Central and Peripheral Oxygen Distribution in Two Different Modes of Interval Training

Area of Science:

• Exercise Physiology
• Sports Science
• Cardiovascular Research

Background:

• High-intensity interval training (HIIT) effectiveness can be modulated by interval duration.
• Optimizing oxygen uptake, cardiac output, and local oxygen supply requires careful adjustment of interval and rest periods.
• Understanding the physiological impact of different HIIT protocols is crucial for personalized training.

Purpose of the Study:

• To compare physiological responses, including oxygen uptake and cardiac output, between long-interval HIIT (HIIT3m) and short-interval HIIT (HIIT30s).
• To analyze the effects of interval duration on cardiopulmonary and muscle tissue stress under matched work rates and duration.
• To determine if different interval durations elicit comparable overall physiological adaptations.

Main Methods:

• 24 participants completed both HIIT3m (3 min work, 3 min active rest) and HIIT30s (30 s work, 30 s active rest) protocols in a randomized order.
• Work intensity was set at 80% of power output at VO2peak, and relief intensity at 85% of power output at the gas exchange threshold.
• Spirometry, impedance cardiography, and near-infrared spectroscopy were employed to measure physiological variables.

Main Results:

• While HIIT3m had shorter durations above the gas exchange threshold, both protocols showed similar average fractional utilization of VO2peak.
• HIIT3m induced higher cardiovascular responses (VO2 and cardiac output) during loaded intervals.
• No significant differences in local hemodynamics were observed; average physiological responses were similar due to incomplete recovery in HIIT30s and large response amplitudes in HIIT3m.

Conclusions:

• Despite lower acute cardiovascular stress in HIIT30s, short submaximal intervals may induce comparable microvascular and metabolic adaptations to HIIT3m.
• Interval duration is a key variable for tailoring HIIT to specific athlete or patient needs and training goals.
• Both HIIT3m and HIIT30s can be effective, but the choice impacts acute cardiovascular load and recovery dynamics.