Double Bouts Test for Non-Exhaustive Aerobic Evaluation of Running Rats

Abstract

For obvious reasons, there are a great number of studies involving exercise conducted in laboratory animals, manly rats. Therefore, it is necessary to develop methods for physical evaluation of exercised rats. PURPOSE: The aim of the present study was to describe a double bouts exercise method for non-exhaustive aerobic conditioning determination in running rats (critical velocity), based on the protocol originally described by Chassain (Science & Sports, v.1, p.41–8, 1986), for human subjects. METHODS: Thirteen male Wistar rats (120 days old) were selected and adapted to treadmill running for three weeks. The rats were submitted to four running tests at different velocities (10, 15, 20 and 25m.min−1) at random, with intervals of 48 hours among them. The rats run two efforts of 5 minutes each at same intensity, with a 2 minutes interval between the two exercise bouts. Blood samples were collected from the animals at the end of each bout for lactate determination. For each intensity, a delta lactate was, by subtracting the blood lactate concentration at the end of the second bout (LACE2) from the lactate concentration at the end of the first bout (LACE1). With the delta lactate for each velocity, an individual linear interpolation was plotted, which enabled the calculation of a “null delta lactate”, equivalent to the critical velocity (C V). To verify the stabilization of the blood lactate at intensity of CV, the rats were submitted to 25 minutes of continuous exercise at 15, 20 and 25m.min−1 velocities, with blood collection every 5 minutes. RESULTS: The estimated CV was 16.6 ± 0.7m.min−1, with significant linear regressions (R=0.90±0.03). The animals presented maximal lactate steady state at 3.90 ± 0.35mM of blood lactate, at the velocity of 20m.min−1. At 15m.min−1, the blood lactate also stabilized, but in lower concentration (3.05 ± 0.34mM). There was a progressive increase in blood lactate concentration at 25m.min−1. The CV and MLSS presented significant correlation (r=0.78). CONCLUSIONS: The results suggest that the non-exhaustive protocol used seems to be valid for the aerobic evaluation in sedentary running rats, but this protocol underestimates the MLSS in 20%.