High Intensity Interval Training in Geriatrics

Inclusion Criteria: * Patients aged 65 years and older hospitalized for rehabilitation after an acute medical condition * Expected duration of the rehabilitation ≥ 2 weeks * Ability to follow instructions to perform a Timed up and Go Test * Ability to perform exercises * Willing to participate in 4 sessions of HIIT per week for 2 weeks Exclusion Criteria: * Any acute condition with tachycardia, hypotension or fever. * Abnormal cycle ergometer stress test with * significant ECG modification * decrease of more than 20 mmHg of the blood pressure with exercise * angina * ST depression at a workload \<6 METs * Inability to reach an intensity of 15/20 in the Borg's scale of perceived exertion * Any unresolved acute medical or surgical condition of the following kind: * acute heart failure * acute coronary syndrome \< 1 month * strole \< 1 month * active pericarditis / myocarditis / endocarditis * thromboembolic disease with \< 2 weeks of anticoagulation * acute infection requiring intravenous treatment * ongoing intravenous perfusion * surgery \< 2 months * recent bone fracture * Previous episode of primary cardiac arrest (ie, cardiac arrest that did not occur in the presence of an acute myocardial infarction or during a cardiac procedure). * Severe heart failure (NYHA III and IV) * Severe stenotic or regurgitant valvular disease * Uncontrolled hypertension at rest (SBP≥160mmHg, DBP≥100mmHg) * Uncontrolled dysrhythmia * Non-sustained ventricular tachycardia with exercise * Implanted defibrillator * Obstructive cardiomyopathy * Resting HR \> 100/min * Severe peripheral artery disease * Severe COPD (VEMS \< 50%) * Exercise-induced asthma * Oxygen dependency * Muscular-skeletal anomaly that may limit exercise participation * Delirium * Inability to follow instructions * Inability to consent