Deltoid Activity Research Articles

Selective Activation of the Infraspinatus During External Rotation Exercises in Participants with Rounded Shoulder Posture: Comparison of Three Common Exercises and Muscle Architecture-Based Exercise

Background and Objectives: The infraspinatus muscle is critical for shoulder stability and external rotation, yet achieving selective activation during exercises remains challenging. This study explores the effectiveness of a novel muscle architecture-based position (MABER) compared to traditional exercises in individuals with rounded shoulder posture. Materials and Methods: This prospective, cross-sectional study evaluated the selective activation of the infraspinatus during external rotation exercises in participants with rounded shoulder posture. Thirty-two participants (17 males and 15 females) were recruited. Electromyographic (EMG) activity of the middle trapezius, posterior deltoid, and infraspinatus muscles in the dominant limb was recorded during four exercise positions: standing external rotation (SER), side-lying external rotation (SDER), scapular plane external rotation (SPER), and MABER. Results: MABER produced the highest infraspinatus activity (p < 0.001), while the lowest activity was observed during SPER (p < 0.001). The SER position generated higher posterior deltoid activity compared to other positions (p < 0.001). The SDER position demonstrated the highest infraspinatus/posterior deltoid activity ratio (p < 0.001). Conclusions: The MABER position can be used as an effective exercise to strengthen the infraspinatus muscle. This study contributes to the literature by comparing MABER with traditional exercises and highlights its potential benefits for individuals with rounded shoulder posture.

Differential effect of three types of exoskeletons and handling height on muscular activity, postural control and perceived effort during simulated bedside mobilization task.

Home care workers are affected by musculoskeletal disorders caused by biomechanical factors. This study investigated the effect of three exoskeletons devices (HAPO, HAPO FRONT and Japet.W) during load mobilization tasks at three bed heights in order to reduce physical risk factor. Anterior deltoid and longissimus bilateral muscular activities were recorded by EMG, a force platform was used to record center of pressure (CoP) displacement, and perceived exertion parameters were assessed using the Borg scale while nineteen healthy subjects performed a load manipulation. The use of the HAPO FRONT decreased global muscular activity by 5,6% and deltoid activity by 10,7%, exoskeletons reduced perceived effort, from 42% to 25%. Bed height has an inverse effect on deltoid and longissimus activity. These findings show that exoskeletons can reduce perceived effort and for overall and deltoids muscular activity. Therefore, the combination of shoulder and low back assistance appears as an interesting line of thought.

A study of effective exercise methods and resistance intensity for selective strengthening of the infraspinatus muscle

Background To selectively strengthen target muscles, resistance intensity as well as limb position should be considered. Objective This study aimed to identify the most effective exercise positions and the optimal resistance intensity to selectively strengthen the infraspinatus muscle. Methods This study included 18 healthy men who underwent four different external rotation (ER) exercises in prone external rotation (PER), side-lying wiper, sitting external rotation, and standing external rotation (STER) exercise by varying the shoulder positions under low, medium, and high resistance intensity conditions randomly. Infraspinatus and posterior deltoid muscle activities and the infraspinatus to posterior deltoid activity ratio were measured based on ER exercise positions and resistance intensities. Results This study revealed a significant interaction and main effects of exercise position and resistance intensity on muscle activity and muscle activity ratio. Both muscle activities were increased as the resistance intensity increased, but the muscle activity ratio was decreased. Infraspinatus muscle activity and muscle activity ratio were higher in the PER and STER exercises than in other exercises. Conclusion We indicate that PER and STER are effective exercises to selectively strengthen the infraspinatus muscle. Additionally, performing the exercise at low or medium resistance intensity rather than high resistance intensity is recommended to activate the infraspinatus selectively while minimizing the involvement of the posterior deltoid.

Biomechanical Evaluation of Physical Examination Tests for Rotator Cuff Tears - A Computer Simulation Study.

