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Michael N Sawka - One of the best experts on this subject based on the ideXlab platform.
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performance in the heat physiological factors of importance for hyperthermia Induced Fatigue
Comprehensive Physiology, 2014Co-Authors: Lars Nybo, Peter Rasmussen, Michael N SawkaAbstract:This article presents a historical overview and an up-to-date review of hyperthermia-Induced Fatigue during exercise in the heat. Exercise in the heat is associated with a thermoregulatory burden which mediates cardiovascular challenges and influence the cerebral function, increase the pulmonary ventilation, and alter muscle metabolism; which all potentially may contribute to Fatigue and impair the ability to sustain power output during aerobic exercise. For maximal intensity exercise, the performance impairment is clearly influenced by cardiovascular limitations to simultaneously support thermoregulation and oxygen delivery to the active skeletal muscle. In contrast, during submaximal intensity exercise at a fixed intensity, muscle blood flow and oxygen consumption remain unchanged and the potential influence from cardiovascular stressing and/or high skin temperature is not related to decreased oxygen delivery to the skeletal muscles. Regardless, performance is markedly deteriorated and exercise-Induced hyperthermia is associated with central Fatigue as indicated by impaired ability to sustain maximal muscle activation during sustained contractions. The central Fatigue appears to be influenced by neurotransmitter activity of the dopaminergic system, but inhibitory signals from thermoreceptors arising secondary to the elevated core, muscle and skin temperatures and augmented afferent feedback from the increased ventilation and the cardiovascular stressing (perhaps baroreceptor sensing of blood pressure stability) and metabolic alterations within the skeletal muscles are likely all factors of importance for afferent feedback to mediate hyperthermia-Induced Fatigue during submaximal intensity exercise. Taking all the potential factors into account, we propose an integrative model that may help understanding the interplay among factors, but also acknowledging that the influence from a given factor depends on the exercise hyperthermia situation.
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performance in the heat physiological factors of importance for hyperthermia Induced Fatigue
Comprehensive Physiology, 2014Co-Authors: Lars Nybo, Peter Rasmussen, Michael N SawkaAbstract:This article presents a historical overview and an up-to-date review of hyperthermia-Induced Fatigue during exercise in the heat. Exercise in the heat is associated with a thermoregulatory burden which mediates cardiovascular challenges and influence the cerebral function, increase the pulmonary ventilation, and alter muscle metabolism; which all potentially may contribute to Fatigue and impair the ability to sustain power output during aerobic exercise. For maximal intensity exercise, the performance impairment is clearly influenced by cardiovascular limitations to simultaneously support thermoregulation and oxygen delivery to the active skeletal muscle. In contrast, during submaximal intensity exercise at a fixed intensity, muscle blood flow and oxygen consumption remain unchanged and the potential influence from cardiovascular stressing and/or high skin temperature is not related to decreased oxygen delivery to the skeletal muscles. Regardless, performance is markedly deteriorated and exercise-Induced hyperthermia is associated with central Fatigue as indicated by impaired ability to sustain maximal muscle activation during sustained contractions. The central Fatigue appears to be influenced by neurotransmitter activity of the dopaminergic system, but inhibitory signals from thermoreceptors arising secondary to the elevated core, muscle and skin temperatures and augmented afferent feedback from the increased ventilation and the cardiovascular stressing (perhaps baroreceptor sensing of blood pressure stability) and metabolic alterations within the skeletal muscles are likely all factors of importance for afferent feedback to mediate hyperthermia-Induced Fatigue during submaximal intensity exercise. Taking all the potential factors into account, we propose an integrative model that may help understanding the interplay among factors, but also acknowledging that the influence from a given factor depends on the exercise hyperthermia situation. © 2014 American Physiological Society. Compr Physiol 4:657-689, 2014.
Jose Oliveira - One of the best experts on this subject based on the ideXlab platform.
