Phenotypical transitions and Ca2+ activation properties in human muscle fibers: effects of a 60-day bed rest and countermeasures.

Muscle biopsies were taken from soleus and vastus lateralis before and after a 60-day bed rest (BR) to examine expression changes in the regulatory proteins of the thin filament and in contractile function. Twenty-four women separated in three groups were submitted to BR or a combined protocol of resistance and aerobic exercises during BR or received a supplementation of amino acids during BR. Ca(2+)-tension relationships were established in single skinned fibers identified by their myosin heavy chain and troponin C isoform expressions. Expression patterns of regulatory proteins were analyzed on muscle pieces. For both muscles, BR produced similar decreases in slow and fast fiber diameters but larger decreases in P(0) maximal forces in slow than in fast fibers. Specific forces were decreased in slow soleus and vastus fibers, which displayed a reduction in Ca(2+) affinity. These changes were accompanied by slow-to-fast transitions in regulatory proteins, with troponins C and T appearing as sensitive markers of unloading. Exercises prevented the changes in fiber diameters and forces and counteracted most of the slow-to-fast transitions. The nutrition program had a morphological beneficial effect on slow fibers. However, these fibers still presented decreases in specific P(0) after BR. Phenotypical transitions due to BR were not prevented by amino acids. Finally, in vastus lateralis muscle, BR induced a decrease in O-glycosylation level that was prevented by exercise and attenuated by nutrition. In conclusion, this study has addressed for the first time in women the respective efficiencies of two countermeasures associated with BR on muscle properties and regulatory protein expression.

Pain and neuromuscular disease: the results of a survey.

OBJECTIVE: The objective of this study was to evaluate pain frequency, severity, location, treatment, and relief in a population of adult patients with neuromuscular disorders (NMD). DESIGN: The authors used a self-completion mail questionnaire from the Physical Medicine Clinic at the Lille University Medical Center (northern France). Two hundred eighty-one adults with a confirmed diagnosis of hereditary neuromuscular disease were mailed a questionnaire, which was returned by 125 subjects (response rate = 45%). The main outcome measures were mean motor deficiency scores (on the Brooke and Vignos scales), anxiety and depression scores, pain intensity (on a 0-10 numeric scale) and location, frequency of pain-aggravating situations, and pain treatment and relief. RESULTS: Seventy-three percent of respondents reported pain and 62% reported chronic pain (defined as pain for at least 3 mos). The mean pain intensity was 6.1/10 with 40% reporting severe pain (a score of > or = 7). Forty-six percent and 16% of subjects had a high risk for anxiety and depression, respectively. The most common pain-aggravating situations were "walking," "standing," and "muscle stretching." Walking was more frequently cited as a pain-aggravating situation by the chronic pain population than by the acute pain population. Seventy percent of patients with pain had received at least one analgesic drug. Massage was the most frequently prescribed physical treatment. CONCLUSIONS: Pain is a frequent symptom in adult patients with NMD and needs to be better characterized in this population. The use of painkillers and physical pain treatments did not seem to provide adequate relief for the patients studied here.