Underwater Cycle Ergometry: Power Requirements With and Without Diver Thermal Dress
Technical rept. Apr-Jun 2008
NAVY EXPERIMENTAL DIVING UNIT PANAMA CITY FL
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Navy Experimental Diving Unit NEDU uses cycle ergometers to increase diver oxygen consumption in many different experiments. An ongoing problem has been that, although the power requirement of cycling in the water is known to be greater than that in air for the same ergometer setting, the magnitude of the difference, particularly with diver thermal dress, has been unclear. We compared oxygen consumption during dry ergometry to that during ergometry in head-out water immersion among a total of 25 cycling subjects who wore PT gear, wet suits, dry suits, or non-return valve NRV suits. We also measured the effects of pedal cadence with different diver dress. Additional power varied greatly among subjects and was either independent of ergometer setting or increased with setting. Mean additional power when constant with increased ergometer setting was 64 standard error SE 5 W, 69 SE 5 W, SE 9 W, and 126 SE 7 W at 60 rpm in PT gear, wet suit, dry suit, and NRV suit, respectively. Additional power requirements varied approximately with the cube of cadence, a variation suggesting drag and moment of inertia, not additional torque, as the causes. Additional power in a wet suit was no different from that in PT gear. Greater pedal drag and less stable subject position may cause a greater additional power requirement at NEDU than that measured at other institutions. High intersubject variations mean that a direct measure of oxygen consumption is necessary, if that variable must be controlled.
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