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Cited by 269Cardiovascular and exercise physiologySports Performance and TrainingPhysical Activity and Health

&OV0312;O2 reserve and the minimal intensity for improving cardiorespiratory fitness

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SWAIN, DAVID P., FRANKLIN, BARRY A.·2002·Medicine & Science in Sports & Exercise
DOI 10.1097/00005768-200201000-00023
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Abstract

PURPOSE: The American College of Sports Medicine has stated that aerobic training needs to occur at a minimum threshold intensity of 50% VO(2max) for most healthy adults and at 40% VO(2max) for those with a very low initial fitness. Recently, the concept of VO(2) reserve (%VO(2R), i.e., a percentage of the difference between maximum and resting VO(2)) has been introduced for prescribing exercise intensity. This analysis was designed to determine the threshold intensity for improving cardiorespiratory fitness expressed as %VO(2R) units. METHODS: Previous studies in healthy subjects (N = 18) that evaluated the results of training at low-to-moderate intensities (i.e., < or = 60% VO(2max)) were identified. The original studies described the intensity of exercise variously as %VO(2max), %HRR, %HR(max), or as a specific HR value. In each case, the intensity was translated into %VO(2R) units. RESULTS: Exercise training intensities below approximately 45% VO(2R) were consistently ineffective at increasing VO(2max) in studies that used subjects with mean initial VO(2max) values > 40 mL x min(-1) x kg(-1). In studies using subjects with mean initial VO(2max) values < 40 mL x min(-1) x kg(-1), no intensity was found to be ineffective. For this latter group of subjects, the lowest intensities examined were approximately 30% VO(2R). CONCLUSION: Although evidence for a threshold intensity was not strong, this analysis of training studies supports the use of 45% VO(2R) as a minimal effective training intensity for higher fit subjects and 30% VO(2R) for lower fit subjects.

AI snapshot

Written from the paper’s full text.

TL;DR

This analysis converted low-to-moderate training intensities from 18 prior studies into %VO2 reserve units to estimate the minimal intensity needed to raise VO2max. It supports roughly 45% VO2R for higher-fit subjects and roughly 30% VO2R for lower-fit subjects, while noting that evidence for a strict threshold is not strong.

Key findings

  • For groups with mean initial VO2max above 40 mL·min⁻¹·kg⁻¹, training below about 45% VO2R was consistently ineffective at increasing VO2max; intensities above this level generally produced improvements.
  • For groups with mean initial VO2max below 40 mL·min⁻¹·kg⁻¹, every examined training intensity produced significant VO2max gains, with the lowest intensities around 28–32% VO2R; the proposed minimal effective intensity was about 30% VO2R.
  • When translated back to %VO2max, 30% VO2R in lower-fit groups (mean VO2max 28.9 mL·min⁻¹·kg⁻¹) corresponded to about 38% VO2max, and 45% VO2R in higher-fit groups (mean VO2max 44.7 mL·min⁻¹·kg⁻¹) corresponded to about 49% VO2max, close to earlier ACSM guidelines of 40% and 50% VO2max.
  • Among 15 studies comparing two or more intensities, 5 found significantly greater VO2max improvement at the higher intensity and 8 showed a nonsignificant trend in the same direction.

Methods

  • The author identified 18 studies of healthy adults from ACSM position stands, a MEDLINE search, and cross-referenced bibliographies; inclusion required pre- and post-training VO2max measurement and at least one group training at approximately ≤60% VO2max.
  • Reported intensities were converted into %VO2R: %HRR was treated as equivalent to %VO2R; %VO2max was converted using gross exercise VO2 and an assumed resting VO2 of 3.5 mL·min⁻¹·kg⁻¹; %HRmax was converted with a formula derived from heart rate/VO2 data.
  • Training groups were collated by initial VO2max categories and translated intensity to examine whether a minimal effective intensity differed by fitness level.

