Carryover effect after functional electrical stimulation treatment – pilot study for a quantitative approach

Functional Electrical Stimulation (FES) has been reported to be an effective treatment for neurological patients, e.g. post-stroke patients. Besides beneficial effects at muscles themselves, a re-learning process named carryover effect has been observed in some patients. This work aims at defining a quantitative method to assess the carryover effect in a group of patients, starting from a set of outcome measures that are specific to the considered treatment. Fifteen post-stroke chronic subjects have been recruited for 20 half an hour sessions of FES-based treatment for Foot Drop correction during ambulation. Gait velocity, a spatial asymmetry index, a temporal asymmetry index, endurance velocity and tibialis anterior activation index during gait have been selected as outcome measures. After the analysis performed with the proposed method based on principal component analysis, 50% of patients presented the carryover effect. The proposed approach is a quantitative method that can be applied to any set of outcome measures of interest. The results could inform further studies aimed at identifying the carryover effect mechanism of action.