A comparison of three maximal treadmill exercise protocols

Exercise Stress Testing in Athletes

Exercise stress testing (EST) is indicated for diagnostic and prognostic purposes in the general population. In athletes, stress tests can also be useful to inform the risk of high-intensity training and competition, to assess athletic conditioning, and to refine training regimens. Many specific indications for EST are unique to athletes. Treadmill and cycle ergometer protocols each have their strengths and disadvantages; extensive protocol customization may be necessary to answer the clinical question at hand. A comprehensive understanding of the available tools for exercise testing, their strengths, and their limitations is crucial to providing cardiovascular care to athletic individuals.

Effect of Cardiorespiratory Fitness on Verifying VO2max in Middle-aged and Older Adults

We investigated the effect of cardiorespiratory fitness (CRF) on the probability of achieving the verification criterion to confirm that VO₂max was obtained in a sample of middle-aged to older adults. Data from twelve men and nine women (60.7±8.5 years, VO₂max: 34.8±9.4 mL/kg/min) were used for analysis. Participants had their VO₂max measured via a maximal graded exercise test and confirmed using a verification bout on a cycle ergometer. Logistic regression was used to evaluate the effect of CRF (VO₂max) on the probability a participant would successfully achieve the verification criterion. Odds ratios are reported to quantify the effect size. No statistically significant relationship was observed between CRF and achieving the verification criterion (β=.081, SE=.0619, Wald=1.420, p=.156). Estimated odds ratio for the effect of CRF on the verification criterion indicated an increase of 8% [Exp(β)=1.08, 95% CI (0.96, 1.22)] in the probability of achieving the verification criterion given a one unit increase in VO₂max. Each 1 mL/kg/min increase in VO₂max results in an 8% increase in the chance that an individual achieves the verification criterion confirming that VO₂max was obtained. Therefore, CRF is likely of practical significance and should be considered when deciding to use a verification trial.

Incremental and decremental cardiopulmonary exercise testing protocols produce similar maximum oxygen uptake in athletes

The aim of the study was to evaluate and compare the maximal oxygen uptake (\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\dot{\mathrm{V}}$$\end{document}V˙O_2max) achieved during incremental and decremental protocols in highly trained athletes. Nineteen moderate trained runners and rowers completed, on separate days, (i) an initial incremental \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\dot{\mathrm{V}}$$\end{document}V˙O_2max test (INC) on a treadmill, followed by a verification phase (VER); (ii) a familiarization of a decremental test (DEC); (iii) a tailored DEC; (iv) a test with decremental and incremental phases (DEC-INC); (v) and a repeated incremental test (INC_F). During each test \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\dot{\mathrm{V}}$$\end{document}V˙O₂, carbon dioxide production, ventilation, heart and breath rates and ratings of perceived exertion were measured. No differences were observed in \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\dot{\mathrm{V}}$$\end{document}V˙O_2max between INC (61.3 ± 5.2 ml kg⁻¹ min⁻¹) and DEC (61.1 ± 5.1 ml kg⁻¹ min⁻¹; average difference of ~ 11.58 ml min⁻¹; p = 0.831), between INC and DEC-INC (60.9 ± 5.3 ml kg⁻¹ min⁻¹; average difference of ~ 4.8 ml min⁻¹; p = 0.942) or between INC and INC_F (60.7 ± 4.4 ml kg⁻¹ min⁻¹; p = 0.394). \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\dot{\mathrm{V}}$$\end{document}V˙O_2max during VER (59.8 ± 5.1 ml kg⁻¹ min⁻¹) was 1.50 ± 2.20 ml kg⁻¹ min⁻¹ lower (~ 2.45%; p = 0.008) compared with values measured during INC. The typical error in the test-to-test changes for evaluating \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\dot{\mathrm{V}}$$\end{document}V˙O_2max over the five tests was 2.4 ml kg⁻¹ min⁻¹ (95% CI 1.4–3.4 ml kg⁻¹ min⁻¹). Decremental tests do not elicit higher \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\dot{\mathrm{V}}$$\end{document}V˙O_2max than incremental tests in trained runners and rowers, suggesting that a plateau in \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\dot{\mathrm{V}}$$\end{document}V˙O₂ during the classic incremental and verification tests represents the maximum ceiling of aerobic power.

The Oxygen Uptake Plateau-A Critical Review of the Frequently Misunderstood Phenomenon

A flattening of the oxygen uptake–work rate relationship at severe exercise indicates the achievement of maximum oxygen uptake \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\left({\text{VO}}_{2\max } \right)$$\end{document}VO2max. Unfortunately, a distinct plateau \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\left( {{{\text{VO}}}_{2} {\text{pl}}} \right)$$\end{document}VO2pl at \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$${{\text{VO}}}_{2\max }$$\end{document}VO2maxis not found in all participants. The aim of this investigation was to critically review the influence of research methods and physiological factors on the \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$${{\text{VO}}}_{2} {\text{pl}}$$\end{document}VO2pl incidence. It is shown that many studies used inappropriate definitions or methodical approaches to check for the occurrence of a \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$${{\text{VO}}}_{2} {\text{pl}}$$\end{document}VO2pl. In contrast to the widespread assumptions it is unclear whether there is higher \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$${{\text{VO}}}_{2} {\text{pl}}$$\end{document}VO2pl incidence in (uphill) running compared to cycling exercise or in discontinuous compared to continuous incremental exercise tests. Furthermore, most studies that evaluated the validity of supramaximal verification phases, reported verification bout durations, which are too short to ensure that \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$${{\text{VO}}}_{2\max }$$\end{document}VO2max have been achieved by all participants. As a result, there is little evidence for a higher \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$${{\text{VO}}}_{2} {\text{pl}}$$\end{document}VO2pl incidence and a corresponding advantage for the diagnoses of \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$${{\text{VO}}}_{2\max }$$\end{document}VO2max when incremental tests are supplemented by supramaximal verification bouts. Preliminary evidence suggests that the occurrence of a \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$${{\text{VO}}}_{2} {\text{pl}}$$\end{document}VO2pl in continuous incremental tests is determined by physiological factors like anaerobic capacity, \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$${{\text{VO}}}_{2}$$\end{document}VO2-kinetics and accumulation of metabolites in the submaximal intensity domain. Subsequent studies should take more attention to the use of valid \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$${{\text{VO}}}_{2} {\text{pl}}$$\end{document}VO2pl definitions, which require a cut-off at ~ 50% of the submaximal \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$${{\text{VO}}}_{2}$$\end{document}VO2 increase and rather large sampling intervals. Furthermore, if verification bouts are used to verify the achievement of \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$${{\text{VO}}}_{{2{\text{peak}}}}$$\end{document}VO2peak/\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$${{\text{VO}}}_{2\max }$$\end{document}VO2max, it should be ensured that they can be sustained for sufficient durations.

Is a verification phase useful for confirming maximal oxygen uptake in apparently healthy adults? A systematic review and meta-analysis

BACKGROUND

The 'verification phase' has emerged as a supplementary procedure to traditional maximal oxygen uptake (VO2max) criteria to confirm that the highest possible VO2 has been attained during a cardiopulmonary exercise test (CPET).

OBJECTIVE

To compare the highest VO2 responses observed in different verification phase procedures with their preceding CPET for confirmation that VO2max was likely attained.

METHODS

MEDLINE (accessed through PubMed), Web of Science, SPORTDiscus, and Cochrane (accessed through Wiley) were searched for relevant studies that involved apparently healthy adults, VO2max determination by indirect calorimetry, and a CPET on a cycle ergometer or treadmill that incorporated an appended verification phase. RevMan 5.3 software was used to analyze the pooled effect of the CPET and verification phase on the highest mean VO2. Meta-analysis effect size calculations incorporated random-effects assumptions due to the diversity of experimental protocols employed. I2 was calculated to determine the heterogeneity of VO2 responses, and a funnel plot was used to check the risk of bias, within the mean VO2 responses from the primary studies. Subgroup analyses were used to test the moderator effects of sex, cardiorespiratory fitness, exercise modality, CPET protocol, and verification phase protocol.

