Hybrid-training method increases muscle strength and mass in the forearm without adverse effect of hand function in healthy male subjects

Hybrid Training System Consisting of Synchronized Neuromuscular Electrical Stimulation for Voluntary Exercise Using an Articular Motion Sensor

Neuromuscular electrical stimulation (NMES) is widely used for improving muscle strength, preventing muscle atrophy, and decreasing pain. Recently, NMES has become a substitute for exercise therapy for metabolism improvement and functional capacity improvement. However, NMES has several disadvantages. First, slow-twitch muscle contractions are insufficient because the recruitment pattern of NMES does not obey Henneman's size principle. Second, when using surface electrodes, it is difficult to contract deep skeletal muscles at the application site. Third, electrical stimulation causes discomfort. Therefore, we devised a simultaneous combination of NMES and voluntary muscle contractions to overcome the weak points of NMES. A hybrid training system (HTS) that resists the motion of a volitionally contracting agonist muscle with force generated by its electrically stimulated antagonist was developed as a technique to combine the application of NMES and volitional contractions. This motion sensor makes it possible to simultaneously combine voluntary movements with NMES. Our HTS synchronizes with voluntary movements, enhancing safety and reducing discomfort. This HTS enhances the exercise effect of even simple exercise. So far, our HTS has been reported to be effective for muscle strength enhancement, prevention of muscle atrophy, improvement of physical function, pain relief, enhancement of physical fitness, and improvement of metabolic function. HTS are expected to be useful methods in environments where sufficient exercise load is not available or for individuals with low exercise tolerance.

Sex differences in wrist torque and endurance-Biomechanical factors associated with developing lateral epicondylitis of the humerus

Since eccentric contractions contribute to the development of tendinopathy, sex differences in wrist torque and endurance may be involved in the pathophysiology of lateral epicondylitis and its refractoriness. Therefore, the present study investigated sex differences in wrist torque and endurance. The wrist extension and flexion torques of the 100 wrists of 25 males and 25 females were measured. The following parameters were assessed: muscle strength at the starting- and end point for the measurement, Δ muscle strength, that is, the amount of a loss over time, and the muscle endurance ratio, that is, the decrease rate over time. Each parameter in males and females was statistically analyzed. In wrist extension, muscle strength at the starting point was 6.1 Nm for males and 3.3 Nm for females (p < 0.001); Δ Muscle strength was -0.052 Nm/s for males and -0.038 Nm/s for females (p = 0.036); The muscle endurance ratio was 99.1%/s for males and 98.8%/s for females (p = 0.015). In wrist flexion, muscle strength at the starting point and absolute value of Δ muscle strength were significantly larger in males than in females; No significant difference was observed in the muscle endurance ratio in wrist flexion between males and females. These results revealed sex differences in wrist torque and endurance. The muscle endurance ratio of the wrist extensors was lower in females than in males, which suggests that females need to exert more effort to maintain the wrist extension position under resistance. This may predispose the wrist extensor muscles in females to eccentric contractions.

KiloHertz currents on aspects of muscle function: A scoping review

BACKGROUND

Neuromuscular electrical stimulation (NMES) with kiloHertz currents (kHz) is a resource used in rehabilitation for producing muscle contractions with functional objectives, resulting from the optimization of the performance of aspects of muscle function (AOMF). However, parameters such as inadequate frequency, phase duration, amplitude, and therapy time may limit the effectiveness of NMES by the absence of adequate stimuli to generate positive adaptations in the AOMF. This study aimed to present an overview of the effectiveness and dosimetry of NMES by kHz on AOMF, such as torque and hypertrophy, in healthy people.

METHODS

The study was outlined as a scoping review. From the search, 3892 studies were found of which were incorporated into Rayyan software for exclusion of duplicates and further selection by titles and abstracts, which resulted in 33 articles for this review.

RESULTS

According to the included studies, kHz can increase torque and generate hypertrophy. Only the studies with Russian current showed hypertrophy gains. Dosimetry was not always detailed in the studies, which hinders stipulating optimal parameters for kHz.

CONCLUSION

From this review, it is concluded that NMSC by kHz is a valid resource to optimize AOMF, although the dosimetric parameters are still inconsistent.

Can maximal handgrip strength and endurance be improved by an 8-week specialized strength training program in older women? A randomized controlled study

Maximal handgrip strength and endurance are important indicators of upper limb function in older adults. Up to now, there is insufficient information regarding the efficacy of specialized strength training programs for improving handgrip strength. The purpose of this study was to investigate the effectiveness of an 8-week specialized handgrip strength training program on maximal handgrip strength and endurance in healthy older women. A randomized controlled trial was performed. Thirty-six healthy older women (>65 years) were randomly divided into a training group (TG) (n = 18) and a control group (CG) (n = 18). The TG participated in an 8-week specialized handgrip strength training program using rubber balls and hand grippers (2 training sessions/week, 10-15 min, 8-15 repetitions/set, 4-6 total sets/session). Prior to and after the completion of the program, maximal handgrip strength and dynamic endurance (indices: repeated maximal repetitions and percentage change in handgrip strength between first and last 6 repetitions) were assessed in both hands. Repeated measures MANOVA results indicated that maximal handgrip strength (+9.3%-10.4%) and strength values during repeated maximal repetitions (+14% to 27%) significantly increased in TG (p < 0.001), while the percentage change in handgrip strength between the first and last 6 repetitions decreased significantly (-6%) (p < 0.05), irrespective of the tested hand. The results of this study showed that an 8-week specialized handgrip strength training program can be used effectively by athletic trainers, physical and hand therapists to counteract the detrimental effects of the aging process on maximal handgrip strength and endurance in older adults.

