Effects of training on contractile properties of paralyzed quadriceps muscle (original) (raw)
Related papers
Spinal cord, 2000
Objectives: To assess if contractile speed and fatigability of paralysed quadriceps muscles in individuals with spinal cord injury (SCI) can be altered by functional electrical stimulation leg cycle ergometry (FES-LCE) training. Settings: The Sint Maartenskliniek rehabilitation centre and the University of Nijmegen, Nijmegen, the Netherlands. Methods: Contractile properties of the quadriceps muscle were studied in seven people with motor-complete SCI who participated in a FES-LCE training program. Subjects trained for 30 min, three times per week for 6 weeks. Contractile speed and fatigue characteristics of electrically stimulated isometric contractions were compared before and after 6 weeks of FES-LCE. Results: Fatigue resistance improved following FES-LCE training as indicated by the higher forces maintained in response to repetitive electrical stimulation. In contrast with an improved fatigue resistance, the maximal rate of force rise was unaected, the speed of relaxation increased and the fusion of a 10 Hz force signal decreased. Furthermore, the force-frequency relationship shifted to the right at low stimulation frequencies, indicated by a decline in the ratio of 1 and 100 Hz force responses as well as the ratio of 10 and 100 Hz force responses. Conclusion: FES-LCE training can change the physiological properties of the quadriceps muscle in people with SCI. Even after a short period of training, the stimulated muscles become more resistant to fatigue. Furthermore, the increased speed of relaxation and associated decreased fusion and altered force-frequency relationship following training may be related to adaptations in the calcium handling processes, which re¯ect an early response of long-term disused muscles. Spinal Cord 38, 214 ± 223
Contractile properties of the quadriceps muscle in individuals with spinal cord injury
Muscle & Nerve, 1999
Selected contractile properties and fatigability of the quadriceps muscle were studied in seven spinal cord-injured (SCI) and 13 ablebodied control (control) individuals. The SCI muscles demonstrated faster rates of contraction and relaxation than did control muscles and extremely large force oscillation amplitudes in the 10-Hz signal (65 ± 22% in SCI versus 23 ± 8% in controls). In addition, force loss and slowing of relaxation following repeated fatiguing contractions were greater in SCI compared with controls. The faster contractile properties and greater fatigability of the SCI muscles are in agreement with a characteristic predominance of fast glycolytic muscle fibers. Unexpectedly, the SCI muscles exhibited a forcefrequency relationship shifted to the left, most likely as the result of relatively large twitch amplitudes. The results indicate that the contractile properties of large human locomotory muscles can be characterized using the approach described and that the transformation to faster properties consequent upon changes in contractile protein expression following SCI can be assessed. These measurements may be useful to optimize stimulation characteristics for functional electrical stimulation and to monitor training effects induced by electrical stimulation during rehabilitation of paralyzed muscles.
Physical therapy, 1990
The purpose of this study was to determine the effects of a reduction in the pulse frequency on the fatigue rate of human quadriceps femoris muscle during intermittent (8-second) contractions. Twelve healthy subjects each participated in two experimental sessions. Thirty cycles (cycle time: 8 seconds "on"/12 seconds "off") were applied during each session. During one session, a frequency of 60 pulses per second (pps) was used for all trains. During the other session, the subjects were stimulated with 60 pps for the first train. The stimulating frequency of each train was then progressively reduced, in 5-pps steps, for contractions 2, 3, 5, 8, 12, and 20. By the fifth contraction, the differences in average force produced by the 60-pps trains and the reduced-frequency trains were significant. The difference between the two conditions increased, with the variable-frequency protocol producing 46% more force than the constant-frequency protocol during the last contra...
Variable-frequency-train stimulation of skeletal muscle after spinal cord injury
Journal of Rehabilitation Research and Development, 2004
Skeletal muscle, after spinal cord injury (SCI), becomes highly susceptible to fatigue. Variable-frequency trains (VFTs) enhance force in fatigued human skeletal muscle of able-bodied (AB) individuals. VFTs do this by taking advantage of the "catch-like" property of skeletal muscle. However, mechanisms responsible for fatigue in AB and SCI subjects may not be the same, and the efficacy of VFT stimulation after SCI is unknown. Accordingly, we tested the hypothesis that VFT stimulation would augment torque-time integral in SCI subjects. The quadriceps femoris muscle was stimulated with constant frequency trains (CFTs) (six 200 s square wave pulses separated by 70 ms) or VFTs (a train identical to the CFT, except that the first two pulses were separated by 5 ms) in SCI and AB subjects. After 180 contractions (50% duty cycle), isometric peak torque decreased 44, 56, and 67 percent, in the AB (n = 10), acute SCI (n = 10), and chronic SCI (n = 12) groups, respectively. In fatigued muscle, VFTs enhanced the torquetime integral by 18 percent in AB subjects and 6 percent in chronic SCI patients, and had no effect in acute SCI patients when compared to the corresponding CFT. The much faster rise times in SCI subjects (~80 ms vs. 120 ms in AB subjects) probably contributed to the inability of VFTs to enhance torque-time integrals in SCI patients. The results suggest that the use of VFT stimulation in patients with SCI may not be as efficacious as it is in AB persons.
