i see dead people, i see flying pigs, i see naked women but i see no pictures of you?

am i missing something?

probably 5 reps over 4 sets, using a total of 40lbs weights either in form of barbell or dumbell.

maybe its because he said he decided to reduce the amount of reps per set and increase the total amount of sets?

see an orthopedist? i really dont think you're supposed to get sharp stabbing pains in yer leg when doin squats.

You can lose muscle mass but it's not a definite. Generally(with my minimal knowledge, this is purely a personal opinion and may or may not be accurate, take with grain of salt, sugar, etc) for the average person or someone who's looking to lift for the sake of bulking and for higher PR's it'd probably be a bad idea.

But then again, alot of people lift and do cardio on the same day, I mean look at the guys in the UFC, most of them(if not all) do both + different training routines. So it can't be all that bad.