Short Arm Human Centrifuge Therapeutic Training and Rehabilitation (GRACER1)

The patients will be randomly assigned to the short arm human centrifuge training (SAHC intervention), standard of care (SOC training) or a passive control. The SAHC intervention consists of 3 sessions per week. The session duration is 1 hour. The intervention will last 3 months. Aiming to estimate the minimum number of participants required for obtaining reliable results, the investigators performed power analysis. It was conducted in g-power 3.1 to determine a sufficient sample size using an alpha of 0.05, a power of 0.80, and a medium effect size (f = 0.21). Based on the aforementioned assumptions, a total sample size of 26 participants per group was computed. The passive control group will abstain from any exercise. Initially, there will be one session serving as an evaluation and familiarization of the SAHC group participants on the centrifuge. Its aim besides familiarization will be also to individually assess the optimal according to the participant's cardiovascular functioning with cardiac output (CO), stroke volume (SV) mean arterial pressure (MAP) diastolic blood pressure (DBP), systolic blood pressure (SBP), and heart rate (HR). These criteria are monitored at each training session and are used to dynamically adapt the intervention intensity. More specifically, after 6 training sessions (2 weeks), the centrifugation load will be increased and considering the cardiovascular criteria, centrifugation will be combined with either aerobic exercise (through an ergometer) or resistance training through elastic training bands. Further verification of the dynamic configuration of the intervention will be provided by the electroencephalographic (EEG) assessment. More specifically, resting state EEG (eyes open \& closed condition, lying in horizontal position) and centrifugation in three different intensities, mild (corresponding to 0.5,0.7, and 1 g), medium (corresponding to 1.2 and 1.5 g) and high intensity (corresponding to 1.7 and 2 g). Functional connectivity and cortical-network features derived from graph theory will be used by deep learning algorithms (convolutional neural networks) in order to define the optimal centrifuge training. A set of core outcomes as described below will be collected at the following experimental time instances: a) baseline, b) after 4 weeks, c) 8 weeks, d) 3 months, e) 6-month follow-up, g) 12-month follow-up. The outcomes will be collected across the domains of body structure and function, activity, and participation as classified by the world health organization international classification of functioning (ICF), disability and health. The primary outcomes are the following: 1. A set of cardiovascular biosignal sensors described above, 2. Electroencephalographic (EEG) recordings, 3. The functional gait assessment (FGA) and 4. The functioning differences assessed by changes in summary ordinal score on the short physical performance battery (SPPB). The battery consists of three tests: balance, gait ability and leg strength. The score for each test is given in categorical modality (0-4) based on run time intervals, and the total score will range from 0 (worst) to 12 points (best). The SPPB has been shown to be a valid instrument for screening frailty and predicting disability, institutionalization and mortality. A total score of less than 10 points indicates frailty and a high risk of disability and falls. 1 point change in the total score has demonstrated to be of clinical relevance. More primary outcomes include other measures of gaze and postural stability, fatigue, and functional mobility, isokinetic strength and muscle oxygen consumption. Additionally, a set of biomarkers in blood and urine will be collected.