EFFECT OF CAFFEINE AS AN ERGOGENIC AID DURING
ANAEROBIC EXERCISE PERFORMANCE IN CAFFEINE
NAÏVE COLLEGIATE FOOTBALL PLAYERS
KATHLEEN WOOLF,1 WENDY K. BIDWELL,1
AND
AMANDA G. CARLSON2
1
Nutrition Program, Arizona State University, Polytechnic Campus, Mesa, Arizona; and 2Athletes Performance,
650 S. Athletes’ Performance, Tempe, Arizona
ABSTRACT
Woolf, K, Wendy, KB, and Carlson, AG. Effect of Caffeine as
an Ergogenic Aid During Anaerobic Exercise Performance in
Caffeine Naı̈ve Collegiate Football Players. J Strength Cond Res
23(5): 1363–1369, 2009—Research suggests that caffeine
may improve performance in aerobic exercise; the evidence for
anaerobic performance is mixed. This study examined the effect
of caffeine (5 mg/kg body weight [BW]) vs. placebo on
performance-based anaerobic exercise tests used during the
National Football League (NFL) Combine. Collegiate football
athletes (n = 17; 20 6 2 yr; body mass index 29.4 6 3.6 kg/m2)
completed 2 study visits, 1 week apart. Participants were low
caffeine users with a reported average intake of 16 6 20 mg/day.
On the day of testing, participants ingested a caffeinated (5 mg/
kg BW caffeine + 0.125 g/kg BW carbohydrate) or placebo
(0.125 g/kg BW carbohydrate) beverage, ate a light meal, and
completed 3 exercise tests (40-yard dash, 20-yard shuttle, and
a bench press) 60 minutes later. Borg’s rating of perceived
exertion (RPE) was recorded after each exercise test. Heart rate
(HR) and blood pressure (BP) were monitored (pre-exercise and
postexercise). Data were analyzed using paired t-tests, Wilcoxon
signed rank test, and repeated measures analysis of variance.
No significant differences were found between treatments for
the exercise tests (40-yard dash: 5.01 6 0.25 vs. 5.03 6 0.26 s,
p = 0.43; 20-yard shuttle: 4.64 6 0.19 vs. 4.66 6 0.24 s,
p = 0.51; bench press: 17 6 8 vs. 17 6 8 reps, p = 0.51;
caffeine vs. placebo, respectively). However, 59% of the participants improved in performance with the caffeine during the
bench press and the 40-yard dash. No differences were found
between treatments for RPE, HR, and BP. Caffeine did not
improve performance for anaerobic exercise tests used at the
NFL Combine in caffeine naı̈ve male football athletes.
Address correspondence to Dr. Kathleen Woolf, kathleen.woolf@asu.
edu.
23(5)/1363–1369
Journal of Strength and Conditioning Research
Ó 2009 National Strength and Conditioning Association
KEY WORDS field tests, bench press, 40-yard dash, 20-yard
shuttle
INTRODUCTION
M
any athletes use caffeine as an ergogenic aid to
enhance exercise performance (13,17,29–30).
A variety of foods and beverages, including
chocolate, tea, coffee, and cola drinks, contain
caffeine. Energy drinks are a relatively new category of
beverages that contain caffeine in amounts similar to the
concentrations found in coffee (33).
Caffeine is currently a monitored or restricted drug for
competitive athletes. The World Anti-Doping Agency
(WADA) monitors caffeine use during competition to detect
patterns of misuse in sport (42). The National Collegiate
Athletic Association (NCAA) considers caffeine a prohibited
substance when the concentration in the urine exceeds 15
mg/mL (44). An athlete would need to consume approximately
13 mg mg/kg body weight (BW) of caffeine (approximately
700 mg caffeine or 8 cups of brewed coffee) to reach the
maximum allowable urinary concentrations (17,21).
