Yi-xin Wu’s research while affiliated with Shenyang University and other places

The paper by Qin et al. showed that high-intensity interval training (HIIT) could significantly improve peak oxygen uptake in post-MI （myocardial infarction） patients, and no significant difference in systolic and diastolic blood pressures, peak and resting heart rate, left ventricular ejection fraction, and left ventricular end-diastolic volume was found between HIIT group and control group.¹ Although its overall effectiveness in exercise capacity is often difficult to attribute to a single specific mechanism, compared with moderate-intensity continuous training and routine physical activity, it is speculated that HIIT’s potential for promoting gains in muscular strength may play an important role because of ‘high intensity’. The persistent view of improving muscular strength is generally dominated by resistance-based training, which is recommended as the preferred type of exercise to improve muscle mass, cross-sectional area of muscle fibres (hypertrophy), and neural adaptations such as motor unit recruitment.² Although the activations of muscle fibres during almost all exercise activities are not exclusive, there are dominant recruitments of motor units with their own attributes in different training zones. The non-exclusivity also exists in energy supplies deriving from aerobic and anaerobic energy system. Exercise intensity above the first ventilatory threshold can elicit more contribution of anaerobic glycolytic energy, corresponding to the initial recruitment of Type IIA muscle fibres;³ similarly, exercise intensity above the second ventilation threshold can recruit Type IIB muscle fibres requiring immediate/high-energy adenosine triphosphate supply (Table 1). These high-threshold motor units are also recruited during resistance training. The greater activation of Type II muscle fibres is significantly related to the improvement of muscular strength. Therefore, HIIT can theoretically elicit muscle adaptations resembling resistance training.