These were the machines that everyone back in the day said were responsible for Jeff King's quad sweep.
We called them the "duck press"...no idea why...maybe they were good for squashing water fowl...
I think I posted a link to an interview with Jeff King. In it he said that front squats
were responsible for his quad development (he forgot to mention Mom and Dad
).
I would never use that leg press machine I posed a picture of. Something about
pressing heavy weights with your heart and head upside down. I think the 'internal'
pressure in that position is not good. Had a guy blow a blood vessel in his eye ball
using that machine.
It has been a long time since I have seen one of these machines in a gym. Tell you
something? If memory serves, the original Golds had one, or was it when they
moved to Santa Monica? Memory fuzzy here. I remember seeing Mike Mentzer using
one and Arnold, but it could have been a memory of a foto I saw. (Getting old sucks.)
I think Emeric posted something about this, except he referenced the 45 deg.
leg press machine as another example.
Now, I have been using the a duck like stance when I do leg presses. Easier on the
hips and low back. Still constant tension, not locking out. Great burn, better than
squats. And for squats now, my feet now are wider and I go all the way down and
3/4 of the way (YouTube is good for something) , constant tension on the quads
and now I can pretty much squat pain free in the lower back and hips, albeit with
lighter weighs.. And when pain did occur, it came the next day . . . weird. May it
was rocking the hips forward at the top of the movement (standing). Who knows.
Maybe this will help the OP.