Binkley T L, Specker B L
Ethel Austin Martin Program in Human Nutrition, South Dakota State University, United States.
J Musculoskelet Neuronal Interact. 2016 Mar;16(1):18-23.
Effects of time in moderate to vigorous physical activity (MVPA) and sitting (SIT) on bone were tested, hypothesizing that high MVPA would be positively associated with bone size and strength, offset effects of high SIT, and be mediated by lean mass.
155 children (79 male, 58 pubertal), 6-20 years (10.2±3.5 yr) were measured by dual-energy x-ray absorptiometry (DXA) and peripheral quantitative computed tomography (pQCT). MVPA and SIT were measured by 7-day activity recall. Regression analyses tested effects of MVPA and SIT on bone. Mediation analysis was conducted to determine if lean mass mediated the effect of activity on bone.
In pubertal boys, SIT was negatively associated with tibial endosteal and periosteal circumference as well as bone strength (β= -0.19, -0.14, and -5.68, respectively; all p<0.05). Effects of SIT on bone circumferences and strength were mediated by lean mass. MVPA did not offset the effects of SIT. In pubertal girls, MVPA was positively associated with cortical thickness (β=0.01, p<0.05) and the association was not mediated by lean mass.
Current health communications that encourage increased physical activity should include additional messaging to decrease time spent sitting, especially in pubertal boys.
测试中度至剧烈身体活动（MVPA）时间和久坐（SIT）时间对骨骼的影响，假设高MVPA与骨骼大小和强度呈正相关，抵消高SIT的影响，并由瘦体重介导。
通过双能X线吸收法（DXA）和外周定量计算机断层扫描（pQCT）对155名6至20岁（10.2±3.5岁）儿童（79名男性，58名青春期儿童）进行测量。通过7天活动回忆法测量MVPA和SIT。回归分析测试MVPA和SIT对骨骼的影响。进行中介分析以确定瘦体重是否介导活动对骨骼的影响。
在青春期男孩中，SIT与胫骨内膜和骨膜周长以及骨强度呈负相关（β分别为-0.19、-0.14和-5.68；均p<0.05）。SIT对骨骼周长和强度的影响由瘦体重介导。MVPA没有抵消SIT的影响。在青春期女孩中，MVPA与皮质厚度呈正相关（β=0.01，p<0.05），且这种关联不由瘦体重介导。
当前鼓励增加身体活动的健康宣传应包括额外信息，以减少久坐时间，尤其是在青春期男孩中。
