Figure 5.

Experimentally determined relationship between velocity of the stretch and the stretch reflex threshold in elbow flexors in one patient with a stroke (A) and a healthy subject (B). Thresholds were determined as the velocity and angle corresponding to the onset of EMG activity in the biceps brachii during the stretch of the muscle when the subject was at rest. Velocity-dependent velocity/angle thresholds (black dots) varied with the speed of the stretch with slower stretches (lower lines) resulting in EMG activation occurring at higher joint angles than faster stretches (top curved lines). In the healthy individual, no stretch responses were evoked at slower velocities. Locations of the TSRT+ within (A) or beyond (B) the angular range of the joint were identified by extrapolation of a linear regression line through all the velocity-dependent thresholds to zero velocity.