Flight-Time Method Modified: Development of a Novel and More Accurate Method for Measuring Vertical Jump Height Using a Smartphone Application.

Nishioka, Takuya; Yamaguchi, Shota; Inami, Takayuki

Purpose: The flight-time method (FT) is used for measuring vertical jump height (JH) in the field because of its convenience; however, FT overestimates JH when the lower limb is flexed at landing. Herein, we proposed a new method (ie, flight-time method modified [FTM]) to address the problem of FT and evaluate its validity and reliability. Methods: A total of 24 men performed 6 countermovement jumps on force plates (sampling rate: 1000 Hz) while being recorded with a smartphone high-speed camera at 240 frames·s–1. JH was calculated by the impulse–momentum method (IM), FT, and FTM. For FTM, the flight time and JH were calculated based on the displacement of the greater-trochanter marker using a smartphone application. Results: JH calculated using FT was significantly higher (P <.001) compared with JH calculated by IM; however, JH calculated by FTM showed no significant difference with JH calculated by IM. Furthermore, JH calculated by FTM, compared with JH calculated by FT (ρ =.882; 95% CI,.838–.914), exhibited a stronger, nearly perfect, and significantly positive correlation (ρ =.987; 95% CI,.982–.991) with JH calculated by IM and showed high reliability. Conclusions: The FTM proposed in this study had higher concurrent validity compared with FT and a high reliability for measuring countermovement JH because it was not affected by lower-extremity flexion at landing. Therefore, practitioners should consider using FTM as a convenient, low-cost, reliable, and more valid method for measuring JH in the field.

LEG physiology; BIOMECHANICS; MOBILE apps; STATISTICAL correlation; PEARSON correlation (Statistics); EFFECT sizes (Statistics); SMARTPHONES; DATA analysis; T-test (Statistics); RESEARCH evaluation; DESCRIPTIVE statistics; MANN Whitney U Test; STATISTICS; ONE-way analysis of variance; FRIEDMAN test (Statistics); EXERCISE tests; JUMPING; COMPARATIVE studies; CONFIDENCE intervals; DATA analysis software; RANGE of motion of joints; VIDEO recording; EVALUATION

International Journal of Sports Physiology & Performance, 2025, Vol 20, Issue 1, p56

1555-0265

Academic Journal

10.1123/ijspp.2024-0063