Massive leg muscles.
Olympic speed skaters have massive legs; even smaller skaters do. Why is this so as they appear not to lift weight during their events? I think I have this solved now after noting that the skaters pull 2.5Gs in the turns. At my weight that would be 500lbs of load on the legs in turning. That load, however, is largely eccentric (negative or downward and resisted).
So, they are weight lifting after all; they are resisting negative load, one leg at a time. I would have a 500lb eccentric load on each leg if I could skate as fast as they do. What thighs I would have.
The other question is: why is their upper body so muscular since that would seem to be almost dead weight. Of course, they do a vigorous arm pump in starting, but then they place their arms behind them in a stationary pose. That upper body musculature would appear to be the result of systemic growth signaling from their leg muscles.
MGF and IGF flood the leg muscle cells from their intense activity and stem cells migrate and fuse into muscle cells. AKT is released by mechanical stress on muscle cells (through mTOR) -- yes mechanical stress induces protein synthesis. These growth factors and stem cells enter the blood stream and induce growth of other muscles through circulation, they also rescue or heal damaged organs such as the liver. There are other systemic signals delivered by the endocrine system and the sympathetic nervous system; for example, you induce proteostasis in your brain and other organs. That is why old time body builders tell you that you will get bigger lats or biceps from doing heavy squats; they did not know about systemic signaling, but they were empiricists and learned through trial and error and so discovered systemic signaling before it was understood in biology.