this was my first day of endurance so likewise i chose chest and alts to start, my max is about 225 on the bench but i have major problems just getting 105 up 15 times(I was shooting for 20)...is this because i have weak slow twitch muscles or what? I don't want to get unmotivated and was wondering if I should drop in weight so I can get 20 reps or stay at 15 and just failure a couple reps with the same weight...