A QUANTITAVE TEST OF ON-ORBIT EXERCISE COUNTERMEASURES

该子项目是利用NIH/NCRR资助的中心赠款提供的资源的许多研究子项目之一。子项目和研究者（PI）可能从另一个NIH来源获得主要资金，因此可以在其他CRISP条目中表示。所列机构为中心，不一定是研究者所在机构。卧床是一个很好的模拟研究在轨肌肉骨骼的变化，发生在长时间的航天飞行。我们的新方法包括量化典型的日常负荷，以下肢在选定的自由生活的志愿者受试者谁是不习惯锻炼和规划个人运动处方的基础上，每日负荷刺激理论。然后，受试者将被随机分配到对照组或运动组，并在克利夫兰临床基金会（CCF）的一般临床研究中心（GCRC）接受6度头低位卧床休息12周。在此期间，运动组将在CCF独特的零重力运动模拟器（ZLS）中进行个性化的日常运动计划，旨在取代他们在自由生活期间经历的日常机械负荷刺激。将使用类似于国际空间站上的跑步机和阻力锻炼装置进行锻炼。将在卧床开始和结束时进行DXA、MRI和QCT扫描，以评估骨矿物质密度的变化、肌肉体积的变化和骨的区域变化（皮质与小梁）。还将在卧床第8周进行DXA扫描。将在卧床前和卧床后收集力量测量值，还将评估骨吸收和骨形成的尿液和血清标志物。将由注册营养师计划和监督足以维持恒定体重的膳食摄入量，并均衡摄入大量和微量营养素，GCRC医生将全天24小时提供任何医疗需求。将在卧床休息后8周内为受试者提供康复计划。拟议的实验应该提供一个明确的答案，间歇性负荷更换是否可以充分保护肌肉骨骼系统对运动不足性骨质减少和肌肉萎缩的问题，并可能打开一个新时代，在个性化的运动对策规划。

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.