Proprioception. It’s that little sense that lets you know where the body is in relation to its various segments and the external environment. Also known as kinesthetic awareness. You have receptors (proprioceptors) located in the skin, in and around the joints and muscles, and in the inner ear that send back information to tell you where you are.
Today we’re going to talk about the proprioceptors located in and around the joints and muscles – specifically the muscle spindles and Golgi Tendon Organs (GTO). These musculotendinous receptors provide feedback regarding muscle tension and length so that the body can manage muscular control and coordination.
Chapters 1 and 5 in ACE’s Essentials of Exercise Science for Fitness Professionals are where you are going to find the most information on inhibition, muscle spindles and GTO. The muscle spindle is a proprioceptor that provides information about changes in muscle length – it responds to stretch, dynamic and static changes in muscle length. The GTO is another type of proprioceptor that provides information about changes in muscle tension – it responds to force.
GTO are located within tendons and are generally less active, less numerous, and slower to react than muscle spindles which are located within skeletal muscles.
When we talk about muscles contracting, we also have to talk about what stops those muscles from contracting (inhibition). Why would we want to stop a muscle from contracting? Usually for reasons involving safety and injury prevention, but also to help your muscles contract and relax to help you maintain a nice upright posture. When you are dealing with flexibility, inhibition can help to increase the stretch and increase muscle extensibility. There are two primary types of inhibition – autogenic inhibition and reciprocal inhibition.
Autogenic inhibition occurs when the GTO is activated by a force exerted on the muscle tendon, causing reflex inhibition (relaxation) of the contracting muscle and contraction of the agonist. The inhibitory signals from the GTO are trying to override excitatory impulses from the muscle spindles and cause gradual relaxation. For example, if you hold a hamstrings stretch for 7- 10 seconds, the increase in muscle tension activates a GTO response and inhibits the muscle contraction, allowing for greater stretching.
Reciprocal inhibition is relaxation of the antagonist muscle in response to contraction of the agonist. For example, firing the gluteus maximus (the agonist) for 6 – 15 seconds reciprocally inhibits the hip flexors (antagonist) temporarily, allowing the hip flexors to then be stretched.
If you’re interested in more in-depth information on inhibition and stretch reflex you can check out Chapter 5 in the Essentials Manual. For other questions you might have, you can contact us at 1-888-825-3636 x782 and speak with one of our Education Consultants!