Numerous physical diagnostic shoulder tests have been established to determine the presence of rotator cuff tears and to identify the affected muscles. However, reported sensitivities and specificities of these tests vary strongly. The aim of this study was to identify diagnostic postures that are biomechanically most sensitive in identifying rotator cuff lesions and compensation mechanisms. A musculoskeletal modelling study investigating muscle activity in healthy shoulders as well as in shoulders with anterior, superior, and posterosuperior rotator cuff tear patterns, was conducted. Muscle moment arms and muscle synergism for the Lift-off and Bear Hug tests, Jobe and Full-can tests and Infraspinatus and Hornblower tests were compared for healthy and pathological models. In a healthy model the Lift-off test showed significantly higher subscapularis activity compared to the Bear Hug test (p<0.001). Teres minor and infraspinatus activity were threefold and twofold higher, in the Hornblower than the Infraspinatus test, respectively. In superior tests, supraspinatus activity was more than twofold lower than lateral deltoid activity and synergistic activity increase was smallest (Δ 1-3% in deltoid). Activity increase was highest in posterosuperior tests for the teres minor with 66.4% activity increase in the Infraspinatus test (p<0.001) and 81.3% increase in the Hornblower test (p<0.001). The Lift-off test was significantly more sensitive in detecting subscapularis tears and the Hornblower test was more effective in assessing teres minor integrity in posterosuperior tears. Both, Jobe and Full-can tests demonstrated low biomechanical sensitivity in the detection of superior rotator cuff tears.

The use of lifting straps during snatch alters muscle activation patterns

The snatch is prevalent in competitive and recreational lifting as well as strength training. Lifting straps (LS) are an accessory that wrap around the hand and the barbell, reducing the limitations of grip strength. However, this benefit has not been quantitatively supported for the snatch. The aim of this study was to compare muscle activation patterns between using LS and not using them at 80% of the snatch one-repetition maximum in a group of twelve sub-elite male weightlifters. It was hypothesized that LS would decrease forearm muscle activation and increase larger muscle group activation. Eight dominant-side muscles located in the lower limbs, back, shoulders, and upper limbs were measured via electromyography. A two-way analysis of variance (ANOVA), followed by a Tukey Pairwise comparison, revealed that LS significantly impacted (p = 0.039) muscle activation in the snatch. Specifically, latissimus dorsi activation increased the most (17.2 ± 55.7%), while biceps brachii activation decreased the most (−8.0 ± 37.0%). Comparing muscle activation across different phases of the lift showed that LS decreased forearm and bicep brachii activation by 16.0 ± 25.2% and 7.1 ± 35.7% respectively during the pull phase, and increased vastus lateralis, latissimus dorsi, and medial deltoid activation between the second part of the first pull and the catching position, with a corrected effect size exceeding 1.5. These results support the hypothesis that LS decrease forearm activation, which could reduce grip strength limitations and consequently, reduce problems associated with fatigue. Increases in vastus lateralis activation with the use of LS suggest a greater training stimulus during the snatch, which can help develop leg strength.

Effects of Kitchen Cooking Height on Upper Limb Muscle Activation, Posture, and Perceived Discomfort of Chinese Older and Young Women.

Inappropriate kitchen cooking height may lead to uncomfortable and muscle fatigue. This study aims to compare the effects of kitchen cooking height on upper limb muscle activation, posture, and perceived discomfort among different age groups. Fifteen older women and fifteen young Chinese women each completed three consecutive 20 s simulated cooking tasks at five different heights. Surface electromyography, motion capture, and Borg CR10 scale were used to measure muscle loading. Results showed that the main power muscles of the cooking task were the anterior deltoid, brachioradialis, and biceps brachii. The higher muscle contribution rate of biceps brachii and triceps brachii was found in the younger group compared to the older group (p < 0.05). Muscle activation of the anterior deltoid (different in 1.28-2.87%), pectoralis major (different in 1.43-1.69%), and erector spinae (different in 0.6-1.21%), as well as right shoulder abduction (different in 5.91°-7.96°), were significantly higher in older group than in young group (p < 0.05). Muscle activation of the anterior deltoid and right shoulder abduction decreased significantly with decreasing height (p < 0.05). A height of 200-250 mm below the elbow was considered a more comfortable cooking height for both age groups. This provides data to support the design of cabinet sizes.

