RESEARCH ARTICLE


Peak Ground and Joint Forces in Step-Exercise Depending on Step-Pattern and Stepping-Rate



Rita Santos-Rocha1, 2, *, António Veloso2, MariaLourdes Machado2, Maria João Valamatos2, Carlos Ferreira2
1 Sport Sciences School of Rio Maior, Polytechnic Institute of Santarém, Portugal
2 Laboratory of Biomechanics, Faculty of Human Kinetics, Technical University of Lisbon, Portugal


© 2009 Santos-Rocha et al.

open-access license: This is an open access article distributed under the terms of the Creative Commons Attribution 4.0 International Public License (CC-BY 4.0), a copy of which is available at: https://creativecommons.org/licenses/by/4.0/legalcode. This license permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

* Address correspondence to this author at the AV BRASIL, 155, 7A, 1700-067, LISBON, Portugal; Tel: +351-966036856; Fax: +351-243999292; E-mail: rsantos@esdrm.pt


Abstract

The assessment of biomechanical loading is quite important for exercise prescription and injury prevention in the scope of Exercise Biomechanics. The study of ground reaction forces, joint forces and joint moments of force at ankle, knee and hip, allows the understanding of the magnitude of external and internal loading experienced by the lower extremity joints and the pattern of force-absorbing adjustments while performing a dynamic activity. The main purposes of this study were to compare the peak values of those forces, during the ascending and the descending phases of four Step-Exercise patterns (basic-step, knee-lift, run-step and knee-hop), performed at varying stepping-rate conditions (125, 130, 135 and 140 beats per minute), in a group of 18 skilled females. The results showed that vertical ground reaction forces and joint forces at ankle varied from: 1.6-1.7 BW (body weight) in basic-step, 1.3-1.6 BW in knee-lift, 1.7-2.1 BW in runstep and, 1.0-1.8 BW in knee-hop; vertical joint forces at knee and hip varied from: 1.5-1.7 BW in basic-step, 1.2-1.5 BW in knee-lift, 1.5-2.0 BW in run-step and, 0.8-1.8 BW in knee-hop. Significant greater values were found in run-step for all parameters. No significant differences were found among conditions of stepping-rate. The anterior-posterior forces varied from 0.2-0.6 BW considering the four movements. Significant greater values were found in the two propulsive movements. Also, these forces increased with faster stepping-rates. The joint moments of force varied from 0.1-1.0 Nm/BW considering the four movements. Significant greater values were found: at ankle, in basic-step and run-step; at knee, in run-step and knee-hop (ascending-phase); and at hip, in run-step. No significant differences were found among conditions of stepping-rate, at ankle and at knee (decending-phase). Joint moments increased with faster stepping-rates at knee (ascending-phase) and at hip. The results suggest that experienced steppers are capable of stepping at different cadences, with generally similar patterns of kinematics and kinetics. We concluded that lower extremity internal loading can be effectively controlled by varying stepping-rate during Step classes.

Keywords: Sports biomechanics, Exercise and health, Ground reaction forces, Joint forces, Moments of force.