Proprioceptors Chapter 3.2 Slides PDF

Proprioceptors Proprioceptors Sensory receptors in the muscles and tendons that are sensitive to stretch, tension, and pressure  Ex.Muscles spindles and golgi tendon organ  Occurs before conscious awareness Almost instantaneously relay information about muscular dynamics and limb movement...

Proprioceptors Proprioceptors Sensory receptors in the muscles and tendons that are sensitive to stretch, tension, and pressure  Ex.Muscles spindles and golgi tendon organ  Occurs before conscious awareness Almost instantaneously relay information about muscular dynamics and limb movement to conscious and subconscious portions of the CNS Allows continual monitoring of the progress of any sequence of movements and serves to modify subsequent motor behavior  Importantfor powerful, complex coordinated movements  Can enhance muscle relaxation Proprioceptors Fig. 3.9. Kenney et al. 2015. Physiology of Sport & Exercise. Hum.Kin. Proprioceptors Lengthening a muscle → Ac vates muscle spindles → Triggers contraction of that muscle Contracting a muscle (forcefully) → Ac vates GTOs → Relaxes the muscle https://www.youtube.com/watch?v=7T4NI_2qDEM  Muscle Spindles Provide mechano‐sensory information about changes in muscle fiber length and tension Primarily respond to any stretch of a muscle and initiate a stronger muscle action to counteract this stretch Initiates a stretch reflex Important to utilize for powerful contractions Important to minimize when relaxing a muscle Fig. 19.13. McArdle et al. 2010. 5 Exercise Physiology… LWW  Neurophysiological Model of Stretch Reflex Activation of muscle spindles initiates a stretch reflex  Known as “pre‐loading” the muscle Three main components:  Muscle spindle that responds to stretch  Afferent nerve fiber that carries the sensory impulse from the spindle to the spinal cord  Efferent spinal cord motor neuron that activates the stretched muscle fibers Fig. 19.14. McArdle et al. 2010. Ex. patellar reflex Exercise Physiology… LWW  Mechanical Model of Stretch Reflex Elastic energy in tendons and muscles is increased with a rapid stretch (eccentric muscle action) and then briefly stored. If a concentric muscle action follows immediately, the stored energy is released, contributing to the total force production. If a concentric muscle action does not occur immediately following the eccentric action, then the stored energy dissipates and is lost as heat.  Plyometric Mechanics and the Stretch Shortening Cycle The stretch‐shortening cycle (SSC) combines mechanical and neurophysiological mechanisms and is the basis of plyometric exercise. A rapid eccentric muscle action stimulates the stretch reflex and storage of elastic energy, which increase the force produced during the subsequent concentric action. Table 16.1. Baechle et al. 2009. Essentials of Strength… Human Kinetics 8  Flexibility and Stretch Reflex Proprioceptors and Stretching Fig. 13.7. Baechle et al. 2009. Essentials of Strength… Human Kinetics  Static  Dynamic  Ballistic A stretch reflex occurs when muscle spindles are stimulated during a rapid stretching movement. Limits muscle relaxation  Proprioceptive Neuromuscular Facilitation (PNF) Stretching  Activate GTOs prior to stretch  Golgi Tendon Organs When stimulated by excessive tension, Golgi tendon organs  Inhibit agonists, excite antagonists  Prevent excessive tension in muscle/tendon  Reduce potential for injury Detect differences in the tension generated by active muscle to protect the muscle and surrounding connective tissue from injury from sudden or excessive load  GTO activation directly related to load applied Fig. 19.15. McArdle et al. 2010. Exercise Physiology… LWW Review Questions Distinguish between muscle spindles and GTOs on their functions and how they are activated Distinguish between the neurophysiological model and the mechanical model of the stretch reflex Discuss the 3 phases of the SSC Briefly explain the role of the proprioceptors in stretching Explain the benefits of GTO activation Figure & Notes References Kenney, Wilmore, Costill. Physiology of Sport and Exercise (5th ed). Human Kinetics, 2011. McCardle, Katch, Katch. Exercise Physiology: Nutrition, Energy, and Human Performance, 8th Edition. Wolters Kluwer Health, 2014. Baechle & Earle. Essentials of Strength & Conditioning, 3rd Editiion. Human Kinetics, 2009.