# This is gonna hurt in the morning. (About soreness.) **URL:** \ **Category:** Factual Questions\ **Created:** [August 13, 2006, 10:53pm UTC](https://boards.straightdope.com/t/this-is-gonna-hurt-in-the-morning-about-soreness/368595 "2006-08-13T22:53:54Z")\ **Posts on this page:** 8\ **Page:** 1
**Author:** ![Wolfian](https://avatars.discourse-cdn.com/v4/letter/w/7ea924/32.png) [@Wolfian](https://boards.straightdope.com/u/Wolfian)\ **Post date:** [August 13, 2006, 10:53pm UTC](https://boards.straightdope.com/t/this-is-gonna-hurt-in-the-morning-about-soreness/368595/1 "2006-08-13T22:53:54Z")
I ran a 5K this morning and have been feeling fine, if a little tired all day. I know that when I wake up tomorrow I’ll be sore. What causes soreness and why does it usually occur after a night’s sleep? ---
**Author:** ![MelCthefirst](https://avatars.discourse-cdn.com/v4/letter/m/eada6e/32.png) [@MelCthefirst](https://boards.straightdope.com/u/MelCthefirst)\ **Post date:** [August 13, 2006, 11:31pm UTC](https://boards.straightdope.com/t/this-is-gonna-hurt-in-the-morning-about-soreness/368595/2 "2006-08-13T23:31:05Z")
I’ve discovered that the older you get, the longer it takes for the soreness to kick in. These days, for me, the second day after using the muscles is the most sore. ---
**Author:** ![ultrafilter](https://avatars.discourse-cdn.com/v4/letter/u/3d9bf3/32.png) [@ultrafilter](https://boards.straightdope.com/u/ultrafilter)\ **Post date:** [August 14, 2006, 12:49am UTC](https://boards.straightdope.com/t/this-is-gonna-hurt-in-the-morning-about-soreness/368595/3 "2006-08-14T00:49:33Z")
The keyword you’re looking for is “microtrauma”. You should be able to find something on Google with that. ---
**Author:** ![Rhubarb](https://avatars.discourse-cdn.com/v4/letter/r/59ef9b/32.png) [@Rhubarb](https://boards.straightdope.com/u/Rhubarb)\ **Post date:** [August 14, 2006, 1:01am UTC](https://boards.straightdope.com/t/this-is-gonna-hurt-in-the-morning-about-soreness/368595/4 "2006-08-14T01:01:28Z")
According to one professor in college, next-day soreness is caused by a buildup of lactic acid in the muscle tissue. I can’t explain the mechanism of it, in fact I’m surprised I remembered this much. ---
**Author:** ![ultrafilter](https://avatars.discourse-cdn.com/v4/letter/u/3d9bf3/32.png) [@ultrafilter](https://boards.straightdope.com/u/ultrafilter)\ **Post date:** [August 14, 2006, 1:04am UTC](https://boards.straightdope.com/t/this-is-gonna-hurt-in-the-morning-about-soreness/368595/5 "2006-08-14T01:04:22Z")
[QUOTE=Rhubarb] According to one professor in college, next-day soreness is caused by a buildup of lactic acid in the muscle tissue. [/QUOTE] It’s been known for a long time that lactic acid dissipates within seconds after exercise, and there’s even some recent research that suggests it’s actually a fuel source for muscular activity. ---
**Author:** ![Rhubarb](https://avatars.discourse-cdn.com/v4/letter/r/59ef9b/32.png) [@Rhubarb](https://boards.straightdope.com/u/Rhubarb)\ **Post date:** [August 14, 2006, 1:11am UTC](https://boards.straightdope.com/t/this-is-gonna-hurt-in-the-morning-about-soreness/368595/6 "2006-08-14T01:11:50Z")
[QUOTE=ultrafilter] It’s been known for a long time that lactic acid dissipates within seconds after exercise, and there’s even some recent research that suggests it’s actually a fuel source for muscular activity. [/QUOTE] Thanks for the info. It appears my professor was not up-to-date on the facts. ---
**Author:** ![Vlad\_Igor](https://avatars.discourse-cdn.com/v4/letter/v/7feea3/32.png) [@Vlad\_Igor](https://boards.straightdope.com/u/Vlad_Igor)\ **Post date:** [August 14, 2006, 1:22am UTC](https://boards.straightdope.com/t/this-is-gonna-hurt-in-the-morning-about-soreness/368595/7 "2006-08-14T01:22:05Z")
I believe that it has to do with the breakdown of muscle tissue from exertion. FWIW, I’m 43, and yesterday I did a 23-mile bike ride, non-stop. In previous years, this would have resulted in soreness and weakness for two days afterwards, but today I mowed the lawn and made several trips to the basement doing laundry without any problems. “The Day After” can get better over time, provided you’re not overdoing it to begin with. Vlad/Igor ---
**Author:** ![Scruloose](https://avatars.discourse-cdn.com/v4/letter/s/e68b1a/32.png) [@Scruloose](https://boards.straightdope.com/u/Scruloose)\ **Post date:** [August 14, 2006, 2:01am UTC](https://boards.straightdope.com/t/this-is-gonna-hurt-in-the-morning-about-soreness/368595/8 "2006-08-14T02:01:55Z")
[What causes muscle soreness.](http://www.drmirkin.com/fitness/1346.html) > [@](#): > > It takes at least eight hours to feel this type of soreness. You finish a workout and feel great; then you get up the next morning and your exercised muscles feel sore. We used to think that next-day muscle soreness is caused by a buildup of lactic acid in muscles, but now we know that lactic acid has nothing to do it. Next-day muscle soreness is caused by damage to the muscle fibers themselves. Muscle biopsies taken on the day after hard exercise show bleeding and disruption of the z-band filaments that hold muscle fibers together as they slide over each other during a contraction.