Physical performance of exercising young rats fed hydrolysed whey protein at a sub-optimal level

Exhaustion time, serum lactate, serum glucose, albumin and total proteins were determined in exercising young rats as means to assess the physiological effect of consuming a diet based on partly hydrolysed milk whey protein in comparison to the intact protein, fed at a sub-optimal protein level. A medium degree-of-hydrolysis (DH) whey protein hydrolysate (H), fed at 12% protein, have been examined. The rats were grouped according to the level of activity for sedentary (S), trained (T) and exercised to exhaustion (E) and to the type of protein in the diet: whey-protein isolate (I) or its partial hydrolysate (H). After feeding the diets under sedentary conditions for 2 weeks, the animals underwent physical training on the treadmill for 8 days, followed by an exhaustion test. Time to exhaustion and blood lactate were recorded immediately after exhaustion. Serum glucose, albumin and total proteins, and gastrocnemius protein were determined at 48 h post-exhaustion. The animals consuming the hydrolysed protein endured longer times of activity, in comparison to those consuming the isolate (156±18 vs. 60±13 min). Blood lactate was significantly (P<0.0001P<0.0001) lower in all of the hydrolysate-fed groups as compared to the rats fed the whole protein. Analogously, serum albumin levels were higher in all H groups, as compared to the I groups (P<0.001P<0.001), while the levels of total serum protein were significantly higher for the trained and exhausted groups (P<0.0025P<0.0025). No differences in muscle protein content and glycemic levels for any of the groups were observed. It can be concluded that a dietary protein, fed at a sub-optimal level for growth in the form of a hydrolysate with medium DH may result in augmented physical performance of the exercising rat, while no adverse effects are observable. Alternatively, these observations suggest that consumption of a protein in the hydrolysed form may increase its efficiency in terms of physical performance.