Neuromodulation: Technology at the Neural Interface, 2007
To investigate the nature of the force-velocity relationship on muscle forces and power outputs during functional electrical stimulation (FES)-evoked cycling at different pedaling cadences. Materials and Methods. Ten patients with T4-T9 spinal cord injuries (ASIA A) performed FES-evoked cycling at 50 rev/ min using a motorized isokinetic ergometer for 20 min, after which quadriceps crank torque and power were measured at 10, 30, and 50 rev/min. Results. Pedal cadence affected both the shape and the magnitudes of the quadriceps torque and power curves. Significantly greater average torque (T) and peak crank torques (PTi) were elicited at lower pedal cadences (T 10 > T 50 , p < 0.001; PTi 10 > PTi 50 , p = 0.007). Instantaneous peak power (PPi) and average power output (PO) increased significantly with pedal cadence, such that PPi 50 and PPi 30 > PPi 10 (p < 0.001) and PO 50 or PO 30 > PO 10 (p < 0.001). At the higher cadences, peak torque and peak power were developed at significantly later angles (p < 0.001). Conclusions. The force-velocity relationship of muscle has a significant effect upon the muscle forces produced during FES-evoked cycling. However, muscle force rise times and fatigue within FES-evoked contractions, especially at a low cadence, should be considered when making comparisons between different FES-cycling cadences.
European Journal of Applied Physiology and Occupational Physiology, 2000
In this study we examined the in¯uence of complete spinal cord injury (SCI) on the mechanical characteristics of skeletal muscle in vivo within 6 months of the injury. Surface electrical stimulation (ES) was applied to the left m. quadriceps femoris of patients at 6, 11 and 24 weeks after injury. Surface ES was also applied to seven able-bodied controls (AB) at two time points 18 weeks apart. ES consisted of 2 bouts of 20, 1-s isometric contractions with 2 s and 2 min of rest between contractions and bouts, respectively. The time from 20± 80% of peak torque (rise time) and the half relaxation time (1/2 RT) were determined for the ®rst and for the last few contractions. Force loss over repeat contractions was greater in SCI than AB (27% vs 95%; P = 0.0001), and did not change over the 18-week period. Rise time did not change over repeat contractions, was not dierent between groups, and nor did it change over the 18-week period (range: 150±172 ms). 1/2 RT showed several group dierences. Overall, 1/2 RT was longer at the beginning of ES in SCI than AB [mean (SE) 133 (15) ms vs 90 (6) ms, P = 0.037]. Slowing of relaxation time with force loss over repeat contractions was found in SCI at 24 weeks after injury [167 (18) ms, P = 0.016], but not at 6 [128 (14) ms] or 11 [145 (12) ms] weeks after injury. AB, in contrast, showed prolonged relaxation times, with force loss at both time points [115 (10) ms and 113 (11) ms; P = 0.0001]. The results indicate that SCI alters the relaxation but not contractile properties of mixed skeletal muscle within the ®rst 24 weeks of injury. Altered calcium handling and contraction-induced ®ber injury are suggested to explain the slower relaxation time per se, and the prolonged relaxation with force loss observed after SCI.
Variability in fibre properties in paralysed human quadriceps muscles and effects of training
Pflügers Archiv : European journal of physiology, 2003
A spinal cord injury usually leads to an increase in contractile speed and fatigability of the paralysed quadriceps muscles, which is probably due to an increased expression of fast myosin heavy chain (MHC) isoforms and reduced oxidative capacity. Sometimes, however, fatigue resistance is maintained in these muscles and also contractile speed is slower than expected. To obtain a better understanding of the diversity of these quadriceps muscles and to determine the effects of training on characteristics of paralysed muscles, fibre characteristics and whole muscle function were assessed in six subjects with spinal cord lesions before and after a 12-week period of daily low-frequency electrical stimulation. Relatively high levels of MHC type I were found in three subjects and this corresponded with a high degree of fusion in 10-Hz force responses (r=0.88). Fatigability was related to the activity of succinate dehydrogenase (SDH) (r=0.79). Furthermore, some differentiation between fibre types in terms of metabolic properties were present, with type I fibres expressing the highest levels of SDH and lowest levels of a-glycerophosphate dehydrogenase. After training, SDH activity increased by 76€26% but fibre diameter and MHC expression remained unchanged. The results indicate that expression of contractile proteins and metabolic properties seem to underlie the relatively normal functional muscle characteristics observed in some paralysed muscles. Furthermore, training-induced changes in fatigue resistance seem to arise, in part, from an improved oxidative capacity.
Neuroscience, 2010
Fatiguing exercise of the quadriceps femoris muscle degrades postural control in human subjects. The aim of this work was to compare the effects of the fatigue of the quadriceps femoris induced by voluntary muscular contraction (VC), and by electrical stimulation (ES) superimposed onto voluntary muscular contraction (VC؉ES), on postural control and muscle strength. Fourteen healthy young adults participated in the study. Postural control and muscle strength were evaluated using a stable force platform and an isokinetic dynamometer, respectively, before (PRE condition) and after the completion of each fatiguing exercise (immediately: POST condition; after a 5 min recovery time: POST 5 condition). In POST, both postural control and muscle strength were impaired by both fatiguing exercises. However, the impairment was higher for VC than for VC؉ES. In POST 5, for both fatiguing exercises, postural control recovered its initial level while muscle strength did not. These results suggest that superimposing ES onto voluntary muscular contractions (VCs) impaired muscle strength and postural control less than did VCs alone. However the duration of recovery of these two neurophysiological functions did not differ for the two fatiguing exercises. For both exercises, postural control was restored faster than the ability to produce muscular strength.