PLASMA LACTATE AND VENTILATION THRESHOLDS IN TRAINED AND UNTRAINED CYCLISTS

Six trained male cyclists and six untrained sedentary men were studied to determine whether the plasma lactate threshold (PLT) and ventilation threshold (VT) occur at the same work rate in both fit and unfit populations. The PLT was determined from a marked increase in plasma lactate concentration ([La]) and VT from a nonlinear increase in expired minute ventilation (.ovrhdot.VE) during incremental leg-cycling tests; work rate was increased 30 W every 2 min until volitional exhaustion. The trained subjects'' mean .ovrhdot.VO2 max (63.8 ml O2 .cntdot. kg-1 .cntdot. min-1) and VT (65.8% .ovrhdot.VO2 max) were significantly higher (P < 0.05) than the untrained subjects'' mean .ovrhdot.VO2 max (35.5 ml O2 .cntdot. kg-1 .cntdot. min-1) and VT (51.4% .ovrhdot.VO2 max). The trained subjects'' mean PLT (68.8% .ovrhdot.VO2 max) and VT did not differ significantly, but the untrained subjects'' mean PLT (61.6% .ovrhdot.VO2 max) was significantly higher than their VT. The trained subjects'' mean peak [La] (10.5 mmol .cntdot. l-1) did not differ significantly from the untrained subjects'' mean peak [La] (11.5 mmol .cntdot. l-1). However, the time of appearance of the peak [La] during passive recovery was inversely related to .ovrhdot.VO2 max. These results suggest that variance in lactate diffusion and/or removal processes between the trained and untrained subjects may account in part for the different relationships between the VT and PLT in each population.