The Role of the Sensorimotor System in the Athletic Shoulder
The Role of the Sensorimotor System in the Athletic Shoulder
ABSTRACT & COMMENTARY
Synopsis: The sensorimotor system plays an integral role in maintaining and restoring functional stability to the shoulder by mediating static and dynamic components of afferent proprioception and the efferent neuromuscular responses that result.
Source: Myers JB, Lephart SM. The role of the sensorimotor system in the athletic shoulder. J Athl Train 2000;35(3): 351-363.
This paper explains the sensorimotor system and discusses the role of this system as it relates to functional stability, joint injury, and muscle fatigue in the athletic shoulder. Myers and Lephart review the literature related to the sensorimotor system, and discuss some of their own research in the Neuromuscular Research Laboratory at the University of Pittsburgh. A scientific basis is established for a functional rehabilitation protocol that restores functional stability in the injured shoulder.
Myers and Lephart explain that the sensorimotor system encompasses the sensory, motor, and central integration and processing components of the central nervous system (CNS) that contribute to functional shoulder stability. The sensory, or proprioceptive information, is conveyed to the CNS from mechanoreceptors located in the muscle, tendon, fascia, joint capsule, ligament, and skin about the shoulder joint. This information activates the dynamic restraints responsible for maintaining functional joint stability; a mechanism known as neuromuscular control. The primary neuromuscular control mechanisms contributing to functional shoulder stability include coactivation of glenohumeral and scapulothoracic musculature, reflex stabilization, preparatory activation, and muscle stiffness.
Myers and Lephart describe a paradigm in which injury to the stabilizing capsuloligamentous and/or musculotendinous structures of the shoulder can result in mechanical instability, which can disrupt the normal proprioceptive feedback arising from the mechanoreceptors about the joint. This disruption of tissue and normal proprioceptive feedback leads to a cyclic progression of functional instability in the shoulder.
Myers and Lephart next propose a functional rehabilitation program designed to restore proprioception and neuromuscular control following shoulder injury. The four facets of this program include awareness of proprioception, dynamic-stabilization restoration, preparatory and reactive muscle facilitation, and replication of functional activities. Specific exercises are proposed to address each of these components of functional rehabilitation.
COMMENT BY DAVID H. PERRIN, PhD, ATC
This paper appears in a Journal of Athletic Training special issue on the shoulder. The role of the sensorimotor system in functional stability and joint injury has received considerable attention in the literature as related to the ankle and knee. Far less research has focused on the shoulder. This paper is an excellent overview of the concepts associated with the sensorimotor system of the shoulder, and provides a scientifically based program for restoration of proprioception and neuromuscular control following injury.
In addition to the aforementioned concepts, the paper also emphasizes the importance of assessing the various components of the sensorimotor system as part of a shoulder injury evaluation and treatment protocol. The recommended assessment for proprioception includes threshold to detection of passive motion and joint reposition sense. Neuromuscular control assessment includes muscle activation patterns through electromyography, muscle performance with isokinetics, and functional performance tests. Several assessment techniques are accessible to clinicians and are either described or referenced in the paper.
This special issue of the Journal of Athletic Training includes several excellent papers related to injury, evaluation, treatment, and rehabilitation of the shoulder. For a comprehensive review of the sensorimotor system, I recommend the text, Proprioception and Neuromuscular Control in Joint Stability.1
Reference
1. Lephart SM, Fu FH, eds. Proprioception and Neuromuscular Control in Joint Stability. Champaign, Ill: Human Kinetics; 2000.
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