title: The effect of prolonged exercise and environmental temperature upon left ventricular function and cardiac biomarker release
Creators: name: Hankey, J
Publisher: name: Liverpool John Moores University
Year: 2019

description: This thesis examined the effect of single and repeat bouts of prolonged exercise as well as an environmental temperature challenge upon left ventricular (LV) function and cardiac biomarker release. The primary aims were; (1) does repeated exercise bouts mediate a cumulative decrease in LV function and/or increase in cardiac biomarker concentrations; and (2) to examine the impact of prolonged exercise in a hyperthermic environment upon cardiac function and cardiac biomarker levels. Study 1 demonstrated evidence of LV systolic and diastolic dysfunction after exercise that persisted 22 hours into recovery following 10 days of cycling in amateur cyclists. There was however, limited support for a cumulative change in function across days. A highly individual, but not cumulative, pattern of cardiac biomarker appearance was observed with rapid clearance. This data suggests that the cardiovascular system of the amateur cyclists coped well with the accumulated exercise stress imposed by the repeated cycling over 10 days. Study 2 revealed that a single bout of prolonged exercise (37 km), in a hyperthermic environment, resulted in a decrease in LV systolic and diastolic function and an elevation in cardiac biomarkers. There was no evidence of cumulative changes in function or biomarker appearance over a further 5 days of exercise in a hyperthermic environment. Significant individual variation between participant’s responses were again noted. Study 3 employed a controlled exercise stimulus in a laboratory setting and revealed both LV systolic and diastolic function were not significantly altered following 60 minutes of running in either a normothermic (13oC) or hyperthermic (30oC) environment. The release of cardiac biomarkers was limited, with a tendency for markers to be higher in the hyperthemic condition. Participants coped well with the exercise stress, however, the “low” exercise dose in this study likely negates any meaningful impact upon cardiac function and biomarker release. The final study manipulated core temperature (Tc), through pre-cooling, prior to exercise in a hyperthermic environment (32.4 ± 0.9oC and 46.8 ± 6.4% RH). Diastolic, but not systolic, function was reduced following 90 minutes of running, with no difference apparent between pre-cooling and control conditions. cTnT was evident in all participants following both trials, with a limited release of NT-proBNP that was not mediated by pre-cooling. Pre-cooling appeared to have no beneficial or adverse effect on the cardiovascular function and biomarkers that again displayed high inter-individual variability. In conclusion, we observed evidence that acute exercise can result in changes in both cardiac function and biomarkers. There was, however; (1) no evidence of an accumulation of cardiac function or biomarker data across multiple bouts of exercise across a number of days, and (2) limited evidence that either a hyperthermic environment or a pre-cooling intervention altered cardiac function and biomarker data after exercise in a controlled laboratory design. Changes in cardiac function and biomarkers were transient in nature, of relatively small magnitude and subject to high individual variability. It would seem that these changes represent an acute physiologic perturbation as opposed to pathology.