Evidence from the research literature suggests that 150 to
250 mg of ingested caffeine improves exercise performance
(2,9). Caffeine may enhance performance during endurance
exercise, particularly prolonged and exhaustive exercises
(1,5,7,10,18,20,22). Caffeine may also reduce fatigue, improve
concentration, and enhance mental alertness (31,41). However, the evidence for caffeine as an ergogenic aid for shortterm, high-intensity athletic performance is more mixed. For
example, some studies report an improvement in anaerobic
exercise performance with caffeine (14,16,25,42). Other
studies have reported no improvement in anaerobic exercise
performance with caffeine (11,23,26).
Mixed results could be due to the different exercise
protocols, doses of caffeine, and the fitness level of the
research participants. Caffeine may affect trained and nontrained participants differently; trained individuals may
benefit more from the ergogenic effect of caffeine. Elite
athletes generally have more muscle mass than recreational
athletes. Researchers have speculated that caffeine acts
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Caffeine as Ergogenic Aid in Football Players
directly on muscle fibers, and, thus, the effects of caffeine
would be greater in individuals with a larger muscle mass.
Historic use of caffeine could also impact study results.
No improvement in 15-second cycling sprints was observed
in untrained males that were low caffeine users (,70 mg/d)
after ingesting 7 mg/kg BW of caffeine (43). A higher dose
of caffeine (7 mg/kg BW) given to low caffeine users may
produce a shaky or sick feeling and possibly decrease
performance.
Recently, the impact of caffeine during high-intensity team
sports activity has been examined. Players of high-intensity
team sports engage in many short-term, high-intensity
exercise bouts throughout the game. Stuart et al. (40)
examined the effects of caffeine (6 mg/kg BW) on highintensity team-sport performance. The participants were
amateur male rugby players and were all regular caffeine
consumers. The exercise tests included 14 circuit stations
of activities examining sprinting abilities (straight-line and
agility sprints), peak-power generation in 2 consecutive
drives, and accuracy. Performance improved in the caffeine
trial compared with the placebo trial for all exercise tests
except peak-power during the second drive. This study
suggests that caffeine (6 mg/kg BW) may be effective at
improving physical and skill performance in trained male
rugby players who are regular users of caffeine.
Only limited research has examined the impact of caffeine
on anaerobic-type exercise during field-type exercise. Furthermore, studies do not always report the historic use of
caffeine of the research participants. Thus, the purpose of this
study was to examine the effect of caffeine on short-term,
high-intensity exercise in highly trained, caffeine naı̈ve
football athletes using anaerobic field-type exercises such as
those used in the National Football League (NFL) Combine.
were also recruited from Athletes’ Performance, a state-ofthe-art facility that trains elite and professional athletes.
Participants were eligible if they fit the following inclusion
criteria: played collegiate football during the past season. This
study was approved by the Human Subjects Institutional
Review Board at Arizona State University, and the procedures
were conducted in accordance to these guidelines.
Seventeen male collegiate football players (age, 20 6 2 yr;
wt, 100 6 15 kg; ht, 185 6 5 cm; body mass index [BMI],
29.4 6 3.6 kg/m2) completed this study (Table 1). Height was
measured (without shoes) to the nearest 0.1 cm using a
stadiometer. Weight was measured to the nearest 0.1 kg using
a digital platform scale (Avadia model 758, Webb City, MO).
The athletes played collegiate football during the previous
season (community college to NCAA Division I). Some of the
research participants were currently training for the NFL
Combine; other participants were completing off-season
training to prepare them for the next football season. To
further control the testing conditions, participants completed
identical training programs during the 2 weeks of testing.
To assess usual intake of caffeine, participants completed
the Arizona Food Frequency Questionnaire (AFFQ) (University of Arizona, Tucson, AZ) (34). Participants were given
written and oral instructions on how to complete the
questionnaire. The AFFQs were analyzed by the NCS
OpScan 5 (Al-Bassam International Company, Al-Khobar,
Saudi Arabia). Typical dietary caffeine intake was 16 6 20
(range, 0–81) mg/day (Table 1). Sixteen participants
consumed less than 50 mg/day, and 1 participant consumed
greater than 50 mg/day (Table 1).
