Set cool down length after exercise.
Cool down length scales with both how long and how hard the session was, plus how far heart rate still has to fall. Roughly three fifths of the time should be easy movement that keeps blood circulating, with the remainder spent stretching once the heart rate has come down. The target heart rate is the practical cue for when the easy phase has done its job.
Cool down duration
Cool down minutes = workout minutes x intensity factor + (end heart rate - resting heart rate)/20, clamped to 3-25 minutes
These figures are estimates based on population-average formulas and are intended for training and recreational planning only. They are not medical advice. Consult a qualified health professional before starting or changing an exercise programme, particularly if you have an existing medical condition.
Five to ten minutes after most sessions, longer after hard intervals or long endurance work. The higher your heart rate at the finish, the more time it needs to come down gradually.
Move easily first. Stretching is more comfortable and effective once heart rate has dropped and breathing has settled.
Evidence for preventing next-day soreness is weak. The clearer benefits are avoiding post-exercise dizziness and easing the transition back to rest.