"If you start to slump, your shoulders round and you look older," Brehm adds.Flexibility: 10 minutes daily "Stretching and other flexibility work becomes more important as you get older," says Mitch Gaylord, creator of The Perfect 10 Workout DVD (perfect10workout.com). Tendons and ligaments dry out, so pushing more blood to them by stretching helps you stay flexible. You’re also helping your heart. "Stretching squeezes the blood right through the muscles and back to the heart," Peeke says. Refresh your stretch repertoire with The Stretch Deck (amazon.com) or Karen Voight’s Pure & Simple Stretch DVD (amazon.com).The Mortar: Mental MotivationPassion Use something you love — a sport, a new challenge — to help you set fitness goals. "Think about goal-setting as a way to guide your focus," says Gaylord. By your 40s, you know which kinds of exercise you enjoy and what makes your workouts fun. Joining a tennis league or tackling something specific, like a mini triathlon, can give you the structure you need to get your best workouts.Variety "If you do the same workout all year long, you get diminishing returns in terms of results," Sansone says. "It takes about 12 weeks for your body to hit a plateau, so switching your workouts with the seasons makes sense." And since you’re more injury-prone with age, you’ll avoid repetitive stress injuries by mixing it up. Keeping a workout journal can help you tweak your routine regularly. "If you don’t track your progress, you won’t be able to tell if you’re slacking off," Gaylord says. "Writing it down keeps you honest."Rest (ahhh!) When you allow your body to fully recover from exercise, you perform better at the next workout. Alternate tough cardio sessions with mellow walks. Between strength sessions, take at least 48 hours to recover. (Some recent research even suggests that women 40 and over need to give muscles a 72-hour break between workouts.) You can alternate upper- and lower-body exercises on strength-training days to build in rest for the different muscle groups. Originally published in MORE magazine, May 2007.