The Validity Of The Lactate Minimum Test Adapted To Rats

Abstract

PURPOSE In the present study, adult (90 days) male wistar rats were submitted to the lactate minimum test (TLM), adapted for rats, and were trained at the lactate minimum (LM) intensity. After 8 weeks, they were submitted to the TLM again, to verify the sensivity of the test to the metabolic alterations induced by aerobic training. METHODS For the TLM, first the rats exercised (jumps in the water) for 3 min (30s activity interrupted by 30s rest), supporting a load of 50 % of body weight (bw), to increase blood lactate concentration. After a 9 min period of rest, they began an incremental exercise protocol (swimming), supporting loads of 4.5, 5.0, 5.5, 6.0 and 6.5 bw, 5 min in each load. Blood samples were collected for lactate determination at each load change. The second-degree equations which defined the curves blood lactate vs workload enabled the calculation of the lowest blood lactate concentration (BL) and the corresponding load (LM). In vitro soleus muscle protein synthesis (14C phenilalanyn incorporation to protein) and breakdown (tyrosin release) rates were assessed in the sedentary and trained condition. RESULTS Before training LM (% bw) was 5.10±0.03 at a BL (mmol/L) 7.19±0.46. In the sedentary condition muscle protein synthesis rates (p.mol/mg.h) were 2.2±0.5 and protein breakdown (p.mol/mg.h) rates were 339.7±80.1. After training, LM increase (5.52±0.05), and was obtained at a lower BL (4.90±0.27). Muscle protein synthesis rates were not altered (2.7±0.9) but the breakdown rates were reduced (267±48.5). CONCLUSION Taken together, these results indicate that the TLM discriminated the alterations promoted by exercise training, suggesting the validity of the test adapted for rats. Supported by FAPESP and CNPq