We all throw back our pre workouts loaded with caffeine day-in-day-out on the assumption that it will help us lift more. So it’s nice to see studies surface from time to time which confirm some of these long-held beliefs. The latest one appears in the May 2015 issue of the Journal of Sports Medicine & Physical Fitness. While it was a relatively simple study, it is highly practical in terms of its relation to the average gym junkie.
Researchers from Brasil took a group of 14 young men with an average age of 21 years and weight of 77.6kg who had a recent history of resistance training. Using a double-blind, counterbalanced, crossover design, subjects were given a dose of caffeine equivalent to 5mg per kilogram bodyweight. If we take an individual who weighs 78kg, that equates to a dose of 390mg, which is a tad above even the strongly-dosed pre workouts, which usually sit somewhere between 300-350mg.
Each subject performed 3 sets of bench press and 3 sets of leg press exercises to failure after taking the caffeine and placebo. As expected, taking caffeine prior to the workout enabled the subjects to perform a significantly higher number of reps. For bench press, the average number of reps across the 3 sets was 26.86 when taking placebo and 30 when taking caffeine. As for leg press, average reps when taking placebo were 40, while caffeine resulted in an average of 47.64 reps.
Aside from measuring the effect of caffeine on reps to failure, the researchers also assessed the effect of caffeine on the subjects readiness for physical and mental effort prior to each test. One of the key mechanisms by which caffeine is thought to improve performance is by decreasing perceived effort and/or pain. The authors found that only the subjects’ mental readiness to invest effort improved significantly. Physical readiness to invest effort did not change significantly.
Interestingly, ratings of perceived exertion were not different between treatments and neither was heart rate. So the mechanism underlying improved performance didn’t turn out exactly as expected, but the main point was a big dose (i.e. >300mg) of caffeine boosted reps to failure, which is all the average Joe really cares about. So what are you waiting for? Get yourself some more pre workout!
DaSilva VL, et al. Effects of acute caffeine ingestion on resistance training performance and perceptual responses during repeated sets to failure. Journal of Sports Medicine and Physical Fitness. 2015;55(5):383-389.