Functional Electrical Stimulation (FES) Reduces Intermittent Claudication (IC) and Improves Quality of Life (QOL) Measures: A Cohort Crossover

Research Article

Phys Med Rehabil Int. 2017; 4(5): 1130.

Functional Electrical Stimulation (FES) Reduces Intermittent Claudication (IC) and Improves Quality of Life (QOL) Measures: A Cohort Crossover

Alon G¹*, Embrey DG², Brandsma BA², Vladimir F³, Silva A², Pflugeisen BM², Sherif D² and Amoroso PJ²

¹Department of Physical Therapy & Rehabilitation Science, University of Maryland, School of Medicine, Baltimore, USA

²MultiCare Institute for Research and Innovation, Tacoma WA, USA

³Swedish Hospital, Seattle WA, USA

*Corresponding author: Gad Alon, Department of Physical Therapy & Rehabilitation Science, University of Maryland, School of Medicine, 100 Penn Street, Baltimore, MD 21201, USA

Received: September 29, 2017; Accepted: October 18, 2017; Published: October 25, 2017


Aim: This crossover investigation applied functional electrical stimulation (FES) to the dorsiflexors (DF) and plantarflexors (PF) during walking in the home environment, hypothesizing that it will reduce intermittent claudication (IC), improve walking distance, and enhance quality of life measures compared to three baseline data points during which FES was not provided.

Methods: Nine male patients, 68.4�4 yrs old, and ankle-brachial index between 0.4-0.8 who completed 16 weeks walking 1hr, 6 days/week without FES consented to walk the same amount wearing FES applied bilaterally to the DF and PF. Measurements of perceived pain intensity (PPI) at the end of a 6min walk test (6MW), walking distance, peripheral arterial disease quality of life (PADQOL), intermittent claudication questionnaire (ICQ) and timed up and go (TUG) were obtained at baseline (T0), after 8 weeks walking without FES (T1), after 8 weeks follow up (T2) and after 8 weeks walking with FES (T3). Repeated ANOVA was used to analyze the data and significance was assessed at the P<.05 level.

Results: PPI at T0 was 51.3�19.4 and significantly dropped to 9.9�11.1 (p<.001) at T3 registering a large effect size (?2=.42), PADQOL factor 3 improved by 14.8 points between T0 and T3 (p=.01; ?2=.36) and ICQ score improved by 16.3 points (p=.004; ?2=.36). The 6MW distance and TUG did not change during the study.

Conclusion: This crossover study added validity to the hypothesis that applying FES while walking can markedly diminish the intermittent claudication pain and improve quality of life measures in community ambulatory patients with PAD and IC.

Keywords: Intermittent Claudication; FES; Pain; Walking


Functional electrical stimulation (FES) is a common intervention option in rehabilitation medicine supported by robust peer-reviewed publications [1-4]. With the advent of biomedical electronics, the adoption of wireless wearable FES systems is gaining acceptance in clinical practice over the more traditional, non-wearable, wiredependent devices collectively known as neuromuscular electrical stimulators (NMES) [4]. The primary advantage of wearable FES systems is enabling many patients to improve performance in activities of daily living (ADL). Several investigators tested the benefit of using wearable FES on improving the ability to walk following damage to the brain. Springer and colleagues [5] reported that after training for 6 weeks using a dual channel wireless FES, subjects with limited household ambulation capabilities improved their gait speed by 63.3%, while subjects with functional community ambulation capabilities improved their gait speed by 25.5%. Kluding et al examined the benefits of walking for 30 weeks with a wireless FES designed to control foot drop associated with damage to the brain, comparing it to articulated ankle-foot orthosis (AFO), and concluded that the FES yielded clinically and statistically significant improvements in gait speed and other functional outcomes including greater patient satisfaction with using the FES compared to using the AFO [6]. These advanced FES systems to control foot drop are also benefiting pediatric patients with brain damage after daily use for at least a year [7].

Before wearable wireless FES systems were commercially available, wires-dependent non-invasive FES were applied during daily activities to help patients suffering from stroke, multiple sclerosis (MS), traumatic brain injury (TBI), or Parkinson�s disease, and a number of investigators reported improved locomotion while using wire-dependent FES [1,8-11] and less favorable outcomes using only AFO [12]. Moreover, numerous clinical studies using NMES to induce muscle contraction in the absence of functional training, typically limit clinical outcome to minimize impairments. Specifically, clinical data support the use of NMES to significantly increase total RNA content and reduce protein degradation in post-operative patients [13], improve physical performance, partially reverse sarcopenia by increasing muscle cross section area and capacity to perform daily activity [4,14], and increase the body�s glycolytic metabolism in patients with type-2 diabetes mellitus [15,16].

