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Acute Effects of Caffeine on Strength Performance in Trained and Untrained Individuals

20 Dec 2015-Journal of Athletic Enhancement (SciTechnol)-Vol. 2015, Iss: 2, pp 1-5

TL;DR: It is suggested that both a caffeine supplementation and placebo improve 1 RM in untrained individuals but do not improve performance in resistance trained athletes.

AbstractAcute Effects of Caffeine on Strength Performance in Trained and Untrained Individuals Objective: The primary aim of this study was to compare the acute effects of a caffeine based supplement on the strength performance of trained and untrained individuals with a secondary investigation into the effects of a placebo. Method: Seven resistance trained (>6 months) and seven untrained (<6 months) males (mean ± SD: age: 21 ± 3 y, mass: 75.2 ± 11.3 kg, height: 176 ± 6 cm) consumed either caffeine (CAF) (5 mg.kg.bw-1), placebo (PLA) or nothing (CON) 60 minutes prior to 1 RM squat measurements in a double-blinded, repeated measures design. A two way repeated measures ANOVA was applied to test for the main effects of condition (CAF, PLA, CON) and group (Trained, Untrained), and the interaction effect (condition x group). Results: A significant interaction effect (F(2,11)=4.38, p=0.024) for 1 RM was observed. In the untrained group there was significant difference between CON and PLA (p<0.001). On average 1 RM in the untrained group was 12% lower in the CON trial (92.1 kg) compared to the PLA (102.9 kg; 95% CI=-5.3 to -16.1 kg), and 9% lower compared to CAF (p=0.005; 95% CI=-2.7 to 14.5 kg). There was no significant difference in 1 RM in the untrained group between PLA and CAF (p=0.87, 95% CI -3.2 to 7.5 kg). Additionally, there were no significant differences for the trained group between conditions. There was also a significant main effect for condition for 1 RM (F(2,11)=12.81, p<0.001) . Overall the CON trial was 6% lower (p=0.001, 95% CI=-3.0 to -10.6 kg) than the PLA trial (117.9 kg; 95% CI 97.6 to 124.6 kg), and 5% lower (p=0.12, 95% CI=-1.2 to -9.5 kg) than the CAF trial (116.4 kg; 95% CI 105.0 to 127.8 kg). There was no significant difference between PLA and CAF (p=0.951). Finally, there was a significant main effect for group (F(1,12)=8.79, p=0.12). On average 1 RM was 25% higher in the trained group (131.7 kg; 95% CI=114.5 to 148.9 kg) compared to the untrained group (98.6 kg; 95% CI=81.4 to 115.8 kg). Conclusion: These findings suggest that both a caffeine supplementation and placebo improve 1 RM in untrained individuals but do not improve performance in resistance trained athletes. No significant differences between caffeine and placebo, suggests placebo induced mechanisms also need to be considered.

Summary (2 min read)

Introduction

  • These findings suggest that both a caffeine supplementation and placebo improve 1 RM in untrained individuals but do not improve performance in resistance trained athletes.
  • In terms of studies that have investigated the mechanisms associated with enhanced performance during strength based exercise, contradicting results have been published in terms of muscle activation.

Experimental approach to the problem

  • A double-blind, repeated-measures, cross over design was applied.
  • Treatment order (CAF, PLA, CON] was randomly assigned and counterbalanced.
  • Subjects attended the laboratory on four separate occasions (Preliminary Measures/ Familiarisation, Condition 1, Condition 2 and Condition 3) all separated by 1 week.
  • Electromyography (vastus lateralis) and vertical force production were assessed during the lift to measure for muscle activation and peak force production.

Subjects

  • All subjects categorised themselves as healthy and free from injury or illness.
  • Only non-smoking individuals of a normal body weight (BMI=18-29) were enlisted to avoid the increased rate of caffeine degradation [39].
  • Inclusion criteria stipulated that subjects had been either resistance training at least 3 days a week for the past 6 months or had not partaken in regular resistance training for the past 6 months (un).
  • All testing procedures were verbally explained and a written information sheet was given to all subjects.
  • If resting blood pressure was ≥ 140/90 mmHg the subject was removed from the study.

Familiarisation/Preliminary measures

  • Preliminary measurements for age, height (Stadiometer, Harpendon: HAR-98.602), mass (Tanita: BWB0800) and blood pressure were obtained in the first laboratory visit.
  • Familiarisation processes were instructed by a level 3 personal trainer in which the correct technique for the barbell squat was taught [41].
  • Dynamic stretches were used rather than static due to potential loss of power and strength [42].
  • All results from the preliminary 1 RM were discarded and not included in the analysis.
  • Subjects returned to the lab 7 days later for the first session of testing.

Testing protocol

  • Subjects were randomly allocated in the second visit to consume either a caffeine (CAF) supplement (5 mg.kg.bw-1) a placebo (PLA) (Dextrose, 5 mg.kg.bw-1) or nothing (CON).
  • Supplements were administered in capsule form and taken with 300 ml of water allowing for decreased discomfort and taste.
  • The squat was performed whilst standing on a force plate (Kistler, Type 9281) to measure peak vertical force (PVF) throughout the movement.
  • Immediately following the 1 RM test, a 5 second maximal isometric contraction was performed against a fixed smith machine barbell at a knee angle of 135˚ to normalise EMG readings [43].
  • Electrodes were placed according to SENIAM instructions and recommendations (SENIAM, http://www.seniam.org).

Statistical analysis

  • Descriptive statistics were obtained for age, height, mass and blood pressure.
  • To determine muscle activation, an EMG percentage was calculated by dividing peak contraction by IMVC and multiplying by 100 [43].
  • If Mauchly's test of sphericity was observed as non-significant (p>0.05) then sphericity assumed results were reported.
  • All results are presented as mean ± standard deviation (Table 1).

