Electrical Stimulation Superimposed onto Voluntary Muscular Contraction

Effect of experimentally induced muscle pain on neuromuscular control of force production

PURPOSE

Neural and peripheral effects of induced muscle pain on explosive force production were investigated.

METHODS

Nine participants performed two maximal, six explosive, and six electrical stimulations induced (twitches and octets) isometric knee extensions before and after (15 min of rest) receiving an intramuscular injection of hypertonic saline (pain inducer) or isotonic (placebo) infusions in two laboratory visits separated by 7 days.

RESULTS

It was observed a reduction of peak torque production in maximal voluntary contraction in both conditions (9.3 and 3.3% for pain and placebo, respectively) and in the rate of torque development in placebo (7%). There was an increase in the rate of torque development for twitch and octets (10.5 and 15.8%, respectively) in the pain condition and peak torque for twitch (12%) in both conditions (as did the total rate of torque development for octets).

CONCLUSION

Force production decreases and increases during voluntary and involuntary contractions, respectively, suggesting that acute pain impairs force production via central mechanisms.

The effect of electromyography triggered electrical stimulation to abdominal muscles on sitting balance, respiratory functions, and abdominal muscle thickness in complete spinal cord injury: a randomized controlled trial

Complete thoracic spinal cord injury (SCI) results in a loss of innervation to the abdominal muscles, which affects trunk stability and performance of activities of daily living from a sitting position. Respiratory function is also affected, leading to frequent pulmonary complications. Given the importance of trunk stability and respiratory function, we investigated the effects of electromyography triggered electrical stimulation (EMG-ES) applied to the abdominal muscles on sitting balance, respiratory functions and abdominal muscle thickness in individuals with complete thoracic SCI. This randomized controlled study included 34 participants with complete thoracic SCI who were randomly allocated to the experimental group ( n  = 17) and the control group ( n  = 17). During the 4-week intervention period, the experimental group received EMG-ES to their abdominal muscles, while the control group received isometric abdominal exercises three times per week. Both groups continued with their routine rehabilitation program (active or passive range of motion exercises, stretching, and balance coordination exercises). The primary outcome measures were the modified functional reach test (mFRT) and trunk control test (TCT). Secondary outcome measures included a pulmonary function test (PFT) and the bilateral abdominal muscle thicknesses using ultrasonography. At the end of the study, the experimental group showed significantly greater improvements in both primary outcomes. The mean difference in pre-post changes between the groups for the mFRT area was 242.8 cm² [95% confidence interval (CI): 181.3-329.8; effect size 0.92; P  < 0.001] and 5.0 points for TCT (95% CI: 3.9-6.0; effect size 0.98, P  < 0.001). The increase in the abdominal muscle thickness was also significantly greater in the experimental group ( P  < 0.001) without significant differences in the PFT ( P  > 0.05). We conclude that adding EMG-ES of abdominal muscles may further improve sitting balance and abdominal muscle thickness in individuals with complete thoracic SCI.

Effects of 12 weeks of neuromuscular electrical stimulation of the quadriceps muscles on the function and physio-biochemical traits in functionally fit female nursing-home residents aged 75 + years: a pilot study

PURPOSE

Muscular changes induced by neuromuscular electrical stimulation (NMES) are well recognized, but knowledge of how NMES influences the physio-biochemical traits of the oldest old is still limited. This study investigated the effect of NMES applied for 12 weeks to the quadriceps muscles of female nursing-home residents aged 75 + on their functional capability and inflammatory, bone metabolism, and cardiovascular traits.

METHODS

Nineteen women regularly taking part in two body conditioning sessions per week were randomized into an electrical stimulation group (ES; n = 10; 30 min sessions, 3 times per week) or a control group (CON; n = 9). At baseline and study week 12, all women performed the 30 s chair stand test (30sCST), the 6-minute walk test (6MWT), and the instrumented timed up and go test (iTUG). Resting heart rates, blood pressure, and the blood concentrations of inflammatory and bone metabolism markers were also measured twice.

RESULTS

NMES increased the strength of participants' quadriceps muscles and their performance on the 30sCST and 6MWT while lowering resting arterial blood pressure and inflammatory marker levels; osteoclast activity showed a tendency to decrease. Changes in the iTUG results were not observed. A multiple regression analysis found that the results of functional tests in the ES group were best correlated with pulse pressure (the 30sCST and iTUG tests) and diastolic blood pressure (the 6MWT test).

CONCLUSION

Twelve weeks of NMES treatment improved participants' functional capacity and inflammatory, bone metabolism, and cardiovascular traits. The ES group participants' performance on functional tests was best predicted by hemodynamic parameters.

Neuromuscular Electrical Stimulation Does Not Influence Spinal Excitability in Multiple Sclerosis Patients

(1) Background: Neuromuscular electrical stimulation (NMES) has beneficial effects on physical functions in Multiple sclerosis (MS) patients. However, the neurophysiological mechanisms underlying these functional improvements are still unclear. This study aims at comparing acute responses in spinal excitability, as measured by soleus Hoffmann reflex (H-reflex), between MS patients and healthy individuals, under three experimental conditions involving the ankle planta flexor muscles: (1) passive NMES (pNMES); (2) NMES superimposed onto isometric voluntary contraction (NMES+); and (3) isometric voluntary contraction (ISO). (2) Methods: In total, 20 MS patients (MS) and 20 healthy individuals as the control group (CG) took part in a single experimental session. Under each condition, participants performed 15 repetitions of 6 s at 20% of maximal voluntary isometric contraction, with 6 s of recovery between repetitions. Before and after each condition, H-reflex amplitudes were recorded. (3) Results: In MS, H-reflex amplitude did not change under any experimental condition (ISO: p = 0.506; pNMES: p = 0.068; NMES+: p = 0.126). In CG, H-reflex amplitude significantly increased under NMES+ (p = 0.01), decreased under pNMES (p < 0.000) and was unaltered under ISO (p = 0.829). (4) Conclusions: The different H-reflex responses between MS and CG might reflect a reduced ability of MS patients in modulating spinal excitability.

Immediate Effects of Whole-Body versus Local Dynamic Electrostimulation of the Abdominal Muscles in Healthy People Assessed by Ultrasound: A Randomized Controlled Trial

Dynamic electrostimulation consists of the application of local or global electrostimulation together with physical exercise. This study aimed to investigate the immediate effects of a dynamic electrostimulation session on the thickness of the abdominal musculature, inter-rectus distance, heart rate, blood pressure, and body temperature, and to identify possible differences in its form of application. A total of 120 healthy participants were divided into three groups: the whole-body electrostimulation group, the local electrostimulation group, and the control group without electrical stimulation. All groups performed a single session with the same dynamic exercise protocol. Muscle thickness and inter-rectus distance were evaluated ultrasonographically using the Rehabilitative Ultrasound Imaging technique both at rest and in muscle contraction (the active straight leg raise test) to find the post-intervention differences. The results showed significant differences in immediate post-intervention heart rate, with a smaller increase in the local electrostimulation group compared to the control and whole-body electrostimulation groups. No significant differences were identified between the groups after the interventions in the rest of the variables analyzed. Therefore, a local application, with the same effects as a global application on the abdominal musculature, has fewer contraindications, which makes its use more advisable, especially in populations with cardiorespiratory disorders, for which more research is needed.