RESULTS

Eighty studies were included in the systematic review (total sample of 1,680 participants; 473 women; age 19-68 yr.; VO2max 3.3 ± 1.4 L/min or 46.9 ± 12.1 mL·kg-1·min-1). The highest mean VO2 values attained in the CPET and verification phase were similar in the 54 studies that were meta-analyzed (mean difference = 0.03 [95% CI = -0.01 to 0.06] L/min, P = 0.15). Furthermore, the difference between the CPET and verification phase was not affected by any of the potential moderators such as verification phase intensity (P = 0.11), type of recovery utilized (P = 0.36), VO2max verification criterion adoption (P = 0.29), same or alternate day verification procedure (P = 0.21), verification-phase duration (P = 0.35), or even according to sex, cardiorespiratory fitness level, exercise modality, and CPET protocol (P = 0.18 to P = 0.71). The funnel plot indicated that there was no significant publication bias.

CONCLUSIONS

The verification phase seems a robust procedure to confirm that the highest possible VO2 has been attained during a ramp or continuous step-incremented CPET. However, given the high concordance between the highest mean VO2 achieved in the CPET and verification phase, findings from the current study would question its necessity in all testing circumstances.

PROSPERO REGISTRATION ID

CRD42019123540.

Does heart rate response confirm the attainment of maximal oxygen uptake in adults 45 years and older?

PURPOSE

To test the efficacy of a plateau in heart rate (HR_plat) as an effective indicator for confirming [Formula: see text]max attainment in a middle-aged to older sample.

METHODS

Nine men and eleven women (age 60 ± 8.5 years, [Formula: see text]max 35.9 ± 9.4 ml/kg/min, N = 20) completed a single [Formula: see text]max test on both the treadmill and cycle ergometer.[Formula: see text]max was confirmed using a plateau in [Formula: see text] ([Formula: see text]_plat) of ≤ 150 ml/min, a verification bout, and HR_plat (≤ 4 bpm).

RESULTS

[Formula: see text]_plat occurred in 100% and 95% of participants on the treadmill and cycle ergometer, respectively. Verification criteria ([Formula: see text]max during verification ≤ 2% of [Formula: see text]max during incremental test) were met by 80% of participants on both modalities. HR_plat was achieved by 90% and 70% of participants on the treadmill and cycle ergometer, respectively.

CONCLUSION

These results suggest that a verification bout is reliable for confirming [Formula: see text]max in older adults on both modalities. In our sample of middle-aged and older adults, [Formula: see text]_plat was the most robust method to assess [Formula: see text]max when indirect calorimetry is available. Although more research is warranted, when indirect calorimetry is not available, a HR_plat of ≤ 4 bpm may be a useful alternative to get an accurate representation of maximal effort in middle-aged and older adults.

Association Between Diet Quality and Cardiorespiratory Fitness in Korean Adults: The 2014-2015 National Fitness Award Project

Cardiorespiratory fitness (CRF) is a strong and meaningful indicator for predicting mortality, including cardiovascular disease, as well as simple physical capacity. Healthy eating is thought to be one of the crucial factors associated with an individual's CRF status, although little research has been done on the relationship between healthy eating and CRF. This study aimed to investigate the association between overall diet quality and CRF among Korean adults. The study involved 937 adults (380 men and 557 women) aged 19‒64 years who participated in the 2014‒2015 Korea Institute of Sports Science Fitness Standards project. Diet quality was assessed by the recommended food score (RFS), and CRF was determined by maximal oxygen uptake (VO2max) during a treadmill exercise test. Multiple regression model analyses were stratified by age (19-34, 35-49, and 50-64 years) and sex, because both factors greatly influence CRF. After multivariate adjustment, only the 19‒34 age group in both sexes showed a positive association between RFS and VO2max. Additionally, when physical activity was adjusted, it was still significant in men but only marginally related in women. Our results suggest that better overall diet quality may be associated with a better CRF among young adults aged 19‒34 years in Korea.

Progress Update and Challenges on V . O2max Testing and Interpretation

The maximal oxygen uptake ( V . O2max) is the primary determinant of endurance performance in heterogeneous populations and has predictive value for clinical outcomes and all-cause mortality. Accurate and precise measurement of V . O2max requires the adherence to quality control procedures, including combustion testing and the use of standardized incremental exercise protocols with a verification phase preceded by an adequate familiarization. The data averaging strategy employed to calculate the V . O2max from the breath-by-breath data can change the V . O2max value by 4-10%. The lower the number of breaths or smaller the number of seconds included in the averaging block, the higher the calculated V . O2max value with this effect being more prominent in untrained subjects. Smaller averaging strategies in number of breaths or seconds (less than 30 breaths or seconds) facilitate the identification of the plateau phenomenon without reducing the reliability of the measurements. When employing metabolic carts, averaging intervals including 15-20 breaths or seconds are preferable as a compromise between capturing the true V . O2max and identifying the plateau. In training studies, clinical interventions and meta-analysis, reporting of V . O2max in absolute values and inclusion of protocols and the averaging strategies arise as imperative to permit adequate comparisons. Newly developed correction equations can be used to normalize V . O2max to similar averaging strategies. A lack of improvement of V . O2max with training does not mean that the training program has elicited no adaptations, since peak cardiac output and mitochondrial oxidative capacity may be increased without changes in V . O2max.

Collective effects of age, sex, genotype, and cognitive status on fitness outcomes

INTRODUCTION

Individuals with Alzheimer's disease (AD) broadly exhibit lower cardiorespiratory fitness (CRF) compared to cognitively healthy older adults. Other factors, such as increasing age and female sex, are also known to track with lower CRF levels. However, it is unclear how these factors together with AD diagnosis and genetic risk (apolipoprotein e4 ; APOE4) collectively affect CRF.

METHODS

Our primary objective was to characterize the collective relationship of age, sex, APOE4 carrier status , and cognitive status (nondemented or AD) with two commonly reported CRF outcomes, VO2 max and oxygen uptake efficiency slope (OUES). To interrogate the unique and combined effect of age, sex, APOE4, and cognitive status on CRF, we pooled multiple datasets and tested several statistical models allowing all possible interactions.

RESULTS

AD diagnosis was consistently associated with lower maximal CRF, which declined with increasing age. APOE4 was also associated with lower maximal CRF (VO2max), but only in male subjects. Submaximal CRF (OUES) was lower in APOE4 carriers of both sexes, although this difference converged in male subjects with advancing age.

DISCUSSION

This multi-cohort analysis (n = 304) suggests that APOE4 carrier status and sex are important considerations for studies that evaluate maximal and submaximal CRF.

The relationship between maximum heart rate in a cardiorespiratory fitness test and in a maximum heart rate test

OBJECTIVES

It is suggested that individuals will not reach their heart rate maximum (HRmax) at an incremental cardiorespiratory fitness (CRF) test and commonly five beats per minute (bpm) are added to the highest heart rate (HR) reached. To our knowledge, there is not sufficient data justifying such estimation. Our aim was to assess whether individuals reached HRmax in an incremental CRF test to exhaustion.

DESIGN AND METHODS

Fifty-one males and 57 females (aged 22-70 years) completed both an incremental CRF test (gradual increase in speed and/or inclination until volitional exhaustion) and a test designed to reach HRmax (with repeated work bouts at high intensity before maximal exertion) ≥48h apart. We investigated the relationship between the highest HR in the two tests using hierarchical linear regression analysis, with HRmax from the HRmax test as a dependent variable, and the highest HR reached at the CRF test (HRcrf), whether maximum oxygen uptake was reached on the CRF test, CRF, sex and age as independent variables.

RESULTS

HRmax was 2.2 (95% confidence interval, 1.5-2.9) bpm higher in the test designed to reach HRmax than in the CRF test (p<0.001). Only HRcrf significantly predicted HRmax, with no contribution of the other variables in the model. HRmax was predicted from the highest HR reached in an incremental CRF test by multiplying HRcrf with 0.967, and adding 8.197 (HRmax=8.197+[0.967×HRcrf]) beats/min.

CONCLUSION

Non-athletes reached close to HRmax in a standard CRF test.

The Maximal Oxygen Uptake Verification Phase: a Light at the End of the Tunnel?

