Exercise is generally good for us, but new research has found that some forms of exercise provide anti-aging benefits that others don't. The research found that endurance exercise, such as running, swimming or cycling, and high intensity interval training (HIIT) has the ability to not only slow, but actually reverse cellular aging, whereas resistance exercise, like pumping iron, does not.

As we age, protective caps known as telomeres found on the ends of our chromosomes deteriorate. The shortening of these telomeres is a major molecular mechanism for cell aging, and when the telomeres become so short that they can no longer protect the DNA in the chromosome, the cells die. However, it's not a one-way street, with the protein telomerase able to combat the shortening process, and even reverse it by adding length to the telomeres. It is this reversal that a new study found could be triggered by certain forms of exercise.

A team led by Professor Ulrich Laufs from Leipzig University in Germany enlisted 266 human volunteers who were young and healthy, but previously inactive. They subjects were randomly split into four groups, with three put through different exercise regimes for a period of six months.

The first group performed endurance training in the form of continuous running, the second group did HIIT consisting of a warm up followed by alternate bouts of high intensity running and slower running, topped off with slower running for a cool down, while the third group was subjected to resistance training, which involved circuit training on eight machines, covering back extensions, crunches, pulldowns, seated rowing, seated leg curls and extensions, seated chest presses and lying leg presses. The fourth and final group acted as the control, so just continued their usual lifestyle.

Over the six-month period, the three non-control groups performed three 45-minute exercise sessions a week, with 124 of the original 266 participants completing the study. The length of the subjects' telomeres was analyzed before beginning the exercise regime and two to seven days after the final bout of exercise.

"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. Interestingly, resistance training did not exert these effects," says Professor Laufs.

Compared to the control and resistance exercise groups, the researchers say the endurance and HIIT groups saw a two- to three-fold increase in telomerase activity and a significant increase in telomere length. These are both things that previous studies have shown to be associated with healthy aging but, despite this knowledge, and while admitting the number of participants is small, the researchers say theirs is the first prospective, randomized controlled study to examine the effects of different forms of exercise on these factors.

"Physical exercise is widely recommended," says Professor Lauf. "However, prospective randomized controlled training studies are very rare because they require a great effort and there are no funding sources from industry. The numbers of participants in our study may appear small compared to large drug trials, however, to the best of our knowledge, this is the largest randomized study comparing well defined training modalities with a control group and with a long duration of six months. We hope that our project will stimulate confirmation and further studies in this field."

The researchers also admit that the study participants may have performed elements of exercise that fell outside their respective groups, but point out this would have been likely for all groups, including the control. They also say that more research needs to be done to identify the reason some kinds of exercise appear to provide cellular anti-aging benefits while others don't, but hypothesize the increase in telomerase activity and telomere length resulting from endurance and HIIT exercise may be due to these types of exercise affecting levels of nitric oxide in the blood vessels.

"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," says study co-author Dr. Christian Werner from Saarland University.

Whatever the evolutionary origins, the study provides yet another reason to get active if you want to increase your chances of living healthier for longer.

The team's research is published in the European Heart Journal.