I've spent a lot of time on each one, and one common theme seems to be high-intensity and getting the most bang for your buck while you're working out. Another trend is using your own body weight to provide resistance for weight training.
What is it? It's an intense 60-day workout on DVD by the producers of P90X, Beachbody (beachbody.com). There's no equipment required; you use your own body weight for resistance. One of the keys is doing interval training at high intensity. From the producers: "Fitness expert and college track and field star Shaun T has taken traditional interval training and turned it upside down. Instead of long periods of moderate exercise with short bursts of intensity, you'll perform long periods at maximum intensity with short periods of rest. Each workout keeps you constantly challenged as you alternate between aerobic and anaerobic intervals performed at your MAX. The result: burn up to 1,000 calories in an hour and get the most insane body in 60 days."
Health Benefit: Burns lots of calories and gets you in great physical shape without joining a gym.
Health Consequences: If you're not ready for this, it could cause injury. Some of the reviews posted by users online indicate that people have been hurt. Also, I'm concerned about sticking with this program because it's so intense.
From one Amazon.com user: "I read many reviews before doing insanity about it being a high impact workout with repetitive jumping and motions that can cause deterioration in spinal discs. Oh how I regret not paying attention to that ahead of time. I'm 34 and was in good shape before I started insanity and have always been athletic. I've never had back pain before but now I'm stuck."
Here's another one: "I've been working out for over 20 years (I'm 35, 5'9", 155 lbs, male) lifting weights, running, swimming, cycling, hiking, skiing, and practicing yoga. I've never had any serious injury due to any of my exercises. However, I had to stop walking up and down stairs around week 5 of this program even with icing my knees after every workout. I finally decided to stop the workout completely when I could not do the moves during the workout without joint pain (not the "good" burning pain from working out)."
Bottom Line: I love the idea of using your own body weight to get in shape; however, it's too bad there isn't a beginner's version for those just starting to become "insane." You need to be in shape; it's not for the average person or those with special needs.
Unless you're in fantastic shape, it's probably best to try something else. (See: dietdetective.com/weekly-column/home-fitness-8-exercises-you-...)
What is it? A combination of weights, kettlebells, calisthenics, gymnastics and other fitness and exercise modalities a rapid pace, nonstop, timed, high-intensity workout. American Council on Exercise (ACE) describes CrossFit (crossfit.com) as "a form of functional training that utilizes constantly varied, high-intensity, functional movement patterns to improve efficiency in performing the activities of daily living (ADL)." CrossFit has WOD, Workout of the Day, which has developed a cult-like following. Additionally, CrossFit is now a competitive sport (games.crossfit.com).
Health Benefit: You can burn more calories than with traditional workouts. Women can burn 13 to 15 kcal per minute, and men can burn 15 to 18 kcal; by comparison traditional exercise burns 9 kcal per minute for women and about 11 kcal for men. "High-intensity, multi-joint movements comprise the bulk of CrossFit exercises, and the overall degree of stress placed upon the entire body will certainly promote systemic neuroendocrine adaptations to improve fitness and one's overall capacity to tolerate stress (assuming adequate fueling and recovery between sessions)," says a report by a fitness expert at ACE.
Health Consequences: According to CrossFit, the workouts will "wreck you." They are known to work you so hard that you could throw up or even, in some rare cases, develop rhabdomyolysis (where muscle breaks down, leaks into the blood and can compromise the kidneys). ACE's report states that, "Instructing individuals to complete as many repetitions as possible (AMRAP) using the same intensity creates an issue, regardless of intent. As fatigue builds, technique will suffer, so at what point do we draw the line in the sand and acknowledge that the risks outweigh the benefits? Asking individuals to know their own limits seldom works in a competitive environment." This loss of technique can create a recipe for injury.
Bottom Line: I really see the allure of CrossFit, but unless you're young, without injury and very athletic, you should probably try something simpler, like taking a long walk, doing yoga and strength training.