GI Joes and GI Janes unite in this "do it or else" style of training fashioned after the army and navy boot-camp regimens.

Boot camp is a fast-paced, military-style interval-training class that incorporates calisthenics like the ones you did in the fifth grade. Classes include jumping jacks, pushups, running in place, football-style drills and lots of yelling. If you've always wanted your own personal drill sergeant, you'll love these classes.

The sessions are efficient because they incorporate a wide range of exercises at high intensity. You’ll strengthen your muscles and bones in addition to getting an excellent cardio workout.

If you have enough self-discipline, you can design your own boot camp for free by taking advantage of fitness trails and “par courses” that many municipal parks offer. Better yet, invite a few friends along to keep each other motivated.

• Tons of repetitions will tone muscles, and the fast-paced drills will keep your heart pumping.
  
  
• Though there is a lot of repetition, the wide range of activities and quick tempo stave off boredom.
  
  
• The result: a serious workout and great calorie burner.
  
  
• For those who need a push to get moving, boot camp should do the trick.
  
  
• For advanced exercisers who are tired of the same old routine, this could shake things up.

• Boot camp is not advisable for beginners or anyone who’s nursing and injury.
  
  
• The risk of injury is high, especially because many of the moves are quick, ballistic and super intense.
  
  
• Not all boot camp instructors are certified, well trained or safe.
  
  
• Do you really want to relive fifth-grade gym class, perhaps with a dash of “Full Metal Jacket” tossed in for good measure?