Discussion

  • Both acute caffeine and placebo supplementation significantly increased back squat 1 RM measurements in untrained individuals averaging increases of 11% and 9% respectively.
  • Results found therefore contradict those previously reported on untrained individuals when no significant increase was observed [21,22].
  • Results found do however coincide with those previous reported in muscular endurance [31-33].
  • Caffeine did not vary significantly from placebo in all performance measures taken from both groups.
  • Unfortunately, the measuring of these mechanisms was out of the scope of this study.

1 RM (KG)

  • No distinct disparity between caffeine and placebo conditions, even when significant increases were observed, suggests placebo induced mechanisms also need to be considered.
  • Increased expectancy and belief in caffeine supplements has previously been shown to increase their ergogenic properties [44].
  • Increased expectancy in a performance enhancing supplement can provide an athlete with greater arousal levels [46] which can in turn increase performance, especially in open, simple tasks [47].
  • This phenomenon does not explain the variation in results observed in the present study between trained and untrained individuals, suggesting the cause for disparity may be more complex.
  • Further research aimed at elucidating the main mechanisms involved in the variability between individuals has been previously reported [19,20].

Practical Applications

  • There was no significant effect observed in either force production or muscle activity throughout the maximal lift.
  • This evidence therefore suggests that a caffeine supplement may not be an appropriate ergogenic aid when strength based movements are the main focus.
  • Improved performance was however observed in untrained individuals meaning caffeine or placebo administration may be beneficial for improving performance in the initial uptake of resistance training.

Conclusion

  • The ingestion of caffeine can be utilised by an athlete when endurance and muscular endurance performance is the priority.
  • In terms of muscular strength this piece of research adds to a compilation of work suggesting that caffeine may not provide an ergogenic benefit.

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a SciTechnol journal
Research Article
Brooks et al., J Athl Enhancement 2015, 4:6
http://dx.doi.org/10.4172/2324-9080.1000217
Journal of Athletic
Enhancement
International Publisher of Science,
Technology and Medicine
All articles published in Journal of Athletic Enhancement are the property of SciTechnol, and is protected by copyright laws.
Copyright © 2015, SciTechnol, All Rights Reserved.
Acute Effects of Caffeine on
Strength Performance in Trained
and Untrained Individuals
Joseph H Brooks
1
, Kevin Wyld
1
and Bryna CR Chrismas
2
*
Abstract
Objective: The primary aim of this study was to compare the acute
effects of a caffeine based supplement on the strength performance
of trained and untrained individuals with a secondary investigation
into the effects of a placebo.
Method: Seven resistance trained (>6 months) and seven untrained
(<6 months) males (mean ± SD: age: 21 ± 3 y, mass: 75.2 ± 11.3 kg,
height: 176 ± 6 cm) consumed either caffeine (CAF) (5 mg.kg.bw
-1
),
placebo (PLA) or nothing (CON) 60 minutes prior to 1 RM squat
measurements in a double-blinded, repeated measures design. A
two way repeated measures ANOVA was applied to test for the
main effects of condition (CAF, PLA, CON) and group (Trained,
Untrained), and the interaction effect (condition x group).
Results: A signicant interaction effect (F
(2,11)
=4.38, p=0.024) for
1 RM was observed. In the untrained group there was signicant
difference between CON and PLA (p<0.001). On average 1 RM
in the untrained group was 12% lower in the CON trial (92.1 kg)
compared to the PLA (102.9 kg; 95% CI=-5.3 to -16.1 kg), and
9% lower compared to CAF (p=0.005; 95% CI=-2.7 to 14.5 kg).
There was no signicant difference in 1 RM in the untrained group
between PLA and CAF (p=0.87, 95% CI -3.2 to 7.5 kg). Additionally,
there were no signicant differences for the trained group between
conditions. There was also a signicant main effect for condition for
1 RM (F
(2,11)=
12.81, p<0.001) . Overall the CON trial was 6% lower
(p=0.001, 95% CI=-3.0 to -10.6 kg) than the PLA trial (117.9 kg; 95%
CI 97.6 to 124.6 kg), and 5% lower (p=0.12, 95% CI=-1.2 to -9.5 kg)
than the CAF trial (116.4 kg; 95% CI 105.0 to 127.8 kg). There was
no signicant difference between PLA and CAF (p=0.951). Finally,
there was a signicant main effect for group (F
(1,12)
=8.79, p=0.12).
On average 1 RM was 25% higher in the trained group (131.7 kg;
95% CI=114.5 to 148.9 kg) compared to the untrained group (98.6
kg; 95% CI=81.4 to 115.8 kg).
Conclusion: These ndings suggest that both a caffeine
supplementation and placebo improve 1 RM in untrained individuals
but do not improve performance in resistance trained athletes. No
signicant differences between caffeine and placebo, suggests
placebo induced mechanisms also need to be considered.
Keywords
One repetition maximum; Squat; Placebo; Force; Muscle activation;
Supplementation
*Corresponding author: Dr Bryna Chrismas, Sport Science Program,
College of Arts and Sciences, Qatar University, Doha, Qatar, Tel: +974 7056
7602; E-mail: bchrismas@qu.edu.qa
Received: October 28, 2015 Accepted: December 14, 2015 Published:
December 20, 2015
Introduction
Caeine is one of the highest consumed drugs in the world with
74% of elite athletes now consuming it prior to competition [1].
Caeine antagonises adenosine by binding to its receptors, reducing
its ability to slow neural activity, reduce arousal, and induce sleep [2].
Additionally, altering of metabolic substrate utilisation may occur
when caeine is present, with increased fat oxidation and glycogen
sparing equating to increased endurance performance [3]. Enhanced
secretion of β-endorphins has also been documented, allowing
for prolonged performance as a result of reduced pain perception
[4]. Mechanisms of action in terms of strength performance are
still not clear, however, theories for both central and peripheral
factors have been postulated [5]. Possible mechanisms may include
increased muscle activation, motor unit recruitment [6,7], and
enhanced excitation contraction coupling [6]. e eect of caeine
as an adenosine antagonist may also increase maximal voluntary
contraction through increased neurotransmitter release, increased
ring rates, and increased spontaneous and evoked potentials [8].
Support for the benets of caeine is plentiful when investigating
endurance based performance [9-11]. Signicant enhancements in
cycling [12-14], swimming [15] and rowing [16] have been reported
following caeine ingestion. A plethora of research also highlights
the use of caeine to improve muscular endurance; with regards to
greater repetitions to failure [17], lower ratings of perceived exertion
[18] and reduced fatigue [17]. However, reports of increased muscular
strength performance are less established, and oen more equivocal.
In one study [19], a 5 mg.kg.bw
-1
caeine dose signicantly enhanced
bench press 1 RM in resistance trained females. Furthermore, 201
mg of caeine signicantly increased bench press 1 RM in trained
men [20] but had no eect on leg extension 1 RM. In untrained
men, a similar caeine dose had no eect on bench press 1 RM [21].
Hendrix et al. [22] also showed no increase in bench press 1 RM or
leg extension 1 RM in untrained individuals following 400 mg of
caeine. Similarly, no improvement in trained men was shown for
bench press or lat pull down 1 RM following 300 mg caeine [23].
Eckerson et al. [24] also showed no signicant increase in bench press
1 RM in trained individuals following 160mg of caeine vs. placebo.
Furthermore, no increase in bench press or leg press 1 RM compared
to placebo was shown in resistance trained men [25]. Consequently,
it appears that training status, and exercise type may help explain the
equivocal eects of caeine. Despite this, the eects of training status
have only been researched directly in endurance tasks. For example,
Collomp et al. [15] displayed a signicant reduction in swimming
time trials of elite swimmers, with no signicant improvement in
recreational swimmers, following 250 mg caeine supplementation.
However, these results are not transferable to strength tasks revealing
a distinct need for further research in this area.
In terms of studies that have investigated the mechanisms
associated with enhanced performance during strength based
exercise, contradicting results have been published in terms of
muscle activation. Multiple studies have shown signicant increases
in healthy individuals [26-28] however no signicant dierence was
produced in high level runners [29]. None of these studies have
however employed dynamic compound movements and/or utilised

