Electrical Stimulation Frequency and Skeletal Muscle Characteristics: Effects on Force and Fatigue

Gastrocnemius electrical stimulation increases ankle dorsiflexion strength in patients with post-acute sequelae of SARS-COV-2 (PASC): a double-blind randomized controlled trial

Post-Acute sequelae of SARS-CoV-2 (PASC) is a multisystem disorder causing persistent musculoskeletal deconditioning and reduced lower extremity strength. Electrical stimulation (E-Stim) to the gastrocnemius muscle can enhance strength outcomes by increasing the frequency of muscle fiber activation. We investigated its effect on individuals with PASC. Participants were randomized into intervention (IG) or control (CG) groups. The IG self-administered daily one-hour E-Stim to both their gastrocnemius muscles using a functional device over 4-week, while the CG used a sham device. Primary outcomes were ankle dorsiflexion strength assessed via dynamometry during maximum voluntary contractions, and gastrocnemius voluntary activation (GVA) via surface electromyography. The secondary outcome assessed activities of daily living (ADL), instrumental ADL, and mobility queries. Percentage improvement was calculated. Eighteen patients were analyzed (IG = 10; CG = 8). After 4 week, the IG showed a significantly higher improvement in ankle dorsiflexion strength (222.64%) compared to the CG (51.27%, p = 0.002). Additionally, the IG's ankle dorsiflexion strength improvement significantly correlated with GVA improvement (rho = 0.782) at 4 week. The secondary outcomes did not reveal significant changes in neither group. Self-administered gastrocnemius E-Stim improves ankle dorsiflexion strength in individuals with PASC. However, larger sample sizes and longer interventions are needed to validate these findings.

Biomimetic Peripheral Nerve Stimulation Promotes the Rat Hindlimb Motion Modulation in Stepping: An Experimental Analysis

Peripheral nerve stimulation is an effective neuromodulation method in patients with lower extremity movement disorders caused by stroke, spinal cord injury, or other diseases. However, most current studies on rehabilitation using sciatic nerve stimulation focus solely on ankle motor regulation through stimulation of common peroneal and tibial nerves. Using the electrical nerve stimulation method, we here achieved muscle control via different sciatic nerve branches to facilitate the regulation of lower limb movements during stepping and standing. A map of relationships between muscles and nerve segments was established to artificially activate specific nerve fibers with the biomimetic stimulation waveform. Then, characteristic curves depicting the relationship between neural electrical stimulation intensity and joint control were established. Finally, by testing the selected stimulation parameters in anesthetized rats, we confirmed that single-cathode extraneural electrical stimulation could activate combined movements to promote lower limb movements. Thus, this method is effective and reliable for use in treatment for improving and rehabilitating lower limb motor dysfunction.

Analysis of electrical stimulation and voluntary muscle contraction on skeletal muscle oxygen uptake and mitochondrial recovery using near-infrared spectroscopy

PURPOSE

This investigation was to compare differences in skeletal muscle oxygen consumption ([Formula: see text]) and mitochondrial recovery between voluntary (VOL) and electrically stimulated (ES) plantarflexion contractions.

METHODS

Twelve men and women (26 ± 4.0 years; 171.8 ± 5.1 cm; 74.0 ± 13.7 kg) were seated in a chair with their right knee fully extended and right foot secured to a force transducer. ES electrodes and a near-infrared spectroscopy device were placed on the gastrocnemius. Participants performed ES plantarflexion contractions across a range of stimulation intensities at frequencies of 1 and 2 Hz and similar VOL contractions. Cuff occlusion occurred immediately following each series of contractions to measure [Formula: see text]. A standardized mitochondrial function assessment protocol was also performed to calculate K-constants between work-matched ES and VOL contractions.

