The present study investigated the effect of carbohydrate-only or carbohydrate-plus protein supplementation on endurance capacity and muscle damage.

It included ten recreationally active male runners (VO2 max: 53.61 ± 3.86 ml/kg•min) who completed the run-to-exhaustion test three times with different intakes of intervention drinks. A 7-day wash-out period existed between the tests. Each test began with 60 minutes of running at 70% VO2 max (phase 1), followed by an endurance capacity test: time-to-exhaustion running at 80% VO2 max (phase 2). Participants were randomized to ingest either 1) 0.4 g/kg BM carbohydrate before phase 1 and before phase 2 (CHO+CHO), 2) 0.4 g/kg BM protein before phase 1, and 0.4 g/kg BM carbohydrate before phase 2 (PRO+CHO), or 3) 0.4 g/kg BM carbohydrate before phase 1 and 0.4 g/kg BM protein before phase 2 (CHO+PRO). The participants ingested carbohydrate (CHO) 1.2 g/kg BM during phase 1, and the study obtained blood samples before, immediately, and 24 h after exercise for measurements of alanine aminotransferase (ALT), aspartate aminotransferase (AST), creatine kinase (CK), and myoglobin (MB).

The study found-

• No significant difference in time to exhaustion between the three supplement strategies. 
• Significantly lower ALT and AST in PRO+CHO than in CHO+CHO 24 h after exercise. 
• Significantly lower MB in PRO+CHO and CHO+PRO than in CHO+CHO 24 h after exercise. 
• Less increase in CK in PRO+CHO compared to CHO+CHO 24 h after exercise.

This study shows that Carbohydrate and protein supplement strategies reduce muscle damage generated by endurance exercise; however, they do not improve endurance exercise capacity.

Liang Y, Chen Y, Yang F, Jensen J, Gao R, Yi L, Qiu J. Effects of carbohydrate and protein supplement strategies on endurance capacity and muscle damage of endurance runners: A double-blind, controlled crossover trial. Journal of the International Society of Sports Nutrition. 2022;19(1):623-637. DOI: 10.1080/15502783.2022.2131460