Associations Between Physical Activity And Lower‐Limb Strength With Bone Parameters In Healthy Young Women: A Pilot Study

Abstract

BackgroundMechanical loading‐induced strain provided from physical activity plays an essential role in promoting bone modeling. Furthermore, muscle contraction is an important factor in maintaining bone mass. Therefore, the study aimed to investigate the relationship between physical activity level and lower‐limb strength with bone mineral density (BMD), bone microarchitecture and body composition in young women.MethodsHealthy young women (age: 29.0±6.2 yrs, BMI: 22.46±2.26 kg/m2, n=14), not engaged in systematic exercise training programs, participated in this cross‐sectional study. Moderate‐to‐vigorous physical activity (MVPA) was assessed by accelerometry (ActiGraph GT3X+) for seven consecutive days. Leg press one repetition maximum (1‐RM) test was conducted in order to evaluate lower‐limb strength. BMD (i.e. assessed in four different skeletal sites, as follows: whole body, total femur, femur neck and lumbar spine) and body composition (i.e. lean mass and bone mineral content [BMC]) were measured by dual‐energy x‐ray absorptiometry. Trabecular bone microarchitecture parameters were measured by high‐resolution peripheral quantitative computed tomography in left tibia.ResultsThere was a positive correlation between MVPA and some skeletal sites, such as: total femur BMD (r=0.62, p=0.041) and femur neck BMD (r=0.63, p=0.038). No significant correlation was observed between MVPA and trabecular bone microarchitecture parameters. MVPA was significant correlated with lean mass (r=0.90, p<0.001) and BMC (r=0.78, p=0.004). Lower‐limb strength was positively correlated with whole body BMD (r=0.66, p=0.009), total femur BMD (r=0.76, p=0.001), femur neck BMD (r=0.69, p=0.006), lumbar spine BMD (r=0.74, p=0.002), as well as tibial trabecular number (Tb.N) (r=0.63, p=0.021), and a negative correlation between tibial trabecular separation (Tb.Sp) (r=−0.55, p=0.050). With regard to body composition, lower‐limb strength was significantly associated with lean mass (r=0.73, p=0.002) and BMC (r=0.83, p<0.001).ConclusionsThese preliminary data show that both lower‐limb strength and physical activity level are positively associated with measurements of BMD in young women, especially in lower‐limb sites. Furthermore, lower‐limb strength, but not physical activity level, is positively associated with tibial trabecular number and negatively associated with tibial trabecular separation.Support or Funding InformationFAPESP (process: 2015/02833‐5)