Prehabilitative Exercise Prior to Immobilization

Inclusion Criteria: * Age: Between 20-35 years old or between 65-85 years old. * BMI: Between 18.5 and 35 kg/m2. * Healthy and well, with normal dietary habits (not vegan). Exclusion Criteria: * More than one muscle biopsy previously taken from both vastus lateralis muscles. * Smoking. * Pregnancy. * Past or present substance or alcohol abuse. * Medical/surgical conditions that are assessed to affect protein synthesis or the participant's involvement in the trial. * Knee pain that could affect the completion of the training intervention. * High intake of supplements that increase the risk of bleeding during muscle biopsy (such as fish oil and ginger). * Participation in regular strength training within the past year. * Regular participation in structured sports. * Current use of blood-thinning medication. * Previous participation in trials involving oral intake of heavy water. * Metal in the body preventing MRI scanning. * For the older group, not having gone through menopause, and for the younger group, not having a regular menstrual cycle.