Variable stimulation patterns for poststroke hemiplegia

Fatigability of the thenar muscles using electrical nerve stimulation with fixed stimuli count, while varying the frequency and duty cycle

Our aim was to compare three electrical stimulation protocols (P20, P30 and P40), with the same number of stimuli, but different stimulation frequencies (20, 30 and 40 Hz, respectively) and duty cycles [1.2:1.2 s (continuous), 0.8:1.2 s (intermittent) and 0.6:1.2 s (intermittent), respectively). Twitch force and the peak-to-peak M-wave amplitude of the thenar muscles were measured before, during and after each protocol at 1-40 Hz in random order. Twelve healthy adults (23-41 years old) were examined for each protocol in random order and in separate sessions. P20 elicited the highest mean force, and P40 the lowest decrease in percent force at the end of the protocol. Force evoked at 1 and 10 Hz decreased less after P40, compared with P20 and P30. The M-wave amplitude was significantly reduced throughout all protocols, with the largest decrease observed during P30. Although an increase in frequency typically induced earlier and greater decrement in force, this was compensated or even reversed by increasing the interval between each stimulation train, while keeping the number of pulses per stimulation cycle constant. The lesser decrease in M-wave amplitude during P40 compared with P20 indicates that longer between-train intervals may help maintaining the integrity of neuromuscular propagation.

A randomised clinical trial comparing 35 Hz versus 50 Hz frequency stimulation effects on hand motor recovery in older adults after stroke

More solid data are needed regarding the application of neuromuscular electrical stimulation (NMES) in the paretic hand following a stroke. A randomised clinical trial was conducted to compare the effects of two NMES protocols with different stimulation frequencies on upper limb motor impairment and function in older adults with spastic hemiparesis after stroke. Sixty nine outpatients were randomly assigned to the control group or the experimental groups (NMES with 50 Hz or 35 Hz). Outcome measures included motor impairment tests and functional assessment. They were collected at baseline, after 4 and 8 weeks of treatment, and after a follow-up period. NMES groups showed significant changes (p < 0.05) with different effect sizes in range of motion, grip and pinch strength, the Modified Ashworth Scale, and the muscle electrical activity in the extensors of the wrist. The 35 Hz NMES intervention showed a significant effect on Barthel Index. Additionally, there were no significant differences between the groups in the Box and Block Test. Both NMES protocols proved evidence of improvements in measurements related to hand motor recovery in older adults following a stroke, nevertheless, these findings showed that the specific stimulation frequency had different effects depending on the clinical measures under study.

Influence of Elbow Flexion and Stimulation Site on Neuromuscular Electrical Stimulation of the Biceps Brachii

Functional electrical stimulation (FES) can help individuals with physical disabilities by assisting limb movement; however, the change in muscle geometry associated with limb movement may affect the response to stimulation. The aim of this paper was to quantify the effects of elbow flexion and stimulation site on muscle torque production. Contraction torque about the elbow was measured in 12 healthy individuals using a custom elbow flexion testbed and a transcutaneous electrode array. Stimulation was delivered to six distinct sites along the biceps brachii over 11 elbow flexion angles. Flexion angle was found to significantly influence the optimal (i.e., torque-maximizing) stimulation site ( ), with post hoc analysis indicating a proximal shift in optimal stimulation site with increased flexion. Similarly, the biceps stimulation site was found to significantly influence the flexion angle at which peak torque occurred ( ), with post hoc analysis indicating an increase in peak-torque flexion angle as stimulation site is moved proximally up the biceps. Since maximizing muscle force per unit stimulation is a common goal in rehabilitative FES, future efforts could examine methods which compensate for the shift in optimal stimulation site during FES-induced limb movement.

Pilot Study Combining Electrical Stimulation and a Dynamic Hand Orthosis for Functional Recovery in Chronic Stroke

OBJECTIVE

We investigated the effect of a combined neuromuscular electrical stimulation (ES) and dynamic hand orthosis (DHO) regimen with a group of people with chronic stroke to improve performance on specific daily tasks.

