Influence Of Menstrual Cycle Phase Upon Gender Differences In Post Exercise Hypotension

Abstract

Post-exercise hypotension (PEH) may contribute to long-term adaptations related to exercise, such as improvement of hypertension. Although the magnitude of PEH seems to be unaffected by gender, the impact of menstrual cycle phase upon gender comparisons has been ignored. PURPOSE To examine central and peripheral haemodynamics regulating PEH following moderate-intensity exercise in moderately active males and females. The impact of menstrual cycle phase upon potential gender differences was examined by investigating females in three phases of their cycle. METHODS We studied 8 females (age:20±0.3 yr) during the early follicular (EF), late follicular (LF) and mid-luteal (ML) phases of the menstrual cycle and 8 males (age:21±0.7 yr) on 2 separate occasions. Central and peripheral haemodynamics were recorded via echocardiography and venous occlusion plethysmography before and for 45 min following 30 min of cycle ergometry at 80% of the lactate threshold. RESULTS Significant PEH was observed in all subjects (P < 0.05) with the magnitude of the nadir in all blood pressure variables being significantly greater (P < 0.05) in females compared to males;10±1 vs 4±1,9±1 vs 5±1, 8±1 vs 4±1 for systolic blood pressure (SBP), diastolic blood pressure (DBP) and mean arterial pressure (MAP), respectively. Blood pressure responses did not differ between tests in males, whilst females demonstrated a lower DBP and MAP throughout recovery in the EF phase compared to the LF and ML phases (P < 0.05:at 20 min post-exercise, 68±4.5 mmHg, 74±3.4 xx mmHg and 71±6.1 mmHg for DBP, and 83±2.7 mmHg, 88±3.7 mmHg and 86±5.2 mmHg for MAP, respectively). This difference resulted in a phase-by-gender interaction with DBP and MAP over the 45-min recovery being lower in females than in males in the EF phase only (P < 0.05). SBP displayed a gender-by- time interaction, indicating a different temporal pattern of recovery in each gender (P > 0.05). Cardiac output (CO) and heart rate (HR) increased transiently post-exercise and displayed gender-by-time interactions (P < 0.05). The interaction in CO indicated a greater post-exercise increase in CO in males than in females which was maintained by a larger increase in HR (26±0.3 % vs 3±3.2 %) and a smaller increase in stroke volume (4±0.2 % vs 8±6.6 %). These central haemodynamic indices were unaffected by menstrual cycle phase, whilst calf blood flow and systemic vascular resistance were unaffected by either menstrual phase or gender (P > 0.05). CONCLUSION Cardiovascular recovery from exercise appears to differ between males and females and this difference is further influenced by menstrual cycle phase.