every gym has one of these and everyone uses this machine but because this is a fixed resistance machine we think we just need to lay down and move as much weight as possible. that is not the case. there are a few factors you should keep in mind, first, you should think of your knee health. your knee is a hinge joint and when you point your toes outward or inward, you are putting a lot of pressure on them, and second, your back is prone to injury if you do not position yourself correctly especially when the weight is getting heavier and rep range is coming down. as the hamstring become tired, for you to bring the leg up, you might use the hip flexors, which brings the hip up off the machine if you notice, and since the main hip flexor goes all the way to your spine, it can cause injury to your back. to target the three muscles of the hamstring area, biceps femoris, semitendinosus, and semimembranosus, you should not rotate your legs but change the degree between your legs. also, it is not a bad thing to use the glutes in this workout since glutes are the synergist muscles or fixators to your hamstring which means they help stabilize them and move them properly.