Limitations

  • The paper states that translating prior intensities into %VO2R was indirect, especially for studies reporting specific heart rates or %HRmax, and that all conversions used group means rather than individual data; the findings are therefore preliminary.
  • The paper states that the higher-fit groups showing no improvement came from small studies with only 4–9 subjects per group and about 100 min·wk⁻¹ for 5–10 weeks, so low statistical power or insufficient training volume may explain the negative results.
  • The paper states that no threshold was apparent for lower-fit groups because intensities below 30% VO2R were not routinely tested; it also notes that between-study differences in duration, frequency, and program length make comparisons tenuous. Evident from the text, this is a narrative collation rather than a formal meta-analysis.

Model-written summary. Check it against the paper before relying on it.

Integrity signals

Registry

Crossref · 10.1097/00005768-200201000-00023

Cites

33 of 33 references verified0 citation errors · 0 not checkable

Statistics

Nothing to recompute.

Claims the paper makes

0 of 10 cited sources checked · 0 supported · 0 flagged

  • Findingown data

    In studies whose subjects had mean initial maximal oxygen consumption above 40 mL/min/kg, training intensities below about 45% oxygen consumption reserve consistently failed to increase maximal oxygen consumption.

    “Exercise training intensities below approximately 45% V ˙O2 R were consistently ineffective at increasing V ˙O2max in studies that used subjects with mean initial V ˙O2max values Ͼ 40 mL•min Ϫ1 •kg Ϫ1 .”
    Quote in the paperSubstantial claim
  • Findingown data

    For subjects with mean initial maximal oxygen consumption below 40 mL/min/kg, the lowest training intensities examined were about 30% oxygen consumption reserve.

    “For this latter group of subjects, the lowest intensities examined were approximately 30% V ˙O2 R.”
    Quote in the paperNot a substantial claim
  • Findingown data

    The analysis found fairly strong support for the thesis that higher training intensities produce greater percentage improvements in aerobic capacity than lower intensities, even when lower-intensity exercise is performed long enough to accomplish the same total work.

    “This analysis found fairly strong support for the thesis that training at higher intensities results in greater percentage improvements in aerobic capacity than does training at lower intensities, even when the lower intensity exercise is performed with a sufficient duration to accomplish the same total amount of work (i.e., duration was varied inversely with intensity so that work output was held”
    Quote in the paperSubstantial claim
  • Findingown data

    In studies whose subjects had mean initial maximal oxygen consumption below 40 mL/min/kg, no training intensity was found to be ineffective at increasing maximal oxygen consumption.

    “In studies using subjects with mean initial V ˙O2max values Ͻ 40 mL•min Ϫ1 •kg Ϫ1 , no intensity was found to be ineffective.”
    Quote in the paperSubstantial claim
  • Findingown data

    The data show a trend toward greater percentage improvements in maximal oxygen consumption with higher training intensities compared with lower intensities.

    “Table 1 reveals a trend for greater percentage improvements in V ˙O2max when training at higher versus lower exercise intensities.”
    Quote in the paperSubstantial claim
  • May combine two claims. 13
  • Classified as probably not a substantial claim. 4
  • The quote only partly states this claim. 1

  • May combine two claims.

    Findingreasoning

    The average maximal oxygen consumption for groups with values below 40 mL/min/kg was 28.9 mL/min/kg, and translating 30% oxygen consumption reserve using this average yields 38% of maximal oxygen consumption.

    “The average V ˙O2max for all of these groups was 28.9 mL•min Ϫ1 •kg Ϫ1 .Translating the training intensity to %V ˙O2max units yields: [0.30(28.9Ϫ 3.5) ϩ 3.5]/28.9ϭ 38% of V ˙O2max .”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    Of the 10 remaining studies, 8 showed a nonsignificant greater improvement in the higher-intensity group, and 7 of those 8 controlled total work.

    “Of the 10 remaining studies, 8 exhibited a nonsignificant greater improvement in the higherintensity group (and 7 of these 8 studies controlled the total amount of work between groups).”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    Five of the 15 studies comparing two or more progressive intensities found significantly greater improvement in the higher-intensity group, and three of those five controlled total work.

    “Five of the 15 studies that compared two or more progressive intensities found a statistically greater improvement in the higher-intensity group (and three of these five studies controlled the total amount of work between groups).”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingnone given

    Groups with mean initial maximal oxygen consumption above 40 mL/min/kg showed an intensity-dependent response: those training below 46% oxygen consumption reserve consistently did not improve, while those above that value consistently improved.

