Muscle & nerve
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Multicenter Study Clinical Trial
Long-term intensive electrically stimulated cycling by spinal cord-injured people: effect on muscle properties and their relation to power output.
Inactivity and muscular adaptations following spinal cord injury (SCI) result in secondary complications such as cardiovascular disease, obesity, and pressure sores. Functional electrically stimulated (FES) cycling can potentially reduce these complications, but previous studies have provided inconsistent results. We studied the effect of intensive long-term FES cycle training on muscle properties in 11 SCI subjects (mean +/- SEM: 41.8 +/- 2.3 years) who had trained for up to 1 hour/day, 5 days/week, for 1 year. ⋯ Relative force response at 1 HZ decreased, relaxation rate remained unchanged, and fatigue resistance improved significantly. Power output (PO) improved to a lesser extent than quadriceps torque and not to a greater extent than has been reported previously. We need to understand the factors that limit PO in order to maximize the benefits of FES cycling.
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High-resolution ultrasound can demonstrate focal nerve enlargement in entrapment neuropathies. We hypothesized that a ratio between the nerve cross-sectional area at the site of maximal enlargement and at an unaffected site may improve diagnostic accuracy in ulnar neuropathy at the elbow (UNE), when compared to a single measurement at the site of maximal enlargement. ⋯ This represented a significant increase compared with the ratio of 1.1:1 for both comparisons in controls (P < 0.0001). This type of ratio may be particularly useful for assessing entrapment in those with polyneuropathy or obesity, both of which can cause diffuse nerve enlargement.
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The sternocleidomastoid muscle (SCM) is an accessory inspiratory muscle, but it is not investigated systematically in patients with amyotrophic lateral sclerosis (ALS). We aimed to study the involvement of the SCM and to evaluate the role of the diaphragm and SCM on respiratory tests performed in ALS patients. We studied 45 patients (mean age +/- SD: 60.6 +/- 13 years). ⋯ On multiple regression analysis both PImax and SNIP are dependent on SCM Ampl and Diaphr Ampl, but FVC is not. PImax and SNIP determination mostly depend on SCM and diaphragm function, but the FVC is also dependent on expiratory muscle function. We conclude that neck weakness is a clinical sign that indicates a poor prognosis, and the SCM CMAP can contribute to respiratory function evaluation in ALS patients.
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The time- and dose-dependent effects of acute high-dose corticosteroids on the diaphragm muscle are poorly defined. This study aimed to examine in rabbits the temporal relationships and dose-response effects of acute high-dose methylprednisolone succinate on diaphragmatic contractile and structural properties. Animals were assigned to groups receiving: (1) 80 mg/kg/day methylprednisolone (MP80) intramuscularly for 1, 2, and 3 days; (2) 10 mg/kg/day methylprednisolone (MP10, pulse-dose) for 3 days; or (3) saline (placebo) for 3 days; and (4) a control group. ⋯ Significant myofibrillar disarray was also observed in both MP groups. The decline in Po was significantly associated with the increased volume density of abnormal myofibrils. Thus, very high-dose methylprednisolone (MP80) can produce rapid reductions in diaphragmatic function, whereas pulse-dose methylprednisolone (MP10) produces only modest functional loss.
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We report on two children presenting at birth with respiratory failure, bilateral diaphragmatic eventration, and floppiness. Electrodiagnostic studies of the limbs, and biochemical and DNA studies excluded generalized neuromuscular diseases. ⋯ Diaphragm muscle biopsy showed a paucity of muscle fibers. Isolated hypoplasia of the diaphragm is a rare cause of neonatal respiratory failure, which may have a favorable outcome with long-term ventilatory support.