Longer HIIT intervals increased time near VO2max

HIIT sessions can be built in many ways, and those details matter. This study helps runners and coaches think more clearly about which interval formats spend more time near VO2maxVO2max is the maximal rate of oxygen consumption your body can achieve during exercise. It is a measure of cardiorespiratory fitness and indicates the size of your engine, i.e., your maximal aerobic power, which contributes to endurance performance., without pretending that 1 workout metric explains the whole training puzzle.

Reference: Schoenmakers et al. Time spent at or near V̇O₂max during high-intensity interval training - a systematic review and meta-analysis. BMC Sports Science, Medicine and Rehabilitation (2026) DOI: 10.1186/s13102-026-01766-x.

Study snapshot

A quick, practical summary for runners and coaches.

Quick answer

This systematic reviewA systematic review answers a specific research question by systematically collating all known experimental evidence, which is collected according to pre-specified eligibility criteria. A systematic review helps inform decisions, guidelines, and policy. and meta-analysisA meta-analysis quantifies the overall effect size of a treatment by compiling effect sizes from all known studies of that treatment. examined short-term oxygen uptake during HIIT across 86 studies. Longer intervals and variable-intensity intervals generally produced more time near VO2max. The main caution: this does not prove better long-term fitness or race performance.

Key takeaways

  • Longer HIIT intervals generally produced more time near VO2max.
  • The evidence measured short-term workout responses, not long-term performance.
  • Runners and coaches can use this to guide workout design, not rewrite the whole training plan.

How confident should we be?

Evidence confidence: Moderate

The review included many protocols and used objective oxygen uptake measures. But the studies varied widely, the evidence was not runner-only, and time near VO2max is a useful marker rather than a race result.

Bottom line

Longer intervals, especially efforts lasting 2 minutes or more, look useful when the goal is to spend more time near VO2max. But more time near VO2max is not magic fairy dust. It is 1 clue for designing hard sessions.

Read the deep dive below for a practical interpretation, actionable decisions, my thoughts, my Rating of Perceived scientific Enjoyment, the study details, full results, strengths, and limitations.

Running science research reviews for endurance runners

The deep dive

The details behind the headline result, including the practical meaning, full findings, limitations, and my interpretation.

Practical meaning

What does this research mean for runners and coaches?

This review is useful because it addresses a practical coaching question: which HIIT formats keep athletes near VO2max for longer?

The answer was fairly clear for this short-term oxygen uptake outcome. Longer work intervals generally accumulated more time near VO2max than short or moderate intervals. Variable-intensity intervals also looked promising.

But the practical meaning needs a seatbelt. The review did not test whether these workouts improved running performance over weeks or months. It also included several exercise modes, including cycling, running, rowing, swimming, kayaking, cross-country skiing, and jumping. So, the findings apply to endurance training broadly, but they are not a runner-only rulebook.

For runners

If the goal of the session is to target VO2max, intervals lasting 2 minutes or longer are a sensible place to look. In practice, that often means hard but controlled intervals of 3 to 5 minutes, with enough recovery (typically as long as the interval) to keep the quality high.

That is a practical interpretation, not a direct study finding. The review did not prescribe specific runner workouts.

For marathon runners, this supports using VO2max-style intervals sparingly within a broader plan. For trail runners and ultra runners, the same idea may apply, especially for uphill power and aerobic capacity, but the review did not test trail or ultra training directly.

For coaches

The review can help coaches match the session to the goal. If the goal is time near VO2max, longer intervals and some variable-intensity formats are likely better options than relying only on very short hard efforts.

Still, the session needs to fit the athlete. A perfect-looking VO2max workout is less useful if the athlete is cooked, injury-prone, or 4 days away from a key race.

Practical decision

Should runners change anything?

Maybe. Longer VO2max-style intervals may be worth considering when the specific goal is to spend more time near VO2max, but the review does not justify rewriting a whole training plan.

Consider this if

  • The goal of the workout is to target VO2max.
  • The athlete already tolerates hard intervals well.
  • The current plan uses mostly very short intervals but aims to improve aerobic capacity.

Do not overreact if

  • The athlete is already improving.
  • The athlete is carrying fatigue or injury risk.
  • The main goal is marathon, trail, or ultra performance, where VO2max is only 1 part of the puzzle.

A sensible next step

Use longer VO2max-style intervals occasionally. Think hard, controlled efforts rather than “I have seen the light and it was mostly tunnel.” Keep the workout in proportion to the rest of the training week.

