Subject: What causes the floating sensation felt after an isometric exercise?

I recently did an exercise in my biology class in which I stood in a doorway 
and push outward on the doorframe with my arms extended with as much force as I 
could and I held it for 30 seconds. After I stepped out of the doorframe and 
relaxed my arms, I felt like they were floating upward. I thought maybe that I 
had built up a little amount of lactic acid in those muscles, which aids muscle 
contraction, and that caused the floating sensation. I have not been able to 
answer this question by means of teachers or the internet; please help!

Re: What causes the floating sensation felt after an isometric exercise?