Low-Frequency Rectangular Pulse Is Superior to Middle Frequency Alternating Current Stimulation in Cycling of People With Spinal Cord Injury

Effect of electrical muscle stimulation on the improvement of deltoid muscle atrophy in a rat shoulder immobilization model

Immobilization following trauma or surgery induces skeletal muscle atrophy, and improvement in the muscle atrophy is critical for successful clinical outcomes. The purpose of this study is to evaluate the effect of electrical muscle stimulation (EMS) on muscle atrophy. The study design is a controlled laboratory study. Eighty rats (56 to establish the deltoid muscle atrophy [DMA] model and 24 to evaluate the effect of EMS on the model) were used. DMA was induced by completely immobilizing the right shoulder of each rat by placing sutures between the scapula and humeral shaft, with the left shoulder as a control. After establishing the DMA model, rats were randomly assigned into three groups: low-frequency EMS (L-EMS, 10 Hz frequency), medium-frequency EMS (M-EMS, 50 Hz frequency), and control (eight rats per group). After 3 weeks, the deltoid muscles of each rat were harvested, alterations in gene expression and muscle cell size were evaluated, and immunohistochemical analysis was performed. DMA was most prominent 3 weeks after shoulder immobilization. Murf1 and Atrogin were significantly induced at the initial phase and gradually decreased at approximately 3 weeks; however, MyoD expressed an inverse relationship with Murf1 and Atrogin. IL6 expression was prominent at 1 week. The time point for the EMS effect evaluation was selected at 3 weeks, when the DMA was the most prominent with a change in relevant gene expression. The M-EMS group cell size was significantly larger than that of L-EMS and control group in both the immobilized and intact shoulders (all p < 0.05), without significant differences between the L-EMS and control groups. The M-EMS group showed significantly lower mRNA expressions of Murf1 and Atrogin and higher expressions of MyoD and Col1A1 than that of the control group (all p < 0.05). In immunohistochemical analysis, similar results were observed with lower Atrogin staining and higher MyoD and Col1A1 staining in the M-EMS group. DMA model was established by complete shoulder immobilization, with the most prominent muscle atrophy observed at 3 weeks. M-EMS improved DMA with changes in the expression of relevant genes. M-EMS might be a solution for strengthening atrophied skeletal muscles and facilitating rehabilitation after trauma or surgery.

The role of electrical stimulation for rehabilitation and regeneration after spinal cord injury

Electrical stimulation is used to elicit muscle contraction and can be utilized for neurorehabilitation following spinal cord injury when paired with voluntary motor training. This technology is now an important therapeutic intervention that results in improvement in motor function in patients with spinal cord injuries. The purpose of this review is to summarize the various forms of electrical stimulation technology that exist and their applications. Furthermore, this paper addresses the potential future of the technology.

Comparison of the effects of kilohertz- and low-frequency electric stimulations: A systematic review with meta-analysis

OBJECTIVE

This study aimed to determine whether kilohertz-frequency alternating current (KFAC) is superior to low-frequency pulsed current (PC) in increasing muscle-evoked torque and lessening discomfort.

DATA SOURCES

The electronic databases PubMed, PEDro, CINAHL, and CENTRAL were searched for related articles, published before August 2017. Furthermore, citation search was performed on the original record using Web of Science.

REVIEW METHODS

Randomized controlled trials, quasi-experimental studies, and within-subject repeated studies evaluating and comparing KFAC and PC treatments were included. The pooled standardized mean differences (SMDs) of KFAC and PC treatments, with 95% confidence intervals (CIs), were calculated using the random effects model.

RESULTS

In total, 1148 potentially relevant articles were selected, of which 14 articles with within-subject repeated designs (271 participants, mean age: 26.4 years) met the inclusion criteria. KFAC did not significantly increase muscle-evoked torque, compared to PC (pooled SMD: -0.25; 95% CI: -0.53, 0.06; P = 0.120). KFAC had comparable discomfort compared to that experienced using PC (pooled SMD: -0.06; 95% CI: -0.50, 0.38; P = 0.800). These estimates of the effects had a high risk of bias, as assessed using the Downs and Black scale, and were highly heterogeneous studies.

