The Acute Effects of A Caffeine Containing Supplement on Strength

Grant Weaver, Sam Vaninger, Brett Vihnanek
This study was meant to examine the acute effects of a caffeinecontaining supplement on upper and lower body strength and
muscular endurance as well as anaerobic capabilities. 37
resistance trained men volunteered to participate in this study.
Participants then went through 2 Wingate tests to determine
peak power, and did a 1 rep max test on bilateral leg extension
and free-weight bench press exercises. They rested for at least
2 days before coming back to take the tests again in which
participants were randomly assigned to 1 of 2 groups. Group 1
was given a caffeine-containing supplement while group 2 was
just given a placebo. 1 hour after ingestion participants went
through the same tests again and found an increase in bench
press in the caffeine-containing supplement group, while all
other forms of strength were the same. Thus, the caffeinecontaining supplement may be an effective supplement for
increasing upper body strength and, therefore, could be useful
for competitive and recreational athletes who perform resistance
The caffeine containing supplement (IV) will
increase upper and lower body strength
(DV)as well as muscular endurance (DV) and
anaerobic capabilities (DV)
37 resistance trained men between the ages of
19 and 23
All had at least one year of resistance training for
3-4 days per week.
The subjects varied in both height and weight
No history of medical or surgical events that
could affect the study
None were on any medications
No use of nutritional supplements (protein,
creatine, etc) 6 weeks before the study
Hadn’t participated in any other studies within a
month of being screened for this trial.
Participants were volunteers
Random assignment
Double blind
Placebo controlled
Parallel design
For the first visit, the subjects performed 2 Wingate tests
to determine peak power and mean power.
Wingate test is the most popular anaerobic cycling test
Previous studies reported that it is both a reliable and valid
method to measure anaerobic capabilities.
Subjects cycle against low resistance for 4 min. to warm
up. At command, the subjects then pedaled for 30
seconds as fast as possible against a resistance equal to
7.5% of their body weight.
After a break, the subjects repeated this.
Peak power = highest output (rpm) in a 5 second period
Mean power= Average output over 30 seconds
Average PP and MP from the two tests were the used for
statistical analysis.
24 hours after the Wingates, the subjects
returned to test muscular strength and
1 rep max out for barbell bench press and
bilateral leg extension to test strength
To determine max out, heavier loads were added
until subject couldn’t complete lift. This was
usually achieved within about 5 trials
2 minutes rest was given between all trials.
After 1 RM was determined, subjects rested for 2
min and performed as many reps as possible at
80% of their 1 RM on LE and BP to determine total
volume lifted (muscular endurance).
48 hours later, the subjects returned and
were given the treatment.
Randomly assigned into a supplement and
placebo group (17 in SUPP, 20 in PLAC)
Supplement contained approx. 200 mg of
Placebo was microcrystalline cellulose
The Wingates, 1 RM, and total volume tests
were then repeated in the exact fashion as
they were in the pretest one hour after the
supplement was ingested.
When compared to the placebo, the
supplement had no effect on LE 1RM, LE
However, the supplement resulted in a mean
2.1 kg increase in the 1RM for BP
This concludes that caffeine may be an
effective supplement to increase upper body
strength and could be useful for competitive
and recreational athletes performing
resistance training.
Interaction of selection and treatment: The
study only looked at resistance trained men
aging from roughly 19-23. The study could
have produced different results between
different age groups, gender, and amounts of
resistance training. Simply testing one
demographic doesn’t allow for generalization.
Interaction of setting and treatment: The
subjects were only tested in a lab. Results
may have varied depending on if they were
tested in a competitive or recreational
However, this doesn’t really seem to be much
of a threat to validity, as being in a different
place doesn’t change any of the movements
or lifts.
Interaction of history and treatment: The
caffeine was ingested 1 hour before the post
test. The results may have varied had they
been given the treatment closer to their test
or even over an hour before it.
There were two separate groups, which
eliminated single group threats.
The groups were randomly assigned, eliminating
any multiple group threats.
The study was double blind, so neither the
subjects nor experimenters knew who was
ingesting the SUPP and who was ingesting the
PLAC. This eliminates all social interaction
R 0 X1 0
R 0 X2 0
Overall, the internal validity for this study
seemed very good.
Inadequate preoperational explication: All tests
have been used many times in the past to
measure what they were supposed to measure
and all had been found to be valid tests,
eliminating this threat.
Mono-operation bias: Each aspect of the study
could have been measured in more than one way.
For example, upper body strength could have
been measured in more ways then just barbell
bench press. Incline BP, dumbell bench press,
machine bench press are all other ways to
measure upper body strength, but only one was
Mono-method bias: Change in strength could
be measured in different ways. For example,
bench press mainly uses chest, triceps, and
shoulder muscles, but bicep curls use
different muscles, and they are obviously part
of the upper body. However, bench press
uses the most upper body muscles out of any
upper body lift, making it seem like the best
demonstration of strength.
Interaction of Different Treatments: There
aren’t outside factors that would have had
any effect on the results in the time this
experiment was conducted.
Interaction of testing and treatment: All the
subjects were already experienced in
resistance training, so one additional trial
would not likely implicitly improve
Confounding constructs and levels: This is
probably the biggest threat to the entire
experiment. All subjects varied in size, but
all were given the same dose of caffeine.
There could be differences in results if more
trials were given with varying amounts of
Or, caffeine could have been dosed
proportionately to body weight.

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