Konieczynski D D, Truty M J, Biewener A A
Department of Organismal Biology and Anatomy, University of Chicago, Illinois, USA.
J Orthop Res. 1998 Jan;16(1):29-37. doi: 10.1002/jor.1100160106.
The present study sought to answer two research questions. First, how distinctive, as a potential osteogenic stimulus, are short-duration bouts of treadmill exercise relative to sedentary background activity? Second, how well does daily effective strain stimulus relate the loading history for one such exercise program, in comparison with other experimental loading programs, to bone formation? In vivo cortical strains were measured in the tibiotarsus of White Leghorn chickens at a late stage of skeletal growth (14-34 weeks old) under the conditions of a previous investigation of bone formation in response to an exercise program (15 min/day, treadmill gait at 60% maximum speed while carrying 20% body mass) that included sedentary background activity. These strain data were compiled into 24-hour loading histories of peak cyclic strain, demonstrating that strains were statistically different for exercise and background activities (p < 0.0001), with both the magnitude and number of cyclic strain events being greater during exercise (generally greater than 500 microstrain, 2,500 cycles/day) than during background activity (generally less than 500 microstrain, mean: 775 cycles/day). Strains during exercise accounted for more than 97% of the daily effective strain stimulus for bone adaptation, despite the fact that exercise comprised only 1% of the daily period (15 min/day). The levels of the daily effective strain stimulus were similar to those calculated for strains engendered by artificial loading of functionally isolated avian ulnae, which either maintained bone mass or resulted in a 15% increase of cortical cross-sectional area in both sets of studies. These results indicate that short-duration bouts of treadmill exercise and sedentary background activity can represent distinct osteogenic stimuli for adaptive bone modeling. They also provide experimental support for the use of a daily effective strain stimulus to quantify skeletal loading histories for differing programs of physical exercise, although the relative importance of other mechanical and nonmechanical factors requires further investigation.
本研究旨在回答两个研究问题。第一，作为一种潜在的成骨刺激，相对于久坐不动的背景活动，短时间的跑步机运动有何独特之处？第二，与其他实验性负荷方案相比，每日有效应变刺激与这样一个运动方案的负荷历史对骨形成的关联程度如何？在骨骼生长后期（14 - 34周龄）的白来航鸡胫跗骨中，在先前一项关于响应运动方案（每天15分钟，以60%最大速度在跑步机上行走，同时背负20%体重）的骨形成研究条件下，测量体内皮质应变，该研究条件包括久坐不动的背景活动。这些应变数据被汇编成24小时峰值循环应变的负荷历史，表明运动和背景活动的应变在统计学上存在差异（p < 0.0001），运动期间循环应变事件的幅度和数量均大于背景活动期间（运动期间一般大于500微应变，每天2500次循环；背景活动期间一般小于500微应变，平均每天775次循环）。尽管运动仅占每日时长的1%（每天15分钟），但运动期间的应变占骨适应每日有效应变刺激的97%以上。每日有效应变刺激水平与功能孤立的禽类尺骨人工加载所产生应变的计算水平相似，在这两组研究中，人工加载要么维持骨量，要么导致皮质横截面积增加15%。这些结果表明，短时间的跑步机运动和久坐不动的背景活动可代表适应性骨建模的不同成骨刺激。它们还为使用每日有效应变刺激来量化不同体育锻炼方案的骨骼负荷历史提供了实验支持，尽管其他机械和非机械因素的相对重要性需要进一步研究。
