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Wake Forest University - October 24th, 2000

Methods

On two separate occasions all participants completed a bicycle maximal oxygen uptake (V02max) test. Participants rode with either the Z-Torque crank or the normal crank configuration in a randomized order. All tests were conducted on a Cannondale mountain bike frame mounted on a Velodyne trainer (Schwinn Corp., Chicago, IL). Oxygen uptake was measured using a MedGraphics CPXID metabolic cart. The seat height of the bike was adjusted as closely as possible to each subject's own bicycle dimensions. The Velodyne trainer, an ergometer on which a bike minus the front wheel is mounted, controls power output via electromagnetic resistance. Power output is independent of cadence and gearing.

The test protocol was identical for each subject and consisted of a 5 min warmup ride at 100 W, followed by 5 min at 150 W, and 5 min at 200 W, after which power output increased by 25 W every minute until volitional exhaustion.

Heart rate (HR) and rating of perceived exertion (RPE), were determined at 150 and 200 W and at the end of every minute during the incremental test. The peak power output at the end of the incremental test was also recorded.

The rate of energy expenditure was calculated from the oxygen consumption and respiratory exchange ratio values at each power output. Energy expenditure and power output were expressed in watts. Gross efficiency at each power output was calculated as the power output/energy expenditure X 100. 

Results

Participants achieved similar maximal oxygen consumption, peak power outputs and gross efficiencies with the Z-Torque and normal crank configurations (Table 1). In addition, ratings of perceived exertion (RPE) at 150 and 200 W, heart rate (HR) at peak power output, 150, and 200 W, and cadence at 150 and 200 W were not significantly different. However, participants perceived their effort to be significantly lower at peak power output with the Z-Torque crank.