Research News Flash
A 1.0 percent treadmill gradient has been found to be most representative of the energy costs needed for over-ground running at varying speeds. However, this information does not necessarily translate to wheelchair athletes given the varying resistive forces present in running vs. wheelchair sports. To date, an optimal gradient for treadmill-based exercise in wheelchair-based exercise protocols is unknown.
The purpose of this study was to determine which laboratory exercise conditions provide the most accurate physiological and biomechanical comparison to over-ground wheelchair sports. The study analyzed heart rate, respiratory data (VO2 and respiratory exchange ratios), mechanical efficiency, and kinetic and temporal parameters associated with propulsion in 15 able-bodied participants with previous experience in wheelchair propulsion. Each participant performed three three-minute trials for each of the different modalities, including over ground on a wooden sprung surface, wheelchair ergometer, and treadmill propulsion at varying gradients. Each modality consisted of trials at four, six, and eight km/h. During the treadmill trials, the participant performed the test at each speed across varying treadmill gradients of 0.0, 0.7, 1.0, and 1.3 percent, for a total of 12 trials. The wheelchair was equipped with a force-sensing SMARTWHEEL, and speed was monitored using a speedometer strapped to the participant’s knees.
The results of the study showed that the treadmill gradient of 0.7 percent was most representative of over ground physiological and biomechanical requirements at speeds of four and six km/h. A 1.0 percent treadmill gradient was shown to be a valid condition to simulate physiological requirements at eight km/h. Therefore, when performing fixed-gradient exercise protocols, a treadmill gradient of 0.7 percent should be utilized due to its association with important physiological markers such as VO2 and heart rate across different speeds. When performing fixed-speed protocols at lower speeds, the study showed 0.7 percent treadmill gradient is most appropriate, while at higher speeds the study showed 1.0 percent treadmill gradient to be most representative of the over ground demands. Future studies should compare physiological demands at a greater number of gradients and broader range of speeds.
Mason, B., Lenton, J., Leicht, C., & Goosey-Tolfrey, V. (2014). A physiological and biomechanical comparison of over-ground, treadmill and ergometer wheelchair propulsion. Journal of Sports Sciences, 32(1), 78-91.