UTILIZATION OF AN HYPERBOLIC MODEL FOR THE DETERMINATION OF THE CRITICAL LOAD IN SWIMMING RATS.
L Marangon, Cláudio Alexandre Gobatto, María Alice Rostom de Mello, Eduardo Kokubun · Medicine & Science in Sports & Exercise · 2002
Since there are obvious limitations in the investigations with human subjects, animal models became important for a deeper insight into the mechanisms involved in the physiological responses to physical exercise. However, the control of exercise intensity is not easily determined in animals. Maximal lactate steady state (MLSS) in rats during swimming exercise was previously determined by our group to occur when the animals supported a 6% body weight overload at a 5.5mM blood lactate concentration. In evaluations with human subjects, it was suggested the use of non invasive tests for the determination of “critical power (CP)” and “anaerobic work capacity (AWC)” which relates the exercise intensity (L) to the exhaustion time (tlim) by means of the “rectangular hyperbolic” function (P=CP+AWC/tlim). Previous studies established that CP is correlated to the MLSS intensity and other indicators of the aerobic capacity. PURPOSE: The present study was designed to test the validity of this model in rats submitted to swimming exercise. METHODS: Twenty and tree adult male Wistar rats adapted to water for 6 days were used. Each rat was submitted to 4 swimming tests, performed each other day, supporting loads (L) of 9, 11, 13 and 15% of body weight (bw) continuously until exhaustion (tlim in s). RESULTS: The results indicated that CP (here expressed as critical load-CL, in % bw) was 7.48 ± 0.25 and AWC (%bw per s) was 518.81 ± 22.59. Mean regression coefficient (r2) obtained by the Load-1/time model was 0.92 ± 0.01. Even more, rats submitted to a 20 min swimming session supporting the load corresponding to the CL showed blood lactate stabilization at 5.82 ± 0.37mM CONCLUSION: There data show that the model applied to the CL and AWC determination was well adjusted to this exercise protocol and the results obtained were similar to those reported for human subjects. Supported by FAPESP and CNPq