Related Experiment Video
Updated: Jun 5, 2026
A Real-World High-Intensity Interval Training Protocol for Cardiorespiratory Fitness Improvement
Published on: February 22, 2022
Time spent at or near V̇O₂max during high-intensity interval training - a systematic review and meta-analysis
Patrick Schoenmakers1, Kelly Murray2, Jamie White2,3
1School of Sport, Rehabilitation, and Exercise Sciences, University of Essex, Colchester, CO4 3SQ, United Kingdom. ppscho@essex.ac.uk.
Background:
High-intensity interval training (HIIT) is widely recognised as an effective strategy to improve cardiorespiratory fitness and endurance performance. Time spent at or near maximal oxygen uptake (tV̇O2max) has emerged as a key marker of the adaptive potential of HIIT, yet HIIT configurations that maximise tV̇O₂max remain unclear.
Objective:
This systematic review and meta-analysis examined acute tV̇O₂max responses across various HIIT protocols, aiming to identify configurations with the greatest potential to stimulate training adaptations.
Methods:
PubMed and Scopus were systematically searched to September 2025 for studies reporting tV̇O₂max during HIIT, defined as time spent at or above ≥ 80% V̇O₂max. Associations between protocol characteristics and tV̇O₂max were evaluated using ANCOVAs and linear mixed-effects models, while random-effects meta-analyses compared standardised mean differences (SMDs) across HIIT configurations, recovery modalities (active vs passive), and exercise intensity distributions in work intervals.
Results:
The literature search yielded 86 unique articles, in which tV̇O2max was determined for a total of 239 HIIT protocols. Protocols with long work intervals (≥ 2 min) elicited significantly greater tV̇O₂max than short (≤ 30 s) or moderate (> 30 s to < 2 min) work intervals, and linear mixed-effects models confirmed a positive relationship between cumulative HIIT duration and time ≥ 90% and ≥ 95% V̇O₂max when longer work intervals were used. Protocols incorporating variable-intensity work intervals further increased tV̇O₂max compared to even-paced formats (SMD = 0.80, p < .01). In contrast, recovery modality (active vs passive) showed no effect on tV̇O₂max.
Conclusions:
tV̇O₂max exhibits considerable variability, and its dose-response relationship with long-term adaptations requires further investigation. Nevertheless, HIIT protocols with longer and variable-intensity work intervals maximise tV̇O₂max, providing researchers, practitioners, and athletes with a firmer foundation for understanding how specific protocols shape the physiological demands and adaptive potential of a workout.
Related Concept Videos
01:19Cardiac Output I:Effect of Heart Rate on Cardiac Output
Cardiac output (CO) refers to the total amount of blood ejected by one of the ventricles in liters per minute (L/min). In a resting adult, CO ranges from 5 to 6 L/min, adjusting according to the body's metabolic requirements.
Effect of Heart Rate on Cardiac Output
Cardiac output adapts to metabolic demands during stress, physical activity, or illness. The autonomic nervous system regulates heart rate via the sinoatrial node. The parasympathetic nervous system decreases heart rate...
01:17Exercise and Cardiac Output
Sustained exercise increases the muscles' oxygen demand, which can be met...
01:20Exercise and Cardiovascular Response
Light to moderate physical activity initiates a series of interconnected responses in the body. The heart rate modestly increases in anticipation of the workout, followed by widespread vasodilation as oxygen consumption by skeletal muscles increases. This results in decreased peripheral resistance, increased capillary blood flow, and accelerated...
01:30Factors Influencing Heart Rate
Let us explore the significant factors affecting heart rate, including age, body temperature, posture, acute pain, chemical influences,...
01:22Cardiac Output II: Effect of Stroke Volume on Cardiac Output
Preload
Preload refers to the initial elongation of the cardiac myocytes before contraction and is related to the volume of blood filling the heart at the end of diastole, or end-diastolic volume. The...
01:27Exercise and Muscle Performance
Endurance exercises
Endurance exercises involve running, swimming, or cycling, which require repetitive movements with low force output. When a person engages in endurance exercise, a few noticeable changes occur in their skeletal muscles. For instance, the number of capillaries...