Physiological responses at various lactate markers for running at 4 and 8 minute treadmill increments.

Abstract

We compared physiological responses corresponding to speeds at plasma lactate markers between incrementa l treadmill running of 4 and 8 min stages in fifteen healthy men (23 ± 4 yrs , 1.78 ± 0.49 m, 72.7 ± 10.8 kg).Treadmill speed, oxygen uptake ( V  O 2 ), heart rate (HR), rating of perceived exertion (RPE) and plasma lactate were measured for each stage, and calculated at: fixed blood lactate accumulation (FBLA) 4.0 mmol/L , an initial 1 mmol/L rise, deviation maximum (D max ), lactate t hreshold (LT) and log - log LT. There was no effect ( p >0.05) of stage duration on speed, V  O 2 , HR and RPE at fixed markers. For 8 min stages, speed was lower at modelled markers: D max ( - 1.1 km/ h; p= 0.001), LT ( - 0.9 km/ h ; p=0 .008) and log - log LT ( - 0.8 km/h; p=0 .006), yet RPE was higher and V  O 2 lower for LT (1.1, p= 0.02 ; - 0.27 L/ min, p= 0.01 ) and log - log LT (1.4, p= 0.03 ; - 0.29 L/min , p= 0.002). Lactate and V  O 2 were greater at 8 km/h for 4 min ( p= 0.000 1), then similar until 11 km/ h , with a trend towards elevated plasma lactate for 4 min thereafter. When applying lactate threshold markers to assess physiological responses to incremental running, protocols using prolonged stage durations may underestimate marker running speed