Aquatic-treadmill walking: quantifying drag force and energy expenditure.
Quantification of the magnitudes of fluid resistance provided by water jets (currents) and their effect on energy expenditure during aquatic-treadmill walking is lacking in the scientific literature.



To quantify the effect of water-jet intensity on jet velocity, drag force, and oxygen uptake (VO2) during aquatic-treadmill walking.



Descriptive and repeated measures.



Athletic training facility.



Water-jet velocities were measured using an electromagnetic flow meter at 9 different jet intensities (0-80% maximum). Drag forces on 3 healthy subjects with a range of frontal areas (600, 880, and 1250 cm2) were measured at each jet intensity with a force transducer and line attached to the subject, who was suspended in water. Five healthy participants (age 37.2 ± 11.3 y, weight 611 ± 96 N) subsequently walked (~1.03 m/s or 2.3 miles/h) on an aquatic treadmill at the 9 different jet intensities while expired gases were collected to estimate VO2.



For the range of jet intensities, water-jet velocities and drag forces were 0-1.2 m/s and 0-47 N, respectively. VO2 increased nonlinearly, with values ranging from 11.4 ± 1.0 to 22.2 ± 3.8 mL · kg-1 · min-1 for 0-80% of jet maximum, respectively.



This study presented methodology for quantifying water-jet flow velocities and drag forces in an aquatic-treadmill environment and examined how different jet intensities influenced VO2 during walking. Quantification of these variables provides a fundamental understanding of aquatic-jet use and its effect on VO2. In practice, the results indicate that VO2 may be substantially increased on an aquatic treadmill while maintaining a relatively slow walking speed.
Biomechanics Laboratory and the Sports Medicine Research Center, Utah State University, Logan, UT USA.
Eadric
E
Bressel
Gerald
G
Smith
Andrew
A
Miller
Dennis
D
Dolny
D000328:Adult; D055592:Biophysical Phenomena / Q000502:physiology*; D004734:Energy Metabolism / Q000502:physiology*; D005260:Female; D006801:Humans; D007101:Immersion; D008297:Male; D010101:Oxygen Consumption / Q000502:physiology*; D016138:Walking / Q000502:physiology*