Effect of Superimposed Russian Current on Quadriceps Strength and Lower-Extremity Endurance in Healthy Males and Females

CONTEXT

More studies are needed to compare the effect of voluntary contraction, electrical stimulation, and electrical stimulation superimposed onto voluntary contraction in improving trained and untrained homolog muscle strength and lower-extremity endurance.

DESIGN

Seventy-six healthy young adults (age = 20.41 [3.07] y, 61 females and 15 males) were included in the study. Subjects were randomly divided into 3 groups as voluntary isometric contraction (IC) group, Russian current (RC) group, and superimposed Russian current (SRC) group.

METHODS

All training regimens were performed under physiotherapist supervision for a total of 18 sessions (3 times per week for 6 wk). In each session, 10 ICs were achieved with voluntary isometric exercise only, RC only, or RC superimposed onto ICs. Main outcome measures were trained and untrained quadriceps strength (maximal voluntary isometric contraction [MVIC]) and lower-extremity endurance (sit-to-stand test).

RESULTS

After 6 weeks of training, all outcome measures improved in all groups (P < .05), except the untrained quadriceps MVIC score of RC group (P = .562). The trained quadriceps MVIC score (P < .001, η2 = .478), untrained quadriceps MVIC score (P = .011, η2 = .115), and sit-to-stand test score (P < .001, η2 = .357) differed significantly among the 3 groups; post hoc analysis revealed that the trained quadriceps MVIC score was higher in SRC and RC groups than in the IC group, untrained quadriceps MVIC score was higher in SRC group than in the RC group, and sit-to-stand test score was higher in SRC group than in the RC group and IC group.

CONCLUSIONS

RC and RC superimposed onto IC are superior to IC in improving quadriceps muscle strength, and RC superimposed onto IC is superior to RC and IC in improving lower-extremity endurance. RC superimposed onto IC and voluntary IC created cross-education effect on untrained quadriceps.

Constant Load Pedaling Exercise Combined with Electrical Muscle Stimulation Leads to an Early Increase in Sweat Lactate Levels

A novel exercise modality combined with electrical muscle stimulation (EMS) has been reported to increase cardiovascular and metabolic responses, such as blood lactate concentration. We aimed to examine the effect of constant load pedaling exercise, combined with EMS, by non-invasively and continuously measuring sweat lactate levels. A total of 22 healthy young men (20.7 ± 0.8 years) performed a constant load pedaling exercise for 20 min at 125% of the pre-measured ventilatory work threshold with (EMS condition) and without (control condition) EMS stimulation. Blood lactate concentration was measured by blood samples obtained from the earlobe every minute. Sweat lactate was monitored in real time using a sensor placed on the forearm. The sweat lactate threshold (sLT) was defined as the point of increase in sweat lactate. sLT occurred significantly earlier in the EMS condition than in the control condition. In the single regression analysis, the difference in sLT between the two conditions, as the independent variable, was a significant predictor of the difference in blood lactate concentrations at the end of the exercise (p < 0.05, r = −0.52). Sweat lactate measurement may be a noninvasive and simple alternative to blood lactate measurement to determine the effectiveness of exercise combined with EMS.

Safety and efficacy of electrical stimulation for lower-extremity muscle weakness in intensive care unit 2019 Novel Coronavirus patients: A phase I double-blinded randomized controlled trial

Background

Intensive care unit (ICU) prolonged immobilization may lead to lower-extremity muscle deconditioning among critically ill patients, particularly more accentuated in those with 2019 Novel Coronavirus (COVID-19) infection. Electrical stimulation (E-Stim) is known to improve musculoskeletal outcomes. This phase I double-blinded randomized controlled trial examined the safety and efficacy of lower-extremity E-Stim to prevent muscle deconditioning.

Methods

Critically ill COVID-19 patients admitted to the ICU were randomly assigned to control (CG) or intervention (IG) groups. Both groups received daily E-Stim (1 h) for up to 14 days on both gastrocnemius muscles (GNMs). The device was functional in the IG and non-functional in the CG. Primary outcomes included ankle strength (Ankle_s) measured by an ankle-dynamometer, and GNM endurance (GNM_e) in response to E-Stim assessed with surface electromyography (sEMG). Outcomes were measured at baseline, 3 and 9 days.

Results

Thirty-two (IG = 16, CG = 16) lower extremities in 16 patients were independently assessed. The mean time between ICU admission and E-Stim therapy delivery was 1.8 ± 1.9 days (p = 0.29). At 3 days, the IG showed an improvement compared to the CG with medium effect sizes for Ankle_s (p = 0.06, Cohen's d = 0.77) and GNM_e (p = 0.06, d = 0.69). At 9 days, the IG GNM_e was significantly higher than the CG (p = 0.04, d = 0.97) with a 6.3% improvement from baseline (p = 0.029). E-Stim did not alter vital signs (i.e., heart/respiratory rate, blood saturation of oxygen), showed no adverse events (i.e., pain, skin damage, discomfort), nor interfere with ICU standard of care procedures (i.e., mechanical ventilation, prone rotation).

Conclusion

This study supports the safety and efficacy of early E-Stim therapy to potentially prevent deterioration of lower-extremity muscle conditions in critically ill COVID-19 patients recently admitted to the ICU. If confirmed in a larger sample, E-Stim may be used as a practical adjunctive therapy.

Clinical trial registration

[https://clinicaltrials.gov/], identifier [NCT04685213].

Neuromuscular Electrical Stimulation Training vs. Conventional Strength Training: A Systematic Review and Meta-Analysis of the Effect on Strength Development

ABSTRACT

Happ, KA, and Behringer, M. Neuromuscular electrical stimulation Training vs. conventional strength training: a systematic review and meta-analysis of the effect on strength development. J Strength Cond Res 36(12): 3527-3540, 2022-A systematic review of the current state of literature and a meta-analysis were conducted to compare the strength development between neuromuscular electrical stimulation (NMES) and conventional strength training when training volume is matched. Searches of PubMed and several other databases were conducted for studies that met the following primary inclusion criteria: randomized studies of >20 days duration with a sample size of >4 subjects in each group ("voluntary contraction" [VC] and "electrically stimulated" [ES]) conducted with percutaneous stimulation only in healthy individuals at equal training volume. Finally, a total of 19 studies were included in the analysis. When comparing strength gains between groups (ES-VC), no favorable effect toward a training method could be observed (0.023 hg [95% CI: -0.198 to 0.246, p = 0.836]). Subgroup analyses were performed based on the application type (NMES evoked and NMES onto voluntary contractions) and stimulation frequency. Both analyses revealed no favorable effect and significant difference of groups (significance level set at 0.05). A meta-regression evaluated the relationship between stimulation frequency and effect size difference. The regression showed a tendency of higher stimulation frequencies being associated with higher study effect size differences (predicted effect size = -0.599 + 0.008 (Hz) ( p = 0.176)). The findings indicate that training with NMES results in virtually identical strength gains compared with conventional strength training when training volume is matched. If training with NMES is preferred, the stimulation frequency type (regular or Burst Mode Alternating Current) can be chosen according to preference without loss of effectiveness.