Investigation of musculoskeletal symptoms, work postures, quantification of muscle activity, and estimation of grip/push forces among sonographers

AbstractDue to the physical nature of their work, sonographers are exposed to many musculoskeletal disorder risk factors, including awkward posture, repetitive movements, forceful manual exertion, and static muscle contractions, especially in the upper limbs. The current study is an investigation of musculoskeletal disorders among sonographers, caused by various occupational risk factors via different sonographic scan types. During the first phase of this study, the musculoskeletal symptoms and work postures of 29 subjects were investigated. During the second phase, muscle activity was quantified, and grip/push forces were estimated using the data obtained from 10 volunteer sonographers. 82% of sonographers experienced musculoskeletal symptoms. Based on the final scores and action levels obtained via rapid upper limb assessment, while performing scans of left regions; ergonomic changes and interventions were found necessary, to relieve stress on the sonographer's body. The results of muscular activity per muscle and scan type, showed that the mean muscle activity of the middle deltoid muscle was significantly higher during the right abdominal scan (17.64% maximum voluntary contraction [MVC]), compared to those of thyroid (12.54% MVC) and left abdominal (7.32% MVC) scans. Additionally, mean grip and push forces during both abdominal scans were significantly higher than those during the thyroid scan. Despite an injury risk during all scans, risk factor impact was different among scan types. This groundbreaking study represents the first that captures and measures both grip and push forces simultaneously, which may prove helpful while investigating corrective interventions or optimizing design of sonography robots and ergonomic probes in future studies.

Effects of track-based stair climbing robot on muscle activity, usability, and psychological anxiety: a preliminary study

This study investigated the effects of using the LiftCar-150 track-based stair-climbing robot on muscle activity, usability, and psychological anxiety. While stair-climbing robots enhance mobility for individuals with physical disabilities, existing research has predominantly focused on engineering perspectives, with limited attention to user-centered outcomes. Ten healthy participants and an 80 kg dummy rider completed stair-climbing tasks at slow (5 m/min) and fast (7 m/min) speeds. Muscle activity in the middle trapezius (MT), erector spinae (ES), multifidus (MF), gluteus maximus (Gmax), gluteus medius (Gmed), and anterior deltoid (AD) muscles was recorded by electromyography. Usability was evaluated in terms of safety, efficiency, and satisfaction using a 5-point Likert scale, while psychological anxiety was assessed with a visual analog scale (VAS) ranging from 0 to 10. Results showed that during stair ascent, activities of the back extensors (ES and MF) and gluteus muscles (Gmax and Gmed) significantly increased compared to descent, while anterior deltoid activity was higher during descent. Usability scores averaged 4.05 for stability, 4.1 for efficiency, and 3.7 for satisfaction. Perceived psychological anxiety scores were 4.2 ± 0.3 and 5.4 ± 0.5 at slow speed, and 3.5 ± 0.2 and 5.7 ± 0.4 at fast speed during ascent and descent, respectively. While operators recognized the robot’s stability and efficiency, satisfaction levels were neutral, and specific muscle activation was increased. These findings provide essential insights into optimizing the design and usability of stair-climbing robots to better address user needs.

Design and evaluation of the OmniSuit: A passive occupational exoskeleton for back and shoulder support

Many physically straining occupations involve lifting movements over the full-vertical range of motion, which over time may lead to the development of musculoskeletal injuries. To address this, occupational exoskeletons can be designed to provide meaningful support to the back and shoulders during lifting movements.This paper introduces the main functional design features of the OmniSuit, a novel passive occupational exoskeleton. We present the technical and biomechanical considerations for the expected support level, as well as an evaluation of the physiological benefit and usability of the exoskeleton in a sample of 31 healthy volunteers performing physically demanding tasks in a laboratory setting.The OmniSuit exoskeleton significantly reduced Deltoid, Trapezius and Erector Spinae muscle activity between 4.1%MVC and 15.7%MVC when lifting a 2.5kg weight above shoulder level (p<0.001), corresponding to a reduction of up to 49.1% compared to without exoskeleton. A position-dependent reduction of Erector Spinae muscle activity was observed (p<0.001), with reductions ranging between 4.6%MVC and 14.0%MVC during leaning and squatting, corresponding to a reduction up to 41.5% compared to without exoskeleton. The measured muscular support and the predicted support torque based on the biomechanical model were found to show a similar profile for those phases of the movement which are most straining to the shoulder and back muscles. Participants reported experiencing good device usability and minimal discomfort (<1/10) in the shoulder and back during task execution with exoskeleton support.These first results validate that the considered biomechanical model helped design an ergonomic and efficient exoskeleton, and confirm the potential of such wearable assistive devices to provide support over multiple joints during physically demanding tasks.

Electromyography of shoulder muscles in individuals without scapular dyskinesis during closed kinetic chain exercises on stable and unstable surfaces: a systematic review and meta-analysis.

