What is Neuromuscular Coordination?

Neuromuscular coordination

Neuromuscular coordination refers to the ability of your central nervous system to efficiently control and coordinate the contraction of a muscle, or group of muscles, in order to complete a specific task or movement. 

Developing neuromuscular coordination is an important, and often overlooked, factor in long term success in all sports (power, endurance and skill based):

  • In power or strength based sports it allows for a greater ability to exert a force, or to exert that force more efficiently. Examples include powerlifting, long jump, or sprinting.
  • With skill based sports it allows for greater control (improved accuracy, timing) of precise co-ordinated movements. Examples include baseball, basketball, golf or tennis.
  • In some cases there may be both a power and skill element. Examples include high jump, boxing and javelin.
  • With endurance based sports it allows for more efficient movement, reduced energy expenditure, and lower oxygen costs at a given speed or work rate. Examples include running, swimming, cross country skiing, or cycling.

Factors affecting neuromuscular coordination

Neuromuscular coordination works on two levels:

  • Intra-muscular coordination
  • Inter-muscular coordination

Intra-Muscular Coordination

The word “Intra” refers to something that’s within, so in this sense intra-muscular coordination refers to neuromuscular coordination “within” an individual muscle. Specifically it relates to the recruitment and coordination of groups of muscle fibers within a muscle. 

So, how are muscle-fibers recruited? At the most basic level, muscle fibres are recruited through something referred to as a motor unit. This consists of a single motor nerve and the associated muscle fibers, that it innervates (stimulates to contract). Following activation, the motor unit activates all of the associated muscle fibers.

Muscle Fiber Motor Unit

Importantly, each motor unit consists of just one type of muscle fiber (e.g. type I, type IIa, or type IIb). However, the number of individual muscle fibers within a unit varies between muscle groups. 

The type of motor units that are recruited (type I, type II etc) depends on the force of muscle contraction. At low intensities, it is primarily type I motor units. And as exercise intensity increases type II motor units are also recruited.

One interesting point is the level of precision is inversely proportional to the motor unit size. As a consequence large muscle groups (quadriceps, hamstrings, glutes) have larger motor units that generate more force but are less precise. In contrast, smaller muscle groups (those responsible for the movement of your eyes, fingers etc) have smaller motor units, which allows more precision but less force. 

Improved Intra-muscular coordination allows for a greater ability to control the application of force within an individual muscle. 

Intra-muscular coordination is dependent on two factors:

  1. Rate coding
  2. Recruitment of Neuromuscular motor units

1. Rate Coding

Rate coding refers to the control of the firing or discharge rate (number of action potentials in a given time) of motor units. As rate coding increases, it influences the contraction speed and (consequently) the force exerted by that motor unit. As such, improvements in the motor units discharge rate can have a beneficial effect on intra-muscular coordination. 

Importantly, strength training is known to have a beneficial effect on rate coding. This leads to significant increases in the discharge rate of motor units.


2. Recruitment of Motor Units

Whereas rate coding refers to the frequency of action potentials, motor unit recruitment refers to the amount of motor units recruited during a muscle contraction. Essentially, it refers to the ability to recruit motor units during exercise or activity. In this way, it’s a measure of how many motor units – and consequently muscle fibers – are recruited within a muscle. 

As you would expect, increased motor unit recruitment leads to increased force production. Importantly, motor unit recruitment can be significantly increased through specific training. 

Untrained individuals have a limited ability to recruit motor units. 

Highly trained athletes are able to recruit much higher percentages of a muscles motor pool (the collection of all motor neurons within a muscle) during exercise. 

Strength training, and particularly maximum load training and plyometrics, is one of the most effective ways to increase your ability to recruit motor units. It’s also one of the most effective ways to improve exercise efficiency.

One advantage here, is that it provides athletes with a greater pool of motor units to utilise during exercise. Effectively, this increases maximum force production, but it also improves exercise efficiency at sub-maximal intensities. 

Another effective, approach is to incorporate high intensity intervals. Overtime this leads to an increased ability to recruit greater percentages of muscle fibres

In addition to rate coding and muscle fibre recruitment, it’s believed that motor unit synchronization may play a role.