Citation: Brooks JH, Wyld K, Chrismas BCR (2015) Acute Effects of Caffeine on Strength Performance in Trained and Untrained Individuals. J Athl Enhancement
4:6.
Page 2 of 5
doi:http://dx.doi.org/10.4172/2324-9080.1000217
Volume 4 • Issue 6 • 1000217
muscle activation measurements during movements used by elite
athletes in training and competition, which have been shown to
increase performance [30]. Subsequently, more applicable research in
this area is clearly warranted.
Interestingly caeine placebos have been shown to signicantly
increase the performance of both endurance and muscular endurance
based tasks, oen to a similar degree to real caeine supplements [31-
33]. Enhanced muscular work output [33] and reports of caeine-
related symptoms post placebo ingestion have been shown [31].
In addition, improved repetitions to failure and reduced RPE [32]
have also been documented. e side eects of caeine have been
well documented [34] and common symptoms for example sleep
deprivation [35] may inhibit an athlete's ability to recover eectively.
If caeine-related benets can be replicated via placebo ingestion,
removing the negative side eects, then this may oer an interesting
insight for coaches. Research has currently failed to measure the
possible magnitude of improvement from a caeine placebo during
1 RM lis although they have been shown to increase sporting
performance [36]. Research into the eects of a placebo on this type
of muscular action would allow for better application of research into
both training and competition.
e aim of the current study was to therefore investigate whether
acute consumption of a caeine based supplement (5 mg.kg.bw
-1
)
would signicantly improve strength performance in trained and
untrained individuals. An additional goal was to investigate the
caeine placebo eects on strength based tasks. It was hypothesised
that both caeine and a placebo would signicantly increase 1 RM
performance trained subjects but have no eect on untrained.
Methodology
Experimental approach to the problem
A double-blind, repeated-measures, cross over design was
applied. Treatment order (CAF, PLA, CON] was randomly assigned
and counterbalanced. Trials were performed at the same time of
day (9:00-12:00] to avoid diurnal variation [37]. Subjects attended
the laboratory on four separate occasions (Preliminary Measures/
Familiarisation, Condition 1, Condition 2 and Condition 3) all
separated by 1 week. A smith machine (Pullum: Pullum Pro) was
used to assess 1 RM measurements for the barbell back squat on all
occasions. Electromyography (vastus lateralis) and vertical force
production were assessed during the lift to measure for muscle
activation and peak force production. A maximal isometric
contraction on a fixed barbell was then performed to normalise
EMG data and calculate a percentage of muscle activity. Statistical
tests were conducted to test a trained group (n=7) and untrained
group (n=7).
Subjects
Seven resistance trained and seven non-resistance trained male
subjects (white, British, age: 21 ± 3 y, mass: 75.2 ± 11.3 kg, height: 176
± 6 cm) volunteered to be included in this experiment. All subjects
categorised themselves as healthy and free from injury or illness. Only
male subjects were recruited to remove potential variability caused
by a menstrual cycle inuence when measuring caeine response in
a female population [38]. Only non-smoking individuals of a normal
body weight (BMI=18-29) were enlisted to avoid the increased rate of
caeine degradation [39]. Inclusion criteria stipulated that subjects
had been either resistance training at least 3 days a week for the past
6 months (trained) or had not partaken in regular resistance training
for the past 6 months (untrained). Typical training for the ‘‘trained’’
group included both upper and lower body resistance training at a
moderate to high repetition range [6-12] and intensity (70-90%
1RM). All testing procedures were verbally explained and a written
information sheet was given to all subjects. Informed consent and
a physical activity readiness questionnaire was completed prior to
participation. A preliminary blood pressure test (Omron, M5-I) was
carried out prior to any testing as well as a pre-test questionnaire. If
resting blood pressure was ≥ 140/90 mmHg the subject was removed
from the study. All subjects had a resting blood pressure less than
this cut o, and therefore, no subjects were removed. Subjects were
advised to maintain their normal lifestyle patterns apart from being
instructed to not participate in vigorous activity 48 hours prior to
testing. Subjects were also required to abstain from consuming any
other caeine throughout testing. Additionally, no caeine was to
be consumed within 5 days of starting the experiment to allow for
caeine withdrawal to potentiate eects of acute ingestion [40].
Ethical approval was gained from the University of Bedfordshire
prior to any data collection.
Familiarisation/Preliminary measures
Preliminary measurements for age, height (Stadiometer,
Harpendon: HAR-98.602), mass (Tanita: BWB0800) and blood
pressure were obtained in the rst laboratory visit. Familiarisation
processes were instructed by a level 3 personal trainer in which the
correct technique for the barbell squat was taught [41]. Subjects
were trained to squat to a knee angle of 90˚ for standardisation.
Preliminary 1 RM squats were performed on the smith machine to
familiarise the subjects with the 1 RM protocol as well as exercise
technique. One repetition maximum measurements were recorded as
the maximum amount of weight lied in which the correct technique
was maintained [41]. All 1 RM tests began with a 5 minute warm up
on a cycle ergometer (Monark, 824e) at 100 W followed by dynamic
stretches (2x15 leg swings each leg) and body weight squats (2 x 12
repetitions). Dynamic stretches were used rather than static due to
potential loss of power and strength [42]. A 5 minute cool down was
performed on a cycle ergometer (Monark, 824e) at 100 W followed
by static stretches for the lower body post testing. All results from the
preliminary 1 RM were discarded and not included in the analysis.
Subjects returned to the lab 7 days later for the rst session of testing.
Testing protocol
Subjects were randomly allocated in the second visit to consume
either a caeine (CAF) supplement (5 mg.kg.bw
-1
) a placebo (PLA)
(Dextrose, 5 mg.kg.bw
-1
) or nothing (CON). Supplements were
administered in capsule form and taken with 300 ml of water allowing
for decreased discomfort and taste. One hour post consumption,
1 RM back squat was performed on a smith machine (Pullum,
Luton, UK) following an identical protocol as the preliminary tests.
e squat was performed whilst standing on a force plate (Kistler,
Type 9281) to measure peak vertical force (PVF) throughout the
movement. Electromyography (EMG) was used to measure peak
contraction (PC) using Kendall ARBO EMG electrodes and recorded
using Powerlab soware (Version 5) with RMS smoothed data being
analysed. Immediately following the 1 RM test, a 5 second maximal
isometric contraction was performed against a xed smith machine
barbell at a knee angle of 135˚ to normalise EMG readings [43]. A
peak value from the 5 seconds was used to determine an isometric
maximal voluntary contraction (IMVC). Electromyography activity
was recorded in the vastus lateralis with a ground electrode placed on