RESULTS

For mitochondrial assessments, there were no significant differences between ES and VOL rate constants (2.03 ± 0.98 vs. 1.25 ± 1.35 min-1, p = 0.266). ES resulted in a significantly greater workrate-[Formula: see text] slope at 1 Hz (0.007 ± 0.007 vs. 0.001 ± 0.002% [Formula: see text]/s/N, p = 0.014) and 2 Hz (0.010 ± 0.010 vs. 0.001 ± 0.001% [Formula: see text]/s/N, p = 0.012), as well as a significantly greater workrate-[Formula: see text] Y-intercept at 2 Hz (1.603 ± 1.513 vs. 0.556 ± 0.564% [Formula: see text]/s, p = 0.035) but not 1 Hz (0.579 ± 0.448 vs. 0.442 ± 0.357% mV̇O2/s, p = 0.535) when compared to VOL.

CONCLUSION

ES results in a significantly greater [Formula: see text] at similar work rates compared to VOL, however, the mitochondrial recovery rate constants were similar. The greater mVO2 with ES may partially contribute to the increased rate of fatigue during ES exercise in individuals with muscle paralysis.

Effect of Athletic Training on Fatigue During Neuromuscular Electrical Stimulation

The purpose of this study was to explore the effect an individual's exercise training type will have on muscle fatigability during repetitive contractions induced by Neuromuscular Electrical Stimulation (NMES). Thirty-four subjects comprising of competitive athletes and controls were recruited into three cohorts: Endurance (runners/cyclists) n = 13; nine male, four female; 27 ± 8 years old, Explosive (Lifters/Sprinters) n = 11; nine male, two female; 30 ± 7 years old, and controls n = 10, six male, four female, 26 ± 4 years old. Subjects were placed in a custom-made leg extension rig, and received NMES against a fixed resistance (NMES-FR), to the Vastus Medialis muscle resulting in isometric leg extensions, at a duty cycle of 1 s on/3 s rest, for 20 min. The force of the isometric contractions was recorded using a Hogan MicroFet2 dynamometer, and three separate fatigue metrics were calculated to compare the different cohorts, sports within each cohort, and gender within each cohort. For every fatigue metric, the endurance group fatigued significantly less than both the explosive and control cohorts, with no difference observed between the explosive and the controls. Within each cohort, no significant difference was observed in any fatigue metric between sport or gender, but these comparisons lacked power. The results show that only high capacity endurance activity will have any effect on reducing one's fatigability during repetitive NMES. The implications of this conclusion can aid in the development of NMES regimens for use in healthy populations, such as athletic training or astronaut musculoskeletal countermeasures, as well as clinical applications when fatigue is to be minimized.

Output of Electronic Muscle Stimulators: Physical Therapy and Police Models Compared

INTRODUCTION

Both physical therapists and police officers use electrical muscle stimulation. The typical physical therapist unit is attached with adhesive patches while the police models use needle-based electrodes to penetrate clothing. There have been very few papers describing the outputs of these physical therapy EMS (electrical muscle stimulator) units.

METHODS

We purchased 6 TENS/EMS units at retail and tested them with loads of 500 Ω, 2 kΩ, and 10 kΩ.

RESULTS

For the typical impedance of 500 Ω, the EMS units delivered the most current followed by the electrical weapons; TENS units delivered the least current. At higher im-pedances (> 2 kΩ) the electrical weapons delivered more current than the EMS units, which is explained by the higher voltage-compliance of their circuits. Some multi channel EMS units deliver more calculated muscle stimula tion than the multi-channel weapons.

CONCLUSION

Present therapeutic electrical muscle stimula-tors can deliver more current than present law-enforcement muscle stimulators.

Assessment of muscle activity using electrical stimulation and mechanomyography: a systematic review

