Barbara M. Doucet

VARIABLE STIMULATION PATTERNS FOR POSTSTROKE HEMIPLEGIA

Neuromuscular electrical stimulation can improve motor function in those affected by paralysis, but its use is limited by a high rate of muscular fatigue. Variable stimulation patterns have been examined in young adults with and without spinal cord injury, but much less investigation has been devoted to studying the effects of variable stimulation patterns administered to older adults or those paralyzed by stroke. Significant changes occur in the neuromuscular system with age that may affect the response to variable stimulation patterns. We administered three, 3‐min intermittent stimulation patterns to the median nerves of 10 individuals with hemiplegia from stroke and 10 age‐matched able‐bodied adults: (1) constant 20 HZ, (2) a pattern that began at 20 HZ and progressively increased to 40 HZ in the latter half of the task, and (3) a 20‐HZ pattern that switched to a 20‐HZ doublet pattern after 90 s. In the able‐bodied group the doublet pattern produced significantly higher force time integrals (FTI) (1409.72 ± 3.15 N · s) than the 20–40‐HZ pattern (1067.46 ± 1.15 N · s) or the 20‐HZ pattern (831 ± 1.87 N · s). In the poststroke individuals the doublet pattern also produced the highest FTI (724.04 ± 2.02 N · s), and there was no significant difference between the 20–40‐HZ (636.42 ± 1.65 N · s) and 20‐HZ (583.64 ± 3.02 N · s) patterns. These results indicate that protocols that incorporate doublets in the later stages of fatigue are effective in older adults and in older adults with paralysis from stroke.

Quantifying Function: The Rest of the Measurement Story

Sharon A. Gutman, PhD, OTR, FAOTA, is Associate Professor, Columbia University, Programs in Occupational Therapy, New York. In this era of health care reform, funding caps, and restricted access to services, occupational therapy practitioners are challenged to validate their services and justify their place in the health care arena. The strength of our profession lies in our unique ability to thoroughly and comprehensively measure function—a person’s ability to perform a specific daily life activity such as transferring from a wheelchair to a toilet or maintaining a monthly budget that supports shared apartment living. The International Classification of Functioning, Disability and Health (World Health Organization, 2001) defines function in terms of body impairments, activity limitations, and participation restrictions. Although occupational therapy practitioners have always agreed that evaluating and treating function is the essential core of the profession, we have not consistently agreed on the definition of function or the best methods to measure it.

High- Versus Low-Frequency Stimulation Effects on Fine Motor Control in Chronic Hemiplegia: A Pilot Study

Abstract Background: The optimal parameters of neuromuscular electrical stimulation (NMES) for recovery of hand function after stroke are not known. This clinical pilot study examined whether higher or lower frequencies are more effective for improving fine motor control of the hand in a chronic poststroke population. Methods: A 1-month, 4 times per week, in-home regimen of either a high-frequency (40 Hz) or low-frequency (20 Hz) NMES program was applied to the hemiplegic thenar muscles of 16 persons with chronic stroke. Participants were identified a priori as having a low level of function (LF) or a high level of function (HF). Outcome measures of strength, dexterity, and endurance were measured before and after participation in the regimen. Results: LF subjects showed no significant changes with either the high- or the low-frequency NMES regimen. HF subjects showed significant changes in strength, dexterity, and endurance. Within this group, higher frequencies of stimulation yielded strength gains and increased motor activation; lower frequencies affected dexterity and endurance. Conclusions: The results suggest that higher frequencies of stimulation could be more effective in improving strength and motor activation properties and that lower frequencies may affect coordination and endurance changes. Results also indicate that persons with a higher functional level of recovery may respond more favorably to NMES regimens, but further study with larger patient groups is warranted.

Neurorehabilitation: Are We Doing All That We Can?

Occupational therapists have many intervention tools available for working with clients having a neurological injury; however, some of the most innovative and effective methods have not gained acceptance by many clinicians. Emerging research and new technologies provide occupational therapists with a multitude of treatment strategies and novel devices, but incorporation of those tools into clinical practice appears to be limited by the time necessary to learn about the intervention, educational requirements associated with implementation, or lack of awareness regarding the evidence supporting the use of such tools. Strategies to combat this trend include educating clinicians on evidence-based methods for neurological rehabilitation, aligning academics with practitioners to translate evidence into practical treatment strategies, and accepting that occupational therapy can use these innovations as a means toward state-of-the art, occupation-based practice.

Variable stimulation patterns in younger and older thenar muscle

Neuromuscular electrical stimulation (NMES) is typically used with older adults receiving rehabilitation therapies, but little is known about the stimulation patterns that maximize force output and minimize fatigue in this population. The purpose of this study was to apply variable patterns of stimulation to the thenar muscles of the hand in younger and older adults to determine if force production and neuromuscular fatigue effects were similar. Three submaximal stimulation patterns were administered: A 20Hz constant frequency pattern, a pattern that increased from 20 to 40Hz, and a pattern that incorporated two closely spaced (5ms) doublet pulses. The doublet stimulation produced significantly higher average forces and force-time integrals (FTIs) than the constant frequency and increasing frequency patterns in both age groups. Additionally, older adults showed less fatigue than the younger group during isometric contractions performed after the fatiguing stimulation patterns. These results suggest that variable pulse NMES patterns enhance force production in the hand in both younger and older individuals better than constant frequency patterns, which are typically used in clinical applications. Also, greater fatigue resistance to electrical stimulation protocols may exist in the older population; this is critical information for the design and application of NMES rehabilitation regimens used with older adults.

Force irregularity following maximal effort: the after-peak reduction

Irregularities in force output are present throughout human movement and can impair task performance. We investigated the presence of a large force discontinuity (after-peak reduction, APR) that appeared immediately following peak in maximal effort ramp contractions performed with the thumb adductor and ankle dorsiflexor muscles in 25 young adult participants (76% males, 24% females; M age 24.4 years, SD = 7.1). The after-peak reduction displayed similar parameters in both muscle groups with comparable drops in force during the after-peak reduction minima (thumb adductor: 27.5 ± 7.5% maximal voluntary contraction; ankle dorsiflexor: 25.8 ± 6.2% maximal voluntary contraction). A trend for the presence of fewer after-peak reductions with successive ramp trials was observed, suggesting a learning effect. Further investigation should explore underlying neural mechanisms contributing to the after-peak reduction.