The Effect of Shoulder Mobilization on Scapular and Shoulder Muscle Activity During Resisted Shoulder Abduction: A Crossover Study of Asymptomatic Individuals.

OBJECTIVE: The primary aim was to investigate the effect of inferior shoulder mobilization on scapular and shoulder muscle activity during resisted shoulder abduction in asymptomatic individuals. METHODS: This was a lab-based, repeated-measures, crossover, randomized controlled study. Twenty-two participants were recruited. The order of experimental conditions was randomized. Each participant performed 5 repetitions of resisted shoulder abduction before and after the control and mobilization (grade +IV inferior shoulder mobilization, 3 sets, 60 seconds) conditions. Surface electromyography recorded the muscle activity of anterior, middle, and posterior deltoid; supraspinatus; infraspinatus; upper and lower trapezius; serratus anterior; and latissimus dorsi muscles. RESULTS: Muscle activity levels reduced for infraspinatus (11.3% MVIC, 95% CI: 1.7-20.8), middle (22.4% MVIC, 95% CI: 15.9-28.8) and posterior deltoid (8.7 % MVIC, 95% CI: 4.6-12.9), and serratus anterior (-28.1% MVIC, 95% CI: 15.6-40.8) muscles after the mobilization condition during the eccentric phase of shoulder abduction. No carryover effects were observed, and within-session reliability was excellent (intraclass correlation coefficient scores ranging from 0.94 to 0.99). CONCLUSION: Our findings suggest that inferior glenohumeral mobilization reduces activity levels of some scapular and shoulder muscles. Given the exploratory nature of our study, changes in muscle activity levels may have been found by chance. Confirmatory studies are required.

Effects of neuromuscular electrical stimulation in patients with pulmonary arterial hypertension: a randomized controlled pilot study.

BACKGROUND: Patients with pulmonary arterial hypertension (PAH) present impairments in muscle strength and exercise capacity. There is growing evidence about the benefits of neuromuscular electrical stimulation (NMES) in patients with respiratory diseases, except in patients with PAH. The aim of this study was to investigate the effects of NMES on muscle strength, and other physical and psychosocial variables in patients with PAH. METHODS: Patients with PAH were randomly divided into two groups as NMES and control. The NMES was applied to the bilateral deltoid and quadriceps femoris muscles with 50 Hz for 3 days/week, 8 weeks for the NMES group. Muscle strength, muscle cross-sectional area and thickness, arterial stiffness, exercise capacity, functional mobility and balance, balance confidence, fatigue, physical activity, and quality of life were assessed at baseline and after 8 weeks by blinded assessors. RESULTS: There was no significant difference in the demographic and clinical characteristics between the patient groups (p > 0.05). The improvements in muscle strength, muscle cross-sectional area and thickness, pulse wave velocity, exercise capacity, functional mobility and balance, balance confidence, fatigue, physical activity, and quality of life were significantly higher in the NMES group compared to the control group (p < 0.05). CONCLUSIONS: This study suggests that NMES intervention is safe and effective for patients with PAH.

Assessing the physiological strain of physical therapists according to work experience: A cross-sectional study.

OBJECTIVES: This cross-sectional study aimed to assess the physiological response of physical therapists to compare the physiological workload within three groups of varying work experience and their comparative physiological responses during a 15-min recovery period. METHODS: Thirty therapists participated in the present study. They were divided into three groups with varying levels of work experience based on the number of years they had been in active employment: 1) Early Career (EC) group = 2-6 years); 2) Mid-Career (MC) group = 7-11 years), and 3) Late career (LC) group = over 11 years). Each group included 10 subjects comprised of both males and females. To conduct the measurements, each therapist treated one hemiplegic patient for 20 min using a passive range of motion protocol and then rested for 15 min. The maximum voluntary contraction on trapezius and deltoid muscles were tested using electromyography before and after treatment. During treatment, the muscle workload, muscle fatigue, and cardiovascular load were measured. The perceived workload was assessed using a subjective workload index (SWI) questionnaire following treatment. RESULTS: The three work experience groups of physical therapists performed a similar workload. The SWI corresponded well with physiological measurement. The muscle capacity after treatment of the EC group was significantly lower than that of the MC group (p < 0.05). Notably, the right deltoid of the LC group was significantly lower than that of the MC group. CONCLUSIONS: The physical therapists worked with a moderate, objectified workload. A 15-min rest period brought the cardiovascular load below 30% and lowered fatigue in the right deltoids. This result may indicate a musculoskeletal disorder warning signal for the physical therapists.

Multimodal stimuli modulate rapid visual responses during reaching.

