To find an answer to this, we need to understand what happens to our body when we exercise? Fitness experts advise to warm up before you start exercising to prevent muscle damage before strenuous activities (like weight lifting). Once you start exercising, your heart rate and BP increase, temperature rises and you begin to sweat and once you stop exercising all these come back to normal, this process is called homeostasis. By exercising, you are burning calories, improving circulation, losing water and electrolytes. Now comes the question of bathing after exercise, I feel it depends on several factors like the type of exercise - strenuous or non-strenuous, duration of exercise, season, the actual condition of your body, where are you exercising - gym or park. Warm water bath leads to vasodilation (opening/widening of blood vessels) which increases blood circulation and therefore releases all the lactic acid and toxins into the blood, this is advisable if you are doing a cardio (walking, jogging, cycling) just to improve circulation and burn calories. A cold water bath is advisable when you are doing strenuous activities (lifting weights, football, marathons, kickboxing) as the muscle undergo stress and once you stop exercising, the repair of the muscles begin. Therefore, cold water bath will help counter the inflammation of muscles caused by strenuous exercise.