Unloaded Minds - How Prolonged Unloading Shapes Human Performance in Lunar Gravity
Recruiting now · Not applicable
Conditions studied: Unilateral Lower Limb Suspension (Simulated Microgravity)
In brief
During spaceflight and lunar missions, reduced gravitational loading causes the muscles and nervous system to decondition rapidly. While muscle wasting is well documented, much less is known about how the brain and spinal cord adapt to the absence of normal mechanical loading - and how these central changes interact with muscle deterioration to impair movement control. This study investigates how two weeks of simulated lower limb unloading affects the brain's movement programs (motor engrams), the functional connection between nerves and muscles, and overall movement quality. Healthy participants undergo 14 days of Unilateral Lower Limb Suspension (ULLS), a model in which one leg is kept unloaded using a raised shoe and crutches while the other leg functions normally. After the unloading period, participants travel to Bordeaux, France, where they walk on a treadmill for the first time - in lunar gravity - during a parabolic flight. Before and after the unloading period, participants are assessed with MRI (muscle size), force plate tests (jump performance and balance), nerve stimulation (number of functional motor units), and treadmill gait analysis combining brain activity (EEG), muscle activity (EMG), joint movement, and plantar pressure measurements. The same gait analysis is repeated during the parabolic flight under lunar gravity (0.16G). The results will shed light on how the brain and muscles adapt to disuse and reactivate under partial gravity - with direct relevance to astronaut safety and rehabilitation, as well as clinical conditions involving prolonged limb immobilization.
Key facts
- Study ID
- NCT07607340
- Run by
- Karolinska Institutet
- People needed
- 24
- Starts
- 2026-05-01
- Expected to finish
- 2029-03-31
- Last updated by the study team
- 2026-05-26
Who can join
Age: 18 and older, up to 60. Sex: any. Healthy volunteers: accepted.
You may qualify if…
- 18-60 years of age, willing to participate
You may not qualify if…
- high activity level according to the GLTEQ
- contraindications to exercise
- pregnancy
- contraindications to MRI
- active cardiovascular disease
- cerebrovascular disease including previous stroke
- aneurysm (large vessels or intracranial)
- pulmonary disease including pulmonary hypertension or COPD
- metabolic diseases (including: hyper/hypoparathyroidism, hyper/hypothyroidism, Cushing's disease, type 1 or type 2 diabetes)
- active inflammatory bowel disease
- kidney disease
- malignancy
- recent steroid treatment (within the past 6 months), or hormone replacement therapy
- coagulation disorders
- musculoskeletal or neurological diseases
- diseases requiring long-term medication, including statin therapy
- smoking
Where it is running
- Karolinska Institutet — Huddinge, Stockholm County, Sweden (enrolling)
Full record on ClinicalTrials.gov
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