There are many martial arts forms you can practice, depending on what's offered in your community. For people wanting a bit more self-defense in their workout, Jeet Kun Do, Silat, or any style of boxing (American, Thai, Filipino, or Kick) will suffice.
For people who want a rigorous workout sans the learning how to severely hurt someone, Taekwondo is an excellent choice.
In my opinion, of all martial artists, people who practice Taekwondo are in the best shape physically.
Taekwondo is a Korean martial art form and the national sport of South Korea. It was originally established for the Korean military, but today, it is the world's most popular martial art form in terms of the number of practitioners.
Taekwondo combines combat techniques with sport, exercise, and in some cases, meditation. There are two forms of Taekwondo: Traditional and Sport.
Traditional Taekwondo is typically referred to as the original military form established in the 1950s and 60s.
Sport Taekwondo has evolved over the decades and focuses more on competition and sparring, though if you practice the sport form you don't have to compete. Tournaments are simply an option for anyone who's interested.
Primarily, Taekwondo focuses on kicking and jumping, which requires you to use your core. The kicking exercises alone will have your legs burning within a few seconds. If you keep doing it you'll see your thighs and ass tighten before your eyes. By the time you reach the "Jumping 360 Round House," your lower body will be rock solid.
Taekwondo has a heavy focus on core training with exercises like Burpees, box jumps, and jumping lunges as well as a focus on upper body development with push-ups, pull-ups, and shrimp crawls.
There are form sets in Taekwondo that require an enormous amount of discipline and concentration. With form sets, you simulate fighting maneuvers, but in a more artistic and sport-like arena as opposed to practical application like with other martial arts forms.
Taekwondo is ranked on a belt system and separated into "junior" and "senior" or "student" and "instructor" levels.
The junior level has 10 ranks (geup) that are referred to as the "color belts." The range of colors differ for each Dojang.
Typically students start out at tenth geup (or white belt) and work their way to first geup (often a red belt with a black stripe).
The senior level has nine ranks (dan) that are referred to as the black belts or degrees. Practitioners in the senior level start out at first-degree black belt (or first dan) and move up.
To move up a belt level in Taekwondo you have to complete a series of tests, each one building on the other. To move up you must master a variety of kicking and basic exercises, as well as the more complex form sets. There's also a board breaking requirement, and in certain Dojang's a boxing element.
Taekwondo, and martial arts for that matter, is not cheap. You must pay the Dojang a fee each month (differs among Dojangs), plus there is a fee attached to each test.
On average it takes someone almost four years to earn first dan.
Some Dojangs will rush the process with a kind of "pay for your degree" business model. At good Dojangs, however, practitioners will invest a lot of time and energy earning a black belt but will be much better trained and in better shape than they would if they had gone to a "Buy A Belt" type establishment.
Finding a good Dojang can be difficult, especially if you're in small-town America. If you do have limited selection for martial arts studios in your town, you may have to take the good with the bad because, in the end, a solid Taekwondo workout produces results.
If you live in Oklahoma City, Grand Master Reeder's Martial Arts Center, 7926 N. May Ave (across from 7-Eleven), is a great place to study. Grand Master Reeder is knowledgable, dedicated to the health benefits of martial arts, reasonably-priced, has an array of classes and class times, and isn't a radical freak who's preparing kids for a militia take-over.
If you're interested in getting in shape with an intense cardio and core workout, but don't want to spend hours every day in the gym, try Taekwondo. It's painful, repetitive, exhausting, intense, hard, and guaranteed to produce visible results in just a few weeks, which is always fun.