Commonly performed during an incremental test to exhaustion, maximal oxygen uptake (V̇O_2max) assessment has become a recurring practice in clinical and experimental settings. To validate the test, several criteria were proposed. In this context, the plateau in oxygen uptake (V̇O₂) is inconsistent in its frequency, reducing its usefulness as a robust method to determine “true” V̇O_2max. Moreover, secondary criteria previously suggested, such as expiratory exchange ratios or percentages of maximal heart rate, are highly dependent on protocol design and often are achieved at V̇O₂ percentages well below V̇O_2max. Thus, an alternative method termed verification phase was proposed. Currently, it is clear that the verification phase can be a practical and sensitive method to confirm V̇O_2max; however, procedures to conduct it are not standardized across the literature and no previous research tried to summarize how it has been employed. Therefore, in this review the knowledge on the verification phase was updated, while suggestions on how it can be performed (e.g. intensity, duration, recovery) were provided according to population and protocol design. Future studies should focus to identify a verification protocol feasible for different populations and to compare square-wave and multistage verification phases. Additionally, studies assessing verification phases in different patient populations are still warranted.

A comparative study of two protocols for treadmill walking exercise testing in ambulating subjects with incomplete spinal cord injury

STUDY DESIGN

This is a comparative study of two exercise testing protocols.

OBJECTIVES

The objective of this study was to compare maximal oxygen uptake (VO₂ max) and achieved criteria for maximal exercise testing between the Sunnaas Protocol-a newly designed treadmill exercise test protocol-and the Modified Bruce Protocol in persons with incomplete spinal cord injury (SCI).

SETTING

This study was conducted in Sunnaas Rehabilitation Hospital, Norway.

METHODS

Twenty persons (19 men) with incomplete SCI (AIS D) capable of ambulating without assistive devices performed two treadmill walking exercise tests (Sunnaas Protocol and Modified Bruce Protocol) until exhaustion 1-3 days apart. The key differences between the protocols are the smaller increments in speed and shorter duration on each workload in the Sunnaas Protocol. Cardiovascular responses were measured continuously throughout both tests.

RESULTS

The subjects exhibited statistically significantly higher VO₂ max when using the Sunnaas Protocol (37.1±9.9 vs 35.4±9.8 ml kg^-1 min^-1, P=0.01), with a mean between-test difference of 1.8 ml kg^-1 min^-1 (95% confidence interval: 0.49-3.16). There was no significant difference in mean maximal heart rate (HR max). Nineteen (95%) subjects achieved at least three of the four criteria for maximal oxygen uptake using the Sunnaas Protocol. Thirteen (65%) subjects achieved at least three of the criteria using a Modified Bruce protocol.

CONCLUSIONS

The small differences in both VO₂ max and achieved criteria in favor of the Sunnaas Protocol suggest that it could be a useful alternative treadmill exercise test protocol for ambulating persons with incomplete SCI.

Glucose metabolism during the acute prostate cancer treatment trajectory: The influence of age and obesity

BACKGROUND & AIMS

Obesity and age, key risk factors for aggressive prostate cancer, are associated with insulin resistance. Glucose-related parameters in patients with aggressive prostate cancer were compared with 2 reference groups: men of similar age and body mass index (BMI) without cancer, and healthy young men. Acute changes in these parameters following radiation treatment were also evaluated.

METHODS

Nine patients with aggressive prostate cancer underwent metabolic assessments prior to treatment (baseline), 7 and 33 weeks post-baseline (post-treatment initiation). Baseline measures were compared with the 2 reference groups. Evaluations included: 1) fasting and oral glucose tolerance test (OGTT) blood samples for glucose, C-peptide, and insulin, 2) fasting blood samples for triglycerides, cholesterols, leptin, adiponectin, IL-6, and TNF-α, 3) body composition, 4) nutrition, and 5) physical activity.

RESULTS

At baseline, patients had normal fasting glucose concentrations (<5.6 mM; 4.9 ± 1.2 mM) but impaired 2-h OGTT glucose concentrations (>7.8 mM; 8.7 ± 2.9 mM). Both reference groups had normal fasting (matched males: 4.2 ± 0.5 mM; young males: 3.7 ± 0.4 mM) and 2-h OGTT glucose concentrations (matched males: 5.6 ± 1.8 mM; young males: 3.1 ± 0.1 mM) that were significantly lower than patient values. During the OGTT, patients had higher insulin (120 min) and C-peptide (45, 60, 90, 120 min) concentrations compared to the matched males. At 7 weeks, 2-h OGTT glucose concentrations in patients improved to healthy ranges without changes in insulin, C-peptide, IGF-1, IGFBP-3 or other metabolic parameters.

CONCLUSIONS

At baseline patients with aggressive prostate cancer demonstrated impaired glucose tolerance compared with men of similar age and body size. Following treatment, glucose tolerance improved in the absence of changes in expected modifiers of glucose metabolism. These improvements may be related to treatment.

Use of the Wasserman equation in optimization of the duration of the power ramp in a cardiopulmonary exercise test: a study of Brazilian men

This study aimed to analyze the agreement between measurements of unloaded oxygen uptake and peak oxygen uptake based on equations proposed by Wasserman and on real measurements directly obtained with the ergospirometry system. We performed an incremental cardiopulmonary exercise test (CPET), which was applied to two groups of sedentary male subjects: one apparently healthy group (HG, n=12) and the other had stable coronary artery disease (n=16). The mean age in the HG was 47±4 years and that in the coronary artery disease group (CG) was 57±8 years. Both groups performed CPET on a cycle ergometer with a ramp-type protocol at an intensity that was calculated according to the Wasserman equation. In the HG, there was no significant difference between measurements predicted by the formula and real measurements obtained in CPET in the unloaded condition. However, at peak effort, a significant difference was observed between oxygen uptake (V˙O2)peak(predicted)and V˙O2peak(real)(nonparametric Wilcoxon test). In the CG, there was a significant difference of 116.26 mL/min between the predicted values by the formula and the real values obtained in the unloaded condition. A significant difference in peak effort was found, where V˙O2peak(real)was 40% lower than V˙O2peak(predicted)(nonparametric Wilcoxon test). There was no agreement between the real and predicted measurements as analyzed by Lin's coefficient or the Bland and Altman model. The Wasserman formula does not appear to be appropriate for prediction of functional capacity of volunteers. Therefore, this formula cannot precisely predict the increase in power in incremental CPET on a cycle ergometer.

Long maximal incremental tests accurately assess aerobic fitness in class II and III obese men

This study aimed to compare two different maximal incremental tests with different time durations [a maximal incremental ramp test with a short time duration (8-12 min) (S_Test) and a maximal incremental test with a longer time duration (20-25 min) (L_Test)] to investigate whether an L_Test accurately assesses aerobic fitness in class II and III obese men. Twenty obese men (BMI≥35 kg.m-2) without secondary pathologies (mean±SE; 36.7±1.9 yr; 41.8±0.7 kg*m^-2) completed an S_Test (warm-up: 40 W; increment: 20 W*min-1) and an L_Test [warm-up: 20% of the peak power output (PPO) reached during the S_Test; increment: 10% PPO every 5 min until 70% PPO was reached or until the respiratory exchange ratio reached 1.0, followed by 15 W.min^-1 until exhaustion] on a cycle-ergometer to assess the peak oxygen uptake V˙O2peak and peak heart rate (HR_peak) of each test. There were no significant differences in V˙O2peak (S_Test: 3.1±0.1 L*min^-1; L_Test: 3.0±0.1 L*min^-1) and HR_peak (S_Test: 174±4 bpm; L_Test: 173±4 bpm) between the two tests. Bland-Altman plot analyses showed good agreement and Pearson product-moment and intra-class correlation coefficients showed a strong correlation between V˙O2peak (r=0.81 for both; p≤0.001) and HR_peak (r=0.95 for both; p≤0.001) during both tests. V˙O2peak and HR_peak assessments were not compromised by test duration in class II and III obese men. Therefore, we suggest that the L_Test is a feasible test that accurately assesses aerobic fitness and may allow for the exercise intensity prescription and individualization that will lead to improved therapeutic approaches in treating obesity and severe obesity.

Aerobic fitness levels and validation of a non exercise VO2max prediction equation for HIV-infected patients on HAART

BACKGROUND

Non-exercise (N-EX) questionnaires have been developed to determine maximal oxygen consumption (VO2max) in healthy populations. There are limited reliable and validated N-EX questionnaires for the HIV+ population that provide estimates of habitual physical activity and not VO2max.

OBJECTIVES

To determine how well regression equations developed previously on healthy populations, including N-EX prediction equations for VO2max and age-predicted maximal heart rates (APMHR), worked on an HIV+ population; and to develop a specific N-EX prediction equation for VO2max and APMHR for HIV+ individuals.

METHODS

Sixty-six HIV+ participants on stable HAART completed 4 N-EX questionnaires and performed a maximal graded exercise test.