    “Groups with mean initial V ˙O2max values above 40 mL•min Ϫ1 •kg Ϫ1 exhibited an intensity-dependent response, in that those who exercised at intensities below 46% V ˙O2 R consistently demonstrated a lack of improvement, whereas those who exercised at intensities above this value consistently experienced improvements in V ˙O2max .”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    No threshold intensity was apparent for less fit subject groups, because all studies with subjects having aerobic capacities below 40 mL/min/kg found statistically significant increases in maximal oxygen consumption regardless of training intensity.

    “No threshold intensity was apparent for less fit subject groups, as all studies using subjects with aerobic capacities less than 40 mL•min Ϫ1 •kg Ϫ1 found statistically significant increases in V ˙O2max , regardless of training intensity.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingreasoning

    The average maximal oxygen consumption for groups with values above 40 mL/min/kg was 44.7 mL/min/kg, and translating 45% oxygen consumption reserve using this average yields 49% of maximal oxygen consumption.

    “The average V ˙O2max for all of these groups was 44.7 mL•min Ϫ1 •kg Ϫ1 .Translating the training intensity to %V ˙O2max units yields: [0.45(44.7 Ϫ 3.5) ϩ 3.5]/44.7 ϭ 49% of V ˙O2max .”
    Quote in the paperSubstantial claim

  • Classified as probably not a substantial claim. May combine two claims.

    Premisecitation

    The American College of Sports Medicine's 1990 position stand recommended a minimum training intensity of 50% of heart rate reserve or maximal oxygen consumption for most adults and 40% for individuals with low initial aerobic fitness.

    “The American College of Sports Medicine has stated that aerobic training needs to occur at a minimum threshold intensity of 50% V ˙O2max for most healthy adults and at 40% V ˙O2max for those with a very low initial fitness.”
    • Also stated in: § Abstract · hedged
      “In its 1990 position stand (1), the American College of Sports Medicine (ACSM) suggested a threshold intensity for training at 50% of HRR or V ˙O2max for most adults and 40% of HRR or V ˙O2max for individuals with a low initial level of aerobic fitness.”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites [1]

      Couldn’t be matched to a paper in Crossref, so it can’t be checked.

  • Classified as probably not a substantial claim. May combine two claims.

    Interpretationreasoning

    The three studies that reported no improvement in maximal oxygen consumption after training had only four to nine subjects per group, and larger sample sizes might have produced statistically significant improvements.

    “However, the three studies that reported no improvement in V ˙O2max after training (8,9,18) had only four to nine subjects per group.If a greater number of subjects had been tested, statistically significant improvements in V ˙O2max may have been attained.”
    Quote in the paperSubstantial claim0 of 3 sources checked
    • cites [8]

      Couldn’t be matched to a paper in Crossref, so it can’t be checked.

    • cites [9]

      Couldn’t be matched to a paper in Crossref, so it can’t be checked.

    • cites [18] source

  • Classified as probably not a substantial claim. May combine two claims.

    Interpretationnone given

    Higher training intensities are generally more effective at improving maximal oxygen consumption, but unusually vigorous exercise may not be recommended because of injury, cardiovascular complications, and compliance issues.

    “A further conclusion is that higher intensities of training are generally more effective at improving V ˙O2max ; however, unconventionally vigorous exercise may not be recommended in consideration of injury, cardiovascular complications, and compliance issues.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Interpretationreasoning

    The 1957 Karvonen et al. study did not firmly establish a threshold intensity because it had only six subjects, only three trained below 70% heart rate reserve, and it did not measure maximal oxygen consumption.

    “However, only six subjects participated in the experiment, and only three of these trained at an intensity less than 70% of HRR.Moreover, the maximum oxygen consumption of the subjects was not measured.Thus, although the study serves as the foundation for later work, it did not firmly establish a threshold intensity.”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites [23] source

  • May combine two claims.

    Premisecitation

    Heart rate reserve does not correspond to the same exercise intensity as maximal oxygen consumption percentage, but it does correspond to oxygen consumption reserve percentage.

