Key result
Twice-weekly HIIT substantially improves aerobic capacity and metabolic economy while optimizing adherence.
Why the study?
The optimal weekly frequency of 4 × 4 min high−intensity interval training in male university students was unknown, needing evidence to prescribe efficient endurance training in this population.
Does performing 4 × 4 min high-intensity interval training (HIIT) twice or three times per week improve cardiorespiratory function and exercise performance compared to once per week in physically active male university students?
RCT (n=45)
Open-label
Computer-generated randomization sequence
No
Does performing 4 × 4 min high-intensity interval training (HIIT) twice or three times per week improve cardiorespiratory function and exercise performance compared to once per week in physically active male university students?
p-value: p=0.230
Twice-weekly 4 × 4 min HIIT yields substantial improvements in aerobic capacity and submaximal metabolic economy while maintaining high adherence in physically active male university students.
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 (VO 2 max), time to exhaustion, heart rate (HR), oxygen uptake (VO 2 ), 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. VO 2 max increased markedly in both the 2− and 3−session groups, while the 1−session group showed only a small increase. Submaximal VO 2 , 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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Zhang et al. (2026) conducted an RCT in Physically active (n=45). 4 × 4 min high-intensity interval training (HIIT) vs. 1 session per week was evaluated on Maximal oxygen uptake (VO2max) (p=0.230). In physically active male university students, 6 weeks of 4 × 4 min HIIT performed twice or three times weekly yielded substantial improvements in aerobic capacity and submaximal metabolic economy, with twice-weekly training offering the optimal balance of physiological benefits and adherence.
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