute and told to stop. Participants were instructed to sprint from a standing start before given the
command “GO!” to avoid a rolling start. Data recorded
from the tethered sprint included peak velocity (PV),
time to peak velocity (TTPV), and total distance. The
step rate and step length during the tethered sprint were
also calculated. Intraclass correlation coefficients and
All data were analyzed using
independent t-tests (forwards
vs. backs) using SPSS Statistics
v.21 (Chicago, IL, USA), and
significance was set at an alpha
level of 0.05, whereas p values of
less than 0.1 were considered
trends. Levene’s test was used
to examine normality, and for
any variable that displayed nonnormality, unequal variances
were assumed. Effect sizes are
reported as Cohen’s d with corresponding 90% confidence intervals and interpreted as trivial
(,0.2), small (0.2–0.6), moderate (0.6–1.2), and large (1.2–
2.0) (5,12). Effect size and
corresponding CIs were analyzed using a custom spreadsheet
(28). When confidence limits crossed both thresholds for substantially positive ($0.20) and negative (#20.20) effects,
differences were considered unclear.
RESULTS
Anthropometrics
The anthropometric characteristics for all participants are
listed in Table 1. Backs had significantly less body mass (p ,
0.001, large, d = 1.60), and significantly lower BF% (p = 0.010,
moderate, d = 1.10), than did forwards. A trend was observed
in height (p = 0.095), with a moderate effect size (d = 0.68)
indicating that forwards were possibly taller.
Muscle Architecture
Forwards had a significantly larger VL CSA (p = 0.004, large,
d = 1.26) compared with backs
(Table 1). There were no
between-group differences in
PA (p = 0.127, moderate, d =
0.61), but a trend was observed
in MT (p = 0.076), with a moderate effect size (d = 0.72), indicating possibly larger values for
forwards (Table 1).
Aerobic Capacity
Backs had significantly greater
V_ O2peak (p = 0.017, moderatelarge, d = 21.20) than forwards
(Table 2).
Figure 2. Schematic illustration of the Pro Agility.
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TABLE 1. Anthropometric and muscle architectural differences between positional groups.*†
Forwards
n
Height (m)
Body mass (kg)
Body fat (%)
CSA (cm3)
MT (cm)
PA (8)
13
13
12
13
13
13
Backs
Mean 6 SD
n
6
6
6
6
6
6
12
12
12
12
12
12
1.8
90.5
12.6
38.3
2.2
13.8
0.1
12.4
4.2
9.1
0.4
1.9
Mean 6 SD
p
6
6
6
6
6
6
0.095z
,0.001§
0.010§
0.004§
0.076z
0.127
1.8
73.7
8.8
28.8
1.9
12.5
0.1
7.1
2.1
7.3
0.4
2.3
Cohen’s d
0.68
1.60
1.10
1.26
0.72
0.61
(0.02 to 1.34)
(0.95 to 2.26)
(0.42 to 1.78)
(0.60 to 1.91)
(0.06 to 1.38)
(20.06 to 1.28)
*CSA = cross-sectional area; MT = muscle thickness; PA = pennation angle.
†Data are presented as mean 6 SD and Cohen’s d effect size (90% confidence interval).
zTrend (p , 0.1).
§Statistically significant (p # 0.05).
Strength Tests
Forwards had a significantly higher 1RM bench press
(p = 0.011, moderate, d = 1.17) than that of backs, but
no difference was noted in relative 1RM bench press (p =
0.341, unclear, d = 0.40) (Table 2). Forwards were
also significantly stronger in the 1RM squat (p = 0.003,
large, d = 1.42) than backs, but only a trend was
noted in the relative squat strength between the groups
(p = 0.060) with a moderate effect size (d = 0.85)
(Table 2).
