The Experts below are selected from a list of 327 Experts worldwide ranked by ideXlab platform
Richard R. Neptune - One of the best experts on this subject based on the ideXlab platform.
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The influence of wheelchair propulsion hand pattern on upper extremity Muscle power and Stress
Journal of Biomechanics, 2016Co-Authors: Jonathan S. Slowik, Philip S. Requejo, Sara J. Mulroy, Richard R. NeptuneAbstract:Abstract The hand pattern (i.e., full-cycle hand path) used during manual wheelchair propulsion is frequently classified as one of four distinct hand pattern types: arc, single loop, double loop or semicircular. Current clinical guidelines recommend the use of the semicircular pattern, which is based on advantageous levels of broad biomechanical metrics implicitly related to the demand placed on the upper extremity (e.g., lower cadence). However, an understanding of the influence of hand pattern on specific measures of upper extremity Muscle demand (e.g., Muscle power and Stress) is needed to help make such recommendations, but these quantities are difficult and impractical to measure experimentally. The purpose of this study was to use musculoskeletal modeling and forward dynamics simulations to investigate the influence of the hand pattern used on specific measures of upper extremity Muscle demand. The simulation results suggest that the double loop and semicircular patterns produce the most favorable levels of overall Muscle Stress and total Muscle power. The double loop pattern had the lowest full-cycle and recovery-phase upper extremity demand but required high levels of Muscle power during the relatively short contact phase. The semicircular pattern had the second-lowest full-cycle levels of overall Muscle Stress and total Muscle power, and demand was more evenly distributed between the contact and recovery phases. These results suggest that in order to decrease upper extremity demand, manual wheelchair users should consider using either the double loop or semicircular pattern when propelling their wheelchairs at a self-selected speed on level ground.
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A theoretical analysis of the influence of wheelchair seat position on upper extremity demand
Clinical Biomechanics, 2013Co-Authors: Jonathan S. Slowik, Richard R. NeptuneAbstract:article i nfo Background: The high physical demands placed on the upper extremity during manual wheelchair propulsion can lead to pain and overuse injuries that further reduce user independence and quality of life. Seat position is an adjustable parameter that can influence the mechanical loads placed on the upper extremity. The pur- pose of this study was to use a musculoskeletal model and forward dynamics simulations of wheelchair propulsion to identify the optimal seat position that minimizes various measures of upper extremity demand including Muscle Stress, co-contraction and metabolic cost. Methods: Forward dynamics simulations of wheelchair propulsion were generated across a range of feasible seat positions by minimizing the change in handrim forces and Muscle-produced joint moments. Resulting Muscle Stress, co-contraction and metabolic cost were examined to determine the optimal seat position that minimized these values. Findings: MuscleStressandmetaboliccostwerenearminimalvaluesatsuperior/inferiorpositionscorresponding to top-dead-center elbow angles between 110 and 120° while at an anterior/posterior position with a hub- shoulder angle between −10 and −2.5°. This coincided with a reduction in the level of Muscle co-contraction, primarily at the glenohumeral joint.
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The influence of altering push force effectiveness on upper extremity demand during wheelchair propulsion
Journal of Biomechanics, 2010Co-Authors: Jeffery W. Rankin, Andrew M. Kwarciak, W. Mark Richter, Richard R. NeptuneAbstract:Manual wheelchair propulsion has been linked to a high incidence of overuse injury and pain in the upper extremity, which may be caused by the high load requirements and low mechanical efficiency of the task. Previous studies have suggested that poor mechanical efficiency may be due to a low effective handrim force (i.e. applied force that is not directed tangential to the handrim). As a result, studies attempting to reduce upper extremity demand have used various measures of force effectiveness (e.g., fraction effective force, FEF) as a guide for modifying propulsion technique, developing rehabilitation programs and configuring wheelchairs. However, the relationship between FEF and upper extremity demand is not well understood. The purpose of this study was to use forward dynamics simulations of wheelchair propulsion to determine the influence of FEF on upper extremity demand by quantifying individual Muscle Stress, work and handrim force contributions at different values of FEF. Simulations maximizing and minimizing FEF resulted in higher average Muscle Stresses (23% and 112%) and total Muscle work (28% and 71%) compared to a nominal FEF simulation. The maximal FEF simulation also shifted Muscle use from Muscles crossing the elbow to those at the shoulder (e.g., rotator cuff Muscles), placing greater demand on shoulder Muscles during propulsion. The optimal FEF value appears to represent a balance between increasing push force effectiveness to increase mechanical efficiency and minimize upper extremity demand. Thus, care should be taken in using force effectiveness as a metric to reduce upper extremity demand.
M L Hull - One of the best experts on this subject based on the ideXlab platform.
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Can the efficacy of electrically stimulated pedaling using a commercially available ergometer BE improved by minimizing the Muscle Stress–time integral?
