Figure 3

Normalized fiber length/velocity curves and reflex modulation factors over the gait cycle. Normalized muscle fiber length (${\tilde{\mathit{l}}}_{\mathit{m}}$, top pane) and muscle fiber velocity (${\tilde{\mathit{v}}}_{\mathit{m}}$, middle pane) for the reference condition are shown as function of the gait cycle for soleus (SOL), gastrocnemius (GAS), vastus (VAS) and rectus femoris (RF). The left lower pane shows the plantarflexors reflex modulation factor (k _m ) for reference (black, experimentally measured) and stroke subjects (grey, according to Yang et al. 1991). The right lower pane shows the modulation curves for the quadriceps muscle, for reference (black) and stroke (grey) subjects, both according to Faist et al., 1999. The most prominent difference between stroke and control was the lack of suppression of plantarflexors H-reflexes and of quadriceps tendon jerk reflex in the swing phase. Intervals indicated on the X-axis correspond to specific phases of the gait cycle: 0-5%: Initial Contact, 5-20% Loading Response, 20-35%: Mid Stance, 35-50%: Terminal Stance, 50-70%: Pre-Swing, 70-80%: Initial Swing, 80-95%: Mid Swing, 95-100%: Terminal Swing.