Superimposing neuromuscular electrical stimulation onto voluntary contractions to improve muscle strength and mass: a systematic review

Training and rehabilitation programs involving neuromuscular electrical stimulation superimposed onto voluntary contractions (NMES+) have gained popularity in the last decades. Yet, there is no clear consensus on the effectiveness of such intervention. The aim of this review was to evaluate the effect of chronic exposure to NMES+ on muscle strength and mass compared to conventional volitional training or passive electrical stimulation alone. Two authors conducted an electronic search to identify randomized controlled trials that investigated the effect of NMES+ training, involved healthy participants or orthopaedic patients, detailed a well-defined NMES training protocol, and provided outcomes related to skeletal-muscle strength and/or mass. The authors extracted data on participants, intervention characteristics, muscle-related outcomes, and assessed the methodological quality of the studies.A total of twenty-four studies were included in the review. The majority of these reported an increase in muscle strength following training with NMES+ compared to an equivalent voluntary training or passive NMES training. The highest improvements were found when NMES was superimposed on sub-maximal exercises involving both concentric and eccentric contractions. Only two studies reported an increase in muscle mass after NMES+ intervention, while no significant improvements were found in two other studies.This review indicated that chronic exposure to NMES+ determines muscle strength improvements greater or equal compared to volitional training alone. However, differences in the methodological characteristics of the stimulation and the type of exercise associated with NMES+, revealed significant discrepancies in the results. A deeper understanding of the neurophysiological adaptations to NMES+ is crucial to fully explain the muscle-related enhancement resulting from such intervention.

Therapeutic Potential of Electromyostimulation (EMS) in Critically Ill Patients—A Systematic Review

Ample evidence exists that intensive care unit (ICU) treatment and invasive ventilation induce a transient or permanent decline in muscle mass and function. The functional deficit is often called ICU-acquired weakness with critical illness polyneuropathy (CIP) and/or myopathy (CIM) being the major underlying causes. Histopathological studies in ICU patients indicate loss of myosin filaments, muscle fiber necrosis, atrophy of both muscle fiber types as well as axonal degeneration. Besides medical prevention of risk factors such as sepsis, hyperglycemia and pneumonia, treatment is limited to early passive and active mobilization and one third of CIP/CIM patients discharged from ICU never regain their pre-hospitalization constitution. Electromyostimulation [EMS, also termed neuromuscular electrical stimulation (NMES)] is known to improve strength and function of healthy and already atrophied muscle, and may increase muscle blood flow and induce angiogenesis as well as beneficial systemic vascular adaptations. This systematic review aimed to investigate evidence from randomized controlled trails (RCTs) on the efficacy of EMS to improve the condition of critically ill patients treated on ICU. A systematic search of the literature was conducted using PubMed (Medline), CENTRAL (including Embase and CINAHL), and Google Scholar. Out of 1,917 identified records, 26 articles (1,312 patients) fulfilled the eligibility criteria of investigating at least one functional measure including muscle function, functional independence, or weaning outcomes using a RCT design in critically ill ICU patients. A qualitative approach was used, and results were structured by 1) stimulated muscles/muscle area (quadriceps muscle only; two to four leg muscle groups; legs and arms; chest and abdomen) and 2) treatment duration (≤10 days, >10 days). Stimulation parameters (impulse frequency, pulse width, intensity, duty cycle) were also collected and the net EMS treatment time was calculated. A high grade of heterogeneity between studies was detected with major cofactors being the analyzed patient group and selected outcome variable. The overall efficacy of EMS was inconclusive and neither treatment duration, stimulation site or net EMS treatment time had clear effects on study outcomes. Based on our findings, we provide practical recommendations and suggestions for future studies investigating the therapeutic efficacy of EMS in critically ill patients.

Systematic Review Registration: [https://www.crd.york.ac.uk/prospero/], identifier [CRD42021262287].

Post-arthrolysis rehabilitation in a patient with wrist stiffness secondary to distal radio-ulnar fracture: A case report

BACKGROUND

Arthrolysis is usually performed when stiffness has a disabling effect on quality of life and in cases where physiotherapy has not been effective. This report describes one patient with a chronic stiff wrist who underwent open arthrolysis. The purpose of this case report is to describe the rehabilitation following arthrolysis, in order to illustrate the effects of intensive physiotherapy for this patient.

CASE DESCRIPTION

A 54-year-old woman with chronic wrist stiffness secondary to a radio-ulnar fracture was described. The patient presented severe pain and unsatisfactory wrist range of motion and muscle strength almost 2 years after the traumatic event.

INTERVENTION

Post-arthrolysis rehabilitation was based on edema control, manual therapy, transcutaneous electrical nerve stimulation (TENS), static splinting and strengthening exercises. In addition, graded motor imagery and proprioceptive rehabilitation were included to address impaired motor control. Outcome measures of passive range of motion (PROM), active range of motion (AROM), grip and pinch strength, numeric rating scale (NRS), disability of the arm, shoulder and hand (DASH) and patient-rated wrist/hand evaluation (PRWHE) were recorded.

CONCLUSIONS

The outcomes of this case report suggest that arthrolysis combined with immediate and intensive physiotherapy were a suitable option for the treatment of post-traumatic wrist stiffness in this patient. The passive motion measured intraoperatively was maintained, while pain, functional active motion and strength were improved allowing for social reintegration.

Brain Plasticity Mechanisms Underlying Motor Control Reorganization: Pilot Longitudinal Study on Post-Stroke Subjects

Functional Electrical Stimulation (FES) has demonstrated to improve walking ability and to induce the carryover effect, long-lasting persisting improvement. Functional magnetic resonance imaging has been used to investigate effective connectivity differences and longitudinal changes in a group of chronic stroke patients that attended a FES-based rehabilitation program for foot-drop correction, distinguishing between carryover effect responders and non-responders, and in comparison with a healthy control group. Bayesian hierarchical procedures were employed, involving nonlinear models at within-subject level-dynamic causal models-and linear models at between-subjects level. Selected regions of interest were primary sensorimotor cortices (M1, S1), supplementary motor area (SMA), and angular gyrus. Our results suggest the following: (i) The ability to correctly plan the movement and integrate proprioception information might be the features to update the motor control loop, towards the carryover effect, as indicated by the reduced sensitivity to proprioception input to S1 of FES non-responders; (ii) FES-related neural plasticity supports the active inference account for motor control, as indicated by the modulation of SMA and M1 connections to S1 area; (iii) SMA has a dual role of higher order motor processing unit responsible for complex movements, and a superintendence role in suppressing standard motor plans as external conditions changes.

The effectiveness of superimposed neuromuscular electrical stimulation combined with strengthening exercises on patellofemoral pain: A randomized controlled pilot trial

BACKGROUND

Patellofemoral pain (PFP) is one of the most common disorders of the knee. Neuromuscular electrical stimulation (NMES) is often assumed by clinicians to be an effective adjunctive therapy to quadriceps strengthening.

OBJECTIVE

The aim of this study was to assess the efficacy of superimposed NMES combined with strengthening exercises to improve the recovery of quadriceps strength and function in patients with PFP.

METHODS

This study was planned as a single blind randomized controlled pilot study. A total of twenty-seven patients diagnosed with PFP were randomly assigned into 2 groups. Patients received superimposed NMES in addition to the standardized program (Group I) or only the standardized program (Group II). The patients in both groups were treated 3 times a week for 6 weeks and followed at 12 weeks. Primary outcome measure was quadriceps isokinetic muscle strength. The changes in dependent variables before treatment, 6th, and 12th weeks were analyzed using a 2 × 3 mixed-model analysis of variance.

RESULTS

There were significant improvements in the within groups statistics of all parameters for both groups (p< 0.05). No differences in quadriceps strength, Kujala and Lysholm scores between groups were found at the different time points [F (2, 21) = 0.86; p= 0.12, F (2, 21) = 0.001; p= 0.97, F (2, 21) = 0.12; p= 0.73, respectively].

