Muscle activation in the contralateral passive shoulder during isometric shoulder abduction in patients with unilateral shoulder pain

Comparison of abdominal muscle activity during abdominal drawing-in maneuver combined with irradiation variations

Many experts have used an indirect method for enhancing strength and performance of muscles in clinical practice. The indirect method, which called an irradiation is a basic procedure of proprioceptive neuromuscular facilitation, there is little research related the effects of irradiation. This study investigated abdominal muscle activity during abdominal drawing-in maneuver (ADIM) combined with irradiation variations. The study recruited 42 healthy, young adults who were divided randomly into three groups according to which intervention they received. The first group performed the ADIM combined with coactivation of the pelvic floor muscle. The second group performed the ADIM combined with the irradiation resulting from dorsiflexion of the ankle. The third group performed the ADIM combined with the irradiation resulting from bilateral arm extension. Electromyography data were collected from the rectus abdominis, external oblique abdominis, and transversus abdominis/internal oblique abdominis (TrA/IO) muscles during ADIM combined with irradiation variations. There were significant differences in the abdominal muscle activity and the preferential contraction ratio of the TrA/IO among the three groups (P<0.05). ADIM combined with irradiation resulting from bilateral arm extension may be effective for enhancing the deep and superficial abdominal muscles of healthy people and athletes. The ADIM without the irradiation is advantageous for recovering motor control of the TrA/IO.

Upper limb physical function and adverse effects after breast cancer surgery: a prospective 2.5-year follow-up study and preoperative measures

OBJECTIVE

To examine upper limb physical function and adverse effects after axillary lymph node dissection (ALND) and sentinel lymph node biopsy (SLNB) in patients with breast cancer to identify impairments that can inform rehabilitation strategies.

DESIGN

Prospective longitudinal cohort. Upper limb measurements were studied preoperatively and 2.5 years after breast cancer treatment.

SETTING

Hospital setting.

PARTICIPANTS

Two groups of patients with early-stage primary breast cancer (N=391): the ALND surgery group (mean age, 55±10y) and the SLNB group (mean age, 57±10y).

INTERVENTIONS

Not applicable.

MAIN OUTCOME MEASURES

Arm lymphedema (≥10% increased arm volume relative to control arm volume), grip strength (in kilograms), shoulder mobility, pain intensity during isometric shoulder abduction (on a 100-mm visual analog scale), and body mass index (kg/m(2)). Parametric/nonparametric tests were used for hypothesized changes and differences, and regression analysis was used for confounding factors.

RESULTS

We observed more adverse effects in women treated with ALND than with SLNB after 2.5 years (P<.05): arm lymphedema (17% vs 3%), grip strength reduction (12% vs 2%), and shoulder abduction-provoked pain (increase of 6% vs decrease of 50%). The adverse effects were similar for affected and control upper limbs for all outcomes except arm lymphedema, which occurred only on the affected side.

CONCLUSIONS

Adverse effects in both affected and control/unaffected upper limb were observed after 2.5-year follow-up in both ALND and SLNB groups, but a higher prevalence was observed in the ALND group. Thus, women going through ALND surgery may benefit from further postoperative physical therapy, including resistance and strength exercise, focusing on pain management.

Muscle activity and head kinematics in unconstrained movements in subjects with chronic neck pain; cervical motor dysfunction or low exertion motor output?

Background

Chronic neck pain after whiplash associated disorders (WAD) may lead to reduced displacement and peak velocity of neck movements. Dynamic neck movements in people with chronic WAD are also reported to display altered movement patterns such as increased irregularity, which is suggested to signify impaired motor control. As movement irregularity is strongly related to the velocity and displacement of movement, we wanted to examine whether the increased irregularity in chronic WAD could be accounted for by these factors.

Methods

Head movements were completed in four directions in the sagittal plane at three speeds; slow (S), preferred (P) and maximum (M) in 15 men and women with chronic WAD and 15 healthy, sex and age-matched control participants. Head kinematics and measures of movement smoothness and symmetry were calculated from position data. Surface electromyography (EMG) was recorded bilaterally from the sternocleidomastoid and splenius muscles and the root mean square (rms) EMG amplitude for the accelerative and decelerative phases of movement were analyzed.

Results

The groups differed significantly with regard to movement velocity, acceleration, displacement, smoothness and rmsEMG amplitude in agonist and antagonist muscles for a series of comparisons across the test conditions (range 17 – 121%, all p-values < 0.05). The group differences in peak movement velocity and acceleration persisted after controlling for movement displacement. Controlling for differences between the groups in displacement and velocity abolished the difference in measures of movement smoothness and rmsEMG amplitude.

Conclusions

Simple, unconstrained head movements in participants with chronic WAD are accomplished with reduced velocity and displacement, but with normal muscle activation levels and movement patterns for a given velocity and displacement. We suggest that while reductions in movement velocity and displacement are robust changes and may be of clinical importance in chronic WAD, movement smoothness of unconstrained head movements is not.