Citation: Brooks JH, Wyld K, Chrismas BCR (2015) Acute Effects of Caffeine on Strength Performance in Trained and Untrained Individuals. J Athl Enhancement
4:6.
Page 3 of 5
doi:http://dx.doi.org/10.4172/2324-9080.1000217
Volume 4 • Issue 6 • 1000217
the knee. Electrodes were placed according to SENIAM instructions
and recommendations (SENIAM, http://www.seniam.org). Location
preparation included the shaving and cleaning of the skin using an
alcohol solution. Identical testing protocols including warm up and
cool down were applied for all subjects, for all three conditions.
Statistical analysis
Data was analysed using SPSS 19 from SPSS Inc. (SPSS 19.0 for
Windows, SPSS, Chicago, IL). All data was deemed to be normally
distributed by observation of quantile-quantile (Q-Q) plots.
Descriptive statistics were obtained for age, height, mass and blood
pressure. To determine muscle activation, an EMG percentage was
calculated by dividing peak contraction by IMVC and multiplying
by 100 [43]. One repetition maximum, EMG % and PVF were all
analysed using a two way repeated measures analysis of variance
(ANOVA) to test for signicant dierences between condition (CAF,
PLA CON) and group (trained, untrained), and the interaction eect
(condition x group). If Mauchly's test of sphericity was observed
as non-signicant (p>0.05) then sphericity assumed results were
reported. In the case of Mauchly's test being deemed as signicant
(p<0.05), then results derived from a Greenhouse-Geisser test were
reported. Following a signicant F value, direction and magnitude of
dierence amongst means were determined using a Bonferroni post
hoc test. Signicance level was set at p<0.05. All results are presented
as mean ± standard deviation (Table 1).
Results
One repetition maximum
A signicant interaction eect (F=4.38, p=0.024) for 1 RM was
observed. In the untrained group there was signicant dierence
between CON and PLA (p<0.001). On average 1 RM in the untrained
group was 12% lower in the CON trial (92.1 kg) compared to the PLA
(102.9 kg; 95% CI=-5.3 to -16.1 kg), and 9% lower compared to CAF
(p=0.005; 95% CI=-2.7 to 14.5 kg). ere was no signicant dierence
in 1 RM in the untrained group between PLA and CAF (p=0.87, 95%
CI -3.2 to 7.5 kg) (Figure 1). Additionally, there were no signicant
dierences for the trained group between conditions. ere was also
a signicant main eect for condition for 1 RM (F
(2,11)=
12.81, p<0.001)
. Overall the CON trial was 6% lower (p=0.001, 95% CI=-3.0 to -10.6
kg) than the PLA trial (117.9 kg; 95% CI 97.6 to 124.6 kg), and 5%
lower (p=0.12, 95% CI=-1.2 to -9.5 kg) than the CAF trial (116.4
kg; 95% CI 105.0 to 127.8 kg) (Figure 2). ere was no signicant
dierence between PLA and CAF (p=0.951). Finally, there was a
signicant main eect for group (F
(1,12)
=8.79, p= 0.12). On average
1 RM was 25% higher in the trained group (131.7 kg; 95% CI=114.5
to 148.9 kg) compared to the untrained group (98.6 kg; 95% CI=81.4
to 115.8 kg).
Muscle activation
No signicant interaction eect for muscle activation was
revealed (F
(2,11)
=0.386, p=0.684). ere was also no signicant main
eect for condition (F
(2,11)
=0.51 p=0.61) or group (F
(1,12)
=1.69, p=0.22,
95% CI=-11.86 to 46.98%).
Force production
A signicant main eect was revealed for group (F
(1,12)
=8.91,
p=0.01) with average MVF 53% higher in the trained group (2474.98
N; 95% CI=2029.94 to 2920.03 N ) compared to the untrained group
(1612.68 N; 95% CI=1167.64 to 2057.73 N). No signicant interaction
eect was observed (F
(2,11)
=0.311, p=0.735). ere was also no
signicant main eect for condition (F
(2,11)
=2.63, p=0.12).
Discussion
Both acute caeine and placebo supplementation signicantly
increased back squat 1 RM measurements in untrained individuals
averaging increases of 11% and 9% respectively. To the authors’
knowledge, this is the rst study to report signicant increases of 1
RM squat measurements in untrained individuals following caeine
supplementation. Results found therefore contradict those previously
reported on untrained individuals when no signicant increase was
observed [21,22]. In terms of placebo ingestion, this study was the
rst to investigate the eect of a caeine placebo on 1 RM strength
performance. Results found do however coincide with those previous
reported in muscular endurance [31-33].
No signicant dierence was found for trained individuals
following caeine ingestion although a mean increase of 2%
was observed. is supports the collection of previous research
documenting no signicant increase [20,23-25]. It does however
contradict the research reporting signicant increases of 1 RM bench
press in resistance trained women [19] and men [20] although non-
signicant percentage increases of a similar degree were observed.
Dierent muscle groups tested may have inuence on degree of
variation observed which may explain the results presented. A
placebo supplement failed to signicantly increase 1 RM in trained
individuals. As mentioned, this study was the rst to investigate the
eect of a caeine placebo on 1 RM strength. However, in comparison
to research obtained measuring muscular endurance [31-33] these
ndings did not support those previously published.
Although placebo ingestion failed to signicantly increase
performance in trained individuals, caeine did not vary signicantly
from placebo in all performance measures taken from both groups.
erefore, the hypothesis that placebo would produce a similar
response to caeine was met and supports previous research into
caeine placebos [28,31,32]. Muscle activation and force production
did not signicantly increase in either trained or untrained
individuals supporting some previously published research [6,29]
and contradicting others [27,28]. e lack of signicant increase in
muscle activation and force production, in either group, suggests
that previously devised mechanisms of neurotransmitter release
and firing rates were either not increased through the antagonising
of adenosine or were increased but had no eect on strength
performance. Unfortunately, the measuring of these mechanisms was
out of the scope of this study. A probable cause is the lower dosage of
Control Placebo Caffeine
1 RM (KG)
Trained 130±17.1 132.1±13.5 132.9±13.1
Untrained 92.1±27.9 100.7±24.2* 102.8±24.1*
EMG Percentage (%)
Trained 120.9±34.5 130.1±43.9 124.9±29.2
Untrained 105.8±21.4 105.5±14.2 111.9±24
Force Production (N)
Trained 2407.4±614.3 2324.6±798.5 2692.8±525.9
Untrained 1431.1±594 1586.9±617.8 1819.9±608.4
* Signicantly greater than control.
Table 1: Descriptive statistics for Trained (n=7) and Untrained (n=7) groups
within Control, Placebo and Caffeine conditions. All values are mean ± standard
deviation.

