Rui Wu1, Eamonn Delahunt2, Massimiliano Ditroilo2, Madeleine M Lowery3, Ricardo Segurado4, Giuseppe De Vito2. 1. School of Public Health, Physiotherapy and Sports Science, University College Dublin, Dublin, Ireland. Electronic address: rui.wu@ucd.ie. 2. School of Public Health, Physiotherapy and Sports Science, University College Dublin, Dublin, Ireland; Institute for Sport and Health, University College Dublin, Dublin, Ireland. 3. School of Electrical & Electronic Engineering, University College Dublin, Dublin, Ireland. 4. School of Public Health, Physiotherapy and Sports Science, University College Dublin, Dublin, Ireland.
Abstract
PURPOSE: This study investigated the effect of knee joint angle and age on torque steadiness of knee extensors (KE) at varying submaximal isometric contractions. METHODS: 22 young (24.0 ± 2.6 years; 11 women) and 22 older (69.4 ± 2.4 years; 10 women) healthy men and women participated. Maximal voluntary isometric contraction (MVIC) of the KE and flexors was examined at 90° and 60° of knee flexion (0° = full extension). At each angle, participants performed KE isometric contractions (20%, 50% and 80% MVIC) to evaluate torque steadiness, whereas surface EMG was concurrently acquired from the vastus lateralis and biceps femoris muscles. RESULTS: Age-related impairment in torque steadiness was observed only at 20% MVIC (p < 0.01). A lower level of steadiness (p < 0.001) with a higher level of agonist and antagonist activations (all p < 0.01) was observed at 90° of knee flexion in comparison with contractions at 60°. Young participants were less steady when performing contractions at 90° compared with contractions at 60° of flexion (p < 0.001), whereas there was no difference for older participants. Furthermore, a significant effect of agonist activation and antagonist co-activation on torque steadiness was observed, but only in young participants (all p < 0.05). CONCLUSIONS: These findings suggest that: (1) knee joint angle affects torque steadiness differently in young and older individuals; (2) an age-related impairment in steadiness was only presented at the lowest considered contraction intensity; and (3) the muscle activation responses were not associated with steadiness in older individuals.
PURPOSE: This study investigated the effect of knee joint angle and age on torque steadiness of knee extensors (KE) at varying submaximal isometric contractions. METHODS: 22 young (24.0 ± 2.6 years; 11 women) and 22 older (69.4 ± 2.4 years; 10 women) healthy men and women participated. Maximal voluntary isometric contraction (MVIC) of the KE and flexors was examined at 90° and 60° of knee flexion (0° = full extension). At each angle, participants performed KE isometric contractions (20%, 50% and 80% MVIC) to evaluate torque steadiness, whereas surface EMG was concurrently acquired from the vastus lateralis and biceps femoris muscles. RESULTS: Age-related impairment in torque steadiness was observed only at 20% MVIC (p < 0.01). A lower level of steadiness (p < 0.001) with a higher level of agonist and antagonist activations (all p < 0.01) was observed at 90° of knee flexion in comparison with contractions at 60°. Young participants were less steady when performing contractions at 90° compared with contractions at 60° of flexion (p < 0.001), whereas there was no difference for older participants. Furthermore, a significant effect of agonist activation and antagonist co-activation on torque steadiness was observed, but only in young participants (all p < 0.05). CONCLUSIONS: These findings suggest that: (1) knee joint angle affects torque steadiness differently in young and older individuals; (2) an age-related impairment in steadiness was only presented at the lowest considered contraction intensity; and (3) the muscle activation responses were not associated with steadiness in older individuals.
Authors: Sasha N Zill; Chris J Dallmann; Nicholas S Szczecinski; Ansgar Büschges; Josef Schmitz Journal: J Neurophysiol Date: 2021-06-09 Impact factor: 2.974