Will Training Twice A Day Kill Muscle Mass?

Answering a youtube question by Michael Cassonova on his new training regime. He commented on our last video explaining he has been training calisthenics for a year now 5-6 days a week. He plans on adding a 40lbs weight vest to his workout as well as starting concurrently a 3 day a week weight lifting program. He wants to know if this will kill his muscle masshttp://www.amazedfitness.com/workout-tips/will-training-twice-a-day-kill-muscle-mass/