Muscle coactivation

[1] This occurs through a motor neuron sending a signal (through creating action potentials) to the muscle fiber to contract by releasing acetylcholine.

In the upper limbs, the stability of muscle coactivation allows for precise low-level physical tasks.

By protecting the muscles at the end of their range of motion, the direction of the fine movements is able to be changed.

The coactivation of different muscle groups allows for proper balance and the ability to adjust weight and to stay upright on uneven ground.

[1] Muscle coactivation is absolutely necessary for learning a fine motor skill or for any activity involving stability.

[10] An EMG of coactivation would display the agonist and antagonist muscle contracting simultaneously.