Posted by 
Running, swimming, cycling and other types of endurance exercise can slow cellular aging, but strength training may not, a new study suggests.
Researchers looked at how different types of exercise affected telomeres in 124 inactive, young, healthy adults.
Telomeres are protective caps on the ends of chromosomes. As you age, telomeres shorten and result in cell aging. However, an enzyme called telomerase can counteract the shortening process and even add length to the telomeres.
The study participants were randomly assigned to six months of either: endurance training (long sessions of running); high-intensity interval training (high-intensity running alternating with slower running); resistance (weight) training; or no changes in activity (the control group).
The participants’ telomere length and telomerase activity were assessed at the start of the study, and two to seven days after the final exercise session, according to the authors. The study was published Nov. 27 in the European Heart Journal.
“Our main finding is that compared to the start of the study and the control group, in volunteers who did endurance and high-intensity training, telomerase activity and telomere length increased, which are both important for cellular aging, regenerative capacity and thus, healthy aging,” said study leader Ulrich Laufs, a professor at Leipzig University in Germany. “Interestingly, resistance training did not exert these effects.”
Compared to the resistance and control groups, telomerase activity increased two- to threefold and telomere length increased significantly in the endurance and high-intensity training groups.
“The study identifies a mechanism by which endurance training — but not resistance training — improves healthy aging. It may help to design future studies on this important topic by using telomere length as indicator of ‘biological age’ in future intervention studies,” Laufs said in a journal news release.
Endurance and high-intensity training could increase telomere length and telomerase activity by affecting levels of nitric oxide in blood vessels, which produces changes in cells, the researchers theorized.
“From an evolutionary perspective, endurance and high-intensity training may mimic the advantageous traveling and fight-or-flight behavior of our ancestors better than strength training,” said study co-author Dr. Christian Werner, from Saarland University in Germany.