As muscle fibers become fatigued and produce less force, additional motor units are recruited to maintain a constant muscle force and flexor joint torque to maintain the isometric position. As a result, the EMG magnitude increases as the muscle fatigues.
Does EMG increase with force?
The recruitment pattern with maximal voluntary contraction is called “interference pattern” because of the increasing degree of superimposition of action potentials from different units. With increasing force, the EMG becomes continuously denser and the maximal peaks in the signal have a higher amplitude.
Why does EMG amplitude increase when load increases?
EMG amplitude increases because there are more muscle fibers firing action potentials simultaneously, and each fiber contributes some force, in order to generate a total force equal to the load. At the maximum load, the EMG amplitude will be at its maximum as well.
What is the apparent relationship between EMG activity and muscle force?
The amount of force a muscle produces when electrically activated by EMG depends on the current (and previous) state of that muscle. The force a muscle produces depends on its length, velocity of movement, and frequency.
What increases EMG amplitude?
In conclusion, motor-unit synchronization increased the amplitude of the average rectified EMG and decreased the steadiness of the force exerted by the muscle in simulated contractions.
What would increase the force generated by a muscle?
As the stimulus frequency is increased, the force is increased until the maximum is reached, at which point it begins to decrease. An increase in the level of circulating epinephrine and norepinephrine from the sympathetic nervous system also increases the force of contraction.