Why do muscles ache days after a workout, instead of right away?

Sports scientists attribute the phenomenon to what they call “delayed onset muscle soreness,” and  involves not just pain but also “loss of strength and range of motion in the affected area,” said Dr. Scott Sailor, a professor of kinesiology at Fresno State University in Fresno, Calif., and the president of the National Athletic Trainers’ Association, The New York Times reports.

One reason: Strenuous workouts can cause multiple slight tears to the muscle tissue, after which a variety of cells and substances migrate to these muscles to help them start healing.

So how do you treat such pain?

“Various treatments have been attempted over the years,” said Sailor, including massage, icing, and anti-inflammatory painkillers. “At best, they have decreased the perception of pain,” he said, but only temporarily.

No treatment yet has been shown to reduce the length of time that muscles remain sore and weak.