#explainer
In orbit, muscles and bones do not support the body as they do when walking and standing on Earth. Without regular loading, their condition deteriorates. Exercise helps limit these changes and prepares the crew for a return to gravity.
How to exercise without weight
The station uses resistance equipment, a treadmill with restraints and a cycle ergometer. Resistance equipment replaces the loading supplied by weights on Earth. Treadmill harnesses pull an astronaut toward the belt; otherwise each push would send them away. Aerobic work supports cardiovascular fitness.
Exercise is part of the job
Training has a scheduled place in the daily programme and combines different types of loading. It does not eliminate every effect of spaceflight or replace nutrition and health monitoring. Its purpose is to preserve safe working ability during the mission and after landing.
Why a treadmill is not enough
Endurance and resistance exercise serve different purposes. Running supports cardiovascular conditioning, while appropriately controlled resistance work exercises muscles and loads the skeleton. Programmes combine equipment and adapt to the crew. Counting minutes of movement alone would miss the question of what loading the body actually receives.
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Key points
- The station uses resistance equipment, a treadmill with restraints and a cycle ergometer.
- Training has a scheduled place in the daily programme and combines different types of loading.
- Endurance and resistance exercise serve different purposes.
Sources & further reading
- Human adaptation to spaceflight and countermeasures.
- Station operations, logistics and crew exercise.
- Free fall, orbital gravity and weightlessness.
Spaceflightpedia. (n.d.). Why do astronauts need to exercise?. Retrieved 17 October 2026, from https://spaceflightpedia.com/article/astronaut-exercise
article text — CC-BY-SA · ◉ NASA photography — public domain · ✦ AI illustration — marked, generated from sources