RESULTS

Sixty males and 6 females were included; mean (SD) age was 49.2 (8.2) years; CD4 count was 516.0 ± 253.0 cells·mm-3; and 92% had undetectable HIV PCR. Mean VO2max was 29.2 ± 7.6 (range, 14.4-49.4) mL·kg-1·min-1 Despite positive correlations with VO2max, previously published N-EX VO2max equations produced results significantly different than actual VO2 scores (P < .0001). An HIV+ specific N-EX equation was developed and produced similar mean VO2max values, R = 0.71, when compared to achieved VO2max (P = .53).

CONCLUSION

HIV+ individuals tend to be sedentary and unfit, putting them at increased risk for the development of chronic diseases associated with a sedentary lifestyle. Based on the level of error associated with utilizing APMHR and N-EX VO2max equations with HIV+ individuals, neither should be used in this population for exercise prescription.

Use of the HR index to predict maximal oxygen uptake during different exercise protocols

This study examined the ability of the HR_index model to accurately predict maximal oxygen uptake (O_2max) across a variety of incremental exercise protocols. Ten men completed five incremental protocols to volitional exhaustion. Protocols included three treadmill (Bruce, UCLA running, Wellness Fitness Initiative [WFI]), one cycle, and one field (shuttle) test. The HR_index prediction equation (METs = 6 × HR_index − 5, where HR_index = HR_max/HR_rest) was used to generate estimates of energy expenditure, which were converted to body mass-specific estimates of O_2max. Estimated O_2max was compared with measured O_2max. Across all protocols, the HR_index model significantly underestimated O_2max by 5.1 mL·kg⁻¹·min⁻¹ (95% CI: −7.4, −2.7) and the standard error of the estimate (SEE) was 6.7 mL·kg⁻¹·min⁻¹. Accuracy of the model was protocol-dependent, with O_2max significantly underestimated for the Bruce and WFI protocols but not the UCLA, Cycle, or Shuttle protocols. Although no significant differences in O_2max estimates were identified for these three protocols, predictive accuracy among them was not high, with root mean squared errors and SEEs ranging from 7.6 to 10.3 mL·kg⁻¹·min⁻¹ and from 4.5 to 8.0 mL·kg⁻¹·min⁻¹, respectively. Correlations between measured and predicted O_2max were between 0.27 and 0.53. Individual prediction errors indicated that prediction accuracy varied considerably within protocols and among participants. In conclusion, across various protocols the HR_index model significantly underestimated O_2max in a group of aerobically fit young men. Estimates generated using the model did not differ from measured O_2max for three of the five protocols studied; nevertheless, some individual prediction errors were large. The lack of precision among estimates may limit the utility of the HR_index model; however, further investigation to establish the model's predictive accuracy is warranted.

Estimated V(O2)max from the rockport walk test on a nonmotorized curved treadmill

The Rockport Walk Test (RWT) is a 1-mile walk used to estimate the maximal volume of oxygen uptake (V(O2)max). The purpose of this study was to validate the RWT on a nonmotorized curved treadmill (CT). Twenty-three healthy adults (10 females; 19-44 years old) participated. One trial of the RWT was performed on a measured indoor track (RWTO) and another on the CT (RWTC) on different days in randomized order. Heart rate (HR) and completion time were used to calculate V(O2)max using 6 different general and gender specific equations from previous research. Subjects also performed a treadmill graded exercise test (GXT), which was used as the criterion measure for V(O2)max. Completion times and HR between the 2 RWT were compared using dependent t-tests. Estimated V(O2)max values were compared between the RWTC, RWTO, and GXT through repeated measures analysis of variance, Pearson's correlations (r), and Bland-Altman's plots. There was no difference between completion times for the RWTO and RWTC but HRs were significantly higher with RWTC. When the same equation was applied to the RWTO and RWTC, there were no similar results. All V(O2)max estimations were different from observed V(O2)max except for the estimation from the relative general Kline et al. equation on the RWTO. Despite high correlations (r = 0.75-0.91), the RWTC underestimated V(O2)max. The RWTC underestimates V(O2)max but may be beneficial if a new equation were created specifically for the CT. With appropriate equations for the CT, the RWTC would provide an alternate form of V(O2)max testing.

The impact of firefighter personal protective equipment and treadmill protocol on maximal oxygen uptake

This study investigated the effects of firefighter personal protective equipment (PPE) on the determination of maximal oxygen uptake (VO(2max)) while using two different treadmill protocols: a progressive incline protocol (PIP) and a progressive speed protocol (PSP), with three clothing conditions (Light-light clothing; Boots-PPE with rubber boots; Shoes-PPE with running shoes). Bruce protocol with Light was performed for a reference test. Results showed there was no difference in VO(2max) between Bruce Light, PIP Light, and PSP Light. However, VO(2max) was reduced in Boots and Shoes with shortened maximal performance time (7 and 6 min reduced for PIP Boots and Shoes, respectively; 11 and 9 min reduced for PSP Boots and Shoes, respectively), whereas the increasing rate of VO(2) in Boots and Shoes during submaximal exercise was greater compared with Light. Wearing firefighter boots compared with wearing running shoes also significantly affected submaximal VO(2) but not VO(2max). These results suggest that firefighters' maximal performance determined from a typical VO(2max) test without wearing PPE may overestimate the actual performance capability of firefighters wearing PPE.

Effect of fasting versus feeding on the bone metabolic response to running

Individuals often perform exercise in the fasted state, but the effects on bone metabolism are not currently known. We compared the effect of an overnight fast with feeding a mixed meal on the bone metabolic response to treadmill running. Ten, physically-active males aged 28 ± 4y (mean ±SD) completed two, counterbalanced, 8d trials. After 3d on a standardised diet, participants performed 60 min of treadmill running at 65% VO(2max) on Day 4 following an overnight fast (FAST) or a standardised breakfast (FED). Blood samples were collected at baseline, before and during exercise, for 3h after exercise, and on four consecutive follow-up days (FU1-FU4). Plasma/serum were analysed for the c-terminal telopeptide region of collagen type 1 (β-CTX), n-terminal propeptides of procollagen type 1 (P1NP), osteocalcin (OC), bone alkaline phosphatase (bone ALP), parathyroid hormone (PTH), albumin-adjusted calcium, phosphate, osteoprotegerin (OPG), cortisol, leptin and ghrelin. Only the β-CTX response was significantly affected by feeding. Pre-exercise concentrations decreased more in FED compared with FAST (47% vs 26%, P<0.001) but increased during exercise in both groups and were not significantly different from baseline at 1h post-exercise. At 3h post-exercise, concentrations were decreased (33%, P<0.001) from baseline in FAST and significantly lower (P<0.001) than in FED. P1NP and PTH increased, and OC decreased during exercise. Bone markers were not significantly different from baseline on FU1-FU4. Fasting had only a minor effect on the bone metabolic response to subsequent acute, endurance exercise, reducing the duration of the increase in β-CTX during early recovery, but having no effect on changes in bone formation markers. The reduced duration of the β-CTX response with fasting was not fully explained by changes in PTH, OPG, leptin or ghrelin.

Determination of maximal oxygen uptake using the bruce or a novel athlete-led protocol in a mixed population

Treadmill tests for maximal oxygen uptake (V̇O_2max) have traditionally used set speed and incline increments regardless of participants training or exercise background. The aim of this study was to determine the validity of a novel athlete-led protocol for determining maximal aerobic fitness in adults. Twenty-nine participants (21 male, 8 female, age 29.8 ± 9.5 y, BMI 24.4 ± 3.1, mean ± SD) from a variety of exercise backgrounds were asked to complete two maximal treadmill running tests (using the standard Bruce or a novel athlete-led protocol [ALP]) to volitional failure in a counter-balanced randomised cross-over trial one week apart. We found no substantial difference in maximal oxygen uptake (47.0 ± 9.1 and 46.8 ± 10.7 ml·kg⁻¹·min⁻¹, mean ± SD for the ALP and Bruce protocols respectively), evidenced by the Spearman correlation coefficient of 0.93 (90% confidence limits, 0.88-0.96). However, compared to the Bruce protocol, participants completing the ALP protocol attained a substantially higher maximal heart rate (ALP = 182.8 ± 10.5, Bruce = 179.7 ± 8.7 beats·min⁻¹). Additionally, using the Bruce protocol took a longer period of time (23.2 ± 17.0 s) compared to the ALP protocol. It seems that using either treadmill protocol will give you similar maximal oxygen uptake results. We suggest the ALP protocol which is simpler, quicker and probably better at achieving maximal heart rates is a useful alternative to the traditional Bruce protocol.

