Benjamin Kozlowski1,2, Benjamin Pageaux3,4, Emma F Hubbard1, Benjamin St Peters1, Philip J Millar5, Geoffrey A Power6. 1. Neuromechanical Performance Research Laboratory, Department of Human Health and Nutritional Sciences, College of Biological Sciences, University of Guelph, Guelph, ON, Canada. 2. Temerty Faculty of Medicine, Division of Anatomy, Department of Surgery, University of Toronto, Toronto, ON, Canada. 3. École de Kinésiologie et des Sciences de l'Activité Physique (EKSAP), Faculté de Médecine, Université de Montréal, Montréal, Québec, Canada. 4. Centre de Recherche de l'Institut Universitaire de Gériatrie de Montréal (CRIUGM), Montréal, Québec, Canada. 5. Human Cardiovascular Physiology Laboratory, Department of Human Health and Nutritional Sciences, College of Biological Sciences, University of Guelph, Guelph, ON, Canada. 6. Neuromechanical Performance Research Laboratory, Department of Human Health and Nutritional Sciences, College of Biological Sciences, University of Guelph, Guelph, ON, Canada. gapower@uoguelph.ca.
Abstract
PURPOSE: Following a shortening or lengthening muscle contraction, torque produced in the isometric steady state is lower (residual torque depression; rTD) or higher (residual torque enhancement; rTE), respectively, compared to a purely isometric contraction at the same final muscle length and level of activation. This is referred to as the history dependence of force. When matching a given torque level, there is greater muscle activation (electromyography; EMG) following shortening and less activation following lengthening. Owing to these differences in neuromuscular activation, it is unclear whether perception of effort is altered by the history dependence of force during plantar-flexion. METHODS: Experiment 1 tested whether perception of effort differed between the rTD and rTE state when torque was matched. Experiment 2 tested whether perception of effort differed between the rTD and rTE state when EMG was matched. Finally, experiment 3 tested whether EMG differed between the rTD and rTE state when perception of effort was matched. RESULTS: When torque was matched, both EMG and perception of effort were higher in the rTD compared to rTE state. When EMG was matched, torque was lower in the rTD compared to rTE state while perception of effort did not differ between the two states. When perception of effort was matched, torque was lower in the rTD compared to rTE state and EMG did not differ between the two states. CONCLUSION: The combined results from these experiments indicate that the history dependence of force alters one's perception of effort, dependent on the level of motor command.
PURPOSE: Following a shortening or lengthening muscle contraction, torque produced in the isometric steady state is lower (residual torque depression; rTD) or higher (residual torque enhancement; rTE), respectively, compared to a purely isometric contraction at the same final muscle length and level of activation. This is referred to as the history dependence of force. When matching a given torque level, there is greater muscle activation (electromyography; EMG) following shortening and less activation following lengthening. Owing to these differences in neuromuscular activation, it is unclear whether perception of effort is altered by the history dependence of force during plantar-flexion. METHODS: Experiment 1 tested whether perception of effort differed between the rTD and rTE state when torque was matched. Experiment 2 tested whether perception of effort differed between the rTD and rTE state when EMG was matched. Finally, experiment 3 tested whether EMG differed between the rTD and rTE state when perception of effort was matched. RESULTS: When torque was matched, both EMG and perception of effort were higher in the rTD compared to rTE state. When EMG was matched, torque was lower in the rTD compared to rTE state while perception of effort did not differ between the two states. When perception of effort was matched, torque was lower in the rTD compared to rTE state and EMG did not differ between the two states. CONCLUSION: The combined results from these experiments indicate that the history dependence of force alters one's perception of effort, dependent on the level of motor command.
Authors: K M Gallagher; P J Fadel; M Strømstad; K Ide; S A Smith; R G Querry; P B Raven; N H Secher Journal: J Physiol Date: 2001-06-15 Impact factor: 5.182