Torque-EMG-velocity relationship in female workers with chronic neck muscle pain

The present study investigated the effect of chronic neck muscle pain (defined as trapezius myalgia) on neck/shoulder muscle function during concentric, eccentric and static contraction. Forty-two female office workers with trapezius myalgia (MYA) and 20 healthy matched controls (CON) participated. Isokinetic (-60, 60 and 180 degrees s(-1)) and static maximal voluntary shoulder abductions were performed in a Biodex dynamometer, and electromyography (EMG) obtained in the trapezius and deltoideus muscles. Muscle thickness in the trapezius was measured with ultrasound. Pain and perceived exertion were registered before and after the dynamometer test. The main findings were that shoulder abduction torque (at -60 and 60 degrees s(-1)) and trapezius EMG amplitude (at -60, 0 and 60 degrees s(-1)) were significantly lower in MYA compared with CON (p<0.001-0.05). Deltoideus EMG and trapezius muscle thickness were not significantly different between the groups. While perceived exertion increased in both groups in response to the test (p<0.0001), pain increased in MYA only (p<0.0001). In conclusion, having trapezius myalgia was associated with decreased strength capacity and lowered activity of the painful trapezius muscle. The most consistent differences-in terms of both torque and EMG-were found during slow concentric and eccentric contractions. Activity of the synergistic pain free deltoideus muscle was not significantly lower, indicating specific inhibitory feedback of the painful trapezius muscle only. Parallel increase in pain and perceived exertion among MYA were observed in response to the maximal contractions, emphasizing that heavy physical exertion provokes pain increase only in conditions of myalgia.     

Establishment of a recording method for surface electromyography in the iliopsoas muscle

We examined the availability and reliability of surface electromyography (EMG) signals from the iliopsoas muscle (IL). Using serial magnetic resonance images from fifty healthy young males, we evaluated whether the superficial region of IL was adequate for attaching surface EMG electrodes. Subsequently, we assessed EMG cross-talk from the sartorius muscle (SA)—the nearest to IL—using a selective cooling method in fourteen subjects. The skin above SA was cooled, and the median frequencies of EMG signals from IL and SA were determined. The maximum voluntary contraction during isometric hip flexion was measured before and after selective cooling, and surface EMG signals from SA and IL were measured. The superficial area of IL was adequately large (13.2 ± 2.7 cm²) for recording surface EMG in all fifty subjects. The maximum perimeter for the medial–lateral skin facing IL was noted at a level 3–5 cm distal to the anterior superior iliac spine. Following cooling, the median frequency for SA decreased significantly (from 70.1 to 51.9 Hz, p < 0.001); however, that for IL did not alter significantly. These results demonstrated that EMG cross-talk from SA was negligible for surface EMG signals from IL during hip flexion.     

17beta-estradiol signaling in skeletal muscle cells and its relationship to apoptosis

17beta-estradiol exerts an antiapoptotic action in skeletal muscle cells through extranuclear ERalpha and beta. This protective action, mainly involves a non-genomic mechanism of ERK1/2 and PI3K/Akt activation and BAD phosphorylation. ERbeta plays a major role in the inhibition of apoptosis by 17beta-estradiol at the level of mitochondria, whereas ERalpha and ERbeta mediate the activation of Akt to the same extent, suggesting differential involvement of ER isoforms depending on the step of the apoptotic/survival pathway involved. The myopathies associated to estrogen deficit states may be related to the mechanisms by which estrogen regulates apoptosis.     

Fracture of neck of the femur: changing incidence.

From 1959 to 1977 the numbers of hospital admissions for fracture of the neck of the femur increased by a factor of 2.7. Detailed analysis of data from the Hospital In-Patient Enquiry for 1968-77 showed that the increase applied to both sexes and at all ages over 45. The true incidence rate increased in parallel with the admission rate, and only a small part of the increased number of admissions was explained by the increasing numbers of the elderly. The increasing incidence of fracture of the neck of the femur imposes great strain on hospital resources, particularly trauma and orthopaedic departments, and merits urgent investigation. An explanation for the increase might be that the experience of one demand-led condition characterises a greater need for health care among the elderly for other conditions.     

Postural responses to vibrostimulation of the neck muscle proprioceptors in man

Postural responses to vibrostimulation (50–100 Hz, 0.5 mm, 4–8 sec) of muscles of the back surface of the neck were studied in healthy subjects. In the sitting position, vibrostimulation evoked local displacements (backward head deflection), but global postural responses (forward inclination of the whole body) developed in the standing position. The amplitude of the evoked body inclination was dependent upon the site of the vibrostimuli application along the vertebral column. Asymmetrical application of vibrostimuli to the muscles of the right or left neck side was accompanied by development of a lateral component in the postural response. Changes in the spatial orientation of the head led to the changes in postural response direction: head turning to the right resulted in right-side body deviation during vibration, and vice versa. Illusions of head bend caused by habituation to its static turning were accompanied by precisely the same changes in the direction of body deviation. It is assumed that neck-evoked motor events are mediated via central mechanisms that are involved in perception of the head and body position in space.Translated from Neirofiziologiya, Vol. 25, No. 2, pp. 101–108, March–April, 1993.     

Permeability of rat diaphragm muscle to some methyl glycosides and its relationship to monosaccharide transport

1. Studies in vitro have shown that rat diaphragm muscle is freely permeable to alpha- and beta-methyl d-xylosides and beta-methyl l-arabinoside but not to alpha- or beta-methyl d-glucoside or alpha-methyl d-mannoside. 2. No competition for entry between methyl pentosides and d-xylose, l-arabinose, d-glucose or 3-O-methyl-d-glucose could be demonstrated and alpha-methyl xyloside entry was not inhibited by phlorrhizin. 3. It is concluded that the monosaccharide transport system is unlikely to contribute significantly to the entry of the methyl pentosides in this tissue.     

Age-related changes of element contents in human tendon of the iliopsoas muscle and the relationships among elements

To elucidate compositional changes of the tendons with aging, the authors investigated age-related changes of element contents in the tendon of the iliopsoas muscle by inductively coupled plasma-atomic emission spectrometry. The subjects consisted of 14 men and 14 women, ranging in age from 4 to 102 yr. The insertion tendons of the iliopsoas were removed from the cadavers after ordinary dissection and also surgically from patients with congenital dislocation of the hip. It was found that both Mg and P in the tendon of the iliopsoas muscle increased significantly with aging, but the other elements, such as S, Ca, Na, Zn, Fe, and Si, hardly changed with aging. With regard to the relationship among element contents, extremely significant correlations were found between P and S contents, between Mg and Na contents, and between S and Zn contents. In addition, very significant correlations were found between Si and either S or Zn contents. However, there was no significant correlation between Ca and P contents. These results revealed that with regard to age-related changes of element contents and the relationships among element contents, the tendon of the iliopsoas muscle was different from the Achilles tendon, in which both Mg and P decreased significantly with aging and there were significant correlations each other among the contents of S, Mg, and P.