This research has proved that mechanomyographic (MMG) signals can be used for evaluating muscle performance. Stimulation of the lost physiological functions of a muscle using an electrical signal has been determined crucial in clinical and experimental settings in which voluntary contraction fails in stimulating specific muscles. Previous studies have already indicated that characterizing contractile properties of muscles using MMG through neuromuscular electrical stimulation (NMES) showed excellent reliability. Thus, this review highlights the use of MMG signals on evaluating skeletal muscles under electrical stimulation. In total, 336 original articles were identified from the Scopus and SpringerLink electronic databases using search keywords for studies published between 2000 and 2020, and their eligibility for inclusion in this review has been screened using various inclusion criteria. After screening, 62 studies remained for analysis, with two additional articles from the bibliography, were categorized into the following: (1) fatigue, (2) torque, (3) force, (4) stiffness, (5) electrode development, (6) reliability of MMG and NMES approaches, and (7) validation of these techniques in clinical monitoring. This review has found that MMG through NMES provides feature factors for muscle activity assessment, highlighting standardized electromyostimulation and MMG parameters from different experimental protocols. Despite the evidence of mathematical computations in quantifying MMG along with NMES, the requirement of the processing speed, and fluctuation of MMG signals influence the technique to be prone to errors. Interestingly, although this review does not focus on machine learning, there are only few studies that have adopted it as an alternative to statistical analysis in the assessment of muscle fatigue, torque, and force. The results confirm the need for further investigation on the use of sophisticated computations of features of MMG signals from electrically stimulated muscles in muscle function assessment and assistive technology such as prosthetics control.

Effects of Aerobic and Anaerobic Fatigue Exercises on Postural Control and Recovery Time in Female Soccer Players

Sixteen female soccer players (age = 20.19 ± 1.52 years; body mass = 56.52 ± 4.95 kg; body height = 164.81 ± 4.21 cm) with no history of lower extremity injury participated in the study. The Biodex SD Balance system was used to determine the non-dominant single-leg stability. In anaerobic exercise, each subject performed four maximal cycling efforts against a resistance equivalent to 0.075 kg/body mass for 30 s with three-minute rest intervals. In aerobic exercise, subjects performed the Bruce protocol on a motorized treadmill. After each exercise, subjects subsequently performed a single-leg stability test and then repeated the same test for four times with five-minute passive rest periods. In accordance with the results, it was found that the impairment observed right after the aerobic loading was higher (p < 0.001) compared to the anaerobic one. However, the time-related deterioration in both aerobic and anaerobic loadings was similar. The B-pre value was lower than B_post and B₅ (p < 0.01) and B₁₀ (p < 0.05) in both conditions. Subjects could reach the initial balance level at B₁₅ after aerobic and anaerobic loadings. The lactate level did not reach resting value even after 20 min of both fatigue protocols. Although the fatigue after aerobic and aerobic exercise negatively affects a single-leg dynamic balance level, single leg balance ability returns to the baseline status after 10 min of passive recovery duration.

Interleaved intramuscular stimulation with minimally overlapping electrodes evokes smooth and fatigue resistant forces

OBJECTIVE

It is known that multi-site interleaved stimulation generates less muscle fatigue compared to single-site synchronous stimulation. However, in the limited number of studies in which intramuscular electrodes were used, the fatigue reduction associated with interleaved stimulation could not consistently be achieved. We hypothesize that this could be due to the inability to place the intramuscular electrodes used in interleaved stimulation in locations that minimize overlap amongst the motor units activated by the electrodes. Our objective in the present study was to use independent intramuscular electrodes to compare fatigue induced by interleaved stimulation with that generated by synchronous stimulation at the same initial force and ripple.

APPROACH

In the medial gastrocnemius muscle of an anesthetized rabbit (n = 3), ten intramuscular hook wire electrodes were inserted at different distances from the nerve entry. Overlap was measured using the refractory technique and only three electrodes were found to be highly independent. After ensuring that forces obtained by both stimulation modalities had the same ripple and magnitude, fatigue induced during interleaved stimulation across three independent distal electrodes was compared to that obtained by synchronously delivering pulses to a single proximal electrode.

MAIN RESULTS

Contractions evoked by interleaved stimulation exhibited less fatigue than those evoked by synchronous stimulation. Twitch force recruitment curves collected from each of the ten intramuscular electrodes showed frequent intermediate plateaus and the force value at these plateaus decreased as the distance between the electrode and nerve entry increased.

