Figure 4

Recordings from two muscle spindle afferents in separate but similar cat experiments in which a mechanical feedback motor was used to deliver L₆ manipulative thrusts of 25 ms (A) and 50 ms (B) duration without a tissue preload. In (A) there was a cessation of discharge (0.3 s) following a 24.5 N thrust, while in (B) there was a decrease in discharge (3.47 s) following a 19.6 N thrust. Cat body weight in (A) was 5.1 kg and in (B) 3.2 kg. Similarity in muscle spindle response characteristics between less forceful thrusts delivered by a feedback motor and greater forces delivered by the Activator IV device suggests a possible plateau effect for thrust magnitude on muscle spindle response.