Tuesday, January 26, 2010

Marathons make your muscles old

This is - or should be somewhat disturbing.

Shorter telomere length is proposed as a marker for biological aging. They are also associated with more cancers.

Again a danger to chronic cardio

Skeletal muscle telomere length in healthy, experienced, endurance runners


Measuring the DNA telomere length of skeletal muscle in experienced endurance runners may contribute to our understanding of the effects of chronic exposure to endurance exercise on skeletal muscle. This study compared the minimum terminal restriction fragment (TRF) length in the vastus lateralis muscle of 18 experienced endurance runners (mean age: 42 ± 7 years) to those of 19 sedentary individuals (mean age: 39 ± 10 years). The runners had covered almost 50,000 km in training and racing over 15 years. Minimum TRF lengths measured in the muscle of both groups were similar (P = 0.805) and within the normal range. Minimum TRF length in the runners, however, was inversely related to their years spent running (r = −0.63, P = 0.007) and hours spent training (r = −0.52, P = 0.035). Therefore, since exposure to endurance running may influence minimum TRF length, and by implication, the proliferative potential of the satellite cells, chronic endurance running may be seen as a stressor to skeletal muscle.


darwinstable said...

Wow this is scary. Good post!

Drs. Cynthia and David said...

Not quite. It happens to weight lifters too - the heavier the load, the shorter the telomeres. See http://www.ncbi.nlm.nih.gov/pubmed/18091019

There are a ton of papers talking about satelite cells that can differentiate into muscle cells, and thereby regenerate damaged muscle. They presumably will have "normal" length telomeres, at least until too many replication cycles have occurred. So presumably what these studies indicate is that overtraining/chronic muscle damage can outstrip your ability to repair and regenerate the muscle. see e.g., http://www.ncbi.nlm.nih.gov/pubmed/12972872 and http://jcs.biologists.org/cgi/content/full/121/18/2975

Interesting stuff, so thanks.


Drs. Cynthia and David said...

Oh, and longer telomeres are associated with cancer, at least the kind that doesn't die on its own.

Marc said...

My own "observational speculation" might just have some scientific back up ;-) Thanks for sharing this..it makes a lot of sense to me on a "gut" level too.


John Sifferman said...

Well that's one more logical explanation about why runners are plagued with musculoskeletal injuries. Surely, excessive impact is the culprit. I wonder if the results would be different had the test group included barefoot or minimalist footwear runners, too.

mudbeard said...

The experienced runners are probably on a diet higher in carbs.

High carb diets are also known to shorten telomere length.

Any data on diet in the full research paper? Are the results compensated for this?

LauraK said...

The link for the source article isn't working. It would be nice to see the research that backs this up.

It sounds pretty common sense though that if you beat yourself up (doing any form of exercise) and don't allow proper rest and recovery, your body will suffer for it.

Were the subjects "healthy" in terms of not suffering many overuse injuries or just generally healthy? If they suffer many overuse injuries it seems likely they aren't allowing for adequate rest.