Quantifying cardiorespiratory responses resulting from speed and slope increments during motorized treadmill propulsion among manual wheelchair users.

Background: Cardiorespiratory fitness assessment and training among manual wheelchair (MW) users are predominantly done with an arm-crank ergometer. However, arm-crank ergometer biomechanics differ substantially from MW propulsion biomechanics. This study aimed to quantify cardiorespiratory responses resulting from speed and slope increments during MW propulsion on a motorized treadmill and to calculate a predictive equation based on speed and slope for estimating peak oxygen uptake (VO) in MW users.

Methods: In total, 17 long-term MW users completed 12 MW propulsion periods (PP), each lasting 2min, on a motorized treadmill, in a random order. Each PP was separated by a 2-min rest. PPs were characterized by a combination of 3 speeds (0.6, 0.8 and 1.0m/s) and 4 slopes (0°, 2.7°, 3.6° and 4.8°). Six key cardiorespiratory outcome measures (VO, heart rate, respiratory rate, minute ventilation and tidal volume) were recorded by using a gas-exchange analysis system. Rate of perceived exertion (RPE) was measured by using the modified 10-point Borg scale after each PP.

Results: For the 14 participants who completed the test, cardiorespiratory responses increased in response to speed and/or slope increments, except those recorded between the 3.6 and 4.8 slope, for which most outcome measures were comparable. The RPE was positively associated with cardiorespiratory response (r≥0.85). A VO predictive equation (R=99.7%) based on speed and slope for each PP was computed. This equation informed the development of a future testing protocol to linearly increase VO via 1-min stages during treadmill MW propulsion.

Conclusions: Increasing speed and slope while propelling a MW on a motorized treadmill increases cardiorespiratory response along with RPE. RPE can be used to easily and accurately monitor cardiorespiratory responses during MW exercise. The VO can be predicted to some extent by speed and slope during MW propulsion. A testing protocol is proposed to assess cardiorespiratory fitness during motorized MW propulsion.