BIOLOGY | HEALTH | MEDICAL on Instagram: "When you raise your arms, your blood flow adjusts automatically to keep circulation steady and your brain well-supplied with oxygen. When you lift your arms above your head, the muscles in your shoulders and chest slightly compress nearby veins — this makes it a bit harder for blood to return to the heart. To balance this, your heart rate increases slightly and blood vessels widen (vasodilation) to keep smooth blood flow. Gravity also helps drain blood f