Effect of exercise intensity on the cytokine response to an acute bout of running

PURPOSE

We compared the effects of exercise intensity (EI) on the cytokine response to an acute bout of running.

METHODS

Ten males (mean ± SD VO(2max)= 56.2 ± 8.1 mL·min(-1)·kg(-1)) completed three, counterbalanced, 8-d trials. After three control days, on day 4, participants completed 60 min of running at 55%, 65%, and 75% VO(2max). The cytokines tumor necrosis factor (TNF)-α, interleukin-1β (IL-1β), IL-6, and IL-1 receptor antagonist (ra), and creatine kinase were measured during and for 3 h after exercise and on four follow-up days (FU1-FU4).

RESULTS

RER was higher at 75% V(O2max) compared with both 55% (P < 0.001) and 65% (P < 0.01) VO(2max). IL-1β was undetectable in six participants. There was a small (18%-27%) increase in TNF-α during exercise but no effect of EI. IL-6 concentrations peaked at the end of exercise, with a greater increase at 75% VO(2max), resulting in higher concentrations at the end of exercise and at 30 min after exercise compared with 55% (P < 0.001) and 65% VO(2max) (P < 0.01). IL-1ra concentrations peaked at the end of exercise at 75% VO(2max), resulting in higher (P < 0.05) concentrations at 1-2 h after exercise compared with 55% and 65% VO(2max). Creatine kinase was increased at FU1 and FU2, but there was no effect of EI.

CONCLUSIONS

Sixty minutes of treadmill running at 75% VO(2max) results in a greater increase in IL-6 but not TNF-α compared with 55% and 65% V(O2max). The higher IL-1ra concentrations at 75% VO(2max) might be related to the higher IL-6 concentrations that precede them.

The role of exercise intensity in the bone metabolic response to an acute bout of weight-bearing exercise

We compared the effects of exercise intensity (EI) on bone metabolism during and for 4 days after acute, weight-bearing endurance exercise. Ten males [mean ± SD maximum oxygen uptake (Vo(2max)): 56.2 ± 8.1 ml·min(-1)·kg(-1)] completed three counterbalanced 8-day trials. Following three control days, on day 4, subjects completed 60 min of running at 55%, 65%, and 75% Vo(2max). Markers of bone resorption [COOH-terminal telopeptide region of collagen type 1 (β-CTX)] and formation [NH(2)-terminal propeptides of procollagen type 1 (P1NP), osteocalcin (OC), bone-alkaline phosphatase (ALP)], osteoprotegerin (OPG), parathyroid hormone (PTH), albumin-adjusted calcium (ACa), phosphate (PO(4)), and cortisol were measured during and for 3 h after exercise and on four follow-up days (FU1-FU4). At 75% Vo(2max), β-CTX was not significantly increased from baseline by exercise but was higher compared with 55% (17-19%, P < 0.01) and 65% (11-13%, P < 0.05) Vo(2max) in the first hour postexercise. Concentrations were decreased from baseline in all three groups by 39-42% (P < 0.001) at 3 h postexercise but not thereafter. P1NP increased (P < 0.001) during exercise only, while bone-ALP was increased (P < 0.01) at FU3 and FU4, but neither were affected by EI. PTH and cortisol increased (P < 0.001) with exercise at 75% Vo(2max) only and were higher (P < 0.05) than at 55% and 65% Vo(2max) during and immediately after exercise. The increases (P < 0.001) in OPG, ACa, and PO(4) with exercise were not affected by EI. Increasing EI from 55% to 75% Vo(2max) during 60 min of running resulted in higher β-CTX concentrations in the first hour postexercise but had no effect on bone formation markers. Increased bone-ALP concentrations at 3 and 4 days postexercise suggest a beneficial effect of this type of exercise on bone mineralization. The increase in OPG was not influenced by exercise intensity, whereas PTH was increased at 75% Vo(2max) only, which cannot be fully explained by changes in serum calcium or PO(4) concentrations.

Automatic detection of maximal oxygen uptake and ventilatory threshold

Maximal oxygen uptake (VO(2max)) and ventilatory threshold (VT) are the most common measurements in exercise physiology laboratories for the objective characterization of the physiologic state of metabolic and respiratory systems. Several techniques for their identification were proposed in the literature: the aim of the present study was to review them and assess their performance when applied to experimental data. In the present study, the criteria to detect VO(2max) and VT from respiratory gas-exchange data were analysed and automatic procedures for the identification of these parameters were implemented. These procedures were then applied to experimental data in order to assess the verifiability, repeatability and sensitivity to measurement noise of each proposed method. The results suggest plateau- and RISE-105- as the most reliable automatic procedures for determining VO(2max), while respiratory exchange ratio-, ventilatory equivalent for O(2)- and P(ET,O2)-criteria appear to be the most reliable automatic procedures for estimating VT.

Recommendations for improved data processing from expired gas analysis indirect calorimetry

There is currently no universally recommended and accepted method of data processing within the science of indirect calorimetry for either mixing chamber or breath-by-breath systems of expired gas analysis. Exercise physiologists were first surveyed to determine methods used to process oxygen consumption ((.)VO2) data, and current attitudes to data processing within the science of indirect calorimetry. Breath-by-breath datasets obtained from indirect calorimetry during incremental exercise were then used to demonstrate the consequences of commonly used time, breath and digital filter post-acquisition data processing strategies. Assessment of the variability in breath-by-breath data was determined using multiple regression based on the independent variables ventilation (VE), and the expired gas fractions for oxygen and carbon dioxide, FEO2 and FECO2, respectively. Based on the results of explanation of variance of the breath-by-breath (.)VO2 data, methods of processing to remove variability were proposed for time-averaged, breath-averaged and digital filter applications. Among exercise physiologists, the strategy used to remove the variability in (.)VO2 measurements varied widely, and consisted of time averages (30 sec [38%], 60 sec [18%], 20 sec [11%], 15 sec [8%]), a moving average of five to 11 breaths (10%), and the middle five of seven breaths (7%). Most respondents indicated that they used multiple criteria to establish maximum ((.)VO2 ((.)VO2max) including: the attainment of age-predicted maximum heart rate (HR(max)) [53%], respiratory exchange ratio (RER) >1.10 (49%) or RER >1.15 (27%) and a rating of perceived exertion (RPE) of >17, 18 or 19 (20%). The reasons stated for these strategies included their own beliefs (32%), what they were taught (26%), what they read in research articles (22%), tradition (13%) and the influence of their colleagues (7%). The combination of VE, FEO2 and FECO2 removed 96-98% of (.)VO2 breath-by-breath variability in incremental and steady-state exercise (.)VO2 data sets, respectively. Correction of residual error in (.)VO2 datasets to 10% of the raw variability results from application of a 30-second time average, 15-breath running average, or a 0.04 Hz low cut-off digital filter. Thus, we recommend that once these data processing strategies are used, the peak or maximal value becomes the highest processed datapoint. Exercise physiologists need to agree on, and continually refine through empirical research, a consistent process for analysing data from indirect calorimetry.

Evaluation of true maximal oxygen uptake based on a novel set of standardized criteria

In this study, criteria are used to identify whether a subject has elicited maximal oxygen uptake. We evaluated the validity of traditional maximal oxygen uptake criteria and propose a novel set of criteria. Twenty athletes completed a maximal oxygen uptake test, consisting of an incremental phase and a subsequent supramaximal phase to exhaustion (verification phase). Traditional and novel maximal oxygen uptake criteria were evaluated. Novel criteria were: oxygen uptake plateau defined as the difference between modelled and actual maximal oxygen uptake >50% of the regression slope of the individual oxygen uptake–workrate relationship; as in the first criterion, but for maximal verification oxygen uptake; and a difference of ≤4 beats·min–1 between maximal heart rate values in the 2 phases. Satisfying the traditional oxygen uptake plateau criterion was largely an artefact of the between-subject variation in the oxygen uptake–workrate relationship. Secondary criteria, supposedly an indicator of maximal effort, were often satisfied long before volitional exhaustion, even at intensities as low as 61% maximal oxygen uptake. No significant mean differences were observed between the incremental and verification phases for oxygen uptake (t = 0.4; p = 0.7) or heart rate (t = 0.8; p = 0.5). The novel oxygen uptake plateau criterion, maximal oxygen uptake verification criterion, and maximal heart rate verification criterion were satisfied by 17, 18, and 18 subjects, respectively. The small individual absolute differences in oxygen uptake between incremental and verification phases observed in most subjects provided additional confidence that maximal oxygen uptake was elicited. Current maximal oxygen uptake criteria were not valid and novel criteria should be further explored.

