Effect of high and low carbohydrate meals on sustained Maximum Voluntary Contraction (MVC) after prolonged exercise

Abstract

Fatigue is a natural physiological phenomenon where the body’s capability to do work is reduced, and in general carbohydrate (CHO) depletion has been attributed to the aetiology of this condition. However, its composition in iso-caloric meals has never been investigated on capacity of sustained force production following a prolonged exercise. Aim: To investigate the effects of high and low CHO meals on sustained maximal voluntary contraction (MVC) capability after a 90-minute run. Methods: Ten (n=10) moderately trained runners (age: 25±3.7 years, and VO2max: 51.42±4.78 ml/min/kg) were prescribed, in a cross-over, randomised, and double blind design, either one of these iso-caloric meals: high CHO meal (1.5 g/kg body weight), or a low CHO meal (0.8 g/kg body weight) prior to the 90-minute run at 65% of VO2max. A 90-second sustained MVC was measured before and after the run (represented at 30, 60, and 90 seconds respectively). Results: MVC dropped significantly (p<0.01) after the prolonged running exercise in both groups. The difference in the sustained MVC was significant between the two groups at all time points (p<0.01). Conclusion: While both groups completed the 90-minute running task successfully, the high CHO meal allowed a higher sustained force production (MVC) post-exercise, suggesting physiological changes that allows better neuromuscular functions. Theoretically, several factors could be attributed to this phenomenon, such as preservation of fuel source, and/or alteration of brain neurotransmitter concentrations that affect neural drive.