A golgi what? I hear you saying. We agree, it’s not the most enticing blog title, but bear with us. The golgi tendon organ (GTO) is an important neuro-physiological sensory receptor of the peripheral nervous system (which basically means it connects the brain to the outside world) which we, as soft tissue therapists, need to know about. So we thought we’d share some of that knowledge with you.
These sensory receptors are found wrapped in the collagen fibres of tendons. They primarily detect increases in tension in the tendon, and therefore muscle tension. Their primary job is to protect muscle and any associated connective tissue from injury, which may be caused by excessive force or speed of contraction. When the GTOs are activated by an excess amount of muscle tension or stretch they will conduct very rapid signals to the Central Nervous System, causing a reflex inhibition of the muscle they supply.
As an example, if you were to attempt to catch a weight that was too heavy for you, the GTOs would respond by causing the bicep muscle to relax, resulting in you dropping the weight. They do this to prevent the muscle from being damaged.
So why are we explaining this to you? Well, one technique which we use during our soft tissue therapy treatments is known as Muscle Energy Technique (MET). MET is useful for many reasons: it can increase the range of movement in restricted joints, reduce muscle hyper- or hypo-tonicity and increase muscle/tendon strength. It is therefore a good technique to use for both injury rehabilitation and prevention.
There’s a couple of different ways to apply MET, one of them is known as post isometric contraction – PIR. By holding a sustained contraction of the target muscle the GTOs will be stimulated, which via an inhibitory effect in the spinal cord reduces the stimulation of the motor efferent nerves supplying the muscle. There is then a period of inhibition in the target muscle and we are able to utilize this time to stretch it gently, thereby gaining length in previously shortened muscle fibres and giving you greater range of movement/joint mobility.
The stimulation of GTOs is also an intrinsic factor that affects the degree of skeletal muscle tension. So by using MET we can also switch off a muscle which could be holding too much tension. This often happens around in injury site when muscles ‘guard’ the area to prevent re-injury. However, if that guarding continues long after the injury has healed it can be detrimental, and cause postural deviations, aches and pains. Increased muscle tension can also be due to postural deviations, so correcting them will mean less pain for you.