Abstract

PURPOSE: We aimed to examine the effect of running speed on metabolic responses associated with maximal lactate steady state (MLSS) in rats during forced running wheel (FRW) exercise. METHODS: Forty male adult Wistar rats were divided into seven groups. The blood lactate threshold and peak running speed were determined for an incremental power test group. Five groups participated in constant power tests at intensities 10, 13, 14.5, 16, and 17.5 m/min to determine MLSS and a non-exercise group was chosen as the control. Animals were euthanized immediately after constant power tests and their corticosterone, non-esterified fatty acid (NEFA), blood glucose, and creatine kinase (CK) levels analyzed. The differences among groups were identified by one-way analysis of variance (p < 0.05). RESULTS: Blood lactate threshold corresponded a running intensity of 15 m/min, while MLSS was determined to be 16 m/min. Serum corticosterone concentrations were significantly higher in 14.5, 16, and 17.5 m/min groups (298.8+/-62, 338.3+/-65, and 354+/-26 nM, respectively) as compared to that in the control group (210.6+/-16 nM). Concentrations of NEFA observed in groups 13, 14.5, 16, and 17.5 m/min (662.8+/-24, 702.35+/-69, 718.4+/-34, and 752.8+/-77 muM, respectively) were significantly higher than those in 10 m/min and control groups (511.1+/-53 and 412.1+/-56 muM, respectively). The serum CK concentration recorded for group 17.5 m/min (372.4+/-56 U/L) was higher than those recorded for other groups. CONCLUSION: The speed above 16 m/min on FRW resulted in increased physiological demands and muscle damage in untrained healthy Wistar rats.