Prevention of muscle disuse atrophy by low-frequency electrical stimulation in rats

An electrical stimulation intervention protocol to prevent disuse atrophy and muscle strength decline: an experimental study in rat

BACKGROUND

Skeletal muscle is negatively impacted by conditions such as spaceflight or prolonged bed rest, resulting in a dramatic decline in muscle mass, maximum contractile force, and muscular endurance. Electrical stimulation (ES) is an essential tool in neurophysiotherapy and an effective means of preventing skeletal muscle atrophy and dysfunction. Historically, ES treatment protocols have used either low or high frequency electrical stimulation (LFES/HFES). However, our study tests the use of a combination of different frequencies in a single electrical stimulation intervention in order to determine a more effective protocol for improving both skeletal muscle strength and endurance.

METHODS

An adult male SD rat model of muscle atrophy was established through 4 weeks of tail suspension (TS). To investigate the effects of different frequency combinations, the experimental animals were treated with low (20 Hz) or high (100 Hz) frequency before TS for 6 weeks, and during TS for 4weeks. The maximum contraction force and fatigue resistance of skeletal muscle were then assessed before the animals were sacrificed. The muscle mass, fiber cross-sectional area (CSA), fiber type and related protein expression were examined and analyzed to gain insights into the mechanisms by which the ES intervention protocol used in this study regulates muscle strength and endurance.

RESULTS

After 4 weeks of unloading, the soleus muscle mass and fiber CSA decreased by 39% and 58% respectively, while the number of glycolytic muscle fibers increased by 21%. The gastrocnemius muscle fibers showed a 51% decrease in CSA, with a 44% decrease in single contractility and a 39% decrease in fatigue resistance. The number of glycolytic muscle fibers in the gastrocnemius also increased by 29%. However, the application of HFES either prior to or during unloading showed an improvement in muscle mass, fiber CSA, and oxidative muscle fibers. In the pre-unloading group, the soleus muscle mass increased by 62%, while the number of oxidative muscle fibers increased by 18%. In the during unloading group, the soleus muscle mass increased by 29% and the number of oxidative muscle fibers increased by 15%. In the gastrocnemius, the pre-unloading group showed a 38% increase in single contractile force and a 19% increase in fatigue resistance, while in the during unloading group, a 21% increase in single contractile force and a 29% increase in fatigue resistance was observed, along with a 37% and 26% increase in the number of oxidative muscle fibers, respectively. The combination of HFES before unloading and LFES during unloading resulted in a significant elevation of the soleus mass by 49% and CSA by 90%, with a 40% increase in the number of oxidative muscle fibers in the gastrocnemius. This combination also resulted in a 66% increase in single contractility and a 38% increase in fatigue resistance.

CONCLUSION

Our results indicated that using HFES before unloading can reduce the harmful effects of muscle unloading on the soleus and gastrocnemius muscles. Furthermore, we found that combining HFES before unloading with LFES during unloading was more effective in preventing muscle atrophy in the soleus and preserving the contractile function of the gastrocnemius muscle.

Low-frequency electrical stimulation alleviates immobilization-evoked disuse muscle atrophy by repressing autophagy in skeletal muscle of rabbits

BACKGROUND

The study aimed to investigate the effect of low-frequency electrical stimulation (LFES) on disuse muscle atrophy and its mechanism in a rabbit model of knee extension contracture.

METHODS

This study involved two experiments. In the time-point experiment, 24 rabbits were randomly divided into 4 groups: Control 1 (Ctrl1 group), immobilization for 2 weeks (I-2 group), immobilization for 4 weeks (I-4 group), and immobilization for 6 weeks (I-6 group). In the intervention experiment, 24 rabbits were randomly divided into 4 groups: Control 2 (Ctrl2 group), electrical stimulation (ESG group), natural recovery (NRG group), and electrical stimulation treatment (ESTG group). All intervention effects were assessed by evaluating the knee joint range of motion (ROM), cross-sectional area (CSA) of the rectus femoris muscle, and expression of autophagy-related proteins.

RESULTS

The time-point experiment showed that immobilization reduced the knee ROM, reduced the rectus femoris muscle CSA, and activated autophagy in skeletal muscle. The levels of five autophagy-related proteins [mammalian target of rapamycin (mTOR), phosphorylated mTOR (p-mTOR), autophagy-related protein 7 (Atg7), p62, and microtubule-associated protein light chain 3B-II (LC3B-II)] were significantly elevated in the skeletal muscle of the I-4 group. The intervention experiment further showed that LFES significantly improved the immobilization-induced reductions in ROM and CSA. Additionally, LFES resulted in a significant decrease in the protein expression of mTOR, p-mTOR, Atg7, p62, and LC3B-II in the rectus femoris muscle.

