Neuromuscular Fatigue: Age and Sex Differences

描述(申请人提供)：衰老与运动能力和认知功能的显著下降有关，肌肉骨骼紊乱和疼痛的增加，尤其是在女性。在接下来的30年里，美国65岁以上劳动力的数量将增加一倍以上，到2050年，老年人将占劳动力的25%。在低强度持续姿势收缩期间出现的神经肌肉疲劳(运动导致的力量丧失)和肌肉疼痛可能会很严重，并会增加与工作有关的任务中疼痛和受伤的风险。为了了解随年龄增长而加剧疲劳的潜在因素，这项建议研究了认知和遗传因素，这些因素在上肢静态姿势运动任务中导致更严重的神经肌肉疲劳和疼痛，尤其是在老年女性中。我们发现，在低强度持续上肢收缩期间，女性在执行具有挑战性和应激性的认知任务时，神经肌肉疲劳性和稳定性丧失比男性更严重。老龄化对老年女性的影响尚不清楚。因此，这项建议调查了在施加不同水平的认知压力/需求时，年龄和性别对持续姿势疲劳任务中运动表现和疼痛的影响。重要的是，载脂蛋白-E e4(ApoE E4)等位基因遗传会随着年龄的增长而传递更大的认知衰退风险，最近还与年龄相关的力量减弱有关。虽然神经肌肉疲劳会加剧老年人与年龄相关的力量衰退，而且可能对载脂蛋白e4遗传更敏感，但目前还没有关于遗传和疲劳的研究。这项建议还确定了载脂蛋白e4是否有助于老年人神经肌肉疲劳程度的差异。目的1将比较健康的年轻和老年男性和女性在存在和不存在认知应激源的情况下，在低强度姿势疲劳收缩上肢期间的神经肌肉疲劳和疼痛。我们假设，与年轻人相比，当认知需求增加时，老年人，特别是女性，在疲劳和疼痛方面会有更大的变化。目的2将确定APOE e4等位基因是否与老年男性和女性在低强度静态疲劳收缩期间神经肌肉疲劳和疼痛的年龄相关变化有关。我们假设，携带APOE e4等位基因的老年人将表现出最大的疲劳和疼痛。这项建议采用了一种创新的方法，通过确定认知和遗传因素，使老年人在持续姿势收缩期间容易出现运动能力下降、疲劳和疼痛增加的情况。识别老年人运动功能下降的风险因素将为临床医生提供一个理论基础，以便在大规模运动功能缺陷发生之前促进预防性干预，如练习或亚临床人群的认知和身体训练，从而增加劳动力的生产和有效时间，以及在老年时更独立、更健康的生活。 公共卫生相关性：这项建议调查了认知需求和遗传因素，这些因素可能在上肢静态持续姿势疲劳收缩期间导致更大的与年龄相关的神经肌肉疲劳和疼痛。持续的姿势收缩对于日常和人体工程学任务是必不可少的，而神经肌肉疲劳的增加使老年妇女在老龄化的劳动力中面临更大的肌肉骨骼损伤和疼痛风险。我们针对那些在遗传上有加速运动和认知衰退风险的老年人(载脂蛋白-E e4等位基因阳性)，以识别健康但亚临床的老年人，当认知需求被强加时，他们容易受到神经肌肉疲劳和疼痛的影响。这一结果将对肌肉骨骼疾病的治疗方法以及老龄化劳动力中的疼痛和康复产生重大影响。

DESCRIPTION (provided by applicant): Aging is associated with marked declines in motor performance and cognitive function, and an increase in musculoskeletal disorder and pain, especially in women. The number of Americans > 65 years in the workforce will more than double during the next 30 years so that older adults will comprise >25% of the workforce by 2050. Neuromuscular fatigue (exercise-induced loss of strength) and muscle pain that develops during low-intensity sustained postural contractions can be substantial and will increase risk of pain and injury during work-related tasks. To understand underlying factors that exacerbate fatigue with age, this proposal examines cognitive and genetic factors that contribute to greater neuromuscular fatigue and pain during static postural motor tasks of the upper limb especially in older women. We established that neuromuscular fatigability and loss of steadiness during low-intensity sustained upper limb contractions are greater for women than men when performing a challenging and stressful cognitive task. The impact of aging in older women is not known. This proposal therefore investigates the impact of age and sex on the impairment of motor performance and pain during a sustained postural fatiguing task when different levels of cognitive stress/demand are imposed. Importantly, Apolipoprotein-E e4 (APOE e4) allele inheritance conveys greater risk with increasing age of cognitive decline, and recently was associated with age-related reductions in strength. While neuromuscular fatigue exacerbates age-related decrements in strength in older adults and is likely more sensitive to APOE e4 inheritance, there are no studies addressing genetic inheritance and fatigue. This proposal also identifies whether APOE e4 contributes to differences in the magnitude of neuromuscular fatigue among older adults. Aim 1 will compare neuromuscular fatigue and pain during low-intensity postural fatiguing contractions of the upper limb in healthy young and older men and women in the presence and absence of a cognitive stressor. We hypothesize that older adults, especially women, will have greater changes in fatigue and pain when cognitive demand is increased compared with young adults. Aim 2 will determine whether the APOE e4 allele genotype is associated with age-related changes in neuromuscular fatigue and pain during low-intensity static fatiguing contractions among older men and women. We hypothesize that older adults who are APOE e4 allele carriers will exhibit the greatest fatigue and pain. This proposal adopts an innovative approach by identifying cognitive and genetic factors that predispose older adults to decrements in motor performance, increased fatigue and pain during sustained postural contractions. Identifying risk factors in older adults for motor decline will provide clinicians with a rationale to promote preventative interventions such as practice, or cognitive and physical training for sub-clinical populations before large motor function deficits occur, thus increasing productive and effective time in the work-force and more independent, healthy living in old age. PUBLIC HEALTH RELEVANCE: This proposal examines cognitive demand and genetic factors that can contribute to greater age-related neuromuscular fatigue and pain during static sustained postural fatiguing contractions of the upper limb. Sustained postural contractions are essential for daily and ergonomic tasks and increased neuromuscular fatigue place older women at greater risk of musculoskeletal injury and pain in an aging workforce. We target older adults who are genetically at risk of accelerated motor and cognitive decline (Apolipoprotein-E e4 allele positive) in order to identify healthy but subclinical older adults who are vulnerable to neuromuscular fatigue and pain when cognitive demand is imposed. The results will significantly impact treatment approaches to musculoskeletal disorders and pain and rehabilitation in an aging workforce.