Obviously for general self defense or a cardio workout aspect it is really never too late to pick up any martial arts but in terms of Kickboxing/Muay Thai in an amateur fighting/serious training aspect is 21 to late? In all the bios of professional fighters I have read it seems that 90% of them started at 10/11/12, were punching each other in the head at an amateur level by 16 and by age 23/24 are professional fighters. Have I missed the boat? I began tkd at age 12 and was black belt by 16. Quit martial arts and have only recently (last 12 months) become interested in them (muay thai specifically) again at the age of 21. Have I missed the boat in terms of fighting in this sport? are those teenage years through to adulthood vital to the success of a kick boxer and their fight experience? or is it simply a case of having the physical and mental ability to dedicate yourself to the training?
