Pregnancy-induced changes in the maximal physiological responses during swimming

Area of Science:

• Exercise Physiology
• Reproductive Physiology
• Sports Medicine

Background:

• Understanding physiological adaptations during pregnancy is crucial for exercise recommendations.
• Peak oxygen uptake (VO2 peak) is a key indicator of cardiorespiratory fitness.
• Previous research has not fully elucidated the impact of pregnancy on VO2 peak during swimming.

Purpose of the Study:

• To evaluate the effect of pregnancy on VO2 peak during tethered swimming.
• To compare swimming VO2 peak with cycle ergometry VO2 peak during pregnancy and postpartum.
• To investigate factors influencing changes in VO2 peak during pregnancy, including ventilation and hemoconcentration.

Main Methods:

• Ten pregnant women were assessed at 25 and 35 weeks of gestation, and 9-11 weeks postpartum.
• Tethered swimming and cycle ergometry tests were performed to measure VO2 peak and maximal heart rate.
• Hemoglobin concentrations, hematocrits, and plasma volume changes were analyzed.

Main Results:

• Maximal heart rates were similar for both swimming and cycling, unaffected by pregnancy.
• Cycling VO2 peak remained consistent throughout pregnancy.
• Swimming VO2 peak significantly decreased during pregnancy (25th wk: 1.64 ± 0.12 L/min; 35th wk: 1.48 ± 0.11 L/min) compared to postpartum (1.78 ± 0.14 L/min) and cycling values.
• Reduced peak ventilation correlated with decreased swimming VO2 peak during pregnancy (r = 0.864).
• Increased exercise-induced hemoconcentration was observed during pregnancy for both exercise modes.

Conclusions:

• Unlike cycling, swimming VO2 peak is significantly reduced in pregnant women.
• This reduction is primarily associated with decreased peak ventilation, not hemoconcentration.
• Pregnancy induces greater exercise-induced hemoconcentration, potentially due to altered capillary dynamics.