CONCLUSIONS

The results indicate that superimposed NMES combined with the standardized rehabilitation program has no clinically significant superiority to standardized rehabilitation program alone.

Effect of Abdominal Electrical Muscle Stimulation Training With and Without Superimposed Voluntary Muscular Contraction on Lumbopelvic Control

CONTEXT

Electrical muscle stimulation (EMS) was designed for artificial muscle activation or superimposed training.

OBJECTIVES

To compare the effects of 8 weeks of superimposed technique (ST; application of electrical stimulation during a voluntary muscle action) and EMS on the cross-sectional area of the rectus abdominis, lateral abdominal wall, and on lumbopelvic control.

SETTING

University research laboratory.

DESIGN

Randomized controlled trial.

PARTICIPANTS

Fifty healthy subjects were recruited and randomly assigned to either the ST or EMS group.

INTERVENTION

The participants engaged with the electrical stimulation techniques (ST or EMS) for 8 weeks.

MAIN OUTCOME MEASURES

In all participants, the cross-sectional area of the rectus abdominis and lateral abdominal wall was measured by magnetic resonance imaging and lumbopelvic control, quantified using the single-leg and double-leg lowering tests.

RESULTS

There were no significant differences in the cross-sectional area of the rectus abdominis (right: P = .70, left: P = .99) or lateral abdominal wall (right: P = .07, left: P = .69) between groups. There was a significant difference between groups in the double-leg lowering test (P = .03), but not in the single-leg lowering test (P = .88). There were significant differences between the preintervention and postintervention in the single-leg (P < .001) and double-leg lowering tests (P < .001).

CONCLUSIONS

ST could improve lumbopelvic control in the context of athletic training and fitness.

A New Approach to Evaluate Neuromuscular Fatigue of Extensor Elbow Muscles

Neuromuscular fatigue evaluation is widely performed on different muscles through the conventional protocol using maximum voluntary contraction (MVC) with electrical stimuli in the analyzed muscle. In an attempt to use this protocol on elbow extensor musculature, previous studies and pilot studies showed co-contraction effects from antagonist musculature during muscular stimulations. The aim of this study was to propose a new neuromuscular fatigue protocol evaluation on elbow extensor musculature. Twenty participants preformed exercises to induce central (CenFat) and peripheral fatigue (PerFat). Neuromuscular fatigue was evaluated on knee extensor muscles by a conventional protocol that provides Twitch Superimposed (TS_K) and Twitch Potentiated (TP_K), central and peripheral parameters respectively. For elbow extensor muscles, the protocol used sustained submaximal contraction at 10, 20, 30, 40, and 50% of MVC. The neuromuscular fatigue in upper limbs was identified by Twitch Potentiated (TP_E) and multiple Twitch Superimposed (TS_E) parameters. Using the relationship between MVC (%) and evoked force, the proposed protocol used several TS_E to provide slope, y-intercept and R ². It is proposed that slope, R ², and y-intercept change may indicate peripheral fatigue and the identified relationship between y-intercept and R ² may indicate central fatigue or both peripheral and central fatigue. The results were compared using the non-parametric analyzes of Friedmann and Wilcoxon and their possible correlations were verified by the Spearmann test (significance level set at p < 0.05). After PerFat a decrease in TP_E (57.1%, p < 0.001) was found but not in any TS_E, indicating only peripheral fatigue in upper limbs. After CenFat a decrease in TP_E (21.4%, p: 0.008) and TP_K (20.9%, p < 0.001) were found but not in TS_K, indicating peripheral fatigue in upper and lower limbs but not central fatigue. A non-significant increase of 15.3% after CenFat and a statistical reduction (80.1%, p: 0.001) after PerFat were found by slope. Despite R ² showing differences after both exercises (p < 0.05), it showed a recovery behavior after CenFat (p: 0.016). Although PerFat provided only peripheral fatigue, CenFat did not provide central fatigue. Considering the procedural limitations of CenFat, parameters resulting from the proposed protocol are sensitive to neuromuscular alteration, however, further studies are required.

The influence of low-intensity resistance training combined with neuromuscular electrical stimulation on autonomic activity in healthy adults: A randomized controlled cross-over trial

Background:

Low-intensity resistance training (RT) combined with neuromuscular electrical stimulation (NMES) is one method of exercise to improve the deterioration of physical function. However, it is unclear whether low-intensity RT combined with NMES (RT + NMES) can be safely implemented.

Objective:

This study aimed to examine the influence of low-intensity RT + NMES on autonomic activity and cardiovascular responses in healthy adults.

Methods:

This study was an open-label, randomized controlled cross-over trial. The exercise intensity of isometric knee extension RT was set to 40% of the maximum voluntary contraction (peak torque). NMES was adjusted to a biphasic asymmetrical waveform with the frequency maintained at 50 Hz and a phase duration of 300 μs. The difference in the change in autonomic activity and cardiovascular responses was compared by assessing heart rate variability, blood pressure, and heart rate during RT and RT+NMES.

Results:

Twenty healthy male college students (mean age 21.0±0.6 years) participated in this study. The ratio of low- and high-frequency components of heart rate variability, systolic blood pressure, and heart rate increased during exercise in the RT and RT+NMES sessions (P<0.05). There were no significant differences in autonomic activity and cardiovascular responses throughout the sessions during RT and RT+NMES.

Conclusion:

In conclusion, our results demonstrated that low-intensity RT+NMES was safe and did not induce excessive autonomic and cardiovascular responses in healthy adults.

Intradialytic neuromuscular electrical stimulation improves functional capacity and muscle strength in people receiving haemodialysis: a systematic review

QUESTIONS

Does neuromuscular electrical stimulation (NMES) applied during haemodialysis sessions improve functional capacity in people with end-stage renal disease? Does NMES used in this way also improve muscle strength, muscle mass/architecture, psychological outcomes, cardiovascular outcomes and biochemical variables? Does it have any adverse effects?

DESIGN

Systematic review of randomised controlled trials with meta-analysis. PubMed, Web of Science, Scopus and SPORTDiscus were searched from inception to 15 October 2019.

PARTICIPANTS

Patients receiving haemodialysis for end-stage renal disease.

INTERVENTION

NMES administered during haemodialysis sessions versus control.

OUTCOMES MEASURES

Functional capacity, muscle strength, muscle mass, psychological outcomes, cardiovascular outcomes, biochemical variables and adverse events.

DATA ANALYSIS

Data were meta-analysed where possible and results were expressed as the pooled mean difference between groups with a 95% confidence interval.

RESULTS

Eight studies (221 patients) were included in the analysis. Overall, the methodological quality of the studies was fair to good. NMES improved functional capacity as assessed by the 6-minute walk distance test (MD 31 m, 95% CI 13 to 49) and peak workload attained in incremental exercise (MD 12.5 W, 95% CI 3.2 to 21.9). NMES increased knee extensor muscle strength (MD 3.5 kg, 95% CI 2.3 to 4.7) and handgrip strength (MD 2.4 kg, 95% CI 0.4 to 4.4). Muscle mass/architecture was not substantially affected. NMES was estimated to be beneficial for several domains of quality of life in several studies, although most of these estimates were imprecise. No benefits were found for cardiovascular outcomes. The available data did not establish any clear effects on cardiovascular outcomes or biochemical variables (dialysis efficiency, urea and creatinine). No major NMES-related adverse events were observed.

CONCLUSIONS

NMES is safe, practical and effective for improving functional capacity and muscle strength in haemodialysis patients. Further research is needed to confirm the clinical relevance of these findings.

