It was recommended to me many years ago to help me relax and sleep to start with my toes tighten the muscles and hold for 10 seconds then slowly let them relax Then keep going up your body with whatever muscle came next right up to your jaw. I did that for years and found it relaxing. I dont do it now for a few reasons or I do but skip body parts. I get cramps. LOL you need to concentrate on that muscle relaxing and focus on it staying relaxed as you move to the next group. Its a good way to releave your body of the tensions of the day.
I've never heard of it described like that... I meditate by focus breathing and clearing the mind. I will try the muscle tightening with it.