Agonist versus antagonist muscle fatigue effects on thigh muscle activity and vertical ground reaction during drop landing

Kellis, Eleftherios; Kouvelioti, Vasiliki

doi:10.1016/j.jelekin.2007.08.002

« Previous Next »Journal of Electromyography and Kinesiology
Volume 19, Issue 1 , Pages 55-64, February 2009

Agonist versus antagonist muscle fatigue effects on thigh muscle activity and vertical ground reaction during drop landing

Laboratory of Neuromuscular Control and Therapeutic Exercise, Department of Physical Education and Sports Sciences at Serres Aristotle University of Thessaloniki, TEFAA Serres, Serres 62100, Greece

Received 11 May 2007; received in revised form 3 August 2007; accepted 3 August 2007. published online 24 September 2007.

Abstract

Background

Agonist and antagonist co-activation plays an important role for stabilizing the knee joint, especially after fatigue. However, whether selective fatigue of agonists or antagonist muscles would cause different changes in muscle activation patterns is unknown.

Hypothesis

Knee extension fatigue would have a higher influence on landing biomechanics compared with a knee flexion protocol.

Study design

Repeated-measures design.

Methods

Twenty healthy subjects (10 males and 10 females) performed two sets of repeated maximal isokinetic concentric efforts of the knee extensors (KE) at 120°s⁻¹ until they could no longer consistently produce 30% of maximum torque. On a separate day, a similar knee flexion (KF) fatigue protocol was also performed. Single leg landings from 30cm drop height were performed before, in the middle and after the end of the fatigue test. The mean normalized electromyographic (EMG) signal of the vastus medialis (VM), vastus lateralis (VL), biceps femoris (BF) and gastrocnemius (GAS) at selected landing phases were determined before, during and after fatigue. Quadriceps:hamstrings (Q:H) EMG ratio as well as sagittal hip and knee angles and vertical ground reaction force (GRF) were also recorded.

Results

Two-way analysis of variance designs showed that KE fatigue resulted in significantly lower GRF and higher knee flexion angles at initial contact while maximum hip and knee flexion also increased (p<0.05). This was accompanied by a significant decline of BF EMG, unaltered EMG of vastii and GAS muscles and increased Q:H ratio. In contrast, KF fatigue had no effects on vGRFs but it was accompanied by increased activation of VM, BF and GAS while the Q:H increased during before landing and decreased after impact.