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PubMed1990

The distribution of muscle weakness in upper motoneuron lesions affecting the lower limb.

To determine the distribution of weakness in the lower limb after upper motoneuron lesions the strength of 8 muscle groups was measured. Four groups of patients were studied: 22 control subjects, 16 patients with unilateral leg paresis, 4 patients with severe unilateral paralysis and 5 patients with paraparesis. In the testing posture (seated), patients with cerebral upper motoneuron lesions showed no selective loss of power in flexors or extensors on the contralateral side. Gravitational torques were included in the measurements. However, proximal muscles (acting at hip and knee) were significantly less severely affected than more distal muscles (acting at ankle and hallux). At any particular joint, physiological flexors and extensors were affected equally in both the hemiparetic and paraparetic subjects. As in the upper limb (Colebatch and Gandevia, 1989), the strength of muscles on the clinically unaffected side was reduced compared with control subjects, although no muscle groups were especially affected.

Adolescent↗
PubMed1993

Effect of ephedrine on muscle weakness in a model of myasthenia gravis in rats.

In addition to therapy with anticholinesterases, ephedrine is sometimes used to improve muscle strength in myasthenia gravis, with variable results. The efficacy of ephedrine was tested in rats with a alpha-bungarotoxin-induced model of myasthenia gravis. The rats showed a drooping lower lip and impaired capability of drinking. Injections of neostigmine caused an improvement of the position of the lip. Ephedrine caused some improvement. However, ephedrine had no effect, either on the lower lip or on water consumption, when the sleep-wake cycle was reversed and the rats had their active period during day time. It was concluded that the effect of ephedrine was unspecific and probably due to arousal from drowsiness. The results suggest, therefore, that the variability of the effect of ephedrine in myasthenic patients is unrelated to neuromuscular transmission per se but rather due to a difference in susceptibility to arousal.

Animals↗
PubMed1993

Muscle weakness in women occurs at an earlier age than in men, but strength is preserved by hormone replacement therapy.

1. The time-course of the age-related decline in specific muscle force (maximum voluntary force per cross-sectional area) in men and women was determined by measuring the maximum voluntary force and cross-sectional area of the adductor pollicis muscle in 273 subjects aged 17-90 years (176 men, 30 premenopausal women and 67 peri- or post-menopausal women who were not receiving hormone replacement therapy). 2. To determine whether the loss of specific muscle force is hormone-dependent in women, we studied a further 25 women, aged 42-72 years, who were receiving hormone replacement therapy. 3. There was no significant difference in specific force between young men and pre-menopausal women. Around the time of the menopause there was a dramatic decline in specific force in women which was prevented by the use of hormone replacement therapy. In men the weakness started later (around the age of 60 years) and the decline in specific force was more gradual, reaching the level seen in post-menopausal women after the age of 75 years. 4. The protective effect of hormone replacement therapy on muscle strength is likely to be an important contributory factor to its proven action in preventing osteoporotic fractures. The dramatic peri-menopausal decline in muscle strength is a likely explanation for the known increases in falls and Colles' fractures around the time of the menopause.

Adolescent↗
PubMed1993

Measuring abdominal muscle weakness in patients with low back pain and matched controls: a comparison of 3 devices.

OBJECTIVE: To compare 3 hand held devices used to measure isometric abdominal muscle strength: the adapted sphygmomanometer, the vigorometer and the Penny & Giles myometer. METHODS: Subjects were men, aged 22 to 43 years. Fifteen had a history of low back pain and 18 age matched controls had no low back pain. The test position was a half sit-up at 45 degrees, knees at 90 degrees, feet secured. The single observer applied pressure with one of the devices downwards, just below the sternal notch, while the patient maintained that position. Order of methods was random, controlled by a series of 3 x 3 Latin squares. The vigorometer and myometer were calibrated to mm Hg. Even numbered subjects were tested twice; odd numbered subjects had their measurements timed. RESULTS: One subject was unable to complete the study. Subjects with low back pain had abdominal muscle strength 38.8 mmHg lower than healthy controls [F(1,62) = 72.84, P2 < 0.01]. Order of measurements was similar [F(2,62) = 1.19, P2 = 0.31]; instruments differed [F(2,62) = 27.94, P2 < 0.01]. Duplicate readings were similar (minimum P2 > 0.10); all 3 devices detected significant differences between the 2 groups (P2 < 0.01); mean measurement time was 19 s and time to measure with each device was similar (P2 = 0.70). CONCLUSION: All 3 instruments performed equally well. Since the sphygomanometer is available at about 1/5 the cost of the vigorometer and 1/12 the cost of the myometer, it is the preferred instrument.

Abdominal Muscles↗