Final answer:
During pregnancy, the uterus grows and exerts upward pressure on the diaphragm, leading to increased pressure on the lungs and decreased volume of breath, which can cause shortness of breath.
Step-by-step explanation:
Shortness of breath during pregnancy exercise can be attributed to increased pressure on the lungs by the diaphragm. During pregnancy, the respiratory minute volume increases notably to accommodate the increased oxygen needs of the fetus as well as the heightened maternal metabolic rate.
As the uterus grows, it exerts upward pressure on the diaphragm which can decrease the volume of each breath, leading to shortness of breath or dyspnea. Later in pregnancy, a process known as lightening occurs where the pelvis becomes more elastic and the fetus descends, often ameliorating this condition. Breathing is a complex process involving pressure changes facilitated by the contraction and relaxation of the diaphragm and other muscles. Any disruption in the pressures or muscle function, as can occur in pregnancy, may lead to difficulty breathing.