Acting involves many physical activities, including performing stunts and fighting, which call for physical fitness. Imagine if Jackie Chan, with all his stunts, was not physically fit. Probably, he would not be able to perform those life-threatening stunts, and he wouldn’t be as successful as he is today. Now, being physically fit is key to becoming a successful actor. Just as vocal training is important for your voice, body fitness is just as important to your movement during acting. As an actor, you need to move and turn with ease, you need to throw punches and kicks, you need to perform stunts, and so on. As such, you must spend time in the gym, working on your physicality.
Physical fitness increases your presence on the state. Look at Arnold Schwarzenegger, for instance. His physique alone will speak a lot to any audience even before he makes a move or utters a world. Being physically fit will prevent you from injuries when acting, and it will make you a competent performer. Now you don’t have to be like Arnold or an Olympic athlete, because you may not get there after all. The most important thing is to tune your body to the physical elements of the theatre- it has to be ready for anything that is thrown at it, be it dancing, fighting, or running.
One important tip to keep your body fit is to work out regularly. Physical fitness is not a one-day event that will last forever. Rather, it is built and maintained over time. Ask any great actor and they will tell you that they hit the gym almost on a daily basis.