The effects of thigh muscle strength physical activity and menstrual cycle on the orthostatic tolerance in young adult women

2002 Fiscal Year Final Research Report Summary

• Project/Area Number: 13680069
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Single-year Grants
• Section: 一般
• Research Field: 体育学
• Research Institution: Osaka International University (2002); Osaka International University for Woman (2001)
• Principal Investigator: HIRATA Mari Osaka International University, Faculty of Human Science, Professor, 人間科学部, 教授 (90173244)
• Co-Investigator(Kenkyū-buntansha): INOUE Yoshimitsu Osaka International University, Faculty of Human Science, Professor, 人間科学部, 教授 (70144566)
• Project Period (FY): 2001 – 2002
• Keywords: Young women / Bleed pressure regulation / Postural change / Thigh muscle strength

Research Abstract

We examined the relationship between the orthostatic tolerance to 60° head ? up tilt of 10 minutes and three factors - maximum thigh muscle strength, maximum aerobic power and body size - in 32 young women.
Using the relative change in the thoracic impedance upon standing, impedance being an indicator of blood volume, the subjects were divided into three groups : one group of 17 had significant decrease in blood volume (called the decrease group) ; the second group of 10 showed a decrease in blood volume followed by recovery starting after the first one minute (called the recovery group) ; the third group of 5 had a minor change of blood volume (the mildly affected group). Most of the women with strong thigh muscle were classified in the recovery group, the members of which tended to have larger body size and higher thigh muscle strength.
No difference in blood pressure in the supine position was recorded among the three groups. Women in the decrease group and the mildly affected group h ad a tendency to have higher blood pressure in the upright position than the supine position. In the recovery group, however, blood pressure was lower in the upright position than the supine position, and the relative changes in the diastolic and mean blood pressure upon standing were significantly less than those of the other two groups. Thigh muscle strength had a negative correlation with relative changes in both the diastolic and mean blood pressure in the supine position. Women with strong thigh muscle tended to have lower blood pressure in the upright position than the supine position. These results suggest that the change in blood pressure upon standing for 10 minutes depends on the change in blood volume in the chest, which happens within 1 minute of changing position. The constriction of the stronger antigravity muscle increases significantly the venous return just after standing ; but upon standing, it seems to influence blood pressure regulation mediated by the cardiopulmonary receptor, causing decrease in blood pressure.
The maximum aerobic power had no relationship with changes in blood pressure in the upright position.