The EMG is a recording of: The action potential of the motor nerves supplying the muscle fibers. The contraction forces of the innervated muscle fibers. The action potentials of the innervated muscle fibers.

The correct answer is option B.  The contraction forces of the innervated muscle fibers.

Explanation:

Electromyography or EMG is the study of muscle activity with the help of analyzing electric signals that are burst or generated by the contraction of the muscle fibers. In other words, it is the electrical activity of the skeletal muscles in response to a nerve's stimulation of the muscle.

EMG uses the myoelectric signals to analyze muscle that is generated during the contraction forces of the inverted muscle fibers of the skeletal muscle.

Thus, the correct answer is option B.  The contraction forces of the innervated muscle fibers.