A telomere is a region of repetitive DNA at the end of chromosomes, which protects the end of the chromosome from destruction.....
During cell division, the enzymes that duplicate the chromosome and its DNA can't continue their duplication all the way to the end of the chromosome. If cells divided without telomeres, they would lose the end of their chromosomes, and the necessary information it contains. (In 1972, James Watson named this phenomenon the "end replication problem".) The telomere is a disposable buffer, which is consumed during cell division and is replenished by an enzyme, the telomerase reverse transcriptase.
This mechanism usually limits cells to a fixed number of divisions, and animal studies suggest that this is responsible for aging on the cellular level and affects lifespan. (From wiki)
So telomeres are the protective end bits of chromosomes, but they get shorter as you age.... If you remember Dolly, the clone sheep, one of the things about her was that she had shorter telomeres than other sheep and died sooner.
Anyway this study proposes that moderate amounts of exercise - more so than very high or very low levels - have a protective effect on this element of aging.
Relationship between Physical Activity Level, Telomere Length, and Telomerase Activity.
Purpose: The purpose of this study was to examine the relationship of exercise energy expenditure (EEE) with both telomere length and telomerase activity in addition to accounting for hTERT C-1327T promoter genotype.
Methods: Sixty-nine (n = 34 males; n = 35 females) participants 50-70 yr were assessed for weekly EEE level using the Yale Physical Activity Survey. Lifetime consistency of EEE was also determined. Subjects were recruited across a large range of EEE levels and separated into quartiles: 0-990, 991-2340, 2341-3540, and >3541 kcal[middle dot]wk-1. Relative telomere length and telomerase activity were measured in peripheral blood mononuclear cells (PBMC).
Results: The second EEE quartile exhibited significantly longer telomere lengths [1.12 +/- 0.03 relative units (RU)] than both the first and fourth EEE quartiles (0.94 +/- 0.03 and 0.96 +/- 0.03 RU, respectively; P < 0.05) but was not different from the third quartile. Telomerase activity was not different among the EEE quartiles. An association was observed between telomerase enzyme activity and hTERT genotype with the TT genotype (1.0 x 10-2 +/- 4.0 x 10-3 attomoles (amol) per 10,000 cells; n = 19) having significantly greater telomerase enzyme activity than both the CT (1.3 x 10-3 +/- 3.2 x 10-3; n = 30) and CC groups (5.0 x 10-4 +/- 3.9x 10-3; n = 20; P = 0.01).
Conclusion: These results indicate that moderate physical activity levels may provide a protective effect on PBMC telomere length compared with both low and high EEE levels.