Intensified training augments cardiac function, but not blood volume, in male youth elite ice hockey team players

Abstract

While it is well-established that a period of interval training performed at near maximal effort, such as speed endurance training (SET), enhances intense exercise performance in well-trained individuals, less is known about its effect on cardiac morphology and function as well as blood volume. To investigate this, we subjected 12 Under-20 Danish national team ice hockey players (age 18 ± 1 years, mean ± SD) to 4 weeks of SET, consisting of 6-10 × 20 s skating bouts at maximal effort interspersed by 2 min of recovery conducted three times weekly. This was followed by 4 weeks of regular training (follow-up). We assessed resting cardiac function and dimensions using transthoracic echocardiography and quantified total blood volume with the carbon monoxide rebreathing technique at three time points: before SET, after SET and after the follow-up period. After SET, stroke volume had increased by 10 (2-18) mL (mean (95% CI)), left atrial end-diastolic volume by 10 (3-17) mL, and circumferential strain improved by 0.9%-points (1.7-0.1) (all P < 0.05). At follow-up, circumferential strain and left atrial end-diastolic volume were reverted to baseline levels, while stroke volume remained elevated. Blood volume and morphological parameters for the left ventricle, including mass and end-diastolic volume, did not change during the study. In conclusion, our findings demonstrate that a brief period of SET elicits beneficial central cardiac adaptations in elite ice hockey players independent of changes in blood volume.

Keywords: blood volume; echocardiography; high‐intensity interval training; performance.

FIGURE 1

Timeline of the training and the testing battery. SET, speed endurance training; CO, carbon monoxide. Created with BioRender.com.

FIGURE 2

Linear regression for association between changes (delta) in key parameters: stroke volume, blood volume, left atrial end‐diastolic volume, global left ventricular circumferential strain, and global left ventricular longitudinal strain. Filled circles show changes from baseline to SET. Open circles show changes from SET to follow‐up. Regression lines shown the trend of all deltas (filled and open circles) with their 95% confidence interval. SET, speed endurance training.

FIGURE 3

Left ventricular circumferential strain acquired by parasternal short‐axis images at the level of the mitral valve (Base), papillary muscle (Mid), and at the apex (Apical) at baseline (continuous line), in response to SET (dashed line) and at follow‐up (dotted line). SET, speed endurance training.