Ever wonder how an astronaut stays in shape out in space? It’s not as easy as following a clean diet and heading to the intergalactic gym with cosmic weights and hypertrophic sci-fi machines. That’s because, as you already know, you kinda need gravity for resistance training.
Without gravity, astronauts need to turn to some clever engineering in order to train. Training is all the more important in a shuttle in orbit around the globe because, without gravity, the threat of bone loss and muscle atrophy is significant.
In early March 2025, Johnny Kim, an astronaut with NASA, U.S. Navy officer, and physician, shared how he is preparing for his takeoff 192 days out.
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“Strength training is required for astronauts to fight bone loss and muscle atrophy in space,” Kim shared in the caption of his post. Per Cells, “Skeletal muscle atrophy in the microgravity environment is thought to be associated with changes in energy metabolism, protein metabolism, calcium ion homeostasis, myostatin levels, and apoptosis.” (1)
Leading up to a spaceflight, we have a dedicated astronaut strength, conditioning, and rehabilitation coach (ASCR).”
—Johnny Kim
The ASCR is responsible for teaching astronauts how to use the on-orbit resistive devices, — Advanced Resistive Exercise Device (ARED) — and ensure they follow an optimized strength routine, comprising mostly of compound movements with some isolation exercises. Strength training, in combination with bisphosphonate alendronate, a class of medications that help treat osteoporosis, “can prevent or attenuate group mean declines in areal bone mineral density.” (2)
The squat is probably the most common and famous compound exercise on Earth, as it is in orbit.
—Johnny Kim
How Does ARED Work?
Per Kim, “ARED uses two vacuum cylinders with pistons as the source of constant resistance. This constant resistive load can be changed from 50-600 pounds by adjusting the length of the lever arm.”
ARED works like a “small syringe,” Kim shared. “Push the plunger and cover the opening tip with your finger. If you pull back on the plunger, you will feel resistance because of the vacuum you created. Attach that plunger to a complex series of lever arms, and you will have ARED.” While Kim admitted that that is a “major simplification of clever engineering,” the concept of creating a pressure vacuum that can be manipulated to create resistance in microgravity means astronauts can continue to get out-of-this-world strong.
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References
- Liu, Y., Cao, X., Zhou, Q., Deng, C., Yang, Y., Huang, D., Luo, H., Zhang, S., Li, Y., Xu, J., & Chen, H. (2024). Mechanisms and Countermeasures for Muscle Atrophy in Microgravity. Cells, 13(24), 2120. https://doi.org/10.3390/cells13242120
- Sibonga, J., Matsumoto, T., Jones, J., Shapiro, J., Lang, T., Shackelford, L., Smith, S. M., Young, M., Keyak, J., Kohri, K., Ohshima, H., Spector, E., & LeBlanc, A. (2019). Resistive exercise in astronauts on prolonged spaceflights provides partial protection against spaceflight-induced bone loss. Bone, 128, 112037. https://doi.org/10.1016/j.bone.2019.07.013
Featured image: @jonnykimusa on Instagram