Countermovement Jump and Isometric Midthigh Pull
Forwards had a significantly higher PF (p = 0.003, large, d =
1.32). No differences in VJ power (p = 0.108, moderate, d = 0.65)
TABLE 2. Performance differences between positional groups.*†
Forwards
n
V_ O2peak (ml$kg21$min21)
VJ power (W)
Strength
BP (kg)
BP:BM
Squat (kg)
Squat:BM
Midthigh pull
PF (N)
PRFD (N$s21)
Tethered sprint
Distance (m)
PV (m$s21)
TTPV (s)
Step length (m)
Step rate (steps/s)
Field tests
ProAgility (s)
T test (s)
40 m (s)
9
13
12
12
11
11
Mean 6 SD
Backs
n
49.4 6 4.7
9
4,676.8 6 1,036.2 12
121.1
1.3
164.6
1.8
6
6
6
6
30.3
0.3
43.0
0.4
10
10
10
10
Mean 6 SD
54.9 6 3.9
4,110.2 6 575.1
89.5
1.2
108.5
1.5
6
6
6
6
20.4
0.2
31.5
0.3
p
Cohen’s d
0.017z 21.20 (21.98 to 20.41)
0.108
0.65 (20.01 to 1.31)
0.011z
0.341
0.003z
0.060§
1.17
0.40
1.42
0.85
(0.48 to 1.87)
(20.30 to 1.10)
(0.70 to 2.14)
(0.12 to 1.57)
12 2,244.6 6 505.2
12 1,654.6 6 338.8
0.003z
1.32 (0.64 to 2.00)
12 14,952.6 6 8,864.5 12 15,086.7 6 18,014.4 0.982 20.01 (20.69 to 0.67)
6
6
6
6
6
6
6
6
6
6
13
13
13
13
13
226.3
5.49
5.74
1.2
3.26
14.1
0.25
1.76
0.1
0.15
12
12
12
12
12
213.8
5.14
6.33
1.1
3.40
17.9
0.37
2.70
0.1
0.20
11
11
11
5.14 6 0.30
10.96 6 0.64
5.57 6 0.38
11
11
11
5.16 6 0.30
10.61 6 0.41
5.47 6 0.14
0.063§
0.75 (0.08 to 1.42)
0.012z
1.04 (0.37 to 1.71)
0.515 20.24 (20.92 to 0.42)
0.047z
0.80 (0.14 to 1.47)
0.058§ 20.77 (21.44 to 20.10)
0.880
0.143
0.470
20.06 (20.77 to 0.65)
0.62 (20.09 to 1.33)
0.30 (20.42 to 1.01)
_ O2peak = peak oxygen uptake; VJ = vertical jump; BP = bench press; BM = body mass; PF = peak force; PRFD = peak rate of
*V
force development; PV = peak velocity; TTPV = time to peak velocity.
†Data are presented as mean 6 SD and Cohen’s d effect size (90% confidence interval).
zStatistically significant (p # 0.05).
§Trend (p , 0.1).
VOLUME 30 | NUMBER 9 | SEPTEMBER 2016 |
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Physical Differences between Forwards and Backs
or PRFD (p = 0.982, unclear, d = 20.01) were observed between
the groups (Table 2).
Speed and Agility Measures
No differences (p = 0.470, unclear, d = 0.30) were observed
in 40-m sprint between the groups. Additionally, there were
no differences observed between the groups in the pro agility
(p = 0.880, unclear, d = 20.06) or T test (p = 0.143). However, a moderate effect in the T test (d = 0.62) suggests that
backs were possibly faster than forwards (Table 2).
Tethered Sprint
Forwards were observed to have a significantly higher PV
(p = 0.012, moderate, d = 1.041), and greater step length (p =
0.047, moderate, d = 0.80) than those of backs. No differences were noted between the groups in TTPV (p = 0.515,
unclear, d = 20.25), but trends were noted in distance covered (p = 0.063), with a moderate effect size (d = 0.75), and
step rate (p = 0.058), with a moderate effect size (d = 20.77),
which suggests that forwards possibly covered a greater distance than backs and backs possibly had a quicker step rate
than that of forwards (Table 2).
DISCUSSION
Limited research is available on collegiate RU characteristics. Hence, the purpose of the current investigation was to
characterize the anthropometric and performance measures
between forwards and backs in an American male collegiate
rugby team using a comprehensive testing battery. As
hypothesized, our findings are consistent with previous
studies describing forwards as having greater body mass
and body fat, exhibiting greater absolute strength and PF
when compared with smaller leaner backs that display
a greater propensity for aerobic power (8,16,23,32,41). This
study adds to the current body of rugby literature by providing data from muscle architecture, running kinematics,
and speed and agility assessments to allow further differentiation between forwards and backs. The current results suggest that forwards had a greater VL CSA, and possibly MT,
than did backs. Forwards were moderately taller and had
a longer step length, which may account for the moderately
greater distance covered by the forwards as compared with
the backs. However, forwards and backs did not show any
differences in speed and agility tests.
In regard to body mass and BF%, forwards were shown to
be heavier and have a greater amount of body fat. According
to previous research, forwards tend to weigh more and have
greater amounts of body fat than backs (8,23,32,52). Similarly, in RU and rugby league athletes, greater body mass in
forwards and leaner backs have been reported (16,24,32,52).
