Abstract

Objective: Impaired biomechanics and neuromuscular control have been suggested as probable links to female sex bias in the onset of patellofemoral pain syndrome (PFPS). There are limited objective, clinical measures for assessment of impaired biomechanics and neuromuscular control. The primary objective of this investigation was to examine sex differences in vertical ground reaction force (vGRF) and force loading rate in young athletes performing maximum, repeated vertical single-leg hops (RVSH). We hypothesized that females would demonstrate greater vGRF and force loading rate than males and females would show inter-limb differences in force attenuation.

Design: Cross-Sectional Study.

Setting: Pediatric sports medicine clinic.

Participants: One hundred-nine healthy high-school, soccer and basketball athletes.

Assessment of risk factors: Participants performed RVSH for 15 seconds on a portable forceplate with a sampling rate of 400 Hz (Accupower; AMTI, Watertown, MA).

Main outcome measurements: Raw vGRF was filtered with a generalized cross-validation (GCV) spline using a 50 Hz cut-off frequency, and then normalized to potential energy (PE). Force loading rate was calculated by dividing normalized vGRF by time to peak force. Group means were compared using ANOVA.

Results: Females demonstrated significantly greater normalized vGRF (p < 0.001) and force loading rate (p <0.001) during landing than their male counterparts. Neither sex demonstrated significant inter-limb differences in force attenuation (p>0.05).

Conclusions: Female athletes may have altered force attenuation capability during RVSH as identified by increased vGRF and force loading rate compared to male athletes. Portable forceplates may be potential tools to identify altered force attenuation in clinical settings.