Muscle & Nerve, 2012Co-Authors: Nils A. Hakansson, M L HullAbstract:INTRODUCTION: The cardiorespiratory and muscular strength benefits of functional electrical stimulation (FES) pedaling for spinal cord injury (SCI) subjects are limited because the endurance of electrically stimulated Muscle is low. METHODS: We tested new electrical stimulation timing patterns (Stim3, designed using a forward dynamic simulation to minimize the Muscle Stress-time integral) to determine whether SCI subjects could increase work and metabolic responses when pedaling a commercial FES ergometer. Work, rate of oxygen uptake (VO(2)), and blood lactate data were taken from 11 subjects (injury level T4-T12) on repeated trials. RESULTS: Subjects performed 11% more work pedaling with Stim3 than with existing stimulation patterns (StimErg) (P = 0.043). Average (VO(2)) and blood lactate concentrations were not significantly different between Stim3 (442 ml/min, 5.9 mmol/L) and StimErg (417 ml/min, 5.9 mmol/L). CONCLUSION: The increased mechanical work performed with Stim3 supports the use of patterns that minimize the Muscle Stress-time integral to prolong FES pedaling.
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Muscle Stimulation Waveform Timing Patterns for Upper and Lower Leg Muscle Groups to Increase Muscular Endurance in Functional Electrical Stimulation Pedaling Using a Forward Dynamic Model
IEEE Transactions on Biomedical Engineering, 2009Co-Authors: Nils A. Hakansson*, M L HullAbstract:Functional electrical stimulation (FES) of pedaling provides a means by which individuals with spinal cord injury can obtain cardiorespiratory exercise. However, the early onset of Muscle fatigue is a limiting factor in the cardiorespiratory exercise obtained while pedaling an FES ergometer. One objective of this study was to determine Muscle excitation timing patterns to increase Muscle endurance in FES pedaling for three upper leg Muscle groups and to compare these timing patterns to those used in a commercially available FES ergometer. The second objective was to determine excitation timing patterns for a lower leg Muscle group in conjunction with the three upper leg Muscle groups. The final objective was to determine the mechanical energy contributions of each of the Muscle groups to drive the crank. To fulfill these objectives, we developed a forward dynamic simulation of FES pedaling to determine electrical stimulation on and off times that minimize the Muscle Stress-time integral of the stimulated Muscles. The computed electrical stimulation on and off times differed from those utilized by a commercially available FES ergometer and resulted in 17% and 11% decrease in the Muscle Stress-time integral for the three upper leg Muscle groups and four upper and lower leg Muscle groups, respectively. Also, the duration of Muscle activation by the hamstrings increased by 5% over a crank cycle for the computed stimulation on and off times, and the mechanical energy generated by the hamstrings increased by 20%. The lower leg Muscle group did not generate sufficient mechanical energy to reduce the energy contributions of the upper leg Muscle groups. The computed stimulation on and off times could prolong FES pedaling, and thereby provide improved cardiorespiratory and Muscle training outcomes for individuals with spinal cord injury. Including the lower leg Muscle group in FES pedaling could increase cardiorespiratory demand while not affecting the endurance of the Muscles involved in the pedaling task.
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Prediction of pedal forces in bicycling using optimization methods.
Journal of Biomechanics, 2004Co-Authors: Rob Redfield, M L HullAbstract:Abstract The bicycle-rider system is modeled as a planar five-bar linkage with pedal forces and pedal dynamics as input. The pedal force profile input is varied, maintaining constant average bicycle power, in order to obtain the optimal pedal force profile that minimizes two cost functions. One cost function is based on joint moments and the other is based on Muscle Stresses. Predicted (optimal) pedal profiles as well as joint moment time histories are compared to representative real data to examine cost function appropriateness. Both cost functions offer reasonable predictions of pedal forces. The Muscle Stress cost function, however, better predicts joint moments. Predicted Muscle activity also correlates well with myolectric data. The factors that lead to effective (i.e. low cost) pedalling are examined. Pedalling effectiveness is found to be a complex function of pedal force vector orientation and Muscle mechanics.
Jonathan S. Slowik - One of the best experts on this subject based on the ideXlab platform.
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The influence of wheelchair propulsion hand pattern on upper extremity Muscle power and Stress
Journal of Biomechanics, 2016Co-Authors: Jonathan S. Slowik, Philip S. Requejo, Sara J. Mulroy, Richard R. NeptuneAbstract:Abstract The hand pattern (i.e., full-cycle hand path) used during manual wheelchair propulsion is frequently classified as one of four distinct hand pattern types: arc, single loop, double loop or semicircular. Current clinical guidelines recommend the use of the semicircular pattern, which is based on advantageous levels of broad biomechanical metrics implicitly related to the demand placed on the upper extremity (e.g., lower cadence). However, an understanding of the influence of hand pattern on specific measures of upper extremity Muscle demand (e.g., Muscle power and Stress) is needed to help make such recommendations, but these quantities are difficult and impractical to measure experimentally. The purpose of this study was to use musculoskeletal modeling and forward dynamics simulations to investigate the influence of the hand pattern used on specific measures of upper extremity Muscle demand. The simulation results suggest that the double loop and semicircular patterns produce the most favorable levels of overall Muscle Stress and total Muscle power. The double loop pattern had the lowest full-cycle and recovery-phase upper extremity demand but required high levels of Muscle power during the relatively short contact phase. The semicircular pattern had the second-lowest full-cycle levels of overall Muscle Stress and total Muscle power, and demand was more evenly distributed between the contact and recovery phases. These results suggest that in order to decrease upper extremity demand, manual wheelchair users should consider using either the double loop or semicircular pattern when propelling their wheelchairs at a self-selected speed on level ground.
