Influence of protein- versus carbohydrate-enriched feedings on physiological responses during an ultraendurance...

This study investigated effects of a high protein (PROT) versus a high carbohydrate (CHO) diet on performance and physiological responses during an ultraendurance climbing race at moderate altitude. On two different periods, in a randomised crossover design, ten climbers (30.0+/-0.9 years) participated in the race (duration 29 h approximately, energy expenditure 43.6+/-1.2 MJ.day (-1)) and were fed either with the PROT (30% protein content) or the CHO diet (68% carbohydrate) each providing 16.74 MJ. Mental performance was assessed by the Stroop test and we estimated maximal voluntary strength of quadriceps muscle. We quantified metabolic and hormonal circulating concentrations. Mental performance was unaffected after the two races, while muscular performance and body weight were decreased (both p<0.01) with no diet effects. Decreases were measured for IGF-I concentration and its binding protein IGFBP-3 (p<0.001), and increases for cortisol and norepinephrine (p<0.01) with no diet effects. Glucose concentration decreased (p<0.05) without diet effects, while amino acids (leucine, isoleucine, valine, and tyrosine) decreased in CHO group (p<0.001). Leptin concentration decreased (p<0.001) without diet effects, whereas total ghrelin increased in CHO group (p<0.01). Our results showed that a high PROT or high CHO intake during physical exertion at moderate altitude maintained mental performance, but did not limit muscle force reduction and body weight loss. There was decreased glucose availability, and hormonal responses indicated both catabolism and extreme energy deficiency induced by exercise with opposite responses of ghrelin and leptin. The ghrelin response was additionally indicative of macronutrient intake during the race.