If you were able to gather up your stomach muscles and manually scrunch them up (that is, to contract them) you’d find that a couple of things happen:
This process of the muscles on one side relaxing when the muscles on the other side contract is called reciprocal inhibition.
Another example would be the muscles in your thighs – if you bend your knee, the hamstrings contract (tighten)… and the quads relax to allow the movement to happen.
On the other hand, if you want to kick a ball, your quads will contract powerfully to provide the kick and your hamstrings will lengthen out to allow the movement.
To be technical about it, muscles that cause the opposite movement to the desired one are inhibited from contracting (effectively allowing them to be stretched).
So if the abs are contracted ,it’s not that the back muscles actually relax, it’s just that they don’t contract.
If that didn’t happen then you’d have muscles on opposite sides of the body both trying to contract against each other which could be a problem.
Think again about kicking that ball – if the quads contracted and the hamstrings weren’t “switched off” then there’d be a quick powerful contraction on both sides of the thighs.. something would have to give, and it would be a muscle tear!
Muscles that do the same thing (cause the same movement) are called agonist muscles.
So for example, the biceps and the muscle that helps bend the elbow called the brachioradialis agonists. They both cause the elbow to bend – a movement called flexion of the forearm.
Muscles that do the opposite movement are called antagonist.
So the antagonist muscle to the biceps is triceps, because it straightens the elbow out after the biceps have flexed it.
When agonists contract, reciprocal inhibition causes antagonists to relax.
Within each muscle, are organs called muscle spindles . Being located within the belly of the muscle itself, when a muscle like the bicep contracts, the muscle spindle contracts.
The Golgi Tendon organ that sits between the muscle and the tendon that it connects to, also senses the increased tension when the muscle contracts.
Electrical impulses are sent from the muscle spindles and the Golgi Tendon organs via the nerves to the spinal column notifying the nervous system of the contracting position of the muscle (e.g. the bicep).
To permit continued contraction of the bicep, the nervous system initiates signals within the spinal column to be sent out via the nervous system to the muscle spindles and the Golgi Tendon organs within the antagonist muscles (in this case, the triceps) instructing the muscles to “switch off” and relax – allowing them to stretch out to accommodate the contraction within the opposing agonists.
All of this becomes useful to the sports person in warming up before sport.
Active stretching – for example, leg circles for footballers that get progressively bigger over a period of a minute or so – is great for pre-match warm up.
This active stretching uses the principle of reciprocal inhibition – in the case of leg circles, with hamstrings and quads alternately contracting and switching off (to allow progressively greater stretching).
If you’re already a client of mine, you’ll recognise all of this from the treatment that you get with me.
I use reciprocal inhibition all the time, in a treatment called Muscle Energy Technique, to help stretch out tight muscles. Muscles that respond particularly well to reciprocal inhibition in treatment include:
As ever, if you think I can help, give me a call.