How much exercise is “enough” for bone health?

When I talk to some of my clients about exercise, I know a lot of them aren’t enthusiastic, thinking I’m going to tell them they need to spend hours lifting heavy weights and sweating in a gym. After all, everyone knows it’s weight-bearing exercise — and lots of it — that builds bone and lowers the risk of fractures, right? 

Surprise! Not necessarily. Two new studies show that even small amounts of low-impact exercise have a positive effect on fracture risk. 

Twenty minutes of walking does the trick

The first study (Stattin et al., 2017) followed over 65,000 Swedish men and women for 17 years and found that participants who walked or bicycled daily for even short periods of time had a lower fracture rate compared with those who did not. Regardless of sex or age, even relatively sedentary people could lower their fracture risk by exercising just a little bit every day. As long as they got at least an hour of exercise per week, these otherwise inactive people had a 13% lower rate of hip fractures and a 6% lower rate of any fracture compared to people who did none at all. 

It’s worth emphasizing that the findings held true whether you looked at any fracture (including common, relatively mild fractures like vertebral or wrist fractures) or the more serious and life-changing hip fractures that everyone fears.

Of course, the more exercise they got, the better the results: those with 20 minutes of walking or cycling every day, which translates to about 2 hours per week — had a 23% lower rate of hip fracture and a 13% lower rate of any fracture. That’s a pretty good return for not a lot of effort — just imagine what you get when you do even more!

Light loads do more than you think

The second study (Hamaguchi et al., 2017) had a small group of 7 postmenopausal women undergo six weeks of training wearing a weighted vest with 380-760 g (roughly from 1.75 pounds) of added weight. With just two workout sessions per week, the participants saw improvements in pelvis BMD (1.6%) and knee extensor strength (15.5%) — which is helpful in maintaining balance and preventing falls. Workouts consisted of squats, front lunges, side lunges, calf raises and toe raises (eight sets of three repetitions with a 15-second rest between each set). 

A little bit goes a long way

I know that it can be hard to start exercising if you’re not accustomed to it, and especially if you’re recovering from a muscle strain or a fracture, the get-up-and-go impulse just isn’t there. But you don’t have to do a lot to get benefit from it! Both of these studies show that a little goes a long way. 

Hamaguchi K, Kurihara T, Fujimoto M, et al. The effects of low-repetition and light-load power training on bone mineral density in postmenopausal women with sarcopenia: a pilot study. BMC Geriatrics 2017;17:102. doi:10.1186/s12877-017-0490-8.

Stattin K., Michaëlsson K., Larsson S.C., Wolk A., & Byberg L. Leisure-Time Physical Activity and Risk of Fracture: A Cohort Study of 66,940 Men and Women. Journal of Bone and Mineral Research 2017;32(8):1599-1606. doi: 10.1002/jbmr.3161.