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Updated: Aug 5, 2026
A Real-World High-Intensity Interval Training Protocol for Cardiorespiratory Fitness Improvement
Published on: February 22, 2022
Study on the effects of 4 × 4 min high-intensity interval training frequency on cardiorespiratory function, metabolic
Hanwen Zhang1, Yingjian Zhang2, Heng Tian3
1Capital University of Physical Education and Sports, Beijing, China.
Objective:
To determine the optimal weekly frequency of 4 × 4 min high-intensity interval training (HIIT) in male university students and thus provide evidence for prescribing efficient endurance training in this population.
Methods:
Forty-five physically active male university students were randomly assigned to three groups performing 4 × 4 min HIIT once, twice, or three sessions per week (n = 15 per group) for 6 weeks. Maximal oxygen uptake (VO2max), time to exhaustion, heart rate (HR), oxygen uptake (VO2), ventilatory threshold (VT), respiratory exchange ratio (RER), and blood lactate concentration were assessed via treadmill testing and breath-by-breath gas analysis. Repeated-measures ANOVA was used for statistical analysis.
Results:
After 6 weeks of intervention, all groups showed prolonged time to exhaustion and reduced submaximal HR and blood lactate, with the 2- and 3-session groups exhibiting larger improvement magnitudes. VO2max increased markedly in both the 2- and 3-session groups, while the 1-session group showed only a small increase. Submaximal VO2, VT, and RER changed minimally across groups. Post-intervention blood lactate was notably lower in the 2- and 3-session groups than in the 1-session group (p < 0.001), whereas physiological improvements were generally comparable between the 2- and 3-session groups. Training completion rates were 100%, 93%, and 80% in the 1-, 2-, and 3-session groups, respectively.
Conclusion:
Within the present study conditions, twice-weekly 4 × 4 min HIIT yielded substantial improvements in aerobic capacity and submaximal metabolic economy while maintaining relatively high adherence, showing a favorable balance between training benefits and tolerability. The twice-weekly frequency appears relatively optimal for physically active male university students. These findings are limited by the homogeneous sample and short intervention period, and further validation in larger, diverse cohorts is warranted.
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