Functional electrical stimulation–assisted cycling training improves lower limb function in chronic stroke survivors

A longitudinal pilot study by the Chinese University of Hong (CUHK) and Northwestern Polytechnical University in Xi’an, China, used electrical impedance myography (EIM) and surface electromyography (sEMG) to demonstrate that functional electrical stimulation (FES)–assisted cycling training improves lower limb function in chronic stroke survivors through increasing muscle impedance properties, improving muscle activation capacity, and allowing better muscle coordination during ankle joint movements.

FES-assisted cycling training was previously shown to improve walking ability of chronic stroke survivors through positive orthotic effects from FES and symmetrical coordination of muscle contraction during cycling. [Yale J Biol Med 2012;85:201-215; Eur J Transl Myol 2016;26:6063]

“FES and cycling training are common strategies for improving ambulatory function in rehabilitation after stroke, but the inherent muscle changes after such training have not been fully explored,” wrote the researchers. “We applied EIM and sEMG to track the changes in lower limb muscles so as to assist clinical evaluation of the effect of training on muscle weakness and functional deficits of chronic stroke survivors.” [Front Neurol 2021;doi:10.3389/fneur.2021.746263]

Fifteen individuals with hemispheric stroke (nine women and six men; mean age, 58.1 years) and no history of antispastic medication use for 6 months before training or during training were recruited in the study. The EIM and sEMG parameters were compared between the paretic and nonparetic sides before and after training across four muscle groups.

Significant differences in both EIM and sEMG values were found between paretic and nonparetic sides before training, as well as in the paretic side after training, which corresponded with the significant increases in clinical scores (Fugl-Meyer Lower Extremity [FMA-LE], p=0.013; Fugl-Meyer Assessment for ankle joint and coordination [FMAac], p=0.02; 6-minute walk test [6MWT], p=0.009; Berg Balance Scale [BBS], p=0.038) after training.

“The results demonstrate that after training, muscle activation increased and muscle contraction coordination within ankle joint movements improved. Significant correlations were found between EIM and clinical scores, as well as between sEMG and clinical scores. Lower extremity motor function improved after training, and the study participants acquired better balance and ambulation performance,” commented the researchers.

Results of EIM and sEMG assessment reflected that muscle cross-sectional area and muscle mass increased after training, while intramuscular fat tissue volume decreased. “After training, the composition and structural properties of paretic-side tibialis anterior muscle changed to resemble the same muscle on the nonparetic side more closely, which may facilitate the increase of muscle activation volume during ankle dorsi-flexion,” noted the researchers.