Comparative impacts of endurance and resistance exercise on the cardiovascular system in humans: a prospective reandomised 6-month intervention

[Truncated abstract] In recent years, sophisticated imaging modalities have evolved which considerably enhance our capacity to describe human anatomy and physiology. These approaches, including magnetic resonance imaging (MRI) and high-resolution duplex ultrasonography, permit us to describe cardiovascular adaptations to exercise training, in vivo, at a level of precision that has not been historically possible. In addition to facilitating the description of novel phenomena, the marked improvements in spatial and temporal resolution that have resulted from these technologies allow critical reappraisal of accepted textbook dogma. There is a long held belief in exercise science that different modalities of exercise training induce distinct cardiac morphological adaptations. This notion, embedded in the 'Morganroth' and 'athlete's heart' concepts, is almost entirely based on echocardiographic assessments which have limited anatomical resolution and heavily rely on a number of key assumptions such as the calculation of 3-dimensional parameters from 2-dimensional images. No previous study has directly addressed the question of the relative impacts of resistance and endurance training modalities on cardiac morphology and function using MRI. Whilst high-resolution duplex ultrasound has provided a platform for major advances in our understanding of the impacts of exercise training on arterial structure and function, the effect of resistance and endurance training has not been directly experimentally addressed in asymptomatic humans. This question is relevant for several reasons. Firstly, previous studies have been largely based on cross-sectional comparisons between elite athletes and controls and whilst longitudinal training studies which control for between-subject differences have been performed, the majority of these are of relatively short-term duration.