The more you practice punching, the stronger and more defined your arms will become. This increased strength and endurance will allow you to deliver punches faster and for a longer period of time. The more you practice kicking, the better your balance and greater the musculature of your legs will become, allowing you to have more control and stronger knockdown power. Your body's developmental emphasis is placed upon your most recent activities. But don't worry, you can overcome your body's propensity toward inactivity by teaching it new fitness habits.