Unstable surfaces are commonly utilized to enhance the flexibility of the musculoskeletal system for achieving training or rehabilitation goals. However, their effects on shoulder muscle activation during various push-up (PU) exercises have not been thoroughly investigated. Therefore, the purpose of this study was to synthesize electromyography (EMG) data of shoulder muscles in individuals without scapular dyskinesis performing different PU exercises on both stable and unstable surfaces. A systematic online search was conducted in electronic databases, including Web of Science, PubMed, Scopus, and Google Scholar, up to January 16, 2024, using predefined sets of keywords. Out of the 1,971 titles and abstracts screened, 80 articles were reviewed in detail by two independent researchers to check the eligibility, of which 28 eligible studies were ultimately included. Following assessment of the quality and risk of bias, the studies were categorized based on exercises and muscle groups, and a meta-analysis using a random-effects model was performed to estimate the overall effect size. The use of unstable surfaces led to a decrease in anterior deltoid activity during PU [P = 0.032; I2 = 91.34%; SMD = -0.630 (95% CI -1.205, -0.055)], an increase in pectoralis major activity during PU [P = 0.006; I2 = 63.72%; SMD = 0.282 (95% CI 0.079, 0.484)], as well as during knee PU [P = 0.018; I2 = 32.29%; SMD = 0.309 (95% CI 0.052, 0.565)], and an increase in triceps brachii activity during PU [P = 0.000; I2 = 85.05%; SMD = 0.813 (95% CI 0.457, 1.168)], knee PU [P = 0.000; I2 = 0.00%; SMD = 0.589 (95% CI 0.288, 0.891)], as well as during push-up plus [P = 0.006; I2 = 13.16%; SMD = 0.563 (95% CI 0.161, 0.965)]. However, the use of unstable surfaces did not show a significant effect on the EMG activity of the pectoralis major during push-up plus [P = 0.312; I2 = 22.82%; SMD = 0.207 (95% CI -0.194, 0.609)]. Unstable surfaces can modulate muscle activity in different PU exercises, while the effects on the targeted muscles depend on the type of exercise. The findings of this review provide a framework based on the level of activity of each shoulder muscle during different PU exercises, which can help coaches, trainers, and sports therapists select the most suitable type of PU for designing training or rehabilitation programs. Particularly, the most suitable exercise for increasing anterior deltoid activity is PU on a stable surface. To concurrently increase activity of the pectoralis major and triceps brachii, adding unstable surfaces under hands during knee PU and standard PU is recommended. PROSPERO, identifier CRD42021268465.

Human-exoskeleton cooperation for reducing the musculoskeletal load of manual handling tasks in orchid farms

Work-related musculoskeletal diseases of the lower back and shoulders are frequently caused by lifting, carrying and trunk bending. Therefore, a hybrid exoskeleton (HExo) that provides external torque to the upper extremities and back may reduce discomfort in the lower back and shoulder tendinopathies. In this study, we designed and fabricated HExo, a novel upper-limb and lower-back combined exoskeleton, and evaluated its impact in reducing the musculoskeletal load on the shoulder and back during agricultural work in orchid farms. The human motion tracking technique was utilised to collect the joint angles of orchid farmers during their work, and the joint angle data were subsequently used for the design of HExo. Electromyography (EMG) and centre of pressure (CoP) measurements were taken for 5 participants performing farm tasks and 16 participants performing laboratory-standardised tasks both with and without the HExo. The amplitude probability density function and Wilcoxon signed rank test were utilised in the data analysis to verify the advantage in wearing HExo. The use of HExo resulted in a reduction in erector spinae, latissimus dorsi and anterior deltoid muscle activation of up to 36.92 % (p = 0.05), 31.43 % (p = 0.017), and 57.59 % (p = 0.012), respectively. Furthermore, its use did not affect the ability of participants to maintain balance. Hence, HExo could be a promising for reducing solution musculoskeletal load.

Responsiveness to exoskeleton loading during bimanual reaching is associated with corticospinal tract integrity in stroke.