Applying wearable FES to patients with peripheral arterial disease (PAD) while walking is a novel approach aimed at reducing intermittent claudication (IC), improving walking distance, and enhancing quality of life measures. We recently published a manuscript [17] detailing the effects of walking for one hour, six days each week, for eight weeks on three primary outcome measures: the perceived pain intensity (PPI) at the completion of the 6-min (6MW) walk test, the distance walked in six minutes, and the Peripheral Arterial Disease Quality of Life (PADQOL) measures. One group using FES while walking (FES+Walk) was compared to a group walking at the same prescribed dose, but without FES (Walk). Both groups were followed for additional 8 weeks after completing the 8-week training. The FES+Walk group experience marked drop in IC (PPI score) dropping 65.5% at the end of the follow-up, while the WALK group PPI scores increased 8% in the same time period. The walking distance of the FES+Walk increased by 42.2 meters (14.5%) compared to only 24.4 meters (8.5%) and the factor 3 of PADQOL score of the FES+Walk group increased by 12.9 points compared to only 5.1 points of the Walk group. At the completion of the follow up period, patients in Walk only group were offered the FES to apply at home for 8 weeks thus enabling to extend the study as a crossover design. The aim was to test if the benefits of FES+walk reported in the original study could be reproduced. The specific hypothesis of this crossover investigation was that applying FES to the dorsiflexors (DF) and plantarflexors (PF) during walking in the home environment will reduce intermittent claudication, improve walking distance, and enhance quality of life compare to the three baseline data points in which FES was not provided.


Patients in this study (N = 9) chose to participate in the crossover phase and receive FES. The crossover protocol was approved by the local institutional review board. Of the five patients choosing not to continue participation, three stated they are walking fine and not interested in FES, one developed foot ulcer and was unable to walk and one patient declined due to financial hardship. Participating patients were ambulatory, community dwelling adults diagnosed with PAD and IC with an Ankle Brachial Index (ABI) between 0.4 and 0.8. All patients received standard care by their primary physicians, defined as conservative (non-surgical) management of signs and symptoms of PAD, and prescribing appropriate medications to including those to improve circulation and manage pain.

Outcome measures

Baseline (T0), post-treatment (T1) and follow up (T2) measures were collected according to the protocol from the original study [17]. The crossover data (T3) documented outcome measures for the nine patients enrolled in the crossover phase. Five measures included: 1) Walking distance was determined by measuring meters traveled during the 6MW test [18]. If patients were unable to walk the full six minutes, they were allowed to sit and rest until they were ready to continue. 2) The PPI was used to determine the severity of ischemic walking pain. After the 6MW, investigators asked patients to rate their ischemic pain in their lower legs by placing a hatch mark on a 0-100mm horizontal line. Patients were instructed that 0 meant �no pain� and 100 meant �the most intense pain ever experienced.� 3) Changes in lifestyle were measured using Factor 3 (Symptoms and Limitations in Physical Functioning) of the Peripheral Arterial Disease Quality of Life (PADQOL) questionnaire [19]. 4) The Intermittent Claudication Questionnaire (ICQ) measured the impact of walking pain on quality of life. This measure has been shown to be a reliable and valid measure of quality of life for patients with IC [20]. 5) The Timed Up and Go (TUG) measured the time (sec) needed for patients to stand up from a standard chair, walk 3 meters, walk around a cone, return to the chair, and sit down. A video camera perpendicular to the walkway recorded this task to assure accurate data collection.

Intervention procedures

Patients were instructed to walk one hour per day, six days per week, in their natural environment while using the FES system during the 8-week phase. Patients kept a daily log to document walking time per day, physician visits, medication changes, and any unforeseen complications. Weekly visits provided the investigator an opportunity to review daily logs, respond to questions, and monitor FES application.

FES system

The FES system provided electrical stimulation to the DF and PF while the patient was walking (Figure 1a). Each FES unit contained a motion sensor that automatically triggered muscle contractions of the PF (40% of the gait cycle) and DF (60% of the gait cycle). Customized software allowed adjustments in the intensity (�coul) and pulses/s (PPS) of each FES unit. This specific FES system delivered symmetrical biphasic waveform pulses, at a rate of 25PPS to the DF and 8-15 PPS to the PF. Stimulation intensity for each patient was adjusted by increasing the phase charge (�coul) of each channel.