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joint position sense is altered by football pre participation warm up exercise and match Induced Fatigue
Knee, 2015Co-Authors: Eduardo Salgado, Fernando Ribeiro, Jose OliveiraAbstract:Abstract Background The demands to which football players are exposed during the match may augment the risk of injury by decreasing the sense of joint position. This study aimed to assess the effect of pre-participation warm-up and Fatigue Induced by an official football match on the knee-joint-position sense of football players. Methods Fourteen semi-professional male football players (mean age: 25.9 ± 4.6 years old) volunteered in this study. The main outcome measures were rate of perceived exertion and knee-joint-position sense assessed at rest, immediately after a standard warm-up (duration 25 min), and immediately after a competitive football match (90 minutes duration). Results Perceived exertion increased significantly from rest to the other assessments (rest: 8.6 ± 2.0; after warm-up: 12.1 ± 2.1; after football match: 18.5 ± 1.3; p Conclusions The results indicate that knee-joint-position sense acuity was increased by pre-participation warm-up exercise and was decreased by football match-Induced Fatigue. Clinical relevance: Warm-up exercises could contribute to knee injury prevention, whereas the deleterious effect of match-Induced Fatigue on the sensorimotor system could ultimately contribute to knee instability and injury.
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effect of exercise Induced Fatigue on position sense of the knee in the elderly
European Journal of Applied Physiology, 2007Co-Authors: Fernando Ribeiro, Jorge Mota, Jose OliveiraAbstract:Previously, data on the effects of muscle Fatigue on joint position sense (JPS) have been provided. However, to our knowledge, no studies have been conducted so far to assess the effects of local muscle Fatigue on elderly proprioception. Thus, the purpose of the present study was to determine the effects of local muscle Fatigue on knee JPS in old-age-subjects. Sixteen male volunteers (mean age +/- SD: 69.81 +/- 3.92 years) participated in this study. Each subject completed all of the data collection in one morning session; JPS measures were obtained prior to and immediately after the Fatigue protocol. JPS was evaluated by the technique of open-kinetic chain and active knee positioning, and was reported using absolute, relative and variable angular errors. The Fatigue protocol applied to the lower extremity consisted of 30 maximum concentric repetitions of the knee extensors and flexors muscles on an isokinetic dynamometer at an angular velocity of 120 s(-1) (2.09 rad s(-1)). The results showed that peak torque of knee extensor and flexor muscles was significantly decreased from rest to post exercise-Induced Fatigue. After local load to the knee muscles, a significant increase of absolute angular error was observed (2.56 degrees ). The relative error showed the directional bias in the extension movement. However, the reliability and accuracy of estimating knee angles as showed by the variable error is similar at both times. It can be concluded that exercise-Induced local muscle Fatigue alters knee JPS in old age adults.
Fang Fang - One of the best experts on this subject based on the ideXlab platform.
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domain structure evolution and Fatigue cracking of 001 oriented pb mg1 3nb2 3 o3 0 67 pbtio3 0 33 ferroelectric single crystals under cyclic electric loading
Applied Physics Letters, 2007Co-Authors: Fang Fang, Weiyou Yang, F C Zhang, H QingAbstract:The authors report on the electrically Induced Fatigue cracking and phase transition behavior for ⟨001⟩-oriented [Pb(Mg1∕3Nb2∕3)O3]0.67(PbTiO3)0.33 (PMN-PT 67∕33) ferroelectric single crystals under cyclic electric field. For crystals with initial cracks, crack growth and deviation are associated with the transition from the rhombohedral to the tetragonal phase, even though the peak value of the applied cyclic electric field is below the coercive field (Ec). For crystals without initial cracks, numerous microcracks are developed in the crystal as a result of 71° domain switching.
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Fatigue crack growth for batio3 ferroelectric single crystals under cyclic electric loading
Journal of the American Ceramic Society, 2005Co-Authors: Fang Fang, Weiyou Yang, Fang Zhang, H S LuoAbstract:Electrically Induced Fatigue crack growth is an important degradation mechanism for ferroelectric devices. Reliability concerns for ferroelectric devices place stringent demands for ferroelectric materials. In situ observation of electrically Induced Fatigue crack growth was carried out for ferroelectric single crystals under alternating electric field. Electrically Induced Fatigue crack growth was observed both below and above the coercive field. Crack closure and open behavior were observed together with 90° ferroelectric domain switching during the electric cycling. The crack propagation behavior is a repeated process of continuous but small increments followed by a sudden increase in the crack length. It was suggested that the electric boundary condition along the crack face, from its mouth to its tip, is a variation from the impermeable to the permeable state. The gradual attainment of an impermeable crack tip after an incubation period of field cycling causes the observed jump in crack propagation.
Lars Nybo - One of the best experts on this subject based on the ideXlab platform.