Comparação entre as modalidades de caminhada e corrida na predição do consumo máximo de oxigênio

Os testes ergométricos de exercício realizados em esteira podem ser desempenhados a partir das modalidades de caminhada e corrida, contudo, sem haver grandes elucidações ao comparar resultados de VO2máx obtidos nessas possibilidades de teste. Com o intuito de responder a essa questão, o presente estudo objetivou comparar a predição do VO2máx entre um protocolo escalonado máximo de caminhada e um de corrida, ambos elaborados de modo a proporcionar demandas metabólicas idênticas em cada estágio. Foram voluntários para o presente estudo 23 indivíduos (15 masculinos e oito femininos) com 27,7 ± 7,6 anos de idade, 73,0 ± 14,9kg de massa corporal, 170,0 ± 1,0cm de estatura, 19,3 ± 8,6% de gordura corporal, 24,7 ± 3,3kg×m-2 de índice de massa corporal e 44,1 ± 6,0mL×kg-1×min-1 de potência aeróbia máxima. Um teste t pareado não demonstrou diferenças significativas (p = 0,364; IC 95 % = -2,2 a 0,85) entre o protocolo de caminhada e o de corrida, apesar de a média dos valores do VO2máx na corrida ter sido 2,4% superior (42,4 vs. 43,4mL×kg-1×min-1). Com base nos resultados encontrados, conclui-se que a administração de diferentes estratégias de protocolos em esteira (caminhada ou corrida) não influenciou significativamente a estimativa do VO2max, não interferindo na posterior tomada de decisão para a prescrição do treinamento cardiorrespiratório.

Effect of stage duration on physiological variables commonly used to determine maximum aerobic performance during cycle ergometry

In this study, we examined the effect of stage duration on physiological variables commonly used to determine maximum aerobic performance during cycle ergometry. Ten recreationally trained males (mean age 27.8 +/- 7.1 years; BMI 24.3 +/- 2.5 kg x m(-2); VO2max 52.5 +/- 5.9 ml x kg(-1) x min(-1)) performed three different stage duration protocols on two separate occasions. Each short stage (SS; 1-min stages), long stage (LS; 3-min stages), and constant load + short stage (CL + SS; 4-min constant load followed by 1-min stages) protocol started at 50 W with increments of 30 W. The physiological variables measured included: time to maximum, maximum workload, maximum oxygen consumption (VO2max), maximum heart rate, maximum rating of perceived exertion, maximum blood lactate concentration, and maximum respiratory exchange ratio. The ventilatory threshold was calculated for every trial of the three protocols. There was no difference in VO2max, but maximum heart rate was higher in the LS protocol (P<0.05). Maximum respiratory exchange ratio varied between the protocols (P<0.05), while maximum workload differed between the SS and LS protocols, and the LS and CL + SS protocols (P<0.0001). The physiological variables were comparable between trials for the SS and CL + SS protocols, but maximum workload and VO2max differed for the LS protocol (P<0.05). Workload at the ventilatory threshold was lower for the LS protocol (P<0.05). Heart rate at the ventilatory threshold was different between the LS and CL + SS protocols (P<0.05). Performing a test involving 1- or 3-min stage durations on a single occasion was appropriate for the determination of VO2max and the ventilatory threshold. However, the disparity in heart rate and workload could result in differences in mechanical and physiological work being undertaken. Consistent use of a protocol may alleviate errors during exercise prescription.

V˙O2max, Protocol Duration, and the V˙O2 Plateau

PURPOSE

The purpose of this study was to compare VO2max, VO2-time slopes at the end of the protocol (last 30 s), and the presence of a VO2 plateau (VO2-time slope < 0.05 L.min(-1) during the last 30 s) across four protocol durations (5, 8, 12, and 16 min) during incremental cycling exercise to VO2max.

METHODS

Eight male (23.8 +/- 3.2 yr) and eight female (26.0 +/- 8.9 yr) subjects of moderate to high fitness levels participated in the study.

RESULTS

VO2max was significantly higher in men than in women for each protocol duration, with main effect means of 4.23 versus 2.84 L.min(-1), respectively. For women, VO2max did not differ between any protocol duration. For men, VO2max for the 8-min protocol (4.44 +/- 0.39 L.min(-1)) was significantly higher than for all other protocol durations. Analysis of covariance, using the highest VO2max as the covariate, removed all protocol-duration significance for men. The VO2 slope for the final 30 s of each test was significantly lower for the 16-min protocol compared with the 5-min protocol, for both men and women. The ventilation threshold across four protocols was similar, at approximately 76% of VO2max for both men and women.

CONCLUSIONS

The protocol duration of tests to VO2max should be between 8 and 10 min for healthy, moderately to highly trained subjects.

Incremental Exercise Test Design and Analysis

Physiological variables, such as maximum work rate or maximal oxygen uptake (VO2max), together with other submaximal metabolic inflection points (e.g. the lactate threshold [LT], the onset of blood lactate accumulation and the pulmonary ventilation threshold [VT]), are regularly quantified by sports scientists during an incremental exercise test to exhaustion. These variables have been shown to correlate with endurance performance, have been used to prescribe exercise training loads and are useful to monitor adaptation to training. However, an incremental exercise test can be modified in terms of starting and subsequent work rates, increments and duration of each stage. At the same time, the analysis of the blood lactate/ventilatory response to incremental exercise may vary due to the medium of blood analysed and the treatment (or mathematical modelling) of data following the test to model the metabolic inflection points. Modification of the stage duration during an incremental exercise test may influence the submaximal and maximal physiological variables. In particular, the peak power output is reduced in incremental exercise tests that have stages of longer duration. Furthermore, the VT or LT may also occur at higher absolute exercise work rate in incremental tests comprising shorter stages. These effects may influence the relationship of the variables to endurance performance or potentially influence the sensitivity of these results to endurance training. A difference in maximum work rate with modification of incremental exercise test design may change the validity of using these results for predicting performance, and prescribing or monitoring training. Sports scientists and coaches should consider these factors when conducting incremental exercise testing for the purposes of performance diagnostics.

Verification phase as a useful tool in the determination of the maximal oxygen uptake of distance runners

This study investigated the utility of a verification phase for increasing confidence that a “true” maximal oxygen uptake had been elicited in 16 male distance runners (mean age (±SD), 38.7  (± 7.5 y)) during an incremental treadmill running test continued to volitional exhaustion. After the incremental test subjects performed a 10 min recovery walk and a verification phase performed to volitional exhaustion at a running speed 0.5 km·h–1 higher than that attained during the last completed stage of the incremental phase. Verification criteria were a verification phase peak oxygen uptake ≤ 2% higher than the incremental phase value and peak heart rate values within 2 beats·min–1 of each other. Of the 32 tests, 26 satisfied the oxygen uptake verification criterion and 23 satisfied the heart rate verification criterion. Peak heart rate was lower (p = 0.001) during the verification phase than during the incremental phase, suggesting that the verification protocol was inadequate in eliciting maximal values in some runners. This was further supported by the fact that 7 tests exhibited peak oxygen uptake values over 100 mL·min–1 (≥ 3%) lower than the peak values attained in the incremental phase. Further research is required to improve the verification procedure before its utility can be confirmed.

