How long do you have to devote to elongation or stretching? Ideally, when a person finishes a gym routine spend 10 minutes elongating each of the muscle groups that were worked. 30 How to elongate? To do it correctly you should stretch by holding the tension for 10 to 15 seconds three times, but without bouncing. It is best to stretch as each muscle group is worked out, for example, if the triceps are used, the triceps are elongated, and then another exercise.