The 3 Rules of Staying Fit at Every Age

Let's put this archaic idea to bed, once and for all: Your physique is not destined for a downhill slide as you age. Sure, your body changes as the decades go by, but there's plenty of proof that good diet and exercise habits can override your chronological age, says Barbara Bushman, Ph.D., an exercise physiologist at Missouri State University. "By simply staying active, it's amazing how you can slow down the decline that would otherwise happen," says Bushman.

The key to maintaining your hotness as you rack up birthdays is knowing your body's ever-evolving strengths and weaknesses. (Need an updated baseline? Try these 6 Mini Fitness Tests for areas that matter most.) Things that can be a struggle at 20, like finding a routine you enjoy, can be second nature by your forties. And stuff you took for granted early on, like recovering quickly from a workout, doesn't come as easily in future decades. Knowing what you'll encounter will help keep you looking your best at any, and every, age. Here's how to sharpen your skills in each decade.

IN YOUR 20s

Home In On Cross-Training.
Young fitness buffs sometimes feel invincible, says Hollywood-based trainer Jeanette Jenkins, creator of the Sexy Abs with Kelly Rowland workout DVD. "That can lead to doing too much or going too hard, which can cause injuries." Keep your routine balanced with cardio, strength training, and yoga or Pilates.

Watch Your Weight.
Researchers found that women ages 20 to 25 who were too thin were at increased risk for bone loss. Determining your body mass index (BMI) helps gauge if you're in a healthy range. Calculate yours at nhlbisupport.com/bmi. Here's an easy place to start: How to Use Protein as Your Secret Weight-Loss Weapon

Try A New Bedtime Snack.
In a small study, participants who had two kiwifruit each night before bed went to sleep faster and slept longer. Raw kiwi contains high levels of serotonin and folate, both of which could contribute to the improved Z's.

IN YOUR 30s

Push Your Limit.
Add three to five 30-second sprints during cardio sessions, which will rev up your metabolism and allow your body to keep burning calories hours after your workout, says Hollywood-based trainer Jeanette Jenkins, creator of the Sexy Abs with Kelly Rowland workout DVD. (Or get a similar effect by adding 30-to 60-second cardio blasts, like jumping jacks, in between moves of a strength workout.) Bonus: High-intensity intervals also strengthen your bones, which will make you less prone to fractures and osteoporosis. Start now. Add these to the end of any fitness routine: 5 Moves to Boost Your Metabolism.

Curb Excess Salt And Caffeine. Both can promote bone loss, says Tanya Zuckerbrot, R.D., founder of the F-Factor Diet. She recommends limiting sodium to 1,300 milligrams a day and caffeine to 200 to 300 milligrams to help reduce that risk.

Muscle Up. A study found that the rate of muscle loss tends to be greater in the lower body than in the upper body. Adding exercises like squats, lunges, and deadlifts to your weekly routine (at least twice a week) can help slow and even prevent that loss.

IN YOUR 40s

Bump Up Your Weight Training.
Make sure you are lifting weights that are heavy enough to challenge yourself, says Hollywood-based trainer Jeanette Jenkins, creator of the Sexy Abs with Kelly Rowland workout DVD. Your last few reps of a move should be tough to eke out. Are you avoiding strength training entirely? Here's why you need to Lose Your Fear of Lifting Weights.

Do More Yoga. It's especially valuable now because it boosts flexibility in the spine and hips, which is integral for good posture. Plus, Downward Dog and inversions are amazing for your complexion, bringing blood flow to your face. Consider it an anti-aging facial!

Get Creative.
It's easy to fall into a workout rut in your forties, says Bushman. A new activity, whether it's a salsa dance class, a bicycle tour, or a surfing lesson, can bolster your enthusiasm and pick up your metabolism.

This article on Workouts for Women originally appeared on Women's Health


More from Women's Health:

Amazing Core-Sculpting Moves from Jillian Michaels


The 101 Best Things You Can Do For Your Body-Starting Now


Build an At-Home Sweat Center You Will Actually Use