AUTHOR=Ito Go , Feeley Marina , Sawai Toru , Nakata Hideomi , Otsuki Shingo , Nakahara Hidehiro , Miyamoto Tadayoshi 

TITLE=High-intensity interval training improves respiratory and cardiovascular adjustments before and after initiation of exercise

JOURNAL=Frontiers in Physiology

VOLUME=15

YEAR=2024

URL=https://www.frontiersin.org/journals/physiology/articles/10.3389/fphys.2024.1227316

DOI=10.3389/fphys.2024.1227316

ISSN=1664-042X

ABSTRACT=<p><bold>Purpose:</bold> High-intensity interval training (HIIT) may induce training-specific physiological adaptations such as improved respiratory and cardiovascular adjustments before and after the onset of high-intensity exercise, leading to improved exercise performance during high-intensity exercise. The present study investigated the effects of HIIT on time-dependent cardiorespiratory adjustment during maximal exercise and before and after initiation of high-intensity exercise, as well as on maximal exercise performance.</p><p><bold>Methods:</bold> 21 healthy male college students were randomly assigned to HIIT group (n = 11) or control group (n = 10). HIIT group performed training on a cycle ergometer once a week for 8 weeks. The training consisted of three bouts of exercise at 95% maximal work rate (WR<sub>max</sub>) until exhaustion. Before and after the HIIT program, dynamic cardiorespiratory function was investigated by ramp and step exercise tests, and HIIT-induced cardiac morphological changes were assessed using echocardiography.</p><p><bold>Results:</bold> HIIT significantly improved not only maximal oxygen uptake and minute ventilation, but also maximal heart rate (HR), systolic blood pressure (SBP), and time to exhaustion in both exercise tests (<italic>p</italic> &lt; 0.05). Time-dependent increases in minute ventilation (V<sub>E</sub>) and HR before and at the start of exercise were significantly enhanced after HIIT. During high-intensity exercise, there was a strong correlation between percent change (from before to after HIIT program) in time to exhaustion and percent change in HR<sub>max</sub> (r = 0.932, <italic>p</italic> &lt; 0.001). Furthermore, HIIT-induced cardiac morphological changes such as ventricular wall hypertrophy was observed (<italic>p</italic> &lt; 0.001).</p><p><bold>Conclusion:</bold> We have demonstrated that HIIT at 95% WR<sub>max</sub> induces training-specific adaptations such as improved cardiorespiratory adjustments, not only during maximal exercise but also before and after the onset of high-intensity exercise, improvement of exercise performance mainly associated with circulatory systems.</p>