The stimulant drug ephedrine, either alone or in combination with caffeine, leads to highly significant performance improvements that would take weeks to acquire through training alone.

That is the clear conclusion of a Canadian military study, which is part of a series set up to clarify the effects of caffeine and ephedrine on physical performance across a broad range of exercsie intensities.

A group of 13 healthy active male subjects, all accustomed to resistance training exercises, performed a weight training circuit consisting of three supersets of leg and bench press exercises on four separate occasions, 90 minutes after ingesting one (in turn) of the following in a capsule formulation:

• Caffeine (C) – 4mg per kg of body weight;
• Ephedrine (E) – 0.8mg/kg body weight of ephedrine hydrochloride;
• Caffeine and ephedrine combined (C+E);
• Placebo (P) – 300mg of dietary fibre.

The researchers’ theory was that the caffeine-ephedrine combination (C+E) would improve muscular endurance and, further, that the magnitude of the improvement would be greater than could be achieved by ingesting either drug alone.

They were not disappointed in the first supposition: the mean number of repetitions for the first set of leg press exercises was significantly higher for the trials involving ephedrine than for the caffeine-only and placebo trials – 18.5 reps for C+E, 16.3 for E, 13.6 for C and just 12.5 for P. Results for the bench press followed the same pattern, although the improvements were of a lesser magnitude, ranging from 14.3 reps for C+E to 12.3 reps for P.

However, these apparent ergogenic effects were not sustained for the second and third set of exercises. Furthermore, there was no significant difference between the effects of ephedrine alone and ephedrine-plus-caffeine, suggesting that there is no synergistic (additive) interaction between the two drugs.

The researchers comment: ‘The magnitude of the effect [of C+E] during that first set is highly significant for this type of exercise, considering that it was induced only 90 minutes after ingesting the C+E. The 48% improvement in the leg exercise and the 16% improvement in bench-press performance would otherwise be expected to require from four to approximately 12 weeks of strength training.’

They believe the most plausible explanation for the observed effects is that the increase in muscular endurance with C+E was mediated by an increase in central nervous system stimulation, which may have delayed or masked the perception of fatigue.

The fact that the improvement occurred only in the first set of exercises may, they believe, have been related to the short rest interval of just two minutes between sets. ‘It is tempting to speculate that a more prolonged recovery interval between the [sets] may have facilitated a continuing ergogenic effect of the ephedrine treatments in subsequent sets.’

The researchers hasten to point out that their results should not be taken as advocacy for athletes to use ephedrine as an ergogenic aid. Even discounting the fact that such drugs are banned by the International Olympic Committee, their use poses serious health risks.

For example, systolic blood pressure before exercise was significantly increased with both ephedrine treatment trials by comparison with the other two.

‘We acknowledge that there are serious risks…’, conclude the researchers. ‘However, the fact remains that huge numbers of consumers are estimated to be purchasing and ingesting [ephedrine-containing] products, specifically with a view to enhancing physical performance. This study provides some empirical evidence about the efficacy of C+E and…will perhaps lead to a greater understanding as to why such products are used, in spite of the potential health risks.’

Med Sci Sports Exerc, vol 35, no 6, pp987-994