Article Review: Caffeine intake (200mg) and effect on muscular strength & endurance
Article: Beck, T.W., Housh, T.J., Schmidt, R.J., Johnson, G.O., Housh, D.J., Coburn, J.W. and Malek, M.H., 2006. The acute effects of a caffeine-containing supplement on strength, muscular endurance, and anaerobic capabilities. The Journal of Strength & Conditioning Research, 20(3), pp.506-510.
Design: This was a randomized, double-blinded, placebo- controlled, parallel design of 37 well trained men, ingesting either 2.4mg/kg (around 200mg on average) dose of caffeine or a placebo. They tested anaerobic sprint power, maximal strength in bench press and leg extension and muscle endurance in the same 2 lifts.
Findings: They only found an increase in maximal strength in bench press, every other exercise had no significant improvement.
Limitations: This one is hard as you have to take in to account a few factors. We do not know the exposure these men have had to caffeine (if they are habitual users or not), their diet or sleep were not controlled between test days. The level of strength is also a factor, whereby the higher the strength the less significant improvement they can make (Its a lot easier to go from 40 to 45kg than 140 to 145kg). The muscular endurance test was also performed the same day, and was at 80% of their 1RM (Quite a higher workload).
My thoughts: I chose this study as it related most to the normal dosage you'd find in most pre-workouts, where as most studies used 6mg/kg. The study showed no real improvement of 1RM, however an increase in only upper body is interesting, there may be a differing effect in upper vs lower body. The no change in endurance surprised me but upon reading the workload of 80%1RM doesn't leave much room to improve, that is quite a heavy working set, especially after maximal training 2 days prior. All in all, 200mg dose not appear very effective to influence muscular strength, however other studies utilising higher dosages have shown great improvements. I would hazard a guess that this dosage is not high enough to have an ergogenic effect and needs to be closer to 6mg/kg to cause an improvement.