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performance in the heat physiological factors of importance for hyperthermia Induced Fatigue
Comprehensive Physiology, 2014Co-Authors: Lars Nybo, Peter Rasmussen, Michael N SawkaAbstract:This article presents a historical overview and an up-to-date review of hyperthermia-Induced Fatigue during exercise in the heat. Exercise in the heat is associated with a thermoregulatory burden which mediates cardiovascular challenges and influence the cerebral function, increase the pulmonary ventilation, and alter muscle metabolism; which all potentially may contribute to Fatigue and impair the ability to sustain power output during aerobic exercise. For maximal intensity exercise, the performance impairment is clearly influenced by cardiovascular limitations to simultaneously support thermoregulation and oxygen delivery to the active skeletal muscle. In contrast, during submaximal intensity exercise at a fixed intensity, muscle blood flow and oxygen consumption remain unchanged and the potential influence from cardiovascular stressing and/or high skin temperature is not related to decreased oxygen delivery to the skeletal muscles. Regardless, performance is markedly deteriorated and exercise-Induced hyperthermia is associated with central Fatigue as indicated by impaired ability to sustain maximal muscle activation during sustained contractions. The central Fatigue appears to be influenced by neurotransmitter activity of the dopaminergic system, but inhibitory signals from thermoreceptors arising secondary to the elevated core, muscle and skin temperatures and augmented afferent feedback from the increased ventilation and the cardiovascular stressing (perhaps baroreceptor sensing of blood pressure stability) and metabolic alterations within the skeletal muscles are likely all factors of importance for afferent feedback to mediate hyperthermia-Induced Fatigue during submaximal intensity exercise. Taking all the potential factors into account, we propose an integrative model that may help understanding the interplay among factors, but also acknowledging that the influence from a given factor depends on the exercise hyperthermia situation.
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performance in the heat physiological factors of importance for hyperthermia Induced Fatigue
Comprehensive Physiology, 2014Co-Authors: Lars Nybo, Peter Rasmussen, Michael N SawkaAbstract:This article presents a historical overview and an up-to-date review of hyperthermia-Induced Fatigue during exercise in the heat. Exercise in the heat is associated with a thermoregulatory burden which mediates cardiovascular challenges and influence the cerebral function, increase the pulmonary ventilation, and alter muscle metabolism; which all potentially may contribute to Fatigue and impair the ability to sustain power output during aerobic exercise. For maximal intensity exercise, the performance impairment is clearly influenced by cardiovascular limitations to simultaneously support thermoregulation and oxygen delivery to the active skeletal muscle. In contrast, during submaximal intensity exercise at a fixed intensity, muscle blood flow and oxygen consumption remain unchanged and the potential influence from cardiovascular stressing and/or high skin temperature is not related to decreased oxygen delivery to the skeletal muscles. Regardless, performance is markedly deteriorated and exercise-Induced hyperthermia is associated with central Fatigue as indicated by impaired ability to sustain maximal muscle activation during sustained contractions. The central Fatigue appears to be influenced by neurotransmitter activity of the dopaminergic system, but inhibitory signals from thermoreceptors arising secondary to the elevated core, muscle and skin temperatures and augmented afferent feedback from the increased ventilation and the cardiovascular stressing (perhaps baroreceptor sensing of blood pressure stability) and metabolic alterations within the skeletal muscles are likely all factors of importance for afferent feedback to mediate hyperthermia-Induced Fatigue during submaximal intensity exercise. Taking all the potential factors into account, we propose an integrative model that may help understanding the interplay among factors, but also acknowledging that the influence from a given factor depends on the exercise hyperthermia situation. © 2014 American Physiological Society. Compr Physiol 4:657-689, 2014.
H S Luo - One of the best experts on this subject based on the ideXlab platform.
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Fatigue crack growth for batio3 ferroelectric single crystals under cyclic electric loading
Journal of the American Ceramic Society, 2005Co-Authors: Fang Fang, Weiyou Yang, Fang Zhang, H S LuoAbstract:Electrically Induced Fatigue crack growth is an important degradation mechanism for ferroelectric devices. Reliability concerns for ferroelectric devices place stringent demands for ferroelectric materials. In situ observation of electrically Induced Fatigue crack growth was carried out for ferroelectric single crystals under alternating electric field. Electrically Induced Fatigue crack growth was observed both below and above the coercive field. Crack closure and open behavior were observed together with 90° ferroelectric domain switching during the electric cycling. The crack propagation behavior is a repeated process of continuous but small increments followed by a sudden increase in the crack length. It was suggested that the electric boundary condition along the crack face, from its mouth to its tip, is a variation from the impermeable to the permeable state. The gradual attainment of an impermeable crack tip after an incubation period of field cycling causes the observed jump in crack propagation.