CONCLUSIONS

This meta-analysis does not establish that KFAC is superior to PC in increasing muscle-evoked torque and lessening discomfort level. However, no strong conclusion could be drawn because of a high risk of bias and a large amount of heterogeneity. High quality studies comparing the efficacy between PC and KFAC treatments with consideration of potential confounders is warranted to facilitate the development of effective treatment.

Effects of Intramuscular Electrical Stimulation Using Inversely Placed Electrodes on Myofascial Pain Syndrome in the Shoulder: A Case Series

Myofascial pain syndrome (MPS) is one of the common musculoskeletal conditions of the shoulder which may develop sensory-motor and autonomic dysfunctions at the various level of the neuromuscular system. The pain and dysfunction caused by MPS were primarily treated with physical therapy and pharmacological agents in order to achieve painfree movements. However, in recent years intramuscular electrical stimulation (IMES) with conventional electrode placement was used by researchers to maximise therapeutic values. But, in this study an inverse electrode placement was used to deliver electrical impulses intramuscularly to achieve neuro-modulation at the various level of the nervous system. Nine patients with MPS were treated with intramuscular electrode stimulation using inversely placed electrodes for a period of three weeks. All nine subjects recovered from their shoulder pain and disability within the few weeks of intervention. So, this inverse electrode placement may be more appropriate for chronic pain management.

The efficacy of neuromuscular electrical stimulation with alternating currents in the kilohertz frequency to stimulate gait rhythm in rats following spinal cord injury

Background

Rehabilitation facilitates the reorganization of residual/regenerated neural pathways and is key in improving motor function following spinal cord injury. Neuromuscular electrical stimulation (NMES) has been reported as being clinically effective. Although it can be used after the acute phase post-injury, the optimal stimulation conditions to improve motor function remain unclear. In this paper, we examined the effectiveness of NMES with alternating currents in the kilohertz (kHz) frequency in gait rhythm stimulation therapy.

Methods

Tests were performed using 20 mature female Fischer rats. Incomplete spinal cord injuries (T9 level) were made with an IH impactor using a force of 150 kdyn, and NMES was administered for 3 days from the 7th day post-injury. The needle electrodes were inserted percutaneously near the motor point of each muscle in conscious rats, and each muscle on the left and right leg was stimulated for 15 min at two frequencies, 75 Hz and 8 kHz, to induce a gait rhythm. Motor function was evaluated using Basso, Beattie, Bresnahan (BBB) scores and three-dimensional (3D) gait analysis. Rats were divided into four groups (5 rats/group), including the NMES treatment 75-Hz group (iSCI-NMES 75 Hz), 8-kHz group (iSCI-NMES 8 kHz), injury control group (iSCI-NT), and normal group (Normal-CT), and were compared.

Results

There was no significant difference in BBB scores among the three groups. In 3D gait analysis, compared with the injury control group, the 8-kHz group showed a significant improvement in synergistic movement of both hindlimbs.

Conclusion

We suggest that kHz stimulation is effective in gait rhythm stimulation using NMES.

Whole body oxygen uptake and evoked knee torque in response to low frequency electrical stimulation of the quadriceps muscles: V•O2 frequency response to NMES

Background

There is emerging evidence that isometric Neuromuscular Electrical Stimulation (NMES) may offer a way to elicit therapeutically significant increases in whole-body oxygen uptake in order to deliver aerobic exercise to patients unable to exercise volitionally, with consequent gains in cardiovascular health. The optimal stimulation frequency to elicit a significant and sustained pulmonary oxygen uptake has not been determined. The aim of this study was to examine the frequency response of the oxygen uptake and evoked torque due to NMES of the quadriceps muscles across a range of low frequencies spanning the twitch to tetanus transition.

