How Long Rather Than How Hard ....

....  may determine your immune response to exercise. Hope I caught your attention for the right reasons with my heading.

A 2 hour bike ride sure beats a 2 hour jam

Here's quite an interesting read, especially for those of you who just finished the marathon today.

We know exercise helps strengthen our immune system, Too much exercise weakens it. How do we know what's optimal?

Researchers compared 30 minutes of moderate treadmill running, 30 minutes of intense running (when maintaining a conversation while running is difficult), 120 minutes of moderate running and of course a control group with no exercise.

This is a very interesting study as researchers administered diphenylcyclopropenone (DPCP), which is a chemical through a patch on subjects' lower back. The response on the back is redness and skin thickening which is then measured. This is very different from previous other immune function studies which use animals or measure certain blood markers or saliva.

Results? A long duration of exercise (120 minutes) causes a temporary weakening of immune function. Surprisingly, the 30 minutes short bout of intense exercise did not weaken immune function.

Other questions remain. How would a two hour bike ride (which is less stressful on the body) compare to a two hour long run? Will your overall fitness matter? If you're used to running two hours every weekend, will the two hour run still weaken your immune system?

Many questions need to be answered. However, I don't think we should oversimplify the takeaway message that it is how long rather than how hard that may affect our immune response to exercise.

So those of you who've run the full distance this morning, all the more you need to rest well.

Reference

Diment DC, Forted MB et al (2014). Exercise Intensity And Duration Effects On In Vivo Immunity. Med Sci Sp Ex. DOI: 10.1249/MSS.0000000000000562.