Punching bags toughen your knuckles for martial arts practice, boxing and more strenuous sparring workouts, but you must start slowly. Repeatedly hitting the rough surface of the punching bag with bare hands can lead to abrasions if you attack your workout too aggressively. Wear protective gear to prevent future abrasions from interrupting your workout.
Punching Bag Construction
Punching bags consist of a thick, heavy material over an inner compartment filled with sand, packed rags, water or compressed air. Columnar heavy bags have little give to them when you punch or kick them, while small teardrop-shaped speed bags typically contain an air bladder that makes them spring back when punched. Bags of every type have a textured outer covering of leather or canvas. The rough texture provides friction that helps keep your fists centered on the bag, but that roughness also contributes to abrasions on your knuckles.
Although they look and feel like burns, the superficial injuries you get from going a few rounds with a punching bag are abrasions. These scrapes are functionally identical to the "road rash" you might sustain on your knees or palms after taking a spill from a bicycle and skidding on the concrete. The repeated rubbing of your bare skin against the rough texture of the punching bag eventually wears away a portion of the protective outer layer of your skin, the epidermis. Without its outermost layer of protection, the raw, nerve-filled skin beneath feels inflamed and hot as if you'd been burned.
Treat minor abrasions at home with a thorough washing in cool water to remove any dirt or debris. If your friction burns are open, use soap with caution to avoid stinging raw skin. Over-the-counter antibiotic ointments and sprays help prevent inflamed skin from becoming infected. Take a break from the punching bag until your hands heal. While superficial abrasions rarely require a doctor's attention, if you notice deeper hand or wrist pain, speak to your doctor about the possibility of bone or tendon injuries underlying the surface injury.
Boxers wrap their hands in part to provide firm support for the bones of their hands and wrists, but they also do it to protect their skin from punching bag burns. Wrap your knuckles with tape and wear padded gloves to protect your hands as you use the punching bag. When using a speed bag, work toward greater control rather than more speed; you'll save wear on your hands and improve your technique.