If you want to pump up your bone density but don’t like to lift heavy weights, take heart: You can get significant results using very light weights, as long as you do a lot of repetitions, suggests a small study from Penn State University in the Journal of Sports Medicine and Physical Fitness.
Resistance training improves bone density by putting stress on bones, with greater force resulting in greater results, which is why heavy weights with fewer repetitions are typically recommended for bone (and muscle) benefits. But such protocols are not always practical or feasible for everyone, especially many older people.
Participants (average age 48, mostly women), who were previously sedentary, were randomly assigned either to a low-load, high-repetition resistance-training program or to classes that focused on core strength exercises (no weights), two or three times a week for 27 weeks. The resistance-training group used very low weights (about 20 percent of the maximum they could lift—as opposed to 75 to 80 percent for more standard weight lifting) and a very high number of repetitions (800 to 1,000 per 60-minute session, or about 100 reps for each exercise).
The exercises were done using weighted bars and self-selected weights (no machines) and included squats, chest presses, dead lifts, dead rows, triceps extensions, and lunges. All participants also went to cycling classes three times a week for cardiovascular conditioning. Bone density measurements were taken at the start and end of the study.
Both groups lost body fat and improved strength, but only the weight-training group showed increases in bone density, which ranged from 4 to 8 percent, on average, at various sites. This is notable, considering that people begin losing bone mass in the third decade of life, after peak mass is achieved, with a rate that accelerates in women during menopause. Though the study included just a handful of postmenopausal women and people with osteopenia (low bone mineral density, or BMD), they benefited most from low-load training.
Bottom line: Previous studies have yielded inconsistent data about whether training with light weights has bone benefits, but the new findings “indicate that this type of strength training may be an effective and maintainable method of increasing BMD in older and untrained populations,” the researchers wrote. Many health clubs offer such classes, or you can do a similar workout at home using hand weights or bars. The program followed in the study, Bodypump by Les Mills, is available at some gyms and “on demand” (with a free trial), which you can do on a device such as a tablet, computer, or smart TV.