The greater body mass in forwards may provide a protective
advantage because they tend to have a greater degree of
contacts per training session and a greater involvement in
rucks, mauls, and scrums per match (8,21,33). However,
backs take advantage of being lighter and leaner to increase
their speed and advance the ball forward (23). In the current
2388
the
investigation, a moderate effect for height may indicate that
the forwards were taller than backs. Although the literature
on height seems unclear, generally, the higher the playing
level, the clearer the distinction between forwards and backs
(23). Therefore, longer limbs and being physically taller may
be advantageous for forwards who spend more time in lineouts (23,47).
Backs had a significantly greater aerobic capacity than
forwards. This is also consistent with available literature in
rugby players (16,21,23,41). The aerobic capacity of professional Portuguese RU players were previously reported to be
46.6 ml$kg21$min21 in forwards and 52.3 ml$kg21$min21 in
backs (16), whereas Japanese rugby college athletes, regardless of position, were reported to have an average aerobic
capacity of 54.8 ml$kg21$min21, which was similar to the
current investigation. Backs have a greater need for aerobic
capacity as they have been shown to travel greater absolute
and relative distances during a match and spend more time
in high-intensity running than forwards (10,21,45). In addition, Roberts et al. (45) showed that backs spend more time
in low-intensity activity as compared with forwards (96 vs.
88%, respectively). Because backs cover longer distances,
and spend greater time in low-intensity activity and highintensity running, the need for or the development of higher
aerobic capacities should be expected.
Strength and power are of great importance to forwards
(23). In support, the forwards examined in this study had
significantly greater CSA and possibly MT of the VL suggesting a difference between forwards and backs. A greater
CSA is indicative of greater force production potential (1,38),
and therefore, may provide an advantage for greater force
outputs that appear to parallel the observed strength differences in the current investigation. In conjunction, match play
may be indicative of greater force production in forwards.
For example, Roberts et al. (45) observed that forwards perform more bouts (89 vs. 24) and spend a longer average time
(5.2 vs. 3.6 seconds) in rucks, mauls, line-outs, tackles, and
scrums than backs.
The results of this study indicated that forwards were
significantly stronger in the bench press and squat measures.
However, when equating for body mass, these differences
were no longer apparent. In comparison with Australian RU
athletes, the relative strength results from this study indicate
that forwards were similar to the international and senior
levels of competition for the bench and squat, respectively,
whereas the backs were more consistent with the senior and
intermediate levels, respectively (54). Particularly, the relative strength observed in professional Australian RU players
for bench press (1.3–1.4) and squat (1.6–1.7) fall in line with
the current findings (2). In agreement with previous
research, forwards were shown to be stronger than backs
(8,52). This is likely related to the greater contact (e.g., rucking, mauling, and scrummaging) observed in forwards during
competition than backs (21,23,45). However, comparison
with other studies indicates that this sample of American
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college rugby athletes was weaker than professional rugby
players (2,8,59), but similar in strength to semiprofessionals
(31). These differences may occur because of training history
and structured resistance training programs used by national
or international competitors (23,52).
Although no differences in power were noted between
positions, a moderate effect size suggests that forwards
were potentially more powerful than backs. This was
similar to other studies that reported similar vertical jump
height between forwards and backs in the US national
rugby team (37) and an American club team (36). Power
seems to be greater as the level of competition increases in
RU players because of training and physical maturation
(3). The greater power in the forwards may stem from
the observed larger CSA and greater 1RM strength as well
as possibly greater MT and relative squat strength compared with backs. Likewise, no differences between backs
and forwards were observed in peak RFD, but forwards
were shown to produce greater absolute PF during the
IMTP than backs. Peak force outputs reported in this
study appear to be less than that reported in English rugby
union academy players under 21 years (3,104.5 6 354.0 N),
under 18 years (2,561.3 6 339.4 N) (18), professional rugby
league players (2,529.4 6 397.8 N) (60), and professional
rugby union players from the United Kingdom (2,634.1 6
371.9 N) (13). Because of rugby’s combative nature and use
of explosive movements, power is an important physical
quality for both forwards and backs while noting that the
forwards spend most of the time in close contact with the
opposition.
