Staying Fit in Microgravity

Have you ever dreamed of being an astronaut? Soaring high above Earth with stars in reach; floating, weightless, exploring the infinite unknown of our universe. For many of us aspiring scientists, travelling in space was one of our wildest childhood ambitions. Little did we know, living in the microgravity of space is akin to living under extreme conditions (Schneider, 2016).

As the human body adapts to living in weightlessness it undergoes deconditioning (Petersen, et al., 2016). The degenerative processes that typically occur slowly as individuals age on Earth accelerate, as without gravity the human body is not required to support itself (Schneider, 2016). This adaptive process hinders multiple human physiological systems (Schneider, 2016) leading to decreased bone mass, muscle volume, muscle strength, maximum oxygen uptake, and cardiovascular capacity, all of which make returning to life in Earth’s gravitational field onerous (Petersen, et al., 2016; Scott, Weber and Green, 2019). Nonetheless, there is hope for our cosmic aspirations as consistent in-flight exercise can act as a countermeasure to deconditioning (Petersen, et al., 2016; Schneider, 2016).

The first use of in-flight exercise was part of the National Aeronautics and Space Administration’s Apollo Program, running from 1961 to 1972 (Scott, Weber and Green, 2019). Aboard the Apollo spacecraft, crewmembers used a variable resistance rope friction device to remain active (Scott, Weber and Green, 2019). Modernly, exercise has become cardinal to microgravity countermeasures in the International Space Station (ISS), specifically for individuals completing long-duration missions (LDMs) (Scott, Weber and Green, 2019). Astronauts are now required to exercise for an average of two hours daily, six days a week (Schneider, 2016; Scott, Weber and Green, 2019). These exercise regimes have proven successful, with many ISS astronauts demonstrating little to no change in bone mass and cardiovascular capacity upon returning from LDMs (Petersen, et al., 2016). Crewmembers have exhibited significantly less relative bone mineral density changes from pre- to post-flight, compared to astronauts residing in the Mir space station, where formal exercise was not enacted (see Figure 1). These findings further demonstrate the efficacy of exercise in promoting the return of healthy astronauts from space (Sibonga, et al., 2015; Scott, Weber and Green, 2019).

Effective aerobic and resistance exercise under microgravitational conditions provides a challenge, as much of the equipment used on Earth requires human body or object weight for function (Petersen, et al., 2016). Consequently, ISS exercise equipment is designed to account for the absence of gravitational force, and to avoid transmitting any vibrations, forces, or torques to the ISS structure itself (Petersen, et al., 2016). Equipment used in the ISS includes the Advanced Resistance Exercise Device (ARED), a treadmill, and the Cycle Ergometer with Vibration Isolation and Stabilization System (CEVIS) (see Figure 2) (Scott, Weber and Green, 2019). The ARED is designed for multi-set, multi-repetition “weightlifting” (Petersen, et al., 2016), in which astronauts work against loads including 75% of the user’s body weight to account for the absence of weight in microgravity (Scott, Weber and Green, 2019). The treadmill and CEVIS allow crewmembers to perform aerobic exercise comparable to running and cycling, using harnesses and pressure bands to create ground reaction forces similar to those encountered under Earth’s gravitational force (Petersen, et al., 2016; Scott, Weber and Green, 2019).

With deconditioning in microgravity analogous to accelerated ageing on Earth, the efficacy of exercise regimes in the ISS provides a fascinating means to maintain the health of our astronauts, and also of our ageing population (Schneider, 2016). The continued study, implementation, and improvement of exercise routines and equipment in the ISS will afford our society the opportunity to improve and expand space travel. It will also contribute to our understanding of the benefits of exercise for people living on earth (Schneider, 2016).

Works Cited

Loff, S., 2019. The Apollo Missions. [online] NASA. Available at: <https://www.nasa.gov/mission_pages/apollo/missions/index.html> [Accessed 11 Jan. 2020].

Petersen, N., Jaekel, P., Rosenberger, A., Weber, T., Scott, J., Castrucci, F., Lambrecht, G., Ploutz-Snyder, L., Damann, V., Kozlovskaya, I. and Mester, J., 2016. Exercise in space: the European Space Agency approach to in-flight exercise countermeasures for long-duration missions on ISS. Extreme Physiology & Medicine, [online] 5(9). https://dx.doi.org/10.1186/s13728-016-0050-4.

Schneider, S., 2016. Exercise in Space; A Holistic Approach for the Benefit of Human Health on Earth. [online] Cologne, Germany: Springer, Cham. https://dx.doi.org/10.1007/978-3-319-29571-8.

Scott, J.P.R., Weber, T. and Green, D.A., 2019. Introduction to the Frontiers Research Topic: Optimization of Exercise Countermeasures for Human Space Flight – Lessons From Terrestrial Physiology and Operational Considerations. Frontiers in Physiology, [online] 10(173). https://dx.doi.org/10.3389/fphys.2019.00173.

Sibonga, J.D., Spector, E.R., Johnston, S.L. and Tarver, W.J., 2015. Evaluating Bone Loss in ISS Astronauts. Aerospace Medicine and Human Performance, [online] 86, pp.A38–A44. https://dx.doi.org/10.3357/amhp.ec06.2015.