Unloaded Minds - How Prolonged Unloading Shapes Human Performance in Lunar Gravity
试验速览
- 阶段
- 不适用
- 状态
- 招募中
- 入组人数
- 24
- 试验地点
- 1
- 主要终点
- Muscle volume
研究概览
简要总结
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.
详细描述
The study combines two spaceflight analogues in sequence: a 14-day Unilateral Lower Limb Suspension (ULLS) protocol followed by a parabolic flight campaign simulating lunar gravity (0.16G). This design allows investigation of both the neuromuscular consequences of unloading and the acute reactivation of the system upon first weight-bearing locomotion under partial gravity.
During ULLS, participants keep one lower limb (randomized in a counterbalanced manner) unloaded continuously using a shoe with a 10-cm thick sole and short-length crutches with forearm support. The suspended limb remains in a near-straight position and swings freely from the hip during all upright and ambulatory activity. Compliance is verified daily via telephone interviews, continuous midcalf skin temperature monitoring, and accelerometer data. Fragmin 5000 IU is administered subcutaneously once daily throughout the ULLS period as thromboprophylaxis.
Following the 14-day ULLS period, participants travel to Bordeaux where they continue the ULLS protocol until initiating the first steps on a treadmill during the lunar gravity phases of a parabolic flight. Each participant is allocated 15 parabolas (~20 seconds of 0.16G each): parabolas 1-8 at 3 km/h and parabolas 9-15 at 5 km/h.
Gait analysis is performed on a treadmill at 3 and 5 km/h at baseline (pre-ULLS) and during the parabolic flight. Kinematic data (knee and ankle joint angles) are recorded bilaterally using 2D electronic goniometers (Biometrics, 500 Hz) in the frontal and sagittal planes. Ground reaction forces and spatiotemporal parameters (step and stride length, cadence, step width, gait cycle duration and variability) are recorded using plantar pressure insoles (200 Hz). All signals are synchronized to allow left/right (loaded/unloaded) differentiation.
EEG is recorded during all gait sessions using a 64-channel cap (EasyCap GmbH) with electrodes placed per the international 10-20 system (reference: FCz; ground: AFz). Data are processed in BrainVision Analyzer 2.2 using visual inspection, automated artefact rejection (gradient threshold >60 µV), ICA, and bandpass filtering (0.5-40 Hz). Cortical current density in the motor cortex (M1, Brodmann area 4) is computed using the sLORETA module.
研究设计
- 研究类型
- Interventional
- 分配方式
- Na
- 干预模型
- Single Group
- 主要目的
- Basic Science
- 盲法
- None
入排标准
- 年龄范围
- 18 Years 至 60 Years（Adult）
- 性别
- All
- 接受健康志愿者
- 是
入选标准
- •- 18-60 years of age, willing to participate
排除标准
- •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
研究组 & 干预措施
ULLS
There is only one arm, where one leg is the experimental, unloaded leg, and the other one is the control (loaded) leg
干预措施: Unilateral lower limb suspension (Behavioral)
结局指标
主要结局
Muscle volume
时间窗: Three days before the initiation of the ULLS intervention and at day 15 of unloading, for both thigh and calf muscles bilaterally.
Three days before the initiation of the ULLS intervention, and at day 15 of unloading, all participants will undergo an MRI scan to assess thigh and calf muscle size. Muscle volume will be evaluated using cross-sectional T2-weighted images acquired on a 3-Tesla MR system. Anatomical landmarks and standardized procedures will ensure that the same segment is scanned at both time points. Participants will rest in a supine position for approximately 30 minutes prior to each scan to minimize measurement interference caused by fluid shift. Images will be analysed using manual segmentation to delineate individual muscle boundaries in each cross-sectional slice; muscle volume is then calculated by summing the cross-sectional areas of the target muscles across all slices and multiplying by slice thickness.
次要结局
- Gait analysis(Gait analysis will be performed three-to-five days before the ULLS phase and during the lunar gravity phases of a parabolic flight)
- Electroencephalogram(Three-to-five days before the ULLS phase and during the lunar gravity phases of a parabolic flight, during the gait analysis tests.)
- Electromyography(Three-to-five days before the ULLS phase and during the lunar gravity phases of a parabolic flight, during the gait analysis tests.)
- Muscle function and balance(Three days before initiation of ULLS and immediately after the parabolic flight.)
- Motor unit number estimation(Three days before initiation of ULLS and immediately after the parabolic flight.)
研究者
Rodrigo Fernandez Gonzalo
PhD, Research group leader
Karolinska Institutet