Altered thermoregulation has been reported following spaceflight simulations such as water immersion and bedrest but it has never been evaluated immediately after actual spaceflight . Impaired thermoregulation may have significant impact during various spaceflight activities such as countermeasure exercise , extravehicular activity ( EVA ) , landing , and egress . It would be manifested as an increased body temperature and heart rate and decreased work capacity and endurance . In this study we evaluated the exercise responses of two crewmembers following a long duration spaceflight and measured their changes in body temperatures , skin blood flow , sweating and heat production during a mild submaximal exercise stress .