By Deborah Kotz, Globe Staff

No question, most of us sit way too much, and that's not good for our health. Too much sitting could raise our risk of heart disease as well as decrease our muscle mass, balance and level of physical fitness.

That could explain why a January study found that those sat the most during the day were more likely to have larger waists, higher cholesterol levels, and higher levels of dangerous inflammation -- all risk factors for heart disease -- compared to those who sat the least.

This week's challenge is all about getting up for mini-breaks -- once every 45 minutes or so. Get up and stroll your office corridors. Pace or march in place while you speak on the phone. Do some stretches, sit-ups, or push-ups in front of the TV. To help you remember, set an alarm on your watch or download this computer app.

By Elizabeth Comeau, Boston.com Staff

Last week, I asked you how you find the time to stay fit. Many of you responded by saying that you just have to do it -- make fitness a daily habit. So, you're making the time for exercise, which is awesome. Now I want to know what, exactly, you do?

The people in the video above are practicing "green" fitness. They do things like exercise circuits at local parks. Getting outside is great (in good weather) but what do you do every day?

Do you hit the pavement for a daily run? Are you a die-hard gym-goer? Tell us your secrets for staying in shape. Don't forget, you can always send us photos of your success, too!

By Elizabeth Comeau, Boston.com Staff

Wouldn't it be nice to have a personal trainer at your disposal at all times? I know personally, I'd love to have a trainer and a chef just take up residence in my home. However, since I can't afford that, being able to ask a personal trainer my fitness questions today at noon will suffice. FULL ENTRY

John Tlumacki /Globe Staff

Marathon runners had the finish line in sight as they made their way down the final yards on Boylston Street.

By Elizabeth Comeau, Boston.com Staff

Yesterday all eyes were turned to the streets of Boston, where runners from across the world showed their athleticism and strength by completing a 26.2 mile run. While it was amazing and inspiring to watch, it kind of made me feel like a slouch.

I didn't run 26.2 miles yesterday... did you? Did you exercise at all?

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By Deborah Kotz, Globe Staff

With Marathon Monday almost upon us, running is definitely on the mind. At the moment, I'm gazing out at the gorgeous spring weather bemoaning that I haven't yet gotten out for a jog.

Those who aren't runners might assume that running is an easy way to take extra pounds off without worrying about what they eat. But many runners, including the author of a new book, "Run Your Butt Off! ," find it difficult, if not impossible, to lose weight through running alone.

Full disclosure: I put on six pounds while training for the marathon several years ago and, yes, it was mostly fat, not muscle.

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It's a week before Marathon Monday. Have you started training yet? Sure it's totally too late for this year's 'thon, but how about 2012? Okay, perhaps the marathon isn't for you, but it's definitely a good idea to keep challenging yourself when you exercise. Pick up the pace a bit when you stroll. Or try doing a minute or two of jogging for every five minutes that you walk briskly. If you're already a runner, try sprinting for 30 seconds for every mile you run.

That's the challenge for this week: to pick up your pace. Pushing yourself beyond your normal comfort level can increase your endurance and improve your lung capacity -- both of which can improve the overall functioning of your body. If you bike, pedal faster; swim, kick harder; dance, choose a faster beat.

For those in Boston who wonder why reality shows rarely hit their town -- we're all still waiting for the Masshole spin-off of the Jersey Shore -- well, here's a chance to star in one. If you're a certified personal trainer or a high school senior looking to shed some serious weight, MTV wants you...to come to an open casting call.

Personal trainers, MTV says, must be"highly" credentialed and dynamic (i.e. professional acting skills are a plus). And, yes, those who've worked with overweight teens are preferred. I'm guessing teens who are cast must be willing to dive into drama and controversy as well as a hard-core exercise regimen.

The casting call will be held this Saturday, April 9, at the Westgate Mall in Brockton, Mass. from noon to 3 p.m. Those who can't make it can email a resume, short bio, and recent photos to bostonhsweightloss@gmail.com or check out this video for more information.

By Deborah Kotz

In this age of obesity where every child is encouraged to move as much as possible, parents sometimes forget about the risks faced by student athletes at the other end of the spectrum. Two research findings out this week highlight the dangers of hidden life-threatening heart problems in college athletes and the risk of stress fractures in high school girls who participate in high-impact sports.

The first study, published yesterday in the journal Circulation, found that the incidence of sudden cardiac death among National Collegiate Athletic Association (NCAA) student-athletes was 1 in 43,770 participants per year -- pretty tiny -- but that rate jumped to 1 in 3,100 for NCAA Division 1 basketball players.

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By Deborah Kotz, Globe Staff

What triggers a heart attack? Let me count the theories. A new study by Boston researchers, published Tuesday in the Journal of the American Medical Association, blames the occasional roll in the hay or bout of exercise -- for those who don't, ahem, build up a sweat very often. And let's not forget previous research, which found higher heart attack rates in cities on the days following a home team loss in the Super Bowl or other studies that linked heart attacks to too much traffic or air pollution.

While I do see the need for such studies -- given that 30 percent of heart attack patients had no known previous risk factors -- I'm beginning to wonder what good they do the individual. The latest finding didn't find that sex or exercise were huge contributors to heart attacks in this country and certainly didn't increase risks to the point that we should curtail these activities in any way.  FULL ENTRY

By Deborah Kotz

I loved the study this week that found that dog owners who walked their dogs were 34 percent more likely to get the 150 minutes of recommended exercise they need each week than those who didn't own a dog. Emphasis here on walking your dog; it's not enough to just own one.

I was also struck by a Boston University School of Medicine study published yesterday, which found that African-American women who live in urban areas -- like Manhattan -- where it's easier to walk than drive gain less weight over time than those who live in more sprawling areas -- like Los Angeles -- that require a car to get from place to place.

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