CONCLUSIONS

LFES alleviates immobilization-evoked disuse muscle atrophy possibly by inhibiting autophagy in the skeletal muscle of rabbits.

Wearable and Implantable Electroceuticals for Therapeutic Electrostimulations

Wearable and implantable electroceuticals (WIEs) for therapeutic electrostimulation (ES) have become indispensable medical devices in modern healthcare. In addition to functionality, device miniaturization, conformability, biocompatibility, and/or biodegradability are the main engineering targets for the development and clinical translation of WIEs. Recent innovations are mainly focused on wearable/implantable power sources, advanced conformable electrodes, and efficient ES on targeted organs and tissues. Herein, nanogenerators as a hotspot wearable/implantable energy-harvesting technique suitable for powering WIEs are reviewed. Then, electrodes for comfortable attachment and efficient delivery of electrical signals to targeted tissue/organ are introduced and compared. A few promising application directions of ES are discussed, including heart stimulation, nerve modulation, skin regeneration, muscle activation, and assistance to other therapeutic modalities.

Transcutaneous carbon dioxide application inhibits muscle atrophy after fracture in rats

BACKGROUND

Muscle atrophy causes difficulty in resuming daily activities after a fracture. Because transcutaneous carbon dioxide (CO₂) application has previously upregulated oxygen pressure in the local tissue, thereby demonstrating its potential in preventing muscle atrophy, here we investigated effects of CO₂ application on muscle atrophy after femoral shaft fracture.

METHODS

Thirty fracture model rats were produced and randomly divided into a no treatment (control group) and treatment (CO₂ group) groups. After treatment, the soleus muscle was dissected at post-fracture days 0, 14, and 21. Evaluations were performed by measuring muscle weight and performing histological examination and gene expression analysis.

RESULTS

Muscle weight was significantly higher in the CO₂ group than in the control group. Histological analysis revealed that the muscle fiber cross-sectional area was reduced in both groups. Nevertheless, the extent of atrophy was lesser in the CO₂ group. Muscle fibers in the control group tended to change into fast muscle fibers. Vascular staining revealed that more capillary vessels surrounded the muscle fibers in the CO₂ group than in the control group. Messenger RNA (mRNA) analysis revealed that the CO₂ group had a significantly enhanced expression of genes that were related to muscle synthesis.

CONCLUSION

Transcutaneous CO₂ application may be a novel therapeutic strategy for preventing skeletal muscle atrophy after fracture.

Ketogenic Diet Potentiates Electrical Stimulation-Induced Peripheral Nerve Regeneration after Sciatic Nerve Crush Injury in Rats

SCOPE

Recent findings indicate that the ketogenic diet (KD) is neuroprotective and electrical stimulation (ES) can improve functional recovery from peripheral nerve injury. However, it is not clear whether KD and ES play a synergistical role in the peripheral nerve recovery following injury.

METHODS AND RESULTS

A KD consisting of a 3:1 ratio of fat to carbohydrate + protein is used and is coupled with ES treatment in a rat model of peripheral nerve crush injury. Neuromuscular recovery is evaluated by electromyography, and axonal regeneration and myelination by histological methods. The effects on insulin-like growth factor 1 (IGF-1) and IGF-1 receptor expression in peripheral nerve tissue, pre- and post-nerve injury, are also investigated. The combination of KD and ES synergistically increases muscle force in biceps femoris and gluteus maximus and prevents development of hypersensitivity in biceps femoris. It promotes peripheral nerve regeneration by increasing total axons, axon density, and axonal diameter, as well as myelin thickness and axon/fiber ratio. These effects are due to modulation of the IGF system as the treatment expression of IGF-1 and IGF-1 receptor in regenerated nerve tissue.

CONCLUSION

The results establish that KD and ES promote peripheral nerve regeneration. Patients recovering from peripheral nerve injury may benefit from this combinational approach.

