[Purpose] The purpose of this study was to determine the effects of functional electrical stimulation on muscle tone and stiffness in stroke patients.
[Subjects and Methods] Ten patients who had suffered from stroke were recruited. The intervention was functional electrical stimulation on ankle dorsiflexor muscle (tibialis anterior). The duration of functional electrical stimulation was 30 minutes, 5 times a week for 6 weeks. The Myoton was used a measure the muscle tone and stiffness of the gastrocnemius muscle (medial and lateral part) on paretic side.
[Results] In the assessment of muscle tone, medial and lateral part of gastrocnemius muscle showed differences before and after the experiment. Muscle stiffness of medial gastrocnemius muscle showed differences, and lateral gastrocnemius muscle showed differences before and after the experiment. The changes were greater in stiffness scores than muscle tone.
[Conclusion] These results suggest that FES on ankle dorsiflexor muscle had a positive effect on muscle tone and stiffness of stroke patients.
Muscle tone is defined as the resistance of muscle being passively lengthened1) . Abnormal muscle tone occurs in disorders of central nervous system and can affect up to two-thirds of patients with stroke2) . Especially, it is a common motor disorder following stroke, which may require rehabilitation3) . A hypertonus state leads to involuntary muscle contractions that interfere with the normal movements of the arms and legs, restrict the range of motion of joints, and lower extremity the functions of daily living, thereby restricting the functional recovery of patients4) .
Yan and Hui-Chan reported that functional electrical stimulation (FES) may be able to normalize muscle tone in affected ankle plantar flexors5) . FES is a popular post-stroke gait rehabilitation intervention. FES is typically delivered to ankle dorsiflexors to correct foot drop during the swing phase6) . FES is applied on the tibialis anterior muscle to enhance coordination capability during the gait cycle, and to increase the range of motion of the ankle joint and walking speed, thus improving gait quality7) . FES appears to enhance balance control during walking and, thus, effectively management foot drop in stroke patients8) . Cho et al. reported that treadmill training while FES was applied to the gluteus medius and tibialis anterior muscles increased lower limb muscle strength and improved balance and gait9) . Most previous studies assessed muscle strength and gait ability. However, few studies have assessed muscle tone and stiffness. Therefore, we investigated the influence of FES on muscle tone and stiffness in stroke patients.
Stroke survivors show significantly higher resistance torque and joint stiffness10) . Muscle stiffness, which is defined as a change in passive tension per unit change in length, is an indication of a muscle’s passive resistance to elongation11) . Ankle stiffness is associated with difficulty walking due to an asymmetric posture and a loss of balance and motor control12) . Limited ankle joint dorsiflexion is caused by calf muscle (gastrocnemius and soleus muscles) stiffness and soft contracture13) . Owing to an increase of muscle tension in the gastrocnemius muscle, stroke patients cannot actively control dorsiflexion, and foot drop tends to occur14) .
In this study, we hypothesized that FES applied to the ankle dorsiflexor (tibialis anterior) may reduce muscle tone and stiffness of the gastrocnemis muscle (medial and lateral part) in stroke patients.