A QUANTITAVE TEST OF ON-ORBIT EXERCISE COUNTERMEASURES

这个子项目是利用由NIH/NCRR资助的中心拨款提供的资源的许多研究子项目之一。子项目和调查员(PI)可能从另一个NIH来源获得了主要资金，因此可能会出现在其他CRISE条目中。列出的机构是针对中心的，而不一定是针对调查员的机构。卧床休息是研究在长时间航天飞行中发生的在轨肌肉骨骼变化的极佳模拟。我们的新方法包括量化选定的自由生活志愿者受试者的典型日常负荷，这些受试者不是习惯性锻炼者，并基于每日负荷刺激理论规划个人运动处方。然后，受试者将被随机分为对照组或运动组，并被限制在克利夫兰临床基金会(CCF)综合临床研究中心(GCRC)的6度头朝下卧床休息12周。在此期间，锻炼组将在CCF独特的零重力运动模拟器(ZLS)中接受个性化的日常锻炼计划，该模拟器旨在取代他们在自由生活期间经历的日常机械负荷刺激。锻炼将使用一台跑步机和一个类似于国际空间站上提供的阻力锻炼装置。在卧床开始和结束时，将进行DXA、MRI和QCT扫描，以评估骨密度的变化、肌肉体积的变化以及骨的局部变化(皮质骨与骨小梁)。DXA扫描也将在卧床第8周进行。强度测量将在卧床前和卧床后收集，尿液和血清骨吸收和形成的标记物也将被评估。饮食摄入量将由注册营养师计划和监督，以维持恒定的体重和平衡的宏量和微量营养素摄入量，GCRC医生将全天24小时服务于任何医疗需求。在卧床休息后的8周内，将为受试者提供康复计划。对于间歇性负荷替代是否能够充分保护肌肉骨骼系统免受运动性骨量减少和肌肉萎缩的影响这一问题，拟议的实验应该提供一个明确的答案，并可能开启个性化运动对策规划的新纪元。

This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Bedrest is an excellent analog for the study of on-orbit musculoskeletal changes that occur during long-duration spaceflight. Our novel approach involves quantifying typical daily loads to the lower extremities in selected free-living volunteer subjects who are not habitual exercisers and planning individual exercise prescriptions based on daily load stimulus theory. Subjects will then be randomized to control or exercise groups and confined to 6-degree head-down bedrest in the General Clinical Research Center (GCRC) at the Cleveland Clinic Foundation (CCF) for 12 weeks. During this time, the exercise group will undergo individualized daily exercise programs in the unique Zero Gravity Locomotion Simulator (ZLS) at CCF designed to replace their daily mechanical load stimulus experienced during free living. A treadmill and a resistance-exercise device similar to those available on the International Space Station will be used for exercise. DXA, MRI, and QCT scans will be conducted at the start and end of bedrest to assess variations in bone mineral density, changes in muscle volume, and regional changes (cortical vs. trabecular) in bone. DXA scans will also be conducted at week 8 of bedrest. Strength measurements will be collected pre- and post-bedrest, and urinary and serum markers of bone resorption and formation will also be assessed. Dietary intake sufficient to maintain constant body weight with a balanced intake of macro- and micronutrients will be planned and supervised by a registered dietician, and a GCRC physician will be available 24 hr/day to attend to any medical needs. A rehabilitation program will be offered to subjects in the 8 weeks following bedrest. The proposed experiment should provide a categorical answer to the question of whether intermittent load replacement can adequately protect the musculoskeletal system against hypokinetic osteopenia and muscle atrophy and may open a new era in individualized exercise countermeasure planning.