Effect of cross-over fatigue on posture

Arora, Shruti (2013) Effect of cross-over fatigue on posture. Masters thesis, Memorial University of Newfoundland.

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Abstract

Research has shown that local fatigue occurring in an exercised limb can result in force loss in the same muscle of the non-exercised limb. This proposed cross-over effect of fatigue has been identified in muscles of the upper and lower limb and also in muscles that are not directly related to the fatigue (i.e. right quadriceps femoris fatigued and effects are noted in left and right biceps brachii and dorsal interosseous muscle). Studies published to date have also examined the effects of age and gender on cross-over fatigue. Not all studies, however, have confirmed the existence of cross-over fatigue in the nonexercised limb. The discrepancy in results (i.e. some studies finding cross-over fatigue and others not) may be attributed to the variety of outcome measures examined, the intensity at which the fatiguing contractions were performed, the type of fatiguing task and the specific muscle studied. -- So far most studies have examined strength deficits created by this cross-over fatigue. Little attention has been paid to the effect of this type of fatigue on the body's ability to control movement. To the best of our knowledge there is only one study which has examined the effects of cross-over fatigue on balance. These researchers fatigued the quadriceps femoris on one side and measured balance of the non-fatigued leg during single leg standing pre- and post-fatigue protocol. Their study showed that balance, while standing on the non-exercised leg, was disturbed after the fatiguing protocol. At present it remains unknown whether these changes in non-exercised limb balance were due to the alterations in quadriceps femoris function or whether the fatigue affected the activation patterns and force production of other lower limb muscles. Based on this unanswered question this thesis aimed to replicate the previous balance related fatigue research, while adding a full analysis of lower limb muscle activity to assess how knee extensors fatigue on one side affected the non-exercised leg standing balance and muscle activation patterns. The fatigue protocol incorporated 15 consecutive isometric contractions of 16 sec each, which were performed at 30% peak force for the dominant knee extensors. The experimental protocol consisted of pre-fatigue balance trials, warm-up exercises, maximum voluntary isometric contractions, fatigue protocol, and post-fatigue balance trials. The pre- and post-fatigue balance trials consisted of transition from double to single leg standing and single leg standing trials. The study found no cross-over fatigue effects and it is hypothesized that the intensity and the duration of the fatigue protocol incorporated in the present study might have accounted for the lack of cross-over fatigue effects.

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