Device-based rehabilitation of upper extremity impairment following stroke often employs one-sized-fits-all approaches that do not account for individual differences in patient characteristics. Determine if corticospinal tract lesion load could explain individual differences in the responsiveness to exoskeleton loading of the arms in chronic stroke participants. Fourteen stroke participants performed a bimanual shared cursor reaching task in virtual reality while exoskeletons decreased the effective weight of the more-impaired arm and increased the effective weight of the less-impaired arm. We calculated the change in relative displacement between the arms (RC) and the change in relative muscle activity (MC) between the arms from the biceps and deltoids. We calculated corticospinal tract lesion load (wCSTLL) in a subset of 10 participants. Exoskeleton loading did not change RC (p = 0.07) or MC (p = 0.47) at the group level, but significant individual differences emerged. Participants with little overlap between the lesion and corticospinal tract responded to loading by decreasing muscle activity in the more-impaired arm relative to the less-impaired arm. The change in deltoid MC was associated with smaller wCSTLL (R2 = 0.43, p = 0.039); there was no such relationship for biceps MC (R2 < 0.001, p = 0.98). Here we provide evidence that corticospinal tract integrity is a critical feature that determines one's ability to respond to upper extremity exoskeleton loading. Our work contributes to the development of personalized device-based interventions that would allow clinicians and researchers to titrate constraint levels during bimanual activities.

A muscle synergies-based controller to drive a powered upper-limb exoskeleton in reaching tasks.

This work introduces a real-time intention decoding algorithm grounded in muscle synergies (Syn-ID). The algorithm detects the electromyographic (EMG) onset and infers the direction of the movement during reaching tasks to control a powered shoulder-elbow exoskeleton. Features related to muscle synergies are used in a Gaussian Mixture Model and probability accumulation-based logic to infer the user's movement direction. The performance of the algorithm was verified by a feasibility study including eight healthy participants. The experiments comprised a transparent session, during which the exoskeleton did not provide any assistance, and an assistive session in which the Syn-ID strategy was employed. Participants were asked to reach eight targets equally spaced on a circumference of 25 cm radius (adjusted chance level: 18.1%). The results showed an average accuracy of 48.7% after 0.6 s from the EMG onset. Most of the confusion of the estimate was found along directions adjacent to the actual one (type 1 error: 33.4%). Effects of the assistance were observed in a statistically significant reduction in the activation of Posterior Deltoid and Triceps Brachii. The final positions of the movements during the assistive session were on average 1.42 cm far from the expected ones, both when the directions were estimated correctly and when type 1 errors occurred. Therefore, combining accurate estimates with type 1 errors, we computed a modified accuracy of 82.10±6.34%. Results were benchmarked with respect to a purely kinematics-based approach. The Syn-ID showed better performance in the first portion of the movement (0.14 s after EMG onset).

Sensorless model-based tension control for a cable-driven exosuit.

Cable-driven exosuits have the potential to support individuals with motor disabilities across the continuum of care. When supporting a limb with a cable, force sensors are often used to measure tension. However, force sensors add cost, complexity, and distal components. This paper presents a design and control approach to remove the force sensor from an upper limb cable-driven exosuit. A mechanical design for the exosuit was developed to maximize passive transparency. Then, a data-driven friction identification was conducted on a mannequin test bench to design a model-based tension controller. Seventeen healthy participants raised and lowered their right arms to evaluate tension tracking, movement quality, and muscular effort. Questionnaires on discomfort, physical exertion, and fatigue were collected. The proposed strategy allowed tracking the desired assistive torque with a root mean square error of 0.71Nm (18%) at 50% gravity support. During the raising phase, the electromyography signals of the anterior deltoid, trapezius, and pectoralis major were reduced on average compared to the no-suit condition by 30, 38, and 38%, respectively. The posterior deltoid activity was increased by 32% during lowering. Position tracking was not significantly altered, whereas movement smoothness significantly decreased. This work demonstrates the feasibility and effectiveness of removing the force sensor from a cable-driven exosuit. A significant increase in discomfort in the lower neck and right shoulder indicated that the ergonomics of the suit could be improved. Overall this work paves the way toward simpler and more affordable exosuits.

Experimental Analysis of the Efficiency and Usability of Tylke Versus Magill Forceps.