Measurement of wrist flexion and extension torques in different forearm positions

Background

Forceful activities of the wrist were considered to be a risk factor for the epicondylitis. However, there are still conflicting evidence concerning work-relatedness of epicondylitis. The main problem is that there is little information about which forearm postures are capable of withstanding higher torque loads and the extent of the differences in the torques generated by different forearm postures. The objective of this study was to investigate the differences in wrist flexion and extension torques among different forearm positions in healthy subjects.

Methods

Twenty wrists of 10 asymptomatic volunteers were evaluated. The apparatus to measure the wrist torque consisted of a handle with a force sensor and a table to place the forearm in different positions. The direction of the handle can change when measuring different forearm positions. The forearm of the examinee was secured to the table. The participants were asked to exert themselves in maximal isometric contraction for wrist flexion or extension, and to maintain it for 5 s. Each evaluation of the flexion and extension torque was conducted twice. Three forearm positions were evaluated: neutral, pronation, and supination. The intra-class correlation coefficients between first and second measurements were evaluated for the maximum torque. The maximum torques and flexion/extension ratio were compared among the positions. In addition, the agility and endurance for the wrist extension/flexion torques were compared among the positions.

Results

The intra-class correlation coefficients between first and second measurements were 0.928 and 0.866 for the wrist flexion and extension measurements, respectively. The highest torques for the wrist flexion and extension were observed in the supination and pronation positions, respectively (P < 0.01). There was a higher extension/flexion ratio in the supination position compared to the other positions (P < 0.05). There was a superior agility for the wrist flexion in the supination position compared to the pronation position.

Conclusions

The normal balance of the wrist flexion–extension torques in different forearm positions were characterized. This information might aid the provision of advice regarding the optimal positions for performing specific tasks and could help to elucidate the pathophysiology of epicondylitis.

Wrist flexion and extension torques measured by highly sensitive dynamometer in healthy subjects from 5 to 80 years

BACKGROUND

Wrist movements become impaired with disease progression in various neuromuscular disorders. With the development of new therapies, thorough measurement of muscle strength is crucial to document natural disease progression and to assess treatment efficacy. We developed a new dynamometer enabling wrist flexion and extension torque measurement with high sensitivity. The aims of the present study were to collect norms for healthy children and adults, to compute predictive equations, to assess the reliability of the measurements and to test the feasibility of using the device in patients with a neuromuscular disease.

METHODS

The peak isometric torque of wrist flexion and extension was measured with the MyoWrist dynamometer in 345 healthy subjects aged between 5 and 80 years old and in 9 patients with limb girdle muscle dystrophy type 2 C (LGMD2C) aged between 16 and 38 years old.

RESULTS

Predictive equations are proposed for the wrist flexion and extension strength in children and adults. Intra-rater and inter-rater reliability was good with ICCs higher than 0.9 for both wrist flexion and extension. However, retest values were significantly higher by 4% than test results. The dynamometer was applied with no difficulty to patients with LGMD2C and was sensitive enough to detect strength as weak as 0.82 N.m. From our models, we quantified the mean strength of wrist extension in LGMD2C patients to 39 ± 17% of their predicted values.

CONCLUSIONS

The MyoWrist dynamometer provides reliable and sensitive measurement of both wrist flexion and extension torques. However, a training session is recommended before starting a study as a small but significant learning effect was observed. Strength deficit can be quantified from predictive equations that were computed from norms of healthy children and adults.

Changes in diffusion tensor imaging (DTI) eigenvalues of skeletal muscle due to hybrid exercise training

Several studies have proposed the cell membrane as the main water diffusion restricting factor in the skeletal muscle cell. We sought to establish whether a particular form of exercise training (which is likely to affect only intracellular components) could affect water diffusion. The purpose of this study is to characterise prospectively the changes in diffusion tensor imaging (DTI) eigenvalues of thigh muscle resulting from hybrid training (HYBT) in patients with non-alcoholic fatty liver disease (NAFLD). Twenty-one NAFLD patients underwent HYBT for 30 minutes per day, twice a week for 6 months. Patients were scanned using DTI of the thigh pre- and post-HYBT. Fractional anisotropy (FA), apparent diffusion coefficient (ADC), the three eigenvalues lambda 1 (λ1), λ2, λ3, and the maximal cross sectional area (CSA) were measured in bilateral thigh muscles: knee flexors (biceps femoris (BF), semitendinosus (ST), semimembranous (SM)) and knee extensors (medial vastus (MV), intermediate vastus (IV), lateral vastus (LV), and rectus femoris (RF)), and compared pre- and post-HYBT by paired t-test. Muscle strength of extensors (P<0.01), but not flexors, increased significantly post-HYBT. For FA, ADC and eigenvalues, the overall picture was of increase. Some (P<0.05 in λ2 and P<0.01 in λ1) eigenvalues of flexors and all (λ1-λ3) eigenvalues of extensors increased significantly (P<0.01) post-HYBT. HYBT increased all 3 eigenvalues. We suggest this might be caused by enlargement of muscle intracellular space.

Have guidelines addressing physical activity been established in nonalcoholic fatty liver disease?

The purpose of this review was to highlight, in relation to the currently accepted pathophysiology of non-alcoholic fatty liver disease (NAFLD), the known exercise habits of patients with NAFLD and to detail the benefits of lifestyle modification with exercise (and/or physical activity) on parameters of metabolic syndrome. More rigorous, controlled studies of longer duration and defined histopathological end-points comparing exercise alone and other treatment are needed before better, evidence-based physical activity modification guidelines can be established, since several questions remain unanswered.