Low-Magnitude Mechanical Loading Becomes Osteogenic When Rest Is Inserted Between Each Load Cycle
作者:Sundar Srinivasan、David A. Weimer、Steven C. Agans、Steven D. Bain、Ted S. Gross
DOI:10.1359/jbmr.2002.17.9.1613
日期:——
Strategies to counteract bone loss with exercise have had fairly limited success, particularly those regimens subjecting the skeleton to mild activity such as walking. In contrast, here we show that it is possible to induce substantial bone formation with low‐magnitude loading. In two distinct in vivo models of bone adaptation, we found that insertion of a 10‐s rest interval between each load cycle transformed a locomotion‐like loading regime that minimally influenced osteoblast activity into a potent anabolic stimulus. In the avian ulna model, the minimal mean (+SE) periosteal labeled surface (Ps.LS) observed in the intact contralateral bones (1.6 ± 1.5%) was doubled after 3 consecutive days of low‐magnitude loading (3.8 ± 1.5%; p = 0.03). However, modifying the regimen by inserting 10 s of rest between each load cycle significantly enhanced the periosteal response (21.9 + 4.5%; p = 0.03). In the murine tibia model, 5 consecutive days of 100 low‐magnitude loading cycles did not significantly alter mean periosteal bone formation rate (BFR) compared with contralateral bones (0.011 ± 0.005 μm3/μm2 per day vs. 0.021 ± 0.013 μm3/μm2 per day). In contrast, separating each of 10 of the same loading cycles with 10 s of rest significantly elevated periosteal BFR (0.167 ± 0.049 μm3/μm2 per day; p = 0.01). Endocortical bone formation parameters were not altered by any loading regimen in either model. We conclude that 10 s of rest between each load cycle of a low‐magnitude loading protocol greatly enhances the osteogenic potential of the regimen.
通过运动来抵消骨质流失的策略取得的成功相当有限,尤其是那些让骨骼进行轻微活动(如散步)的方案。与此相反,我们在这里展示了通过低强度负荷诱导大量骨形成的可能性。在两种不同的体内骨适应模型中,我们发现,在每个负荷周期之间插入 10 秒钟的休息时间,可将对成骨细胞活动影响最小的类似运动的负荷机制转变为一种强有力的合成代谢刺激。在鸟类尺骨模型中,连续 3 天的低强度加载后,在完整对侧骨中观察到的最小平均(+SE)骨膜标记面(Ps.LS)(1.6 ± 1.5%)增加了一倍(3.8 ± 1.5%;P = 0.03)。然而,通过在每个加载周期之间插入 10 秒钟的休息时间来改变加载方案,则可显著增强骨膜反应(21.9 + 4.5%;p = 0.03)。在小鼠胫骨模型中,与对侧骨(每天 0.011 ± 0.005 μm3/μm2 与每天 0.021 ± 0.013 μm3/μm2 相比)相比,连续 5 天 100 次低强度加载循环并不会显著改变平均骨膜骨形成率(BFR)。相比之下,在 10 个相同的加载周期中,每个周期休息 10 秒钟可显著提高骨膜 BFR(每天 0.167 ± 0.049 μm3/μm2; p = 0.01)。在这两种模型中,任何加载方案都不会改变皮质内骨形成参数。我们的结论是,在低强度加载方案的每个加载周期之间休息 10 秒可大大提高该方案的成骨潜力。