I told my brother about NROL while we were on vacation last summer. He's fought some serious tendonitis type problems in his right elbow for years. He was a very competitive tennis player for a long time and the elbow problems have really curtailed his tennis, although he still plays some and he plays left-handed at times.
Anyway, in the fall, he bought NROL and started doing the workouts. He is 3 years younger than I am, but I've been amazed at his progress so far. His weights in squats are way higher than mine. My deadlifts are a bit higher, but not by much.
He suggested that the endurance work is likely impeding my progress when it comes to lifting more weight, and I think there is something in NROL about that being the case. He does some cardio and some high intensity interval training (I think), but mostly he lifts.
We're both doing the Fat Loss 2 program right now from NROL - my second time and his first. I've got a head start of 5 or so months, and yet, he's making more progress.
It's great for him, but I'm really kind of curious if it's just a natural difference between us, whether it's age (46 vs 43 - is it that big a difference), my running, or something else.