Effect of repeated endurance runs on cardiac biomarkers and function in adolescents

This study examined the effect of two bouts of prolonged exercise performed on the same day on cardiac biomarkers and left ventricular (LV) function in trained adolescent runners.

Twelve male adolescent runners (age = 14.5 ± 1.5 yr) performed two 45-min constant-load treadmill runs (RUN1 and RUN2), separated by 255 min of recovery, with intensity set at the running speeds that corresponded to ventilatory threshold. Serum cardiac troponin T (cTnT) and N-terminal pro-brain natriuretic peptide (NT-pro-BNP) were assessed before (PRE1, PRE2), immediately after (POST1, POST2), and 255 min after each run (POST1+4, POST2+4) where PRE2 and POST1+4 were the same sample. LV function was examined echocardiographically before and after each run.

cTnT was undetectable at PRE1 and POST1 but was elevated in eight-twelfths (67%) of runners at POST1+4/PRE2 (median (range) = 0.018 (<0.01-0.375 ng·mL(-1))). cTnT decreased progressively thereafter up to POST2+4 (four-twelfths, 33%). Data for NT-pro-BNP were significantly increased at POST1 and POST2 but returned to baseline at POST1+4 and POST2+4. Ejection fraction (EF) was significantly reduced after RUN1 (74% ± 5% to 70% ± 5%, P < 0.05), although still within normal range. There was no evidence of a cumulative drop in EF after RUN2 because the change was similar in magnitude (73% ± 4% to 68% ± 5%, P < 0.05). The decrease in the early-atrial (E:A) diastolic flow velocity ratio was greater after RUN1 (1.91 ± 0.13 to 1.83 ± 0.08, P < 0.05) than after RUN2 (1.86 ± 0.15 to 1.85 ± 0.12, P > 0.05), and thus, changes were not cumulative.

Neither cardiac biomarkers (cTnT or NT-pro-BNP) nor LV function (EF or E:A) demonstrate cumulative changes after two 45-min runs at ventilatory threshold separated by ∼ 4 h of recovery. Adolescent hearts seem to cope well with two prolonged runs performed on the same day.