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Mechanical Scale and Load Cell Underwater Weighing: A Comparison of Simultaneous Measurements and the Reliability of Methods

Moon, Jordan R1; Stout, Jeffrey R2; Walter, Ashley A3; Smith, Abbie E2; Stock, Matt S3; Herda, Trent J3; Sherk, Vanessa D4; Young, Kaelin C4; Lockwood, Christopher M2; Kendall, Kristina L2; Fukuda, David H2; Graef, Jennifer L2; Cramer, Joel T3; Beck, Travis W3; Esposito, Enrico N5

Journal of Strength & Conditioning Research:
doi: 10.1519/JSC.0b013e3181e99c2d
Original Research

Moon, JR, Stout, JR, Walter, AA, Smith, AE, Stock, MS, Herda, TJ, Sherk, VD, Young, KC, Lockwood, CM, Kendall, KL, Fukuda, DH, Graef, JL, Cramer, JT, Beck, TW, and Esposito, EN. Mechanical scale and load cell underwater weighing: a comparison of simultaneous measurements and the reliability of methods. J Strength Cond Res 25(3): 652-661, 2011-Both load cell and mechanical scale-based hydrostatic weighing (HW) systems are used for the measurement of underwater weight. However, there has been no direct comparison of the 2 methods. The purpose of the current investigation was to simultaneously compare a load cell and mechanical scale for use in HW. Twenty-seven men and women (mean ± SD, age: 22 ± 2 years) participated in the 2-day investigation. Each subject completed 2 HW assessments 24 hours apart. Single-day comparisons of all trials for both days revealed no significant difference between the mechanical scale and the load cell (mean difference < 0.016 kg, p > 0.05). True underwater weight values were not significantly different between methods for either days (mean difference < 0.014 kg, p > 0.05) and accounted for a mean difference in percent fat (%FAT) of <0.108%. The 95% limits of agreement indicated a maximum difference between methods of 0.53% FAT. Both methods produced similar reliability SEM values (mechanical SEM < 0.72%FAT, load cell SEM < 0.75%FAT). In conclusion, there was no difference between mechanical scale and load cell measurements of underwater weights and the added precision of the load cell only marginally (<0.16%FAT) improved day-to-day reliability. Either a mechanical scale or load cell can be used for HW with similar accuracy and reliability in young adults with a body mass index of 18.7-34.4 (5-25%FAT).

Author Information

1Human Performance and Body Composition Laboratories, Department of Sports Fitness and Health, United States Sports Academy, Daphne, Alabama; 2Metabolic and Body Composition Laboratories, Department of Health and Exercise Science, University of Oklahoma, Norman, Oklahoma; 3Biophysics Laboratory, Department of Health and Exercise Science, University of Oklahoma, Norman, Oklahoma; 4Bone Density Laboratory, Department of Health and Exercise Science, University of Oklahoma, Norman, Oklahoma; and 5Sports Medicine Rehabilitation Laboratory, Department of Sports Medicine, United States Sports Academy, Daphne, Alabama

Address correspondence to Dr. Jordan R. Moon,

© 2011 National Strength and Conditioning Association