Cardiorespiratory Responses to Continuously-Graded and Ramp Treadmill Protocols

Abstract

Ramped treadmill protocols (RTP) are often used for stress testing in clinical and low-fit populations because small frequent adjustments in work rate are thought to reduce cardiorespiratory stress and elicit higher fitness estimates versus graded treadmill tests (GTP). It is not known if RTP are of similar utility in fit individuals. Our purpose was to compare cardiorespiratory responses to RTP and GTP in healthy middle-aged adults of different fitness status. Seventy-one men and women (higher-fit: n = 32, BMI = 24.2 ± 3.3 kg/m2, VO2peak > 69th percentile; moderately-fit: n = 13, BMI = 24.9 ± 2.3 kg/m2, VO2peak 50-69th percentile; lower-fit: n = 26, BMI = 27.5 ± 4.7 kg/m2, VO2peak < 50th percentile) completed RTP and GTP matched for work rates every 3 min in a randomized cross-over design. Differences in submaximal and peak heart rate, blood pressures, rate pressure product, oxygen consumption, ventilation, and perceived exertion were determined using mixed factorial ANOVAs. Submaximal heart rates and respiratory gas exchange variables were lower at equivalent work rates during the RTP (p < 0.05). Treadmill time, but not VO2peak, was greater with RTP compared to GTP across groups (p <0.05). RTP elicited lower cardiorespiratory responses at equivalent submaximal work rates; however, RTP and GTP yield similar peak results and are equally tolerated across fitness categories in healthy adults.