The shift to colder weather makes hibernating under a pile of blankets — perhaps while binge-watching favorite shows — quite tempting. But outdoor exercise is a great way to improve energy levels, boost the immune system, connect with nature and, during the coronavirus pandemic, safely socialize with people outside your bubble.

Indeed, the protracted health crisis is motivating many people to get off the couch and get out in the brisk air: Sales of outdoor winter sports equipment as a result have been spiking. From August through October, sales of backcountry ski gear and accessories grew 76 percent compared with the same period in 2019, according to the NPD Group.

But an outdoor exercise routine during the winter does bring unique risks. Cold temperatures cause blood vessels to narrow, making it harder for the heart to pump blood and potentially straining the heart. This narrowing of blood vessels can also keep muscles from getting the oxygen they need to stay warm and flexible, which can lead to injury. Hypothermia, frostbite and falls on icy ground are also hazards of winter weather.

A little planning and preparation can mitigate the risk whether you’re going for a winter walk, trekking in snowshoes or sledding with the children. Here’s what you need to know to feel the burn and the “brrr.”

Before you head out

FUEL UP The body has two main types of adipose tissue or fat — white and brown. Unlike standard white fat, which stores calories, brown fat is packed with energy-creating mitochondria that produces heat and helps the body maintain its core temperature when it’s cold out. This is the type of fat hibernating animals use to stay warm.

“Essential fatty acids like omega-3s, DHA and EPA can help increase the amount of brown fat,” said Shawn Stevenson, the nutritionist and author of the book “Eat Smarter.” “You’ll find that in salmon, roe, egg yolks and algae or krill oil. There’s no need to go crazy, but two to three servings a week can help during the cold time of year.”

DRINK UP Cold temperatures cause physiological shifts that diminish the body’s thirst response and increase water loss through respiration — when you see your breath, water is leaving your body and evaporating — and urination (yes, you really do urinate more in the winter).

“Staying hydrated isn’t as intuitive as it is during the summer, when sweat is pouring off you,” said Sophie Caldwell Hamilton, a cross-country skier and two-time Olympian. “For me it starts first thing in the morning. For every cup of coffee I have, I have a cup of water. When I’m skiing, I have a drink belt with warm water and a Nuun electrolyte tablet in it.”

GEAR UP Dress dry, not just warm. Water moves heat away from the body, leaving you cold and increasing your risk for hypothermia (when your core body temperature falls below 95 degrees).

When you are heading out, start with a base layer made of merino wool, polypropylene or material that will wick away water and sweat. This includes glove liners, socks and hats, which can get wet with sweat and freeze. Next, add a slightly thicker layer made of fleece or light wool and top it off with something that breaks the wind. Sunglasses or goggles and a buff, neckwear that can be pulled up over the mouth and nose, help protect the face. There’s a wide variety of winter boot options so be sure to check the temperature rating and traction.

“I buy hand and toe warmers in bulk and keep them in my pockets,” said Dr. Katie Eichten, a cross-country skier and emergency physician at the Hayward Area Memorial Hospital in Wisconsin. “I also put one against the back of my phone and put both in a middle-layer pocket so the battery lasts longer.”

If you’re heading into the mountains, your phone can be a particularly powerful tool. Dustin Dyer, an owner and director of Kent Mountain Adventure Center, suggests downloading a navigation app like Avenza Maps, Powder Project or Trailforks, that includes offline digital maps and uses your phone’s built-in GPS to locate you even when you’re out of range.

SAFETY FIRST Depending on your winter outdoor activity, you may want to consider specialized safety training.

Mr. Dyer, who guides backcountry skiers, snowboarders and ice climbers, recommends CPR training for everybody.

“If you’re going to be one hour from care, doing multiple days outside or really going off the grid, you should have Wilderness First Aid,” he said of the certification course. “And everyone who is going into the mountains in the winter needs some kind of avalanche training. For most people, avalanche awareness, which focuses on avoidance, is going to be adequate.”

While outside

WARM UP (AND COOL DOWN) When exercising in cold temperatures, your muscles are not as pliable and are at increased risk for injury and strain. The cold air also causes the upper airway to narrow making it harder to breathe. Breathing through the nose and covering the nose and mouth with a scarf or mask can warm the air before it reaches the lower airway. But both the muscles and the lungs need to warm up for at least 10 to 15 minutes.

Dr. Eichten, who has also completed over 10 Birkies, a 50-kilometer cross-country race formally known as the American Birkebeiner, suggests moving at a slower pace of whatever activity you are planning to do and then adding in some dynamic stretches like arm circles, lunges and hip circles.

“You also need to let your breathing slow down before you go back into the warm air,” Dr. Eicthen said. “Your lungs need to adjust to a normal breathing rate or you can induce a cough or spasm.”

KEEP UP It’s important to stay on top of your fuel, hydration and clothing while you’re out.

If you’re going to be active for more than 45 minutes, think about how you can fuel your body along the way. Dr. Eichten suggests a simple carbohydrate like a granola bar or an electrolyte drink.

You can also easily lose one to two liters of water while out, so bring water with you, be conscious of your activity level and take water breaks.

Be sure to adjust your clothing as necessary.

“You want to stay warm, but you don’t want to get too sweaty,” Ms. Hamilton said. “As the intensity ratchets up, I take off layers and then add them back on as I start to cool down.”

Back inside

CHANGE “Even if you don’t feel sweaty, the first thing you need to do is take off the layers that were next to your skin,” Dr. Eichten said. “You can get cold quickly. Your muscles will tighten because they’re trying to get warm.”

A warm shower helps soothe muscle fatigue while the steam opens up the airways.

STRETCH The cold weather and vasodilation of blood vessels causes more tightness in the muscles, which have to work harder than in milder weather. This can increase soreness and affect range of motion. Self-massage and stretching can encourage muscle recovery by improving blood flow and reducing inflammation.

ROLL OUT Jill Miller, the author of “The Roll Model,” uses two rubber massage balls to slowly roll out big muscle groups like the quadriceps as well as any areas that have been immobilized by boots or skates. This stimulates the tissue, increases circulation and adds to the feeling of warmth.