Muscle physiology and performance during intensified cycle training: Impact of carbohydrate-protein supplementation

Previous studies show that carbohydrate-protein (CP) ingestion can enhance short-term recovery following exercise, thereby benefiting subsequent exercise performance and compounding physiological parameters, when compared to carbohydrate (CHO) alone. Less is known about the influence that CP supplementation may have over a long-term intervention (several days/weeks). The purpose of this investigation was to determine whether CP supplementation was effective in improving tolerance to a period of intensified training (IT), compared to CHO. Additionally, the influence of CP on recovery/ adaptation to a period of IT followed by a period of reduced volume training (RVT) was examined. Eight endurance-trained cyclists (age: 24.9±7.3 years, weight: 71.8±11.5 kg, VO2max: 63.4±7.9 ml/kg/min) completed two independent training phases, each with a 10 day period of IT, followed by a 10 day period of RVT. CHO supplementation was provided during (45 g/hr) and immediately following (1.2 g/kgBW) all exercise sessions in one phase, whereas CP treatments was provided throughout the other phase (45gCHO/hr + 15gPRO/hr during; 1.2gCHO/kgBW + 0.3gPRO/kgBW post). The impact of IT on cycling performance was ‘unclear’ (60 ± 210 sec), with an ‘unclear’ treatment effect. CP ‘likely’ preserved whole muscle function throughout IT, compared to CHO. Whole muscle size was ‘possibly’ maintained throughout IT with CP, compared to CHO. While CHO ‘likely’ increased MHC IIa CSA following IT, CP ‘likely’ increased MHC IIa CSA following RVT, compared to their respective treatments. Throughout a period of IT, CP supplementation may preserve whole muscle size and function, compared to CHO. However, CP minimally affected changes in cycling performance and muscle fiber size following IT