Training effect on performance, substrate balance and blood lactate concentration at maximal lactate steady state in...

Training effects on time-to-exhaustion, substrate and blood lactate balances at the maximal lactate steady state velocity (MLSSv) were examined. Eleven male, veteran, long-distance runners performed three tests before and after 6 weeks of training at MLSSv: an incremental test to determine maximum O2 uptake (VO(2,max)) and the velocity at the lactate threshold (vLT), a sub-maximal test of two stages of 20 min at 95 and 105% of vLT separated by 40 min rest to determine the MLSSv and the corresponding lactate concentration (MLSSc) and a time-to-exhaustion run at MLSSv for which the substrate balance was calculated. Duration and distance run at MLSSv increased dramatically respectively from 44+/-10 to 63+/-12 min and from 10.4 to 15.7 km respectively (P<0.01). MLSSv increased significantly with training but the relative fraction of VO(2,max) remained the same (85.2+/-4.5 vs. 85.3+/-5.2%, P=0.93). MLSSc was unaffected by training as determined from the percentage of energy yielded by carbohydrates (80%) during the exhaustive run at MLSSv. These findings show that training at MLSS elicits small increases in MLSSv and VO(2,max), but enhances time-to-exhaustion (endurance) at MLSSv substantially (+50%). Training does not change the proportion of carbohydrate oxidized, which is the major substrate used during an exhaustive run at MLSS lasting 1 h.