Just like muscle, you lose bone mass as you age, too. This increases the likelihood you'll one day suffer a debilitating fracture in your hips or vertebrae. That's even worse than it sounds, since U.K. researchers found that among older women who break a hip during a fall, more than 50 percent will never walk again. In addition, significant bone loss in your spine can result in the dreaded "Dowager's hump," a condition that leaves you with a hunchback. The good news: A study in the Journal of Applied Physiology found that 16 weeks of resistance training increased subjects' hip bone density, and elevated their blood levels of osteocalcin—a marker of bone growth—by 19 percent.
Another bone-related benefit: Researchers in Georgia found that osteoarthritis sufferers who performed leg exercises through a full range of motion three times a week reduced knee pain by up to 58 percent.
6. You'll Be More Flexible
Over time, your flexibility can decrease by up to 50 percent. This makes it harder to squat down, bend over, and reach behind you. But in a study published in the International Journal of Sports Medicine, scientists found that three full-body workouts a week for 16 weeks increased flexibility of the hips and shoulders, while improving sit-and-reach test scores by 11 percent. Not convinced that weight training doesn't leave you "muscle-bound?" Research shows that Olympic weightlifters rate only second to gymnasts in overall flexibility.
7. Your Heart Will Be Healthier
Pumping iron really does get your blood flowing. Researchers at the University of Michigan found that people who performed three total-body weight workouts per week for two months decreased their diastolic blood pressure (the bottom number) by an average of eight points. That's enough to reduce the risk of a stroke by 40 percent, and the risk of a heart attack by 15 percent.
8. You'll Derail Diabetes
Call it muscle medication. In a 4-month study, Austrian scientists found that people with type 2 diabetes who started strength training significantly lowered their blood sugar levels, improving their condition. Just as important, lifting may be one of the best ways to prevent diabetes in the first place. That's because it not only fights the fat that puts you at an increased risk for the disease, it also improves your sensitivity to the hormone insulin. The end result: Your body has an easier time moving sugar from your blood stream into your muscles cells. This helps keep your blood sugar under control, reducing the likelihood you'll develop diabetes.