When I bend over I get an instant sharp pain in either my upper chest area or stomach. It reminds me of a charlie horse. It goes away on its own whether I've straightened up or not. Do you know what might be causing this?
This could be related to acid reflux, since bending over can cause the stomach contents to wash up your throat a bit, and the acidic content of it can cause pain. It's important, though, not to make an assumption. It sounds like this has been going on for some time, so if it continues or worsens, you should see your doctor for an evaluation. There are many medications and other treatments that can helpful if it is being caused by acid reflux.
Here's some information for you that might be helpful:
Symptoms of Acid Reflux
Tips for Exercising with Acid Reflux