"PIR" Post-Isometric Relaxation technique
PIR (post-isometric relaxation) is a stretching technique that utilizes both active and passive stretching.
First, stretch the muscle, lengthening it to determine end feel. This is your base line of comparison for subsequent stretching.
Secondly, relax for 10 seconds followed by a 30% stretch of the muscle. This position is held as you hold your breath and contract the muscle against resistance at 20-30% full-strength.
Repeat the second step for a total of 3-5 repetitions, with the goal of increasing the end range with each repetition. Discomfort is expected, pain is not - be mindful of your pain tolerance and bodily signals when perform stretches.