Creatine and caffeine are among the most popular ergogenic aids used by exercising
individuals. Creatine supplementation during resistance training has been shown to increase
muscle mass and muscle performance (i.e. strength, endurance), possibly by influencing
high-energy phosphate metabolism, muscle protein kinetics, and inflammation. Caffeine
ingestion has been shown to increase muscle performance, primarily by influencing adenosine
receptor activity, muscle protein kinetics, phosphodiesterase, and excitation-coupling.
Previous research investigating the combined effects of creatine and caffeine has produced
mixed results, with some showing a beneficial effect on short-term anaerobic type activities,
while other report no effect. Despite the potential beneficial effects of creatine and
caffeine separately, no study has compared the combined effects of creatine and caffeine
during resistance training. Therefore, the purpose of this thesis is to determine the effects
of creatine and caffeine co-supplementation during resistance training on muscle mass and
muscle performance in trained young adults.
The study will be a double-blind, repeated measures design. In order to minimize group
differences, participants will be matched according to age and weight and be randomized on a
1:1:1:1 basis to one of four groups: Creatine + Caffeine (CR-CAF; 0.1 g/kg of creatine
monohydrate powder + 3 mg/kg of caffeine [micronized powder]); Creatine (CR; 0.1 g/kg of
creatine monohydrate powder + 3 mg/kg of caffeine placebo [micronized cellulose powder]),
Caffeine (CAF; 3 mg/kg of caffeine + 0.1 g/kg of creatine monohydrate placebo [maltodextrin])
or placebo (PLA; 0.1g/kg creatine monohydrate placebo + 3 mg/kg of caffeine placebo). An
individual, blinded to supplement and group allocation, will be responsible for the
preparation of study kits. Each study kit will contain the participants supplement for the
duration of the study, detailed supplementation instructions, measuring spoons,
supplementation compliance log, daily caffeine consumption log and a resistance training log.
Supplement powders will be similar in energy content, color, taste, texture, and appearance.
The creatine dosage of 0.1 g/kg has previously been shown to be effective for increasing
muscle mass and muscle performance. The caffeine dosage of 3 mg/kg has been shown to increase
muscle performance. Participants will be instructed to refrain from additional caffeine
sources ≥ 3 hour prior to consuming their supplement so that a valid estimate regarding the
effects of caffeine supplementation on muscle can be made. On training days, participants
will mix their supplement powder in water and consume the solution 60 minutes prior to
exercise. Sixty minutes was chosen because this is the approximate time it takes for peak
plasma caffeine concentrations to occur after caffeine ingestion and pre-exercise creatine
supplementation has a beneficial effect on muscle performance.
Participants will follow the same periodized, resistance training program for 6 weeks. The
program will consist of three sets of 6, 8, 10 repetitions to muscle fatigue in order.
Resistance training will start on the first day of supplementation and will consist of a
split routine involving whole body musculature. Day 1 will involve chest and biceps
musculature and include the following exercises in order: machine-based chest press, free
weight incline bench press or dumbbell press, free-weight flat dumbbell press, machine-based
pec-dec, free-weight standing barbell curl, free-weight alternate arm dumbbell curl and
machine-based preacher curl. Day 2 will involve leg and core musculature and include the
following exercises in order: free-weight squat, machine-based leg press, machine-based leg
extension, machine-based leg curl, machine-based calf raise, and machine-based weighted
abdominal crunches. Day 3 will serve as a rest day from training. Day 4 will involve back and
triceps musculature and include the following exercises in order: body weight or
weight-assisted chin-ups, machine-based seated row, machine-based lat pull-down, free-weight
alternate dumb-bell row, free-weight close-grip bench press, machine-based cable triceps bar
extension, and machine-based cable triceps rope extension. Day 5 will involve shoulder and
core musculature and include the following exercises in order: free-weight dumbbell press,
free-weight upright row, free-weight shrugs, free-weight or machine based lateral deltoid
flys, free weight or machine-based rear deltoid flys and machine-based weighted abdominal
crunches. Day 6 will serve as a rest day from training. This cycle will be repeated for 6
weeks. Participants will maintain training logs to ensure adherence and compliance to the
study and to determine total training volume (load x repetitions x sets).