Limitations to systemic and locomotor limb muscle oxygen delivery and uptake during maximal exercise in humans

Reductions in systemic and locomotor limb muscle blood flow and O2 delivery limit aerobic capacity in humans. To examine whether O2 delivery limits both aerobic power and capacity, we first measured systemic haemodynamics, O2 transport and O2 uptake during incremental and constant (372 +/- 11 W; 85% of peak power; mean +/- S.E.M.) cycling exercise to exhaustion (n = 8) and then measured systemic and leg haemodynamics and during incremental cycling and knee-extensor exercise in male subjects (n = 10). During incremental cycling, cardiac output and systemic O2 delivery increased linearly to 80% of peak power (r2 = 0.998, P < 0.001) and then plateaued in parallel to a decline in stroke volume (SV) and an increase in central venous and mean arterial pressures (P < 0.05). In contrast, heart rate and increased linearly until exhaustion (r2 = 0.993; P < 0.001) accompanying a rise in systemic O2 extraction to 84 +/- 2%. In the exercising legs, blood flow and O2 delivery levelled off at 73-88% of peak power, blunting leg per unit of work despite increasing O2 extraction. When blood flow increased linearly during one-legged knee-extensor exercise, per unit of work was unaltered on fatigue. During constant cycling, , SV, systemic O2 delivery and reached maximal values within approximately 5 min, but dropped before exhaustion (P < 0.05) despite increasing or stable central venous and mean arterial pressures. In both types of maximal cycling, the impaired systemic O2 delivery was due to the decline or plateau in because arterial O2 content continued to increase. These results indicate that an inability of the circulatory system to sustain a linear increase in O2 delivery to the locomotor muscles restrains aerobic power. The similar impairment in SV and O2 delivery during incremental and constant load cycling provides evidence for a central limitation to aerobic power and capacity in humans.

Maximal Aerobic Capacity Testing of Older Adults: A Critical Review

Most of the data that describe maximal oxygen uptake (VO(2max)) and the requirements for its attainment have been developed using young adults as subjects. Many older adults are unable to satisfactorily complete a maximal exercise effort in a standard exercise stress test. This review describes exercise tests currently available to measure VO(2max) in older adults. PubMed and CINAHL databases were searched for studies including healthy individuals older than 65 years with reproducible descriptions of the testing protocol. The research on VO(2max) testing in healthy individuals older than 65 years is limited, does not describe the protocols in detail, and/or lacks information on the psychometric properties of the exercise tests. There is a need for refinement of the few existing protocols for testing aerobic capacity in older adults, as well as the development of new protocols specifically applicable to older adults. Consensus on the criteria defining VO(2max) attainment during exercise in older adults is required, as well as agreement on the most appropriate exercise protocols and equipment, specific to older adults, to successfully fulfil these criteria.

Comparison of Wpeak, VO2peak and the ventilation threshold from two different incremental exercise tests: Relationship to endurance performance

This report presents data comparing the peak rate of oxygen consumption (VO2(peak)), peak power output (W(peak)) and the ventilation threshold (VT) obtained from two different incremental cycle exercise tests performed by nine well trained triathletes (Mean +/- SD age 32 +/- 3 yrs; body mass 77.4 +/- 4.9 kg and height 185 +/- 3 cm). Furthermore, the relationship between these variables and the average sustained power output (W) during a 90 min cycle time trial (TT) was also determined. The two incremental exercise tests involved a 'short' test, which commenced at 150 W with 30 W increments every 60 s until exhaustion. The second ('long') incremental test commenced at a power output representing 50% of the W(peak) obtained in the short test. The subjects were then required to increase the power output by 5% every 3 min until exhaustion. The results showed the W(peak) (W) in the short test was significantly (p < 0.01) higher than in the long test. However, there was no significant difference in the VO2(peak) (1 x min(-1)) between the two tests. There was a weak but significant correlation between W(peak) (W) and VO2(peak) (l x min(-1)) (r = 0.72: p < 0.05) in the short (60 s stage) test but not the long (3 min stage) test (r = 0.52). There were no significant differences and good agreement between for the heart rate (HR) (b x min(-1)) and oxygen consumption (VO2) corresponding to the VT. In contrast, the power output (W) corresponding to the VT was significantly different and not comparable between the long and short incremental tests. The cycle TT performance was most correlated to the W(peak) (W) (r = 0.94; p < 0.01) and the VT (W) (r = 0.75; p < 0.05) from the long test as well as the VO2(peak) (l x min(-1)) obtained from the short incremental test (r = 0.75; p < 0.01). These data suggest that the length of stages during incremental cycle exercise may influence the W(peak) and in turn the relationship of this variable to VO2(peak). Furthermore, the W(peak) obtained from a test incorporating 3 min stage increments represents the best indicator of 90 min cycle performance in well-trained triathletes.

The maximally attainable VO2 during exercise in humans: the peak vs. maximum issue

The quantification of maximum oxygen uptake (V(O2 max)), a parameter characterizing the effective integration of the neural, cardiopulmonary, and metabolic systems, requires oxygen uptake (VO2) to attain a plateau. We were interested in whether a VO2 plateau was consistently manifest during maximal incremental ramp cycle ergometry and also in ascertaining the relationship between this peak VO2 (V(O2 peak)) and that determined from one, or several, maximal constant-load tests. Ventilatory and pulmonary gas-exchange variables were measured breath by breath with a turbine and mass spectrometer. On average, V(O2 peak) [3.51 +/- 0.8 (SD) l/min] for the ramp test did not differ from that extrapolated from the linear phase of the response in 71 subjects. In 12 of these subjects, the V(O2 peak) was less than the extrapolated value by 0.1-0.4 l/min (i.e., a "plateau"), and in 19 subjects, V(O2 peak) was higher by 0.05-0.4 l/min. In the remaining 40 subjects, we could not discriminate a difference. The V(O2 peak) from the incremental test also did not differ from that of a single maximum constant-load test in 38 subjects or from the V(O2 max) in 6 subjects who undertook a range of progressively greater discontinuous constant-load tests. A plateau in the actual VO2 response is therefore not an obligatory consequence of incremental exercise. Because the peak value attained was not different from the plateau in the plot of VO2 vs. work rate (for the constant-load tests), the V(O2 peak) attained on a maximum-effort incremental test is likely to be a valid index of V(O2 max), despite no evidence of a plateau in the data themselves. However, without additional tests, one cannot be certain.

Prolonged incremental tests do not necessarily compromise VO2max in well-trained athletes

Existing literature suggests that tests for maximal oxygen uptake (VO2max) should last 8-12 minutes and that prolonged tests do not produce valid measurements. The research underlying this suggestion has been performed with non-athletic populations and trained athletes may be more tolerant of longer protocols. Eleven rowers (8 males, 3 females) each underwent four different incremental tests on a standard rowing ergometer in randomised counterbalanced order. One of the tests was continuous with workload increments each minute (IT1MIN). This test lasted an average of 12 min+/-4 s (SEM). The other three tests were discontinuous and consisted of 7 stages separated by 1-minute recovery intervals. Stage durations of 3, 4 and 5 min were used in the different tests (IT3MIN, IT4MIN and IT5MIN). Mean values for VO2max were almost identical for IT1MIN (4.56+/-0.22 L x min(-1)), IT3MIN (4.60+/-0.23 L x min(-1)) and IT4MIN (4.60+/-0.21 L x min(-1)), while IT5MIN produced a significantly lower value (4.47+/-0.21 L x min(-1), p<0.05). There was no significant difference between protocols in peak post-exercise blood lactate concentration (approx 13 mmol x L(-1) in each case), but IT1MIN produced lower peak heart rates and higher respiratory exchange ratios. We conclude that with well trained rowing athletes discontinuous test protocols involving 7 stages of 3-4 minutes duration can provide valid measurements of VO2max.

Discontinuous incremental threshold loading test: measure of respiratory muscle endurance in patients with COPD

STUDY OBJECTIVE

To assess the discontinuous incremental threshold loading (DC-ITL) test as a measure of respiratory muscle endurance for patients with COPD in terms of perceived breathing difficulty, reliability, and validity.

DESIGN

The DC-ITL test was repeated three times at weekly intervals under identical test conditions.

SETTING

Clinical research laboratory.

PATIENTS

Forty-eight patients with moderate to severe COPD.

MEASUREMENTS AND RESULTS

Rating of perceived breathing difficulty (RPBD) was measured at the end of each stage of the DC-ITL test with a Borg category-ratio scale. The maximal inspiratory pressure (PImax) was measured before and after the DC-ITL test. Breathing patterns were measured during the DC-ITL test. The mean (+/-SD) for RPBD at the maximal load was 6.3 (3.1), 6.6 (2.8), and 6.7 (2.7) for visits one, two, and three, respectively (not significant). The mean relative maximal load for the DC-ITL test (peak mouth pressure as a percent of PImax) at the last completed stage was 59+/-23%, 62+/-20%, and 63+/-19% for visits one, two, and three, respectively (not significant). Test-retest reliability was r1,2=0.82 and r2,3=0.69 for relative maximal load and r1,2=0.90 and r2,3=0.90 for absolute maximal load (peak mouth pressure). Tidal volume decreased (p < 0.01) and respiratory rate increased (p < 0.01) from the next-to-the-last to the last completed stage. PImax decreased after the DC-ITL test (p < 0.01).

