Geneau, Mary C ORCID: 0000-0001-6778-4784, Carey, David L, Gastin, Paul B, Robertson, Samuel ORCID: 0000-0002-8330-0011 and James, Lachlan P ORCID: 0000-0002-0598-5502 (2024) Classification of Force-Time Metrics into Lower-Body Strength Domains. Journal of Strength and Conditioning Research, 38 (9). pp. 1561-1567. ISSN 1064-8011

Abstract

The purpose of this study was to classify force-Time metrics into distinct lower-body strength domains using a systematic data reduction analysis. A cross-sectional design was used, whereby competitive field sport athletes (F = 39, M = 96) completed a series of drop jumps, squat jumps, countermovement jumps (CMJs), loaded CMJs, and 2 isometric tasks on portable force platforms, resulting in a total of 285 force-Time performance metrics. The metrics were split into 4 test "families"and each was entered into a sparse principal component analysis (sPCA) model. A single metric from each component of each family-specific sPCA were selected based on the loading, reliability, and simplicity of the metric and entered into a second sPCA that included metrics across all tests. The final sPCA revealed 7 principal components each containing 2 metrics and explained a total of 53% variance of the dataset. The final principal components were interpreted as 7 lower-body strength domains: (a) dynamic force, (b) dynamic timing, (c) early isometric, (d) maximal isometric, (e) countermovement velocity, (f) reactive output, and (g) reactive timing. The findings demonstrate that a total of 7 metrics from a drop jump, CMJ, and isometric test can be used to represent ∼50% of variance in lower-body strength performance of field sport athletes. These results can help guide and simplify the lower-body strength diagnosis process in field sport athletes.

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