Valsalva?s Maneuver - The forced expiration against a closed glottis resulting in an increase in intra-thoracic and intra-abdominal pressure which impedes venous return to heart, thus affecting arterial pressure and autonomic activity. Valsalva's maneuver (Fig. 2) is a reproducible autonomic test of baroreflex responsiveness. It allows assessment of the training effect on the sympathetic baroreflex by comparing the arterial pressure decrease during Phase II Valsalva to the increase in muscle sympathetic nervous activity (MSNA) before and after exercise. Similarly, vagal baroreflex responsiveness will be assessed by determining the change in R-R interval as a function of the change in Phase IV Valsalva arterial pressure, and compared before and after exercise.

Head-up tilt - Simulates lower body negative pressure (LBNP) via gravity, causing an increase in blood pooling in the lower extremities and a decreased blood supply to the head. Head-up tilt is a tool used to assess orthostatic tolerance.