TIP: Never make any major changes to your training or lifestyle habits based on the findings of one study, especially if the study is small or provides low-quality evidenceA low quality of evidence means that, in general, studies in this field have several limitations. This could be due to inconsistency in effects between studies, a large range of effect sizes between studies, and/or a high risk of bias (caused by inappropriate controls, a small number of studies, small numbers of participants, poor/absent randomisation processes, missing data, inappropriate methods/statistics). When the quality of evidence is low, there is more doubt and less confidence in the overall effect of an intervention, and future studies could easily change overall conclusions. The best way to improve the quality of evidence is for scientists to conduct large, well-controlled, high-quality randomised controlled trials.. Check whether other trials confirm the findings. If there is a meta-analysis on the topic, look at the effect sizeA standardised measure of the magnitude of an effect of an intervention. Unlike p-values, effect sizes show the size of the effect and how meaningful it might be. Common effect size measures include standardised mean difference (SMD), Cohen’s d, Hedges’ g, eta-squared, and correlation coefficients., the variability between studiesHeterogeneity shows how much the results in different studies in a meta-analysis vary from each other. It is measured as the percentage of variation (the I2 value). A rule of thumb: if I2 is roughly 25%, that indicates low heterogeneity (good), 50% is moderate, and 75% indicates high heterogeneity (bad). High heterogeneity means there’s more variability in effects between studies and, therefore, a less precise overall effect estimate., and the quality of evidenceCertainty of evidence tells us how confident we are that the published results accurately reflect the true effect. It’s based on factors like study design, risk of bias, consistency, directness, precision, and publication bias. High certainty means that the current evidence is so strong and consistent that future studies are unlikely to change conclusions. Whereas, low certainty means more doubt and less confidence, and that future studies could easily change current conclusions..

Expert interpretation

My thoughts

Running science from Thomas Solomon at Veohtu

This is a useful review for runners and coaches because it connects workout design to a measurable physiological response. That is good nerd fuel.

The main message is practical: longer intervals generally gave athletes more time near VO2max. Variable-intensity intervals also looked interesting. The force is reasonably strong with this one, for the short-term oxygen uptake outcome at least.

But I would not worship time near VO2max as the only sacred training metric. The review tells us what happened during workouts. It does not prove which sessions make runners faster, healthier, or more durable over a training block.

So, I would use this paper to refine interval design, not overhaul a programme. The unresolved bit is the fun bit: if 1 workout gives more time near VO2max, does it always make the runner better? Probably not always, and that’s where coaching gets interesting.

My Rating of Perceived scientific Enjoyment

owlRPsE: 5/10

I experienced low scientific enjoyment because although the authors asked a useful coaching question and reported risk of biasRisk of bias in a meta-analysis refers to the potential for systematic errors in the studies included in the analysis. Such errors can lead to misleading/invalid results and unreliable conclusions. This can arise because of issues with the way participants are selected (randomisation), how data is collected and analysed, and how the results are reported. clearly, it lacked several important standard metholdogical component for a meta-analysis. For example, it did not include a protocol pre-registrationPre-registration is when a detailed description of a study plan is deposited in an open-access repository before collecting the study data. It promotes transparency and accountability and boosts research integrity. Without preregistration, it is easier for scientists to change outcomes after seeing the data, selectively report “exciting” results, or run many analyses and only show the ones that work, which can introduce bias and weaken the trustworthiness of the findings. or an assessment of publication biasPublication bias in a meta-analysis occurs when smaller or less favorable studies are probably missing. This means that studies with satistically significant results are more likely to be published than those with non-significant findings, leading to distorted conclusions. This bias can inflate effect sizes and misrepresent the true effectiveness of interventions. or certainty of evidenceCertainty of evidence tells us how confident we are that the published results accurately reflect the true effect. It’s based on factors like study design, risk of bias, consistency, directness, precision, and publication bias. High certainty means that the current evidence is so strong and consistent that future studies are unlikely to change conclusions. Whereas, low certainty means more doubt and less confidence, and that future studies could easily change current conclusions. (such as GRADEGRADE, which stands for Grading of Recommendations Assessment, Development and Evaluation, is a standardised and structured approach used to assess the certainty of evidence in meta-analyses. It evaluates how “confident” researchers are in the results of studies and the recommendations that follow from them. GRADE rates a body of evidence as “high”, “moderate”, “low”, or “very low” certainty using a set of standardised criteria.).

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Read on for further details about the paper.

Research question

What did the researchers ask?

The authors aimed to identify which HIIT protocols produced the most time at or near VO2max.

VO2max is the highest rate at which the body can use oxygen during hard exercise. Time near VO2max is often used as a marker of how strong the aerobic stimulus of a workout might be. In plain English: how long the session keeps the engine close to full blast.

Study design

What type of study was this?

This study was a systematic review and meta-analysis.

A systematic review collects studies using a planned search strategy. A meta-analysis pools numerical results across studies. This design can show broad patterns across the evidence, but the conclusions depend on the quality, similarity, and reporting of the included studies.

This review examined short-term oxygen uptake during HIIT protocols. It did not directly test whether the protocols caused better long-term VO2max gains, race performance, recovery, or injury outcomes.

Participants

Who took part?

The review included 86 studies and 239 HIIT protocols. The studies included apparently healthy human participants.

