Does it really matter if my personal trainer is certified? I just want someone buff to get me through the workout. – Karen Astor, Kingston, New York

There are many reasons to hire a personal trainer. Maybe you haven't done anything physical since you climbed the ropes in elementary school gym class, or you have a specific goal in mind like running a marathon or finally dropping those excess pounds once and for all. I suppose wanting to stare at an Adonis or Athena for an hour isn't the worst reason in the world to plunk down $50-$100 an hour, provided it comes with the added benefit of raising your fitness level. Just make sure you hire someone qualified.

Problem is, plenty of gorgeous and maybe not-so-gorgeous trainers out there don't know the difference between a push up a push up bra. They don't even bother to demonstrate the minimum qualifications and knowledge to ensure a safe and effective workout. And believe me -- a bad trainer can turn what should be a fun and positive experience into a nightmare -- or at the very least, waste your time without bringing you any closer to achieving your fitness goals.

Is it true that three minutes of jumping rope is equivalent to 15 minutes of jogging? - Samantha Janes, New York City

I've gotten this question a lot over the years and I don't know where it comes from. The short answer is no, this is not true.

While both have the potential of being good cardio workouts, most people can't jump rope continuously for more than a few minutes. Jumping rope definitely works more muscles than jogging but the trade off is that it's even higher impact than running -- which itself is a fairly high impact activity. Skipping rope burns about 10 calories per minute whereas a moderately paced jog burns about 13. You can churn up as many as 18 calories per minute jumping rope but few people have the skill or stamina to last very long at that intensity.

Fans of The Biggest Loser may have noticed an exotic addition to the show recently: The 2010 StreetStrider.

Like a cross between an elongated tricycle, a Razor scooter and a gym elliptical trainer, the StreetStider consists of a light frame with two small wheels in front and one large wheel in back. Riders stand on the ski-like platforms and stride their legs in a stretched out oval motion. The movement is part jogging, part cycling -- and part something completely new for an outdoor exercise machine.

If the Biggest Loser contestants are any indication, StreetStriding will be the next big fitness craze. They tested the machine behind the scenes for over two seasons, zipping around obstacle courses and pumping up hills. Although contestants had usually lost a good deal of weight before climbing aboard, most of them were still on the heftier side so Dave Kraus, the inventor and president of StreetStrider International, thinks their feedback was especially useful in helping in working out the kinks and perfecting the motion for the average person.

"We're really hoping to re-energize people of all shapes and sizes by providing them with a cutting edge product that's safe, rigorous and low impact," he says.

Rowing machine in the gym – waste of time or a good way to get in shape? Sandra Kearney – Texas

Nothing is a waste of time if you put in the effort and practice good form. The rowing machine is no exception. At the gym, I like a rowing machine that consists of a flywheel, fan, and cable with a handle attached to one end. You pull the handle toward you as you slide the seat backwards. The fan creates air resistance, which makes the movement feel pretty close to skimming across the water. If your gym has one of those rickety hydraulic powered row-thingies it's time to ask yourself why you belong to that gym.

When you're trying to get in shape for a rowing or paddling sport, you'll love working out on a quality rowing simulator. Even if you never plan to hit the water, you may learn to love rowing for its ability to combine upper body, lower body and cardio conditioning all in one package, something few other cardio workouts can do. Contrary to popular myth, rowing isn't bad for your back. If you do it correctly, you initiate the movement from your legs and buttocks; this eliminates excess stress on your back muscles.

I don't have time to do a cardio and a weight workout. Which one should I give up? – Kathleen Boyd, Stanford, Conn.

There are two myths we can bust here. The first: You have to spend hours a day to get in shape and lose weight. The second: You have to separate your strength training routine from your cardio routine. A type of workout known as circuit training allows you to work your heart and muscles at the same time while burning calories at warp-factor speed.

In a circuit training routine, you jump from one exercise to the next with no or just a few seconds rest in between sets. It's the perfect routine for people who are time-challenged or want to juice up their current exercise routines. Though circuit training won't pack as much of a cardio punch as true aerobic activities like walking and jogging, or as much muscle shaping as slow and steady traditional weight training, doing two to three circuits a week will result in moderate strength gains and good cardiovascular benefits. A 20-minute, high-intensity circuit will burn off upwards of 250 calories, which is comparable to running an eight-minute mile. That's a great overall fitness package.

Liz Neporent is a diet and fitness expert and co-author of "The Fat-Free Truth."She regularly appears on national TV programs and is the president of Wellness 360, a New-York based wellness provider. You can also follow her on Twitter @lizzyfit.

I recently developed these lovely little pockets of fat on the sides of my breasts. Please tell me what to do about this "Bra Overhang" -- or is it something I just have to learn to live with? – Rachel Ross, New York City.

Fortunately, this is one fitness problem that can be largely solved with a trip to a good department store. This "bra overhang," as you so cleverly call it, is often the result of wearing a bra past its freshness date. Stretched-out elastic, thread-bear fabric and poor fit do your silhouette no favors. I think it's time for new bras, and when you shop, it's a good idea to check in with an experienced lingerie salesperson who can help you with proper fit, style and comfort.

