Figure 2. Firing patterns of γ_s axons during spontaneous locomotion.

Traces from above downward are: EMG of TA (continuous) and MG (broken), ankle angle with TA shortening upwards, instantaneous frequency records of three single γ_s axons in a TA nerve filament. Note that all three γ_s axons are modulated in the same way with increasing discharge during TA muscle shortening.