title: Mechanical scale and load cell underwater weighing: a comparison of simultaneous measurements and the reliability of methods.
abstract: 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).
authors.affiliation: Human Performance and Body Composition Laboratories, Department of Sports Fitness and Health, United States Sports Academy, Daphne, Alabama, USA. jmoon@ussa.edu
authors.forename: Jordan R
authors.initials: JR
authors.lastname: Moon
authors.forename: Jeffrey R
authors.initials: JR
authors.lastname: Stout
authors.forename: Ashley A
authors.initials: AA
authors.lastname: Walter
authors.forename: Abbie E
authors.initials: AE
authors.lastname: Smith
authors.forename: Matt S
authors.initials: MS
authors.lastname: Stock
authors.forename: Trent J
authors.initials: TJ
authors.lastname: Herda
authors.forename: Vanessa D
authors.initials: VD
authors.lastname: Sherk
authors.forename: Kaelin C
authors.initials: KC
authors.lastname: Young
authors.forename: Christopher M
authors.initials: CM
authors.lastname: Lockwood
authors.forename: Kristina L
authors.initials: KL
authors.lastname: Kendall
authors.forename: David H
authors.initials: DH
authors.lastname: Fukuda
authors.forename: Jennifer L
authors.initials: JL
authors.lastname: Graef
authors.forename: Joel T
authors.initials: JT
authors.lastname: Cramer
authors.forename: Travis W
authors.initials: TW
authors.lastname: Beck
authors.forename: Enrico N
authors.initials: EN
authors.lastname: Esposito
mesh_terms: D000328:Adult; D001823:Body Composition / Q000502:physiology*; D001835:Body Weight / Q000502:physiology*; D001837:Body Weights and Measures / Q000379:methods*; D005260:Female; D006801:Humans; D007101:Immersion; D008297:Male; D015203:Reproducibility of Results; D055815:Young Adult