Hello, I am an 81 yr.old male. 5 8 , 160 lbs. in better than good condition. I m involved with water aerobics , 1 hour, 3 x week, and swim some laps after the excersises. I m starting to experience a little shortness of breath after doing anything strenuous, and recently I have extreme weakness in my legs upon getting out of bed. Lasts about 15 seconds, but legs are very wobbly and cannot walk. What s up?