Genetic endowments aside, an elite endurance athlete and the average daily walker are, in their adaptations to exercise, different less in kind than in degree. "Adaptations to training take place along a continuum," says Jennifer Sacheck, a postdoctoral fellow at Harvard Medical School studying the biochemistry of activity and inactivity. The person who works out every day for an hour will show better adaptation to training stress than someone who exercises three times a week for 20 minutes.
But the elite are not only training more, they are careful and systematic about what they do. Many use heart-rate monitors to gauge the intensity of their workouts, so they can exercise at a percentage of their maximum heart rate (roughly, 220 minus one’s age). Most of their workouts, perhaps 80 percent of them during the course of a year, take place in what is called "zone 1," when the heart beats at roughly 70 to 75 percent of its maximum. This is an easy pace once initial training adaptations have occurred; the challenge of a zone-1 workout is said to lie in its length, which may range from one hour most days up to two to three hours once a week. An endurance athlete’s season will begin with months of this long, slow, distance training, thought specifically to increase capillarization of muscles and to enhance the mechanisms of aerobic energy metabolism. As the competitive season approaches, the athlete begins to introduce high-intensity intervals into the training, typically working up to two of these a week. For example, a series of four, four-minute intervals performed at 90 to 95 percent of the maximum heart rate (a challenging pace) might be performed with the goal of increasing the stroke volume of the heart. Always, the athlete is trying to stress the body, but to avoid injury, because the hard-won adaptations to training are all reversible, some in as little as a few weeks.
Resistance training is usually part of the athlete’s routine also, in order to build strength and avoid the loss of lean muscle mass over time. Most important of all, the elite athlete stays committed to training year round, with perhaps a few weeks or a month off each year to pursue other kinds of physical activity.
For the rest of us, lack of motivation can be a major obstacle to exercise and even people who want to exercise regularly can have difficulty incorporating activity into their busy daily lives. Doing something enjoyable, and making it part of a daily routine perhaps by walking or biking part of the way to and from work are proven strategies. Here are some additional things that Sacheck and JoAnn Manson, chief of preventive medicine at Brigham and Women’s Hospital in Boston, and a professor at Harvard’s public health and medical schools, have found can motivate the slothful, and keep them on track.