Sport and exercise: old wives’ tales

In an era when sport has a remarkable resource of science and medicine applied to it at an ever-increasing expense, it is remarkable that the evidence base for some of the widely accepted training practices is seriously lacking. In an excellent article published in the British Medical Journal recently, Carl Heneghan and colleagues from Oxford, UK,¹ looked at six claims made by sports and exercise products to examine the evidence underpinning the claims.

1. The colour of urine accurately reflects hydration. The evidence is that most people cannot reliably assess urine colour and there are no good studies comparing urine colour with other measures of hydration such as thirst and body mass.

2. You should drink before you feel thirsty. Drinking ahead of thirst may worsen performance in endurance exercise and carries a rare but serious risk of hyponatraemia. Elite endurance athletes perform best when they drink to thirst and some studies suggest exercise-induced dehydration can improve performance.

3. Energy drinks with caffeine improve sports performance. Limited, low-quality evidence supports the use of energy drinks containing caffeine, taurine or guarana to improve endurance in moderate-intensity activity of around 60 minutes. No studies compare the effectiveness of these products with ingesting caffeine alone and there are important concerns regarding harms.

4. Carbohydrate and protein combinations improve post-workout performance and recovery. There is a lack of evidence to support combined carbohydrate and protein supplements after exercise to improve recovery and reduce muscle breakdown. The results of studies of supplements containing a variety of carbohydrate to protein ratios show inconsistent and generally small benefits in some measures of sports performance, but generally do not show benefits over and above a balanced and nutritious diet.

5. Branched chain amino-acids improve performance or recovery after exercise. High-quality evidence is lacking that branched chain amino acids enhance performance or recovery in competitive settings. There is limited evidence to suggest that muscle soreness and recovery may be reduced and that longer-term supplementation may increase some strength and endurance measures. High-quality large randomised trials evaluating the effect on outcomes that are directly relevant to athletes, such as run times or maximal weight lifts in the competitive setting.

6. Compression garments improve performance or enhance recovery. There is no consistent evidence that compression garments improve sporting performance. Muscle soreness seems to be reduced if garments are worn for 24 hours after exercise, but objective measures of recovery are less consistent, and compression garments seem to work no better than other recovery strategies such as low grade exercise or contrast bathing. Potential adverse effects of these garments may include increased skin temperature, decreased thermoregulation and reduced range of motion. 

Larger studies in individual sports and research are available generalised to either highly trained athletes or the general population, with outcomes related to sports performance, and examination of adverse effects and acceptability of compression garments.

Reference

1. Mythbusting sports and exercise products. Heneghan C, Gill, P, O’Neil B et al. BMJ 2012; 345: e4848