Science of Sport: Modafinil - Banned drug works as ergogenic aid

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Traces of the banned stimulant drug modafinil have been found in the urine of a number of world-class athletes, including US sprinter Kelli White. But until now there has been no scientific evidence that modafinil, prescribed for sleep disorders, such as narcolepsy, is at all effective as an ergogenic aid.

Powerful evidence in favour of modafinil has now emerged from Canadian research, whose underlying agenda was to consider modafinil as a tool for use during military combat operations.

The study, involving 15 healthy men familiar with exhaustive exercise, was set up to investigate the effect of acute ingestion of modafinil on time to exhaustion during high-intensity exercise.

The subjects exercised on cycle ergometers for five minutes at 50% VO2max, then at 85% VO2max to exhaustion on three separate occasions:

• Control condition (C) – no supplement;
• Placebo condition (P) – dietary fibre ingested in the form of opaque gelatin capsules, one hour before a standardised light breakfast and three hours before the exercise test;
• Treatment condition – modafinil (M) in a dosage of 4mg per kg of body weight, given in the same form and according to the same protocol as the placebo. Key findings were as follows:
• Modafinil ingestion was associated with a significant 22% increase in time to exhaustion compared with the control and placebo conditions, making it comparable in efficacy to caffeine. However, the researchers point out, ‘as [modafinil] has a half life of 10-13 hours, twice that of caffeine, its use could possibly result in a more sustained efficacy than that reported for caffeine’;
• Modafinil led to a slight but significant increase in VO2 compared with control and placebo – but only during the last 30 seconds of exercise, when subjects were close to exhaustion;
• Heart rates increased with time in all the conditions, but were highest of all with modafinil;
• Modafinil was associated with significantly lower ratings of perceived exertion (RPE) than control or placebo, but only after 10 minutes of exercise at 85% VO2max. Subjective RPE values were similar at exhaustion, regardless of treatment.

‘The results of this study are particularly timely,’ observe the researchers, ‘in light of recent controversies around world-class athletes who had traces of modafinil in their urine. Until this study, there was no published evidence to document that modafinil can enhance physical performance. The current study is the first to provide evidence that modafinil can indeed enhance physical performance of a nature that would likely be advantageous during competitive sports where exercise to exhaustion is commonplace.’

The fact that modafinil does not appear to disrupt sleep, is an effective cognitive enhancer and may shorten the amount of recovery sleep needed after sleep deprivation suggests it could also be part of an effective strategy to combat jet lag in military personnel and athletes alike.

And unlike with caffeine, high doses of which are associated with anxiety, the subjects in this study did not report any subjective differences associated with modafinil use.

The study was not designed to establish precisely how modafinil – which is, of course, still banned for competitive athletes – works. The researchers speculate that it operates by delaying the perception of fatigue, thereby allowing people to work for longer.

I>Med Sci Sports Exerc, vol 36, no 6, pp1078-1082, 2004

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