Winter weather conditions in many parts of the United States can pose a number of significant challenges to outdoor activity and exercise. As a health and exercise professional, you know that wintertime environmental conditions place considerable stress on the cardiovascular, respiratory and thermoregulatory systems. For instance, the incidence of heart attacks is highest during cold winter months, and prolonged exposure to cold, dry air can cause significant injury to the airway. And, thanks to snowy and icy conditions, the risk of outdoor falls is much greater during the winter months, especially for older adults. Clearly, it is essential that you help your clients take extra precautions while participating in outdoor activities and exercise. This article outlines seven strategies for helping your clients perform outdoor wintertime activities safely and effectively.

1. Understand the physiological challenges related to exercising in the cold.

The major problems encountered when exercising in the cold are associated with an excessive loss of body heat, which can result in hypothermia and/or frostbite. When the skin or blood temperature drops, the thermoregulatory center activates mechanisms that conserve body heat and increase heat production. The body avoids excessive heat loss in three primary ways:

• Peripheral vasoconstriction is the narrowing of the arterioles (due to sympathetic stimulation), which reduces the blood flow to the extremities and skin, thus decreasing the amount of body heat lost to the environment.
• When altering skin blood flow is not enough to prevent heat loss, nonshivering thermogenesis is increased. This involves stimulation of the metabolism (as directed by the sympathetic nervous system) to increase internal heat production.
• Shivering is the next bodily process that occurs if peripheral vasoconstriction and nonshivering thermogenesis are not enough to prevent heat loss. Shivering is a rapid, involuntary cycle of contraction and relaxation of skeletal muscles, which can increase the body’s rate of heat production by four to five times.

The effects of cold air are, of course, compounded by wind. As wind increases, so do convective heat loss and the rate of body cooling. An index based on the cooling effect of wind is windchill, which refers to the cooling power of the environment (Table 1). As windchill increases, so does the risk of freezing body tissues. The risk of frostbite is less than 5% when the temperature is above 5° F (-15° C). However, increased vigilance for outdoor exercise is required when the windchill factor falls below -8° F (-22° C), as exposed skin is susceptible to frostbite in less than 30 minutes.

Table 1. Windchill Factor Chart

After an exercise session, chilling can occur quickly if the body surface is wet with sweat and heat loss continues. There are documented cases of runners who ran in a cold environment, got sweaty, slowed from fatigue and developed clinical hypothermia due to increased heat losses from sweat and air movement coupled with decreased heat production from a reduced exercise intensity.

2. Understand the long-terms effects of cold air exposure. 

Cold air is always dry, and endurance exercise triggers a loss of both water and heat from the lower respiratory tract. Air must be warmed to body temperature and brought to 100% relative humidity before entering the alveoli. This process, known as conditioning, is done by the respiratory tract, beginning with the nose and mouth. By the time air reaches the trachea, it has been warmed to body temperature. This is important, as it helps prevent reductions in core body temperature. At the same time, air is moistened to 100% humidity before reaching the alveoli.  This prevents the cell lining of the passageway from drying out.

The burden of the lower respiratory tract to condition the air is much greater for wintertime activities than it is for summertime activities. The colder and drier the atmospheric air, the harder the respiratory tract has to work to warm and humidify this air. Prolonged and repeated exposure to cold, dry air can induce significant injury to the airway and cause exercise-induced bronchoconstriction (EIB) and asthma. Here are several preventative measures you can share with your clients to limit these possibilities:    

• Although there is not a specific temperature threshold of cold air that leads to airway injury, urge your clients to consider indoor alternatives when the temperature drops below 5° F (-15° C).
• Both the duration and intensity of exercise can play a critical role in the risk of airway damage due to inhalation of cold air. As such, encourage clients to avoid combinations of prolonged and vigorous-intensity exercise during cold weather conditions. Vigorous-intensity exercise for short durations and moderate-intensity exercise for prolonged durations are generally tolerable.    
• Another option for alleviating airway injury risk when vigorously exercising in cold air (i.e., <5° F or <-15° C) and/or for prolonged durations is to wear a breathing mask. Research has shown that wearing a heat- and moisture-exchanging breathing device can help healthy individuals manage their airway responses to high-intensity exercise in sub-zero temperatures.

3. Mitigate the risk of cardiac events, which are most common during the winter months. 

The incidence of heart attacks is highest during cold winter months. Indeed, colder temperatures and major snowfalls are often followed by an increased number of heart attacks, especially among men. The cold can cause a generalized vasoconstriction that can increase peripheral resistance and blood pressure. This may cause problems in people who have hypertension or who have heart disease.

Snow shoveling is a widespread wintertime activity for millions of Americans. Interestingly, previous research has shown that snow shoveling can elicit increases in heart rate and blood pressure similar to those experienced during a maximal exercise test. Collectively, the high metabolic demands of snow shoveling, coupled with the previously mentioned physiological responses to cold, mean you offer your clients guidance on how to best lower their risk while performing this common wintertime activity. Here are several strategies worth considering:

• Given the high-intensity nature of snow shoveling, a 5- to 10-minute warm-up inside before getting started will lessen the overall strain on the cardiovascular system.
• Use a smaller shovel so that the weight of snow being lifted each time is lighter than if they were to use a large shovel. This can help ensure lower blood pressure responses. Encourage your clients to practice proper breathing so they avoid performing the Valsalva maneuver, which can also drive up blood pressure responses.
• If the temperature is below approximately 5° F (-15° C), encourage clients to wear a face covering while snow shoveling. Cold air inhalation can cause vasoconstriction of the coronary arteries and a mismatch between myocardial blood supply and demand.

