Enhanced Concentric Torque After Eccentric Loading is A Positive Contributor to Dynamic Balance In Children

Abstract

<h3>Research Objectives</h3> To investigate if concentric torque is enhanced after eccentric loading at different velocities at the knee and ankle, and whether the enhanced concentric torques are related to dynamic balance in children. <h3>Design</h3> Cross-sectional study. <h3>Setting</h3> University laboratory. <h3>Participants</h3> Children (n=15; 40% male) ages 8-13 years (mean±SD=11.1±1.4 years). <h3>Interventions</h3> Not applicable. <h3>Main Outcome Measures</h3> We used FSST (rapid stepping while changing directions) to determine dynamic balance. A greater time taken to complete FSST indicates poor dynamic balance. Eccentric (ECC), concentric (CONC), and eccentric preloaded concentric (ECCCONC) muscle torque at the knee and ankle were assessed in a random order using the Biodex3 system at two velocities (120° and 180°/second). All torque measures were normalized for weight. Joint-specific enhanced concentric torque was calculated by subtracting CON from ECCCONC torque for each velocity. <h3>Results</h3> Joint-specific enhanced concentric torque after eccentric loading was observed at the ankle at both 120° and 180°/second (p< 0.01 for both) and at the knee at 120°/second (p< 0.01). Enhanced concentric torque at the ankle at 120°/second was negatively related to FSST (rspearman=-0.65, p=0.01). In separate partial correlation models, this relationship remained after controlling for age (rpartial=-0.81, p< 0.01), sex (rpartial=-0.73, p< 0.01), height (rpartial=-0.78, p< 0.01), and muscle strength of the knee (rpartial=-0.76, p< 0.01) and ankle (rpartial=-0.65, p=0.02). <h3>Conclusions</h3> Our study provides novel preliminary evidence of presence of joint-specific enhanced concentric torque in children. Enhanced concentric torque after eccentric loading at the ankle but not the knee is a positive, robust contributor to dynamic balance, independent of age, sex, height, and muscle strength of the knee and ankle, in children. It is plausible that eccentric-biased exercise training may improve dynamic balance in children warranting future investigations. <h3>Author(s) Disclosures</h3> The authors listed have no conflicts to disclose.