Using functional electrical stimulation on peroneal muscles: the effect on risk factors of lateral ankle sprain

There are approximately 10,000 lateral ankle sprains (LAS) occurring a day worldwide, with a significant impact on economy, workforce and individuals, with medical costs in the UK ranging from £940-£1,314 per injury. Long term issues have been reported in 70% of individuals, including pain and instability. A risk factor for LAS that has been identified is lateral centre of pressure (COP) during walking and running, however this is time consuming and costly to establish. One key aetiology of LAS, is incorrect landing with the foot in a more supinated position causing the COP to be lateral. 

The first study in the thesis (Chapter 3) is titled “Screening for laterally deviated plantar pressure during stance using the Cumberland ankle instability tool and anthropometric measures”. The Objective was to identify a novel method in which individuals with a lateral COP during running could be easily identified. 32 healthy males aged 18-45 years had foot pressure data collected whilst running on a treadmill for 2 minutes using a pressure insole system for classifying the participants as medial or lateral strikers. Data including height and body mass, lower limb anthropometrics (ankle range of movement (ROM), Knee ROM, calf circumference, foot length and width and arch height) was collected, the Cumberland Ankle Instability Tool (CAIT) and the Tegner activity level was also used. As a result of the study a model was created using binary logistic regression with the collected data, the model had a sensitivity of 71.4% and a specificity of 54.5% when identifying medial and lateral strikers. A validation trial was also done, comprising of 15 healthy active Asian males recruited by The Chinese University of Hong Kong it reported a 73.3% accuracy. The study concluded that it is possible to identify individuals with a lateral COP using basic anthropometric measures and the CAIT.

The second study (Chapter 4) is titled “Effect of 8-week treadmill running with peroneal muscle functional electrical stimulation on laterally deviated centre of plantar pressure position and star excursion balance test performance”. This study follows on from the previous study using participants that were identified as having a laterally deviated COP. The Objective was to establish the effect that an 8-week training protocol using FES has on both COP position and SEBT performance. A group of 14 healthy males with a laterally deviated COP during running were recruited from study 1 they were single blinded into a control or intervention group. Participants in the intervention group were allocated a level of FES stimulation to their peroneal muscles based upon comfort. Participants ran on a treadmill for 15 minutes at a comfortable place twice a week for 8 weeks. As part of data collection COP position data were collected at 3 time points (immediate, post intervention, 4 week follow up). SEBT was also assessed pre and post intervention. On analysis there was a significant difference in the results post intervention at max pressure for intervention M=0.7(±0.7) and control M=-6.0 (±4.6) conditions; t(6)=-2.9, p<0.05. At the conclusion of the study FES was found to have an effect, moving COP position from lateral to medial. SEBT has also been found to improve in posterior, posterior-medial and posterior-lateral directions.

A third study (Chapter 5) is titled “Functional electrical stimulation of peroneal muscles on balance in healthy females: a cohort study”. This study focused on balance and FES, impaired balance is linked with lateral ankle sprain risk and has been associated with peroneal strength and reaction times. The objective was to assess the effect of FES on balance using total COP excursion length. Fifteen healthy females performed single and double-leg standing balance tests with eyes open and closed on a force plate, before and after 15-minute FES intervention during treadmill running. The total excursion of COP in single and double-leg stance with eyes open reduced significantly after FES intervention by 14.7% (p < 0.001) and 5.9% (p = 0.031) respectively. The eyes closed condition exhibited a 12.7% (p = 0.002) reduction in single-leg stance but did not significantly change in double-leg stance (p > 0.05). In conclusion the study identified a positive impact from the programme with an increase in balance for both single and double leg stance.

Overall, these studies have identified a potential tool to detect individuals with a lateral COP in a clinical setting and use FES to both change COP position and improve balance.