Do the effects of high intensity 40 km cycling upon left ventricular function and cardiac biomarker during recovery vary with time of day?

Abstract

Twelve healthy participants performed two identical high-intensity 40 km cycling trials (morning and evening) under controlled laboratory conditions. Echocardiograms and venous blood samples were collected before and after each exercise bout. Cardiac electro-mechanical-delay (cEMD) was measured as QRS-complex onset to peak systolic (S') and early diastolic (E') tissue velocities. Myocardial strain and strain rates were assessed in longitudinal, circumferential and radial planes at the left ventricular apex and base. Cardiac troponin I (cTnI) and N-terminal Pro-Brain Natriuretic Peptide (NT-proBNP) were assessed as biomarkers of cardiomyocyte damage and wall stress. cEMD was lengthened after both morning (S': 160 ± 30 vs. 193 ± 27; E': 478 ± 60 vs. 620 ± 87, P < 0.05) and evening (S': 155 ± 29 vs. 195 ± 31; E': 488 ± 42 vs. 614 ± 61, P < 0.05) trials. A reduction in peak S' (morning: 6.96 ± 1.12 vs. 6.66 ± 0.89; evening: 7.09 ± 0.94 vs. 7.02 ± 0.76) was correlated with cEMD (r = -0.335, P < 0.05). Peak longitudinal strain was reduced, atrial strain rates were sporadically increased in both trials post-cycling. cTnI was elevated in only two participants (0.04 µg · L(-1), 0.03 µg · L(-1)), whilst NT-proBNP was below the clinical cut-off point in all participants. Prolonged-cycling resulted in a lengthening of cEMD, small changes in aspects of left ventricular deformation and sporadic increases in cardiac biomarkers. None of these effects were moderated by time-of-day.

Left Ventricular Function and Cardiac Biomarker Release—The Influence of Exercise Intensity, Duration and Mode: A Systematic Review and Meta-Analysis

“…Exercise was shown to significantly reduce RV longitudinal strain (LS) in two studies (1, 27) that involved >60 minutes of exercise, whereas RV LS was maintained in the study of Stewart et al(15), which involved <60 minutes of exercise. Longitudinal LV strain was significantly reduced in three studies (1,19,27), and unaffected following a 6 hour triathlon in the study of Leetmaa et al(23). The participants in this study were elite national-level triathletes and it is worth noting that the reported values were substantially higher than in all other studies (27.5% preexercise, 26.8% post).…”

“…Three studies (10,20,35) reported the previously obtained intra-individual CV of their echocardiographic measurements to demonstrate reliability. (19,20). It would appear from these findings that cycling exercise of up to minutes duration at low to moderate-intensities does not affect myocardial strain but high intensity cycling exercise of >60 minutes may negatively impact radial, circumferential and longitudinal strain.…”

“…With the exceptions of the two studies by Chan-Dewar et al (19,20), all studies reported that exercise lead to a significantly reduced LVEF, E/A ratio, or both variables. There were five studies in total that reported significant reductions in both E/A ratio and LVEF (6,10,25,26,27) and the study quality amongst these ranged from fair to good.…”

“…The participants in this study were elite national-level triathletes and it is worth noting that the reported values were substantially higher than in all other studies (27.5% preexercise, 26.8% post). Longitudinal strain was increased following the low-intensity exercise bout in Chan-Dewar et al(20), and maintained following <60 minutes of moderate intensity cycling in the studies of Stewart et al(15) and Chan-Dewar et al(19). Stewart and colleagues(15) reported large reductions in radial strain (RS) and a small, significant reduction in circumferential strain (CS), with no concomitant change in RS or CS rates.…”

“…There were six studies (1,15,19,20,23,27) that reported LV or RV strain and strain rates. These variables were reported in limited and insufficient quantities across the 22 studies to facilitate a meta-analysis of the strain data.…”