Image by andycarvin via Flickr
Ok, I know there are some things that we just don’t talk about in the running community. Many guys don’t like to admit that their nipples hurt after running…. And go on hurting them without even asking for advice. Wait, what?
Yes it’s true. If you have any doubt, go to the finish line of a marathon and wait. Cances are good that you’ll see someone with blood on their shirt. At a larger marthon, you will see several people, especially later in the race. Some people look like they’ve been shot. Sorry for the graphic image 
I’ve never bled, but can tell it’s uncomfortable and the last thing you want to be thinking about on a long run.
There are several factors that cause this… the fit of the shirt, material it’s made out of, running gait, upper body movement, and duration can make your favorite shirt feel like sandpaper. You may hear rumors of using band-aids, vasalene, or Body-Glide… but I’ll tell you the best solution I’ve found. Nip Guards. I use them for every run longer than 1 hour.
- NipGuards save your… Nips.
These come in packs of 10 (for $8.95) and I order 3 of them at a time. With two circular, padded coverings that minimize friction. Even with a hairy chest, no worries with these (and a reason a guy like me avoids bandaids).
I had a friend that insisted they would come off when he’d sweat. Turns out… he didn’t read the instructions. When you apply them, you should stick them, then turn them a little. This will create a better bond. I’ve never lost one :)
One last note: it’s no secret how much I love Amazon! but the ones listed there are almost twice the price. I would suggest ordering directly from the nipguards site at www.nipguards.com
I'm The Running Mike, a triathlon coach, running coach, and endurance athlete that likes to run, bike, and swim. 
Thank you, Mike, for your public service announcement! One more factor is the amount of salt in one’s perspiration. For example, consuming more electrolytes during an endurance run or walk will increase the likelihood of nipple irritation.