Anti-Aging FitnessWhen you put on a dress, can you zip up the back without help? If you change shoes, can you do it standing up? Can you hoist a heavy bag of cat litter? Chase a dog that’s gotten off the leash? Could you do all those things better 20 years ago? And how well will you do them two decades down the pike? If these tasks are a lot harder now than they used to be, rest assured they’ll only become more of a challenge. But declining strength and flexibility are not inevitable, and how well you will function 20 years into the future depends a lot on how physically active you are right now. "What we think of as signs of aging are actually just symptoms of muscle disuse," says Pamela Peeke, MD, author of Body for Life for Women. "But you can erase problems if you stay active in a variety of ways."Resistance training, for instance, can stave off the decline in muscle mass that starts to happen after age 40, says exercise physiologist Wayne Westcott, PhD, of the South Shore YMCA in Quincy, Massachusetts. Heart-healthy aerobic workouts are rejuvenating too; they can offset the drop in lung capacity that begins as early as age 25. How can you slow down your age clock? Start by taking these tests devised by Westcott, which show how old you are, biologically, based on the five elements of fitness: strength, core (back and abdominal) function, flexibility, balance, and endurance. Once you pinpoint your weak areas, follow our workout plan for four weeks, then test yourself again. Our prediction: In 2029, you’ll feel 20 years younger — and maybe look that way too.The Game PlanOn the next four pages: tests to assess your biological age (versus your calendar age) and exercises to lower it. After four weeks you’ll feel more vigorous and youthful.1. Take the tests You can do one a day for five days, or do them all in one session, leaving at least 15 minutes between tests for recovery.2. Rank the results Mark your weakest fitness area as #1 and your strongest as #5. This will help you prioritize which problems to address first. If there’s a tie, focus first on the area you most want to ignore.3. Make your plan Choose the exercises that will most improve your problem areas. Then create a schedule of activities for the next two weeks, starting with your highest priorities. Shoot for six to 10 sessions that last 30 to 60 minutes each. If an activity affects more than one element of fitness (for example, yoga helps both core function and balance), check off all the appropriate categories.4. Show up and sweat Follow the workouts. Pick up the intensity until you’re maxed out.5. Start over After two weeks, repeat the tests. The new results will prove that your efforts are paying off. If your weak and strong areas change, reorder your priorities based on the new rankings. Then plan two more weeks of workouts. 6. Celebrate After just four weeks, you should see a dramatic difference in your abilities. Now keep your program going!Strength: Dip TestStrong muscles not only make your life easier, they also boost your metabolism. "Those hungry muscle cells chew up calories at two to three times the rate of fat cells," Peeke says. Other benefits: Muscle-building workouts toughen your bones and tone your flab.Dip TestSit on a sturdy chair (not one with wheels!) and slide your butt off, gripping the front edge of the chair with both hands to support yourself. Make sure your arms are straight, your butt is in front of the seat and your legs are straight in front of you. Then bend your elbows to 90 degrees and press back up; repeat as many times as you can. If you get to 15, you’re finished.Your Score/Biological Age Reps Body Age 13 to 15 20s 10 to 12 30s 8 to 9 40s 5 to 7 50s 3 to 4 60+ Fitness RxWhat works: Classic strength-training moves, including the triceps dip test you just performed. (It firms the back of your arms and shoulders.) Build more power with weightlifting machines, dumbbells, and bodysculpting and/or boxing classes.How often: Two 30- to 60-minute strength-training sessions a week.Core: Bicycle TestThe muscles in your abdomen, back, and hips make up your core, which holds you upright and allows the upper and lower body to work together. To keep this important area functioning well, you need to do more than crunches, Peeke says.