What is overtraining?

a. overloading the muscles too often

b. progressing through exercises too quickly

c. muscles that aren't adapting quickly enough

d. when muscles start atrophying

My answer is a. overloading the muscles too much. This is worse than not training enough because you risks injury and it will not make your muscles grow. It needs 48 hours rest before you work out again. Some who have done this only succeed in getting injured.