Investigation of Low-Current Direct Stimulation for Rehabilitation Treatment Related to Muscle Function Loss Using Self-Powered TENG System

Muscle function loss is characterized as abnormal or completely lost muscle capabilities, and it can result from neurological disorders or nerve injuries. The currently available clinical treatment is to electrically stimulate the diseased muscles. Here, a self-powered system of a stacked-layer triboelectric nanogenerator (TENG) and a multiple-channel epimysial electrode to directly stimulate muscles is demonstrated. Then, the two challenges regarding direct TENG muscle stimulation are further investigated. For the first challenge of improving low-current TENG stimulation efficiency, it is found that the optimum stimulation efficiency can be achieved by conducting a systematic mapping with a multiple-channel epimysial electrode. The second challenge is TENG stimulation stability. It is found that the force output generated by TENGs is more stable than using the conventional square wave stimulation and enveloped high frequency stimulation. With modelling and in vivo measurements, it is confirmed that the two factors that account for the stable stimulation using TENGs are the long pulse duration and low current amplitude. The current waveform of TENGs can effectively avoid synchronous motoneuron recruitment at the two stimulation electrodes to reduce force fluctuation. Here, after investigating these two challenges, it is believed that TENG direct muscle stimulation could be used for rehabilitative and therapeutic purpose of muscle function loss treatment.

Self-Powered Direct Muscle Stimulation Using a Triboelectric Nanogenerator (TENG) Integrated with a Flexible Multiple-Channel Intramuscular Electrode

Muscle function loss can result from multiple nervous system diseases including spinal cord injury (SCI), stroke, and multiple sclerosis (MS). Electrical muscle stimulation is clinically employed for rehabilitative and therapeutic purpose and typically requires mA-level stimulation current. Here, we report electrical muscle stimulation, which is directly powered by a stacked-layer triboelectric nanogenerator (TENG) through a flexible multiple-channel intramuscular electrode. This multiple-channel intramuscular electrode allows mapping of motoneurons that is sparsely distributed in the muscle tissue and thus enables high efficiency TENG muscle stimulation, although the short-circuit current of the TENG is only 35 μA. With a stimulation efficiency matrix, we find the electrical muscle stimulation efficiency is affected by two factors, namely, the electrode-motoneuron position, and the stimulation waveform polarity. To test whether it is a universal phenomenon for electrical stimulation, we then further investigate with the conventional square wave current stimulation and confirm that the stimulation efficiency is also affected by these two factors. Thus, we develop a self-powered direct muscle stimulation system with a TENG as power source and waveform generator, and a multiple-channel intramuscular electrode to allow motoneuron mapping for stimulation efficiency optimization. We believe such self-powered system could be potentially used for rehabilitative and therapeutic purpose to treat muscle function loss.

Effect of electrical stimulation on motor nerve regeneration in sciatic nerve ligated-mice

The purpose of this study was to investigate the effect of electrical stimulation on sciatic nerve regeneration and functional recovery of target muscles. Mice were randomly divided into 3 groups: ligated without electrical stimulation, ligated with electrical stimulation and control (non-ligated). The unilateral peripheral mononeuropathy was produced on the right hind limb. Sciatic nerve was then electrically stimulated daily for a period of 2 weeks (duration: 0.2 msec, frequency: 100Hz, amplitude: 15mA). Evoked surface EMG was recorded from biceps femoris (BF) and gluteus maximus (GM) muscles on the 3rd, 7th, 10th and 14th day after sciatic nerve ligation. Muscle force and sensitivity was determined by processing of the recorded EMG signals in time and frequency domains respectively. The results showed electrical stimulation (ES) produced a significant increase in the EMG response of BF, and muscle force significantly increased on the 14th day (p<0.001), however no significant difference was found in GM muscle force between experimental groups. This may be due to possible innervation by inferior gluteal nerve. Frequency analysis of BF signals indicates that hyperalgesia remained after 14 days in both ligated groups. On the 14th day no difference in GM muscle sensitivity was found between groups. In conclusion, the results of this study have shown that the electrical stimulation of sciatic nerve accelerates nerve repair and indirectly improves BF muscle force to a comparable level with control without effect on muscle sensitivity. However, ES had no effect on GM muscle force and sensitivity.

