Muscle Atrophy During Long Duration Bed Rest

Previous space flight testing demonstrated that even eight days of space flight can result in significant muscle atrophy ( 3 ) . Extended duration space flight is important for the economical and practical utilization of space. The loss of muscle mass during space flight is a medical concern for long duration flights to the planets or extended stays aboard space stations. Understanding the extent and temporal relationships of muscle loss is important for the development of effective space flight countermeasures and rehabilitation schemes in clinical situations where musculoskeletal unloading is a component. A number of bed rest studies were conducted by the Johnson Space Center over a number of years, primarily to examine disuse bone loss. As a secondary objective of these studies, several parameters of muscle loss and performance were examined. The results of these measurements in eight subjects, including MRI volume changes in some subjects, have been published (2). The purpose of this paper is to report our attempts to fit this muscle loss data including additional bed rest data not previously published to a mathematical function relating length of bed rest and muscle loss.