Principal Investigator (Last, First): Amann, Markus ABSTRACT Patients with COPD are limited in their daily activities because of exercise limitation that can be sufficiently severe to impair simple everyday tasks. The proposed research will examine novel mechanisms that might contribute to this severe limitation in exercise tolerance and also determine how exercise tolerance might be improved. Specifically, we will assess the role of excessive respiratory muscle work, a characteristic of COPD patients, and elevated oxidative stress during exercise in this population. Additionally, we will assess whether the increased work of breathing is a significant contributor to the increased levels of oxidative stress during exercise in patients with COPD. We will a) use a mechanical ventilator in combination with a reduced density gas mixture to reduce the work of breathing during cycle exercise and b) use venous infusion of vitamin C during cycle exercise to examine the effects of both, the reduced work of breathing and the reduced oxidative stress on muscle fatigue in the exercising legs. We will use a novel combination of methods to provide a sensitive, reproducible, objective means of quantifying limb muscle fatigue. We will further examine whether these proposed effects on limb fatigue are, in part, due to blood flow and oxygen (O2) transport to the limbs and how this is influenced by the work of breathing and oxidative stress. In healthy subjects it has been shown that a reduction in respiratory muscle work increases blood flow and O2 transport to the limbs. Also in healthy subjects, we have recently revealed that increases in blood flow / O2 transport to the working legs significantly reduces muscle fatigue and improves exercise tolerance. Furthermore, it has been shown that a reduction in oxidative stress also increases blood flow / O2 delivery during exercise in older healthy individuals, however, there are currently no data on the effects of oxidative stress on limb blood flow / O2 transport in COPD patients during exercise. In view of the significantly increased work of breathing required during exercise and the substantially increased oxidative stress in COPD patients, we expect the effects of reducing the impact of these factors on limb muscle fatigue to be even greater than in healthy subjects. We propose that this research will provide new effective methods to improve exercise capacity during the rehabilitation of patients with COPD by allowing them to improve endurance of their locomotor muscles. It is anticipated that this improvement in the rehabilitation process will prevent the deterioration of muscle function which is currently prevalent in the sedentary COPD population.
Principal Investigator (Last, First): Amann, Markus Relevance to Public Health We propose that this research will provide new effective methods to improve exercise capacity during the rehabilitation of patients with COPD by allowing them to improve endurance of their locomotor (leg) muscles. It is anticipated that this improvement in the rehabilitation process will prevent the deterioration of muscle function which is currently prevalent in the sedentary COPD population.
|Taylor, Janet L; Amann, Markus; Duchateau, Jacques et al. (2016) Neural Contributions to Muscle Fatigue: From the Brain to the Muscle and Back Again. Med Sci Sports Exerc 48:2294-2306|
|Blain, Gregory M; Mangum, Tyler S; Sidhu, Simranjit K et al. (2016) Group III/IV muscle afferents limit the intramuscular metabolic perturbation during whole body exercise in humans. J Physiol 594:5303-15|
|Sidhu, Simranjit K; Weavil, Joshua C; Venturelli, Massimo et al. (2015) Aging alters muscle reflex control of autonomic cardiovascular responses to rhythmic contractions in humans. Am J Physiol Heart Circ Physiol 309:H1479-89|
|Amann, Markus; Sidhu, Simranjit K; Weavil, Joshua C et al. (2015) Autonomic responses to exercise: group III/IV muscle afferents and fatigue. Auton Neurosci 188:19-23|
|Weavil, J C; Sidhu, S K; Mangum, T S et al. (2015) Intensity-dependent alterations in the excitability of cortical and spinal projections to the knee extensors during isometric and locomotor exercise. Am J Physiol Regul Integr Comp Physiol 308:R998-1007|
|Broxterman, Ryan M; Richardson, Russell S; Amann, Markus (2015) Less peripheral fatigue after prior exercise is not evidence against the regulation of the critical peripheral fatigue threshold. J Appl Physiol (1985) 119:1520|
|Pollak, Kelly A; Swenson, Jeffrey D; Vanhaitsma, Timothy A et al. (2014) Exogenously applied muscle metabolites synergistically evoke sensations of muscle fatigue and pain in human subjects. Exp Physiol 99:368-80|
|Sidhu, Simranjit K; Weavil, Joshua C; Venturelli, Massimo et al. (2014) Spinal Î¼-opioid receptor-sensitive lower limb muscle afferents determine corticospinal responsiveness and promote central fatigue in upper limb muscle. J Physiol 592:5011-24|
|Goodall, S; Twomey, R; Amann, M et al. (2014) AltitudeOmics: exercise-induced supraspinal fatigue is attenuated in healthy humans after acclimatization to high altitude. Acta Physiol (Oxf) 210:875-88|
|Amann, Markus; Venturelli, Massimo; Ives, Stephen J et al. (2014) Group III/IV muscle afferents impair limb blood in patients with chronic heart failure. Int J Cardiol 174:368-75|
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