The procedure of nasotracheal intubation (NI) has long been performed utilizing the Magill forceps as developed by Sir Ivan Magill in the 1920s. While used for nearly a century, several serious patient safety concerns remain including torn tube cuffs, vocal cord trauma, and inefficient tube placement. The Tylke forceps have been developed as a modification to the largely unchanged form of Magill forceps. In the present investigationwe compared the efficacy, number of clasps, and muscle activation involved in NI using the Tylke forceps versus the Magill forceps in previously untrained individuals. Tylke forceps showed faster successful NI over the standard Magill forceps at an average intubation time of 6.54s vs. 13.73s, respectively. Tylke forceps also had fewer clasps per intubation over the Magill. The trapezius, deltoid, and brachioradialis muscle activation was also compared in Tylke vs Magill forceps intubation trials. Tylke forceps required less lower muscle activation in the brachioradialis and trapezius over the Magill forceps with Tylke forceps resulting in higher deltoid muscle activation. Tylke forceps were more efficacious and reduced the number of clasps over the Magill forceps when used in successful NI with different muscle activation patterns.

Upper limb biomechanical differences in volleyball spikes among young female players

The performance assessment of relevant biomechanical factors is essential for appropriate age-related training progression in volleyball spike (VS). This study aimed to investigate the differences in upper limbs’ (a) range of motion (ROM), (b) angular velocities, and (c) muscular activity during VS among under 16- (U-16), under 18- (U-18), and under 20- (U-20) year-old female volleyball players. The kinematic variables of the spike performances were recorded using six optoelectronic cameras (Vicon Motion system, UK). Additionally, the wireless Trigno system (Delsys, USA) was used to record the electromyographic signals. The one-way ANOVA (1d SPM analysis) exhibited a significantly greater wrist internal rotation ( p &lt; .001), wrist adduction velocity (p &lt; .001), and palmaris longus activity ( p &lt; .001) in the acceleration phase in U-20, compared to the U-16 group. Additionally, the U-20 and the U-18 players portrayed a significantly greater shoulder external rotation ( p &lt; .001) and internal angular velocity ( p = .035) relative to the U-16 group. A significantly greater pectoralis major (p &lt; .001), biceps brachii ( p &lt; .001), and anterior deltoid ( p &lt; .001) activity was observed in the U-20 group, compared to younger groups. This study suggests that older players employ more upper limb muscular activities during spike with the presence of blocks, which enables them to hit the ball with greater velocities and direct the ball in their desired direction through increased wrist ROMs.

Variability analysis of muscle activation symmetry to identify indicators of individual motor strategy: a case series on elite Paralympic powerlifters.

In Paralympic powerlifting competitions, movement execution symmetry is a technical requirement influenced by individual athlete characteristics and motor strategies. Identifying the elements associated with individual motor strategies can offer valuable insight for improving sport performance. Therefore, this case series study aimed to explore muscle activation symmetry and its intra- and inter-individual variability to determine the muscles mostly related to individual motor strategies in elite Paralympic powerlifters. Bilateral electromyographic activation of the anterior deltoid (AD), pectoralis major (PM), latissimus dorsi (LD), triceps (TRI) and external oblique (EO) muscles were analysed in five elite Paralympic powerlifters while performing four sets of one-repetition maximum of Paralympic bench press. Muscle activation symmetry indexes (SI) were obtained and transformed to consider individual-independent evaluation. The coefficient of variation (CV), variance ratio (VR), and mean deviation (MD) were computed to assess inter- and intra-individual variability in electromyographic waveforms and SI. Both transformed and non-transformed SI indicated overall symmetric activation in DA, PM, TRI, and LD. Transformed SI revealed asymmetrical muscle activation of EO when grouping data (mean bilateral difference: 10%). Athletes exhibited low intra-individual SI variability in all analysed muscles (CV < 10%) and low inter-individual variability in DA, PM, LD, and TRI (CV < 10%; VR: 4%-11%; MD: 29%-43%). In contrast, higher inter-individual variability was observed in EO (CV: 23%; VR: 23%; MD: 72%-81%). The highest variability and asymmetry in abdominal muscle activation among athletes emphasize the importance of personalized training approaches for targeting these muscles due to their role in individualizing motor strategies.

