R. M. Glaser

Evaluation of the amplitude and frequency components of the surface EMG as an index of muscle fatigue

The frequency components and amplude of the surface electromyogram (EMG) were measured during both 3-s (tensions of 5-100% of the maximum voluntary contraction (MVC)) and fatiguing contractions at 25, 40 and 70% MVC in the handgrip, biceps, adductor pollicis and quadriceps muscles in six male subjects. For the handgrip and biceps muscles, the experiments were repeated at three different muscle lengths: the length at which the muscle was able to exert its maximum isometric strength, and the muscle length above and below that length which corresponded to a length at which the muscle could exert 80% of it maximum. The frequency components of the EMG were the same during brief fatiguing isometric contractions in any of the muscles examined here as long as the muscles contracted near their optimal length. Shortening the muscle length prior to contraction caused an increase in the power in the low frequencies of the EMG power spectra while stretching a muscle had the opposite effect during isometric contraction...

Improving the efficacy of electrical stimulation-induced leg cycle ergometry: an analysis based on a dynamic musculoskeletal model

To improve the design and increase the effectiveness of electrical stimulation-induced leg cycle ergometry, it is necessary to have a better understanding of the factors that influence the force production capabilities of the stimulated muscles, the ability of the muscles to produce the desired movement, and the metabolic demands of the contractions. A dynamic musculoskeletal model capable of simulating a spinal cord injured (SCI) person exercising on a stimulation-powered leg cycle ergometer was developed to explore these issues. This model was used to address the concern whether performance can be improved by changing seat configuration, the loading, or the intermuscle stimulation pattern. Performance was assessed in terms of the probability that a given SCI subject would be able to maintain a steady cadence, the relative strength required by each muscle group to pedal alone, and the estimated rate of metabolic energy utilization associated with steady-state pedaling. The authors considered the sensitivity of the model predictions to intersubject variability. Several strategies are suggested for either minimizing the strength needed to pedal, or maximizing the cardiovascular aerobic exercise. >

Musculoskeletal responses of spinal cord injured individuals to functional neuromuscular stimulation-induced knee extension exercise training.

This study was conducted to evaluate a newly designed functional neuromuscular stimulation (FNS)-induced knee extension (KE) exercise system that incorporates the most desired features of previously described systems by determining the musculoskeletal responses of spinal cord injured (SCI) individuals to training. A specially designed chair and electrical stimulator were fabricated for FNS-induced KE resistance exercise. Surface electrodes were placed over motor points of the quadriceps muscles, and KE was alternated between legs at an average rate of 6 KE/min/leg. KE testing protocols were developed for pre- and post-training evaluations of performance, and 12 SCI subjects exercise-trained up to three times per week for 36 sessions using a progressive resistance load at ankle level. Pre- and post-training evaluation data were statistically compared using a 0.05 level for significance. Quadriceps muscle performance (strength x repetitions) improved for both legs in all subjects as indicated by significant increases in load resistance and repetitions over the 36-session training period (right leg mean = 1156.0 versus 1624.8 kg.reps, left leg mean = 1127.3 versus 1721.1 kg.reps). In addition, knee range of motion significantly increased (right leg mean = 134 versus 146 degrees, left leg mean = 133 versus 144 degrees). Thigh skinfold, thigh girth, body weight and bone density were not significantly changed. The lack of decrease in bone density in some subjects suggests that the training may retard the rate of bone loss which typically occurs with SCI. No injuries or problems were encountered during testing and training.(ABSTRACT TRUNCATED AT 250 WORDS)

Bicycle Ergometer For Paralyzed Muscle

A bicycle ergometer for exercising paralyzed muscle in man is described. This system can be used for isotonic training for both the cardiovascular system and skeletal muscle for individuals who are paralyzed. The device cannot be used on individuals who have lower motor neuron lesions. The device is based upon a standard MonarkTM bicycle ergometer. The ergometer has been modified with sensors for feedback of crank position that an Apple IITM computer then uses to coordinate stimulation of muscles. The muscles used in the study are the iliacus and quadriceps. Exercise training to test the device was conducted on four paraplegic and quadriplegic subjects over a period of 30 days. Exercise was induced three times per week for a period of 15 minutes. Results of these experiments show an increase in endurance and muscle size.

