Image courtesy of Prevention

It's no secret that working out keeps you younger -- both in terms of the energy you have and your physical ability to keep doing the things you love. "Fitness is a youth serum," says physical therapist and fitness expert Maureen Hagan. "Fitness affects how youthful you look, the way you move, and your ability to do whatever you want, whenever."

Hagan has been training clients for more than 20 years with a focus on active aging, and is also a regularly published research reviewer on the same topic. This past weekend at the IDEA World Fitness Convention, Hagan presented the healthy aging secrets she's learned from both practice and clinical research. Don't worry, we're not about to overhaul your favorite workout. No matter how old you are or what you like to do for exercise, you can use Hagan's secrets to move better, protect yourself from injury, and feel younger.

Your Walking Pains, Solved!

1. Squat right

"People say to me, 'Oh I can't squat, it hurts my knees,'" and then they go and pick up their bag of groceries from the floor," Hagan says. The point: You squat all the time, so it's essential that you learn to do it properly. For women, that means turning your toes out slightly. This simple fix allows your femur to line up properly in the hip joint, causing your knees to track over your ankles instead of caving in. The result: a stronger knee joint and less chance of knee pain. (Men have a different hip structure, so they should squat with toes forward.) Also, "women really do need to step their feet slightly wider than their hips," Hagan adds. "Without the wider stance than hip-width, that knee tracking and movement at the hip cannot happen."

2. Hack your genetics

Ever hear that you can't change your genes? That's only partially true. While you can't change your genetic makeup, you can change how certain genes are expressed -- that is, how much they do whatever they do. And strength training is one of the best ways to do that. Only 26 weeks of resistance training reverses the aging process at the genetic level, research shows. "You can actually train your tissues to behave the way they did when you were younger," Hagan says. Furthermore, resistance training preserves muscle mass that we typically lose as we age -- 5 pounds per decade, on average. (We also gain an average of 10 pounds of fat per decade. "That's certainly not fair! It should at least be even!" Hagan says. Give this Over 40 Metabolism Miracle to even the playing field.)

3. Play on the brain gym

Exercise is a physical crossword puzzle, Hagan likes to say. The more activity you can do that also engages your brain, the better. These can involve reaction training (such as playing tennis or racquetball), memorizing choreography (like you would in step class or Zumba), and changing direction (common in step, kickboxing, and dance classes).