Adolescence and early adulthood are the times during life when there is a step decline in exercise. New research from Ohio State University has identified the factors that keep young people exercising. For women, family members who encourage physical activity will be the determining factor in maintaining an exercise program. The support of friends is more influential in keeping men engaged in sports or regular workouts.

Both groups are more active when they are provided with readily accessible and attractive opportunities for exercise.

"Deep winter may not always present the most salutary conditions for runners, but think of it this way: change is what keeps us fresh too. Go for a run, change your life. Sometimes it can work better in January than it does in June."

-from John Jerome's The Elements of Effort

3. Calorie Sources - fat, carbohydrates, protein.

We really are what we eat. The five basic nutrients (proteins, carbohydrates, fat, vitamins, and minerals) are necessary to sustain life. Each nutrient has an important role to play in our diet.

Proteins form the basic building blocks of muscle, bone, hair, blood, fingernails, antibodies, enzymes, hormones, and other body tissues.

Carbohydrates furnish the body with energy and give bulk to food. Fats nourish the skin, aid in the absorption of certain vitamins, help form cell membranes and hormones, help provide stamina, and serve to insulate the body from extreme temperature. Vitamins are needed to maintain a variety of vital functions in the body. Minerals are essential for various functions, such as formation of bones and teeth.

The Food Pyramid (developed by the Federal government) lists the recommended number of daily servings from each of the major food groups. Generally, daily calories should be divided according to the following percentages: 55 percent carbohydrate, 30 percent fats, and 15 percent protein.

In addition to gaining weight by eating excessive calories, a nutritionally poor diet can cause many other unhealthy conditions.

Approximately one-third of the cancer deaths and a large number of heart disease related deaths are linked to high-fat, high calorie foods.

“Instead of decreasing your average training speed as you get older, gradually increase the percentage of training miles that you run at 10-K race pace or faster. (Be careful to keep plenty of rest days in the mix, too.) The point is, jogging doesn't maintain "young legs." You must do high-quality work for that to occur.”

– Eileen Portz-Shovlin, Runners World senior editor

Extreme cold can cause a drop in body temperature or frostbite. In addition, the wind chill factor poses an additional threat. Both conditions can be extremely dangerous for the exerciser.

When the air is still, body heat warms the layer of air surrounding the body. This layer of warm air acts as an insulator, protecting the skin from the colder air. This makes the temperature seem warmer than it actually is. If you are moving, the insulating layer of warm air is no longer there. You feel colder. Adding wind to the temperature results in a wind chill factor or the amount of "coldness". It measures the amount of heat loss. For example, a wind chill factor of minus five indicates that the effects of wind and temperature on exposed flesh are the same as if the air temperature were five degrees below zero even though the actual temperature is much higher.