    “Recent research has demonstrated that %HRR does not provide equivalent exercise intensities to %V ˙O2max but is instead equivalent to a percentage of the difference between maximum and resting oxygen consumption, i.e., to a percent-age of oxygen consumption reserve, %V ˙O2 R (33,34).”
    Quote in the paperSubstantial claim0 of 2 sources checked
    • cites [33] source
    • cites [34]

      Couldn’t be matched to a paper in Crossref, so it can’t be checked.

  • The quote only partly states this claim.

    Interpretationreasoning

    It is accurate to state that training intensities of 30% or more oxygen consumption reserve routinely improved aerobic capacity.

    “It would be accurate to simply state that training intensities of 30% or more of V ˙O2 R routinely resulted in improved aerobic capacity.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Interpretationreasoning

    It is more appropriate to state that training above 45% oxygen consumption reserve generally improves aerobic capacity than to call 45% a true threshold for higher fit subjects.

    “Rather than stating that 45% of V ˙O2 R represents a true threshold for this population, it might be more appropriate to simply state that exercise training above 45% of V ˙O2 R generally results in improved aerobic capacity.”
    Quote in the paperSubstantial claim

  • Probably not a substantial claim: may not pass S2 (checkable).

    Study design and conductreasoning

    The present findings should be considered preliminary until confirmed or refuted by training studies that set exercise intensity in oxygen consumption reserve units.

    “Thus, present findings should be considered preliminary until they are confirmed or refuted by training studies that establish exercise intensity in %V ˙O2 R units.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Interpretationown data

    The analysis established reasonable support for a threshold at 45% oxygen consumption reserve for subjects with moderate-to-high initial fitness above 40 mL/min/kg, though it is prudent to call this an effective minimal training intensity rather than a threshold.

    “The current analysis has established that a reasonable level of support exists for a threshold at 45% of V ˙O2 R for subjects of a moderate-tohigh initial fitness level (defined here as Ͼ 40 mL•min Ϫ1 •kg Ϫ1 ), although it would be prudent to refer to this as an effective minimal training intensity rather than as a threshold per se.”
    Quote in the paperSubstantial claim
15 of 15

  • The authors state this as an assumption.

    Heart rate reserve values are equivalent to oxygen consumption reserve values.

    “Some studies reported the intensity as %HRR (2,3,12,14,24,30), and these were assumed to provide equivalent values in %V ˙O2 R units (33,34).”

  • The authors state this as an assumption.

    The average resting oxygen consumption of the subjects was 3.5 mL/min/kg.

    “in which the value 3.5 mL•min Ϫ1 •kg Ϫ1 was assumed to be the average resting V ˙O2 of the subjects.”
2 of 2

Claims other papers make about this one

Each is checked against this paper’s own text: does it say what the citing paper says it does?

  • For deconditioned/inactive individuals or patients with cardiovascular disease, the minimum or threshold intensity for improving cardiorespiratory fitness corresponds to approximately 60%-70% of the highest heart rate achieved during peak or symptom-limited exercise testing.

    “For deconditioned/inactive individuals or patients with CVD, the minimum or threshold intensity for improving CRF corresponds to ∼60%–70% of the highest HR achieved during peak or symptom-limited exercise testing [ 29 , 30 ].”

    From Physical activity, cardiorespiratory fitness, and cardiovascular health: A clinical practice statement of the American Society for Preventive Cardiology Part II: Physical activity, cardiorespiratory fitness, minimum and goal intensities for exercise training, prescriptive methods, and special patient populations (2022) · cites this paper as [29]

    The Discussion (page unavailable) identifies about 30% VO₂ reserve as the minimal effective intensity observed for less-fit subjects; the Methods give a conversion that makes this approximately 60% of maximal heart rate. The paper does not establish a 60%–70% threshold for this group, and its analysis concerns healthy subjects rather than patients with cardiovascular disease or symptom-limited testing. (LLM, conf=0.87)

    Experimental — accuracy not yet measured

  • For elderly and low-fit individuals, an RPE of 12-13 is an appropriate starting point for aerobic exercise prescription.

    “When developing exercise prescriptions for elderly and low-fit individuals, several studies established that using an RPE of 12-13 is an appropriate starting point for aerobic exercise prescription (30,31).”

