It wouldn't be difficult at all if the optimal running technique was known before hand; I think the goal of many of these RL exercises is to either i) find a better solution than what we may have imagined or ii) confirm that our knowledge was indeed the best possible solution!

> It wouldn't be difficult at all if the optimal running technique was known before hand;

You're right, but this is a simulated environment. It means the physics in it are driven by a small set of known (and most likely deterministic) rules.

So I wonder if it would it be possible to analytically determine what is the best possible running strategy.

Correct, it wouldn't be hard to take the best known strategy and implement it perfectly. Aside from the two points you mention, it also serves as a precursor to applying RL to real levels in which we may not be so sure about the optimal strategy.