Good news, busy people: 15 minutes is enough time for an effective workout.

If you haven't already seen the infamously hilarious Shake Weight commercials (check it out below), or seen celebrities like Ellen DeGeneres and Queen Latifah poking fun at the weight-lifting product, we'll clue you in. The Shake Weight for women is an "As Seen on TV" 2.5-pound dumbbell-like product with spring-action that supposedly targets your biceps, triceps, shoulders and chest, and claims you'll only need to work out six minutes a day to get the full muscle-toning benefits.

The men's commercial, seemingly aimed at wannabe bodybuilders, asks, "Would you like to get your arms ripped? Your shoulders pumped and your chest sculpted ... Do you hate working out for hours at the gym with big, bulky equipment, or boring, slow dumbbells?"

The Shake Weight for women commercial, meanwhile, is aimed at fans of Michelle Obama's arms. "Work out your entire upper body in just six minutes a day," the ad touts. "You'll get arms you'll be proud to show off. Feel free to go sleeveless."

The commercials go on to explain these claims are possible because of "dynamic inertia." The manufacturers assert that if men use the Shake Weight for just one minute it's equivalent to doing 240 repetitions of regular weight-lifting. For women, the commercial explains, "Scientific studies at a prestigious University prove that the Shake Weight increases upper-body muscle activity by 300 percent compared to traditional weights." All that for a price tag of $19.95 (plus shipping) for the ladies' version or $29.95 (plus shipping) for guys.

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Overwhelmed by all of the "Follow Friday" recommendations on Twitter? Each week AOL Health's Twitter alias Healthpop and That's_Fit search the Twittersphere for the greatest diet and fitness Twitterers, and each week, we'll highlight the best-of their best tweets (no Twits here). Got any great advice for our Fit Follow Friday post? Give us a shout on Twitter and let us know all about it!

Most people tend to assume that the best time to work out is early in the morning. But as any busy person will know, exercising in the early hours isn't always possible. Over at CafeMom, they're talking about exercising in the evening -- because a workout in the evening is still a workout, and it's better than no workout at all. Plus, a gentle workout like Pilates can help you unwind before bed.

And, as it happens, the evening is actually a great time to exercise. So tell us, when do you work out? Are you an AM exerciser or do you wait until the evening to get your fitness routine in?

Keep track of the latest in diet and fitness Twitter trends and opinions with this weekly post. Not only will AOL Health's Twitter alias Healthpop and That's_Fit ask fitness-related questions and share the best responses with you, we'll scour the Twittersphere for the latest buzz on everything from good eats to exercise routines gone bad.

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Hitting the gym, getting your workout on, or sweating it out are all great in theory. But while our minds and fitness conscience tell us to head for the nearest treadmill, the little devil on our shoulders may have something less strenuous in mind. We turned to Twitter to find out your favorite ditch-the-gym excuses.

A kettlebell workout is done with a kettlebell or traditional Russian weight used for strength training. The kettlebell, typically made from cast iron, can weigh as little as 10 pounds or more than 100 pounds and looks like a large cannonball with a handle on top. Called "one of the most effective means of strength development" by the Soviet armed forces, kettlebell workouts have been popular in Russia for decades and have recently caught on in the U.S.

There are numerous benefits from kettlebell workouts. Training with kettelbells builds strength without adding bulk by allowing users to develop lean muscles. Kettlebell workouts also increase explosive power, agility and stamina. Those who want to outfit their home gym without too much expense often turn to kettlebells, too. Just one or two kettlebells can replace tons of other equipment like weights, barbells, dumbbells and cardio machines.

Kettlebell workouts are effective for toning the entire body because multiple muscle groups are engaged throughout each exercise. These workouts can be customized to different fitness levels, but beginners should work with an experienced instructor to make sure they are using correct form. Like any other piece of exercise equipment, kettlebells that are used incorrectly can cause injuries.

Basic kettlebell moves include the swing, high pull, snatch, overhead press and Turkish get-up. Classic kettlebells can be purchased online and range in price from $47 to $218 each.

When you're ready to begin using kettlebells, you can pull together your own kettlebell workout.

Like a hefty helping of tomatoes with your meal? Then you're in luck. A new study from the UK's Reading University shows that tomatoes may help control hunger.

If you thought BPA was only hiding in your plastic, here's a health update: the December 2009 issue of Consumer Reports tells us BPA is in a variety of name-brand canned food items including Progresso Vegetable Soup and Campbell's Condensed Chicken Soup.

Now for a light-hearted link we love: 10 workout videos to get you LOLing at your desk, if not well, exercising. Hey, laughter burns calories too.

Keep track of the latest in diet and fitness Twitter trends and opinions with this weekly post. Not only will AOL Health's Twitter alias Healthpop and That's_Fit ask fitness-related questions and share the best responses with you, we'll scour the Twittersphere for the latest buzz on everything from good eats to exercise routines gone bad.

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Hauling your cookies to the gym is tough enough without the added stress of irritating workout habits from other gym-goers. From awkward staring to uncleaned exercise equipment, see what gym and workout pet peeves drive the fine folks on Twitter a little bonkers.

Regular exercise is a vital part of a healthy lifestyle, but is there such a thing as over-exercising? You bet -- and according to Sarah Brown, fitness expert for ThatsFit.ca, it's more common than you think. What's more, it can be harmful to your health.

If you think you might be guilty of over-exercising, ask yourself a few important questions. Do you seem to spend most of your free time at the gym? Have your sleep patterns changed? Do you seem to be more susceptible to illness than others? Do you suffer from more aches and pains than usual? If the answers to most of these are a yes, it could be your body's way of telling you to slow down.

