I am a 53 y.o. caucasion female that works out everyday (stretches, ball, weights, treadmill, elliptical), I weigh 132 lbs. recently I have been having a hard time finishing my routine on the treadmill and feeling tired. I seem to get overly hot on the treadmill and feel as though my heart might be beating differently. I am also a hyperthyroid patient should I worry, I do have an appt. w a cardio doc on the 28th