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).
