Thanks for the replies. I'm refreshing the thread after all this time since though I appreciate the answers, I think that my question was misunderstood. When I ask about weakness being caused, I'm wondering if it's possible if the muscles per se might be in top working order, but might not be able to function because of psychological issues in a very acute sense. What I mean by this is, is it possible that a person might be very weak, have some sort of breakthrough/realization, and then be able to exhibit normal strength within minutes. I'm wondering if a person can go to bed after having been weak for years, and wake up with strength and vigor, irrespective of building muscle or conditioning. In other words, I'm speculating about a psychogenic weakness in the absence of muscle weakness.