Old think Lots of repetitions of light weights (for example, 15 to 20 reps of three- to eight-pound dumbbells). That way you won’t bulk up.
New think For a more effective workout, a seasoned exerciser should figure out her maximum ability (the amount of weight you can hoist at one time), then lift 60 to 70 percent of that. If you’re just guessing at your maximum, you may be underestimating yourself and therefore wasting your exercise time, says a study in the Journal of Strength and Conditioning Research. For example, if a woman could lift a 40-pound weight in one bicep curl but doesn’t know it, she might use a four- or eight-pound dumbbell to do her set of 12 reps. That means she’d be lifting only 10 to 20 percent of her max when she should be using a weight that’s 24 pounds or heavier. (If the idea of lifting this much seems outrageous to you, keep in mind that you have probably carried a suitcase that weighs 30 or 40 pounds.) Beginners can improve with less effort, working at 45 percent of max (which in this example would mean lifting an 18-pound dumbbell).
Don’t worry that these heavier weights will bulk you up. For that to happen, even women with a genetic predisposition to becoming muscular would need to eat extra calories and spend hours in the gym lifting ultra-heavy weights. Also, “If you do plenty of cardio, which can hamper the growth of muscles, you won’t get huge,” says Nick Ratamess, PhD, a kinesiology professor at the College of New Jersey, in Ewing.
The workout updated For each strength-training move, choose a weight that feels challenging by the end of one set of eight to 12 repetitions. Since different exercises target different muscles, you may be able to go a lot heavier with some exercises and just a little heavier with others. As you get stronger, first add one more set, then another, so that you work up to doing three sets of eight to 12 repetitions on at least two nonconsecutive days of the week. Then add more weight. “You know it’s time to go heavier when the weight feels easy to lift at the end of each set,” Ratamess says. Aim to increase the load by one or two pounds every two to four weeks.
These heavier weights target more fibers in a muscle than lighter ones do, so more of the overall muscle gets toned; they also stimulate the growth of bone cells, especially in the upper body.
Old think Avoid high impact whenever possible. You know too many midlife women—perhaps including yourself—who got hurt doing aerobics or by running a lot.
New think High-impact activities such as jumping, racquet sports and stair climbing are important because they slow down bone loss, says Kathy Gunter, PhD, assistant professor of nutrition and exercise science at Oregon State University, in Corvallis. Most women can safely add impact intervals by doing 100 jumps three times a week. Combine this exercise with your weight-training regimen; a recent study in the British Journal of Sports Medicine reported that the combination of impact and resistance training is especially helpful in preventing bone loss in the hips and spines of postmenopausal women.
The workout updated If you’re not doing high-impact moves already, build up to them. Start by jumping or running for a minute or two, then add longer intervals gradually. You can also try some “faux jumping” moves used in Gunter’s lab, such as heel drops: Stand and rise up on the toes and balls of your feet. Then, drop your heels quickly and repeat (do two sets of 15 repetitions). Or pretend you are stomping your feet as if you were an angry child, 100 strikes per foot, three times a week. Stomp as hard as it would take to flatten a piece of Bubble Wrap.