Instead of working out more, work out better with tips from this celeb trainer.

Keep track of the latest in diet and fitness Twitter trends and opinions with this weekly post. Not only will AOL Health's Twitter alias Healthpop and That's_Fit ask fitness-related questions and share the best responses with you, we'll scour the Twittersphere for the latest buzz on everything from good eats to exercise routines gone bad.

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Hopping on the treadmill and sweating it out on the elliptical are things of the past for many of Twitter's fittest tweeters. They've put traditional workouts on the back burner and are trying something new. Check out which exercise waters they've tested.

When you move your arms in virtually any direction, your shoulders (a.k.a. deltoids) are either in charge or, at the very least, involved. The ingenious design of your shoulder joints makes the shoulders one of the most mobile, versatile muscle groups in your body. It also makes it one of the most vulnerable. Fortunately, if you commit to doing some basic shoulder training on a regular basis you'll keep your "delts" strong and supple and have a better chance of staying injury-free. It'll help balance out your body's curves too. Want to slim your hips? Chiseled shoulders broaden the upper body and polish your posture, creating the illusion that you've shrunk and reshaped your hips. Plus, firmed up shoulders look killer in tank tops. To get your shoulders in shape, try exercises.

Click through the photo gallery below for our step-by-step workout guide.




Ideally, you should own three sets of dumbbells for shoulder work; typically 3, 5 and 8-pounders. When you first try the accompanying shoulder routine, start with your lightest weight. Do 1 set of each move, 8 to 15 sets per set, 2 to 3 times a week. Once you can easily complete 15 reps of an exercise, move up to the next heaviest weight or try the "challenge yourself" version. Rest assured that going heavier won't bulk you up -- we promise. On the contrary, it'll help you shape, tone and strengthen your shoulder muscles a lot quicker than sticking with a weight that's too light to have an impact.

Mistakes to avoid: Don't arch your back as you lift and keep the movement in control so you don't rock back and forth to help lift and lower the weight. To avoid shoulder and neck pain, don't clench your teeth, hitch your shoulders up, or drop your chin to your chest. Keep these technique pointers in mind and you'll create a beautiful pair of shoulders with minimal risk of doing any damage. (If you tend to have chronic shoulder pain, consult with your doctor or physical therapist before you do these moves.)

Shoulders benefit from a bit of variety so change up your routine every month or so by doing 1 to 2 workouts with exercise bands or by tossing in a set or two on the shoulder press machine at the gym. Yoga is surprisingly good at toning and redesigning shoulders because so many upper body poses depend on them to move and support the entire body. Swimming, especially the crawl stroke, is also a good shoulder shaper.

If your weight, health and overall quality of life weren't reason enough to get active on a regular basis, here's another one that might get you off the couch: Working out can help you fight the flu this winter season. Well, that's according to a study on mice anyway. Researchers from Iowa State University have found that mice who regularly run on a treadmill experience flu symptoms that are far less severe than the symptoms suffered by their lazier counterparts. Even mice who only started exercising right before the flu had less severe symptoms, though the ones who were regular gym-rats (pardon the pun) had longer-lasting positive effects -- meaning their symptoms were diminished throughout the course of their illness, not just in the first few days.

The findings, published in the Journal of Infectious Diseases, suggest that exercise can really boost the immune system, and while it's not clear whether the results can be applied to humans as well, researchers are optimistic. And besides, it's already the general consensus that regular, moderate exercise helps improve your odds against illness.

Still, don't overdo it -- you can get too much of a good thing. According to Jeffrey A. Woods, a professor of kinesiology and community health at the University of Illinois, prolonged and intense exercise sessions can lead "to increased susceptibility to viral infection." His advice on navigating flu season? "I would recommend everyone get the annual influenza vaccination and the new H1N1 vaccination," he tells The New York Times.

The flu isn't the only thing that exercise is good for -- cardio is more effective than heart surgery.

CrossFit is a multi-faceted approach to fitness that promotes overall functional physical fitness through variable strength and conditioning exercises. CrossFit workouts are performed in a group setting, can be done in 15 to 20 minutes and involve full-body exercised based largely on functional movements such as lifting, pushing, pulling, swinging, jumping and running. The goal is to create a well-rounded athlete by conditioning a number of physical abilities, including strength, speed, coordination, agility, balance and stamina.

CrossFit was developed by Greg Glassman in the 1980s and has been adopted as the workout of choice for thousands across North America, including police officers, military personnel and professional athletes. CrossFit's legion of dedicated followers pledge allegiance to the the program because of its varied nature, meaning that, unlike some typical gym routines, the workout is never boring. CrossFit workouts can be done by people of all ages and fitness abilities.

Ready for a challenge? Try this Crossfit exercise.

P90X is a workout plan designed by trainer Tony Horton which aims to help users get in shape in 90 days. According to the creators, P90X uses "an advanced training technique called Muscle Confusion, which accelerates the results process by constantly introducing new moves and routines so your body never plateaus."

P90X is a set of DVDs which include 12 different workouts that focus on a specific muscle group or set of exercises. In addition to workouts, the P90X comes with a three-phase nutrition plan. Phase 1 is the Fat Shredder, a high-protein diet; phase 2 is the Energy Booster, a mix of carbohydrates and proteins with a lower amount of fat; and Phase 3 is the Endurance Maximizer, a diet of complex carbohydrates, lean proteins and lower fat, which includes more carbohydrates than the previous phases. There is also a "How to Bring It" DVD that provides a quick overview of P90X, a calendar to track your progress, online peer support and more.

Want to learn more? Discover why Sheryl Crow Loves P90X and read That's Fit Blogger Karla Carrington's review of P90X.