jump rope /HIIT /muscle loss cardio ?

[missyd143]

can someone tell me if you can loose the muscles of your legs by doing a certain amount of cardio? which is best to do ,,i started jumpin rope for 15 min--intervals(2min on 1min rest) is that good enuff 2 burn fat? or more minutes will start to use muscle as fuel?

 

[diamonddiceclay]

15 -20 min is best to jump rope-anything less is not good for the heart