[dude]

Fuer die Kniebeugler drueben ein lustiges Fundstueck bei Lucho:

"And the wall-sits are just brutal. You sit as low as possible (90 degrees) and just hold it. I don't actually use a wall, the stabilization required to stand free has benefits, particularly if you use a close (~6") foot stance, and is also more difficult. If you want extra difficulty- start by standing straight up, then slowly lower yourself to a low squat (the descent should take ~30"), then jump from the low squat as high as you can... land and start lowering again. Eccentric contraction strength is often overlooked yet hugely important in running. Think downhill running."