The Reader: For the past few years, former competitive swimmer Margaret Smith has focused on running and hitting the pool a few times a week. She likes her routine but says she neglects other cardio routines, strength training, and stretching.

The Expert: Tom Holland, an American Council on Exercise–certified trainer and exercise physiologist, and author of The 12-Week Triathlete.

Before: Holland wrote to Cooking Light seeking variety—and a well-rounded workout. "I tend to get into one sport and forgo everything else I should be doing," says the Tarrytown, New York–based college professor, who runs 10 to 20 miles per week.

Doing the same activity at the same distance and pace for an extended period of time may be keeping Smith in shape, but it prevents her from increasing her aerobic capacity and muscle strength, says Holland. "Your muscles adapt to your exercise program, and you'll stop seeing results," he says. Plus, if you don't vary the muscles you use, they'll be more susceptible to injury. Your routine can also become boring.

The Workout: Holland suggests trying a variety of new activities—and change something about your favorites, even slightly, to engage different muscle groups. To motivate Smith to try new things, including adding strength and stretching exercises to her routine, we asked Holland to create a workout with both outdoor and indoor options for each of her preferred activities: running, swimming, and biking. (Smith has cycled periodically in the past and would like to do more.) Each routine includes tips on increasing intensity, plus strength and flexibility exercises, so she can have a total-body workout. When Smith tried it, she immediately noticed a difference.

Click to view the Boost Your Workout with Variety Plan for:

Biking - Improve your aerobic capacity, strengthen your quads, and learn new stretches.

Running - Learn tips to add intensity, strength and flexibility to your runs.

Swimming - Use pace, equipment and in-the-pool stretches to add variety to your routine.

After: When Margaret Smith tried trainer Tom Holland's tips, she realized she had been putting little thought into her routine. "With the new workouts, I found myself focusing on what I was doing, rather than just moving along and letting my mind wander," she says. Smith especially likes how the workouts include strength training and stretching. "I used to skip stretches when I swam, but since this workout suggested some I could do in the pool, I found myself looking forward to them," she says. "They feel great after working so hard." The plans prompted Smith to try swimming and biking two days a week in addition to running, which will help with her new goal: "These routines motivated me to sign up and train for a triathlon!"

Portland, Oregon–based freelance writer Megan McMorris has written for Fitness, Self, and Runner's World, and is the author of Oregon Hiking.