Regarding High-Intensity Interval Training and Left Ventricular Mechanics
Year: 2019
Type: article
Abstract: Dear Editor in Chief, The influence of exercise on the mechanical function of the heart has become a topic of considerable interest over the past decades. In a recent issue of Medicine and Science in Sports and Exercise, Huang et al. (1) report on a study that investigated the effects of high-intensity interval training (HIIT) on echocardiographic-derived indices of left ventricular (LV) mechanical function in young, sedentary, but otherwise healthy men. We believe that this study has the potential to further our understanding on how the heart responds to exercise, and it ultimately fits within the current knowledge on exercise-induced cardiac adaptation in health and disease (2). However, given the data and the conclusions derived from them, we would appreciate additional details from the authors on the methodology used that may have contributed to the unusually large increase in cardiorespiratory fitness after a very short HIIT intervention and the exceptionally low values derived from speckle tracking echocardiography. First, it is surprising that a 6-wk HIIT program in healthy, young individuals induced a rise in V̇O2max by an average of 11.1 mL·kg−1⋅min−1 (32%), in the presence of no change in total body weight. The highest average effect reported in a relatively recent meta-analysis of the relevant literature was half of that reported by Huang et al. (1), namely, a 5.5-mL·kg−1⋅min−1 increase in response to HIIT after 13 wk (3). Why would healthy individuals such as those included in the study by Huang et al. (1) experience such a large increase in such a short period of time? Second, the mean values for the main echocardiographic parameters (LV twist, untwisting rate, circumferential strain, and longitudinal strain) are significantly lower than those commonly reported for healthy individuals (2). The drastically low LV twist (6.18° to 7.52°), untwisting rate (−27°·s−1 to −32°·s−1), circumferential strain (−12.5% to −15.3%), and longitudinal strain (−13.5% to −14.1%) could be considered those of cardiac patients with markedly impaired contractile function (2). Yet, ejection fraction appears to have been normal (61%–64%), suggesting a healthy population. How can this be explained? In addition, because the main aim of the study was to compare the effect of exercise training at two different intensities on the heart’s dynamic responses to acute exercise, more details regarding the following points seem necessary: 1) the methods of standardization used by the authors to ensure that workload and energy expenditure were similar between the training groups during their respective exercise training, and 2) the rationale for why LV mechanical function was assessed during a fixed absolute exercise intensity, despite previous reports recommending that LV mechanics be assessed during exercise at intensities relative to an individual’s maximum workload capacity (4). We acknowledge the effort that is required in undertaking exercise training studies and the personnel that is required to perform the echocardiographic assessments. For this, we commend the authors on their preparation and execution of the study. At present, however, we are concerned about the accuracy and generalizability of the findings of Huang et al. (1) for the aforementioned reasons. Further insight into the methodological considerations may assist with the interpretation of the current results and ultimately provide the foundation for future research in this area of interest. Eric J. Stöhr Cardiff Metropolitan University Cardiff UNITED KINGDOM Columbia University New York, NY Bryce N. Balmain Surendran Sabapathy Surendran Sabapathy Griffith University, Gold Coast Queensland, AUSTRALIA
Language: English
Subfield: Cardiology and Cardiovascular Medicine
Field: Medicine
Domain: Health Sciences
Open Access status: green
OpenAlex ID: W2981311775