Many years ago, probably in the early 90's, I read an article by a bodybuilder named JJ Marsh, who had massively ripped legs. He was a bodybuilder who claimed his legs were a weak point until he started training them 3 times a week and turned them into a strong point. I experimented with 3 times a week training (squats) with my legs, and sure enough, they exploded with growth. If I recall correctly, I put on close to 2" of solid muscle on my quads one in about 6 months without any change in diet. I figured if it worked with legs, it might work with other body parts. Sadly, my experiment with other body parts didn't give me any decent results. But for quads and hamstrings, 3 times a week squats actually worked amazingly well. Mentally, it was tough, because although I loved the results of my squatting sessions, I hated my actual leg workouts, because squats was an exercise I always felt uncomfortable doing due to its affect on my body after a hard set. Many times it brings a feeling of nausea. Something I never felt with any other exercise for any other bodypart.