The Hero and the Portable Oxygen Concentrator

Okay that sounds like a weird combination, but are all your characters perfect? I don't just mean in the moral way, but in the physical too. It's obvious enough that people aren't in real life, but sometimes I know even for me, it just doesn't dawn on me to incorporate some of the normal human frailties into my characters. Not even minor ones--and wow, the hero/heroin--perish the thought. But it's not a bad thought, even for the main characters. You may not want to go as far as having them on a form of life-support, or a portable oxygen concentrators, but by all means don't shy away from having them exhibit some form of physcial frailalty. It can expand their characters immensely, and even give them a degree of empathy (if that's your wish of course, you may not want to do that with the villian). We all know not to make our characters infalable in their attitudes, now it's time to realize it's worth considering not making them infalable in their physical attributes as well.