Abstract
The purpose of the present study was to evaluate whether lactate threshold (LT) in rats could be detected from changes of blood lactate concentration during intensive graded exercise (IGE) with 2 protocols and prolonged exercise (PE) using motor driven treadmill. Rats used in this study were male and female Wistar strain rats 5 weeks of age. After running for 10 minutes per day for 1 week, IGE test was performed with 6 to 7 week old rats. Experimental periods for PE test ranged from 7 to 9 weeks old. Although blood lactate concentration during IGE test was exponentially increased, formal LT was hard to determine. In PE at speed of 23m/min, blood lactate concentration initially increased, and thereafter stablized or gradually decreased to the resting level. At this speed, rats could well tolerate running for 60 minutes. But, blood lactate concentration during PE at speed of 28m/min linearly increased with lapse of time. Endurance time at this speed and peak blood lactate value averaged 38 minutes (30-44 minutes) and 7.0mM (6.2-7.5mM), respectively. From these results, we estimated that the velocity corresponding to LT in rats 6 to 9 weeks of age was about 23m/min.
