Serum cardiac troponin T in adolescent runners: Effects of exercise intensity and duration

The purpose of this study was to evaluate the interactive effects of exercise duration and intensity on the elevation of serum cardiac troponin T (cTnT) in trained adolescent athletes following prolonged exercise in a laboratory-based setting. Thirteen male adolescent runners (mean age 14.8 ± 1.6 year) performed two 45-min and two 90-min constant-load treadmill runs with intensities set at the running speeds that corresponded to either 80 % or 100 % ventilatory threshold (Th_vent): 80%Th_vent45 min, 80%Th_vent90 min, 100%Th_vent45 min and 100%Th _vent90 min. Serum cTnT was assessed pre and post exercise. In the 100%Th_vent45 min trial, the post-exercise serum cTnT level [(Median) 0.015 ng.ml^-1; (Range)<0.01-0.375ng.ml^-1] was greater than that of the 80%Th_vent45 min (undetectable cTnT) and 80%Th _vent 90 min (detectable cTnT in two subjects, 0.021 and 0.133 ng.ml^-1) trials (P<0.01). The serum cTnT level was further increased in the 100%Th_vent90 min trial [(Median) 0.063 ng.ml ^-1; (Range)<0.01-0.417ng.ml^-1] when the treadmill run was sustained for an additional 45 min (P < 0.05). Similar changes were observed in the cTnT positive rate in subjects. These fi ndings suggest that exercise duration and intensity are essential factors in eliciting cTnT release interactively following an endurance exercise. Nevertheless, exercise intensity compared to duration appears to cause a more pronounced increase in cTnT levels.