Breast disorders in men
The male breast is much smaller than its female counterpart, and it cannot produce milk. Because of this smaller size and simpler structure, breast disease is much less common in men than women. Still, men can develop important breast problems, both benign and malignant. Early detection is the key to a successful outcome, so every man should understand the basic elements of male breast disease.
Irritation of the nipple is more common than enlargement of the breast itself. Pain, redness, and even bleeding of the male nipple are fairly common complications of intense, prolonged exercise — hence the common names "jogger's" and "marathoner's" nipple. The cause is not running itself but the mechanical irritation of the runner's shirt rubbing up and down against his chest, especially in hot, humid weather.
You don't have to give up running to cure jogger's nipple. Instead, apply some petroleum jelly to your nipples before you run. Plastic Band-Aids are even better; round "spots" are particularly handy. Or simply run without a shirt when it's hot or humid.