Citation: Brooks JH, Wyld K, Chrismas BCR (2015) Acute Effects of Caffeine on Strength Performance in Trained and Untrained Individuals. J Athl Enhancement
4:6.
Page 4 of 5
doi:http://dx.doi.org/10.4172/2324-9080.1000217
Volume 4 • Issue 6 • 1000217
caeine administered (5 mg.kg.bw
-1
) within this study in comparison
to previous research which has shown a signicant increase in muscle
activation [27,28].
No distinct disparity between caeine and placebo conditions,
even when signicant increases were observed, suggests placebo
induced mechanisms also need to be considered. Increased
expectancy and belief in caeine supplements has previously been
shown to increase their ergogenic properties [44]. is eect has
also been previously imitated through placebo consumption [45].
Increased expectancy in a performance enhancing supplement can
provide an athlete with greater arousal levels [46] which can in turn
increase performance, especially in open, simple tasks [47]. However,
this phenomenon does not explain the variation in results observed
in the present study between trained and untrained individuals,
suggesting the cause for disparity may be more complex. Further
research aimed at elucidating the main mechanisms involved in the
variability between individuals has been previously reported [19,20].
is research provides the understanding that neither training
status nor placebo eects are complex enough explanations for the
continuing disparity in data.
Practical Applications
Compared to a control condition, a caeine supplement did
not signicantly increase 1 RM squat measurements of trained
athletes. ere was no signicant eect observed in either force
production or muscle activity throughout the maximal li. is
evidence therefore suggests that a caeine supplement may not be
an appropriate ergogenic aid when strength based movements are
the main focus. Improved performance was however observed in
untrained individuals meaning caeine or placebo administration
may be benecial for improving performance in the initial uptake of
resistance training.
Conclusion
e ingestion of caeine can be utilised by an athlete when
endurance and muscular endurance performance is the priority. In
terms of muscular strength this piece of research adds to a compilation
of work suggesting that caeine may not provide an ergogenic benet.
Any benet seen in strength and power based movements is likely
to be caused by a degree of expectation and belief when ingesting a
substance. It is also understood that the magnitude of eect may be
determined on an individual basis for which training status may be
a factor.
Acknowledgements
The authors would like to thank the subjects for their participation in this
research. A special mention would also like to be made to the laboratory staff
at the University of Bedfordshire for their hard work and patience during the
collection of data.
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Figure 1: Individual one repetition maximum measurements for untrained
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Caffeine (CAF) conditions. N=7.
Figure 2: Individual one repetition maximum measurements for trained
individuals within Familiarization (FAM), Control (CON), Placebo (PLA) and
Caffeine (CAF) conditions. N=7.