REGISTRATION

PROSPERO CRD42018107323.

Seven Weeks of Jump Training with Superimposed Whole-Body Electromyostimulation Does Not Affect the Physiological and Cellular Parameters of Endurance Performance in Amateur Soccer Players

Intramuscular density of monocarboxylate-transporter (MCT) could affect the ability to perform high amounts of fast and explosive actions during a soccer game. MCTs have been proven to be essential for lactate shuttling and pH regulation during exercise and can undergo notable adaptational changes depending on training. The aim of this study was to evaluate the occurrence and direction of potential effects of a 7-weeks training period of jumps with superimposed whole-body electromyostimulation on soccer relevant performance surrogates and MCT density in soccer players. For this purpose, 30 amateur soccer players were randomly assigned to three groups. One group performed dynamic whole-body strength training including 3 x 10 squat jumps with WB-EMS (EG, n = 10) twice a week in addition to their daily soccer training routine. A jump training group (TG, n = 10) performed the same training routine without EMS, whereas a control group (CG, n = 8) merely performed their daily soccer routine. 2 (Time: pre vs. post) x 3 (group: EG, TG, CG) repeated measures analyses of variance (rANOVA) revealed neither a significant time, group nor interaction effect for VO₂peak, Total Time to Exhaustion and La_max as well as MCT-1 density. Due to a lack of task-specificity of the underlying training stimuli, we conclude that seven weeks of WB-EMS superimposed to jump exercise twice a week does not relevantly influence aerobic performance or MCT density.

Neuromuscular Electrical Stimulation: A New Therapeutic Option for Chronic Diseases Based on Contraction-Induced Myokine Secretion

Myokines are peptides known to modulate brain neuroplasticity, adipocyte metabolism, bone mineralization, endothelium repair and cell growth arrest in colon and breast cancer, among other processes. Repeated skeletal muscle contraction induces the production and secretion of myokines, which have a wide range of functions in different tissues and organs. This new role of skeletal muscle as a secretory organ means skeletal muscle contraction could be a key player in the prevention and/or management of chronic disease. However, some individuals are not capable of optimal physical exercise in terms of adequate duration, intensity or muscles involved, and therefore they may be virtually deprived of at least some of the physiological benefits induced by exercise. Neuromuscular electrical stimulation (NMES) is emerging as an effective physical exercise substitute for myokine induction. NMES is safe and efficient and has been shown to improve muscle strength, functional capacity, and quality of life. This alternative exercise modality elicits hypertrophy and neuromuscular adaptations of skeletal muscles. NMES stimulates circulating myokine secretion, promoting a cascade of endocrine, paracrine, and autocrine effects. We review the current evidence supporting NMES as an effective physical exercise substitute for inducing myokine production and its potential applications in health and disease.

Does adding an integrated physical therapy and neuromuscular electrical stimulation therapy to standard rehabilitation improve functional outcome in elderly patients with pneumonia? A randomised controlled trial

OBJECTIVE

To compare the effects of an integrated programme of physical and electrical therapy to standard rehabilitation to improve physical and functional performance in elderly patients with pneumonia.

DESIGN

Randomized clinical trial. The study was registered in the ClinicalTrial.gov website (identifier: NCT02515565).

SETTING

University Hospital.

SUBJECTS

In total, 185 elderly patients with pneumonia were eligible for the study, of which 95 were finally randomized.

INTERVENTIONS

Patients were randomized to a control group which received the standard treatment or to an intervention group which received additionally an integrated programme of physical and electrical therapy.

MAIN MEASURES

Demographic and clinical information was acquired. Pulmonary function, length of hospital stay, handgrip strength, independence levels and comorbidities were assessed as descriptive outcomes. The main outcome measure was functional and physical performance, evaluated with the short physical performance battery. Secondary outcome measures were respiratory symptoms including dyspnoea, fatigue and cough.

RESULTS

Mean age of patients was 74.92 (11.03) years in the intervention group and 72.53 (9.24) years in the control group. Significant between groups differences (P < 0.05) were found in short physical performance battery chair stand test (2.17 (0.97) vs. 0.58 (0.61)) and total score (5.91 (3.61) vs. 4.15 (3.15)). The intervention group showed better performance than the control group in both cases. Fatigue (32.04 (18.58) vs. 46.22 (8.90)) and cough (18.84 (2.47) vs. 17.40 (3.67)) showed higher improvement in the intervention group, and significant differences were observed between the groups.

CONCLUSION

An integrated programme of physical and electrical therapy during hospitalization improves physical and functional performance in patients with pneumonia.

Effects of an Eight-Week Superimposed Submaximal Dynamic Whole-Body Electromyostimulation Training on Strength and Power Parameters of the Leg Muscles: A Randomized Controlled Intervention Study

The purpose of this study was to assess the effects of dynamic superimposed submaximal whole-body electromyostimulation (WB-EMS) training on maximal strength and power parameters of the leg muscles compared with a similar dynamic training without WB-EMS. Eighteen male sport students were randomly assigned either to a WB-EMS intervention (INT; n = 9; age: 28.8 (SD: 3.0) years; body mass: 80.2 (6.6) kg; strength training experience: 4.6 (2.8) years) or a traditional strength training group (CON; n = 9; age: 22.8 (2.5) years; body mass: 77.6 (9.0) kg; strength training experience: 4.5 (2.9) years). Both training intervention programs were performed twice a week over a period of 8 weeks with the only difference that INT performed all dynamic exercises (e.g., split squats, glute-ham raises, jumps, and tappings) with superimposed WB-EMS. WB-EMS intensity was adjusted to 70% of the individual maximal tolerable pain to ensure dynamic movement. Before (PRE), after (POST) and 2 weeks after the intervention (FU), performance indices were assessed by maximal strength (Fmax) and maximal power (Pmax) testing on the leg extension (LE), leg curl (LC), and leg press (LP) machine as primary endpoints. Additionally, vertical and horizontal jumps and 30 m sprint tests were conducted as secondary endpoints at PRE, POST and FU testing. Significant time effects were observed for strength and power parameters on LE and LC (LE Fmax +5.0%; LC Pmax +13.5%). A significant time × group interaction effect was merely observed for Fmax on the LE where follow-up post hoc testing showed significantly higher improvements in the INT group from PRE to POST and PRE to FU (INT: +7.7%, p < 0.01; CON: +2.1%). These findings indicate that the combination of dynamic exercises and superimposed submaximal WB-EMS seems to be effective in order to improve leg strength and power. However, in young healthy adults the effects of superimposed WB-EMS were similar to the effects of dynamic resistance training without EMS, with the only exception of a significantly greater increase in leg extension Fmax in the WB-EMS group.

Physical strategies to prevent disuse-induced functional decline in the elderly

Disuse situations can have serious adverse health consequences in the elderly, including mainly functional impairment with subsequent increase in the risk of falls or morbimortality. The present review provides clinicians and care givers with detailed and practical information on the feasibility and effectiveness of physical strategies that are currently available to prevent or attenuate the functional decline that occurs secondarily to disuse situations in the elderly, notably in the hospital setting. In this context, active approaches such as resistance exercises and maximal voluntary contractions, which can be performed both isometrically and dynamically, are feasible during most immobilization situations including in hospitalized old people and represent powerful tools for the prevention of muscle atrophy. Aerobic exercise should also be prescribed whenever possible to reduce the loss of cardiovascular capacity associated with disuse periods. Other feasible strategies for patients who are unwilling or unable to perform volitional exercise comprise neuromuscular electrical stimulation, vibration, and blood flow restriction. However, they should ideally be applied synchronously with voluntary exercise to obtain synergistic benefits.

