Abstract
Recent studies, in combination with advances in modern electronics, suggest a role for electrotherapy in reversing muscle wasting. However, its effects on human subjects are not always clear-cut. The authors propose that conventional uniform frequency stimulation may deprive the muscle of adaptive information normally encoded in the nonuniform discharge of its motoneuron. This hypothesis was tested in a double blind control trial by stimulating the quadriceps femoris (QF) of elderly subjects with osteoarthritis of the knee. A stimulation pattern replicating that occurring in a normal, fatigued QF motor unit (patterned neuromuscular stimulation) was compared with uniform stimulation of the same mean frequency and random pattern stimulation (created by shuffling the order of the interpulse intervals in the replicated stimulus train). A'sham' stimulation protocol provided an effective placebo. Subjects were assessed at the level of impairment (muscle strength, endurance and cross-sectional area), disability (timed 10-metre walk, timed sit-to-stand) and handicap (part II of the Nottingham Health Profile).
Following stimulation, some descriptive improvements in outcome measures were observed in favour of PNMS, particularly in functional tests such as walking speed and sit-to-stand time. No stimulation pattern emerged as being significantly better than another, although statistically significant (p ≤ 0.05) differences between individual stimulation patterns were observed at a number of assessment weeks.
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