Citation: Brooks JH, Wyld K, Chrismas BCR (2015) Acute Effects of Caffeine on Strength Performance in Trained and Untrained Individuals. J Athl Enhancement
4:6.
Page 5 of 5
doi:http://dx.doi.org/10.4172/2324-9080.1000217
Volume 4 • Issue 6 • 1000217
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Au thor Af liation Top
1
Department of Sport and Exercise Science, Institute of Sport and Physical
Activity Research, (ISPAR), University of Bedfordshire, Bedford, UK
2
Sport Science Program, College of Arts and Sciences, Qatar University, Doha,
Qatar
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Citations
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Journal ArticleDOI
TL;DR: The meta-analyses showed significant ergogenic effects of caffeine ingestion on maximal muscle strength of upper body and muscle power and future studies should more rigorously control the effectiveness of blinding.
Abstract: Caffeine is commonly used as an ergogenic aid. Literature about the effects of caffeine ingestion on muscle strength and power is equivocal. The aim of this systematic review and meta-analysis was to summarize results from individual studies on the effects of caffeine intake on muscle strength and power. A search through eight databases was performed to find studies on the effects of caffeine on: (i) maximal muscle strength measured using 1 repetition maximum tests; and (ii) muscle power assessed by tests of vertical jump. Meta-analyses of standardized mean differences (SMD) between placebo and caffeine trials from individual studies were conducted using the random effects model. Ten studies on the strength outcome and ten studies on the power outcome met the inclusion criteria for the meta-analyses. Caffeine ingestion improved both strength (SMD = 0.20; 95% confidence interval [CI]: 0.03, 0.36; p = 0.023) and power (SMD = 0.17; 95% CI: 0.00, 0.34; p = 0.047). A subgroup analysis indicated that caffeine significantly improves upper (SMD = 0.21; 95% CI: 0.02, 0.39; p = 0.026) but not lower body strength (SMD = 0.15; 95% CI: -0.05, 0.34; p = 0.147). The meta-analyses showed significant ergogenic effects of caffeine ingestion on maximal muscle strength of upper body and muscle power. Future studies should more rigorously control the effectiveness of blinding. Due to the paucity of evidence, additional findings are needed in the female population and using different forms of caffeine, such as gum and gel.

128 citations


Cites background from "Acute Effects of Caffeine on Streng..."

  • ...[2], a number of experimental trials have been published [4, 11–16], presenting novel findings for females [14], trained [4, 16] and untrained men [11, 13], athletes [15], and adolescents [12]; as such, an updated review appears to be warranted....

    [...]


Journal ArticleDOI
TL;DR: It is suggested that caffeine ingestion improves exercise performance in a broad range of exercise tasks and the magnitude of the effect of caffeine is generally greater for aerobic as compared with anaerobic exercise.
Abstract: Objective To systematically review, summarise and appraise findings of published meta-analyses that examined the effects of caffeine on exercise performance. Design Umbrella review. Data sources Twelve databases. Eligibility criteria for selecting studies Meta-analyses that examined the effects of caffeine ingestion on exercise performance. Results Eleven reviews (with a total of 21 meta-analyses) were included, all being of moderate or high methodological quality (assessed using the Assessing the Methodological Quality of Systematic Reviews 2 checklist). In the meta-analyses, caffeine was ergogenic for aerobic endurance, muscle strength, muscle endurance, power, jumping performance and exercise speed. However, not all analyses provided a definite direction for the effect of caffeine when considering the 95% prediction interval. Using the Grading of Recommendations Assessment, Development and Evaluation criteria the quality of evidence was generally categorised as moderate (with some low to very low quality of evidence). Most individual studies included in the published meta-analyses were conducted among young men. Summary/conclusion Synthesis of the currently available meta-analyses suggest that caffeine ingestion improves exercise performance in a broad range of exercise tasks. Ergogenic effects of caffeine on muscle endurance, muscle strength, anaerobic power and aerobic endurance were substantiated by moderate quality of evidence coming from moderate-to-high quality systematic reviews. For other outcomes, we found moderate quality reviews that presented evidence of very low or low quality. It seems that the magnitude of the effect of caffeine is generally greater for aerobic as compared with anaerobic exercise. More primary studies should be conducted among women, middle-aged and older adults to improve the generalisability of these findings.

