when i do "step up's" i use a box that makes it so that my knee is higher than my hip. when i see other girls doing these at the gym their knee is either lower than the hip, or right in line with the hip. jw if it makes a difference how high the box is?

Yes, the higher the step, the harder the move will be. I know anything up to having the hip & knee lined up is OK, but I don't know about bringing the knee higher than the hip. I'd double-check the book & consider using a slightly lower step so your hip & knee are lined up, and increase your weight if that's too easy.

also, last night i increased my weight from 12lbs in each hand, to 15lbs in each hand for the T push up's. Yesterday was my first day of doing 3x10. i could not finish the last two push up's with proper form. does that mean i should go back to 12lbs? only do 8 solid push up's with heavier weight?

I think you should be doing the hardest variation you can do with good form. If you can do 8 with good form using 15 lb./hand, but you're trying to get 10 reps, then you can either switch weights mid-set, or do lower weights on a full set until you think you can do the heavier weight for the full set. Either way, T-pushups are already pretty impressive! (even without extra weight!) Rock on! :happy:

#3, i am not finding prone jackknife very challenging. i do tons and tons of these in pilates, so that could be why. i have even tried them on my elbow's. anyone have any tips on how to increase difficulty?

The only variation I've seen is to do a pike, where you raise your rear into the air & keep your legs straight, as you roll the ball closer to your head and end up with your toes on the ball. I've never tried it though, so I don't know how *much* harder it would be, but it sure looks harder.

The higher the step, the harder you're working your muscles. I prefer the knee slightly higher than the hip. Think of it as a deep squat.

I would go back to using 12 lb. dumbbells and finish the stated number of sets/reps. When the number of reps decrease, then increase the weight.

I agree, prone jackknife (a.k.a. knee tucks) are not very challenging. I do the pike version as shown in the video below. I do 3 sets of 15 reps. It's awesome!

http://www.youtube.com/watch?v=a6q7k_D6DGQ&list=PL4CE51ED9E54AA7C3&index=2&feature=plpp_video

I am FINALLy feeling ok after having knee issues for two years. so I am doing very low step ups to start. My knee is a little below my hip. If it doenst bother me after a few workouts, i may move it up. I feel like it would be easy to use bad form, and make my knee worse so id rather take it easy, and not put that pressure on the knee cap of having my knee higher than hip. if that makes sense!