The results of this study were unable to report any
significant difference in speed or agility between backs and
forwards. This is in contrast to previous studies that
reported that backs had quicker acceleration and maximal
speed over 40 m, whereas forwards were slower, but had
greater sprint momentum because of a larger body mass
(4,51). These differences may be related to the different
responsibilities for each position during competition. During a match, forwards are involved primarily in static activity (rucks, scrums, mauls, tackling), whereas backs are
involved with maximal intensity longer duration runs
(21,32,45). Backs tend to rely on their speed, generally
have a greater space on the field to achieve higher speeds
than forwards, and have shown to produce similar short
sprint (35 m) performance as sprinters (22,44). Speed performance for the 40-m sprint in this study was similar to
elite Portuguese rugby athletes (;5.5 seconds) (59) and
Australian super rugby players (forwards: 5.46–5.86 seconds and backs: 5.22–5.35 seconds) (54).
This seems to be the first study to report pro agility
performance measures in RU players between forwards and
backs. However, no differences in pro agility performance
were observed between positions, and a trivial effect makes
the conclusions unclear. The current investigation resulted in
slower times (5.14 and 5.16 seconds), on average, than
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national level junior (American) football players in Australia
(4.85 seconds) (34) and preseason status NCAA division III
soccer players (4.96 seconds) (35). Alternatively, a moderate
effect in T test performance suggests that the backs were
possibly quicker than the forwards. The observed T test
times in this study appear to be comparable with those previously reported in South African university rugby league
players (10.0–11.7 seconds) (43), but slower times than
U17 Brazilian soccer players (10.10 seconds) (20), Turkish
collegiate soccer players (9.68–9.94 seconds) (25), and
American collegiate basketball and baseball players (9.89
seconds) (42). The lack of differences between positions in
speed and agility could be attributed to the use of hand-held
stopwatches, rather than more precise timing systems, or
a reflection of the sampled athletes with respect to training
status and competition level.
There were significant differences in the PV and step
length over the course of a 1-minute tethered sprint with
forwards displaying a higher velocity and longer step
length than backs. Despite no significant differences were
noted in the distance covered over 1 minute, a moderate
effect suggests that forwards possibly covered a greater
distance. The reason for this discrepancy could be due to
the difference in running kinematics on a tethered treadmill vs. land-based running because we did not see any
differences in 40-m times on the field (19,48). Along with
differences in kinematics, the stride length may have
a moderate influence over maximum running velocity
and has been shown to have a high correlation (r = 0.66)
with maximum running velocity over 9 seconds of sprinting (9). Although the sprint duration in this study was
1 minute, the average time to PV for both positional groups
was less than 9 seconds. In conjunction with a greater step
length, forwards appear more powerful under anaerobic
performances over the course of 7–40 seconds (23), which
may have been enough to overcome the possibly quicker
step rate of the backs to achieve a higher PV and possibly
greater distance covered.
In addition to this study being limited to a sample drawn
from a single American collegiate rugby team, the researchers were unable to test all athletes because of time
constraints and injuries. Furthermore, the inclusion of match
analysis from several competitive matches to compare with
the resulting anthropometric and performance measures
would have strengthened the comparisons. Nonetheless,
the results of this study indicate that American university
forwards and backs were similar to European, New Zealand,
and Japanese rugby athletes. The forwards were the larger
and stronger athletes, whereas backs were lighter and more
aerobically conditioned athletes. This study provides an
initial descriptive examination of American male collegiate
rugby athletes and a comprehensive test battery, with novel
assessments (muscle architecture, Pro Agility, and tethered
sprint), that further characterizes and distinguishes between
forwards and backs.
VOLUME 30 | NUMBER 9 | SEPTEMBER 2016 |
2389
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Physical Differences between Forwards and Backs
PRACTICAL APPLICATIONS
The results of this study provide a descriptive analysis of
a sample of championship-level American college rugby
players, thereby providing data for comparisons among
other nations at various competitive levels. Considering the
growing popularity of rugby in college athletes, the ability
to understand the physical attribute of players will assist
coaches in team selection and the development of appropriate training programs to meet the physiological demands of rugby that are specific to each position. For
instance, the bigger stronger athletes may be more suitable
in a forward position (prop, hooker, lock, flanker, or
number 8), whereas a smaller, lighter, quicker, and more
aerobically inclined athlete may be more appropriate in
a back position (half-backs, wingers, fullback, or centers). In
terms of strength and conditioning programs, forwards
should focus on optimizing size for protection, strength,
and power, and backs should focus on quickness, power,
and aerobic conditioning. Coaches may further examine
whether differences among other nations or competitive
levels are due to physical attributes or knowledge and
understanding of rugby. Future studies on the relationship
between laboratory- and field-based performance measures
and actual game performance measures in American
collegiate rugby athletes are warranted.
ACKNOWLEDGMENTS
The authors thank the group of participants for their
dedication and the staff of the Institute of Exercise Physiology and Wellness for their help with data collection and
analysis.
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