Often this severe fluid restriction is combined with reduced food intake and heavy exercise in the days before a competitive event, in hopes of maximising weight loss.

Once weight is 'made', the rowers take in large quantities of fluid just before the race in an attempt to restore body fluids to normal levels, but the effect of this overall strategy on performance has been unclear - until now. New research from Victoria University and Ballarat University College in Australia suggests that the fluid-restriction protocol can harm performance by about 5 per cent, mainly because it's impossible to restore all the blood volume drained away during the dehydrating pre-race regime.

Eight male lightweight rowers with international competitive experience participated in the Australian study. Over a period of 24 hours, the rowers lost about 5 per cent of their body weight by restricting liquids and foods and by exercising lightly in 'sweat gear' (clothing with waterproof qualities) to maximise sweat losses. After losing weight the rowers tried to rehydrate themselves by drinking 250 ml (eight ounces) of water every 15 minutes over a 90-minute time period, which is similar to the quick water-intake strategy often used by rowers. 1.5 litres (49 ounces) of water were consumed in all. Shortly thereafter, an exercise trial, designed to simulate a 2000-metre race, was performed on a Gjessing rowing ergometer.

After the 24-hour dehydration period, body weight dropped by an average of almost four kilograms (8.5 pounds), or about 5.2 per cent, and total blood volume plummeted by almost 13 per cent. Only about half (6 per cent) of the lost blood plasma was restored during the water-intake period following dehydration, and the result was a slowing of 2000-metre race time from 7.02 minutes (the time the athletes could achieve when they hadn't utilised the 'make-weight' dehydration regime) to 7.38 minutes (a 5 per cent loss of performance). In a 2000metre race, this represents about a 15-metre per minute loss of speed.

Since the 'dehydration-rehydration' scheme employed by the Australian athletes is one commonly used by competitive rowers, it's clear that another weight-loss strategy should be sought. The basic problem with dehydrating oneself before competition is that blood-volume restoration (following the dehydration) can be a very slow process - so slow that it may not be completed in time for a race. When blood volume is depressed, the movement of oxygen to muscles is limited, and exercise heart rates tend to be unusually high. The answer is not to swill vast amounts of water following dehydration; such intakes will simply lead to avid urination, not better blood volume. It's far more sensible for athletes to make weight by using a long-range, carefully planned programme which combines reasonable eating with the right amount of exercise. (Medicine and Science in Sports and Exercise, 1993).