The purpose of this study is to determine the safety on sauna followed by cold water bath, a common practice in many countries, 30 healthy subjects aged 40 years and older will be at the Montreal Heart Institute Prevention and Cardiac Rehabilitation centre.

To determine the safety on sauna followed by cold water bath, a common practice in many countries, 30 healthy subjects aged 40 years and older will be at the Montreal Heart Institute Prevention and Cardiac Rehabilitation centre. A recent complete evaluation will have excluded any cardiac condition. Subjects will first spend 10 minutes in a dry sauna at 85 degrees celtius. Immediately after , subjects will be immersed in a cold water bath (ICool , Australia) at a temperature of 5 degrees celtius for approximately one minute. Blood pressure , ecg , gaz exchange and thoracic impedance will be measured during sauna and cold water bath.

Principal goal of study: to determine the safety of this practice. Secondary goals of study: to measure the blood pressure response, heart rate, presence of arrythmyas, cardiac output and cerebral perfusion during both conditions.

Primary endpoint: Change in systolic blood pressure from sauna (after 10 minutes ) to cold water (after one minute).

Physiologic measurements: continuous ECG monitoring, BP measurements at every 3 minutes during sauna and at one minute in the cold bath, gaz exchange with a portable equipment (Cosmed K4), bioimpedance and cerebral perfusion with a single frontal NIRS electrode.

Inclusion Criteria:

• Healthy women and men aged 40 and older with a recent complete medical evaluation including a normal resting ECG and a normal symptom-limited treadmill exercise test.

Exclusion Criteria:

• Any cardiac condition, abnormal exercise test, hypertension, type I diabetes and presence of any medications that may affect blood pressure.