Biological and Functional Markers for Precision Astronautical Biomedicine (MARS-PRE)

University of Padova, University of Bari, University of Genova, University of L'Aquila, University of Pavia, University of Trieste, Humanitas Hospital, Italy, University of Rome

In the current study the investigators will study early biomarkers of human degradation. In 10-day horizontal bed rest the investigators will enroll 10 healthy male subjects (18-30years, BMI 20-28kg/m2). Pre-, mid- and post-bed rest the investigators will perform various measurements, some of them will be invasive (blood samples and muscle biopsies), which will be carefully taken by the medical staff. The subjects will be placed in hospital rooms and have 24-hour medical supervision, adequate hygiene, nutrition, passive exercise, entertainment and visits.

Ten young male participants will undergo 10 days of horizontal bed rest. Before, during and after the investigators will monitor many biomechanical, metabolic, cardiovascular, biochemical responses. During the bed rest period there will be no interventions. subjects will be allowed to rotate freely, with no vertical stimulus of any-kind.

In each aprticipants at each time point approx 10 intact muscle fibres will be studied for their force production after 10-day bed rest. Isometric muscle fibre force (in mNewton) will be measured isometric force (Fo) in four subsequent maximal activations (pCa, 4.6; sarcomere length, 2.6 micrometers; temperature 12 degrees C) using an electrical motor with force transducer mounted on it.

Change in ability to mentally imagine/perform locomotory tasks (voxel-based network analyses) after 10-day bed rest

Change in EEG and neurocognitive tasks parameters (event related potential; P300 component during Stroop task) after 10-day bed rest

Neural cell adhesion molecule (NCAM) expression will be analysed in vastus lateralis biopsy samples at three time points.

Thigh muscle volume will be assessed by continous section obtained by 3T MRI. Muscle segmentation will done by Matlab routine.

Change in peak aerobic power (maximal oxygen consumption) will be assessed on a cycloergometer using graded load protocol.

Change in Muscle architecture will be assessed in vastus lateralis, biceps femoris, tibialis anterior, multifidus using sonography. Specifically, we will assess all three architecture parameters (pennation angle, fascicle length and thickness), however for the purspose of this outcome we hypothesize non-homogenous change throughout the whole muscles in pennation angle. The assessment will be performed before, every 2 days of bed rest and post bed rest.

Using tensiomyography we will assess contraction time and maximal discplacement in vastus lateralis, tibialis anterior, biceps femoris, multifidus muscles. We expect that contraction time will remained the same but maximal diasplacement - a measure of a muscle tone, will increase much before the changes in muscle thickness - assessed by sonography. The assessment will be performed before, every 2 days of bed rest and post bed rest.

Using electrophoresis we will assess changes in myosing heavy chains somposition in the biopsies obtained from vastus lateralis muscle before, at day 5 and post 10 days of bed rest

Maximal voluntary isometric knee extensors contraction will be measured using dnamometer set at 90 deg flexion.

Change in static and dynamic balance will be assessed by functional tests (gait assessed with Optogait system and balance assessed with Tensiometric plate-COP) after 10-day bed rest

Change in mean arterial pressure during supine-to-stand test (mmHg) will be assessed by supine to stand test, where subjects will stay 10 minutes in each position.

Inclusion Criteria: Body mass index between 20 - 28 kg/m2 male participants a healthy individual who is able to complete all the tests planned in the research protocol Exclusion Criteria: smoking; regular alcohol consumption; ferromagnetic implants; history of deep vein thrombosis with D-dimer > 500 μg·L-1; acute or chronic skeletal, neuromuscular, psychological, metabolic and cardiovascular disease conditions.

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