Karlsson Magnus
Department of Orthopaedics, Malmo University Hospital, SE-205 02 Malmo, Sweden.
Scand J Med Sci Sports. 2002 Aug;12(4):197-210. doi: 10.1034/j.1600-0838.2002.00207.x.
Exercise during growth seems to build a stronger skeleton resulting in a high peak bone mineral density (BMD) in men. Exercise during adulthood produces benefits in BMD or prevents bone loss, but the changes are of minor biological significance as regards fracture reduction. However, prospective intervention studies suggest exercise to improve muscle strength, co-ordination and balance, even in octogenarians--all traits possible to reduce the number of falls. It is virtually impossible to undertake a randomized blinded study of exercise with fracture as end point due to the large cohorts needed. Retrospective and prospective observational and case control studies suggest activity to be associated with reduced fracture risk. This may be correct, but consistently replicated sampling bias may produce the same observation. The Achilles heel of exercise is the cessation of physical activity. Biologically important benefits in BMD or improvement in muscle size and strength achieved by exercise during growth and young adulthood seem to be eroded in retirement, leaving virtually no remaining benefits in old age, the period when fragility fractures exponentially rise. On the contrary, continued exercise on a lower level may maintain some of the musculoskeletal benefit, but dose-response relationships need to quantified, as do the effects of exercise on bone size, shape, architecture and frequency of injurious falls. Absence of evidence is not evidence of absence of effect, but if we recommend exercise then should this be to children, adults, elderly men or men with fractures? What type of exercise? For how long? How many fewer fractures will result in the community from a community based exercise campaign like the anti-tobacco campaign? The higher level of proof, suggesting exercise to reduce spine and hip fractures must come from well designed and executed prospective randomized studies. Blinded studies obviously cannot be done but open trials can, and should be undertaken.
成长过程中的运动似乎能构建更强壮的骨骼，使男性达到较高的骨矿物质密度峰值。成年期运动对骨矿物质密度有益或可预防骨质流失，但就减少骨折而言，这些变化的生物学意义不大。然而，前瞻性干预研究表明，运动能提高肌肉力量、协调性和平衡能力，即使对八旬老人亦是如此——这些特质都有助于减少跌倒次数。由于所需队列庞大，几乎不可能进行以骨折为终点的运动随机双盲研究。回顾性和前瞻性观察性研究以及病例对照研究表明，活动与降低骨折风险相关。这可能是正确的，但持续存在的抽样偏差可能会产生相同的观察结果。运动的致命弱点在于身体活动的停止。在成长和青年成年期通过运动在骨矿物质密度方面获得的生物学重要益处，以及肌肉大小和力量的改善，在退休后似乎会逐渐消失，在老年期（即脆性骨折呈指数级上升的时期）几乎不再有剩余益处。相反，较低强度的持续运动可能会维持一些肌肉骨骼方面的益处，但运动的剂量反应关系以及运动对骨骼大小、形状、结构和有害跌倒频率的影响都需要量化。缺乏证据并不证明没有效果，但如果我们推荐运动，那么应该针对儿童、成年人、老年男性还是骨折患者呢？何种类型的运动？持续多久？像反烟草运动那样的社区运动能使社区骨折发生率降低多少？要证明运动能减少脊柱和髋部骨折，更高水平的证据必须来自精心设计和实施的前瞻性随机研究。显然无法进行双盲研究，但可以且应该开展开放试验。
