Neuromuscular coordination relates to the ability of the nervous system to efficiently recruit a muscle or group of muscles in order to perform a specific task. Neuromuscular coordination works on two levels: 1) Intra-Muscular Coordination, 2) Inter-Muscular Coordination
Intra-muscular co-ordination - is the activation of individual neuro-muscular units within a muscle fibre. The activation of individual muscle fibres is dependent on rate coding (“firing rate” of action potentials), recruitment of neuro-muscular motor units, and synchronization of motor units.
Rate coding – relates to the control of the firing rate (average number of action potentials) of neuro-muscular motor units. Resistance training is known to lead to increase the firing rate which in turn increases the strength of a muscular contraction.
Recruitment of neuro-muscular motor units – when muscles work against a resistance they recruit motor units to overcome the resistance. The greater the number of neuro-muscular units recruited during a task the greater the force that is applied. Untrained individuals have a limited ability to activate muscle fibres. However, the number of motor units recruited can be increased through specific training such as maximum load training or plyometric training. A strength training program aims to increase the amount of neuro-muscular units recruited during physical activity. It also aims to allow muscle fibre groups to alternate, so when one muscle fibre group exhausts, another is still able to contract.
Synchronization of motor units – motor unit synchronization is the near simultaneous discharge of action potentials in pairs of motor units with similar recruitment thresholds. Increased synchronization of motor units enhances the ability to recruit muscle fibres at the exact time required leading to improvements in both efficiency and the force generated.
Strength training has been shown to lead to improvements in all aspects of intra-muscular coordination including an increased firing rate, greater recruitment of motor units, greater synchronization of motor units. Taken together these adaptations can lead to significant improvements in strength and power production.
Inter-muscular coordination relates to the interaction between muscle groups (agonists, antagonists, stabilizers, fixator and neutralizers) whilst performing a specific task or activity - the greater the level of co-ordination between different muscle groups the better. Strength training leads to improved synchronization between various muscles groups during an activity. This can be easily understood when considering the bicep curl. Although the biceps provide the main force (Agonist or prime mover) for the movement - assisted by the brachiallis - there must be co-ordination with the triceps muscle (Antagonist) which must be relaxed to allow proper lifting of the dumbbell. In addition the trapezius and rhomboids (Fixators – stabilisers that eliminate unwanted movement generate by the agonist) contract isometrically to reduce movement of the scapula (shoulder blade). Finally, the pronator teres prevents the supination action caused by the biceps brachii during elbow flexion – the teres is a neutraliser that acts as an antagonistic synergist opposing the unwanted movement of the agonist.
A low level of inter-muscular co-ordination will therefore adversely affect performance. This becomes increasingly important with more co-ordinated movements such as sprinting and is why elite sprinters will concentrate on relaxation techniques to relax the non-working muscles and thus allow the working muscles to function to their maximum potential.