Muscle plasticity of aged subjects in response to electrical stimulation training and inversion and/or limitation of the sarcopenic process

This review addresses the possible structural and functional adaptations of the muscle function to neuromuscular electrical stimulation (NMES) training in frail and/or aged (without advanced chronic disease) subjects. Evidence suggests that the sarcopenic process and its structural and functional effects would be limited and/or reversed through NMES training using excito-motor currents (or direct currents). From a structural viewpoint, NMES helps reduce muscle atrophy. From a functional viewpoint, NMES enables the improvement of motor output (i.e., muscle strength), gait, balance and activities of daily living which enhances the quality of life of aged subjects. Muscle plasticity of aged subjects in response to NMES training turns out to be undeniable, although many mechanisms are not yet explained and deserve to be explore further. Mechanistic explanations as well as conceptual models are proposed to explain how muscle plasticity operates in aged subjects through NMES training. NMES could be seen as a clinically applicable training technique, safe and efficient among aged subjects and could be used more often as part of prevention of sarcopenia. Therapists and physical conditioners/trainers could exploit this new knowledge in their professional practice to improve life conditions (including the risk of fall) of frail and/or aged subjects.

Electromyostimulation to fight atrophy and to build muscle: facts and numbers

In recent years, electrical myostimulation (EMS) is becoming more and more popular to increase muscle function and muscle weight. Especially it is applied in healthy individual after injury to rebuild muscle mass and in severely atrophic patients who are not able or willing to perform conventional exercise training programs. Studies in experimental models as well as in human subjects confirmed that EMS can increase muscle mass by around 1% and improve muscle function by around 10-15% after 5-6 weeks of treatment. Despite a severe increase in circulating creatine kinase during the first session, EMS can be regarded as a safe therapeutic intervention. At the molecular level, EMS improves the anabolic/catabolic balance and stimulates the regenerative capacity of satellite cells. EMS intensity should be as high as individually tolerated, and a minimum of three sessions per week [large pulses (between 300-450 μs), high frequency (50-100 Hz in young and around 30 Hz in older individuals)] for at least 5-6 weeks should be performed. EMS improved functional performances more effectively than voluntary training and counteracted fast type muscle fibre atrophy, typically associated with sarcopenia. The effect of superimposing EMS on conventional exercise training to achieve more muscle mass and better function is still discussed controversially. Nevertheless, EMS should not be regarded as a replacement of exercise training per se, since the beneficial effect of exercise training is not just relying on building muscle mass but it also exerts positive effects on endothelial, myocardial, and cognitive function.

Training induced changes in quadriceps activation during maximal eccentric contractions

Despite full voluntary effort, neuromuscular activation of the quadriceps group of muscles appears inhibited during eccentric contractions. A nerve stimulation protocol during dynamic contractions of the quadriceps was developed that employed triplets of supramaximal pulses to assess suppressed eccentric activation. Subsequently the effects of a short training intervention, performed on a dynamometer, on eccentric strength output and neural inhibition were examined. Torque-angular velocity (T-ω) and experimental voluntary neural drive-angular velocity (%VA-ω; %VA, obtained via the interpolated twitch technique) datasets, were obtained from pre- and post-training testing sessions. Non-linear regression fits of a seven parameter torque function and of a 3rd degree polynomial were performed on the pre- and post-training T-ω and %VA-ω datasets respectively. T-test showed a significant (p < 0.05) increase in the overall torque output post-training for the group, with three out of the six subjects demonstrating a significant (p < 0.05) increase in the torque output across the range of angular velocities as shown by the extra-sum-of-squares F-test. A significant increase (p < 0.05) in the %VA post-training was also observed as well as a reduction in the plateauing of the torque output during fast eccentric contractions.

Neuromuscular Fatigue After Repeated Jumping With Concomitant Electrical Stimulation

PURPOSE

To evaluate the etiology and extent of neuromuscular fatigue induced by 50 squat jumps performed with and without neuromuscular electrical stimulation (NMES) of the knee extensors.

METHODS

Nine healthy, recreationally active men (24 ± 2 y) took part in 2 experiments. These consisted of 50 squat jumps performed with stimulation (NMES) or without (CON). Maximal voluntary contraction (MVC) force, maximal voluntary activation level (VAL), and forces evoked by single and double (10 and 100 Hz) stimulations were recorded before and after the 50 jumps. NMES was delivered at the maximal tolerated intensity.

RESULTS

Despite average jump height being ∼16% lower in the NMES than in the CON session, a reduction over time in jump height was only found in the NMES condition (-6%). After the 50 jumps, MVC force was reduced to a greater extent in NMES than in CON (-25% ± 11% vs -11% ± 12%). Similarly, forces evoked by single stimulations, as well as by 10-Hz and 100-Hz paired stimulations, were reduced to a greater extent in NMES (-33% ± 12%, -42% ± 15%, and -25% ± 13%) than in CON (-21% ± 6%, -30% ± 9%, and -14% ± 11%). VAL was not significantly altered by either condition.

CONCLUSION

Performing repeated squat jumps with concomitant NMES induced a greater fatigue than squat jumps performed alone and might potentially represent a stronger training stimulus.

Chronic effects of superimposed electromyostimulation during cycling on aerobic and anaerobic capacity

PURPOSE

To examine if chronic endurance training by means of simultaneously applied, superimposed electromyostimulation (EMS) can be used to improve performance and physiological core parameters compared to the traditional cycling.

METHODS

Twenty-one male subjects (VO_2peak 55.2 ± 5.1 ml min^- 1 kg^- 1) were assigned to either a cycling (C) or cycling with superimposed EMS (C + E) group. Before and after the 4-week training period, including 14 sessions of moderate cycling [60 min at 60% peak power output (PPO)], participants performed a 20-min time-trial, a step test to exhaustion, a 30-s isokinetic sprint test, and maximum force- and power-tests. Markers of muscle damage and metabolic condition were assessed during the training period.

RESULTS

Step test results revealed increases in PPO, VO_2peak, lactate threshold 1, and the anaerobic threshold for both groups (p < 0.05). Mean power output (MPO) obtained from time-trial was improved in C and C + E (p < 0.05). Isokinetic sprint test revealed increased PPO in both groups, whereas MPO was only changed in C (p < 0.05). Strength parameters were unaffected. Although metabolic stimuli and markers of muscle damage were higher in C + E compared to C, improvements of endurance performance and capacity were not significantly different between C and C + E.

CONCLUSIONS

Despite a higher metabolic, respiratory, and muscular demand, chronic additional superimposed EMS during cycling does not result in superior improvements in endurance and strength performance compared to the traditional cycling.

