cycling fans have begun painting the chemical structure of lactic acid on roads when races are on. But it turns out that ...

What is lactic acid and lactate? For starters ... “The issue is that when you move lactate around, it moves hydrogen ions ...

So you been sprinting, Lily? Just a bit of cramp? So that's the lactic acid building up. When an athlete does too much or runs too vigorously, not enough oxygen can be delivered to the muscles.