No, it’s still not lactic acid — but norepinephrine is part of the fuel story
The “lactic acid” explanation of muscle soreness refuses to die. It is wrong, and it is worth restating why: lactate clears within about an hour of exercise and does not follow the 24-to-72-hour soreness curve (Miles and Clarkson (1994)). Soreness is mechanical micro-damage and inflammation. Keeping “lactic acid” as the culprit sends people chasing the wrong target.
But there is a real norepinephrine-lactate connection — pointed in the opposite direction.
Norepinephrine acts on support cells in the brain (astrocytes) to break down glycogen and release lactate as fuel for neurons (Hertz et al. (2015); Killeen, Russell, and Sergeant (2013)). In other words, norepinephrine helps supply fuel. It does not leave lactate behind as waste.
That means, if anything, a norepinephrine deficit should reduce acute lactate availability — not create an “acid” overload. This fits the broader finding that norepinephrine and lactate rise together during exercise, and that β2-adrenergic signalling increases glycogen breakdown (Jessen et al. (2020)).
So the correct statement is narrow and almost the opposite of the myth:
- Soreness is not caused by lactate.
- Norepinephrine is one of the signals that makes lactate available as fuel.
- A norepinephrine deficit would impair fuel delivery, not cause a lactic-acid build-up.
Why it matters: it replaces a folk explanation with a mechanism, and it stops an entire category of useless advice — “flush the lactic acid” — from being attached to a real problem.