What is the best cardio to do if you are trying to maintain muscle mass?  Well studies have shown that long distance or endurance running is the worst.  If you are looking to maintain muscle mass the best cardio training is cycling which was proven in a study conducted at the University Of Tampa.  Cycling is a superior cardio exercise for maintaining muscle mass because it is a compound movement exercise.  Because cycling requires you to use hip flexion and multi-joint activation of muscles you would be using in power movements such as squats and dead lifts.  Other great carido exercises for maintaining muscle mass are sprinting and rowing.  So forget about the long distance runs and waling on an incline on the treadmill, start incorporating rowing, sprinting, and cycling into your workout routines and watch the muscle pile up.