Resistance exercise training and the orthostatic response |
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Authors: | John P McCarthy Marcas M Bamman Janice M Yelle Adrian D LeBlanc Roger M Rowe Michael C Greenisen Stuart M C Lee Elisabeth R Spector and Suzanne M Fortney |
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Institution: | (1) NASA Johnson Space Center, Medical Life Sciences Division (SD/3) Houston, TX 77058, USA, US;(2) KRUG Life Sciences Inc., 1290 Hercules, Suite 120, Houston, TX 77058, USA, US;(3) Baylor College of Medicine, 6550 Fannin St., Houston, TX 77030, USA, US;(4) 12 North Rural Street, Chippewa Falls, WI 54729, USA, US |
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Abstract: | Resistance exercise has been suggested to increase blood volume, increase the sensitivity of the carotid baroreceptor cardiac
reflex response (BARO), and decrease leg compliance, all factors that are expected to improve orthostatic tolerance. To further
test these hypotheses, cardiovascular responses to standing and to pre-syncopal limited lower body negative pressure (LBNP)
were measured in two groups of sedentary men before and after a 12-week period of either exercise (n = 10) or no exercise (control, n = 9). Resistance exercise training consisted of nine isotonic exercises, four sets of each, 3 days per week, stressing all
major muscle groups. After exercise training, leg muscle volumes increased (P < 0.05) by 4–14%, lean body mass increased (P = 0.00) by 2.0 (0.5) kg, leg compliance and BARO were not significantly altered, and the maximal LBNP tolerated without pre-syncope
was not significantly different. Supine resting heart rate was reduced (P = 0.03) without attenuating the heart rate or blood pressure responses during the stand test or LBNP. Also, blood volume
(125I and 51Cr) and red cell mass were increased (P < 0.02) by 2.8% and 3.9%, respectively. These findings indicate that intense resistance exercise increases blood volume but
does not consistently improve orthostatic tolerance.
Accepted: 17 January 1997 |
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Keywords: | Blood volume Carotid baroreflexes Leg compliance Blood pressure Muscle mass |
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