Review articles : Minimizing fatigue for functional electrical stimulation of muscle

Interest in the possibility of using electrically stimulated muscular contractions in rehabilitation medicine is increasing. Progress is impeded by the phenomenon of fatigue which impairs effectiveness and consistency of contractions. Various methods for minimizing fatigue have been proposed and are presently discussed. These include fibre type conversion as a result of chronic low frequency conditioning stimulation, sequential stimulation, optimization of stimulation parameters and the use of hybrid orthoses.

A comparison of uniform patterned and eutrophic electrotherapies in a clinical procedure of rehabilitation of some movements in the arthritic hand

The relative effectiveness of two different electrotherapies for hand rehabilitation was measured in 18 patients with muscle atrophy associated with rheumatoid arthritis, three of whom acted as controls and receiving no electrotherapy during the course of the trial. Both forms of electrotherapy were applied for between one and three hours each day for ten weeks. In the first electrotherapy, the stimuli were presented in a uniform pattern at a frequency of 10 stimuli/second (10 Hz). The electrotherapy for comparison (eutrophic electrotherapy) reproduced as stimuli the natural action potential firing pattern of a fatigue resistant motor unit in the first dorsal interosseus (1 st DI) of a normal hand.

Comparison was based on the relative improvement during and following 10 weeks of electrotherapy, with the two patterns of electrotherapy in seven different parameters of hand function: angular deviation at 1 st MCP joint in ulnar drift; hand grip strength; pulp-to-pulp pinch strength; key pinch strength; button-unbutton test; the maximal voluntary force 1 st DI could produce when acting isometrically; and in abduction, the endurance shown by 1 st DI in generating such force.

In all the parameters measured, eutrophic elecrotherapy was seen to be significantly more effective than a uniform patterned electrotherapy of 10 Hz. The greatest comparative effect of eutrophic electrotherapy was seen on endurance in force generation by 1 st DI and on hand grip strength, and the least on the reduction of the angular deviation of ulnar drift.

Electrotherapeutic rehabilitation of the quadriceps in elderly osteoarthritic patients: a double blind assessment of patterned neuromuscular stimulation

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.

A preliminary report on the effectiveness of trunk targeting in achieving independent sitting balance in children with cerebral palsy

OBJECTIVE

To assess the potential of Targeted Training in initiating or accelerating improved movement control of the trunk and hip joints in children with cerebral palsy so that independent sitting balance without specialized seating could be achieved.

DESIGN

Six single case studies.

SETTING

Assessment and review were undertaken in a specialized centre with intervention in the subjects' home or school.

SUBJECTS

Children between the ages of two years five months and seven years five months (mean four years seven months) with an established diagnosis of cerebral palsy. None had independent sitting balance at the start of the study.

INTERVENTION

Targeted Training using specialized equipment was directed at the appropriate few joints of the trunk as determined by initial testing and progressed when control at those joints had become automatic. The equipment provided support and challenged control learning. Periods of no intervention and placebo intervention, when the equipment was inappropriately set up, were also used. Two of the children ceased their traditional physiotherapy input while Targeted Training or placebo training took place.

MAIN OUTCOME MEASURE

A new test was devised and validated to determine the most caudal extent of control of the vertical posture. In addition, a functional test of independent sitting balance was defined.

RESULTS

All six children showed an increase in movement control and all gained independent sitting balance within 12-25 weeks (mean 16 weeks). This was irrespective of the continuation or cessation of traditional physiotherapy.

CONCLUSION

These preliminary findings suggest that Targeted Training may be an effective means of promoting movement control and functional ability. Confirmation of these findings by other investigators would be of value.

The use of patterned neuromuscular stimulation to improve hand function following surgery for ulnar neuropathy

A 60-year-old man with wasting and weakness of the right hand following ulnar nerve entrapment at the elbow was referred for electrotherapy. An ulnar nerve transposition had been performed 2 years previously. This had produced some improvement in nerve conduction without significantly improving hand muscle function. The right first dorsal interosseous muscle (FDI) was stimulated for 4 hours per day over a 6-week period with a stimulus pattern replicating the discharge of a single motor unit from a healthy, fatigued FDI (patterned neuromuscular stimulation or PNMS). The response was assessed using a single case design. Significant improvements in the strength and fatigue resistance of the FDI were observed, associated with improvements in general hand function. PNMS may be useful in restoring hand function in patients with muscle atrophy following entrapment neuropathy.