In a recently published article by Erica Goldstein presented in the May edition of the Journal of the International society of sports nutrition found that caffeine increases the strength in women who regularly exercise strength.
In a randomized study, 15 women were given either 6mg of caffeine per kg body weight or placebo for 7 days. After an hour the women were tested in an RPM bench press and how many repetitions they then failed in 60% of 1 RPM (equivalent to 20 to 25 repetitions).
There was a statistically significant increase in the maximum power of those before the test had taken caffeine. The interesting part of this study is that it stands in contrast to the current position of the ISSN as in January concluded that the effect of caffeine on maximum strength was ambiguous, but that the positive effect seemed to turn out in several repetitions.
Source:
1. J Int Soc Sports Nutr. 2010 May 14; 7 (1): 18 Caffeine enhancer upper body strength in resistance-trained women.Goldstein ER, Jacobs PL, Whitehurst M, Penhollow T, Antonio J. ( abstract )
2. J Int Soc Sports Nutr. 2010 in January 1927, 7 (1): 5 International society of sports nutrition position stand: Caffeine and performance. Goldstein IS, Ziegenfuss T, Kalman D, Kreider R, Campbell B, Wilborn C, Taylor L, Willoughby D, Stout J, Graves BS, Wildman R, Ivy JL, Spano M, Smith AE, Antonio J