|Só pensando, pode-se aumentar a força muscular, garante fisiologista. A técnica é simples, mas bem vigiada: durante alguns meses, cinco vezes por semana, dez voluntários de 20 a 35 anos reuniram-se com pesquisadores da Cleveland Clinic Foundation,em Ohio (EUA) para pensar (só pensar) que estavam fazendo exercícios físicos com o biceps, o músculo do braço. Foram medidos durante os encontros a atividade cerebral e os impulsos elétricos dos neurônios motores nos músculos do braço, uma forma de se certificar de que eles não seriam involuntariamente enrijecidos. Valia apenas o esforço mental. Como resultado, eles mostraram após algumas semanas um aumento de 13,5% na força muscular. Foi feita a mesma experiência com um grupo-controle, também mantido imóvel mas para o qual não foi pedido que pensasse em esforço físico, e esse grupo não mostrou nenhum tipo de crescimento na força muscular. A experiência foi relatada pelo fisiologista Guang Yue, da Cleveland Clinic, durante uma conferência da Sociedade Americana de Neurociência em San Diego (EUA).
A justificativa para esse poder do pensamento está no funcionamento do sistema nervoso central (incluído o cérebro). Os músculos respondem sempre a impulsos de neurônios motores e a descarga desses neurônios no organismo depende de impulsos elétricos que são enviados pelo cérebro.Em sua página da internet, Yue afirma que a possibilidade de haver um treinamento do sistema neural para fortalecer músculos tem um grande potencial na reabilitação neuromuscular. Essa possibilidade oferece oportunidades para melhorar as funções motoras em pacientes que não podem exercer qualquer tipo de força muscular que implique em contrações constantes. O próximo passo do pesquisador é investigar em experiências semelhantes pacientes com idades entre 65 e 80 anos.
Guang Yue, Ph.D.
Department of Biomedical Engineering (ND20)
Lerner Research Institute
9500 Euclid Avenue
Cleveland, Ohio 44195
Telephone: (216) 445-9336
Fax : (216) 444-9198
Neural Control of Movement
Mechanisms of control of human voluntary movements have been studied extensively in the last several decades. Although a great deal has been revealed regarding control strategies in the peripheral neuromuscular system, little is known concerning (1) how the brain, the headquarters of any neuromuscular operation, controls the desired motor action, and (2) how the central nervous system (CNS), including the brain, adapts to various acute and chronic perturbations, such as fatigue, immobilization, training, aging, or disease. Without a good understanding of these questions, effective treatment of movement-disorder diseases is difficult. Our laboratory focuses on investigating issues related to these questions.
Cortical control of finger movements. How the brain controls our fingers is of tremendous interest of almost everyone. However, data on human brain activation during voluntary finger movements are rare. Regaining extension function of upper extremity, especially finger and wrist joints, in patients with movement disorders, such as stroke, is considerably more difficult than regaining flexion function. The mechanisms underlying this phenomenon are unknown. We are studying whether finger extension and flexion movements are controlled differently by the brain, using functional magnetic resonance imaging (fMRI) and EEG-derived movement-related cortical potential (MRCP). Preliminary data indicated that substantially larger brain volume is needed to control finger extension movement than to control the flexion movement.
Plasticity of neural command for maximal voluntary contraction (MVC). Is the command from the brain to muscle for MVC fixed? If the answer is yes, then muscle strength enhancements can only be achieved by enlarging muscle mass and/or improving muscle coordination; if the answer is no, then muscle strength can be improved by increasing neural command from the brain through training the neuromuscular system or even the neural system alone. This possibility (training neural system to improve muscle strength) has great potential in neuromuscular rehabilitation because it provides opportunities for improving motor function (strength) in patients who cannot perform forceful muscle contraction training. We are training people of different populations to determine if muscle strength can be increased by training the CNS alone (NIH grant NS35130). We use fMRI and electrophysiological methods to quantify neural command.
Brain activation during muscle fatigue. Increased fatigability occurs in every patient with muscle weakness, regardless of whether the weakness is due to a central or peripheral neurological disorder. The underlying mechanisms are not well understood and there is a need to study fatigability systematically in neurology and rehabilitation. The behavior of the peripheral neuromuscular system during muscle fatigue has been studied extensively, but the role of the central nervous system in muscle fatigue is largely unknown. We believe that without a good understanding of mechanisms of fatigue in health, an assessment of mechanisms contributing to increased fatigability in neurological disorders is difficult. We are investigating changes in brain activity during motor performance from non-fatigued to moderately fatigued to severely fatigued conditions in healthy volunteers (NIH grant NS37400). Our future goal is to determine mechanisms underlying increased fatiguability in neurological-disorder patients.
Neural mechanisms underlying motor-function recovery in stroke patients. Motor-function recovery after stroke is a process of re-learning the lost motor skills. Although numerous studies have been performed involving motor performance in stroke patients, little is known about the neural mechanisms that mediate the re-acquisition of motor skills. This project uses fMRI and MRCP techniques to determine brain-function mechanisms underlying motor-function recovery by examining the pattern of brain activation at various stages of the recovery process (NIH grant HD36725). This will help us determine whether a particular stage of recovery is accompanied by a unique pattern of brain activation and the “end point” at which the pattern of brain activation and function recovery do not change despite further rehabilitation. The information is important for designing rehabilitative treatments and for reducing health care costs by stopping unnecessary treatment at the earliest appropriate stage.
Improvement of hand function in older adults. Aging is accompanied by a marked decline in the manipulative capabilities of the hand. Little information is available on interventional strategies, such as hand and finger exercises, that might be used to maintain hand function in older adults. The objective of this project (CCF grant RPC5488) is to determine the effects of training with highly skilled finger movements on the hand function of older adults and to identify the neural mechanisms that mediate the improvement in performance.
Yue GH, Cole KJ: Strength increases from the motor program: Comparison of training with maximal voluntary and imagined muscle contractions. Journal of Neurophysiology, 67: 1114-1123, 1992.
Hardy PA, Yue GH: Measurement of magnetic resonance T2 relaxation time for neuromuscular physiological experiments. Journal of Applied Physiology, 83, 904-911, 1997.
Yue GH, Bilodeau M, Hardy PA, Enoka RM: Task-dependent effects of limb immobilization on the fatigability of the elbow flexor muscles in humans. Experimental Physiology, 82, 567-592, 1997.
Yue GH, Ranganathan VK, Siemionow V, Sahgal V: Older adults exhibit a reduced ability to maximally activate their elbow flexor muscles. Journal of Gerontology: Medical Sciences, 54: M249-M253, 1999.
Yue GH, Liu JZ, Siemionow V, Ranganathan VK, Sahgal V: Brain activation during human finger extension and flexion movements. Brain Research, in press.
Siemionow V, Yue GH, Ranganathan VK, Liu JZ, Sahgal V: Relationship between motor activity-related cortical potential and voluntary muscle activation. Experimental Brain Research, in press.
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