Perceived exertion and blood lactate concentration during graded treadmill running

The purpose of this study was to investigate the influences of treadmill gradients on the rating of perceived exertion (RPE) at two fixed blood lactate concentrations ( La^–]_b). Ten subjects performed three different incremental treadmill protocols by running either uphill (concentrically-biased), downhill (eccentrically-biased), or on the flat (non-biased). Individual data of each protocol were interpolated to reflect La^–]_b corresponding to 2.0 and 4.0 mmol·l^–1. At 2.0 mmol·l^–1 La^– _b, RPE and treadmill speed during downhill running were greater than during level running which was greater than during uphill running (p < 0.05) . Also, the downhill heart rate (HR) was greater than the uphill HR, and downhill minute ventilation ( ) was greater than the level . Treadmill speed was the only measure at 4.0 mmol·l^–1 La^–]_b to differ between gradients. There was a moderate correlation of RPE with HR at both La^–]_b (r = 0.73 at 2.0 mmol·l^–1;r = 0.48 at 4.0 mmol·l^–1) while treadmill speed was moderately correlated with RPE only at 2.0 mmol·l^–1 La^–]_b (r = 0.70). The results of this study demonstrated that the degree of eccentric-bias during running exercise is an influence of perceived exertion at a moderate but not at a high exercise intensity.