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A theoretical analysis of the influence of wheelchair seat position on upper extremity demand
Clinical Biomechanics, 2013Co-Authors: Jonathan S. Slowik, Richard R. NeptuneAbstract:article i nfo Background: The high physical demands placed on the upper extremity during manual wheelchair propulsion can lead to pain and overuse injuries that further reduce user independence and quality of life. Seat position is an adjustable parameter that can influence the mechanical loads placed on the upper extremity. The pur- pose of this study was to use a musculoskeletal model and forward dynamics simulations of wheelchair propulsion to identify the optimal seat position that minimizes various measures of upper extremity demand including Muscle Stress, co-contraction and metabolic cost. Methods: Forward dynamics simulations of wheelchair propulsion were generated across a range of feasible seat positions by minimizing the change in handrim forces and Muscle-produced joint moments. Resulting Muscle Stress, co-contraction and metabolic cost were examined to determine the optimal seat position that minimized these values. Findings: MuscleStressandmetaboliccostwerenearminimalvaluesatsuperior/inferiorpositionscorresponding to top-dead-center elbow angles between 110 and 120° while at an anterior/posterior position with a hub- shoulder angle between −10 and −2.5°. This coincided with a reduction in the level of Muscle co-contraction, primarily at the glenohumeral joint.
Thomas S Buchanan - One of the best experts on this subject based on the ideXlab platform.
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evidence that maximum Muscle Stress is not a constant differences in specific tension in elbow flexors and extensors
Medical Engineering & Physics, 1995Co-Authors: Thomas S BuchananAbstract:Abstract The specific tension of Muscle (or maximum Muscle Stress) is the maximum force developed per unit cross-sectional area and is a frequently used parameter by investigators estimating Muscle force. Generally, it is assumed to be a constant value for all Muscles and, when multiplied by a Muscle's cross-sectional area, is used to provide a measure of a Muscle's maximum force production. In this study, the specific tension for elbow flexors and for extensors were compared to evaluate the validity of this assumption. Maximum Muscle Stress was determined using maximum joint moments measured as a function of joint angle and using anatomical parameters reported in the literature. It was observed that the specific tension for elbow flexors was considerably larger than for extensors when measured a variety of ways. The exact reasons for the differences are unknown, but variations in specific tension of individual fibers may play a role. It was concluded that the use of a constant value for specific tension in Muscle models is questionable in studies that demand accurate results.
Kenneth P Dial - One of the best experts on this subject based on the ideXlab platform.
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Scaling of mechanical power output during burst escape flight in the Corvidae.
The Journal of experimental biology, 2011Co-Authors: Brandon E Jackson, Kenneth P DialAbstract:Avian locomotor burst performance (e.g. acceleration, maneuverability) decreases with increasing body size and has significant implications for the survivorship, ecology and evolution of birds. However, the underlying mechanism of this scaling relationship has been elusive. The most cited mechanistic hypothesis posits that wingbeat frequency alone limits maximal muscular mass-specific power output. Because wingbeat frequency decreases with body size, it may explain the often-observed negative scaling of flight performance. To test this hypothesis we recorded in vivo muscular mechanical power from work-loop mechanics using surgically implanted sonomicrometry (measuring Muscle length change) and strain gauges (measuring Muscle force) in four species of Corvidae performing burst take-off and vertical escape flight. The scale relationships derived for the four species suggest that maximum Muscle-mass-specific power scales slightly negatively with pectoralis Muscle mass (M(-0.18)(m), 95% CI: -0.42 to 0.05), but less than the scaling of wingbeat frequency (M(-0.29)(m), 95% CI: -0.37 to -0.23). Mean Muscle Stress was independent of Muscle mass (M(-0.02)(m), 95% CI: -0.20 to 0.19), but total Muscle strain (percent length change) scaled positively (M(0.12)(m), 95% CI: 0.05 to 0.18), which is consistent with previous results from ground birds (Order Galliformes). These empirical results lend minimal support to the power-limiting hypothesis, but also suggest that Muscle function changes with size to partially compensate for detrimental effects of size on power output, even within closely related species. Nevertheless, additional data for other taxa are needed to substantiate these scaling patterns.
