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Muscle Innervation (Our Little Secret)

When it comes to Sporting Performance and avoiding injury we find there is one technique of therapy/training that rules them all. It is a technique that is very often neglected or misunderstood and in most cases our clients are unaware we are doing this. Personally I feel this is why we are able to consistently achieve the outstanding results we see in the clinic each and every day.

I am of course talking about Muscle Innervation, sometimes referred to as Muscle Energy Techniques (METs). During this blog we will dive deep into some Sports Science to help you understand how they work, why they work and how you can work on this yourself.

Neuromuscular innervation

So often we see injuries because of poor or limited muscle innervation, but what does this mean and importantly how can we improve our muscle innervation?

Muscle innervation is the key to moving better, stronger, and importantly injury free! In this blog we will explore how muscles work, the sliding filament theory, actin and myosin and the neuromuscular junction.

How And Why Do Muscles Work?

So, to begin let’s break down movements, in this blog we will use the gluteus maximus as the muscle in focus as this is where we use muscle innervation techniques the most during clinic time. The primary movements of the Glute Max are extension of the hip and external rotation of the hip, this is important to note when we come to innervation techniques later. For muscles to contract the brain sends a signal through the central and peripheral nervous system and into the muscles neuromuscular junctions. Each muscle body (Epimysium) is made up of hundreds of smaller muscle fibres (Fig 1.), it’s the contracting of the muscle fibres collectively that enables muscle to create powerful movements.

Sliding Filament theory

So how does a muscle physically contract? This is where actin and myosin filaments come in to play. When viewed under the microscope. muscles are made up of thousands of sarcomeres in a very linear pattern. Each Sarcomere contains many Actin and Myosin filaments, once a signal is received through the neuromuscular junction to contract the actin and myosin slide over each other to shorten the length of its respective sarcomere causing the entire muscle body to shorten and pull on the relevant tendon. This is a hugely complicated process, but all you need to understand is that the contracting of each individual sarcomere collectively causes muscle contractions.

The Neuromuscular junction

For the sliding filament theory to work they are reliant on a stimulus from the nervous system telling them whether to contract and relax and with how much force (effectively eccentric and concentric muscle contractions). Each muscle is innervated or controlled by a motor unit made up of motor neurons. These motor units are responsible for recruiting the correct muscle fibre (Slow twitch for low intensity activity and fast twitch for high intensity activity) they are also responsible for how many muscle fibres we recruit and this is where muscle and neuromuscular innervation is important. In an untrained individual or someone with poor muscle function the body might only be using around half of the muscle fibres within a muscle. So using the glute as an example when we try to extend at the hip the motor units send signals to the muscle fibres in the glute to contract but this signal might only get through to half of the available fibres meaning for a limited and weak contraction. In highly trained athletes with good muscle function they will be able to recruit more than 95% of there muscle fibres meaning for a strong and controlled contraction leading to optimal performance and a hugely reduced risk of injury.

The Neuromuscular junction is made up of all the muscles within the body and the nerves that serve them. The motor unit is the functional unit of this system which sends signals to each muscle fibre. An untrained athlete will only use around 50% of the muscle fibres within each muscle, whereas a highly trained elite athlete will be using around 95% of their muscle fibres. The most efficient way to address muscle imbalances and strengthen muscles is to increase the amount of muscle fibres we recruit when asking a muscle to work.

So how does Muscle Innervation work?

This is the primary bit of Sports Science we use in every single bit of work we do, whether this is during treatment or included within a client’s rehab programme. For increased strength and muscle function we need to isolate muscle groups and muscle fibres so that each motor unit is having to act correctly. This is hugely complex, but you do not need to worry about that, break movements down, consistently undergo S&C work and isolate muscles and movements.

Muscle innervation can be improved relatively quickly, within a couple of weeks if done consistently. If you have ever started a new movement or starting lifting weights in the gym having never done it before then you will have experienced this firsthand. The first few sessions will feel slightly uncoordinated and not very strong with heavy DOMs after that last a good few days. This is because muscle fibre recruitment is poor and the fibres themselves might not be that strong. Within the first couple of weeks, if you are consistent with your weight training, you will notice a big difference in strength, heavier weights, more coordinated movements and far less DOMs. This is primarily to do with a stronger Neuromuscular junction, more motor units and ultimately more muscle fibre recruitment.

How does this Prevent Injury and Improve Performance?

A healthy, pain free muscle contains strong fibres and a high concentration of fibres that are recruited during muscle contractions. A strong Neuromuscular junction will also help improve skill-based sports and exercises that require good technique. This is where the term muscle memory is often used. Sports such as golf require a complex amount of muscle movement in a very short period of time, practice makes perfect as they say. Each time we practice we are teaching the neuromuscular junction what we want it to do and might be making small adjustment to the signals we send it.

When a muscle is strong with good fibre recruitment it will be able to carry out it’s job with ease and without relying on other muscles to help out. An example of this is the relationship between the Glutes and the hamstrings. The primary muscles needed for hip extension (sprinting/running) is the gluteus maximus and assisted by the hamstrings, however in someone with poor muscle function in the glute the hamstrings will assist a lot more and takeover from the glutes leading to overuse injuries such as hamstring tendinopathy or worse a hamstring tear when under high load.

Keep your eyes peeled for a follow up post to see Muscle Innervation in action.

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