Arm exercise training for wheelchair users.

Although individuals with lower-limb paralysis typically use their arms for wheelchair locomotion and exercise training, several factors including the relatively small muscle mass available, as well as deficient cardiovascular reflex responses and inactivity of the venous muscle pump (resulting in hypokinetic circulation), can cause the early onset of fatigue during arm activity. Thus, cardiopulmonary (aerobic) fitness is difficult to develop and maintain; this situation can often be exacerbated by a sedentary lifestyle. The purpose of this paper is to present research related to exercise capability of wheelchair users, arm exercise modes, physical fitness training programs using arm exercise, and newly developed exercise techniques which incorporate combinations of voluntary arm exercise and functional neuromuscular stimulation-induced exercise of paralyzed leg muscles. It is evident that exercise training programs utilizing appropriate techniques can markedly improve the physical fitness, functional independence, and rehabilitation outcome of wheelchair users.

Physiologic responses of paraplegics and quadriplegics to passive and active leg cycle ergometry.

The purposes of this study were three-fold: (a) to determine acute physiologic responses of spinal cord injured (SCI) subjects to peak levels of leg cycle ergometry utilizing functional neuromuscular stimulation (FNS) of paralyzed leg muscles, (b) to determine the relative contributions of passive and active components of FNS cycling to the peak physiologic responses, and (c) to compare these physiologic responses between persons who have quadriplegia and those who have paraplegia. Thirty SCI subjects (17 quadriplegics and 13 paraplegics) performed a discontinuous graded FNS exercise test from rest to fatigue on an ERGYS 1 ergometer. Steady-state physiologic responses were determined by open-circuit spirometry, impedance cardiography with ECG, and auscultation. In the combined statistics of both groups, it was noted that peak FNS cycling significantly increased (from rest levels) mean oxygen uptake by 255%, arteriovenous O2 difference VO2 and VE, Q and a-vO2 and VCO by 69%, and stroke volume by 45%, while total peripheral vascular resistance decreased by 43%. Mean peak power output for paraplegics (15 W) was significantly higher than for quadriplegics (9 W), eliciting higher peak levels of pulmonary ventilation and sympathetically mediated hemodynamic responses such as cardiac output, heart rate, and systolic and diastolic arterial blood pressure. Passive cycling without FNS produced no statistically significant increases in physiologic responses above the resting level in either group.

Metabolic and hemodynamic responses to concurrent voluntary arm crank and electrical stimulation leg cycle exercise in quadriplegics

This study determined the metabolic and hemodynamic responses in eight spinal cord injured (SCI) quadriplegics (C5-C8/T1) performing subpeak arm crank exercise (ACE) alone, subpeak functional electrical stimulation leg cycle exercise (FES-LCE) alone, and subpeak FES-LCE concurrent with subpeak ACE (hybrid exercise). Subjects completed 10 minutes of each exercise mode during which steady-state oxygen uptake (VO2), pulmonary ventilation (VE), heart rate (HR), cardiac output (CO), stroke volume (SV), mean arterial pressure (MAP), arteriovenous oxygen difference (a-v O2 diff), and total peripheral resistance (TPR) were determined. Although mean VO2 for both ACE alone and FES-LCE alone was matched at 0.66 l/mi, individualized power outputs ranged from 0-30 W (mean = 19.4 +/- 1.3) and 0-12.2 W (mean = 2.3 +/- 0.6), respectively. Hybrid exercise elicited significantly higher VO2 (by 54 percent), VE (by 39-53 percent), HR (by 19-33 percent), and CO (by 33-47 percent), and significantly lower TPR (by 21-34 percent) than ACE or FES-LCE performed alone (P less than or equal to 0.05). Stroke volume was similar between hybrid exercise and FES-LCE alone, and these two exercise modes evoked a significantly higher SV (by 41-56 percent) than during ACE alone. These data clearly demonstrate that hybrid exercise creates a higher aerobic metabolic demand and cardiac-volume load in SCI quadriplegics than either subpeak levels of ACE or FES-LCE performed separately. Therefore, hybrid exercise may provide more advantageous central cardiovascular training effects in quadriplegics than either ACE or FES-LCE alone.

