Assessment of Loaded Squat Jump Height With a Free-Weight Barbell and Smith Machine: Comparison of the Takeoff Velocity and Flight Time Procedures. Issue 3 (March 2020)

• Record Type: Journal Article
• Authors: Pérez-Castilla, Alejandro; McMahon, John J.; Comfort, Paul; García-Ramos, Amador
• Is Part Of: Journal of strength and conditioning research. Volume 34:Issue 3(2020)
• Publication Date: 2020-03
• Subjects: force platform -- reliability -- vertical jump; Physical education and training -- Periodicals; Weight training -- Physiological aspects -- Periodicals; Physical fitness -- Periodicals; 613.7
• DOI: 10.1519/JSC.0000000000002166
• Languages: English
• ISSNs: 1064-8011

Abstract

Abstract : Abstract: Pérez-Castilla, A, McMahon, JJ, Comfort, P, and García-Ramos, A. Assessment of loaded squat jump height with a free-weight barbell and Smith machine: comparison of the takeoff velocity and flight time procedures. J Strength Cond Res 34(3): 671–677, 2020—The aims of this study were to compare the reliability and magnitude of jump height between the 2 standard procedures of analyzing force platform data to estimate jump height (takeoff velocity [TOV] and flight time [FT]) in the loaded squat jump (SJ) exercise performed with a free-weight barbell and in a Smith machine. Twenty-three collegiate men (age, 23.1 ± 3.2 years; body mass, 74.7 ± 7.3 kg; height, 177.1 ± 7.0 cm) were tested twice for each SJ type (free-weight barbell and Smith machine) with 17-, 30-, 45-, 60-, and 75-kg loads. No substantial differences in reliability were observed between the TOV (coefficient of variation [CV], 9.88%; intraclass correlation coefficient [ICC], 0.82) and FT (CV, 8.68%; ICC, 0.88) procedures (CV ratio, 1.14), whereas the Smith SJ (CV, 7.74%; ICC, 0.87) revealed a higher reliability than the free-weight SJ (CV, 9.88%; ICC, 0.81; CV ratio, 1.28). The TOV procedure provided higher magnitudes of jump height than the FT procedure for the loaded Smith machine SJ (systematic bias, 2.64 cm; p ⩽ 0.05), whereas no significant differences between the TOV and FT procedures were observed in the free-weight SJ exercise (systematic bias, 0.26 cm; p > 0.05). Heteroscedasticity of the errors was observed for the Smith machine SJ ( r 2 = 0.177) with increasing differences in favor of the TOV procedure for the trials with lower jump height (i.e., higher external loads). Based on these results, the use of a Smith machine in conjunction with the FT more accurately determine jump height during the loaded SJ.