Neuromuscular mechanisms for cold-induced changes in voluntary and involuntary muscle activity

每年有数百名加拿大人死于寒冷的暴露，通常是在冷水浸泡期间。通过了解我们身体对寒冷的生理反应，可以改善生存和康复。我的研究项目侧重于有助于提高体能和在寒冷中生存的生理机制。因此，我打算进一步研究寒冷导致的自主肌肉活动减少和非自愿颤抖的机制和影响。肌肉活动的磁刺激(MS)和电刺激(ES)将识别局部肌肉和/或身体核心冷却对兴奋性和抑制性神经通路的影响。经颅多发性硬化症(位于颅顶)刺激从皮质脊髓神经元到运动神经元再到肌肉的整个运动通路。颈髓ES(位于颅底)能特异性刺激脊髓运动神经元。我们还将专门探讨在短暂和疲劳的随意肌肉收缩过程中冷却身体核心和/或局部肌肉的效果。因此，我们可以区分局部神经回路和中枢神经回路，以及它们是兴奋的还是抑制的，并确定每个回路的比例贡献。这些技术还将有助于确定导致次极大抖动强度的中央机制，即使在核心温度下降的情况下(这种情况下，人们预计会有最大的反应，但事实并非如此)。在这个研究项目的许多研究中，我们将确定性别是否对反应有影响。这些结果可能会指导未来的研究，使肌肉在冷水生存情况下最大限度地收缩和颤抖。最后，如果存在性别影响，女性数据可能会被用来改进加拿大海岸警卫队使用的寒冷生存模型。我打算在未来5年内培养8-10名HQP，他们将成为运动科学家、大学教授、内科医生和理疗师。这些HQP中的一些人将参与教学或辅导，这些主题将提高表现、安全参与和在极端环境中的生存。

Hundreds of Canadians die annually from cold exposure, often during cold-water immersion. Survival and recovery can be improved by understanding our body's physiological responses to cold. My research program focuses on physiologic mechanisms contributing to enhancing physical performance and survival in the cold. Thus, I intend to further study mechanisms for, and implications of cold-induced reduction in voluntary muscle activity and involuntary shivering. Magnetic stimulation (MS) and electrical stimulation (ES) of muscle activity, will identify effects of local muscle and/or body core cooling on excitatory and inhibitory neural pathways. Transcranial MS (at the top of the skull) stimulates the entire motor pathway from corticospinal neurons, to motor neuron, to muscle. Cervico-medullary ES (at the base of the skull) specifically stimulates spinal motor neurons. We will also specifically explore the effects of cooling the body core and/or the local muscle during brief and fatiguing voluntary muscle contractions. Therefore, we can differentiate between local and central neural circuits and whether they are excitatory or inhibitory, and determine the proportional contribution of each. These techniques will also help determine central mechanisms that account for submaximal shivering intensity, even when core temperature is decreasing (a condition when one would expect a maximal response but it is not). During many of the studies in this research program, we will determine if there is an effect of sex on the responses. Results could direct future research to maximize muscle contraction and shivering during cold-water survival situations. Finally, if there are sex effects, female data may be used to improve cold survival models used by the Canadian Coast Guard. I intend to train 8-10 HQP in the next 5 years, who will become exercise scientists, university professors, physicians and physiotherapists. Some of these HQP will be involved in teaching or coaching on topics that will improve both performance, safe participation and survival in extreme environments.