Comparison of Resistance-Based Walking Cardiorespiratory Test to The Bruce Protocol
Cardiorespiratory fitness is assessed through graded exercise tests that determine the maximum amount of sustained mechanical work that an individual can perform while also providing health and fitness related information. This manuscript describes a novel method to perform graded exercise tests that uses posteriorly directed resistive forces. The purpose of this investigation is to validate a novel resistance based test in comparison to a traditional speed and incline based test in a cohort of non-impaired individuals. Twenty non-impaired individuals, 8 males, 12 females, mean age 28.4± 9.6, range 20-54 years old. Participants performed two maximal exercise tests. The speed and incline based test used the Bruce protocol and increased treadmill incline and speed every three minutes. The resistance based test used a robotic device interfaced with the treadmill that provided specified horizontal resistive forces at the center of mass calculated to match each Bruce Protocol stage while individuals walked at 1.1 m/s. Participants obtained ∼3% higher maximum V˙O2 measure using the speed and incline based method (dependent t-test p=0.08). V˙O2 peaks between tests were strongly correlated (r=0.93, p<0.001). Peak values of secondary physiologic measures (i.e., max heart rate, respiratory exchange ratio) were within 3% between tests. We found a significant linear relationship between mass-specific work rate and measured V˙O2 stage-by-stage for both tests, but no significant difference between each linear fit (p=0.84). These data suggest horizontal resistive forces while walking on a treadmill, can be used to increase aerobic effort in a way that closely simulates work rates of the Bruce Protocol.