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Effect of Fatigue on Muscle Mechanics: An Insight into Muscle Strain Injury
It is widely accepted that muscle strain injuries are most likely to occur during eccentric muscle contractions, when muscles are active while lengthening. For example, hamstring muscle strains are likely to occur in the terminal swing phase of the gait cycle, when the hamstring muscles act eccentrically to decelerate the forward motion of the leg, or when absorbing energy during the stance phase. Therefore, it is not surprising that two prominent theories for the mechanism of strain injuries are based on: 1) the force-length (F-L) relationship; and 2) the energy absorption capacity of the muscle. This study will investigate the effects of fatigue on both the F-L relationship and energy absorption capacity of the medial gastocnemius (MG) muscle. Furthermore, the effects of fatigue on skeletal muscle function will be examined during precisely controlled movement tasks and also during dynamic functional tasks.
Muscle strain injuries comprise the majority of musculoskeletal injuries in field sport and impact the health care system, both directly and indirectly by reducing participation in health and fitness programs. Although fatigue has been proposed as a major factor increasing the risk of sustaining a muscle strain injury, the effect of fatigue on human muscle function and its contribution to muscle strain injuries is still relatively poorly understood. For this reason, knowledge of the fundamental biomechanical and physiological changes that occur during fatigue needs to be established. Following this, a better understanding of how a muscle performs under fatigue in functional situations, such as those in which injuries commonly occur, will provide valuable information into the causal mechanisms and ultimately the development of preventative training strategies that can reduce the incidence of muscle strain injuries.