While you're at it, you should also make sure your sports bras are up to speed. During exercise, your breasts need good support to prevent the Cooper's ligaments that hold them up from stretching out. Over time, this may cause your breasts to look droopy and saggy. Once stretched, ligaments do not snap back into place, so it's important to be very protective of them. You have two types of sports bras to choose from.

Liz Neporent is a diet and fitness expert and co-author of "The Fat-Free Truth."She regularly appears on national TV programs and is the president of Wellness 360, a New-York based wellness provider. You can also follow her on Twitter @lizzyfit.

Can't I just get on a treadmill and start running? Is having a goal for my workout program really important? Yvette Carpenter, New York City

Normally, goal setting is a topic I tackle during New Year's resolution season, but since I just got a question about whether or not goals are really that important if you want to lose weight or do something meaningful with your fitness program, I figured this is as good a time as any to remind you how important it is to have real, tangible goals for your fitness program. As Edwin Locke, the father of modern goal-setting theory once pointed out, "Telling someone to 'Try hard' or 'Do your best' is less effective than telling them to 'Try to get more than 80 percent correct.'"

If you are serious about getting results from your workouts, diet or any other aspect of your fitness plan, go through my 10-step goal-setting guide. Is it too much to ask when you're trying to squeeze the most out of your efforts? Me thinks not.

Liz Neporent is a diet and fitness expert and co-author of "The Fat-Free Truth." She regularly appears on national TV programs and is the president of Wellness 360, a New-York based wellness provider. You can also follow her on Twitter @lizzyfit.

I just had a baby. Is it true I can kiss my flat stomach goodbye forever? – Barbara Carlson, Kingston, N.Y.

If you think your baby bump instantly deflates the moment your bundle of joy pops out, then you need a wake-up call, which is ironic considering how little sleep you'll get after having a baby. You can get your pre-pregnancy belly back, but it takes some hard work, patience and dedication. Even those Hollywood starlets like mom-of-twins Rebecca Romijn, who seem to snap back into shape so quickly, need at least a couple of months to tighten and tone the tummy.

For the best advice on postpartum abs, I turned to Tracey Mallett, author of the new book "Super Fit Mama." She offers these three must-do moves for every new mom, as well as some basic tips on the best ways to work your post-baby middle safely and effectively. Mallet, who has had two children, says these exercises aren't necessarily the belly-crunching gut busters you used to do before you got pregnant, because your aim is to restore any abdominal muscle separation that has occurred during pregnancy and labor, and to re-educate your entire core. (If you want to know more about Mallet's workouts and programs, surf on over to her website.)

Liz Neporent is a diet and fitness expert and co-author of "The Fat-Free Truth." She regularly appears on national TV programs and is the president of Wellness 360, a New-York based wellness provider. You can also follow her on Twitter @lizzyfit.

Photo: Getty Images

I've heard that walking or running hills is a better workout than always staying on the flat -- fit or fiction? Margie Burger, Boston, Mass.

Does the thought of struggling up a hill during your workout make you want to run the other way? Perhaps you're suffering from hillophophia, a common disorder that makes you quake with fear every time your feet meet with an incline. If you are so afflicted, relax. The secret to running and walking up hills is not to let them get the upper hand.

The thing to keep in mind is that hills are not the enemy. Treat them as an opportunity to improve your fitness level and pick up the pace on calorie burn. For every additional 5 percent of grade (a modest uptick in the landscape), a 150-pound exerciser will burn an extra three to five calories per minute.

Liz Neporent is a diet and fitness expert and co-author of "The Fat-Free Truth." She regularly appears on national TV programs and is the president of Wellness 360, a New-York based wellness provider. You can also follow her on Twitter @lizzyfit.

Photo: Getty Images

Have you ever seen that OK Go! Video, Here it Goes Again, where four guys do an amazingly-choreographed dance routine skipping between eight treadmills? Very entertaining. Am I the only one, or was it just a matter of time before someone came up with the bright idea to turn this thing into a workout?

The other day my friend and top fitness pro Terri Walsh sent me a link to Tracy Anderson's treadmill dancing video exercise routine. Anderson is the latest Hollywood "it" trainer. As Walsh puts it, "Fitness gurus come, and fitness gurus go, but one who trains Madonna and Gwyneth Paltrow, our patron saints of enlightened blonde fabulousness -- must be the guru-iest of them all no? THEY think she's got something, so she must be good, right?"

Liz Neporent is a diet and fitness expert and co-author of "The Fat-Free Truth." She regularly appears on national TV programs and is the president of Wellness 360, a New-York based wellness provider. You can also follow her on Twitter @lizzyfit.

Photo: zmtomako, Flickr

Will switching from soft drinks to energy drinks help me lose weight?

I know plenty of people who guzzle soft drinks and plenty of people who don't like drinking water. They are constantly looking for a tasty alternative to help them quench their thirst. So, are energy drinks the answer?