"V"ictory transosseous equivalent suture configuration for arthroscopic rotator cuff tear repairs of iatrogenically completed PASTA lesions and full-thickness "U"-shaped tears

The cost of numerous anchors in rotator cuff surgery is high from both an economic standpoint as well as a physiologic one. More anchors means increased cost and increased surgical time; additionally, the greater number of anchors placed, the greater the expense on the native bone that they inevitably replace. It is therefore in the surgeon's and patient's best interest to use the appropriate number of anchors, no more and no less, with the appropriate number being that which allows for strong, stable fixation with minimal gap formation and maximal healing potential and recovery. The transosseous equivalent repair technique described herein uses a single double-loaded bioabsorbable suture anchor placed along the medial border of the rotator cuff foot print and the humeral head articular cartilage margin followed by 1 pushlock (Arthrex, Naples, Florida) anchor placed laterally on the vertical aspect of the greater tuberosity. It is designed for small to medium "U"-shaped tears and for iatrogenically completed partial articular supraspinatus tendon avulsions of moderate to large size, the so-called PASTA lesion. The use of selective knot placement allows for the conversion of a linear construct into a "V" configuration, optimizing repair strength and allowing for earlier rehabilitation while maximizing the healing biology seen with increased footprint contact dimensions and less repair gap formation.

Upper trapezius muscle activation patterns in neck–shoulder pain patients and healthy controls

This study aimed at investigating whether patients with neck-shoulder complaints from different aetiologies (work-related musculo-skeletal disorders, WMSD; whiplash associated disorders, WAD) show comparable muscle activation patterns, characterised by higher activation and lower relaxation levels of the trapezius muscles compared to healthy controls. Twenty healthy controls, 21 WMSD and 20 WAD patients with non-acute neck-shoulder pain were recruited for this cross-sectional study. Surface electromyography (sEMG) recordings were performed at the upper trapezius muscles during reference contractions, standardised computer tasks (typing and unilateral stress task), and rest measurements. sEMG was continuously recorded during these measurements. Outcome measures were root mean square (RMS) to study muscle activity, and relative rest time (RRT) to study muscle relaxation. Statistical analysis comprised the bootstrap technique and Kruskall-Wallis tests. Results showed no clear evidence for abnormal muscle activation patterns in WMSD and WAD patients compared to healthy controls. However, a tendency was observed for higher RMS levels during the reference contractions and computer tasks in both patient groups compared to healthy controls, and lower RRT levels at the non-dominant side during stress. Both patient groups also showed larger variability in RMS and RRT values. This variability has more often been reported in literature and may suggest the existence of subgroups of pain patients with corresponding different muscle activation patterns not related to aetiology. Future research may focus on identifying these subgroups of patients with neck-shoulder pain.

Trapezius muscle motor unit activity in symptomatic participants during finger tapping using properly and improperly adjusted desks

Work-related musculoskeletal disorders in the neck-shoulder area and upper extremities are common among computer users, especially women. We compared temporal changes of motor unit (MU) activation in the trapezius muscle during finger tapping using both appropriate and inappropriate ergonomic desk adjustments. Sixteen intensive and nonintensive computer users with either moderate or severe musculoskeletal disorders participated in the study. Six-channel intramuscular electromyographic (EMG) signals and 2-channel surface EMG were recorded from 2 positions of the trapezius muscle. A statistically significant increase in activity was observed with a desk adjusted 5 cm higher than appropriate and was attributable mainly to increased duration of MU activity. Participants with severe symptoms activated more MUs, and these were also active longer. In women, on average, MUs were active nearly twice as long as in men during the same tapping task. This study demonstrates that it is possible to evaluate ergonomic topics on the MU level and that incorrectly adjusted office equipment, in addition to motor demands imposed by the work task, results in prolonged activity of MUs. A potential application of this research is an increased awareness that certain individuals who work with incorrectly adjusted office equipment may be at greater risk of developing work-related musculoskeletal disorders.

Regional musculoskeletal conditions: shoulder pain

About half the population has at least one episode of shoulder pain yearly. History and clinical examination are cornerstones in the evaluation of the patient. Shoulder pain at the work place is associated with job strain: lack of control and work with elevated arms and hand tools. Clinical skills and knowledge about red and yellow flags and biomechanics are essential to perform a systematic and reliable evaluation. The diagnostic validity of clinical tests for rotator cuff tear, impingement syndrome and superior labral tears is equal or better than ultrasound and magnetic resonance imaging. Non-steroidal anti-inflammatory drugs and cortico-steroidal injections have documented short-term pain relief. Additionally, the physician should attempt to give the patient simple advice and reinforce active coping strategies. One randomized study suggests that a proper physiotherapy regimen and surgery are equally effective for the impingement syndrome. Further research should address the cost-effectiveness of diagnostic methods and treatments.

Influence of memory demand and contra lateral activity on muscle activity

Computer mouse work often includes memory demands and contra lateral activity. This study simulated video display unit (VDU) mouse-work and the focus was on forearm muscle activity as a result of standardised postural loads, memory demands and contra lateral activity. Surface and intramuscular electromyography (EMG) were recorded from the right forearm muscles during finger elevation and rest with and without memory demands and with and without contra lateral activity i.e. activity of the left hand. In most situations, memory demand increased activity in the m. extensor carpi radialis brevis and m. flexor digitalis superficialis. Also contra lateral activity increased activity in situations with and without memory demands. While surface EMG level of the m. extensor digitorum communis did not increase during memory demands, intramuscular EMG level increased when memory demands and contra lateral activity was combined. Influence of memory demands and contra lateral activity were most pronounced, in situations where activity levels were small. We presume that it is not only prolonged time of active computer mouse use that is a risk for development of musculoskeletal disorders, but also the time when people interact with the computer mentally or with the 'non-mouse hand', while resting their 'mouse-hand' on the mouse.