Procedures
Participants reported to Athletes’ Performance twice, separated by 1 week, after an 8- to 12-hour fast and abstaining from
METHODS
Experimental Approach to the Problem
The primary purpose of this study was to examine the effects
of a moderate dose of caffeine during field-type exercises in
highly trained collegiate male football players. A randomized,
double-blind crossover study examined the impact of
a moderate dose of caffeine (5 mg/kg BW) on anaerobic
performance in male football players, 18 to 23 years of age.
Our primary null hypothesis was that the ingestion of
a beverage with a 5.0 mg/kg BW dose of caffeine would not
significantly improve exercise performance in collegiate male
football players using the 185 or 225 lb bench press, a 40-yard
dash, and a 20-yard shuttle. Our secondary null hypothesis
was that the ingestion of a beverage with 5.0 mg/kg BW dose
of caffeine would not alter heart rate (HR), blood pressure
(BP), or Borg’s rating of perceived exertion (RPE).
Subjects
Recruitment began in November of 2004 and involved both
oral communication as well as a recruitment flyer distributed
to local community colleges and athletic facilities. Athletes
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TABLE 1. Characteristics of study participants
(n = 17).*†
Variable
Age (yr)
20 6 2
Height (cm)
185 6 5
Weight (kg)
100 6 15
29.4 6 3.6
BMI (kg/m2)
Typical dietary caffeine intake (mg/d)‡ 16 6 20
Caffeine , 50 mg/d (n)
16
Caffeine . 50 mg/d (n)
1
Treatment beverage
Caffeine dose (mg/kg BW)
5
Carbohydrate dose (g/kg BW)
0.125
*BMI = body mass index; BW = body weight.
†Values are mean 6 SD.
‡Data obtained from Arizona Food Frequency
Questionnaire.
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caffeinated products for 48
hours. HR and BP were measured upon arrival to the facility. A Polar heart rate monitor
(Polar T1 model CEO 537,
Lake Success, NY) was used
to monitor HR, and a professional stethoscope (Adscope
series 601, Miami, FL) and
sphygmomanometer (Moore
Medical, New Britain, CT)
were used to monitor BP. The
participants then consumed
a beverage with caffeine (caffeine, 5.0 mg/kg BW; carbohydrate (CHO), 0.125 g/kg BW)
or without caffeine (placebo;
CHO, 0.125 g/kg BW) and ate
a meal 15 minutes later (Table 1).
Each participant consumed the
same meal during each of the
Figure 1. Exercise performance during caffeine and placebo treatments during the 40-yard dash. Note: outliers are
test days. Sixty minutes after
identified as circles with the ID number and are defined as points more than 1.5 box-lengths from the edge of the box.
consuming the beverage, participants performed 3 exercise
tests: a 40-yard dash test,
an Olympic bar. While in a supine position on the bench,
20-yard shuttle, and a bench press (Olympic bar) with
participants lifted the Olympic bar (185 or 225 lb) off the rack
repetitions to fatigue using 185 or 225 lb. The lower
then lowered it to the chest. The bar was then pressed back up
weight (185 lb) was used for the participants who could not
to the starting position and repeated to fatigue. Researchers
press 225 lb.
recorded the number of repetitions for each participant. The
The 40-yard dash assesses speed, power, and explosion.
research participants estimated perceived effort immediately
During this exercise test, the research participants ran at
maximal effort for 40 yards on
an AstroTurf track. The 20yard shuttle measures lateral
speed and coordination. It was
also completed on the AstroTurf. The AstroTurf was premarked at 0, 5, and 10 yards.
The participants started at the
center of the premeasured 10
yards and ran at maximum
effort for 5 yards one direction,
touching the yard line. They
then ran the full 10 yards back
the other direction. After
touching the yard line, the
participants finished the test
after running across the center
line. The researchers recorded
the time it took to complete the
40-yard dash and the 20-yard
shuttle. Participants completed
the bench press, which tests
upper body strength and conFigure 2. Exercise performance during caffeine and placebo treatments during the 20-yard shuttle.
ditioning, on a flat bench using
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Caffeine as Ergogenic Aid in Football Players
thought they received or how
they felt after each treatment. In
addition, plasma or urinary
caffeine concentrations were
not measured.
