Two astronauts on Axiom Mission 1 spent just 17 days around Earth, yet the mission still left a measurable mark on how they experienced pain. During the flight both participants reported musculoskeletal discomfort and after landing researchers found changes in several sensory tests that probed touch, heat, repeated pain signals and the body’s own ability to dampen pain.
The study appeared in the Journal of Pain Research on December 11, 2023. Andrea K. Sauer, Marie Vigouroux, Patrick M. Dougherty, Juan Pablo Cata and Pablo M. Ingelmo followed the two commercial astronauts before launch, during their stay aboard the International Space Station, after splashdown and again three months later.
The numbers are small, but the question is important. Long before people attempt multi-month journeys deeper into space, commercial crews are already giving scientists a way to watch how the nervous system responds to weightlessness, workload, confinement and disrupted daily rhythm. Pain is part of that picture because it affects movement, sleep, concentration and willingness to keep working through physical strain.
What the crew felt during the mission
The paper says both astronauts experienced musculoskeletal pain during the flight and after landing. The symptoms were manageable rather than disabling and the two participants used anti-inflammatory medication and stretching techniques to cope while the mission was still under way. By the three-month follow-up, their overall pain levels had returned to preflight baseline.
That time course matters because it separates two different questions. One concerns the discomfort astronauts feel while they are adapting to microgravity. The other concerns whether the somatosensory system itself changes in a way that can still be measured after the spacecraft is back on Earth. The Ax-1 study tried to look at both.
The researchers also gathered questionnaire data on anxiety, pain catastrophizing, disability and the effect of pain on physical and mental health. Those scores pointed to stronger pain experiences during flight and immediately after return. The authors were careful with interpretation, because tools designed for clinics on Earth may not capture spaceflight discomfort perfectly, especially when highly trained crew members are motivated to keep working.
A related Axiom Space research page describes the project as an effort to understand how short-term microgravity changes pain sensation, biomechanics, bone physiology and the musculoskeletal system. That framing fits the mission well. A short commercial flight does not erase the basic loading problem in space, where tissues that normally work against gravity are suddenly asked to operate in a very different mechanical setting.
How the pain study was measured before, during and after flight
The investigators built the study around repeated measurements rather than a single postflight check. Data were collected pre-flight, in-flight, post-flight and again three months later. Questionnaires recorded the astronauts’ own descriptions of pain, while qualitative interviews after landing added detail about where discomfort appeared, how it changed and what strategies helped.
The more technical part of the project used quantitative sensory testing and conditioned pain modulation. Quantitative sensory testing examines how strongly a person responds to controlled touch, temperature, or repeated stimulation. Conditioned pain modulation asks whether one painful input changes the response to another, which gives researchers a window into the nervous system’s descending inhibitory control.
Those methods are already used on Earth in pain research and a broader Pain Medicine review has described conditioned pain modulation as one way to study how the body amplifies or suppresses pain signals. Bringing similar tests into a spaceflight context helps researchers move beyond general reports that astronauts hurt and toward more specific questions about which sensory pathways are shifting.
The paper also connects its design to a larger NASA Human Research Program effort to understand how spaceflight affects health and performance. Short missions cannot answer every question about deep-space travel, but they can reveal where countermeasures will be needed. If a crew’s pain regulation changes quickly in orbit, longer missions may need more careful monitoring of physical loading, exercise, sleep and recovery.
The measurement schedule also helped the team avoid a simple before-and-after story. By collecting information during the mission, immediately after return and again months later, the researchers could see that temporary discomfort and longer-lived sensory effects do not necessarily rise and fall on the same timetable.
What changed in touch, heat and pain control after landing
The study found several sensory changes rather than one simple shift. After the mission, both astronauts showed higher mechanical touch detection thresholds, which means it took stronger stimulation for them to notice light mechanical contact. The researchers said those values still remained within published normal ranges, so the result points to subtle alteration rather than obvious clinical loss of function.
The team also saw changes in heat pain thresholds, temporal pain summation and conditioned pain modulation. Temporal pain summation refers to the way repeated painful signals can build on each other. Conditioned pain modulation reflects how efficiently the nervous system can dampen incoming pain when another painful stimulus is present. In the paper, post-landing modulation looked less efficient, suggesting weaker endogenous inhibition at that stage.
A PubMed record for the study summarizes the same pattern: increased mechanical touch detection thresholds, temporal pain summation, heat pain thresholds and differences in conditioned pain modulation after the 17-day mission. The authors did not present those findings as proof of permanent injury. Instead, they described a variable response that could reflect microgravity, stress, sleep disruption, previous pain history, workload, or other factors that act together during spaceflight.
Earlier work on spaceflight pain gives context for why researchers are paying attention. A later systematic review and meta-analysis on low back pain during and after spaceflight notes that pain is common in astronauts and that evidence points to changes in discs, vertebrae and paraspinal muscles. The Ax-1 paper adds a different layer by asking how the nervous system handles incoming signals, not only how the spine or muscles are loaded.
Why a two-person commercial mission still matters
The obvious limitation is scale. Two astronauts are not enough to define a universal rule for every mission, spacecraft, or person. The study itself calls the work a proof-of-concept and the authors repeatedly say that more data are needed. Even so, space medicine often starts with small samples because access to orbit is rare and every repeated measurement from a real mission carries unusual value.
Commercial flights are especially useful because they widen the pool of people who can be studied in orbit. NASA notes that private astronaut missions are part of a broader shift toward a more active commercial economy in low Earth orbit. Those missions also create chances to test health questions in crews that may differ from traditional career astronaut corps in age, background, training history and medical profile.
The nervous system may respond to many overlapping pressures in flight: microgravity, altered sleep, stress, confinement, motion adaptation and changed physical loading. The Ax-1 results do not isolate one cause, but they do show that sensory regulation deserves a place beside bone loss, muscle atrophy and cardiovascular adaptation in discussions about future missions. A crew that feels pain differently may pace work differently, recover differently and need different countermeasures.
The encouraging part is the recovery pattern. Pain reports moved back toward baseline by three months and the paper presents the overall picture as a mostly transient effect after a short stay in orbit. For planners thinking about future commercial stations or longer exploration missions, that result is still a warning. A mission does not need to be long for pain perception to shift and the safest time to understand that shift is before crews spend far longer from Earth.
