Rantalainen T, Sievänen H, Linnamo V, Hoffrén M, Ishikawa M, Kyröläinen H, Avela J, Selänne H, Komi P V, Heinonen A
Neuromuscular Research Centre, Department of Biology of Physical Activity, University of Jyväskylä, Finland.
Bone. 2009 Nov;45(5):956-63. doi: 10.1016/j.bone.2009.07.014. Epub 2009 Jul 23.
Given the adaptation of bone to prevalent loading, bone loss should follow, but lag behind, the decline in physical performance during aging. Furthermore, bone responsiveness to load-induced strains is believed to decrease with aging. However, the relationship between bone and lean body ( approximately muscle) mass appears to remain rather constant throughout adulthood. The purpose of this study was to examine the association between age and bone to neuromuscular performance ratio. Young (N=20, age 24 SD+/-2 years, body mass 77+/-11 kg, height 178+/-6 cm) and elderly (N=25, 72+/-4 years, 75+/-9 kg, 172+/-5 cm) men served as subjects. Bone structural traits were measured at the right distal tibia and tibial mid-shaft with peripheral quantitative computed tomography (pQCT). Maximal section modulus (Z(max50)), total area (ToA(d)), cortical area (CoA(50)), total density (ToD(d)) and cortical density (CoD(50)) were determined from the pQCT images. Neuromuscular performance was measured by recording vertical ground reaction force (GRF) in maximal bilateral hopping. Load-induced strains were estimated by calculating appropriate indices for compressive and tensile loading that took into account both the bone structure and apparent biomechanics of the given bone site. Young subjects had significantly higher maximal GRF compared to older men (4260+/-800 N vs. 3080+/-600 N, P<0.001). They also had smaller ToA(d) (1100+/-170 mm(2) vs. 1200+/-100 mm(2), P=0.028) while their ToD(d) was higher (370+/-46 g/cm(3) vs. 330+/-22 g/cm(3), P=0.002). The Z(max50) did not differ significantly between young (1660+/-320 mm(3)) and elderly men (1750+/-320 mm(3)) (P=0.224). Compressive (0.484+/-0.102 vs. 0.399+/-0.078, P=0.016) and tensile (0.107+/-0.016 vs. 0.071+/-0.018, P<0.001) strain indices were significantly higher in the younger group. In conclusion, the difference in bone to loading ratio at the tibial mid-shaft is bigger than expected from the delay in bone adaptation alone. Potential candidates to explain this phenomenon include a decrease in mechanosensitivity with aging, inability of maximal physical performance to adequately represent the bone loading environment, or the need to maintain constant safety factors to functional strains.
鉴于骨骼会适应常见负荷，骨质流失应随之发生，但会滞后于衰老过程中身体机能的下降。此外，据信骨骼对负荷诱导应变的反应能力会随着衰老而降低。然而，在整个成年期，骨骼与瘦体重（大致为肌肉）之间的关系似乎保持相当稳定。本研究的目的是检验年龄与骨与神经肌肉性能比值之间的关联。年轻男性（N = 20，年龄24±2岁，体重77±11千克，身高178±6厘米）和老年男性（N = 25，72±4岁，75±9千克，172±5厘米）作为研究对象。使用外周定量计算机断层扫描（pQCT）测量右胫骨远端和胫骨中段的骨结构特征。从pQCT图像中确定最大截面模量（Z(max50)）、总面积（ToA(d)）、皮质面积（CoA(50)）、总密度（ToD(d)）和皮质密度（CoD(50)）。通过记录最大双侧单脚跳时的垂直地面反作用力（GRF）来测量神经肌肉性能。通过计算考虑给定骨部位的骨结构和表观生物力学的压缩和拉伸负荷的适当指标来估计负荷诱导应变。与老年男性相比，年轻受试者的最大GRF显著更高（4260±800牛 vs. 3080±600牛，P < 0.001）。他们的ToA(d)也更小（1100±170平方毫米 vs. 1200±100平方毫米，P = 0.028），而他们的ToD(d)更高（370±46克/立方厘米 vs. 330±22克/立方厘米，P = 0.002）。年轻男性（1660±320立方毫米）和老年男性（1750±320立方毫米）之间的Z(max50)没有显著差异（P = 0.224）。年轻组的压缩应变指数（0.484±0.102 vs. 0.399±0.078，P = 0.016）和拉伸应变指数（0.107±0.016 vs. 0.071±0.018，P < 0.001）显著更高。总之，胫骨中段骨与负荷比值的差异比仅由骨骼适应延迟所预期的更大。解释这一现象的潜在因素包括随着衰老机械敏感性降低、最大身体机能无法充分代表骨骼负荷环境，或需要维持功能应变的恒定安全系数。
