Attenuation Of Exertional Muscle Damage With A Nutritional Supplement

Abstract

Previous research suggests that glutamine (GLN) administration either during or following strenuous exercise modulates post-exercise inflammatory responses and may facilitate recovery. PURPOSE: This study studied the effects of GLN added to a beverage containing a carbohydrate (CHO) and an essential amino acid (EAA) mixture consumed during and after exercise on markers of EMD and performance in subjects following a strenuous physical training event. METHODS: Male subjects (n = 33; mean age of 24 years ± 1) completed this blinded-crossover study. Subjects were randomized to ingest either a placebo or treatment beverage during and after two identical events (modified physical fitness test), with the alternate beverage provided at the second event. Beverages were matched for CHO and EAA content (42 grams of CHO, 6 grams of EAA per liter) providing 192 calories. The GLN containing (4 grams) treatment beverage provided 208 calories per liter. RESULTS: No significant differences were noted (p ≤ 0.05) between groups with respect to muscle damage or inflammation, to include changes in creatine kinase, lactate dehydrogenase, white blood cell counts, C-reactive protein and select pro- and anti-inflammatory cytokines, as measured at baseline and after exercise. Creatine kinase, the primary variable of interest, increased after the training event in both groups indicating muscle damage had occurred. The treatment beverage did not significantly attenuate the response (p = 0.28). Plasma GLN levels remained relatively unchanged between placebo and treatment conditions, with both beverages blunting post-exercise induced decreases in GLN levels. Physical performance measures and pain scores were not significantly affected by the addition of GLN. CONCLUSIONS: Our findings suggest that the addition of GLN to a CHO/EAA beverage provided during and after exercise does not confer any significant benefit over a CHO/EAA beverage alone. The intervention failed to alter circulating GLN levels or measurably affect markers of EMD and the inflammatory response, and did not improve physical performance.