Feedback-Controlled and Programmed Stretching of the Ankle Plantarflexors and Dorsiflexors in Stroke: Effects of a 4-Week Intervention Program

The intelligent stretching device used to repeatedly stretch the ankle joint in subjects with spasticity and/or contracture after stroke. The left panel shows the main components of the device, as described in the Methods section. The right panel shows the position of the subject during the stretching. The foot of the subject was fixated on the footplate, and the lower leg was fixed to a leg support. The stretching device was fixed to the chair to prevent the device from moving relative to the subject. Abbreviation: LED, light-emitting diode.

Typical data from a stretching trial, indicating (A) the dorsiflexion (DF) angle as well as (B) the joint torque during the stretching trials. It can be seen from the curves that as the ankle joint moves into extreme positions, the resistance torque increases and the stretching velocity decreases gradually until the maximum resistance torque (10Nm in this trial for both directions) is reached. After a holding period, the movement direction is reversed.

Torque-angle relation (hysteresis loop) obtained from the stretching data, indicating the relation between the ankle angle (positive indicates movement to dorsiflexion) and the resistance torque in the ankle. The curve is the average of 3 completed stretching cycles in a single subject. From the curve, the passive ROM at a controlled peak resistance torque (10Nm) was derived. The slope of the curve was used to estimate the quasistatic stiffness throughout the ROM; the joint viscosity was estimated through the energy loss in the hysteresis loop (the area enclosed).

Typical example of tendon tapping data of the Achilles’ tendon from a single stroke subject. The subject was asked to relax during the tendon tapping. Average data (solid line) and SD (dotted line) from 10 taps are shown for all signals. (A) Tendon tapping force; (B) medial gastrocnemius electromyographic (EMG) response; (C) torque response in the ankle around the plantar- and dorsiflexion axis; and (D) impulse response obtained by scaling the torque response to the tendon tapping force, with the vertical lines indicating, from left to right, the start of the tendon tapping and the onset of the torque response.