Methods

Ten healthy male subjects underwent bilateral NMES of the quadriceps muscles comprising eight 4 minute bouts of intermittent stimulation at selected frequencies in the range 1 to 12 Hz, interspersed with 4 minutes rest periods. Respiratory gases and knee extensor torque were simultaneously monitored throughout. Multiple linear regression was used to fit the resulting data to an energetic model which expressed the energy rate in terms of the pulse frequency, the torque time integral and a factor representing the accumulated force developed per unit time.

Results

Additional oxygen uptake increased over the frequency range to a maximum of 564 (SD 114) ml min^-1 at 12 Hz, and the respiratory exchange ratio was close to unity from 4 to 12 Hz. While the highest induced torque occurred at 12 Hz, the peak of the force development factor occurred at 6 Hz. The regression model accounted for 88% of the variability in the observed energetic response.

Conclusions

Taking into account the requirement to avoid prolonged tetanic contractions and to minimize evoked torque, the results suggest that the ideal frequency for sustainable aerobic exercise is 4 to 5 Hz, which coincided in this study with the frequency above which significant twitch force summation occurred.

Electrical Acupoint Stimulation Changes Body Composition and the Meridian Systems in Postmenopausal Women with Obesity

This study evaluates the effects of electrical stimulation on body composition and the meridian system in postmenopausal women with obesity. Forty-one postmenopausal women were recruited in Taiwan. The body composition was used as a screening test for obesity (percentage of body fat: > 30%, waist circumference: > 80 cm). The experimental group (EG, n = 20) received modulated middle-frequency electrical stimulation treatment for 20 min twice a week for 12 consecutive weeks at the Zusanli (ST36) and Sanyinjiao (SP6) acupoints. The control group (CG, n = 21) did not receive any intervention. The measurements of body composition and the meridian system were recorded for both groups in the pre- and post-study. The results showed that the data of body composition (weight, waist and hip circumference, percentage of body fat, and percentage of lean muscle mass) changed considerably in the EG ( p < 0.05); however, no significant difference was observed in the CG. The left triple burner meridian changed notably in both EG and CG throughout the study ( p < 0.05), however there was no difference between the two groups in the overall mean value, up-down ratio, qi and blood ratio, and yin-yang ratio. Our findings suggest that modulated middle-frequency electrical stimulation could help to improve body composition in postmenopausal women with obesity, potentially providing them with better care and health by integrating Western medicine and traditional Chinese medicine.

Force-pain relationship in functional magnetic and electrical stimulation of subjects with paresis and preserved sensation

OBJECTIVE

Using "painless" magnetic stimulation (FMS) to support the cycling of paretic subjects with preserved sensation is possible and potentially superior to electrical stimulation (FES). We investigated the dependence of the torque and the pain evoked by FMS and FES on stimulation conditions in order to optimize magnetic stimulation.

METHODS

Torque and pain induced by quadriceps stimulation in 13 subjects with paresis and preserved sensation (due to multiple sclerosis) were compared under the conditions: (1) small vs large stimulated surfaces of the thigh, (2) varying contraction velocities of the muscle (isometric vs 15 and 30 rpm isokinetic speed), (3) FMS vs FES modalities, and (4) varying magnetic coil locations.

RESULTS

Torque and pain significantly depended on the amount of surface and location of stimulation during FMS, on the stimulation modality, and on the muscle contraction velocity during FES and FMS. FMS with a saddle-shaped coil produced more torque (p<0.05) than any other stimulation modality, even at 30 rpm velocity.

CONCLUSIONS

To support leg cycling of subjects with preserved sensation, the application of FMS stimulation with a large-surface saddle-shaped coil and the focusing of stimulation on the lateral-frontal surface of the thigh produces greater torque and less pain than FES.

SIGNIFICANCE

Optimized magnetic stimulation is a superior alternative to electrical stimulation in the rehabilitation of subjects with preserved sensation.

A comparison of functional electrical and magnetic stimulation for propelled cycling of paretic patients

OBJECTIVE

To compare isometric torque and cycling power, smoothness and symmetry using repetitive functional magnetic stimulation (FMS) and functional electrical stimulation (FES) in patients with paretic legs with preserved sensibility and in patients without sensibility.

DESIGN

Repeated-measures design.

SETTING

Laboratory setting.

