The main purpose of normalising EMGs is to allow comparison with those from other muscles and/or people:

Question

Quizplus · Accepted Answer

The amplitude of EMGs recorded from the same muscle on different occasions, or from different muscles and different individuals, cannot be compared directly; even if they have been processed using the same method. This problem can be solved by normalising EMGs after they have been processed by expressing the task-specfic EMGs as a percentage of the peak EMG values derived from a reference task (e.g. maximum voluntary contraction).

The Main Purpose of Normalising EMGs Is to Allow Comparison