Comparison of morphological changes of muscle fibers in response to dynamic electrical muscle contraction and dynamic hydraulic stimulation in a rat hindlimb disuse model

This study attempted to compare the muscle fiber morphological responses to dynamic electrical muscle stimulation (DEMS) and dynamic hydraulic stimulation (DHS) in rats under hindlimb suspension (HLS). DEMS at 1 Hz, 50 Hz and 100 Hz for 10 min/day, 5 days/week were introduced to the animals' right quadriceps. Static and 2 Hz DHS were introduced to the right tibiae of other animal groups on a "10 min on - 5 min off - 10 min on" loading regime for 5 days/week. In the end of the 4-week experiments, histological changes in the corresponding soleus, gastrocnemius and quadriceps of the stimulated sites were examined. Compared to age-matched, HLS led to muscle atrophy and strongly reduced muscle wet weights and averaged cross-sectional fiber areas. Among the tested DEMS frequencies, the averaged cross-sectional quadriceps fiber area in the 50 Hz group was 29 % larger than the 100 Hz group. In contrast, difference in the muscle fiber response to the static and 2 Hz DHS was not observed in either soleus or gastrocnemius. Muscle fiber morphological responses to the active DEMS was in a load frequency dependent manner under disuse condition. Relatively passive compressions, either via static or 2Hz DHS, were unable to induce any difference in the muscle fiber responses under functional disuse.

Clinical study of botulinum toxin A injection combined with spasmodic muscle therapeutic instrument on lower limb spasticity in patients with stroke

The clinical effect of botulinum toxin A (BTX-A) injection combined with spasmodic muscle therapeutic instrument with simple BTX-A injection was compared. Eighty patients with stroke were randomly divided into the treatment and control groups of 41 and 39 cases, respectively. The two groups of patients were given routine rehabilitation therapy. Ultrasound-guide positioning technology was used; treatment group was administered BTX-A injection combined spasmodic muscle therapeutic instrument while the control group received only BTX-A injection. Muscle tension and motor function were evaluated at 1, 4, 8 and 12 weeks after treatments by rehabilitation physician who was not aware of the grouping of the patients. Muscle tension was significantly reduced after BTX-A injection in the treatment and control groups. Modified Ashworth scale scores of the treatment and control groups 1 and 4 weeks after treatment were significantly lower than those before treatment. Motor function of lower limbs of patients, 1 and 4 weeks after treatment improved significantly. The comparison of step size and walking speed of the groups showed obvious differences with statistical significance (P<0.01). In conclusion, ultrasonic guidance BTX-A injection is easy to operate with good safety. It can effectively improve extensor myospasm of lower limb of patients with rapid onset and the spasm relief can last for three months. Spasmodic muscle therapeutic instrument can improve the spasm condition of lower limb muscle after stroke as well as motor function of lower limbs and activity of daily living, which can make spasmolysis of BTX-A last for a longer period of time.

Muscle and Limb Mechanics

Understanding of the musculoskeletal system has evolved from the collection of individual phenomena in highly selected experimental preparations under highly controlled and often unphysiological conditions. At the systems level, it is now possible to construct complete and reasonably accurate models of the kinetics and energetics of realistic muscles and to combine them to understand the dynamics of complete musculoskeletal systems performing natural behaviors. At the reductionist level, it is possible to relate most of the individual phenomena to the anatomical structures and biochemical processes that account for them. Two large challenges remain. At a systems level, neuroscience must now account for how the nervous system learns to exploit the many complex features that evolution has incorporated into muscle and limb mechanics. At a reductionist level, medicine must now account for the many forms of pathology and disability that arise from the many diseases and injuries to which this highly evolved system is inevitably prone. © 2017 American Physiological Society. Compr Physiol 7:429-462, 2017.

Using the Hephaistos orthotic device to study countermeasure effectiveness of neuromuscular electrical stimulation and dietary lupin protein supplementation, a randomised controlled trial

Purpose

The present study investigated whether neuromuscular electrical stimulation for 20 min twice a day with an electrode placed over the soleus muscle and nutritional supplementation with 19 g of protein rich lupin seeds can reduce the loss in volume and strength of the human calf musculature during long term unloading by wearing an orthotic unloading device.

Methods

Thirteen healthy male subjects (age of 26.4 ± 3.7 years) wore a Hephaistos orthosis one leg for 60 days during all habitual activities. The leg side was randomly chosen for every subject. Six subjects only wore the orthosis as control group, and 7 subjects additionally received the countermeasure consisting of neuromuscular electrical stimulation of the soleus and lateral gastrocnemius muscles and lupin protein supplementation. Twenty-eight days before and on the penultimate day of the intervention cross-sectional images of the calf muscles were taken by magnetic resonance imaging (controls n = 5), and maximum voluntary torque (controls n = 6) of foot plantar flexion was estimated under isometric (extended knee, 90° knee flexion) and isokinetic conditions (extended knee), respectively.

