Fitness warriors eager to step out of the gym at the first sign of spring should exercise caution, fitness experts say, noting that hitting the open road is more taxing than running on a treadmill, and mountain trails are bumpier than a spinning class.
Even conditioned people may need a period of adjustment to transition safely into working out in the open air.
"The harsher the winter, the more we have to be careful not to come back too fast, too soon," said exercise physiologist and running coach Tom Holland, who lives in Connecticut. "Even people who are generally fit might do less over the winter."
When the weather changes, Holland said, many runners try to run too many miles too soon.
"The body generally takes about two weeks to acclimate," he explained, "so give yourself time to build back that base of strength."
He recommends that regardless of what was done outdoors last fall, a little less should be done in the spring.
"Running on a treadmill is generally easier than outdoor running, so if you've been running five miles on a treadmill don't increase (outdoor) mileage immediately," he said.
And cross-training should not be neglected.
"Just because the weather gets nice, doesn't mean we eschew the gym," he said. "Strength training is a big part of being injury-free."
Chris McGrath, senior fitness consultant for the American Council on Exercise said too many people doing their winter cardio on a treadmill assume they can transition seamlessly to running on the ground.
Pavement is harder than the belt of a treadmill and the mechanics of running are slightly different.
"Most treadmills have some bounce," he explained. "On a treadmill the belt is essentially kicking your foot back. You're not pulling yourself along the ground as much as when you're running on a street."
McGrath said shin splints are a common, minor injury of runners unable to absorb the impact of running on pavement. Whether running, biking or walking, moving outdoors changes things.
"If you've been taking spin classes and then go to a hilly area, it's going to be different" he said. "Heart and lungs and muscles still have to make an adjustment."
As motivating as warmer weather can be, he said, exercisers inconsistent in winter are not conditioned to leap full throttle into a high-level warm- weather workout.
Fitness and wellness coach Shirley Archer, who travels regularly between Switzerland and Florida, said transitioning from cold to warm weather is easier than the other way around.
"In cold weather muscles are colder, the body loses heat more easily, old injuries are more noticeably stiff and the cardiovascular system is more stressed," she said.
When transitioning to a new workout environment, she advises, it's better to rely more on feelings of perceived exertion than to follow a particular pre-set training pace or time.
"Listen to your body. If you're uncomfortable or straining, ease up," she said.
Training outdoors in natural light, changing scenery and varied terrain, tends to be more engaging and mentally stimulating than training indoors, said Gregory Chertok, a sports psychology consultant with the American College of Sports Medicine.
"The mind is constantly seeking variety," Chertok said. "On a treadmill, flat is guaranteed but outdoors you have to watch for potholes, puddles and obstacles."
He said such outdoor challenges can also improve balance and proprioception, the awareness of the position of one's body in space.
Holland believes variety is the key to injury prevention. In fair weather or foul, he said, we tend to stick to what we're good at, and that can lead to problems.
"If you're a runner, bike. If you're a biker, run," Holland advises. "Ideally we want to be exercising in August, not sidelined by injury in June."