They feel they have to push hard to derive the benefits from exercise, and the reality is that they don't. That five months or so is needed to build new blood vessels, thicken bones and muscle tissue and trigger other physiological changes necessary to lose weight and build endurance and strength. For those who've just slacked off a little lately, six weeks might do it. The good news about planning such a long-term project is that the exercise becomes easier over time. Here's where a machine like your body beats one like your car, according to exercise physiologist David Petrie, who is chairman of the Health Sciences Department at Gettysburg College in Pennsylvania.
Progression allows the body to better adapt to stress from exercising.
Concentrate first on building duration and frequency, exercise authorities say. Boosting intensity should wait. If your goal is a 10K, you'll eventually want some of those sessions to reach 60 minutes, but Kulik recommends you lengthen workouts by no more than five minutes each week to get there. On off days, he suggests that new runners swim, cycle or take time off to rest. Troy Jacobson, who coaches endurance athletes in Baltimore, starts work with first-time marathoners five months before a race.