Aerobic capacity evaluation of Sprague Dawley rats in treadmill running: comparison between protocols

The objective of the present study was to compare and test the applicability of different protocols for accessing aerobic capacity in Sprague Dawley rats using treadmill running. Fifteen 70-day-old adult Sprague Dawley rats (270-290 g) were used. After 5 days of adaptation to the treadmill, the animals underwent 7 days of evaluations with a 48-h interval between each protocol. On the first two days, they underwent, in random order, a graded exercise test, with (GXT2) or without (GXT1) blood sample collections to determine blood lactate concentrations and the anaerobic threshold. In the subsequent 4 days, they underwent continuous 30-min efforts to determine the maximal lactate steady state (MLSS) with the intensity prescribed in percentages of the maximum speed (MaxS) obtained in GXT1, and on the last day they underwent the minimum lactate (ML) protocol. The MaxS obtained in GXT2 was higher than in GXT1, and there was a moderate correlation (r=0.614, P=0.011) between them. In many cases, lactate and glucose blood concentrations did not show the expected kinetics, making aerobic capacity determination impossible using these protocols. MLSS showed a higher success rate compared to other protocols (MLSS=80%; GXT2=47%; ML=60%). In conclusion, with the MLSS protocol, it is only possible to measure time to exhaustion at each intensity, which does not exactly reflect aerobic capacity, and the use of blood lactate and glucose concentrations to evaluate the aerobic capacity of rats in incremental and ML treadmill running protocols is still discouraged.