If you wanted to apply a relaxation technique that works by intentionally increasing and then decreasing tension in the muscles, you would use

Correct Progressive relaxation

Progressive relaxation is a deep muscle relaxation technique use to control stress and anxiety, relieve insomnia and chronic pain. This technique works by intentionally increasing tension or tightening one muscle group as you breathe in and then decreasing or releasing the tension by breathing out.

Moreover, doctors uses progressive relaxation in combination with pharmaceutical treatment for the relief of high blood pressure, cancer pain and headache.