The most common cause of vascular obstruction is a blood clot, also known as a DVT. This type of vascular problem usually occurs in one leg (not both), and leads to swelling of the soft tissues throughout the foot and ankle. The swelling can also extend further up the leg.
The hypothalamus is a part of your brain that controls body temperature. When you exercise, your body temperature increases, causing the hypothalamus to signal the brainstem to further increase your heart rate.
The reason for increased minute ventilation during exercise is because much more oxygen and carbon dioxide are exchanged than at rest. This single metabolic fact accounts for the profound changes in not only respiration, but also in cardiac and circulatory physiology during exercise.