Reliability of bilateral and shear components in a two-legged counter-movement jump

Abstract

Strength asymmetry can be detrimental to athlete performance and may lead to injury. The countermovement jump (CMJ) can be used to measure strength asymmetry via shear force production. The reliability of parameters and effects of asymmetry and shear force production on vertical CMJ performance were evaluated in a study with 15 university-level sprint and high jump athletes ( m = 11, f = 4). The athletes performed three CMJs on two occasions, separated by 1 week. Tri-axial ground reaction force (GRF) was recorded using two force platforms embedded within a bespoke weight training area. Key performance metrics were calculated in real-time describing total CMJ performance, asymmetry and shear force production. Changes in the means and coefficients of variation (CV) were used to express reliability. Twenty-six parameters from the Total analysis and 21 Asymmetry analysis parameters showed a CV lower than 10%. Temporal and kinetic variables describing Asymmetry analysis highlight a lower CV compared with equivalent parameters derived from Total analysis. Shear parameters show high levels of CV compared with Total analysis and Asymmetry analysis. The measures of asymmetry calculated using methods described in this work were shown to be reliable for monitoring CMJ performance. No significant negative relationships were found between measures of asymmetry or shear force and traditional performance metrics in the CMJ (e.g. jump height, specific peak power and peak force). Further work is required to identify the potential of reducing asymmetry on CMJ performance.

Assessment of Countermovement Jump: What Should We Report?

“…Specifically, all velocity- and COM-related variables were reliable, as well as the duration of the propulsive phase, flight phase, and the ratio between flight time and overall jump time. In line with our study, velocity-related variables were shown to be consistently reliable [ 19 , 21 , 39 ], as well as the COM-related variables (depth of the countermovement and height of the COM at take-off) [ 14 , 19 , 39 ]. However, the results of previous studies are somewhat contradictory when it comes to the reliability of the duration of the different CMJ phases.…”

Patellar Tendon Structural Adaptations Occur during Pre-Season and First Competitive Cycle in Male Professional Handball Players

“…The results showed a tendency toward decrease in healthy tendon and increase in injured tendon (echo types III and IV), even though we were not able to demonstrate this tendency statistically. The results of this study support previous histological findings proving that tendon structural changes are a response to the load applied [25,26].…”

“…The above Table 1 shows the intraclass correlation coefficient (ICC) values for patellar tendon UTC for all echotypes at 20%, 40% and 80% of tendon length. ICC for CMJ is also reported to be a reliable test; however, it was not performed in this study [25]. The descriptive data median, interquartile range (IQR), and coefficient interval percentage at 95% at the first and last day of pre-season and following the first competitive training for healthy and injured tendon at 20%, 40% and 80% tendon length is provided in the Tables A1-A3, as well as in Figure 2.…”

Whole-Body Reactive Agility Metrics to Identify Football Players With a Core and Lower Extremity Injury Risk

“…A variable that should be considered in any injury prediction model is performance asymmetry. An asymmetry (Asym) represents differences between right and left direction and is expressed as a percentage (Gordon et al, 2021 ). Helme et al, did a systematic review of 14 clinical prediction model studies with half of the studies finding statistically significant results.…”