The two faces of growth: Benefits and risks to bone integrity
The two faces of growth: Benefits and risks to bone integrity
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生长的两个方面：骨骼完整性的益处和风险
作者：
A. Parfitt
骨骼的生长有两个过程：皮质骨通过骨膜附着（宽度增长）形成，松质骨通过软骨内骨化（长度增长）形成。在中轴骨和无骨骨骼中，大约一半的峰值成人骨量是在青春期生长突增期间积累的，女孩比男孩早两年，并且通过生长激素和性激素之间的相互作用受到垂体的控制。在整个生长过程中，特别是在青春期，骨骼适应机械负荷的能力比成熟后大得多。这就是为什么在对年轻运动员的横断面研究中，身体活动对骨骼的影响要大于对以前久坐的成年人的纵向研究的主要原因。在野生动物中，当生长停止时，骨骼必须像它们所需要的那样强壮，在停止生长后获得进一步的力量将不会有生物学目的。生长中的骨对机械负荷的适应是恒力器的目的，它使个体的生理适应能够建立和维持由种群进化适应决定的骨的种属特异性。但增长给骨骼带来了风险和好处。上肢（尤其是前臂下部）骨折的发病率大幅增加，与青春期的生长突增相一致，这是由于皮质内骨转换增加导致皮质孔隙率增加，皮质内骨转换提供了长骨生长端所需的一些钙。这使得对钙的需求增加能够在更长的时间内传播，类似于鹿的鹿茸生长周期中发生的周期性生理性骨质疏松症。随后皮质孔隙率的下降是导致生长停止后桡骨骨密度持续增加的原因，称为固结。在目前的知识状态下，在青春期生长突增期间骨折发生率的增加是适当水平的体力活动的不可避免的结果，并且是为了在生长期间最大化骨积累和在老年时最小化骨折风险而必须付出的代价。
Bones grow by two processes: cortical bone is made by periosteal apposition (growth in width), and cancellous bone is made by endochondral ossification (growth in length). In both the axial and appendicular skeleton, about half of peak adult bone mass is accumulated during the adolescent growth spurt, which occurs two years earlier in girls than in boys, and is under pituitary control via interactions between growth hormone and sex hormones. Throughout growth, but particularly during adolescence, the ability of bone to adapt to mechanical loading is much greater than after maturity. This is the main reason why the effects of physical activity on bone are greater in cross-sectional studies in young athletes than in longitudinal studies in previously sedentary adults. In wild animals, by the time growth has ceased, the bones must be as strong as they will ever need to be, and attainment of further strength after cessation of growth would serve no biologic purpose. Adaptation of growing bone to mechanical loading is the purpose of the mechanostat, which enablesphysiologic adaptation in individuals to establish and maintain a species-specific property of the bones that is determined byevolutionary adaptation in populations. But growth confers risks as well as benefits to the skeleton. The large increase in incidence of upper extremity (particularly lower forearm) fractures, coincident with the adolescent growth spurt in both sexes, is due to an increase in cortical porosity as a consequence of an increase in intracortical bone turnover, which supplies some of the calcium needed by the growing ends of the long bones. This enables an increased demand for calcium to be spread over a longer time, analogous to the cyclic physiologic osteoporosis which occurs during the antler growth cycle in deer. The subsequent decline in cortical porosity is responsible for the continued increase in radial bone density after cessation of growth, referred to as consolidation. In the present state of knowledge, an increased incidence of fracture during the adolescent growth spurt is the inescapable consequence of an appropriate level of physical activity, and is the price that has to be paid in order to maximize bone accumulation during growth and minimize fracture risk in old age.
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从事负重和非负重活动的运动员骨密度的决定因素。
DOI：
10.1152/jappl.1989.67.3.1100
发表时间：
1989
期刊：
Journal of applied physiology (Bethesda, Md. : 1985)
影响因子：
--
作者：
Block,JE;Friedlander,AL;Brooks,GA;Steiger,P;Stubbs,HA;Genant,HK
通讯作者：
Genant,HK
小型哺乳动物和双足鸟类的骨强度：安全因素会随着体型的变化而变化吗？
DOI：
10.1242/jeb.98.1.289
发表时间：
1982
期刊：
The Journal of experimental biology
影响因子：
--
作者：
Biewener,AA
通讯作者：
Biewener,AA
影响因子：
20.3
作者：
J. R. Kerrigan;A. Rogol
通讯作者：
J. R. Kerrigan;A. Rogol
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影响因子：
1.5
作者：
Dalsky,GP
通讯作者：
Dalsky,GP
影响因子：
39.2
作者：
DALSKY, GP;STOCKE, KS;BIRGE, SJ
通讯作者：
BIRGE, SJ