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
Abstract
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.
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
Abstract
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.
Comments
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.
Cynthia
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.
Marc
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?
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.