Fatigue when learning motor skills: When does it matter? Can it help?

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Whether it is in sports, at work or during rehabilitation, developing motor skills require the repetition of hundreds to thousands of movements. Such intensive training often leads to the development of fatigue. Our current understanding of the interactions between fatigue and motor learning remains limited. When does fatigue hinder motor learning? When can it help? Do motor skills learnt with fatigue transfer to testing conditions when an individual is rested? The long-term objective of my research program is to understand the interactions between fatigue and motor learning. Such knowledge is essential for coaches and therapists across Canada to optimize motor learning interventions. During the next five years, I will test the hypothesis that individuals experiencing fatigue during training will learn motor adaptation strategies to compensate for effects of fatigue on the sensorimotor system. These strategies will develop mostly if they contribute to a better performance during training. The impact of these strategies on performance when the individual is rested will depend on task characteristics. My first objective is to evaluate if penalising motor adaptations to fatigue during training will prevent their acquisition, retention and transfer. One of the most frequent motor adaptations to shoulder fatigue is an increase in trunk movements. Some authors believe that these adaptations are favourable while in other contexts they may be unwanted. Are these motor adaptations retained when a trainee learns new motor skills with fatigue? Is it possible for coaches and therapists to adjust training conditions so helpful adaptations are promoted while negative ones are discouraged? To evaluate this hypothesis, participants will train to a sequential shoulder abduction task with or without fatigue. For some participants, trunk movements will contribute to their performance while, for others, they will make the task more difficult. My second objective is to determine if fatigue experienced when learning to propel a wheelchair will lead to better propulsion techniques. During wheelchair propulsion, a greater involvement of trunk movements is advocated by training programs, is observed in expert users and is associated with a lower risk of developing shoulder pain. Learning to propel a wheelchair while experiencing shoulder fatigue may therefore lead to the development of better propulsion techniques. However, this favourable effect would be cancelled out if trunk movements are constraints as it would prevent the use of fatigue-induced motor adaptations. For this objective, healthy individuals will learn to propel a wheelchair at maximal speed on an ergometer while experiencing shoulder fatigue, or not. For some participants, trunk will be immobilised. In all studies, motor adaptations and performance will be evaluated with kinematic and electromyographic data during skill acquisition, retention and transfer. Sex sensitive analyses will be used.