The authors did not restrict the included studies by age, training status, or exercise type. The exercise modes included cycling, running, rowing, swimming, kayaking, cross-country skiing, and jumping.

The paper reported participant details study by study, rather than as 1 pooled summary. A pooled total for sex distribution, age, training status, or runner-only participants was not reported in the source.

Methods

What did the researchers do?

Who? Apparently healthy humans
What? HIIT protocols measuring time near VO2max
How many? 86 studies and 239 protocols

The researchers searched PubMed and Scopus up to September 2025. They followed the PRISMA reportingPreferred Reporting Items for Systematic reviews and Meta-Analyses (PRISMA) reporting is a set of guidelines that helps researchers clearly and completely report a systematic review or meta-analysis. It gives them a checklist and flow diagram to show what they searched, what they included, and how they made their decisions. This makes the review easier to understand, assess, and trust. approach for systematic reviews.

They included peer-reviewed English-language studies that measured time at or near VO2max during HIIT in apparently healthy humans. They excluded studies in clinical populations and studies that did not report time near VO2max.

The researchers grouped HIIT protocols by work interval duration. Short intervals lasted 30 seconds or less. Moderate intervals lasted more than 30 seconds but less than 2 minutes. Long intervals lasted 2 minutes or more.

The researchers mainly analysed time spent at or above 90% and 95% of VO2max. They also compared active recovery with passive recovery, and even-paced intervals with variable-intensity intervals.

Main findings

What did the study find?

Long intervals More time near VO2max
Variable-intensity intervals Moderate increase
Recovery type No clear difference

The researchers found that 133 of the 239 protocols accumulated at least 5 minutes near VO2max. Only 48 protocols accumulated at least 10 minutes near VO2max.

For time at or above 90% of VO2max, the researchers analysed 183 protocols. Long-interval HIIT produced more time near VO2max than short-interval and moderate-interval HIIT. The difference was moderate in size.

The average time at or above 90% of VO2max was 336 seconds for short intervals, 322 seconds for moderate intervals, and 555 seconds for long intervals. So, long intervals added roughly 3 to 4 minutes more time near VO2max.

For time at or above 95% of VO2max, the researchers analysed 117 protocols. Long intervals again produced more time near VO2max than short and moderate intervals. The difference was moderate to large.

The average time at or above 95% of VO2max was 162 seconds for short intervals, 137 seconds for moderate intervals, and 319 seconds for long intervals. So, long intervals roughly doubled the time spent very close to VO2max compared with shorter formats.

The pooled meta-analysis found a small overall difference in time near VO2max across short, moderate, and long interval formats. Longer intervals generally came out best, but variation between studies was high. That means the average result hides a lot of workout-to-workout messiness.

Recovery type was less exciting. Active recovery and passive recovery did not clearly differ for time near VO2max. However, in exhaustive HIIT protocols, passive recovery allowed athletes to complete more total high-intensity work.

Variable-intensity intervals produced more time near VO2max than even-paced intervals. The pooled effect was moderate. In a subset that excluded unclear fraction-based results, variable-intensity intervals added about 165 seconds of time near VO2max.

The authors concluded that longer and variable-intensity work intervals maximise time near VO2max. They also cautioned that the dose-response link between time near VO2max and long-term adaptations still needs more research.

What helps my confidence in the findings?

The strengths

  • The review included 86 studies and 239 HIIT protocols.
  • The researchers used a systematic search and followed PRISMA.
  • The review assessed study quality and risk of bias.
  • The main outcome used objective oxygen uptake measurement.
  • The review separated interval duration, recovery type, and pacing pattern.

What limits my confidence in the findings?

The limitations

  • The review only searched 2 databases.
  • The source did not report pre-registration, publication bias assessment, or GRADEGRADE, which stands for Grading of Recommendations Assessment, Development and Evaluation, is a standardised and structured approach used to assess the certainty of evidence in meta-analyses. It evaluates how “confident” researchers are in the results of studies and the recommendations that follow from them. GRADE rates a body of evidence as “high”, “moderate”, “low”, or “very low” certainty using a set of standardised criteria. certainty ratings.
  • The review examined short-term oxygen uptake, not long-term training adaptation or race performance.
  • The included studies varied widely in sport, protocol design, participant characteristics, and outcome definitions.
  • Many included studies were small, and the evidence was not runner-only.
  • Time near VO2max is a surrogate outcome. Useful, yes. A finish-line photo, no.

Funding and conflicts

Who funded the study?

The authors reported that no funding was received for the preparation of the article.

The authors also reported no conflicts of interestA conflict of interest happens when a person or group has a personal, financial, or professional interest that could influence their judgment. It does not always mean they did something wrong. But it can create bias or make others question whether the decision or result is fully fair and trustworthy.. That lowers concern about obvious commercial influence, but it does not remove the usual issues in this area: small studies, varied protocols, and enough exercise-science heterogeneity to make a spreadsheet quietly weep.

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