Seasonal cycles

Unless you deliver mail, you're not likely to venture out in the rain, snow, or sleet. If you instinctively feel that warm temperatures and sunshine seem to naturally encourage you to be more active, while cold and darkness dampen your enthusiasm to move, research findings published in a recent issue of the American Journal of Epidemiology confirm that you are not alone! Activity patterns apparently change with the seasons.

Almost 650 healthy adults from central Massachusetts were enrolled in the 12-month study. Each volunteer's weight, diet, sunlight exposure, and physical activity was assessed at regular intervals. Participants reported the amount of time they spent daily in each of three activities defined as household, occupational, and leisure. Then they reported the intensity level of each activity as light, moderate, vigorous, or very vigorous. The scientists also recorded fairly detailed information about weather patterns during the study year.

Warmth and sunshine related to higher activity levels

Not surprisingly, the volunteers were most active in the warm, summer month of July. This pattern was strongest in men over age 60. The other participants did not have as dramatic a swing in activity levels. Also, long-time exercisers or those who participated in a sport tended to maintain higher physical activity levels for longer into the winter months, while those new to the exercise habit (less than 12 months) dropped off as winter approached.

These peaks in activity coincided with longer hours of daylight, fewer clouds, and warmer temperatures. Interestingly, snowfall in January correlated with spikes in activity for men. The suspected reason? Snow-shoveling, which, by the way, does count as a form of daily exercise.

These findings may not sound like "news." Many people are well aware that they alter their routines according to the calendar and weather. But these latest findings may help explain other research showing seasonal variation in blood lipid levels, blood pressure, body fat, bone density, and depression.

Forecast calls for increased activity

Numerous health organizations, including the American Heart Association, the American Cancer Society, and the U.S. Surgeon General. recommend some type of physical activity for at least 30 minutes on most--and preferably all--days the week. The challenge is to find ways to maintain high levels of physical activity in good weather and in bad.

Admittedly, it is tough to exercise during the cold, dark, winter months. Be prepared with other options on those days when facing the elements is too much. Walking in the mall, up and down stairs, or even vacuuming and brisk housecleaning can contribute to fitness. As this study indicates, the more active you are, the more likely you are to stay that way year-round.