105 citations


Journal ArticleDOI
TL;DR: It is proposed that a better understanding of the wider, non-direct effects of caffeine on exercise, such as how it modifies sleep, anxiety, and post-exercise recovery, will ensure athletes can maximize the performance benefits of caffeine supplementation during both training and competition.
Abstract: Caffeine is a widely utilized performance-enhancing supplement used by athletes and non-athletes alike. In recent years, a number of meta-analyses have demonstrated that caffeine’s ergogenic effects on exercise performance are well-established and well-replicated, appearing consistent across a broad range of exercise modalities. As such, it is clear that caffeine is an ergogenic aid—but can we further explore the context of this ergogenic aid in order to better inform practice? We propose that future research should aim to better understand the nuances of caffeine use within sport and exercise. Here, we propose a number of areas for exploration within future caffeine research. These include an understanding of the effects of training status, habitual caffeine use, time of day, age, and sex on caffeine ergogenicity, as well as further insight into the modifying effects of genotype. We also propose that a better understanding of the wider, non-direct effects of caffeine on exercise, such as how it modifies sleep, anxiety, and post-exercise recovery, will ensure athletes can maximize the performance benefits of caffeine supplementation during both training and competition. Whilst not exhaustive, we hope that the questions provided within this manuscript will prompt researchers to explore areas with the potential to have a large impact on caffeine use in the future.

64 citations


Journal ArticleDOI
TL;DR: Individuals competing in events in which strength and power are important performance-related factors may consider taking 6 mg kg−1 of caffeine pre-training/competition for performance enhancement.
Abstract: The goal of this randomized, double-blind, cross-over study was to assess the acute effects of caffeine ingestion on muscular strength and power, muscular endurance, rate of perceived exertion (RPE...

64 citations


Cites background or methods from "Acute Effects of Caffeine on Streng..."

  • ...Brooks, Wyld, and Chrismas (2015) found no increase in 1RM machine-based back squat exercise in a group of seven trained males....

    [...]

  • ...The discrepancies between the studies may be due to the following: Brooks et al. (2015) used back squat exercise performed on the Smith machine, a lower dose (5 mg kg−1) and a different form (capsule) of caffeine....

    [...]


01 Sep 2013
Abstract: PURPOSE: This study examined the effects of overnight sleep deprivation on recovery following competitive rugby league matches. METHODS: Eleven male, amateur rugby league players performed two competitive matches, followed by either a normal night's sleep (~8h; CONT) or a sleep deprived night (~0h; SDEP) in a randomised fashion. Testing was conducted the morning of the match, and immediately post-match, 2h post and the next morning (16h post-match). Measures included counter-movement jump (CMJ) distance, knee extensor maximal voluntary contraction (MVC), voluntary activation (VA), venous blood creatine kinase (CK) and C-reactive protein (CRP), perceived muscle soreness and a word-colour recognition cognitive function test. Percent change between post- and 16h post-match was reported to determine the effect of the intervention the next morning. RESULTS: Large effects indicated a greater post- to 16h post-match percentage decline in CMJ distance following SDEP compared to CONT (P=0.10-0.16; d=0.95-1.05). Similarly, the percentage decline in incongruent word-colour reaction times were increased in SDEP trials (P=0.007; d=1.75). Measures of MVC did not differ between conditions (P=0.40-0.75; d=0.13-0.33), though trends for larger percentage decline in VA were detected in SDEP (P=0.19; d=0.84). Further, large effects indicated higher CK and CRP responses 16h post-match during SDEP compared to CONT (P=0.11-0.87; d=0.80-0.88). CONCLUSIONS: Sleep deprivation negatively affected recovery following a rugby league match, specifically impairing CMJ distance and cognitive function. Practitioners should promote adequate post-match sleep patterns or adjust training demands the next day to accommodate the altered physical and cognitive state following sleep deprivation.

64 citations


References
More filters

Journal ArticleDOI
TL;DR: There was a strong correlation between maximal strength in half squats and sprint performance and jumping height in high level soccer players, and high squat strength did not imply reduced maximal oxygen consumption.
Abstract: Background: A high level of strength is inherent in elite soccer play, but the relation between maximal strength and sprint and jumping performance has not been studied thoroughly. Objective: To determine whether maximal strength correlates with sprint and vertical jump height in elite male soccer players. Methods: Seventeen international male soccer players (mean (SD) age 25.8 (2.9) years, height 177.3 (4.1) cm, weight 76.5 (7.6) kg, and maximal oxygen uptake 65.7 (4.3) ml/kg/min) were tested for maximal strength in half squats and sprinting ability (0–30 m and 10 m shuttle run sprint) and vertical jumping height. Result: There was a strong correlation between maximal strength in half squats and sprint performance and jumping height. Conclusions: Maximal strength in half squats determines sprint performance and jumping height in high level soccer players. High squat strength did not imply reduced maximal oxygen consumption. Elite soccer players should focus on maximal strength training, with emphasis on maximal mobilisation of concentric movements, which may improve their sprinting and jumping performance.

989 citations


"Acute Effects of Caffeine on Streng..." refers background in this paper

  • ...Volume 4 • Issue 6 • 1000217 muscle activation measurements during movements used by elite athletes in training and competition, which have been shown to increase performance [30]....

    [...]