Statistical Analyses
Descriptive statistics (age,
height, weight, BMI) were expressed as mean 6 SD. Normality of data was assessed
using histograms and the
Kolmogorov-Smirnov test statistic. Tests for normality were
met for the 40-yard dash, 20yard shuttle, RPE, and HR.
Before analysis, the bench press
data were transformed using the
logarithm. Mean and SD values
in the tables are the untransformed values. Paired t-tests
Figure 3. Exercise performance during caffeine and placebo treatments during the bench press. Note: outliers are
using the Statistical Package
identified as circles with the ID number and are defined as points more than 1.5 box-lengths from the edge of the
box. Extreme points (indicated with an asterisk) extend more than 3 box-lengths from the edge of the box.
for Social Sciences (SPSS, version 14.0, 2005, Chicago, IL)
determined the independent
after each exercise test using Borg’s RPE (scale 6–20).
effects of caffeine vs. no caffeine on exercise performance
Postexercise HR and BP were measured immediately after the
during the bench press, 40-yard dash, and 20-yard shuttle. A
final exercise test.
2-way repeated-measures analysis of variation + Bonferroni
post hoc test was used to examine significant differences in
Limitations
HR and systolic (S)BP for time, treatment, and their interAlthough we controlled for caffeine and diet, we were not
action. A Wilcoxon signed rank test was used to test for
able to ensure compliance in the study. Factors such as rest,
differences for the diastolic (D)BP data.
prior exercise, and over-the-counter medications may have
RESULTS
affected the participants’ response or metabolism of the
caffeine. We did not ask the participants which treatment they
This study examined the effects of a moderate dose of caffeine
(5 mg/kg BW) on anaerobic exercise performance (40-yard
TABLE 2. Exercise performance during caffeine and
placebo treatments for study participants (n = 17).*†
Variable
Caffeine
Placebo
p
40-yard
5.01 6 0.25 5.03 6 0.26 0.43
dash (s)
20-yard
4.64 6 0.19 4.66 6 0.24 0.51
shuttle (s)
Bench press‡
17 6 8
17 6 8
0.51
(reps)
*s = seconds; reps = repetitions.
†Data were analyzed using paired t-tests; values are
mean 6 SD.
‡Data transformed using the logarithm (log10) before
statistical analysis; mean 6 SD data presented
untransformed.
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TABLE 3. Borg’s rating of perceived exertion (RPE)
after exercise tests during caffeine and placebo
treatments for study participants (n = 17).*
RPE†
§
40-yard dash
20-yard shuttlel§
Bench press‡
Caffeine
Placebo
p-Value
13 6 3
12 6 2
16 6 2
13 6 2
12 6 3
15 6 3
1.00
0.25
0.31
*Data were analyzed using paired t-tests; values are
mean 6 SD.
†6 to 20 scale.
‡n = 17.
§n = 14.
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and BP were observed between
treatments at the pre-exercise
or postexercise assessments.
TABLE 4. Blood pressure and heart rate pre- and postcaffeine and placebo
treatments for study participants (n = 17).*†
Caffeine
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DISCUSSION
Placebo
This study examined the effects
of a moderate dose of caffeine
(5 mg/kg BW) on exercise
SBP (mm Hg)
114 6 10
136 6 14
116 6 12
135 6 14
performance, RPE, HR, and
DBP (mm Hg)
72 6 8
63 6 6
76 6 6
63 6 9
BP in highly trained male
HR (BPM)
68 6 10
118 6 21
67 6 6
110 6 19
collegiate football athletes. In
*SBP = systolic blood pressure; DBP = diastolic blood pressure; HR = heart rate; BPM =
our study, all of the participants
beats per minute.
consumed less than the U.S.
†SBP and HR data analyzed using repeated measures analysis of variance; DBP data
analyzed using Wilcoxon signed rank test. Significant difference between pre and post exercise
population’s average intake of
(time effect, p , 0.01). No significant differences observed for treatment or the interaction
caffeine of 193 mg/d (19).
(treatment and time).
Thus, the participants in our
study were caffeine naı̈ve or
very low caffeine consumers.
