Response to: Jiménez-Pavon et al. and Patanè

This commentary refers to ‘Are changes in telomerase activity and telomere length due to different exercise modalities, intensity, or methods: intermittency?’ by D. Jiménez-Pavón et al., on page 3198 and ‘Differential effects of training on telomerase activity and telomere length: the role of miRNAs regulation’ by S. Patanè, on page 3200. The authors appreciate the important comments on our study.1 In our prospective randomized, controlled, training study, we compared the effects of aerobic exercise and high-intensive endurance exercise with resistance exercise, each performed for 45 min 3 ×/week for 6 months, in a primary prevention cohort. The main finding of the study was that chronic aerobic and interval endurance, but not resistance exercise was associated with increased telomerase activity and telomere length in peripheral blood mononuclear cells. Dr Jiménez-Pavon et al.2 argue that a generally lower intensity in our resistance training (RT) group—as opposed to the endurance (ET) groups—could explain the absent effect of RT on telomere parameters. Of note, our RT programme was based on moderate weights3 (100% 20 RM, corresponding to 64 ± 7% of one RM for leg press at baseline4) and the corresponding high number of repetitions (16–20 per set), resulting in high cardiocirculatory and metabolic strain. This is confirmed by mean heart rates (143 ± 11 b.p.m.) and blood lactate concentrations (8.8 ± 1.5 mmol/L) after RT (measured as part of monitoring training loads in a subgroup of eight participants) as well as by a comparable increase in VO2max among training groups. Taken together, it can hardly be ruled out that other combinations of intensity, duration and training frequency would have led to different results. However, within the framework provided by current recommendations,3 it is hardly possible to conceive a practicable RT intervention associated with a more pronounced ET component. Dr Patané5 highlights the potential role of micro-RNA regulation in exercise-induced effects. We believe that it is highly probable that the physiological changes evoked by physical activity include functionally relevant changes including non-coding RNAs and potential additional epigenetic modifications. We hope that our study, in concert with the research of many other groups, sets the stage for important future studies addressing this hypothesis. Understanding of the underlying molecular mechanisms during different types of exercise is urgently needed, e.g. to better understand the threshold, the persistence and the functional consequence of training-induced telomere effects. Ultimately, understanding of the cellular mechanisms may facilitate the prediction of training-response with the long-term aim to provide and to monitor individualized training recommendations. Conflict of interest: none declared.