I have also had this problem. It happens every time I work out. Once my heart rate gets up I start to notice my hearing becomes "muffled" like I have soup cans over my ears. I can hear my own breathing inside my head. If I bend over (with my head lower than my heart) my hearing starts to return to normal but it gets muffled again when I stand. About an hour after my workout, it returns.

Today however, I had a tingling sensation in my arms and legs and felt slightly nauseous. I cut my workout short and came home after resting for a few minutes to get rid of the "gonna puke" feeling.

I am 39 yrs old, 72" tall and 195 lbs. I am in decent shape and I work out regularly. Until today it was just annoying but with the numb feeling and nausea, I am starting to get concerned.

If anyone knows what is causing this please post.

listen to my iPod on a heart pumping volume level when I work out. I don't know if you are working out in a class (with music playing loud) or not but loud noise may be the cause for imbalance. I am going to try the gym without the headphones and see if I have different results.

I have the same problem. It is very annoying and i am starting to get concerned. my muffled hearing doesn't go away for about 30 min. does anyone have an answer to this problem!!!???