Skeletal muscle telomere length in healthy, experienced, endurance runners

(1)	UCT/MRC Research Unit for Exercise Science and Sports Medicine, Department of Human Biology, Faculty of Health Sciences, University of Cape Town, Cape Town, South Africa

(2)	Institut de Myologie, UPMC Univ Paris 06, UMR-S 974, 75013 Paris, France

(3)	Institut de Myologie, INSERM, UMR-S 974, 75013 Paris, France

(4)	Department of Integrative Medical Biology, Section for Anatomy, Umeå University, Umeå, Sweden

(5)	Department of Pathology, Red Cross Children’s Hospital, Cape Town, South Africa

(6)	South African Medical Research Council, Cape Town, South Africa

(7)	UCT/MRC Research Unit for Exercise Science and Sports Medicine, University of Cape Town, P.O. Box 115, Newlands, 7725, South Africa

Measuring the DNA telomere length of skeletal muscle in experienced endurance runners may contribute to our understanding of the effects of chronic exposure to endurance exercise on skeletal muscle. This study compared the minimum terminal restriction fragment (TRF) length in the vastus lateralis muscle of 18 experienced endurance runners (mean age: 42 ± 7 years) to those of 19 sedentary individuals (mean age: 39 ± 10 years). The runners had covered almost 50,000 km in training and racing over 15 years. Minimum TRF lengths measured in the muscle of both groups were similar (P = 0.805) and within the normal range. Minimum TRF length in the runners, however, was inversely related to their years spent running (r = −0.63, P = 0.007) and hours spent training (r = −0.52, P = 0.035). Therefore, since exposure to endurance running may influence minimum TRF length, and by implication, the proliferative potential of the satellite cells, chronic endurance running may be seen as a stressor to skeletal muscle.