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Muscle fatigue and Muscle fibre type

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Muscle fatigue and Muscle fibre type Introduction The objective of this lab report was to investigate the relationship between muscle fatigue and the proportion of fast twitch fibres. Human muscles are made up of a mixture of different fibre types: Fast Twitch oxidative, Fast twitch oxidative Glycolytic and Slow Twitch. The method used was action potential propagation velocity of motor axons in the ulnar nerve. The conduction velocity in a nerve is the speed at which the impulse travels along it. "The larger the diameter of the fibre the faster the nerve impulse will travel." "Each action potential arriving in the motor nerve always produces a muscle action potential, which then spreads along the membrane of the muscle fibre giving rise to a contraction of that fibre. Because of their relatively small size, it is difficult to record the electrical activity of nerve fibres themselves at the surface of skin close to the fibre. This problem can be overcome by recording the electrical activity of the muscle fibres innervated by the nerve instead."(Physiolgical systems accessed on 21/11/04).,The electromyogram (EMG) ...read more.


Figure 2 - Time versus interelectrode distance The graph shows that further up the ulnar nerve the greater the distance the greater the time it takes. The relationship show that time it takes to travel is very quick. Figure 3 - Conduction velocity and muscle fatigue Shows a random set of results with no really relationship, the R values show that there is little correlation between fatigue and conduction velocity. Discussion Figure 1- The increase in EMG might reflect greater total muscle fiber recruitment for a fixed submaximal external force and is defined as fibers fatigue (Edwards 1981, NewhamDJ et al 1983).6. (Edwards RH, 1981, pp. 1-18.) It is when the motor units fall to contract that muscle starts to fatigue. So because it was a fixed force and isometric contraction the muscle does not start to fatigue. Figure 2 - The graphs shows the time and distance, when looking at the gradient of the slopes they are a bit high. In terms of the muscle contracting is nearly 100 ms-1. ...read more.


.( Stephen Wright) Subjective fatigue So far we've been dealing with objective measures of fatigue; i.e. a decrease in the tension developed by the muscle. But this is only one contribution to subjective fatigue---the feeling of muscle tiredness. In fact if one records from biceps or triceps brachii while a subject is carrying a load, one finds that the muscles are inactive. They are electrically inactive and develop no active tension. However, the subjects rapidly feel fatigue in the muscle; these feelings presumably originate from nociceptors or mechanoreceptors in the muscles, ligaments or joints. But of course this is a subjective measure of fatigue, and not related to the capacity of the muscle of develop tension. (Basmajian 4th ed. p164). Reference 1) (Basmajian.4thed.p164).http://anatomy.med.unsw.edu.au/teach/anat3141/2002/FA2_16=MUSCLE3.pdf [accessed at http://www.med.ege.edu.tr/~norolbil/2000/NBD10900.html] 2) Edwards RH, Human muscle function and fatigue. Human muscle fatigue:physiological mechanisms. Pitman Medical, London (Ciba Foundationsymposium 82) 1981, pp. 1-18. [accessed at http://dahweb.engr.ucdavis.edu/dahweb/228site/chp10.pdf] 3) JP/0111 PHYSIOLOGICAL SYSTEMS/ PLP1 Measurement of Nerve Conduction Velocity in the Human Forearm. [accessed at http://www.kcl.ac.uk/kis/schools/life_sciences/biomed/physiol/JP111/2002_2003/JP111%200203%20Prac1%20Conduction%20Velocity.pdf] 4) Stephen Wright, Ph.D., 16. ACTION POTENTIAL PROPAGATION Department of Physiology [accessed at http://human.physiol.arizona.edu/sched/cv/wright/16action.htm ...read more.

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