Many of the old Shaw Bros. martial arts films play off the mystique of the wise old master. Sure, the star of the film is half his age, ripped and gets the girl, but the master can beat the student with just his pinky. The message here is that martial wisdom trumps youth. Even if the student is in his 50s, he can still pursue a rewarding martial practice.
Choose Wisely, Grasshopper
The best martial art for someone over 50 could depend on the style. Most styles are divided into striking and grappling. Striking arts such as Muy Thai and Savat employ kicks and punches. Grappling arts like judo involve submissions, throws, and pins. Pick one. There are styles like Mixed Martial Arts that mix the two, but those tend to call for a long recovery time. They aren't designed with older adults in mind.
Brazilian JuJitsu For Grappling
A large chunk of BJJ is spent sparring at an aerobic 50 percent intensity so you can refine technically complex passes and submissions. There are fewer high impact moves than in other grappling arts, which translates to less wear and tear on the body. There are throwing techniques, but many schools focus on ground work. More importantly, BJJ develops grip strength and hip mobility which deteriorate with age and disuse after age 50.
Everybody Wing Chun Tonight
While Chinese Kung Fu is replete with ornate forms like the Shaolin Five Animal Style, Wing Chun is austere and direct. Most strikes are open handed (as supposed to a closed fist) and focus on speed not raw power. It's ideal for people over 50 who may not have the brute strength of their younger days.
Take Care of Your Body
Martial Arts can improve strength, cardio, and mobility. However, over-training can have disastrous effects, particularly for those over 50. Give yourself plenty of time to recover between hard training sessions. Regardless of style, divide your time between contact sparring and drilling techniques. If you fall in love with a style you'll be tempted to take classes five days a week. For the first two months, limit yourself to two to three days of training.