4. Emphasize balance training during the winter months to reduce fall risk. 

The risk of falling outdoors is greater during winter when snowy and icy conditions are present, especially for older adults. In fact, more fall-related emergency department visits and fractures occur in the winter months than during any other season. Various factors, including slips or trips on ice, snow or freezing rain, contribute to this higher risk for falls. As a result, many older adults become less active during the wintertime months because of fear of falling outdoors. However, decreased activity and time spent indoors can actually lead to an even greater risk for falls, as inactivity leads to diminished muscle strength and reaction time.

During all seasons, and especially during the wintertime months, balance-training programs for older adult clients should focus on improving functional and progressive tasks of daily living. The overall aim of a balance-training program is to improve gait and balance deficits and reduce the fear of falling, which can be accomplished through a range of activities, including dual- and multitask exercises such as spelling words while doing balance exercises or standing core exercises. More balance-training exercises and progressions for older adults are presented in Table 2.

Table 2. Balance Training Exercises and Progressions for Older Adults

Note: The number of repetitions per exercise and rest intervals are dependent on each client’s conditioning and functional status.

5. Use the talk test to monitor exercise intensity during outdoor activities.

Walking or running in snow that is either packed or powdered significantly increases the energy cost and the body’s physiological responses. Therefore, your clients will have to adjust their usual pace to match the intensity they can achieve during milder weather. The talk test is a great way for clients to monitor their exercise intensity and is a practical way to identify ventilatory thresholds, which is part of the overall ACE Integrated Fitness Training^® (ACE IFT^®) Model.

Start by paying close attention to your client’s ability to talk while they are exercising. As their exercise intensity increases, talking will become more difficult as they near the first ventilatory threshold.  Eventually, talking will become very uncomfortable the closer they get to the second ventilatory threshold. Beyond the second ventilatory threshold, they will have great difficulty talking. This simple-to-administer test is an accurate and practical option to monitor intensity, and is particularly helpful during the winter when intensity levels may need to be adjusted.

6. Choose the right clothing and footwear for cold weather exercise. 

Here are some helpful clothing and footwear tips to share with your clients before they head out to exercise in a cold environment:

• Wear several layers of clothing so garments can be removed or replaced, as needed. As exercise intensity increases, remove outer garments. Then, during periods of rest, warm-up, cool-down or lower-intensity exercise, put them back on. A head covering is also important, because considerable body heat radiates from the head.
• Sweating during heavy exercise can soak inner garments. If evaporation does not readily occur, the wet garments can continue to drain the body of heat during rest periods, when retaining body heat is especially important. If wind is present, it may be better for your clients to start the session by heading into the wind and finish with the wind at their back. If the opposite happens, they can become quite sweaty at the start of their session and potentially experience greater heat losses at the end of their workout due to their wet clothing.
• Select garment materials that allow the body to give off body heat during exercise and retain body heat during inactive periods. Cotton is a good choice for exercising in the heat because it readily soaks up sweat and allows evaporation. For those same reasons, however, cotton is a poor choice for exercising in the cold. Wool is a better choice for cold-weather exercise because it helps the wearer maintain body heat even when it gets wet. Newer synthetic materials (e.g., polypropylene) are also excellent choices, as they wick sweat away from the body, thereby preventing heat loss. When windchill is a problem, nylon materials are good for outerwear. Synthetic materials such as Gore-Tex, although much more expensive than nylon, are probably the best choice for outerwear because they can block the wind, are waterproof and allow moisture to move away from the body.
• Choose slip-resistant footwear, which has been shown to help reduce the risk of slips and falls in simulated winter environments by as much as 60 to 80%.

7. Practice good nutrition and hydration for cold weather environments. 

It is beyond your scope of practice as a health and exercise professional to provide specific nutrition recommendations to your clients. However, offering sound educational resources and information can help them make informed decisions and improve their exercise performance. In the case of exercising in the cold, adequate nutrition and hydration can enhance your client’s tolerance to cold conditions.

Prolonged exercise depletes muscle carbohydrate stores and blood glucose levels. In cold weather environments, this depletion is accelerated because the body burns more carbohydrates to fuel shivering, which, in turn, leads to diminished exercise performance and fatigue. However, a more problematic consequence of not having enough carbohydrate available is a reduced ability to shiver. A decline in shivering limits heat production and, as a result, increases the chances for hypothermia.

Therefore, proper nutrition in the form of carbohydrate ingestion before and during exercise is essential for safe and enjoyable prolonged exercise in cold weather environments:   

• One to four hours prior to exercise, consume 1 to 4 grams of carbohydrate per kg of body weight.
• During exercise, consume 30 to 60 grams of carbohydrate per hour.

Evidence-based hydration practices are critical to replace body fluids in the cold, just as in the heat. Large amounts of water are lost from the body during normal respiration, and this effect is even greater during exercise. Because sweat losses in cold weather may not be as obvious as they are during exercise in the heat, monitoring body weight over several days is recommended. You can find more information on hydration recommendations for before, during and after exercise here.

Final Thoughts

During the winter months, many of your clients might be tempted to become less physically active because of frigid outdoor conditions. However, it is possible to minimize the discomfort and risk of exercising in the cold. Applying the research-based strategies outlined in this article can help keep your clients exercising safely and effectively throughout the winter months.

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