Results

After 58 days of wearing the orthosis the percentage loss of volume in the entire triceps surae muscle of the control subjects (-11.9 ± 4.4%, mean ± standard deviation) was reduced by the countermeasure (-3.5 ± 7.2%, p = 0.032). Wearing the orthosis generally reduced plantar flexion torques values, however, only when testing isometric contraction at 90° knee ankle the countermeasure effected a significantly lower percentage decrease of torque (-9.7 ± 7.2%, mean ± SD) in comparison with controls (-22.3 ± 11.2%, p = 0.032).

Conclusion

Unloading of calf musculature by an orthotic device resulted in the expected loss of muscle volume and maximum of plantar flexion torque. Neuromuscular electrical muscle stimulation and lupin protein supplementation could significantly reduce the process of atrophy.

Trial registration

ClinicalTrials.gov, identifier NCT02698878

Electrical stimulation influences satellite cell proliferation and apoptosis in unloading-induced muscle atrophy in mice

Muscle atrophy caused by disuse is accompanied by adverse physiological and functional consequences. Satellite cells are the primary source of skeletal muscle regeneration. Satellite cell dysfunction, as a result of impaired proliferative potential and/or increased apoptosis, is thought to be one of the causes contributing to the decreased muscle regeneration capacity in atrophy. We have previously shown that electrical stimulation improved satellite cell dysfunction. Here we test whether electrical stimulation can also enhance satellite cell proliferative potential as well as suppress apoptotic cell death in disuse-induced muscle atrophy. Eight-week-old male BALB/c mice were subjected to a 14-day hindlimb unloading procedure. During that period, one limb (HU-ES) received electrical stimulation (frequency: 20 Hz; duration: 3 h, twice daily) while the contralateral limb served as control (HU). Immunohistochemistry and western blotting techniques were used to characterize specific proteins in cell proliferation and apoptosis. The HU-ES soleus muscles showed significant improvement in muscle mass, cross-sectional area, and peak tetanic force relative to the HU limb (p<0.05). The satellite cell proliferative activity as detected within the BrdU+/Pax7+ population was significantly higher (p<0.05). The apoptotic myonuclei (detected by terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling) and the apoptotic satellite cells (detected by cleaved Poly [ADP-ribose] polymerase co-labeled with Pax7) were reduced (p<0.05) in the HU-ES limb. Furthermore the apoptosis-inducing factor and cleaved caspase-3 were down-regulated while the anti-apoptotic Bcl-2 protein was up-regulated (p<0.05), in the HU-ES limb. These findings suggest that the electrical stimulation paradigm provides an effective stimulus to rescue the loss of myonuclei and satellite cells in disuse muscle atrophy, thus maintaining a viable satellite cell pool for subsequent muscle regeneration. Optimization of stimulation parameters may enhance the outcome of the intervention.

The effects of low frequency electrical stimulation on satellite cell activity in rat skeletal muscle during hindlimb suspension

Background

The ability of skeletal muscle to grow and regenerate is dependent on resident stem cells called satellite cells. It has been shown that chronic hindlimb unloading downregulates the satellite cell activity. This study investigated the role of low-frequency electrical stimulation on satellite cell activity during a 28 d hindlimb suspension in rats.

Results

Mechanical unloading resulted in a 44% reduction in the myofiber cross-sectional area as well as a 29% and 34% reduction in the number of myonuclei and myonuclear domains, respectively, in the soleus muscles (P < 0.001 vs the weight-bearing control). The number of quiescent (M-cadherin⁺), proliferating (BrdU⁺ and myoD⁺), and differentiated (myogenin⁺) satellite cells was also reduced by 48-57% compared to the weight-bearing animals (P < 0.01 for all). Daily application of electrical stimulation (2 × 3 h at a 20 Hz frequency) partially attenuated the reduction of the fiber cross-sectional area, satellite cell activity, and myonuclear domain (P < 0.05 for all). Extensor digitorum longus muscles were not significantly altered by hindlimb unloading.

Conclusion

This study shows that electrical stimulation partially attenuated the decrease in muscle size and satellite cells during hindlimb unloading. The causal relationship between satellite cell activation and electrical stimulation remain to be established.

