Assessing Crewmember Musculoskeletal Health with Long-Duration Spaceflight

Author: Katelyn Greene, BS, Graduate Student, Virginia Tech, Wake Forest University Center for Injury Biomechanics

Abstract Background: Astronauts on long-duration spaceflight missions (6-months or longer) are susceptible to musculoskeletal alterations that persist even after return to Earth-normal gravity. Vertebral bone deterioration accompanied by muscle atrophy may elevate injury risk. As we step towards deep space exploratory missions, it is crucial that we better understand the impact of extended microgravity on human health, both during mission and upon return to normal gravity.

Abstract Objectives:
This team investigates skeletal degradation and muscle morphology changes from pre-flight to post-flight using quantitative computed tomography (qCT) and magnetic resonance imaging (MRI) of crewmembers on International Space Station missions. The measurements are integrated into computational models, which simulate extreme conditions such as spacecraft landing to quantify vertebral strength and injury risk.

Abstract Methods:
The study will ultimately include 31 pre- and post-flight crewmember biomedical images on previous and upcoming 4+ month missions and are obtained from the National Aeronautics and Space Administration. Our image processing software and custom algorithms collect vertebral geometry and musculoskeletal health metrics including muscle volume, muscle cross-sectional area, bone cortical thickness, and bone mineral density. These measurements are used to adjust the geometry and material properties of computational human body models to match crewmember anatomy. The models are evaluated under various loading conditions to quantify injury risk.

Abstract Results: This study is ongoing; therefore, results are currently limited to muscle size data from previous missions. In the lumbar spine, we found statistically significant decreases in the total muscle volume (mean: 5.1 ±4.2%), quadratus lumborum (9.5 ±2.0%), and paraspinal muscles (5.3 ±1.0%). Surprisingly, in the cervical spine, we found significant increases in the cross-sectional areas of the trapezius (25.1 ±9.9%), semispinalis capitis (11.5 ±4.4%), sternocleidomastoid (9.0 ±2.3%), and rhomboid minor (23.1 ±11.7%). Once the entire imaging dataset is available, we will collect additional musculoskeletal measures and integrate them into the computational models.

Abstract Conclusions: This research better characterizes how prolonged microgravity influences musculoskeletal degradation around the vertebral column. With this insight, we can assess injury risk for crewmembers after return to Earth-normal gravity. It is crucial that we understand these physiological changes to improve the efficacy of in-flight countermeasures and mitigate injury on upcoming missions to Mars and beyond to interstellar space. Acknowledgments: NASA-NNX16AP89G