Granted, downtown Boston is not the most natural setting with the freshest air supply, but exercising outside can provide an interesting alternative to the gym.,Now that spring is in the air, why not get outside and take it all in? If you are looking to jumpstart your exercise routine to shape up for summer, there are two options: either suck wind at the gym or breathe in the great outdoors.

Granted, downtown Boston is not the most natural setting with the freshest air supply, but exercising outside can provide an interesting alternative to the gym. After a long winter of reading muted TV captions and absorbing the sweatiness of the fitness center, a little space and sunlight could do the body good.

Emerson College Fitness Center (ECFC) exercise physiologist Stacey Schaedler encourages people to take a break from the gym and step outside.

“It’s just nice to have a change,” she said of the scenery switch.

Whether working out by the water, on city streets or around Boston Common, checking out the sights rather than staring at the TV can spice up any routine.

Besides, the sun only shines outside. Great weather is not just nice, it is also healthy.

According to Schaedler, sunlight provides the necessary skin-enriching vitamin D, and AOL Diet Fitness says the body soaks up the most oxygen outdoors. This triggers natural endorphins for a mental and physical boost.

While there are countless reasons to get outside, unfavorable weather ultimately keeps us in.

Advising people to keep an eye on the sky, Schaedler said she recommends wearing layers rather than under-dressing when exercising outdoors.

Even better, although also more expensive, is dry-fit or wick-away clothing that absorbs sweat to prevent chills, she said.

And if you are a fair-weather exerciser, then you should know that outdoor fun does not depend on the sun.

Allergy levels are lower on rainy days and muscles will work harder on windy days.

If the forecast predicts a scorcher, plan to avoid exercising in the mid-day heat, and, as always, slap on some sunscreen and drink lots of fluids to avoid overheating.

But what if you enjoy working out in front of the TV and actually like the treadmill? After all, the gym’s environment is both constant and convenient.

According to the article “Take it outside” from the University of Manitoba’s Web site, cardio machines may keep you warm and safe, but outdoor exercise is more challenging.

For instance, running on roads or trails generally burns more calories than on treadmill surfaces.

Thanks to wind and hills, Schaedler said outdoor running involves more impact while using treadmills at a flat incline does not simulate real terrain.

When opting for the treadmill, Schaedler advised people to get creative with their workout.

“Try to do intervals and change the incline,” she said. “Don’t do the same stagnant routine.”

In moving to the world outside the gym, Schaedler said to progressively work up to running several days a week.

“If you ran five days a week [in the fitness center], I would start off with two to three [days running outside] and see how it feels,” she said. Otherwise, injuries like shin splints and stress fractures could result.

As far as the best surfaces to run on, Schaedler said grass is low impact but also not as even as pavement. While running on grass is more challenging, she said cobblestone is probably the worst surface to run on.

Any rough and unpredictable terrain should be handled cautiously to avoid ankle injuries, she said. Although the city may seem limiting, the Boston area can be viewed as a recreational playground. With Boston Common and bike paths along the Charles River in Emerson’s backyard, one can run, bike, skip, jump and do whatever else outside.

Even with great weather, some are still skeptical about running anywhere else but on the trusty treadmill.

“People want to know how far they ran so they stick to the treadmill,” Schaedler said.

She recommended FavoriteRun.com to help outdoor exercisers map out the distance of their routes.

With the ifs, ands or buts about outdoor exercise covered, now is the time to take a breather from the gym and get outside.

And why not? Save the cardio machines for a not-so-hot day and take advantage of the sunny spring weather.

The treadmill will understand.