PARTICIPANTS

Eleven subjects with complete spinal cord injury (SCI) and 29 subjects with chronic hemiparesis (16.6+/-5.5mo poststroke) volunteered.

INTERVENTIONS

Using a tricycle testbed, participants were exposed to isometric measurements and ergometric cycling experiments, performed during both 20Hz FMS and FES stimulation. Subjects with hemiparesis and with complete SCI were stimulated at maximally tolerable level and maximal intensity, respectively.

MAIN OUTCOME MEASURES

Maximal isometric pedaling torque and mean ergometric power, smoothness, and symmetry were recorded for voluntary, FES, and FMS conditions.

RESULTS

Two different patterns of the efficacy of FMS were identified. (1) Patients with complete SCI did not benefit (less torque and power was evoked with FMS than with FES, P<.003 and 10(-4) respectively). (2) Patients with hemiplegia and preserved sensibility could improve their torque output (P<.05), smoothness, and symmetry of pedaling (P<.05) with FMS more than with FES.

CONCLUSIONS

FMS is a potential alternative to surface FES of the large thigh musculature in stimulation-supported cycling of patients with partially or completely preserved sensibility.

Functional electrical stimulation assisted cycling of patients with subacute stroke: kinetic and kinematic analysis

BACKGROUND

Cycling is a safe and functionally effective exercise for patients with early post-stroke and poor balance. Such exercise is considered even more effective when functional electrical stimulation is added. Our principal aim was to determine the biomechanically quantifiable parameters of cycling that can be improved in patients with subacute hemiparesis by incorporating functional electrical stimulation. These parameters were defined as objective goals that can be achieved in clinical applications. A secondary aim was to determine whether they could be used to identify subjects who would benefit from such therapy.

METHODS

Using a tricycle testbed, we tested 39 subacute (mean 10.9 weeks post-stroke (SD 5.9)), hemiplegic subjects. During isometric measurements we recorded volitional and electrically evoked crank torques, the latter at maximal tolerable intensity. During ergometric measurements, volitional pedaling was alternated with combined pedaling (volitional supported by stimulation), performed at 30-s intervals. Power, smoothness, and symmetry of cycling were evaluated.

FINDINGS

Twenty-six percent of the subjects significantly improved the smoothness of their cycling with functional electrical stimulation. Only 8% and 10% significantly increased their power and symmetry, respectively. The improvement in smoothness significantly correlated with the capability of the individual to generate electrical torque (Spearman's rank correlation coefficient=0.66 at P=0.001).

INTERPRETATION

The smoothness of cycling was the most sensitive parameter improved by functional electrical stimulation. This improvement depended on the amount of torque evoked, and the torque achieved, in turn, correlated with the tolerated intensity of stimulation.

Changes in spastic muscle tone increase in patients with spinal cord injury using functional electrical stimulation and passive leg movements

Objective: Comparison of cycling interventions to reduce spastic muscle tone increase in patients with spinal cord injury.

Setting: Neuroprosthetic outpatient clinic in a university hospital.

Methods: Five patients with spinal cord injury took part in a crossover study in which the lower limbs (1) were stimulated by functional neuromuscular electrical stimulation (FES) to induce leg cycling movements and (2) were passively moved by an ergometer machine. Patients sat in a comfortable chair fastened to the ergometer while FES was done to induce leg cycling (active session). During the passive leg movement session the ergometer moved their legs for the same period of time at the same velocity and frequency.

Main outcome measures: The change in spastic muscle tone increase before and after each training session was tested with the modified Ashworth Scale and the pendulum test of spasticity (relaxation index and peak velocity).

Results: The averaged data of the relaxation index increased after FES by about 68%. Compared with the slight increase after the passive movement training of 12%, this is statistically significant ( P = 0.01). Peak velocity increased after FES by around 50%, while it was nearly unchanged after the passive intervention (1%); this is also significant ( P = 0.01). This was similar with the peak velocity and the modified Ashworth Scale.

Conclusion: The study presents further interesting aspects of the usefulness of FES in patients with spinal cord injury to reduce spastic muscle tone.