Alterations of protein turnover underlying disuse atrophy in human skeletal muscle

Unloading-induced atrophy is a relatively uncomplicated form of muscle loss, dependent almost solely on the loss of mechanical input, whereas in disease states associated with inflammation (cancer cachexia, AIDS, burns, sepsis, and uremia), there is a procatabolic hormonal and cytokine environment. It is therefore predictable that muscle loss mainly due to disuse alone would be governed by mechanisms somewhat differently from those in inflammatory states. We suggest that in vivo measurements made in human subjects using arterial-venous balance, tracer dilution, and tracer incorporation are dynamic and thus robust by comparison with static measurements of mRNA abundance and protein expression and/or phosphorylation in human muscle. In addition, measurements made with cultured cells or in animal models, all of which have often been used to infer alterations of protein turnover, appear to be different from results obtained in immobilized human muscle in vivo. In vivo measurements of human muscle protein turnover in disuse show that the primary variable that changes facilitating the loss of muscle mass is protein synthesis, which is reduced in both the postabsorptive and postprandial states; muscle proteolysis itself appears not to be elevated. The depressed postprandial protein synthetic response (a phenomenon we term "anabolic resistance") may even be accompanied by a diminished suppression of proteolysis. We therefore propose that most of the loss of muscle mass during disuse atrophy can be accounted for by a depression in the rate of protein synthesis. Thus the normal diurnal fasted-to-fed cycle of protein balance is disrupted and, by default, proteolysis becomes dominant but is not enhanced.

The effects of frequency-dependent dynamic muscle stimulation on inhibition of trabecular bone loss in a disuse model

Clinical electrical muscle stimulation has been shown to alleviate muscle atrophy resulting from functional disuse, yet little is known about its effect on the skeleton. The objective of this study is to evaluate the potential of dynamic muscle stimulation on disused trabecular bone, and to investigate the importance of optimized stimulation frequency in the loading regimen. Fifty-six skeletally mature Sprague-Dawley rats were divided into seven groups for the 4-week experiment: baseline control, age-matched control, hindlimb suspended (HLS), and HLS with muscle stimulation at 1 Hz, 20 Hz, 50 Hz, and 100 Hz. Muscle stimulation was carried out for 10 min per day for 5 days per week, total of 4 weeks. The metaphyseal and epiphyseal trabecular regions of the distal femurs were analyzed with microcomputed tomography and histomorphometry methods. HLS alone for 4-week resulted in a significant amount of trabecular bone loss and structural deterioration. Muscle contraction at 1 Hz was not sufficient to inhibit trabecular bone loss and resulted in similar amount of loss to that of HLS alone. Bone quantity and structure were significantly improved by applying muscle stimulation at mid-frequency (20 Hz and 50 Hz). Dynamic stimulation at 50 Hz demonstrated the greatest preventive effect on the skeleton against functional disused alone animals (up to +147% in bone volume fraction, +38% in trabecular number and -36% in trabecular separation). Histomorphometric analysis showed that the stimulation, regardless of its frequency, did not have an effect on the bone formation indices, such as mineral apposition rate and bone formation rate. Overall, the data demonstrated the potentials of frequency-dependent dynamic muscle contraction in regulating skeletal adaptive responses under disuse conditions. Dynamic muscle stimulation, with a specific regimen, may be beneficial to future orthopedic research in developing a countermeasure for disuse osteopenia and osteoporosis.

Staging of disuse atrophy of skeletal muscles on immunofluorescence microscopy

The Japanese population is rapidly aging, thereby causing excess demand for facilities for elderly invalids. It is imperative that social measures and scientific studies be carried out to enable better care of bedridden elderly people. The purpose of the present study was to review the histological changes that occur in disuse atrophy of skeletal muscles, the primary pathophysiology of bedridden invalids, with the object of developing a staging standard to be used by researchers and clinicians. Rat hindlimb suspension was used as an experimental model. Atrophy of the soleus muscle was evaluated qualitatively and quantitatively on immunofluorescence microscopy. The myofibrils decreased significantly in the first 2-3 weeks of disuse atrophy. The earliest morphological change was fan-shaped multistep forking of sarcomeres, which appeared by the first week. This type of muscular lesion, designated here as 'sarcomeric disarray', was first described in the present study. Central-core lesions appeared mainly in slow muscle fibers by the second week. These lesions disappeared by the fourth or fifth week. Nerves remained intact and no inflammation or regeneration occurred up to the fifth week. Methods and criteria were compiled for staging of disuse atrophy based on the present results and a diagnosis kit designed for studies on disuse atrophy of skeletal muscles.

