Effects of theophylline and theobromine on exercise performance and implications for competition sport: A systematic review.

A systematic review was undertaken to evaluate studies on the effects of theophylline and theobromine on exercise performance in normal (healthy) subjects. Theophylline was found to have been studied on eight occasions and theobromine on one, the number of subjects per study ranging from seven to 15. In two exercise investigations, theophylline was superior to placebo at a p < 0.05 level and no different in four including one that was conducted in artificial hypoxia. In a treadmill time trial over 3 km, theobromine was superior to placebo and equal to caffeine, at the <0.05 level. In strength studies, theophylline increased wrist strength in one and showed a slight but not statistically significant increase in limb strength in four of the seven subjects in the other. Theophylline caused adverse effects in six participants. There were no adverse effects in the theobromine investigation. Although the studies showed contradicting results and/or insufficient data to draw solid conclusions, it appears both drugs have potential to enhance performance and could be considered for inclusion on the WADA banned list.