The 3-Day Age-Defying Full-Body Upgrade

The familiar story of the 40-something athletic comeback begins with good intentions, but usually ends with a demoralized dad horizontal on the couch. "Too often, guys jump back into a regimen and hurt themselves," says Kevin Elsey, a performance specialist at Athletes' Performance in Phoenix. The problem is threefold: Your metabolism has slowed, your muscles are wasting away, and your tendons are more brittle. "In the past five years, we've seen huge advances in our understanding of human performance," explains Elsey. To get back in the game—the right way—embrace the new science of exercise.

Old science: Slow, static stretching prepares the body for peak performance.

New science: Dynamic "movement prep" exercises do it better.

Static stretches don't improve performance or prevent injury prior to activity, according to a range of research. Instead, trainers recommend "movement prep," low-intensity moves that prepare your body for exercise. It increases core temperature, lengthens and loosens tight muscles and ligaments, and strengthens and stabilizes the body's pillar—the critical combination of your hips, torso, and shoulders that is engaged in every movement you make.

Old science: Work muscles in isolation.

New science: Train the body as an interconnected whole.

"It's important to design your workout so that it engages and brings balance to your entire body," says Elsey. "The days of walking into the weight room and training purely for huge biceps and calves are over. Those muscles might look good on the beach, but if you maintain this narrow focus at the gym, you become a sitting duck for those aches and pains to turn into injuries." If your body is a temple, your core is its foundation. Doing functional "real-world strength" exercises will keep your body operating at peak efficiency.

Old science: Cardio is king.

New science: Strength training rules.

To thwart sarcopenia, the involuntary loss of muscle and bone that stalks every man as he ages, it's essential to incorporate weight-bearing exercises that build muscular and skeletal strength, according to a systematic review in the journal Age and Ageing. Researchers found that resistance training is the best way to slow sarcopenia, more powerful than even growth hormone replacement or testosterone supplementation. Does this mean you should abandon cardio? Not at all. If you're a committed runner or cyclist, keep it up, but work in weekly strength sessions as well.

Old science: Long, slow distance is best for weight loss.

New science: Increased density and intensity are the keys to burning fat.

"People are blown away by how many exercises we do in 30 minutes," says Elsey, whose system uses efficient circuits that strengthen movement patterns by combining strength training with flexibility and stability moves. A well-designed workout program can add hours to your week in saved gym time. Case in point: interval training. By alternating bursts of high-intensity effort with active rest, intervals can actually help you lose weight faster than training at a steady state for the same amount of time.