METHOD

Four people with chronic stroke participated in an ES-DHO regimen using the affected upper extremity 5×/wk for 6 wk. Outcome measures included grip strength, range of motion (ROM), and analysis of muscle activation-deactivation during release of grasp through electromyography. Ability to perform specific daily living tasks was assessed using the Assessment of Motor and Process Skills (AMPS).

RESULTS

Results suggested that improvements in strength, ROM, and grasp deactivation are possible with the combined ES-DHO regimen. All participants' AMPS motor scores improved.

CONCLUSIONS

An ES-DHO regimen may improve motor skills needed for functional task performance in people with chronic stroke. Results should be interpreted cautiously because of the pilot nature of the study and the small sample size.

Neuromuscular Electrical Stimulation for Treatment of Muscle Impairment: Critical Review and Recommendations for Clinical Practice

Purpose: In response to requests from physiotherapists for guidance on optimal stimulation of muscle using neuromuscular electrical stimulation (NMES), a review, synthesis, and extraction of key data from the literature was undertaken by six Canadian physical therapy (PT) educators, clinicians, and researchers in the field of electrophysical agents. The objective was to identify commonly treated conditions for which there was a substantial body of literature from which to draw conclusions regarding the effectiveness of NMES. Included studies had to apply NMES with visible and tetanic muscle contractions. Method: Four electronic databases (CINAHL, Embase, PUBMED, and SCOPUS) were searched for relevant literature published between database inceptions until May 2015. Additional articles were identified from bibliographies of the systematic reviews and from personal collections. Results: The extracted data were synthesized using a consensus process among the authors to provide recommendations for optimal stimulation parameters and application techniques to address muscle impairments associated with the following conditions: stroke (upper or lower extremity; both acute and chronic), anterior cruciate ligament reconstruction, patellofemoral pain syndrome, knee osteoarthritis, and total knee arthroplasty as well as critical illness and advanced disease states. Summaries of key details from each study incorporated into the review were also developed. The final sections of the article outline the recommended terminology for describing practice using electrical currents and provide tips for safe and effective clinical practice using NMES. Conclusion: This article provides physiotherapists with a resource to enable evidence-informed, effective use of NMES for PT practice.

Correlation between upper limb function and oral health impact in stroke survivors

[Purpose] The aim of the present study was to evaluate the relationship between upper limb impairment and oral health impact in individuals with hemiparesis stemming from a stroke. [Subjects and Methods] The study subjects were conducted with a sample of 27 stroke survivors with complete or partial hemiparesis with brachial or crural predominance. The 14-item short version of the Oral Health Impact Profile was used to evaluate perceptions of oral health. The Brazilian version of the Stroke Specific Quality of Life Scale was used to evaluate perceptions regarding quality of life. [Results] A statistically significant association was found between the upper extremity function subscale of the SSQOL-Brazil and the impact of oral health evaluated using the OHIP-14, with a strong correlation found for the physical pain subscale, moderate correlations with the functional limitation, psychological discomfort, physical disability, social disability and social handicap subscales as well as a weak correlation with the psychological disability subscale. Analyzing the OHIP-14 scores with regard to the impact of oral health on quality of life, the most frequent classification was weak impact, with small rates of moderate and strong impact. [Conclusion] Compromised upper limb function and self-perceived poor oral health, whether due to cultural resignation or functional disability, exert a negative impact on the quality of life of individuals with hemiparesis stemming from a stroke.

Eight-point binding as a physical therapeutic resource for rehabilitation of functional performance after a stroke

A stroke may leave neurological, motor and sensory sequelae, interfering with the function of movements and culminating in gait and balance changes. Therefore, it is necessary to demonstrate the efficacy of eight-point binding, a low-cost technique that functions to provide proprioceptive information and promote the biomechanical alignment of the ankle, acting against mechanisms that lead to equinovarus foot. This study aims to determine the immediate effect of eight-point binding as a physical therapy resource for the rehabilitation of function performance after a stroke. To this end, 22 patients who were able to walk alone without an orthosis were evaluated, and performed the Timed Up and Go (TUG) functional mobility test, a gait speed assessment and the Berg Balance Scale, with and without the eight-point binding in the paretic lower limb. When comparing the results after the eight-point binding, it was possible to observe a statistically significant difference (p<0.05) in all of the studied variables. After analyzing the results, it was concluded that after a single application of eight-point binding, it is possible to identify statistically significant improvement in gait speed, functional mobility and balance after a stroke.

