Physiological Responses at the Critical Heart Rate During Treadmill Running

The purposes of this study were to: 1) determine if the critical heart rate (CHR) model for cycle ergometry can be applied to treadmill running; and 2) examine the times to exhaustion (T lim) as well as the ! VO 2 , ratings of perceived exertion (RPE), electromyographic amplitude (EMG AMP) and mean power frequency (MPF) responses during constant heart rate (HR) runs at CHR-5 b·min-1 (CHR-5), CHR, and CHR+5 b·min-1 (CHR+5). Thirteen runners performed an incremental treadmill test to exhaustion. On separate days, 4 constant velocity runs to exhaustion were performed. The total number of heart beats (HB lim) for each velocity was calculated as the product of the average 5 s HR and T lim. The CHR was the slope coefficient of the HB lim versus T lim relationship. The physiological responses were recorded during the constant HR runs. Polynomial regression analyses were used to examine the patterns of responses for all.