Effect of Superimposed Electromyostimulation on Back Extensor Strengthening: A Pilot Study

Park, JH, Seo, KS, and Lee, S-U. Effect of superimposed electromyostimulation on back extensor strengthening: a pilot study. J Strength Cond Res 30(9): 2470-2475, 2016-Electromyostimulation (EMS) superimposed on voluntary contraction (VC) can increase muscle strength. However, no study has examined the effect of superimposing EMS on back extensor strengthening. The purpose of this study was to determine the effect of superimposed EMS on back extensor strengthening in healthy adults. Twenty healthy men, 20-29 years of age, without low-back pain were recruited. In the EMS group, electrodes were attached to bilateral L2 and L4 paraspinal muscles. Stimulation intensity was set for maximally tolerable intensity. With VC, EMS was superimposed for 10 seconds followed by a 20-second rest period. The same protocol was used in the sham stimulation (SS) group, except that the stimulation intensity was set at the lowest intensity (5 mA). All subjects performed back extension exercise using a Swiss ball, with 10 repetitions per set, 2 sets each day, 5 times a week for 2 weeks. The primary outcome measure was the change in isokinetic strength of the back extensor using an isokinetic dynamometer. Additionally, endurance was measured using the Sorensen test. After 2 weeks of back extension exercise, the peak torque and endurance increased significantly in both groups (p ≤ 0.05). Effect size between the EMS group and the SS group was medium in strength and endurance. However, there was no statistically significant difference between 2 groups. In conclusion, 2 weeks of back extensor strengthening exercise was effective for strength and endurance. Superimposing EMS on back extensor strengthening exercise could provide an additional effect on increasing strength.

Effects of combined application of progressive resistance training and Russian electrical stimulation on quadriceps femoris muscle strength in elderly women with knee osteoarthritis

[Purpose] The aim of this study was to investigate the effects of combined application of progressive resistance training and Russian electrical stimulation on quadriceps femoris muscle strength in elderly women with osteoarthritis of the knee. [Subjects] Thirty women over 65 years of age diagnosed with knee osteoarthritis participated in the present study. The subjects were randomly assigned to a control group (n=10), a progressive resistance training group (n=10), or a Russian electrical stimulation group (n=10). [Methods] Each group was treated 3 times weekly for 8 weeks, and each session lasted 45 minutes. Muscle strength was assessed by measuring the peak torque of the quadriceps femoris muscle. Outcome measurements were performed at baseline and at the fourth and eighth weeks of the treatment period. [Results] All groups showed significant intragroup differences in the quadriceps femoris muscle peak torque after the treatment intervention. There were significant intergroup differences between the Russian electrical stimulation group and the other groups. [Conclusion] The results of this study suggest that combined application of progressive resistance training and Russian electrical stimulation can be effective in strengthening the quadriceps femoris muscle in elderly women with knee osteoarthritis.

Modelling suppressed muscle activation by means of an exponential sigmoid function: validation and bounds

The aim of this study was to establish how well a three-parameter sigmoid exponential function, DIFACT, follows experimentally obtained voluntary neural activation-angular velocity profiles and how robust it is to perturbed levels of maximal activation. Six male volunteers (age 26.3±2.73 years) were tested before and after an 8-session, 3-week training protocol. Torque-angular velocity (T-ω) and experimental voluntary neural drive-angular velocity (%VA-ω) datasets, obtained via the interpolated twitch technique, were determined from pre- and post-training testing sessions. Non-linear regression fits of the product of DIFACT and a Hill type tetanic torque function and of the DIFACT function only were performed on the pre- and post-training T-ω and %VA-ω datasets for three different values of the DIFACT upper bound, αmax, 100%, 95% & 90%. The determination coefficients, R(2), and the RMS of the fits were compared using a two way mixed ANOVA and results showed that there was no significant difference (p<0.05) due to changing αmax values indicating the DIFACT remains robust to changes in maximal activation. Mean R(2) values of 0.95 and 0.96 for pre- and post-training sessions show that the maximal voluntary torque function successfully reproduces the T-ω raw dataset.

Pelvic-floor muscle rehabilitation in erectile dysfunction and premature ejaculation

BACKGROUND

In men, involuntary or voluntary ischiocavernosus muscle contractions after erection lead to intracavernous blood pressures far higher than the systolic pressure, which builds and maintains penile rigidity. Thus, erectile dysfunction may be partly due to ischiocavernosus muscle atrophy and may be treated by rehabilitation interventions.

OBJECTIVE

The purpose of this study was to determine whether pelvic-floor muscle strengthening interventions could be associated with increases in intracavernous pressure that would increase penile rigidity.

DESIGN

An observational study was conducted.

METHODS

One hundred twenty-two men with isolated erectile dysfunction and 108 men with isolated premature ejaculation participated (no neuromuscular diseases or previous perineal rehabilitation). Thirty-minute sessions of voluntary contractions coupled with electrical stimulation were designed to increase ischiocavernosus muscle strength (monitored through intracavernous pressure increase). A linear mixed-effects model per group analyzed separately, then jointly, the maximum change in pressure (ΔP) and the maximum baseline (ie, respectively, the average contraction-generated difference in intracavernous pressure and the intracavernous pressure plateau at full erection, both measured during the highest moving average of the best 2 minutes of each session).

RESULTS

Over 20 sessions, the maximum ΔP increased in erectile dysfunction as well as in premature ejaculation (87% and 88%, respectively, in men with positive trends). The maximum baseline also increased (99% and 72%, respectively, in men with positive trends). The joint modeling indicated that the mean expected progressions of the intracavernous pressure after 5 sessions in erectile dysfunction and premature ejaculation were 62.85 and 64.15 cm H2O, respectively.

LIMITATIONS

Indirect measurements were obtained of intracavernous pressure and ischiocavernosus muscle force.

CONCLUSIONS

Pelvic-floor muscle rehabilitation was found to be beneficial in erectile dysfunction. However, its effects on symptoms of premature ejaculation, despite intracavernous pressure gains, were much more difficult to assess. The definitive proof of its benefits requires rather difficult-to-design clinical trials.

Pilot randomized trial of progressive resistance exercise augmented by neuromuscular electrical stimulation for people with multiple sclerosis who use walking aids

OBJECTIVE

To investigate the feasibility and preliminary outcomes of a home progressive resistance training (PRT) program augmented by neuromuscular electrical stimulation (NMES).

DESIGN

Randomized controlled pilot trial.

SETTING

Participant homes.

PARTICIPANTS

People with multiple sclerosis (MS) (N=37) who use a walking aid.

INTERVENTIONS

A 12-week home PRT program or the same program augmented by NMES.

MAIN OUTCOME MEASURES

Strength using hand-held dynamometry; repeated sit to stand test; Berg Balance Scale; timed Up & Go test; 12-Item Multiple Sclerosis Walking Scale; Multiple Sclerosis Impact Scale-29, version 2; and Modified Fatigue Impact Scale (MFIS). The NMES group also completed a device usability questionnaire.

RESULTS

Only change in MFIS score was significantly greater in the NMES group than the PRT group (P=.012). The NMES group improved significantly in quadriceps endurance (median of change, 8.5; P=.043), balance (median of change, 3.5; P=.001), physical impact of MS (median of change, -8.3; P=.001), and impact of fatigue (median of change, -17; P=.001). Participants rated the device as highly usable.

CONCLUSIONS

This pilot study suggests that a home PRT program with NMES is feasible, and the neuromuscular electrical stimulation device is usable by this population. Only reduction in impact of fatigue was greater in the NMES than the PRT group.

Protection against muscle damage induced by electrical stimulation: efficiency of a preconditioning programme

PURPOSE

The aim of this study was to explore the efficiency of a preconditioning programme composed of neuromuscular electrical stimulation (NMES) in the protection against muscle damage induced by a subsequent bout of NMES.

