Which Metrics Should I Monitor? Recommendations for Monitoring Acute Changes in Physical Preparedness With...

Badby, AJ, Ripley, NJ, McMahon, JJ, Mundy, PD, and Comfort, P. Which metrics should I monitor? Recommendations for monitoring acute changes in physical preparedness with countermovement jump force-time metrics in youth soccer players in-season. J Strength Cond Res 40(8): e866-e875, 2026-The aim of this study was to determine the effectiveness of utilizing countermovement jump (CMJ) testing using force plates to monitor acute changes in lower-body neuromuscular function (NMF) resulting from in-season competitive match play in soccer athletes. A within-subjects, observational, cross-sectional, repeated-measures study design consisting of 3 in-season testing occasions was prescribed across 3 separate competitive soccer matches: immediately prematch (∼15 minutes), immediately postmatch (∼15 minutes), and ∼48 hours postmatch (match day [MD] +2). Youth Alliance League (U18) soccer players ( N = 27; age 16.9 ± 0.7 years; height 181.4 ± 5.4 cm; mass 73.6 ± 9.1 kg) were recruited from 3 professional English Football League clubs. A repeated-measures analysis of variance demonstrated significant differences ( p < 0.05) across testing timepoints for all metrics except peak propulsive force. Mass-relative (including outcome) metrics cannot be utilized alone for monitoring acute changes in NMF, as significant reductions ( p < 0.001) in body weight were identified from immediately pre- to immediately postmatch and from immediately postmatch to MD+2. Significant reductions ( p < 0.05) from immediately pre- to immediately postmatch (which were maintained at MD+2) in mean propulsive force (minimal detectable change [MDC] = 7.43%), mean propulsive velocity (MDC = 4.93%), mean propulsive power (MDC = 9.38%), and jump momentum (MDC = 4.43%) indicate that these metrics are sensitive to changes in NMF. If utilizing outcome metrics (e.g., jump height; MDC = 8.55%) in addition to these, collectively, monitoring this combination of metrics (and body weight; MDC = 1.37%) will help to explain both if and why any changes in the outcome occur following soccer match play, thus providing valuable context when utilizing the CMJ as an indicator of acute changes in NMF.