Many jumpers do olympic squats.
And in an olympic squat you’re not supposed to sit back as if you were sitting on a chair.
In fact ol.lifters does not seem to worry too much about the line from toes to knees.
https://www.google.no/imgres?q=olympic+squat&um=1&hl=no&client=firefox-a&sa=N&rls=org.mozilla:nb-NO:official&biw=1238&bih=691&tbm=isch&tbnid=qs-Ns-Sy4NIiHM:&imgrefurl=https://www.dynamic-eleiko.com/sportivny/library/farticles015.html&docid=ggWZPLlH8CBTXM&imgurl=https://www.dynamic-eleiko.com/sportivny/images/shoes/Snatch_with_very_low_squat_2.jpg&w=479&h=480&ei=UHbOTo7QGYOCOqi23acP&zoom=1&iact=rc&dur=306&sig=115508214025298257004&page=2&tbnh=144&tbnw=144&start=16&ndsp=18&ved=1t:429,r:0,s:16&tx=68&ty=76
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