Acute hemodynamic responses of spinal cord injured individuals to functional neuromuscular stimulation-induced knee extension exercise

The purpose of this study was to determine and compare acute hemodynamic responses of spinal cord injured (SCI) quadriplegics (quads), and paraplegics (paras) during a graded-intensity knee extension (KE) exercise test utilizing functional neuromuscular stimulation (FNS) of paralyzed quadriceps muscles. Seven quads and seven paras (N = 14) performed a series of 4-minute stages of bilateral alternating FNS-KE exercise (approximately zero to 70 degree range of motion at the knee and 6 KE/min/leg) at ankle loads of 0, 5, 10, and 15 kg/leg. Physiologic responses were determined with open-circuit spirometry, impedance cardiography, and auscultation. Comparing rest with peak FNS-KE for both groups combined, FNS-KE exercise elicited significant (p less than 0.05) increases in oxygen uptake (130 percent), pulmonary ventilation (120 percent), respiratory exchange ratio (37 percent), arteriovenous oxygen difference (57 percent), cardiac output (32 percent), stroke volume (41 percent), mean arterial pressure (18 percent), and rate-pressure product (23 percent). Heart rate increased significantly by 11 percent from the 5- to the 15-kg/leg stages. Physiologic responses of quads and paras were very similar, except for lower (p less than 0.05) arterial pressures, rate-pressure product, and peripheral vascular resistance in quads. This graded FNS-KE exercise up to the 15-kg/leg load induced relatively small but appropriate increases in aerobic metabolism and cardiopulmonary responses that appear to be safe and easily tolerated by quads and paras. Arterial pressure needs to be monitored carefully in quads to prevent excessive hypertension or hypotension. Although FNS-KE exercise has been shown to elicit peripheral adaptations to improve muscle strength and endurance, it is probably not an effective central cardiovascular training tool for all but the least fit SCI individuals. This information is important for understanding the effects of FNS use during more complex activities such as cycling and ambulation.

Pulmonary function changes in wheelchair athletes subsequent to exercise training

The purpose of this investigation was to determine the pulmonary function and aerobic fitness of wheelchair athletes and assess changes in these values subsequent to an upper-body interval training programme (ITP). Eight male members of the United States national collegiate champion wheelchair basketball team were tested prior to and after an 8 week ITP. Each subject trained (30 min; 3 times per week) on a wheelchair ergometer (WERG) at a power output which would elicit 80% of maximum HR reserve. Before and after training, measurements were obtained at rest, during WERG exercise at 10,20 and 30 W, and during maximal exercise. Static lung volumes and timed forced expiratory volumes measured by spirometry were unchanged by training. Submaximal exercise pulmonary ventilation and oxygen uptake values were similar before and after training, but maximal exercise ventilation (KEmax) increased from 100 to 1311 min−1. In addition, the ratio of KEmax to maximum voluntary ventilation (12s) increased significantly fr...

Energy cost and cardiopulmonary responses for wheelchair locomotion and walking on tile and on carpet.

The purpose of this study was to compare energy cost and cardiopulmonary responses to wheelchair locomotion and walking on tile and on carpet at 3.0 km-h-1. Nine wheelchair-dependent (WD) and ten able-bodied (AB) individuals served as test subjects. WD subjects were tested for wheelchair locomotion on tile and on carpet, and AB subjects were tested for walking over both floor surfaces. Studied variables included gross energy cost (GEC), net locomotive energy cost (NLEC), pulmonary ventilation (VE) and heart rate (HR) during all test conditions. On tile, GEC and NLEC were found to be lower, whereas VE and HR were higher for wheelchair locomotion than for walking. On carpet, wheelchair locomotion elicited higher values for all variables than walking. In going from tile to carpet, significant increases in these variables were found for wheelchair locomotion, whereas walking elicited similar response magnitudes on both floor surfaces. These results suggest that cardiopulmonary stresses for wheelchair locomotion are higher than for walking, and that a carpet can present an obstacle to wheelchair locomotion which may not be recognised by those who walk.