title: Muscle reaction to passive shortening in normal man.
abstract: We have studied in 32 healthy subjects the EMG activity of biceps and triceps brachii, wrist flexors and wrist extensors, triceps surae and tibialis anterior, sterno-cleido-mastoideus (SCM) and splenius, during their passive shortening. A shortening reaction was observed more frequently in wrist extensors, SCM and tibialis anterior than in biceps and triceps brachii. The response appeared only when the joint reached a specific angle regardless of the starting point or the speed used to reach this position. During a muscle ischaemia which abolished the tendon reflex the reaction was not modified. During a joint ischaemia produced distal to the examined muscle its amplitude was strongly reduced. Our results support the hypothesis that joint receptors could play a role in its origin, perhaps through a long-loop reflex.
mesh_terms: D000328:Adult; D004576:Electromyography; D006801:Humans; D007596:Joints / Q000502:physiology; D008875:Middle Aged; D009068:Movement; D009119:Muscle Contraction; D012018:Reflex / Q000502:physiology*; D012782:Shoulder / Q000502:physiology; D014953:Wrist / Q000098:blood supply / Q000502:physiology