Measurement errors when estimating the vertical jump height with flight time using photocell devices: the example of Optojump

Abstract

Common methods to estimate vertical jump height (VJH) are based on the measurements of flight time (FT) or vertical reaction force. This study aimed to assess the measurement errors when estimating the VJH with flight time using photocell devices in comparison with the gold standard jump height measured by a force plate (FP). The second purpose was to determine the intrinsic reliability of the Optojump photoelectric cells in estimating VJH. For this aim, 20 subjects (age: 22.50±1.24 years) performed maximal vertical jumps in three modalities in randomized order: the squat jump (SJ), counter-movement jump (CMJ), and CMJ with arm swing (CMJarm). Each trial was simultaneously recorded by the FP and Optojump devices. High intra-class correlation coefficients (ICCs) for validity (0.98-0.99) and low limits of agreement (less than 1.4 cm) were found; even a systematic difference in jump height was consistently observed between FT and double integration of force methods (-31% to -27%; p<0.001) and a large effect size (Cohen’s d>1.2). Intra-session reliability of Optojump was excellent, with ICCs ranging from 0.98 to 0.99, low coefficients of variation (3.98%), and low standard errors of measurement (0.8 cm). It was concluded that there was a high correlation between the two methods to estimate the vertical jump height, but the FT method cannot replace the gold standard, due to the large systematic bias. According to our results, the equations of each of the three jump modalities were presented in order to obtain a better estimation of the jump height.

Test–retest reliability of physical fitness tests among young athletes: The FITescola® battery

“…In our investigation, we found the vertical jump test to have a high agreement between trials, although this measure was better among girls than among boys. Hypothetically, the differences in jump height between trials can be due to systematic bias, such as the athlete's emotional stress (Schaal et al, 2011) or fatigue (Watkins et al, 2017), and variation in jumping mechanics (Attia et al, 2017). However, our overall findings indicate that the horizontal jump test and the vertical jump test may be an appropriate ecologic alternative to laboratory tests examining lower limb strength.…”

Differences and Trial-to-Trial Reliability of Vertical Jump Heights Assessed by Ultrasonic System, Force-Plate, and High-Speed Video Analyses

“…A systematic bias of 11.2 cm has been recently reported between the jump-and-reach height and the FT method (19), which is in accordance with our difference between the FP_FT and the US (13.7 cm) as well as FP_DI (12.3 cm). Attia et al (14) revealed also a systematically greater jump height of 14.5 cm calculated with the DI compared to the FT method. The observed systematic bias may be due to the different methodological definitions of the jump height.…”

“…The impulse-momentum method, grounding on force-time data, is considered as the 'gold standard' for stationary vertical jump height measurements (6,7), even if it is unclear, whether the vertical impulse is exclusively efficient for the jump height or it produces an angular impulse along the horizontal axis of the body, too (9). A further method uses the double integration of the force-time data to calculate the vertical displacement of the centre of mass during a jump (14). Beyond that, all these mentioned methods are limited due to the difficulty to analyse sportspecific unilateral or bilateral jumps on different surfaces, which contain opening steps and altered landing styles as, for instance, in soccer or handball (1,7).…”

Validity and Reliability of the 30-s Continuous Jump for Anaerobic Power and Capacity Assessment in Combat Sport

“…Verbal feedback will be provided to the subject during the test to encourage them to maintain maximum performance (i.e., explosive continuous jump) until the end of the test. All jumps was assessed with Optojump Next (Microgate, Italy) ( Attia et al, 2017 ) and the best performance was then used to compare with WAnT performance.…”