1) A meta-analysis of nine studies revealed that cold-water immersion is more effective at reducing muscle soreness than passive recovery (where you exercise at a low intensity to flush out exercise-induced toxins). The therapy is said to constrict blood vessels, helping to reduce swelling and tissue breakdown. Prof Aryane Machado and his team also concluded that water temperature between 11°C and 15°C is optimum for 11-15mins. But be warned: some say reducing soreness is a sign the muscle isn’t adapting effectively to the workout.