Do spindle afferents monitor joint position in man? A study with active position holding.

The activity of human spindle afferents from finger extensor muscles has been studied during voluntary position holding at two finger positions, to disclose any explicit monitoring of muscle length. The results indicate that, taken as groups, neither primary nor secondary afferents show explicit position responses during active position tracking. Thus any contribution from muscle spindle to position sense must be derived from other components in spindle afferent discharge.