Lactic Acid is Not Making You Sore. Don’t Focus on “Flushing” It
The idea that in order to reduce soreness after a marathon, you have to flush out all the lactic acid in your system is, as Cane bluntly states, “horeshit.”
Lactic acid is a by-product your muscles produce during intense exercise. Yes, it’s the painful stuff you feel in the middle of a hard-effort creeping in to your legs as you push to the end of the workout. But, according to Cane, even if you lie down at right at the end of a marathon and don’t move, studies show the lactic acid disappears or is greatly reduced within a few hours.
Which means stretching won’t help. And, in fact, might make things worse. The next-morning soreness keeping you stuck in bed is from “micro-traumas” in the tissue, ones that need to heal before the pain goes away, Cane says. The best way to heal them is time. Stretching the damaged muscles may just aggravate the healing tissue more.
“I’m not saying stretching is always bad,” Can says. He encourages it if you need to improve your range of motion during training. “But in terms of it’s effectiveness in reducing post-marathon soreness, there is no evidence.”