    From Ventilatory Threshold Related to VO2reserve, Heart Rate Reserve, and Rating of Perceived Exertion in a Large Varied Sample (2023) · cites this paper as [31]

    The Conclusions (page not provided) report that people with low baseline aerobic capacity improved fitness at intensities as low as 30% of VO₂ reserve, and the paper includes studies of older adults. It does not express a recommended starting intensity as RPE 12–13, so that specific prescription is unsupported. (LLM, conf=0.82)

    Experimental — accuracy not yet measured

  • Moderate-intensity aerobic exercise at RPE 12-13 corresponds directly to VT, and above that intensity exercise becomes high intensity.

    “Applicability of VT to exercise prescription is predicated on the well-established notion that moderate-intensity aerobic exercise at an RPE of 12-13 corresponds directly to VT and that above this intensity exercise becomes high intensity (31,32).”

    From Ventilatory Threshold Related to VO2reserve, Heart Rate Reserve, and Rating of Perceived Exertion in a Large Varied Sample (2023) · cites this paper as [31]

    The Abstract and Discussion describe exercise intensity using oxygen-consumption measures, heart-rate reserve, and METs. Searches for RPE 12–13, ventilatory threshold, and their relationship found no passage establishing that RPE 12–13 corresponds to VT or that exercise above VT becomes high intensity. The paper’s discussion of a minimal effective training intensity addresses a different threshold. (LLM, conf=0.76)

    Experimental — accuracy not yet measured

Cites

Flagged first, then by citations

Research works printed but not linked: 11

  1. 1990, Med Sci Sports Exerc, 22, 265
  2. Burke, 1975, Res Quart, 46, 31
  3. Davies, 1971, Int Z Angew Physiol, 29, 299
  4. Devries, 1971, Geriatrics, 26, 94
  5. Edwards, 1974, Med Sci Sports, 6, 14
  6. Faria, 1970, Res Q, 41, 44
  7. Gaesser, 1984, Med Sci Sports Exerc, 16, 269
  8. Hagberg, 1986, Acta Med Scand, 711, 131
  9. Karvonen, 1957, Ann Med Exp Biol Fenn, 35, 307
  10. Pollock, 1998, Med Sci Sports Exerc, 30, 975
  11. Swain, 1994, Med Sci Sports Exerc, 26, 112

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Related

Authors
SWAIN, D. P., & FRANKLIN, B. A.
Affiliations
Beaumont Health (US)
ORCID
FRANKLIN, BARRY A.
Venue
Medicine & Science in Sports & Exercise
Publisher
Ovid Technologies (Wolters Kluwer Health)
Published
2002-01
Volume
34
Issue
1
Pages
152-157
ISSN
0195-9131 (ISSN-L)
DOI
10.1097/00005768-200201000-00023
OpenAlex
W2027535482
Cited by
269
References
30
Citations by year
2026: 15 · 2025: 14 · 2024: 13 · 2023: 15 · 2022: 8 · 2021: 13 · 2020: 17 · 2019: 12 · 2018: 14 · 2017: 14 · 2016: 9 · 2015: 9 · 2014: 7 · 2013: 14 · 2012: 17
FWCI
16.69
Type
journal article
Language
en
Open access
Locations
  • Medicine & Science in Sports & Exercise (publishedVersion)
  • PubMed (publishedVersion)
  • ODU Digital Commons (Old Dominion University) (submittedVersion)
Topics
  • Health Sciences › Medicine › Complementary and alternative medicine › Cardiovascular and exercise physiology
  • Health Sciences › Medicine › Orthopedics and Sports Medicine › Sports Performance and Training
  • Health Sciences › Medicine › Physiology › Physical Activity and Health
Keywords
exercise intensity thresholds, cardiorespiratory fitness, aerobic exercise, VO2max, exercise prescription, low-intensity training, heart rate reserve
MeSH terms
Adaptation, Physiological, Adolescent, Adult, Aged, Aged, 80 and over, Female, Heart Rate, Humans, Male, Middle Aged, Oxygen Consumption, Physical Education and Training, Physical Fitness, Anaerobic Threshold, Program Evaluation, Exercise

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