REF-1274 · Renwick et al., 2024 · Sports Medicine · Paper · PubMed

Am I a VO2max non-responder?

One block cannot show it: in 24 controlled trials most of the spread in VO2max change was measurement error, with no strong evidence of true between-person differences (A-, from the abstract).

Main caveat: Read from the abstract only. The 24 studies, their populations and programmes, the SDs of change in each arm, the pooled SDIR² with its interval and the…
fairly strong evidenceMeasured on non-athletes and recreational people

Renwick, Gurd and colleagues ran what they call the first systematic review and meta-analysis of inter-individual differences in VO2max trainability that used only studies with a non-exercising comparator group.

They searched EMBASE, PubMed and SCOPUS (32,968 records) and included 24 studies of standardised, supervised aerobic training that reported absolute or relative VO2max, change scores for the exercise and the non-exercise groups, and the SD of change for every group.

From the SDs of change they calculated the SD of individual response (SDIR) — by its usual definition the square root of the exercise arm's variance of change minus the control arm's (REF-430), that is, the spread of true responses left once test error and within-person variation are removed.

Three findings: most of the variation in observed change scores after an intervention is measurement error; a single study is generally too small to estimate SDIR with useful accuracy; and pooling SDIR² across studies gave no strong evidence that it is positive.

The authors conclude that there is not strong evidence for inter-individual differences in VO2max trainability across single interventions, and that clinically relevant predictors of the VO2max response are therefore unlikely to be found.

Our reading: the wide range of change seen in single-arm programmes such as HERITAGE (REF-429) cannot by itself show "high" and "low" responders; one person's change after one block is mostly the group's mean change plus noise.

No strong evidence for a positive SDIR is not proof that it is zero, and the paper does not ask whether someone who did not improve would improve on a different dose or intensity.

Protocol

Design: systematic review and meta-analysis, registered on the Open Science Framework (10.17605/OSF.IO/X9VU3).
Search: EMBASE, PubMed and SCOPUS; two concepts, aerobic exercise training and VO2max; 32,968 records; n = 24 studies included (the participant total is not in the abstract).
Inclusion: human participants; standardised and supervised exercise training; absolute or relative VO2max reported; a non-exercise comparator group; VO2max change scores for both the exercise and the non-exercise groups; the SD of change for all groups.
Analysis: SDIR estimated per study, and SDIR² meta-analysed across studies. Search dates, the meta-analytic model and the handling of negative SDIR² values are not in the abstract.
Not in the abstract: populations (age, sex, training status), training programmes and durations, the mean VO2max change, the SDs of change in the exercise and control arms, the pooled SDIR² with its interval, heterogeneity.
Funding and interests: funding to BJG from the Natural Sciences and Engineering Research Council of Canada (NSERC; grant no. 402635); the authors declare no competing interests; data available from the corresponding author on reasonable request.

Key Results

Question (abstract)Result
Records screened → studies included32,968 → 24
Where the variation in observed VO2max change scores comes fromthe majority is measurement error
Can one study estimate SDIR?not with sufficient accuracy, because sample sizes are generally small
Pooled SDIR² across the 24 studiesno strong evidence for a positive value (estimate and interval not in the abstract)
Authors' conclusionnot strong evidence for inter-individual differences in VO2max trainability across single interventions; clinically relevant predictors of the VO2max response unlikely to be discovered
SD of change in the exercise arms vs the control armsnot in the abstract
Mean VO2max gainnot in the abstract

Mechanisms

Measured: the SD of VO2max change in exercising arms against non-exercising arms in 24 studies; the abstract reports the direction (most of the observed variation is measurement error), not the sizes.
Authors' interpretation: because true between-person differences in VO2max trainability were not shown across single interventions, predictors of the VO2max response (genetic or otherwise) are unlikely to prove clinically relevant.
Inference: a control arm's SD of change holds test error, day-to-day biological variation and whatever happened in life between the two tests. A single-arm programme cannot separate any of that from true response, which is why HERITAGE's range of "little or none to more than 1.0 L/min" (REF-429) describes observed change, not trainability.It fits REF-498: when 42 untrained adults did the same 8-week programme twice, the individual VO2max response barely repeated (ICC 0.19).
Inference: "no strong evidence for a positive SDIR" is an absence of evidence. With studies this small (the authors' second finding), a modest true spread could exist and go undetected.
Inference: the paper is about the spread around the mean of one programme. It does not say everyone gains the same from every programme: the mean gain itself depends on dose and intensity (REF-749, REF-1230, REF-1277).

Practical Application

Am I a VO2max non-responder? One block cannot show it: in 24 controlled trials most of the spread in VO2max change was measurement error, with no strong evidence of true between-person differences (A-, from the abstract).
Forecast with the group number, then let repeated readings speak. When an athlete asks how much their VO2max will rise, give the mean gain for their calibre and dose (REF-1276 for young non-athletes against no-exercise controls; for trained athletes the base holds only an added effect, +2.5 mL/kg/min for adding above-threshold work, REF-989) and say that individual results scatter around it, mostly from measurement noise; never promise a personal multiplier and never call a weak first block a trait (inference from this paper and REF-498).
Do not read a large SD of change as proof of individual response. An SD of change with no control arm beside it — REF-421's 15-min power +4.9 (8.7)%, or HERITAGE's range (REF-429) — cannot separate true response from test noise, day-to-day variation and life between tests (inference from this paper and REF-430).
Judge a lever over more than one block. Not from this paper; the base's own practice (SYNTH-42): judge a lever over 2-3 blocks with the same benchmark before calling the athlete a non-responder to it.
What it does not say: that a person who did not improve cannot improve. Raising the dose or the intensity removed apparent non-response in untrained adults (REF-996, REF-995, REF-1277); this paper does not test that.

Limitations

Read from the abstract only. The 24 studies, their populations and programmes, the SDs of change in each arm, the pooled SDIR² with its interval and the heterogeneity could not be checked.
Small studies. The authors say single-study sample sizes are generally small; the pooled estimate is imprecise, and no strong evidence of a positive SDIR is not evidence that it is zero.
Selection on reporting. Only studies reporting the SD of change in both arms were eligible; whether those differ from the rest is unknown.
One programme at a time. Whether a person's response repeats, or depends on the stimulus, is outside the question (REF-498, REF-997).
VO2max only. Time trial, threshold power and economy are not covered.
Wording. The conclusion's "existence of VO2max trainability" means inter-individual differences in trainability (the objective's words), not whether VO2max can be trained; read alone, the sentence can be misquoted as "VO2max is not trainable".
Funding and interests: Natural Sciences and Engineering Research Council of Canada (NSERC; grant no. 402635) to BJG; the authors declare no competing interests. No device maker, federation or data platform is named among the funders.
How this entry was checked and changed
Why this level

a meta-analysis restricted to controlled studies, which is the design a responder question needs, held below A because the authors describe the included studies as generally small and the pooled SDIR, its interval, the participant total and the heterogeneity are not in the abstract; read from the abstract (closed access; an accepted manuscript listed by OpenAlex in the Robert Gordon University repository sits behind a bot-check page and could not be read)