SIGNIFICANCE

The results indicate that interleaved intramuscular stimulation is preferred over synchronous intramuscular stimulation when fatigue-resistant and smooth forces are desired. In addition, the results suggest that the large muscle compartments innervated by the primary intramuscular nerve branches give rise to progressively smaller independent compartments in subsequent nerve divisions.

Control of Functional Electrical Stimulation Systems Using Simultaneous Pulse Width, Amplitude, and Frequency Modulations

BACKGROUND

One significant challenge of developing a controller for functional electrical stimulation systems is the time-variant nonlinear dynamics of the neuromusculoskeletal system. In the conventional methods, the stimulation intensity is adjusted by a controller; however, the stimulation frequency is always constant. The previous studies have shown that the stimulation frequency is effective in fatigue formation.

OBJECTIVES

A simultaneous modulation of the stimulation intensity and frequency is proposed to improve the joint controllability and muscle endurance. The presented control method determines pulse width (PW), amplitude, and frequency of the electrical stimulation signal, synchronously. Three different modulations are applied for control of the knee joint to show the superiority of the proposed modulation.

METHODS

The stimulation intensity is controlled by the PW and pulse amplitude of the electrical signal using an adaptive fuzzy terminal sliding mode controller and a fuzzy logic controller, respectively. Also, a fuzzy logic controller is applied to adjust the stimulation frequency. The proposed method is utilized to control the knee joint movement using quadriceps femoris muscles for ten paraplegic subjects.

RESULTS

Two different test protocols are defined to evaluate the presented method: A protocol for testing the controllability and another protocol for evaluating the produced muscle endurance. The average value of the root mean square of the tracking error was 6.4° for the proposed method which is 5.1° and 9.6° less than PW modulation and synchronous PW and amplitude modulation, respectively. The average time duration of the knee full extension was 96 sec for the proposed method which is 17 and 26 sec more than PW modulation and synchronous PW and amplitude modulation, respectively.

CONCLUSIONS

The experimental results show that control performance and tracking ability of the joint reference trajectory are improved by using the simultaneous modulation of PW, amplitude, and frequency.

Design and Validation of Multichannel Wireless Wearable SEMG System for Real-Time Training Performance Monitoring

Monitoring of training performance and physical activity has become indispensable these days for athletes. Wireless technologies have started to be widely used in the monitoring of muscle activation, in the sport performance of athletes, and in the examination of training efficiency. The monitorability of performance simultaneously in the process of training is especially a necessity for athletes at the beginner level to carry out healthy training in sports like weightlifting and bodybuilding. For this purpose, a new system consisting of 4 channel wireless wearable SEMG circuit and analysis software has been proposed to detect dynamic muscle contractions and to be used in real-time training performance monitoring and analysis. The analysis software, the Haar wavelet filter with threshold cutting, can provide performance analysis by using the methods of moving RMS and %MVC. The validity of the data obtained from the system was investigated and compared with a biomedical system. In this comparison, 90.95% ± 3.35 for left biceps brachii (BB) and 90.75% ± 3.75 for right BB were obtained. The output of the power and %MVC analysis of the system was tested during the training of the participants at the gym, and the training efficiency was measured as 96.87% ± 2.74.

EJTM3 is also covering Mobility and Medicine at large, an update

Since the first 2018 issue, the European Journal of Translational Myology expanded its authorship and readership from the strict topics of biology, physiology, diagnostic, management and rehabilitation of skeletal muscle to the more clinically relevant fields of human mobility to those of general medicine. This third issue opens with a review on Chronic Fatigue Syndrome, a very complex medical problem, as its other names testify (Myalgic Encephalomyelitis or Systemic Exertion Intolerance Disease). A more typical molecular myology original article follows (Increasing autophagy does not affect neurogenic muscle atrophy), but then several Rapid Reports cover different Medical Specialties fields, related or unrelated to neuromyology, mobility problems and their potential solutions. The Advisors of EJTM invite Authors to submit typescripts, taking into account that the journal is keen to publish high-level papers in the fields of Translational Myology, Mobility and Medicine at large.