These days a fair amount of scientific work is aimed at quantifying the benefits of various different approaches to exercise. The research here is an example of the type, and compares endurance training (aerobic activity) versus resistance training (to build strength). The authors looked at measures of telomerase activity and telomere length in white blood cells obtained from a few hundred volunteers who carried out different programs of training. Some groups showed greater gains than others.
This should not be taken as robust evidence for effects on aging, as firstly this is more an assessment of immune system activity than of the state of the body as a whole, and secondly telomere length is a truly terrible measure of aging. It correlates very poorly with aging in all but the largest groups. All this really tells us is that aerobic activity fires up the immune system more readily than resistance training. It is known that both aerobic and resistance exercise affect aging, and in different ways, but this study isn't the way to usefully quantify those influences.
Our DNA is organised into chromosomes in all the cells in our bodies. At the end of each chromosome is a repetitive DNA sequence, called a telomere, that caps the chromosome and protects its ends from deteriorating. As we grow older, the telomeres shorten and this is an important molecular mechanism for cell aging, which eventually leads to cell death when the telomere are no longer able to protect the chromosomal DNA. The process of telomere shortening is regulated by several proteins. Among them is the enzyme telomerase that is able to counteract the shortening process and can even add length to the telomeres.
Researchers enrolled 266 young, healthy but previously inactive volunteers and randomised them to six months of endurance training (continuous running), high intensity interval training (warm-up, followed by four bouts of high intensity running alternating with slower running, and then a final cool down of slower running), resistance training (circuit training on eight machines, including back extension, crunch, pulldown, seated rowing, seated leg curl and extension, seated chest press and lying leg press), or to an unchanged lifestyle (the control group).
The participants who were randomised to the three forms of exercise undertook three 45-minutes sessions a week, and a total of 124 completed the study. The researchers analysed telomere length and telomerase activity in white blood cells in blood taken from the volunteers at the start of the study, and two to seven days after the final bout of exercise six months later. Telomerase activity was increased two- to three-fold and telomere length was increased significantly in the endurance and high intensity training groups compared to the resistance and control groups.
Previous research has shown that longer telomeres and increased telomerase activity are associated with healthy aging. However, this is the first prospective, randomised controlled study of the effects of different forms of exercise on these two measurements of cellular aging. A possible mechanism that might explain why endurance and high intensity training could increase telomere length and telomerase activity is that these types of exercise affect levels of nitric oxide in the blood vessels, contributing to the changes in the cells.