3. Synchronization of motor units

This refers to the ability of the nervous system to synchronise the discharge of action potentials in multiple motor units. Importantly, synchronization of motor units refers to the synchronization of motor units with a similar recruitment threshold: for instance, the synchronization of type 1 motor units. 

It’s not clear as to the extent to which synchronization actually occurs and whether there is a functional benefit However, it may “increase the rate of force development during rapid contractions” or help to “coordinate the activity multiple muscles to promote skilled muscle synergies” (Semmler, 2002). As this implies the synchronization may also work on an inter-muscular level.

Inter-muscular coordination

Inter-muscular coordination refers to the interaction and level of coordination between different muscle groups. Importantly, this relates to the interaction between multiple muscles and the actions of those muscles during a specific task or activity. Primarily, this refers to the level of neuromuscular coordination between:

Agonists – the working muscle or prime mover i.e. the primary muscle(s) responsible for the movement

Antagonists – the opposing muscle group i.e. with the opposite action to the agonist. To improve inter-muscle cordination antagonist

Synergists – perform or assist with the same joint movement as the agonist. This may involve stabilising a joint, or reducing unwanted movement from the agonist. 

As with Intra-muscular coordination, when you increase the level of inter-muscular coordination, you increase the ability of muscles and groups of muscles to exert a force. It also improves the efficiency of movement. In practical terms, this means more force can be applied with less effort.

Not surprisingly, a low level of inter-muscular coordination will adversely affect performance. This becomes increasingly important with more coordinated movements such as sprinting and hurdling, where it allows the working muscles to function to their maximum potential. As such, athletes often spend significant training time focussing on improving the efficiency and coordination between specific muscle groups.

In particular, this highlights the importance of deliberate practice (specific technique drills, focussed practice, conscious awareness of technique) and why it takes many years of deliberate practice to refine technique and achieve mastery of a skill.

How to Improve Neuro-muscular coordination

Improving neuromuscular coordination is a vital factor in any successful long term approach to training. Importantly, there are a number of effective approaches that should feature in any plan. While, the exact mechanism isn’t fully understood, improvements appear to be linked with adaptations to the myelin sheath that surrounds your nerve cells. These adaptations, lead to stronger, faster and more efficient movements.

As this is an endurance training website we’ll look at this from the perspective of an endurance athlete…

Strength training

Firstly, as I’ve mentioned in the article, strength training (maximum strength and plyometrics) is one of the best approaches as it increases rate coding, motor unit (and hence muscle fiber) recruitment, and improves the inter-muscular coordination between different muscle groups. In fact, it’s known that strength training is beneficial for endurance. One point to note here: to improve it’s effectiveness we want this to be as specific as possible (i.e. working muscles in similar ways to your target sport) – this is especially important with regards to improving inter-muscular coordination.

High Intensity Interval Training

High intensity interval training is beneficial for improving both intra and inter-muscular coordination. Helping to increase the recruitment of muscle fibers (both slow and fast twitch) and effectively increasing the available pool of motor units during exercise.

Sprint Intervals

Sprint interval training can prove to be beneficial especially in view of how this leads to peak recruitment of all muscle fiber types. Completing hill sprint training provides additional benefits since it further increases muscle fiber recruitment and brings in running specific strength training.

Training at Race Intensity

Training at race intensity is likely to be beneficial in improving neuromuscular coordination, especially at the inter-muscular level. This is important since it leads to improved efficiency at the specific intensity used in competition.

High Training Volume

A high volume of training can improve neuromuscular coordination by allowing further refinement of inter-muscular coordination. This believed to be particularly important for many endurance sports, where high volume of aerobic base training may provide greater benefits to efficiency than fitness.

Drills and Technique Work

Further improvements, come through consistent use of specific form and technique drills (agility, sport specific drills etc), that refine technique, coordinate faster movements and bring an additional plyometric component to training. However, one really important point here:

To be effective, drills must be targeted and specific, with attention focussed on technique. Often we see athletes just going through the motions with these drills. Without focussing attention on technique you may be reinforcing bad technique.

Reference

Semmler JG. Motor unit synchronization and neuromuscular performance. Exerc Sport Sci Rev. 2002 Jan;30(1):8-14. doi: 10.1097/00003677-200201000-00003. PMID: 11800501.