Abstract
Due to higher metabolic demands to the contracting muscles there are significant increases in cardiac output (CO) and peripheral vascular adjustments, thus resulting in an increased arterial blood pressure (BP) during exercise. In general women have higher heart rate (HR), lower stroke volume (SV) and CO compared to men even though they change in a similar fashion during exercise. In response to central hypovolemia, triggered by lower body negative pressure (LBNP), women appeared to have lower tolerance compared to men. However, how women exhibit cardiac alterations to sustained LBNP and exercise differently is unclear. PURPOSE: To investigate sex differences in cardiac decompensation in response to LBNP and exercise. METHODS: A total of 17 young adults completed the study. HR from ECG, beat to beat arterial BP from Finapres, and SV from Modelflow, were continuously measured during 5 minutes of resting baseline with and without LBNP (@-20mmHg), and 5 minutes of dynamic handgrip exercise at 35% of maximal voluntary contraction (MVC) with and without LBNP. CO and total vascular conductance (TVC) were calculated as CO=HR✕SV and TVC=CO/Mean BP, respectively. RESULTS: While both sexes significantly increased HR and mean BP from rest to exercise, women had attenuated tachycardic (Δ6.6±2.9 men vs. Δ2.3±2.7 women, p<0.05, bpm) and pressor response (Δ8.7±3.9 men vs. Δ5.0±2.9 women, p<0.05, mmHg). In response to LBNP, SV decreased and HR increased significantly with no changes in CO and mean BP in both sexes. In response to LBNP during exercise at 35% MVC, HR was elevated in both men and women with an additional Increase in HR in women (vs. @35%MVC; Δ4.1±3.7 men vs. Δ7.4±3.2 women, p<0.05, bpm) while Mean BP remained high similarly (vs. @35%MVC; Δ1.2±3.9 men vs. Δ0.7±3.5 women, mmHg). CONCLUSION: When LBNP was applied during exercise, women exhibited an augmented tachycardia while mean BP stayed elevated similarly. Women may exhibit greater cardiac decompensation when exposed to similar sustained hypovolemic stress (moderate level of LBNP, -20mmHg) during exercise.
This work is supported by National Institute of Health, National Institute of General Medical Sciences Grant (SC2GM144165 to A.K. Jensen)
Recommended Citation
Rizk, Yusuf I.; Hernandez Valadez, Daisy; Sievers, Jacob B.; Gendy, Youanaa A.; and Jensen, Areum K.
(2024)
"Sex Differences in Cardiac Decompensation Under Moderate Hypovolemic Stress During Exercise,"
International Journal of Exercise Science: Conference Proceedings: Vol. 14:
Iss.
4, Article 34.
Available at:
https://digitalcommons.wku.edu/ijesab/vol14/iss4/34
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