From Martica Heaner, Ph.D., M.A., M.Ed. http://on-msn.com/9zrljR
"The average person won’t lose muscle from doing cardio and won’t burn more fat by building more muscle, mostly because one has to eat more than usual (not diet) and lift seriously heavy weights to build more muscle. And even then that person probably won’t build enough muscle to make a difference."
"You will always burn more calories the longer or harder you exercise, no matter what your intensity is. So doing cardio for only 15 minutes makes no sense unless you are short on time. Burning BOTH fat calories and carb calories can result in fat loss or pounds off the scale."