Combat sports are full body sports so your fight training should involve your FULL BODY. You train your shoulders, arms and legs, but equally important is your core - your chest, waist, hips, and portions of your back. Most workouts concentrate on either upper or lower body, but just like a city needs to have a thriving midtown, you need a powerful midsection - because this is where the serious business happens!
Think of your core as the foundation for every element of fighting. The core provides balance, moves and stabilizes your midsection, powers your punches and absorbs punishment from an opponent. As the saying goes, if you want to be hardcore, you must develop a hard core.