PMID 35154334

Research
All papers

Hypoxic repeated sprint interval training improves cardiorespiratory fitness in sedentary young women

Kong Z, Lei OK, Sun S, Li L, Shi Q, Zhang H, Nie J

Question

Does repeated sprint interval training performed in normoxia or simulated hypoxia improve cardiorespiratory fitness and cardiometabolic markers in sedentary young women?

Summary

In sedentary young women, 4 weeks of supervised cycling repeated sprint interval training improved VO2peak when performed under simulated hypoxia. Body composition, fasting glucose, and lipid measures did not change.

Methodology

  • Sedentary young women randomized to normoxic RSIT, two hypoxic RSIT conditions, or non-exercise control
  • 62 participants.
  • Cycle ergometer repeated sprint interval training.
  • Work intervals: 6 s maximal/all-out cycling.
  • Recovery: 9 s recovery.
  • Intensity: Maximal/all-out sprints; hypoxia groups trained at FiO2 0.155 or progressively 0.155 to 0.135.
  • About 20 min plus 10 min pre-exposure, 5 min warm-up, and 5 min cool-down.
  • 3 sessions/week.
  • 4 weeks; 12 sessions.
  • Randomized controlled parallel-group training study
  • VO2peak, Body composition, Glucose and lipids, and Adverse events were tracked.

Outcomes

VO2peak

VO2peak improved in both hypoxic training groups and was higher than normoxic training.

H2500 +8.2%, p < 0.001, d = 0.52; H2500-3400 +10.9%, p < 0.05, d = 0.99; hypoxic groups greater than normoxic training p < 0.05

Improved

Normoxic VO2peak

Normoxic RSIT showed a smaller, non-significant VO2peak change.

Normoxic group +3.6%, not significant

No clear change

Metabolic markers

Body composition, fasting glucose, and lipid markers did not change.

No significant changes reported across groups

No clear change

Safety

The training was reported as well tolerated with no adverse events.

Exceptional completion rate; no adverse events reported

No clear change

Insights

  • A very dense 6 s/9 s sprint design can be completed by sedentary young women under close supervision.
  • Simulated hypoxia appeared to amplify VO2peak gains over the same normoxic sprint dose.
  • The equipment and hypoxic exposure requirements limit direct translation to a general mobile HIIT product.

Limitations

  • Short 4-week intervention
  • Women only and young sedentary sample
  • Hypoxic equipment and laboratory supervision reduce generalizability
  • No hemoglobin or hematocrit assessment
  • High-volume 80-sprint format may be difficult to sustain outside a lab

Safety

  • No adverse events were reported; heart rate and SpO2 were monitored before and after each sprint.