Health & wellness

The lactic acid myth

photos by iStock

A common misconception is that an excess level of lactic acid buildup in the muscles causes fatigue and soreness the day after a workout.

Lactic acid is a byproduct from the body burning carbohydrates during exercise. The harder you work, the more lactic acid you produce, said Dain LaRoche, an associate professor of exercise science at the University of New Hampshire.


But within 45 minutes, lactic acid levels return to normal, LaRoche said. “Which means it cannot be responsible for the pain and discomfort you have a day or two after exercise,” he said.

Exercise — lengthening and especially contracting muscles — damages the muscle cells, creating microscopic tears that are believed to cause the pain and soreness felt a day or two later.

Get The Weekender in your inbox:
The Globe's top picks for what to see and do each weekend, in Boston and beyond.
Thank you for signing up! Sign up for more newsletters here

LaRoche and other exercise specialists said post-exercise soreness is also triggered by inflammation and the release of chemicals such as histamine, which causes fluid to accumulate, producing swelling and pain.

“It has absolutely nothing to do with lactic acid,” LaRoche said.


Loading comments...
Real journalists. Real journalism. Subscribe to The Boston Globe today.
You're reading  1 of 5 free articles.
Get UNLIMITED access for only 99¢ per week Subscribe Now >
You're reading1 of 5 free articles.Keep scrolling to see more articles recomended for you Subscribe now
We hope you've enjoyed your 5 free articles.
Continue reading by subscribing to for just 99¢.
 Already a member? Log in Home
Subscriber Log In

We hope you've enjoyed your 5 free articles'

Stay informed with unlimited access to Boston’s trusted news source.

  • High-quality journalism from the region’s largest newsroom
  • Convenient access across all of your devices
  • Today’s Headlines daily newsletter
  • Subscriber-only access to exclusive offers, events, contests, eBooks, and more
  • Less than 25¢ a week
Marketing image of
Marketing image of