Abstract
The aims of the present study are to: (1) determine within- and between-session reliability of multiple metrics obtained during the triple hop test; and (2) determine any systematic bias in both the test and inter-limb asymmetry scores for these metrics. Thirteen male young American football athletes performed three trials of a triple hop test on each leg on two separate occasions. In addition to the total distance hopped, manual detection of touch down and toe-off were calculated via video analysis, enabling flight time (for each hop), ground contact time (GCT), reactive strength index (RSI), and leg stiffness (between hops) to be calculated. Results showed all coefficient of variation (CV) values were ≤ 10.67% and intraclass correlation coefficients (ICC) ranged from moderate to excellent (0.53–0.95) in both test sessions. Intrarater reliability showed excellent reliability for all metrics (CV ≤ 3.60%, ICC ≥ 0.97). No systematic bias was evident between test sessions for raw test scores (g = −0.34 to 0.32) or the magnitude of asymmetry (g = −0.19 to 0.43). However, ‘real’ changes in asymmetry (i.e., greater than the CV in session 1) were evident on an individual level for all metrics. For the direction of asymmetry, kappa coefficients revealed poor-to-fair levels of agreement between test sessions for all metrics (K = −0.10 to 0.39), with the exception of the first hop (K = 0.69). These data show that, given the inherent limitations of distance jumped in the triple hop test, practitioners can confidently gather a range of reliable data when computed manually, provided sufficient test familiarization is conducted. In addition, although the magnitude of asymmetry appears to show only small changes between test sessions, limb dominance does appear to fluctuate between test sessions, highlighting the value of also monitoring the direction of the imbalance.
Highlights
Jump testing is a common method of quantifying ballistic force production capabilities and is often implemented to assess lower body jump performance [1,2], neuromuscular fatigue [3,4], inter-limb asymmetry [5,6], and rehabilitation status post injury [7,8]
No systematic bias was evident between test sessions (p > 0.05; g range = −0.34 to 0.32)
Moving forward, given the importance of monitoring more than the outcome measure solely, we suggest that, where possible, practitioners take the time to calculate and quantify some strategy-based metrics, such as reactive strength index (RSI) and leg stiffness, as these may be more sensitive to change than jump distance [34]
Summary
Jump tests are commonly used due to the associated (and previously reported) strong reliability and time-efficient methods [2,5], making them viable for a wide range of practitioners. Such reasons are key, as they help to ensure confidence in subsequent data collection procedures, whilst enabling a means of gathering objective data for those working in sports with large squads of athletes (e.g., American football, soccer, baseball, and rugby). Horizontal hop testing is regularly implemented in rehabilitation settings and has been frequently cited in the rehabilitation literature as a method of analyzing rehabilitation status and return-to-sport readiness [7,9,10,11]. Metrics that elicit an understanding of jump strategy (e.g., reactive strength and propulsive impulse) have been championed, owing to their better ability to detect meaningful change greater than the error in the test [4,17] and provide a more in-depth understanding of jump performance [18,19,20,21]
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