PDE5 inhibitors is an enzyme that plays a key role in regulating blood flow to the penis. It breaks down cyclic GMP (cGMP), a molecule that helps relax smooth muscles and dilate blood vessels in the penis, which is essential for an erection. Blocking PDE5 increases the levels of cGMP, which in turn improves blood flow and helps with erectile function. This is the principle behind PDE5 inhibitors like sildenafil (Viagra), tadalafil (Cialis), and others. Nitric oxide plays a key role in increasing the production of cGMP in the body. When nitric oxide is produced, it activates an enzyme called guanylate cyclase, which leads to an increase in cGMP levels. This process helps to dilate blood vessels and improve blood flow. Regular physical activity, especially aerobic exercises like walking, running, or cycling, can enhance nitric oxide production.