['This study was designed to test the hypothesis that aerobic exercise training of the elderly will increase aerobic fitness without compromising orthostatic tolerance (OT).', "Eight healthy sedentary volunteers (67.0±1.7 years old, 4 women) participated in 1-year of endurance exercise training (stationary bicycle and/or treadmill) program at the individuals' 65%-75% of peak heart rate (HRpeak). Peak O2 uptake (VO2peak) and HRpeak were determined by a maximal exercise stress test using a bicycle ergometer. Carotid baroreceptor reflex (CBR) control of HR and mean arterial pressure (MAP) were assessed by a neck pressure-neck suction (NP/NS) protocol. Each subject's maximal gain (Gmax), or sensitivity, of the CBR function curves were derived from fitting their reflex HR and MAP responses to the corresponding NP/NS stimuli using a logistic function curve. The subjects' OT was assessed using lower-body negative pressure (LBNP) graded to -50 mmHg; the sum of the product of LBNP intensity and time (mmHg•min) was calculated as the cumulative stress index (CSI).", 'Training increased VO2peak (before vs after: 22.8±0.92 vs 27.9±1.33 ml/min/kg, P < 0.01) and HRpeak (154±4 vs 159±3 beats/min, P < 0.02); and decreased resting HR (65±5 vs 59±5 beats/min, P < 0.02) and MAP (99±2 vs 87±2 mmHg, P < 0.05). CBR stimulus-response curves identified a leftward shift with an increase in CBR-HR Gmax (from -0.13±0.02 to -0.27±0.04 bpm/mmHg, P = 0.01). CSI was increased from 767±68 mmHg•min pre-training to 946±44 mmHg•min post-training (P < 0.05).'] Does aerobic Exercise Training improve Orthostatic Tolerance in Aging Humans?