Are foot posture and morphological deformation associated with ankle plantar flexion isokinetic strength and vertical drop jump kinetics? A principal component analysis.

Static measurements are clinically useful in characterising foot morphology, but it remains unclear to what extent it can influence dynamic lower limb performance. Therefore, the purpose of this study was to investigate if foot posture or foot morphology deformation relates to ankle plantarflexion isokinetic strength and specific kinetics variables during jumping using principal component analysis (PCA). Thirty-eight physically active participants performed drop vertical jump (DVJ) onto force platforms and ankle plantarflexion contractions in different modalities on an isokinetic dynamometer. Foot posture was assessed using the Foot Posture Index-6 item, whereas foot one-, two- and three-dimensional morphological deformation was calculated using the Arch Height Index Measurement System. A PCA was applied to the ankle plantarflexion and kinetics performance data and correlations between PCs and foot parameters measured. The analysis revealed 3 PCs within the ankle plantarflexion and DVJ kinetics variables that captured more than 80% of the variability within the data, but none of them showed significant correlations ( ≤ 0.27) with any foot variables. While foot posture and foot morphological deformation remain of interest in characterising foot morphology across individuals, these findings highlight the lack of clinical relevance of these static evaluations at characterising lower limb and ankle performance.