Jacqueline loved skiing–both downhill and cross country–ice skating and all manner of winter sport. During warm summer months, she made excuses not to exercise.

Her husband, Jake, was the opposite. During the hottest days of summer, he ran until sweat dripped off his exercise clothes. But when the chilly winds started to blow, he hibernated.

For all but the most committed, weather has a way of interfering with exercise schedules. The human body, on the other hand, does not benefit from seasonal holidays.

According to experts, cardiovascular fitness is lost at roughly half the rate it took to attain it. That means, if you spent 10 weeks getting yourself into tip top shape over the summer, you’ll lose all of it in about 20 weeks of winter inactivity.

And those who neglect their exercise schedule during the winter months face a double whammy since the period from Halloween to New Year’s Day is filled with temptations to consume extra calories.

For persons wanting to stay active year round, the ideal solution is to vary the activity with the season. A runner or cyclist, for example, might switch over to cross country skiing; a walker might buy a pair of snow shoes–thus avoiding boredom and bringing different muscles into play.

Whatever the activity, winter exercise can be exhilarating, offering a new environment and new challenges. A solitary run on a winter morning can be an almost transcendental experience. When you’re fighting the winter blues, try a noon workout–catching the warmest, sunniest part of the day.

Winter Exercise More Efficient

Don’t expect to follow the same pace that felt comfortable in October. Your workouts may be shorter and less intense but still more efficient. Studies have demonstrated that men and women who walked or cycled at a moderate pace in cold air used more calories and had greater weight loss than those exercising at the same intensity in warm air.

In addition to the extra calories needed to regulate body temperature and slog through snow, scientists postulate that a cold environment stimulates metabolism of fat.

If you’re properly dressed and moving constantly, you’ll be surprised at how quickly your body starts to generate heat. If the thermometer reads 35 degrees, you’re going to feel as if it’s 55 to 60, at least after the first half mile or so.

Dress in layers that you can peel off if you get too warm. Zippers are handy, allowing you to open up a layer or two to let air in.

The inner layer should be of a material such as polypropylene that wicks moisture away from your skin. The newer high-tech micro-fibers are very good at this, holding less than 1 percent of their weight in water compared to 17 percent for wool, 8 percent for cotton and 5 percent for silk. You’ll pay a premium for the best of these fabrics.

When the temperature dips below 35 degrees, you’ll need a middle layer that will hold in warmth and dry quickly. Fleece is a good, reasonably priced choice, and there are newer high-tech fabrics that are lighter and drier. These too come at a premium price.

The outer layer should protect against wind, rain and snow without locking in moisture. Gore-Tex is the premium choice, but a nylon blend with vent flaps may work as well for moderate conditions. Since they’re constantly on the move, your legs will stay warm with only a pair of spandex tights or wind-resistant pants. For very cold days, another layer in the groin area may be advised to protect the genitals against frost bite.

A warm hat and scarf are essential since 30 to 40 percent of heat from the body is lost through the head and neck.

For healthy, experienced athletes, hypothermia is rarely a danger, at least until the wind chill gets into negative territory. Try to plan your route so that you’re heading into the wind during the first part of your workout and have the wind at your back at the end when you’re fatigued and sweaty. If you venture into sparsely populated areas, make sure someone knows where you are and when you plan to return.

Wind chill combined with wetness increases the risk of frostbite but only if the temperature is below freezing. No matter how low the wind chill factor, you can’t get frost bite when the temperature is above 35 degrees. Tell tale signs include tingling, numbness and white discoloration, typically on the hands, ears, toes and face.

Warming up is particularly important in cold weather...and more easily neglected when you’re fighting off a shiver during the first mile or so. It’s a good idea to warm up at home–with a few minutes of jumping jacks or running in place–before venturing out the door. Cool down and stretching can also be completed in the warmth of your home.

When there’s snow and ice on the pavement, runners, cyclists and even walkers are at risk of injury by falling or sliding. If you’re worried about injury or simply don’t like to venture out in winter, there are numerous indoor alternatives.

Coming Indoors

Aerobics, Pilates and spinning all offer a change of pace from outdoor activities. Stair steppers can give an excellent cardiovascular workout; rowing machines and exercise bikes are good low-impact workout options.

If you don’t have a health club membership, many shopping malls welcome walkers during early morning hours. Or you can buy exercise equipment for your own home.

One study found that women with a treadmill in the home lost twice as much weight during winter as those without one. A treadmill workout is relatively low impact, and you can monitor your progress and design your own workout. One way to build cardiovascular fitness is to alternate several minutes of high intensity with a similar period of low intensity activity. Gradually, you can increase the length of the high-intensity segments.

With only a few hand weights, you can put together an effective strength training workout. And without any equipment at all, you can get a workout with pushups, sit-ups and stair exercises.

Whatever you do this winter, don’t neglect your workouts. Exercise will help you avoid that holiday weight gain, fight the winter blues and improve your metabolism so you feel better all day.