Journal ArticleDOI
TL;DR: It was suggested that improving the power to weight ratio as well as plyometric training involving countermovement and loaded jump-squat training may be more effective for enhancing sport speed in elite players.
Abstract: For many sporting activities, initial speed rather than maximal speed would be considered of greater importance to successful performance. The purpose of this study was to identify the relationship between strength and power and measures of first-step quickness (5-m time), acceleration (10-m time), and maximal speed (30-m time). The maximal strength (3 repetition maximum [3RM]), power (30-kg jump squat, countermovement, and drop jumps), isokinetic strength measures (hamstring and quadriceps peak torques and ratios at 60 degrees .s(-1) and 300 degrees .s(-1)) and 5-m, 10-m, and 30-m sprint times of 26 part-time and full-time professional rugby league players (age 23.2 +/- 3.3 years) were measured. To examine the importance of the strength and power measures on sprint performance, a correlational approach and a comparison between means of the fastest and slowest players was used. The correlations between the 3RM, drop jump, isokinetic strength measures, and the 3 measures of sport speed were nonsignificant. Correlations between the jump squat (height and relative power output) and countermovement jump height and the 3 speed measures were significant (r = -0.43 to -0.66, p < 0.05). The squat and countermovement jump heights as well as squat jump relative power output were the only variables found to be significantly greater in the fast players. It was suggested that improving the power to weight ratio as well as plyometric training involving countermovement and loaded jump-squat training may be more effective for enhancing sport speed in elite players.

610 citations


"Acute Effects of Caffeine on Streng..." refers background in this paper

  • ...Caffeine antagonises adenosine by binding to its receptors, reducing its ability to slow neural activity, reduce arousal, and induce sleep [2]....

    [...]


Journal ArticleDOI
TL;DR: There is a wealth of information from both applied and experimental work, which, when considered together, suggests that sports performance is affected by time of day in normal entrained conditions and that the variation has at least some input from endogenous mechanisms.
Abstract: We discuss current knowledge on the description, impact, and underlying causes of circadian rhythmicity in sports performance. We argue that there is a wealth of information from both applied and experimental work, which, when considered together, suggests that sports performance is affected by time of day in normal entrained conditions and that the variation has at least some input from endogenous mechanisms. Nevertheless, precise information on the relative importance of endogenous and exogenous factors is lacking. No single study can answer both the applied and basic research questions that are relevant to this topic, but an appropriate mixture of real-world research on rhythm disturbances and tightly controlled experiments involving forced desynchronization protocols is needed. Important issues, which should be considered by any chronobiologist interested in sports and exercise, include how representative the study sample and the selected performance tests are, test-retest reliability, as well as overall design of the experiment.

463 citations


"Acute Effects of Caffeine on Streng..." refers methods in this paper

  • ...Trials were performed at the same time of day (9:00-12:00] to avoid diurnal variation [37]....

    [...]


Journal ArticleDOI
TL;DR: Regression analysis revealed that RPE obtained during exercise could account for ∼29% of the variance in the improvement in exercise performance and this may partly explain the subsequent ergogenic effects of caffeine on performance.
Abstract: The purpose of this study was to use the meta-analytic approach to examine the effects of caffeine ingestion on ratings of perceived exertion (RPE) Twenty-one studies with 109 effect sizes (ESs) met the inclusion criteria Coding incorporated RPE scores obtained both during constant load exercise (n=89) and upon termination of exhausting exercise (n=20) In addition, when reported, the exercise performance ES was also computed (n=16) In comparison to placebo, caffeine reduced RPE during exercise by 56% (95% CI (confidence interval), -45% to -67%), with an equivalent RPE ES of -047 (95% CI, -035 to -059) These values were significantly greater (P<005) than RPE obtained at the end of exercise (RPE % change, 001%; 95% CI, -19 to 20%; RPE ES, 000, 95% CI, -017 to 017) In addition, caffeine improved exercise performance by 112% (95% CI; 46-178%) Regression analysis revealed that RPE obtained during exercise could account for approximately 29% of the variance in the improvement in exercise performance The results demonstrate that caffeine reduces RPE during exercise and this may partly explain the subsequent ergogenic effects of caffeine on performance

415 citations


"Acute Effects of Caffeine on Streng..." refers background in this paper

  • ...Typical training for the ‘‘trained’’ group included both upper and lower body resistance training at a moderate to high repetition range [6-12] and intensity (70-90% 1RM)....

    [...]

  • ...Significant enhancements in cycling [12-14], swimming [15] and rowing [16] have been reported following caffeine ingestion....

    [...]


Journal ArticleDOI
TL;DR: The available literature that follows guidelines suggests that performance benefits can be seen with moderate amounts of caffeine, and these benefits are likely to occur across a range of sports, including endurance events, stop-and-go events, and sports involving sustained high-intensity activity lasting from 1-60 min.
Abstract: Athletes are among the groups of people who are interested in the effects of caffeine on endurance and exercise capacity. Although many studies have investigated the effect of caffeine ingestion on exercise, not all are suited to draw conclusions regarding caffeine and sports performance. Characteristics of studies that can better explore the issues of athletes include the use of well-trained subjects, conditions that reflect actual practices in sport, and exercise protocols that simulate real-life events. There is a scarcity of field-based studies and investigations involving elite performers. Researchers are encouraged to use statistical analyses that consider the magnitude of changes, and to establish whether these are meaningful to the outcome of sport. The available literature that follows such guidelines suggests that performance benefits can be seen with moderate amounts (~3 mg.kg-1 body mass) of caffeine. Furthermore, these benefits are likely to occur across a range of sports, including endurance events, stop-and-go events (e.g., team and racquet sports), and sports involving sustained high-intensity activity lasting from 1-60 min (e.g., swimming, rowing, and middle and distance running races). The direct effects on single events involving strength and power, such as lifts, throws, and sprints, are unclear. Further studies are needed to better elucidate the range of protocols (timing and amount of doses) that produce benefits and the range of sports to which these may apply. Individual responses, the politics of sport, and the effects of caffeine on other goals, such as sleep, hydration, and refuelling, also need to be considered.

339 citations


"Acute Effects of Caffeine on Streng..." refers background in this paper

  • ...Support for the benefits of caffeine is plentiful when investigating endurance based performance [9-11]....

    [...]

  • ...Typical training for the ‘‘trained’’ group included both upper and lower body resistance training at a moderate to high repetition range [6-12] and intensity (70-90% 1RM)....

    [...]