Smaller than a Breadbox. The heart is a hollow, muscular organ that is roughly the size of a man's fist, averaging approximately 5 inches in length, 3.5 inches in width, and 2.5 inches in thickness. It weighs about 10.5 ounces in the male and 8.75 ounces in the female. Although you can't just go to a human spare-parts store to buy a new replacement body part, organ transplants take every day. Placed end to end, the blood vessels in your body would stretch almost three times around the equator.
Talk is cheap.
If you can't carry on a conversation while you're exercising, you may be training too hard. Keep on Exercising. If you are 25 pounds overweight, you have nearly 5,000 extra miles of blood vessels through which your heart must pump blood. Hit What You Aim For. Muscle is the primary target organ of aerobic training.