40: Brian Luther, mountaineer and kayaker: "I don't train, I just go out and do it." (Jeff Riedel)
JUST WHEN YOU THINK you've acquired and nailed all the skills necessary for your sport of choice, these ten years introduce serious bugs into the operating system.
The Bad News The cerebrumthe complex part of your brain that is the center for decision-making, learning, and reasoningmay shrink as much as 20 percent over the rest of your adult life. One study has shown that between 45 and 50, response functionsa combination of reaction speed and movement timeslow about 5 percent, or long enough that you'll swipe at air instead of digging out a rival volleyball player's spike. And simultaneously handling a lot of peripheral information also becomes harder; witness the fact that chess grand masters fade by age 40.
You require 120 fewer calories per day at age 40 than at 30, but those remaining calories have to pack more nutrients.
As for the flesh, it's not unusual to carry about 17 more pounds of unneeded mass than you did in your twenties. As fast-twitch muscle fibers wither, explosive power recedes from your forearms and calves, diminishing climbing and sprinting performance, respectively. What's more, key mechanisms for proper kidney function diminish by 10 percent, making dehydration a bigger threat. Drink up.
The Good News "Changing up activities expands your capacities for all physical functions," says Waneen Spirduso, a professor of kinesiology and the director of the Institute of Gerontology at the University of Texas at Austin.
Colorado-based rock climber Jeff Achey, 44, battled encroaching mental and physical deficits by taking on sport routes way beyond his comfort level. Now falling no longer means failureit means he's challenging himself in the right way. "Being OK with a 20-foot fall from an overhang is a skill that every good climber needs," he says. "I know it's made a huge difference in my abilities."
The Prescription You need to keep your internal balance receptors and the nervous system sharp, and you have to strengthen the small muscles that keep the back, hips, knees, and ankle joints in shape, since weakening muscles that cross over your joints result in decreased mobility. Accomplish all the above by balancing on a wobble board for ten minutes, three times a week. >>Your body requires 120 fewer calories per day at age 40 than at age 30, but those remaining calories have to pack more nutrients. Get them from vitamin-heavy fruits and vegetables, not processed foods, and start eating nuts, seeds, olives, fish, and avocadosthe healthy fat in them actually puts the brakes on hunger.