The physiological and perceptual demands of running on a curved non-motorized treadmill compared with running on a motorized treadmill set at different grades

The current study compared the physiological and perceptual demands of running on a commercially available curved non-motorized treadmill (cNMT) to different incline grades on a motorized treadmill (MT). Method: Ten male team-sport athletes completed, after a familiarization session, a 6 min run at a target velocity of 2.78 m·s-1 on the cNMT (cNMTrun). Mean individual running velocity of cNMTrun was then used as warm-up and experimental running velocity in three subsequent visits, in which participants ran for 6 min on the MT set at different grades (4%, 6% or 8%). In all experimental trials (cNMTrun, 4MTrun, 6MTrun and 8MTrun), oxygen consumption (V̇O2) and heart rate (HR) were monitored, and ratings of perceived exertion (RPE) were obtained. Results: HR in cNMTrun was significantly higher compared to all MT trials. V̇O2 and RPE were significantly higher in cNMTrun compared to 4MTrun, but not different to 6MTrun and 8MTrun. The relationship between V̇O2 and MT grade was highly linear, and using linear interpolation, the concave curved design of the cNMT was estimated to mimic a 6.9 ± 3% MT grade. Conclusion: On matched running velocities, V̇O2 and RPE responses while running on the cNMT are similar to a 6-8% MT grade. These findings can be used as reference value by athletes and coaches in the planning of cNMT training sessions, and amend running velocities accordingly. Future studies are needed to determine whether this estimate is similar for lighter and/or female runners.