Estimulação elétrica neuromuscular em cães com atrofia muscular induzida

Empregou-se a estimulação elétrica neuromuscular (EENM) de baixa freqüência no músculo quadríceps femoral de cães com atrofia induzida e avaliou-se a ocorrência de ganho de massa nessa musculatura. Foram utilizados oito cães com pesos entre 15 e 30kg, distribuídos aleatoriamente em dois grupos denominados de I ou controle e II ou tratado. A articulação femorotibiopatelar esquerda foi imobilizada por 30 dias pelo método de transfixação percutânea tipo II, com retirada de aparelho de imobilização após esse período. Decorridas 48 horas da remoção, foi realizada a EENM nos cães do grupo II, cinco vezes por semana, com intervalo de 24 horas cada sessão, pelo período de 60 dias. Foram avaliadas a circunferência da coxa, a goniometria do joelho, a análise clínica da marcha, as enzimas creatina-quinase (CK) e aspartato-amino-transferase (AST) e a morfometria das fibras musculares em cortes transversais do músculo vasto lateral colhido mediante biópsia muscular. A EENM foi empregada no músculo quadríceps femoral na freqüência de 50Hz, duração de pulso de 300 milisegundos e relação de tempo on/off de 1:2. Quanto à morfometria das fibras do músculo vasto lateral, no grupo tratado houve aumento significativo (P<0,05) da área transversal aos 90 dias em relação ao dia zero. A EENM de baixa freqüência ocasiona hipertrofia do músculo vasto lateral em cães após a imobilização rígida temporária da articulação do joelho.

Neuromuscular electrical stimulation in neurorehabilitation

This review provides a comprehensive overview of the clinical uses of neuromuscular electrical stimulation (NMES) for functional and therapeutic applications in subjects with spinal cord injury or stroke. Functional applications refer to the use of NMES to activate paralyzed muscles in precise sequence and magnitude to directly accomplish functional tasks. In therapeutic applications, NMES may lead to a specific effect that enhances function, but does not directly provide function. The specific neuroprosthetic or "functional" applications reviewed in this article include upper- and lower-limb motor movement for self-care tasks and mobility, respectively, bladder function, and respiratory control. Specific therapeutic applications include motor relearning, reduction of hemiplegic shoulder pain, muscle strengthening, prevention of muscle atrophy, prophylaxis of deep venous thrombosis, improvement of tissue oxygenation and peripheral hemodynamic functioning, and cardiopulmonary conditioning. Perspectives on future developments and clinical applications of NMES are presented.

The BION devices: injectable interfaces with peripheral nerves and muscles

Object

The purpose of this study was to describe a novel technology for implantable neuromuscular stimulation to treat complications of paralysis and disuse atrophy, including shoulder subluxation, hand contractures, drop foot, and osteoarthritis. The authors review the results so far of several pilot clinical studies of these muscle stimulation devices.

Methods

Miniature wireless stimulators received power and individually addressed command signals from an external radiofrequency transmission coil. One or more implants were injected through a 12-gauge hypodermic insertion tool into muscles or adjacent to motor nerves, where they provided the means to activate the muscles in any desired pattern of intensity and frequency. Randomized controlled studies in small numbers of patients are underway to identify efficacy, acceptability, best methods of practice, and any design changes that may be required to improve the technology.

Fifty patients have been enrolled in five studies; 35 patients have undergone implantation of a total of 79 BION1 devices. Comparisons with surface stimulation in patients who have suffered a stroke with shoulder subluxation and hand contractures show similar improvements in objective measures of efficacy but higher comfort levels for stimulation by implants.

Conclusions

Injected microstimulators represent a promising new class of technology for the rehabilitation of patients with upper motor neuropathies. As the technology evolves, practitioners may be able to use it to facilitate functional reanimation of paralyzed limbs.

Nerve injury about the shoulder in athletes, part 1: suprascapular nerve and axillary nerve

Nerve injuries about the shoulder in athletes are being recognized with increasing frequency. Prompt and correct diagnosis of these injuries is important to treat the patient and to understand the potential complications and natural history so as to appropriately counsel athletes. This 2-part article is a review and an overview of the current state of knowledge regarding some of the more common nerve injuries seen about the shoulder in athletes.