Lumbar Paraspinal Muscle Atrophy during Long Duration Spaceflight

Abstract

Spaceflight results in significant lumbar pain and muscle atrophy in astronauts. The rate of disc herniation is about four times greater in US astronauts than in matched controls. Muscles are vital spine stabilizers, and trunk muscle atrophy is associated with chronic back pain. Yet, it is unclear whether current countermeasures during 6‐month International Space Station (ISS) missions prevent lumbar paraspinal muscle atrophy.PURPOSETo quantify paraspinal muscle functional cross sectional area (FCSA) before, immediately after, and 30‐days after 6‐month ISS missions.METHODSTo date, complete paraspinal MRI data for three astronauts were available. FCSA was measured in four lumbar paraspinal muscles (multifidus, erector spinae, quadratus lumborum, and psoas) at lumbar vertebral level 3/4. FCSA was measured by setting a threshold to isolate lean muscle.RESULTSLong duration spaceflight produced a significant 15.1% decrease (p=0.023) in total lumbar paraspinal muscle FCSA, as compared to before flight (Table 1). Subsequently 63.3% of FCSA loss was recovered by 30‐days post flight and was not significantly different from before flight (p=0.152).imageCONCLUSIONDespite low sample size, paraspinal muscle atrophy is not prevented by current countermeasures on 6‐month ISS missions. However, recovery activities resulted in a 63% recovery 30‐days post flight. This suggests spaceflight induced back pain and disc herniation risk may be partly related to reduced dynamic trunk stability linked to atrophied lumbar paraspinal muscles.Project supported by NASA grant # NNX13AM89G (to ARH) and NSBRI through NASA NCC 9‐58 (to BRM).