High-versus low-frequency stimulation effects on fine motor control in chronic hemiplegia: a pilot study

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.

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.

Novel patterns of functional electrical stimulation have an immediate effect on dorsiflexor muscle function during gait for people poststroke

BACKGROUND

Foot drop is a common gait impairment after stroke. Functional electrical stimulation (FES) of the ankle dorsiflexor muscles during the swing phase of gait can help correct foot drop. Compared with constant-frequency trains (CFTs), which typically are used during FES, novel stimulation patterns called variable-frequency trains (VFTs) have been shown to enhance isometric and nonisometric muscle performance. However, VFTs have never been used for FES during gait.

OBJECTIVE

The purpose of this study was to compare knee and ankle kinematics during the swing phase of gait when FES was delivered to the ankle dorsiflexor muscles using VFTs versus CFTs.

DESIGN

A repeated-measures design was used in this study.

PARTICIPANTS

Thirteen individuals with hemiparesis following stroke (9 men, 4 women; age=46-72 years) participated in the study.

METHODS

Participants completed 20- to 40-second bouts of walking at their self-selected walking speeds. Three walking conditions were compared: walking without FES, walking with dorsiflexor muscle FES using CFTs, and walking with dorsiflexor FES using VFTs.

RESULTS

Functional electrical stimulation using both CFTs and VFTs improved ankle dorsiflexion angles during the swing phase of gait compared with walking without FES (X+/-SE=-2.9 degrees +/- 1.2 degrees). Greater ankle dorsiflexion in the swing phase was generated during walking with FES using VFTs (X+/-SE=2.1 degrees +/- 1.5 degrees) versus CFTs (X+/-SE=0.3+/-1.3 degrees). Surprisingly, dorsiflexor FES resulted in reduced knee flexion during the swing phase and reduced ankle plantar flexion at toe-off.

CONCLUSIONS

The findings suggest that novel FES systems capable of delivering VFTs during gait can produce enhanced correction of foot drop compared with traditional FES systems that deliver CFTs. The results also suggest that the timing of delivery of FES during gait is critical and merits further investigation.

Avaliação do ácido lático em indivíduos com hemiparesia pós-acidente vascular encefálico após estimulação elétrica para fortalecimento muscular

O fortalecimento da musculatura parética promove melhora da capacidade funcional, o que pode ser obtido pela estimulação elétrica funcional (EEF), porém são necessários parâmetros específicos para evitar fadiga muscular. Este estudo visou verificar, em indivíduos com hemiparesia pós-AVE, o tempo de repouso (time off) necessário para reabsorção do ácido lático durante a EEF, de modo a evitar a fadiga - detectada por lactacidemia (concentração excessiva de ácido lático). Foram coletadas amostras de sangue de 18 indivíduos portadores de hemiparesia em sete momentos, antes, durante e após a EEF. A corrente quadrada bifásica, de 50 Hz, foi usada com time on de 10 segundos (s) e o time off variou de 10 s (protocolo 1) a 30 s (protocolo 2), sobre o ponto motor do músculo tibial anterior. Na análise do sangue coletado, não foi encontrada diferença estatisticamente significante (p>0,05) entre os dois protocolos; tampouco foi registrada diferença no período imediatamente pós-terapia. Pode-se pois afirmar que a ferramenta utilizada para mensurar lactacidemia não se mostrou eficaz na detecção da fadiga muscular, inviabilizando verificar o tempo ideal de repouso (time off), sendo necessários mais estudos em busca de protocolos seguros. Sugere-se a continuidade deste estudo, com alteração do músculo e atividade funcional eliciada pela estimulação elétrica, bem como uma ferramenta alternativa na mensuração e detecção da fadiga muscular.