Lactic acid isn’t your muscles’ foe. It can actually keep you happy, fit, and motivated, according to a study published Tuesday.

Researchers at the University of Bristol and University College London found that lactate—or lactic acid—causes the brain to release a hormone and neurotransmitter crucial for basic brain function. The hormone, called norepinephrine, helps control stress, pain, and appetite and can motivate us to get out of bed in the morning.

Most of us have experienced lactic acid buildup in our muscles—and we know it’s not fun. When we exercise, our bodies produce lactate, which is what makes our muscles burn and get fatigued. But in the brain, it’s an important energy source to keep neurons fueled. It’s also a signal to those neurons to create more of the essential motivating hormone.

“If we can regulate the release of noradrenaline—which is absolutely fundamental for brain function—then this could have important implications for the treatment of major health problems such as stress, blood pressure, pain, and depression,” says Dr. Anja Teschemacher from the University of Bristol.

Sounds like it’s time for some lactic-threshold burnouts.