Year

2010

Degree Name

Masters by Research

Department

School of Health Sciences

Abstract

The primary aim of this thesis was to determine if a laser–based mechanomyogram (MMG) is able to detect alteration to the contractile capability of skeletal muscle following the onset and subsequent recovery from injury. MMG represents the mechanical equivalent of electromyography, the electrical activity of a contracting muscle. As the motor units of the muscle are activated, the overall length of the muscle shortens due to the mechanical processes of actin and myosin cross-bridge formation. This cross-bridge formation leads to a subsequent increase in muscle belly diameter as the muscle shortens and thickens. While the literature pertaining to MMG is replete with observations that changes in muscle belly diameter may be used to assess skeletal muscle injury these observations have been on data derived from investigations that have used models of fatigue or pre-existing disease states within muscle. Therefore, the studies used to substantiate the recommendations for MMG use in injury measurement does not match with the current levels of evidence coming from the scientific community. Two studies were undertaken to determine if MMG was able to detect alterations to the contractile capability of skeletal muscle due to experimentally induced injuries. The first study utilised a low–grade muscle–strain injury induced by eccentric exercise resulting in Delayed Onset of Muscle Soreness (DOMS) in a human biceps brachii muscle. MMG was able to detect alterations and subsequent recovery of the muscle’s contractile capabilities that corresponded to published scientific literature in the area of DOMS onset and recovery. These results indicated that MMG may have a role in detecting altered contractile deficits in more severe skeletal muscle injuries. The second experiment utilised a more severe Grade–II myotoxic induced injury in a rat gastrocnemius muscle. MMG was able to detect alterations and subsequent recovery of V the rat gastrocnemius muscle’s contractile capabilities that corresponded to known histological and functional injury recovery timelines. The results of these two experiments indicate that MMG is able to non–invasively detect the onset and recovery of muscle contractile capabilities in both a low–grade and a high–grade muscle strain injury.

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