In fact, studies show that both aerobic exercise and functional fitness exercises help prevent daily hazards like falls and may help stave off dementia and Alzheimer's disease. "Independent living is a good motivator," says Karen Ross, a geriatrician at the University of Oklahoma Health Sciences Center. "I can talk to people all day about how their arthritis will be better if they exercise, but when I tell them they'll remain independent longer and improve their memory, that's a good carrot."

I HATE GOING IT ALONE

Some people work out to get away from it all, including other people. But for others, the idea of that much alone time, especially doing something they consider tedious, is totally unappealing. So exercise with someone else. Pairing up will make the time go by faster and up the odds of fulfilling the commitment. "You never want to be the person who leaves her friends on the corner at 5:30 a.m.," says Lindsey Spindle, 33. When she moved to a new neighborhood in suburban Maryland last summer, Spindle joined a group of women who had been running together for 20 years. Their weekly routine (four days of running, one of yoga) and consistency (they run in all weather except thunder- and ice storms) keeps her from flaking out, and the social aspect adds to her resolve. "We talk about family, jobs, about silly stuff," says Spindle. "It's hard to make and keep friends, and this is a creative way to stay fit and have a tight-knit group."

It also helps to find an exercise buddy with similar motivations and fitness level. That way no one gets frustrated by someone who can't keep up: Eleven-minute milers and 6-minute milers, for example, don't make the best running partners. If you can't find a group, taking a class with a core following or hiring a personal trainer can serve the same function. You're less likely to skip a session at the gym if someone's waiting for you, especially if you're paying for it.

IT'S SO BORING

The first key to workout dedication is to find an appealing exercise. "I fell in love with the act of running the very first time I went out," says John "the Penguin" Bingham, a columnist at Runner's World. (He gave himself the nickname after seeing a reflection of himself running and deciding he looked short and dumpy, like the bird.) "I still suck," says Bingham, "but I don't care. I'm having so much fun!" For Michael Bondanza, a jewelry designer in New York City, fun means boxing workouts. "I don't like going to a gym where I'm going to be on a machine," he says. "I have to be doing some kind of sport." Many people get off on the wrong foot by defining the best exercise as "whatever burns the most calories," like running hard, says Bryant. "Experiment with different activities until you find the things that float your boat."

Still, even a favorite class or cycling route can get tedious after a while. And as the body adapts, progress in things like weight loss and increased strength may diminish, which may also lead to burnout. To avoid both plateaus and boredom, shake up your routine every month or so. "If you're a runner, get on the bike," says Jason Pulido, vice president of personal training at Crunch. "If you lift weights, use heavier ones and do fewer reps." Some gyms have roving trainers who can offer free advice or new routines. Or set a motivational goal, perhaps training for a 5k run or walk, swimming a certain number of miles in the pool over the course of a summer, or attending a certain class three days a week for three months. The MTV generation or tech-obsessed can take advantage of some of the newer computerized gadgets to spice things up. There are numerous cycling and running workouts for MP3 players and fitness videos online. Or try one of the new exercise games (like Eye Toy: Kinetic, which leads you through a series of exercises) available for PlayStations.