Some people know when lifting weight in a leg press machine you may want to avoid locking out you knees at the top. This to save the joints from being crushed by the weight every rep.
Now if you are in a decent leg press machine (not a 45 degree sled) and you move slow enough to avoid cheating, slamming your knees should not be an issue. There is so much leverage at the top of a typical leg press that the weight is essentially quite light on your leg muscles. So as with all recommendations move slow enough to always be in control of the weight.
At our Ottawa personal training studio we have a specialized leg press for the job. When the double weight stacks are pinned up the foot plate is advanced. This means the end of the movement hits rubber stoppers and you cannot lockout your legs. The advantage is not having to think about it but instead just exercise intensely and let the equipment handle the ergonomics.
See in the video how the foot plate moves out and down and stops before lockout. Very natural action for your lower body muscles.
Be well, be strong,
Andrew and Tierney