Skeletal Muscle Atrophy

The purpose of this randomized controlled trial is to determine whether daily Finnish dry sauna therapy attenuates the adverse cardiovascular, muscular, and metabolic effects of seven days of experimentally reduced physical activity in healthy adults. Participants will be randomized to one of three groups: (1) maintained habitual physical activity with daily sauna therapy, (2) reduced physical activity with daily room-temperature sauna visits (control), or (3) reduced physical activity with daily sauna therapy. Reduced physical activity will be achieved by decreasing daily step count to approximately 1,000 steps per day with the assistance of a power wheelchair. Outcome measures include vascular endothelial function, exercise tolerance, muscle protein synthesis, body composition, blood pressure, glucose regulation, and physiological responses to heat exposure. The study will determine whether passive heat therapy can serve as a practical intervention to preserve cardiometabolic health during short periods of reduced mobility.

This study aims to determine, via skeletal muscle ultrasound (US), the extent, timing and relationship between skeletal muscle mass loss and outcomes after orthotropic heart transplantation (OHT) and left ventricular assist device (LVAD) implantation amongst patients with cardiogenic shock. Advanced therapies such as OHT and VADs in the heart failure (HF) population may promote skeletal muscle mass and subsequent quality of life, but there is a lack of literature assessing muscle mass changes in HF patients before and after advanced therapies using US imaging. Therefore this observational study will provide further insight into the 1) changes in lean body mass during critical illness and 2) the feasibility of using bedside US to assess lean body mass in the inpatient setting.

The goals of our research project are to identify factors explaining inter-individual variation in responses to resistance training (RT) and the baseline determinants underlying an individual's sensitivity to respond to RT. Moreover, investigators aim to assess whether a responsiveness to RT predicts responsiveness to endurance training (ET). Thus, investigators aim to gain a deeper understanding of exercise adaptation processes. The main questions investigators aim to answer are: * Can the physiological responses of one RT intervention be extrapolated to a subsequent RT intervention? * If so, what are the mechanisms underlying differing skeletal muscle growth responses in low, and high responders of skeletal muscle hypertrophy? * If so, do the low responders of skeletal muscle growth respond more favourably when the amount of RT is increased? * Are the high, moderate, and low responders of RT also the highest, moderate, and lowest responders to ET? To examine these main research questions, high (n=30), low (n=30), and moderate (n=30) responders of skeletal muscle growth in response to RT (intervention I, NCT05874986) are reallocated into a subsequent 12-week RT intervention (intervention II) after a detraining period. A subgroup of these participants (n=10) will engage in a 6-week control period before starting the second RT period. Additionally, after intervention II, participants will participate in an ET intervention, lasting 6 weeks. In this intervention II, reallocated participants will be: * Resistance training with supervision for 12 weeks * Consuming deuterium oxide for the assessment of muscle protein synthesis * Consuming D3-3-methylhistidine for the assessment of acute muscle protein breakdown * Consuming D3-creatine for the examination of whole-body skeletal muscle mass * Providing a spot urine sample six (6) times, and urine collection for 24 hours performed twice * Providing saliva samples (30-32 in total) for the assessment of body water enrichment of deuterium * Providing a muscle biopsy four or five (4-5) times during the study * Providing a blood sample fourteen (14) times during the study * Assessed for body composition and body volume four or five times (4-5) during the study * Participating in muscle size, maximal dynamic strength and TMS measurements four or five (4-5) times during the study * Asked to answer questionnaires related to e.g. stress, physical activity, sleep, perceived exertion, and diet * Participating in recovery measurements before and after the second-to-last and the last RT bout, and once in the days between these RT bouts, consisting of six (6) body volume measurements and six (6) maximal voluntary isometric contraction (kg) tests using horizontal leg press for the assessment of neuromuscular recovery * Participating in an acute resistance exercise (RE) after the 12-week RT intervention. Furthermore, in the ET intervention, participants will be: * Participating in a familiarization session and resting electrocardiograph measurements before the intervention * Participating in endurance testing consisting of body composition, movement economy, and incremental RAMP testing before and after ET intervention * Endurance training with supervision for 6 weeks, three times a week.