Effect of Intermittent Fasting for Five Consecutive Days on Exercise-Induced Muscle Damage in Humans

Abstract

Animal studies have supported the immunological benefits of caloric restriction, but clinical trials of such diets in humans are scarce. Regardless, several studies in humans have shown differences in fasting and postprandial levels of inflammatory markers, which may be relevant to studies of exercise-induced muscle damage. PURPOSE: This preliminary investigation compared the signs and symptoms of exercise-induced muscle damage between participants who completed their laboratory sessions in a fasting or postprandial state. METHODS: Upper-body untrained participants (N = 29, 22 yrs old (SD = 3.34), 41.4% women) visited the lab in p.m. hours for five consecutive days after having either fasted for the previous 8 hours or eaten only a supplied meal within the previous 4-5 hours. (The supplied meal consisted of 810-860c, 250-320 fat c, 28-35g fat, 10-13g sat fat, 40-45mg cholesterol, 6-7g fiber, 101-104g carbohydrate, and 32-34g protein.) Measures of muscle pain, resting elbow extension, upper arm girth, isometric strength, myoglobin (Mb), total nitric oxide (NO), interleukin 1beta (IL1b), and tumor necrosis factor (TNFalpha) were collected before and after eccentric contractions of the non-dominant elbow flexors were completed. RESULTS: The loss of elbow extension peaked significantly more slowly for the fasting group than the postprandial group (F3, 72 = 3.01, p <.05, eta2 =.10), but the groups did not change differently across time for any other outcome measures. However, significantly lower strength (53.4+3.7 vs. 73.1+5.2% body weight, p <.05), higher NO (27.06+1.37 vs. 20.73+1.88 μmole/L, p <.05), and lower TNFalpha (2.18+0.18 vs. 3.89+0.25 pg/mL, p <.05), were detected in the fasting group than the postprandial group regardless of time. CONCLUSIONS: These results suggest that eating behavior within 8 hours of lab visits may be a meaningful source of variability in human exercise-induced muscle damage protocols, but intermittent fasting does not generally inhibit the signs and symptoms of exercise-induced muscle damage. Additional research on potential protective effects of caloric restriction (i.e., short-term fasting) on the exercise-induced muscle damage model in humans is warranted. Supported by NIAMS (KO1 AR050146) to E. A. Dannecker, PhD, ATC.