Perhaps. If you're a soda addict, each 8-ounce can you knock back without giving it a second thought will set you back about 100 to 120 empty calories. There is no calorie savings with some of the newer energy drinks, like Red Bull, plus they pack crazy amounts of caffeine and may not be great for your teeth. The same amount of the classic sugary energy drinks like Gatorade deliver just 50 calories. True, that's just half the damage of soda and may contain a few essential vitamins and minerals, but it's still a fairly significant slug of calories. Plus, who drinks just 8 ounces of anything, especially when you're parched? As a recent Columbia University study shows, most people easily chug their way through nearly 250 extra calories a day. Researchers at the Johns Hopkins Bloomberg School of Public Health also found that liquid calories had a stronger impact on weight loss than calories from solid foods.

Liz Neporent is a diet and fitness expert and co-author of "The Fat-Free Truth." She regularly appears on national TV programs and is the president of Wellness 360, a New-York based wellness provider. You can also follow her on Twitter @lizzyfit.

Photo: mikebaird, Flickr

My knees are shot. Does that mean that running is out of the question? - Robyn Smith, NYC

Running is one of the best calorie burners of all time. It burns between 8 to 20 calories per minute depending on your weight, how fast you're going and your fitness level. Unfortunately, it's also pretty tough on your body. Between 30 and 50 percent of runners are injured every year and up to 50 percent of those injuries are centered around the knees.

So there are a lot of runners out there sidelined by mushy hinge joints wishing they could hear the crunch of leaves beneath their feet and fill their lungs with crisp autumn oxygen. Some will be able to work within the boundaries of bad knees and other joint pain by adjusting the workout. One way to do this is by mixing running and walking intervals together to get just enough of a speed fix and just enough of a break to side-step the aches and pains many runners experience.

Liz Neporent is a diet and fitness expert and co-author of "The Fat Free Truth". She regularly appears on national TV programs and is the president of Wellness 360, a New-York based wellness provider. You can also follow her on Twitter @lizzyfit.

Photo: lululemon athletica, Flickr

Can I get any benefit from doing just a few minutes of exercise or am I just wasting my time?

There is a common misconception that you have to be an exercise fiend to get anything out of a fitness program. Most professional groups, the American Council on Exercise included, recommend doing at least 30 minutes a day of moderate-to-vigorous activity to derive most of the cardio-protective effects of exercise and at least five, one-hour sessions per week if your aim is to lose or maintain weight. All true. But that said, a growing body of research shows you will get some benefit if you aim for as little as 10 minutes of physical activity a day and about the same benefit as a longer workout if you do several mini-workouts throughout the day. Let's refer to this workout approach as "exercise snacking."

I think physical activity can work something like diet: There are times you are able to sit down at the table and enjoy a leisurely meal, and then there are other times when all you can do is grab and go. When you don't have the time or inclination to do a full "meal" of exercise, try exercise snacking to accumulate activity throughout the day in the form of micro-movement sessions that last for 10 minutes or less. Research done at Harvard University shows these bite-sized portions of movement begin to tap into the health benefits of physical activity and chip away at weight issues, especially if your exercise program nibbles total at least 300 calories a day. (For a 150-pound person, that's the equivalent of walking three miles.)

Liz Neporent is a diet and fitness expert and author of "Walking for Dummies." She regularly appears on national TV programs and is the president of Wellness 360, a New-York based wellness provider. You can also follow her on Twitter @lizzyfit.

Photo: Photodisc

For all the magazine headlines touting the amazing fat-blasting powers of yoga, it's a relatively anemic calorie burner. A typical 45-minute class burns off fewer calories than a honey glazed doughnut, hold the sprinkles. Yet, yoga can help you lose weight, just not for the reasons you might think.

Researchers at the Fred Hutchinson Cancer Research Center recently quizzed 303 people about their activity and eating habits and then cross-referenced them to see which groups had the most insight into why they ate and what they ate. It turns out that the yoga devotees were more in tune with the social and emotional reasons they reached for a honey glazed than the average couch potato, and interestingly, even more so than the folks who walked into the same gym but headed for the treadmill, bike or weight room instead of the yoga studio.

Liz Neporent is a diet and fitness expert and author of 12 fitness bestsellers. She regularly appears on national TV programs and is the president of Wellness 360, a New-York based wellness provider. You can also follow her on Twitter @lizzyfit.

Photo: mikebaird, Flickr

While it's true that walking doesn't burn calories as quickly as jogging or Spinning classes or other high-intensity workouts, scores of studies have shown it to be a very effective weight-loss tool. For example, a study published in the Journal of the American Medical Association found that brisk walking is very effective for reducing deep abdominal fat, the most dangerous kind of fat. And a University of Colorado study found that if people could commit to walking 2,000 steps a day more than they do now -- the equivalent of about one additional mile or about 15 minutes worth of movement -- they may not necessarily lose weight but would probably stop gaining. The typical adult gains 1 to 3 pounds a year, which means they're eating, on average, an excess of 10 to 30 calories a day. The 100 calories per day burned off from walking 2,000 steps would more than compensate for this excess.

Researchers have also found that walking an additional 6,000 steps a day (or about 3 miles) is the point at which the pounds really start coming off, as long as it is done in conjunction with sensible eating habits like fat, calorie and portion control.