Aerobic Exercise Training Improves Orthostatic Tolerance in Aging Humans.
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 yr old, four women) participated in 1 yr of endurance exercise training (stationary bicycle and/or treadmill) program at the individuals' 65%-75% of HRpeak. Peak O2 uptake (V˙O2peak) 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 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 neck pressure-neck suction stimuli using a logistic function curve. The subjects' OT was assessed using lower-body negative pressure (LBNP) graded to -50 mm Hg; the sum of the product of LBNP intensity and time (mm Hg·min) was calculated as the cumulative stress index.



Training increased V˙O2peak (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 bpm, P < 0.02) and decreased resting HR (65 ± 5 vs 59 ± 5 bpm, P < 0.02) and MAP (99 ± 2 vs 87 ± 2 mm Hg, 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·mm Hg, P = 0.01). Cumulative stress index was increased from 767 ± 68 mm Hg·min pretraining to 946 ± 44 mm Hg·min posttraining (P < 0.05).



Aerobic exercise training improved the aerobic fitness and OT in elderly subjects. An improved OT is likely associated with an enhanced CBR function that has been reset to better maintain cerebral perfusion and cerebral tissue oxygenation during LBNP.
1Institute of Cardiovascular and Metabolic Diseases, University of North Texas Health Science Center, Fort Worth, TX; 2Minnan Normal University, Fujian Province, CHINA; 3Department of Physical Therapy, University of North Texas Health Science Center, Fort Worth, TX; 4Shanghai University of Medicine and Health Sciences, Shanghai, CHINA; 5Department of Biostatistics and Epidemiology, University of North Texas Health Science Center, Fort Worth, TX; 6Center for Alzheimer's and Neurodegenerative Disease Research, University of North Texas Health Science Center, Fort Worth, TX; and 7Center for Geriatrics, Institute for Healthy Aging, University of North Texas Health Science Center, Fort Worth, TX.
Diqun
D
Xu
Hong
H
Wang
Shande
S
Chen
Sarah
S
Ross
Howe
H
Liu
Albert
A
Olivencia-Yurvati
Peter B
PB
Raven
Xiangrong
X
Shi
D000368:Aged; D017704:Baroreflex / Q000502:physiology; D001794:Blood Pressure / Q000502:physiology; D015444:Exercise / Q000502:physiology*; D005260:Female; D006339:Heart Rate / Q000502:physiology; D006801:Humans; D008150:Lower Body Negative Pressure; D008297:Male; D054971:Orthostatic Intolerance / Q000503:physiopathology*; D010101:Oxygen Consumption / Q000502:physiology; D010809:Physical Fitness / Q000502:physiology*