Prediction of aquatic treadmill (ATM) energy expenditure and comparison with equivalent land treadmill (LTM) running speeds

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Journal/Book Title/Conference

Poster session at 62nd Annual Meeting of the American College of Sports Medicine (ACSM)




San Diego, CA

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The use of aquatic treadmills (ATM) provide an alternative mode of exercise conditioning when exercise on a land treadmill (LTM) is limited due to injury or recovery from surgical intervention. Yet providing an ATM intensity that mimics a corresponding LTM exercise intensity is less clear.

PURPOSE:This study sought to examine the metabolic (VO2) relationship between varying jet resistances and running speed on an ATM versus LTM.

METHODS: Experienced runners (n = 18) completed an initial VO2 peak test, three LTM trials, and 18 ATM trials. Each ATM trial consisted of running for three minutes at either an individual’s relatively slow, moderate and somewhat fast speed while one of six ATM jet settings ranging from 0 to 100% jet capacity in 20% increments were assigned to each trial. Oxygen consumption (VO2) and heart rate (HR) were measured during each trial while ratings of perceived exertion (RPE) were solicited immediately following each trial.

RESULTS: Resulting analysis produced an ATM prediction equation for relative VO2 = -5.4556 + 5.3674*Speed + .3221*Jet Resistance - 0.1649 (Jet Resistance*Speed) with R-squared = 0.92. Differences in the actual (37.6 ± 10.5 ml · kg -1·min-1) vs predicted (38.2 ± 9.1 ml ·kg-1 ·min-1) VO2 for all ATM conditions were similar (p>0.05) however the residual values (4.38 ± 3.37 ml ·kg-1 ·min-1) suggest greater variability. Developing jet resistance specific equations accounted for non-linear impact of jet resistance on energy expenditure. For LTM the prediction equation for relative VO2 was: VO2 = 6.1034 + 4.37*speed, with residual scores of 0.93 ± ml ·kg-1 ·min-1 and a R-squared = 0.95. At a given ATM speed the increased VO2 associated with each jet setting during ATM trials (20, 40, 60, 80 and 100%) corresponded to an average estimated change in comparable LTM speed of -0.96, +0.91, +1.53, +3.05, and +4.16 miles per hour respectively.

CONCLUSIONS: These results demonstrate that ATM metabolic costs appear to be more variable than LTM and may be due to jet resistance’s non-linear impact on energy expenditure. Jet resistances of >40% provide an intensity of exercise that mimics running faster on LTM. This provides an added benefit for those individuals who may be limited due to acute overuse-type injuries or returning to full LTM activity following lower extremity surgery.

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