The reticulospinal tract plays an important role in primate upper limb function, but methods for assessing its activity are limited. One promising approach is to measure rapid visual responses (RVRs) in arm muscle activity during a visually cued reaching task; these may arise from a tecto-reticulospinal pathway. We investigated whether changes in reticulospinal excitability can be assessed noninvasively using RVRs, by pairing the visual stimuli of the reaching task with electrical stimulation of the median nerve, galvanic vestibular stimulation, or loud sounds, all of which are known to activate the reticular formation. Surface electromyogram (EMG) recordings were made from the right deltoid of healthy human subjects as they performed fast reaching movements toward visual targets. Stimuli were delivered up to 200 ms before target appearance, and RVR was quantified as the EMG amplitude in a window 75-125 ms after visual target onset. Median nerve, vestibular, and auditory stimuli all consistently facilitated the RVRs, as well as reducing the latency of responses. We propose that this facilitation reflects modulation of tecto-reticulospinal excitability, which is consistent with the idea that the amplitude of RVRs can be used to assess changes in brain stem excitability noninvasively in humans.NEW & NOTEWORTHY Short-latency responses in arm muscles evoked during a visually driven reaching task have previously been proposed to be tecto-reticulospinal in origin. We demonstrate that these responses can be facilitated by pairing the appearance of a visual target with stimuli that activate the reticular formation: median nerve, vestibular, and auditory stimuli. We propose that this reflects noninvasive measurement and modulation of reticulospinal excitability.

Corticomotor excitability of arm muscles modulates according to static position and orientation of the upper limb.

OBJECTIVE: We investigated how multi-joint changes in static upper limb posture impact the corticomotor excitability of the posterior deltoid (PD) and biceps brachii (BIC), and evaluated whether postural variations in excitability related directly to changes in target muscle length. METHODS: The amplitude of individual motor evoked potentials (MEPs) was evaluated in each of thirteen different static postures. Four functional postures were investigated that varied in shoulder and elbow angle, while the forearm was positioned in each of three orientations. Posture-related changes in muscle lengths were assessed using a biomechanical arm model. Additionally, M-waves were evoked in the BIC in each of three forearm orientations to assess the impact of posture on recorded signal characteristics. RESULTS: BIC-MEP amplitudes were altered by shoulder and elbow posture, and demonstrated robust changes according to forearm orientation. Observed changes in BIC-MEP amplitudes exceeded those of the M-waves. PD-MEP amplitudes changed predominantly with shoulder posture, but were not completely independent of influence from forearm orientation. CONCLUSIONS: Results provide evidence that overall corticomotor excitability can be modulated according to multi-joint upper limb posture. SIGNIFICANCE: The ability to alter motor pathway excitability using static limb posture suggests the importance of posture selection during rehabilitation aimed at retraining individual muscle recruitment and/or overall coordination patterns.

The impact of load and base of support on electromyographic onset in the shoulder muscle during push-up exercises.

OBJECTIVE: To investigate the effects of base of support (BOS) and external loads on electromyographic (EMG) onset in the shoulder muscles during push-up exercises. METHODS: Two levels of external load were applied at two levels of BOS stability during push-up exercises. EMG onset in six shoulder muscles was measured in 30 healthy participants. RESULTS: With load set at 4% of body weight (BW), EMG onset in the lower trapezius (LT) (P = 0.003) and biceps brachia (BB) (P = 0.001) was significantly decreased with no load. Conversely, in other muscles (the upper trapezius (UT), teres major (TM), seratus anterior (SA) and deltoid posterior (DP)), time to EMG onset did not change significantly. No significant changes in EMG onset were observed with load at 2% of BW. The average time to EMG onset was significantly decreased for different stages of BOS instability in the LT (P = 0.04) and UT (P = 0.001). CONCLUSION: Both load and BOS instability reduce time to EMG onset, but BOS instability produces greater reductions.

Sex differences in electromechanical delay during a punch movement.

This study assessed how sex of participant is related to electromechanical delay during a karate punch. Ten male (M age = 25.00 yr., SD = 3.02; M height=174.9 cm, SD=6.3; M weight = 71.13 kg, SD=9.35) and 8 female (M age = 27.4 yr., SD = 6.0; M height = 161.4 cm, SD = 5.1; M weight = 59.09 kg, SD = 7.00) karate athletes performed 10 ballistic punches to a target as hard as possible. Kinematic analysis and surface electromyographic (EMG) activity of the upper-limb muscles were recorded. Men had a significantly shorter electromechanical delay in the anterior portion of the deltoid, showing a larger effectiveness in the transfer of the contractile force for the beginning of movement. Agonist and antagonist relationships show intermuscular coordination differences between the sexes. Results revealed the existence of a different neuromuscular coordination pattern of motor control between men and women, although a similar kinematic pattern was expected due to karate practice.