To date, only limited studies
have examined the impact of caffeine on field-based
dash, 20-yard shuttle, and bench press), RPE, HR, and BP in
anaerobic exercise performance (32,37,39,40).
collegiate male football players.
We did not find a statistically significant difference between
Exercise Performance
treatments for the bench press. However, 59% of the
No significant differences in performance were seen for the
participants in our study increased the number of repetitions
40-yard dash, 20-yard shuttle, or bench press between
on the bench press with caffeine.
treatments (40-yard dash: caffeine, 5.01 6 0.25 vs. placebo,
Jacobs et al. (26) also examined the impact of caffeine
5.03 6 0.26 s, p = 0.43; 20-yard shuttle: caffeine, 4.63 6 0.19
on exercise performance during the leg press and bench
vs. placebo, 4.66 6 0.24 s, p = 0.51; bench press: caffeine,
press. Similar to our study, no significant differences were
17 6 8 vs. placebo, 17 6 8 rep, p = 0.51) (Figures 1–3)
observed with the caffeine trial compared with the placebo
(Table 2). However, 59% of the participants decreased time
trial. Jacobs et.al. (26) included recreational athletes
during the 40-yard dash, 59% decreased time during the
instead of the highly trained collegiate football players
20-yard shuttle, and 47% increased repetitions during the
used in our study. Jacobs et al. (26) administered a lower
bench press with the caffeine.
dose (4 mg/kg BW) of caffeine 90 minutes before testing
instead of the 5 mg/kg BW dose 60 minutes before testing
Borg’s Rating of Perceived Exertion
in our study. However, their study did not provide any
Because the RPE data were not normally distributed, the
information on the historic use of caffeine by the research
Wilcoxon signed rank test was used for the analysis. No
participants.
differences were observed for RPE between treatments in any
In an older study, Jacobson et al. (27) found an
of the exercises (40-yard dash: caffeine, 13 6 3 vs. placebo,
improvement
in muscle strength and power using knee
13 6 2, p = 1.00; 20-yard shuttle: caffeine, 12 6 2 vs. placebo,
extension
and
flexion exercises. Similar to our study, the
12 6 3, p = 0.25; bench press: caffeine, 16 6 2 vs. placebo, 15 6
research
participants
were elite male football athletes and low
3, p = 0.31) (Table 3).
users of caffeine. However, a higher dose of caffeine (7 mg/kg
Heart Rate and Blood Pressure
BW) was used in that study compared with our study
Postexercise values for HR were significantly higher than pre(5 mg/kg BW). These results suggest that a higher dose of
exercise values within each treatment (precaffeine, 68 6 10 vs.
caffeine (7 mg/kg BW) may be needed to get an ergogenic
postcaffeine, 118 6 21; preplacebo, 67 6 6 vs. postplacebo,
effect for short-term, high-intensity exercise. However,
110 6 19 [beats/min]; p , 0.01) (Table 4). Postexercise values
several of our participants reported feeling shaky or jittery
were significantly higher for SBP compared with resting
during the exercise testing. Thus, a higher dose of caffeine
values within each treatment (precaffeine, 114 6 10 vs.
might have negatively impacted their performance. Furtherpostcaffeine, 136 6 14; preplacebo, 116 6 12 vs. postplacebo,
more, the potential to improve may be small and difficult to
135 6 14 [mm Hg]; p , 0.01) (Table 4). Postexercise values
measure in short-term, high-intensity exercise performance.
were significantly lower for DBP compared with pre-exercise
Only limited research has examined the impact of caffeine
values within each treatment (precaffeine, 72 6 8 vs.
during high-intensity, team-sport field performance exercises
postcaffeine, 63 6 6; preplacebo, 76 6 6 vs. postplacebo,
(32,37,39,40). In the present study, no significant perfor63 6 9 [mm Hg]; p , 0.01) (Table 4). No differences in HR
mance improvement was observed with caffeine ingestion
Pre
Post
Pre
Post
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Caffeine as Ergogenic Aid in Football Players
during the 40-yard dash and 20-yard shuttle. For these fieldtests, a performance improvement was seen with the caffeine
for 59% of the participants during the 40-yard dash but
only for 47% during the 20-yard shuttle. Our results are
similar to Paton et al. (37), who also did not find significant
improvement with caffeine using team-sport athletes in
20-meter repeated sprints. In their study, they used a slightly
higher dose of caffeine (6 mg/kg BW). Historic use of
caffeine was not reported in this study. Lorino et al. (32) also
found that a 6 mg/kg dose of caffeine did not improve agility
as measured by the pro-agility run test or power output as
measure by the Wingate test. The participants in this
study were recreationally active young males who were not
habituated to caffeine.
