Strong bones need more than workouts; they need less sitting. A sweeping review shows that across all ages, even light daily activity protects bone health, while too much sedentary time quietly raises the risk of fractures.
Physical activity versus sedentary behavior. Over the years, there has been so much research into how these two factors impact our physical and mental health, particularly as we age.
Now, a new review carried out by the International Osteoporosis Foundation (IOF) Rehabilitation Working Group has analyzed previous studies, reviews, and meta-analyses to examine the links between physical activity, sedentary behavior and bone health across the lifespan.
“This review highlights a critical message for populations worldwide: bone health depends not only on engaging in regular physical activity, but also on reducing the hours we spend in sedentary behavior,” said Professor Olivier Bruyère, PhD, Co-chair of the IOF Rehabilitation Working Group and the study’s lead and corresponding author. “In children and adolescents, too much sitting time can undermine bone development, while in adults and older individuals, inactivity accelerates bone loss and fracture risk. Importantly, even light daily activity – such as walking – can provide measurable benefits, particularly for older adults and menopausal women.”
The selection of epidemiological studies, systematic reviews, and meta-analyses examined by the Working Group focused on two main outcomes: bone mineral density (BMD) and fracture risk. BMD is a measure of the mineral content, such as calcium and phosphorus, within a specific amount of bone, indicating bone strength. They looked across all age groups, including children, adolescents, adults, and older adults, paying special attention to studies using objective measures (like accelerometers) and to research on what happens when sedentary time is replaced with light or moderate-to-vigorous activity.
Children and Adolescents
The review found that too much sitting for things such as screen time or inactivity was linked to lower BMD at weight-bearing sites like the neck of the femur (thigh bone). Weight-bearing and impact activities like running, jumping, and resistance training boosted bone mass during growth phases. Benefits from early interventions such as school-based activity programs were seen to last for years, but required ongoing activity to be maintained.
Adults
Regular physical activity, especially moderate-to-vigorous weight-bearing and resistance training, supported higher BMD and reduced fracture risk. Sedentary time was linked to lower BMD, particularly at the hip, femoral neck, and pelvis. Prolonged uninterrupted sitting was found to be worse than shorter bouts of sitting.
Older Adults
Even light activity (things like walking or household chores) improved BMD and lowered fracture risk, especially for postmenopausal women. More vigorous or resistance-based activity provided greater bone-related benefits. Sedentary behavior amplified frailty and fracture risk; older adults who sat a lot were especially vulnerable. The review showed that replacing just 30 minutes of sitting with light activity measurably improved bone health, specifically at the spine, especially in women over 50.
Across the Lifespan
Physical activity and sedentary behavior had independent effects: being active didn’t cancel out the harm of sitting too much. Even small substitutions of sitting with movement mattered. The WHO guidelines on physical activity and sedentary behavior aligned well with optimal bone health strategies. Namely, 60 minutes/day of physical activity for kids, 150 to 300 minutes/week for adults, and minimizing sitting for all age groups.
“The findings highlight the imperative for early intervention and sustained promotion of physical activity throughout the life course, in alignment with WHO recommendations,” said IOF President Professor Nicholas Harvey and IOF Committee of Scientific Advisors (CFA) Chairman Eugene McCloskey in a joint statement. “We therefore urge governments, healthcare providers, and policymakers to implement comprehensive public health strategies that not only encourage active lifestyles but also systematically reduce sedentary behaviors across all populations and age groups, in order to ensure optimal skeletal health and fracture prevention.”
The review has some limitations. Many studies relied on self-reported physical activity and sedentary behavior, which is less accurate than wearable devices that track activity. Nutrition, body weight, and sex differences weren’t always accounted for. Some evidence was inconsistent, especially regarding how sedentary behavior independently affects BMD in older adults. And, few studies directly used time-substitution models to see what happened when sitting was swapped for activity.
Nonetheless, the study’s findings have practical applications in the real world and across all age groups. In healthcare practices, medical professionals should assess physical activity and sedentary behavior in routine visits and prescribe movement like they do medication. Public health policies should build activity-friendly environments, such as walkable cities, active schools, and accessible gyms and parks.
The takeaway message is this: being active is good for bones, sitting too much is harmful, and the two effects are separate. Even small increases in daily movement, especially replacing sitting with light activity, can help protect bone health and reduce fracture risk across the lifespan.
The study was published in the journal Calcified Tissue International.
Source: IOF