Efficacy of upper limb training on grip strength and muscle activity in individuals with type 2 diabetes: a feasibility study

Abstract The upper limb (UL) is one of the important target for musculoskeletal complications in patients with diabetes. The objective of this trial was to measure the feasibility and clinical effectiveness of upper limb training on grip strength and muscle activity in individuals with Type 2 Diabetes mellitus (T2DM). A parallel three-arm randomised controlled trial (RCT) was employed. Fifty-seven patients with T2DM aged between 35 to 60 years were recruited based on eligibility criteria and asked to visit the outpatient department (OPD) of physiotherapy. They were randomly allocated into 3 groups; resistance training (RT) group; sensorimotor training (SMT) group; and control group with the help of a computer-generated random number table. Primary outcome measures were recruitment rate, outcome measure, retention rate, adherence, and acceptability of the intervention to assess trial feasibility. The efficacy of training on grip strength and on activation of deltoid, bicep and triceps brachii after 6 weeks was measured using a JAMAR hand dynamometer and S4-channel Neurostim EMG/NCV/EP system, respectively. The feasibility of recruitment rate of participants was 72.15%, outcome measures feasibility was 81%, retention rate of participants was 81% and intervention adherence was 91.34% for RT group &amp; 87.41% for SMT group. Most of the participants were satisfied with the given intervention as the acceptance rate was high. Between and within-group analysis of muscular activity and strength shows a significant difference as the P-value was &lt; 0.05. RT group shows maximum improvement in both outcome measures. This study was feasible and well accepted by participants. Therefore, it is possible to perform a fully powered RCT and to use upper limb training in the future for good clinical management in type 2 diabetic population. This trial was registered under the Clinical Trial Registry of India (CTRI) with registration no. CTRI/2021/06/034188.

Alterations in the preferred direction of individual arm muscle activation after stroke.

Stroke survivors have challenges appropriately coordinating the multiple muscles, resulting in a deficit in motor control. Therefore, comprehending the mechanism underlying abnormal intermuscular coordination becomes crucial in developing effective rehabilitation strategies. Quantitative analyses have been employed at pairwise or multi-dimensional levels to understand the underlying mechanism of abnormal intermuscular coordination and its relationship to motor impairment. However, how alterations in individual muscle activation contribute to abnormal intermuscular coordination, motor impairment, and motor performance remains unclear. Thus, we investigated the alterations in the preferred direction of individual muscles after stroke and their relationship with stroke-induced changes in intermuscular coordination, clinical motor impairment, and qualities of motor performance during isometric force generation in the upper extremity. Twenty-four stroke survivors and six age-matched controls were recruited and performed isometric force target matches while recording electromyographic signals from eight upper limb muscles. We determined the preferred activation direction of each muscle, evaluated abnormal intermuscular coordination through a muscle synergy analysis, assessed motor impairment using upper extremity Fugl-Meyer Assessment scores, and examined motor performance characteristics defined by force trajectory features. The post-stroke alterations in the preferred direction of the brachioradialis, anterior, middle, and posterior deltoid were correlated with the motor impairment level and attributed to the changes in muscle synergy characteristics. Only alterations in the preferred direction of the brachioradialis and posterior deltoid activation in forward-backward and upward-downward axes were associated with the qualities of isometric force generation, respectively. These findings imply that alterations in the preferred direction of individual muscle activation contribute to various aspects of motor deficit following stroke. This insight may serve as a foundation for the development of innovative stroke neurorehabilitation approaches that take into account specific attributes of individual muscle activation, including their preferred activation direction.

Effects of Pseudo-Weight Resistance Training Using Mixed-Reality Technology on Muscle Activation in Healthy Adults: A Preliminary Study

The present study investigated the feasibility and effectiveness of pseudo-weight resistance training using mixed-reality (MR) technology for shoulder muscle activation in healthy individuals. Thirty-two healthy students aged 20~35 years participated in this preliminary study and were divided into two groups. Participants in the MR group received 30 min of training three times a week for 4 weeks using a customized MR-based pseudo-weight resistance training system. Those in the control group performed the same exercises using a conventional training program. Muscle activation of the deltoids, upper trapezius, infraspinatus, and supraspinatus were measured before and after the intervention. There was a statistically significant difference in middle deltoid, upper trapezius, and supraspinatus muscle activation in the MR group (p &lt; 0.05), while the control group showed a significant difference in the anterior and middle deltoid, upper trapezius, and supraspinatus (p &lt; 0.05). Regarding the between-group comparison, no statistically significant difference was observed for all six muscles (p &gt; 0.05). Without any superiority of physical weight resistance training in the pseudo-weight training program, an MR-based pseudo-weight resistance training system can potentially be used for muscle-strengthening training, especially for early rehabilitation programs. However, further study using a large sample size with a long experimental duration is needed for more evidence of the presented technology and its use in home training.