A Dutch-Danish team conducted a randomised, double-blind, placebo-controlled crossover study involving nine patients with McArdle disease, or type V glycogenosis:
- ingestion, 10 minutes before the start of a 60-minute submaximal exercise test on an ergocycle, of a sweetened sports drink (in this case Faxe Kondi©) did result in a significant improvement in exercise tolerance, as measured by a smaller increase in heart rate and perceived exertion (Borg scale), compared with ingestion of a zero-calorie version of the same drink (placebo);
- heart rate and perceived exertion, on the other hand, did not differ between the two drinks ingested repeatedly during exercise, after the second wind phenomenon.
Another team confirmed, in eight Spanish patients with McArdle disease, the benefits of adding sugar before exercise. A dose of 150g of glucose-fructose was found to be more beneficial than 75g in terms of exercise tolerance and physical performance. A dose-effect relationship was also demonstrated in vitro, on mouse myotubes modelled on the disease.
These results could contribute to finding the right balance between the muscular benefits of carbohydrate intake and the risks of excess weight and insulin resistance.
