The Effect of Ageing and Physical Activity Level on Muscle Fatigue during Isometric Contraction of Knee Extensor Muscles

Nahar, Nazmun 2013. Effect of ageing and physical activity level on muscle fatigue during isometric contraction of knee extensor muscles. Master’s theses in Biomechanics. Department of Biology of Physical Activity, University of Jyväskylä, Finland. Muscle fatigue is defined as the loss of force or power producing capacity in response to contractile activity and is a fundamental characteristic of skeletal muscle. The aim of this study was to identify whether time to failure remains same or increases in elderly people compared with young people. Another aim was to identify time to failure is same or less in active old people compared with inactive old people. One hundred and ten subjects were recruited in this study. However, complete data was obtained from ninety subjects [32 young (mean age 24±2 years), 28 old active (75±4 years) and 30 old inactive (75±3 years)]. Experimental protocol consisted of measurements before, during and after fatigue test. The electrical stimulation was induced every 10 sec of the fatigue test. To determine the stimulation intensity, double stimulus (doublet) was applied to the relaxed muscle that produced 30 % of maximal voluntary contraction (MVC). To determine the activation level 2×MVC was performed at 90◦ knee angle. During fatigue test, subjects performed sustained contraction at 50 % of the MVC as long as possible. The test was finished when the force dropped below 5 % of the target force. The results showed that following fatigue test there was no significant difference in time to failure between old and young subjects group. Habitual physical activity did not give any different results compared with old inactive subjects group following the fatigue test. Young subjects group had 18% (p<0.001) more peripheral fatigue and 0.6% (p<0.05) more central fatigue than old subjects group. These findings suggest that though the time to failure is similar in this study but it might be difference in mechanism of fatigue between old and young subjects.