On average, professional boxers take ice baths for almost 20 minutes. Some boxers recommend an hour-long session whereas some try to finish things up in as low as 5 minutes. The real challenge is that initial shock to your nervous system when you dip your body in cold ice. But, from the second minute, your muscles start getting numb and it will become much easier. Just keep in mind, as a boxer, you're not taking ice baths to break the world record. Get start with a smaller duration that you're comfortable with and work your way up.