METHODS

Sixteen male volunteers were split up into a control group (CG; n = 8) and a preconditioned group (PCG; n = 8). Both groups attended two NMES bouts (test 1 and test 2) spaced 5 weeks apart. Each one consisted in 100 quadriceps contractions and 100 hamstrings contractions. PCG attended five additional progressive NMES sessions between test 1 and test 2. The outcome measures were the changes in muscle soreness [0-10 pain score on visual analogue pain scale (VAS)], muscle flexibility and serum creatine kinase (CK) activity; they were assessed before (pre-T1) and after (post-T1) test 1 and before (pre-T2) and after (post-T2) test 2.

RESULTS

Damage markers increased similarly in both groups after test 1 (at post-T1, VAS scores = 4·18 ± 2 and 4·43 ± 1·56 cm in CG and PCG, respectively; CK activity = 2307 ± 3774 and 1671 ± 1790 IU l(-1) in CG and PCG, respectively). Compared with test 1, these damage markers were reduced after test 2 in CG (at post-T2, VAS score = 2·68 ± 1·27 cm and CK activity = 218 ± 72 IU l(-1) ). Muscle soreness was further reduced after test 2 in PCG (VAS score = 0·37 ± 0·74 cm).

CONCLUSIONS

A protective effect against muscle damage can be obtained after only one NMES bout, and an additional protective effect can be induced by a preconditioning programme.

Time to task failure influences the postural alteration more than the extent of muscles fatigued

The aim of this study was to compare the effects of unilateral and bilateral muscle fatigue on monopedal postural control. Nineteen subjects completed bilateral fatiguing contractions and unilateral fatiguing contractions of the quadriceps femoris until the torque output for both exercises dropped below 30% of the measured peak torque (the time to task failure was measured) for three consecutive contractions (independently measured for each leg). Postural control was evaluated by using a force platform which recorded center of foot pressure (COP) and was measured before and after the completion of both fatiguing tasks. Spatio-temporal COP parameters were used to evaluate postural control. The unilateral contractions affected monopedal postural control more than the bilateral fatiguing contractions (p<0.05). Moreover, the time to task failure was significantly longer for the unilateral contractions than for the bilateral contractions (p<0.05). The greater alteration of postural control for the unilateral fatiguing contractions compared to the bilateral fatiguing contractions could be related to a longer time to task failure which could provoke greater disturbances of the postural system in terms of sensory input and motor output.

Intra- and interday reliability of voluntary and electrically stimulated isometric contractions of the quadriceps femoris

The reliability of voluntary and electrically stimulated isometric contractions of m. quadriceps femoris of male participants (n=10; age 30±8years; height 1.79±0.05m; body mass 79.4±8.3kg) was investigated using ratio limits of agreement (LoA) on a time scale common to examine recovery from muscle damaging exercise. No systematic changes in reliability occurred over time (baseline versus 2, 24, 48, and 72h). Maximal voluntary contraction (MVC) and interpolated twitch technique (ITT) showed no mean bias (P>0.05) with 95% LoA of ±12.7 and ±5.4, respectively. Resting twitch and potentiated doublet peak force showed no mean bias (P>0.05). However, 95% LoA were smaller for the doublet (±13.9) than the twitch (±32.0). Twitch and doublet rates showed similar trends. Ratio of low (20Hz) to high (50Hz) frequency forces showed no mean bias (P>0.05) and 95% LoA of (±9.2). However, there was significant mean bias (P<0.05) and wider 95% LoA for peak force, contraction and relaxation parameters of the low and high frequency forces. In conclusion, MVC, ITT, potentiated doublet and the ratio of low to high frequency forces are recommended to most reliably examine functional muscle recovery between 2 and 72h after damaging exercise.

Effects of unilateral knee extensor muscle fatigue induced by stimulated and voluntary contractions on postural control during bipedal stance

OBJECTIVE

This study aim was to compare the effects of unilateral knee extensor fatigue induced by electrically stimulated (ES) and voluntary (VOL) contractions on postural control during bipedal stance.

METHODS

Seventeen healthy active males (21.5±2 years) completed these two fatiguing exercises of the quadriceps femoris muscle. Both exercises were of equal duration (130 repetitions of 5 seconds, each separated by a rest period of 2 seconds) and intensity (20% isometric maximal voluntary contraction [MVC]). Both MVC and postural control were recorded using an ergometer and a force platform that registered the centre of foot pressure (COP). We analyzed the spatiotemporal COP parameters (in eyes closed condition) and the spectral power density given by the wavelet transform. Recordings were performed before (PRE condition) and after the completion of each fatiguing task (immediately: POST condition; and after a 5-minute recovery: POST 5 condition).

RESULTS

In the POST and POST 5 conditions, the ES exercise affected MVC more than the VOL exercise but the bipedal postural control was similarly deteriorated for both exercises.

CONCLUSIONS

The disturbance of the bipedal postural control after unilateral knee muscle fatigue is not only related to a reduction in muscle strength but also (especially) to an impairment of the effectiveness of sensory inputs. Unilateral knee muscle fatigue induced by ES similarly degrades the bipedal postural control as that induced by VOL, and the duration of the recovery of postural control did not differ between both fatiguing exercises.

Neuromuscular electrical stimulation as a possible means to prevent muscle tissue wasting in artificially ventilated and sedated patients in the intensive care unit: A pilot study

OBJECTIVE

The aim of this study was to explore if electrical stimulation could prevent muscle atrophy.

MATERIAL AND METHODS

Patients were hospitalized for postoperative coronary artery bypass graftin, chronic obstructive pulmonary disease, ventilatory failure, or acute cerebro-vascular accident, and were divided into an intervention group or a control group. The intervention group underwent daily 30 minute training with an intermittent neuromuscular electrical stimulation applied to the right quadriceps muscle. Heart rate, respiration rate, systolic and diastolic blood pressure, and oxygen saturation were monitored before, during, and after electrical stimulation. Circumference of both thighs was measured.

RESULTS

The intervention resulted in a significant reduction of muscle atrophy in the stimulated as compared with the non-stimulated limb (p < 0.05), without making any impact on cardiovascular, respiratory and, hemodynamic characteristics.

CONCLUSIONS

Muscle atrophy is prevented by intermittent neuromuscular electrical stimulation while this intervention showed no obvious impact on the cardio-respiratory conditions of the patients.

Stimulated contractions delay and prolong central fatigue compared with voluntary contractions in men

Voluntary and stimulated contractions are commonly used in sports training and rehabilitation, and it is well known that both these kinds of contractions generate central fatigue. However, to date, there is a lack of research on the comparison of the mechanisms by which these 2 exercises induce central disturbances. Central fatigue can be characterized by central activation failure during maximal voluntary contraction (MVC). Superimposition of an electrical stimulation onto MVC has been used to detect central activation failure. Completeness of activation has been quantified by the central activation ratio (CAR) = MVC/(MVC + stimulated force). The aim was not only to evaluate the CAR immediately after fatiguing voluntary (VOL) and stimulated (STIM) contractions but also to compare recovery duration over different time periods (prefatigue: PRE condition; immediate postfatigue: POST condition; after a 5-minute recovery: POST 5 condition; after a 30-minute recovery: POST 30 condition) (n = 18). Results showed that in the POST condition, the CAR is more affected for the VOL contractions than for the STIM contractions (p < 0.001). The CAR was affected for the STIM contractions only in the POST 5 condition (p < 0.05). In the POST 30 condition, the CAR was incomplete for the STIM contractions, whereas it was complete for the VOL contractions (p < 0.01). In conclusion, the VOL contractions alter the CAR more than the STIM contractions immediately after their completion. However, the effects of the STIM contractions on the CAR are delayed and prolonged.