However, Stuart et al. (40) found significant improvements
in exercise performance in team-sport athletes in repeated
bouts of sprint, power, and accuracy tests lasting 3 to14
seconds. In their study, they also used 6 mg/kg BW of
caffeine, and all the participants stated that they were regular
consumers of caffeine in their diet. Schneiker et al. (39) also
found a positive impact of caffeine on exercise performance
in competitive male team-sport athletes. The research
participants consumed either caffeine (6 mg/kg) or a placebo
and then completed prolonged intermittent-sprint exercise
tests on a cycle ergometer. No information was provided on
the historic use of caffeine of the research participants.
In the present study, no significant differences were
observed between treatments for RPE during any of the
exercise tests. These results are similar to the results of several
other short-term, high-intensity exercise protocols (4,12).
One published study using a short-term, high-intensity
exercise protocol reported a significantly lower RPE after
caffeine ingestion (16). Furthermore, a recent meta-analysis
found that caffeine reduces RPE during exercise, and the
study stated that this may explain the ergogenic effect of
caffeine on exercise performance (15). However, during
short-term, high-intensity exercise protocols, RPE may not
be a sensitive dependent variable.
Variable cardiac responses have been reported with acute
caffeine ingestion. Most researchers found no impact of acute
caffeine ingestion on resting HR (3,6,8,12,36). However, one
study reported an increase in resting HR after acute caffeine
ingestion (38). Most research also reports that caffeine
may increase postexercise HR but not significantly when
compared with a placebo trial (4,6,12,28,36). Our data are in
agreement with the findings of the majority of the research
literature. We found that resting HR was not significantly
different between trials. HR was significantly increased after
exercise in both trials, but no significant differences were seen
between treatments.
Fewer studies have examined the impact of caffeine on BP
response to exercise. We found no significant differences in
BP between trials. Other research has reported no significant
differences in resting (3,24,26) or postexercise (36) BP
readings after caffeine ingestion.
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CONCLUSIONS
Caffeine ingestion did not statistically improve exercise
performance during the bench press, 40-yard dash, and
20-yard shuttle. During the caffeine treatment, 59% of the
individual participants improved in the bench press, 59%
improved in the 40-yard dash, and 47% improved in the
20-yard shuttle. The potential to improve short-term, highintensity exercise performance may be small and difficult to
measure. Our participants were low users of caffeine and may
have experienced more negative side effects to the caffeine.
More research is needed examining the effect of caffeine
during field tests specific to the athletes’ competition or training regimen. Different doses of caffeine should be examined.
In addition, the participants in this study were either caffeine
naı̈ve or very low caffeine consumers, which may have
contributed to the study results. Thus, research is needed that
compares the effect of caffeine in caffeine naı̈ve vs. habituated
caffeine consumers in anaerobic exercise performance.
PRACTICAL APPLICATION
This study found that caffeine (5 mg/kg BW) did not statistically improve exercise performance in caffeine naı̈ve football
players completing field-based anaerobic exercise tests (40yard dash, 20-yard shuttle, and a bench press) used during the
NFL Combine. Also, no differences were found between
treatments for RPE, HR, and BP. However, 59% of the
individual participants improved performance with the
caffeine during the bench press and the 40-yard dash.
Because caffeine did not statistically improve exercise performance, it would not be recommended for a coach or personal
trainer to suggest a moderate dose of caffeine in caffeine naı̈ve
football players as a method to improve performance.
ACKNOWLEDGMENTS
Grant Support: Experimental and Applied Science, Inc.
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