Abstract
The aim of this study was to assess left ventricular (LV) function and cardiac biomarkers in response to repetitive endurance cycling over 22 days. Ten trained male cyclists (mean±s: age 40±5 years, VO2max 56±4 ml · kg-1 · min-1) completed the 2007 Tour de France route. Before, during, and 2 days after the Tour, all participants underwent an echocardiographic examination to determine ejection fraction, as well as systolic (S'), early diastolic (E'), and late diastolic (A') myocardial tissue velocities, together with the E':A' ratio. Venous blood samples were collected and analysed for cardiac troponin I (cTnI) and B-type-natriuretic peptide. Repeated-measures analysis of variance was used to investigate the cumulative effects of prolonged exercise bouts on LV function and cardiac biomarkers. Alpha was set at 0.05. Although both the ejection fraction (71 ± 2% vs. 59 ± 4%; P ± 0.05) and the E':A' ratio (1.60 ± 0.15 vs. 1.09 ± 0.12; P > 0.05) were reduced at post-stage assessments, there was limited evidence of a progressive decline in either variable over the 22 days. Although post-tour ejection fraction was not different to baseline (68 ± 3%; P ± 0.05), the E':A' ratio remained depressed (1.37 ± 0.26; P > 0.05) following 2 days of recovery. No cTnI was detectable at baseline and B-type-natriuretic peptide was within normal ranges (24 ± 7 pg · ml-1). Cardiac troponin I was detectable in at least one cyclist at every assessment, with 60% being positive after stage 15 (range 0.02-0.09 μg · ml-1). B-type-natriuretic peptide peaked following stage 17 (240 ± 145 pg · ml-1). In conclusion, repetitive endurance cycling resulted in an acute reduction in LV function and the sporadic appearance of cardiac biomarkers following each day of exercise. Despite this there was no cumulative effect of repetitive exercise. Minor changes in diastolic function persisted up to 48 h of recovery.