CONCLUSIONS

Moderate breathing difficulty was experienced during the DC-ITL test. The test was reliable and the results of this study support its validity as a measure of respiratory muscle endurance.

Evaluation of a new standardized ramp protocol: the BSU/Bruce Ramp protocol

BACKGROUND

Because of recent technological advances, exercise testing laboratories now have the ability to use ramp protocols with treadmill exercise tests. Since the Bruce protocol is the most widely used treadmill protocol in clinical laboratories, a standardized ramp treadmill protocol was developed that corresponds to the speed and grade settings of the Bruce protocol at each 3-minute time interval. The purpose of this study was to evaluate the utility of using subject demographic and exercise test data to predict peak oxygen uptake (VO2peak) for tests conducted with the BSU/Bruce Ramp protocol.

METHODS

Maximal exercise tests were performed by 698 men and women using the BSU/Bruce Ramp protocol. Peak oxygen uptake was measured during all tests. Stepwise multiple regression analyses were used to predict VO2peak (mL.kg-1.min-1) from maximal treadmill test time and selected variables including age, gender, physical activity habits, and body weight.

RESULTS

Maximal test time was found to be the most potent predictor of VO2peak, accounting for 86% of the variance in peak aerobic power, with a standard error of estimate of 3.4 mL kg min-1. A multiple regression equation including age, gender, physical activity habits, and body weight resulted in a slightly improved prediction (R2 = 0.88; standard error of estimates = 3.1 mL kg min-1).

CONCLUSIONS

Peak oxygen uptake values can be predicted with reasonable accuracy from the BSU/Bruce Ramp protocol. The BSU/Bruce Ramp would be an excellent choice for laboratories desiring to use a ramp treadmill protocol because of the design of the protocol with identical workloads at equivalent time periods (3, 6, 9, 12, 15, 18, 21 minutes) as the commonly used Bruce protocol.

The effect of stage duration on the calculation of peak VO2 during cycle ergometry

This study investigated the influence of stage duration on the calculation of peak oxygen consumption (peak VO2 to determine whether both the lactate threshold (LT) and peak VO2 could be measured during the same test without compromising the peak VO2 value obtained. Eight moderately-active females (mean age +/- SD = 19.6 +/- 2.5 years) performed three peak VO2 tests on an electrically-braked cycle ergometer. Power output was increased every minute for the short peak VO2 test (S) and every three minutes for the long peak VO2 tests (L). Testing took place over two weeks with all tests separated by at least 48 hours. The first peak VO2 test was a long test (L1) and served as familiarisation. The subjects then performed a short (S) and a long (L2) peak VO2 test in random, counterbalanced order. For each subject, all three tests were performed at the same time of day in controlled environmental conditions. There was no significant difference between the two exercise protocols for peak VO2 when expressed in ml x kg(-1) x min(-1) (F[1,7]=3.47, P=0.105) or in L x min(-1) (F[1,7]=3.39. P=0.108). However, the maximum heart rate (HRmax) achieved in S was significantly less than the HRmax achieved in L2 (F[1,7]=33.4, P<0.001). The power output at exhaustion (Wpeak) was significantly greater in S than in L2 (F[1,7]=56.5, P<0.001). The data from this study therefore showed that in moderately-active females, a three-minute incremental protocol, allowing for the simultaneous calculation of the LT, could be used without compromising peak VO2, but that HRmax and Wpeak were affected.

Maximal oxygen uptake: "classical" versus "contemporary" viewpoints

The traditional view of VO2max owes a great deal to the work of A. V. Hill, who conducted experiments on exercising man in Manchester, England, in the 1920's. Hill and colleagues proposed that there is an upper limit to oxygen uptake (VO2max), that there are inter-individual differences in this variable, and that VO2max is limited by the circulatory and/or respiratory systems. They demonstrated that oxygen uptake increases linearly with running speed, but in some subjects it eventually "reaches a maximum beyond which no effort can drive it," a phenomenon now referred to as the VO2 plateau. In recent years, Timothy Noakes has strongly criticized Hill's concept of VO2max. He maintains that the absence of a VO2 plateau in some subjects is proof that oxygen delivery is not a limiting factor for VO2max. This view fails to recognize that the plateau is not the principal evidence for a cardiorespiratory limitation. Noakes rejects the VO2max paradigm of A. V. Hill in its entirety. The alternative paradigm he proposes is that endurance performance is limited by "muscle factors." Noakes suggests that the best distance runners have muscle characteristics that allow them to achieve higher running speeds, and since running speed is linearly related to oxygen uptake, an indirect consequence of this is that they will have higher VO2max values. This is exactly the opposite of how the relationship between VO2max and running speed at the end of a maximal exercise test should be viewed. Noakes offers little evidence to support his views, and they conflict with a vast body of scientific evidence showing that oxygen transport is a major determinant of endurance performance. After carefully reviewing the evidence on both sides of the issue, we conclude that the older "classical" VO2max paradigm of A. V. Hill is the correct one.

Effect of a rhinovirus-caused upper respiratory illness on pulmonary function test and exercise responses

Upper respiratory illness (URI) may cause more frequent acute disability among athletes than all other diseases combined. The purposes of this study were to determine the impact of a rhinovirus-caused URI on resting pulmonary function submaximal exercise responses and on maximal exercise functional capacity. Twenty-four men and 21 women (18-29 yr) of varying fitness levels were assigned to the experimental group (URI), and 10 additional individuals served as a control group (CRL). An initial serological screening was performed on all URI group subjects to exclude those with the rhinovirus 16 (HRV16) antibody. All subjects completed both a baseline pulmonary function test and a graded exercise test to volitional fatigue. URI subjects were inoculated with HRV 16 on two consecutive days within 10 d of completing these tests. The day following the second inoculation (peak of illness), post-inoculation pulmonary function and graded exercise tests were performed. A noninfected control group completed these same pulmonary and exercise tests 1 wk apart. ANOVA identified no significant differences (P < 0.05) at minutes 2, 5, and 8 for the physiological responses measured between the pre- and post-exercise tests for both the URI and CRL, groups. Furthermore, there were no significant differences between maximal exercise performance between running trials for either group. There was also no significant interaction between treatment (pre/post URI) and group for any of the pulmonary function measures obtained. In conclusion, physiological responses to pulmonary function testing and submaximal and maximal exercise do not appear to be altered by an URI.

Gas exchange and neurohumoral response to exercise: influence of the exercise protocol

Maximal oxygen uptake varies with the exercise protocol, but the extent to which hormonal and metabolic responses to exercise are influenced by the exercise protocol has not been precisely defined. Twelve healthy subjects underwent maximal exercise testing using two incremental bicycle tests with individualized, identical work rate increments between 40 and 70 W. One protocol employed a 1-min and the other a 3-min duration per stage. Expiratory gas and venous blood were sampled at regular intervals for metabolic and hormonal analysis. Exercise duration for the 1-min and 3-min protocols was 6.0 +/- 0.1 and 14.3 +/- 0.3 min, respectively (P < 0.001). Significantly higher values were observed for peak VO2 and maximal ventilation during the 3-min protocol compared with the 1-min protocol (41.1 +/- 1.8 vs 38.3 +/- 1.6 ml.kg-1.min-1, P < 0.001; and 104.9 +/- 8.0 vs 97.2 + 5.7 l.min-1, P < 0.05, for peak VO2 and peak ventilation, respectively). However, the maximal workload achieved was higher during the 1-min versus the 3-min protocol (330 + 24 vs 280 + 21 W, P < 0.01). No differences were observed for maximal heart rate or blood pressure, whereas maximal plasma lactate was roughly twice as high during the 3-min compared with the 1-min protocol (7.5 +/- 0.8 vs 3.8 +/- 0.5 mmol.l-1, P < 0.001). Norepinephrine, epinephrine, dopamine, and growth hormone levels were generally higher throughout exercise during the 3-min compared with the 1-min protocol. When expressed as a percentage of peak VO2, however, differences in catecholamine levels were not observed. Endothelin levels did not change. We conclude that the exercise protocol profoundly influences exercise capacity as well as the metabolic and hormonal response to exercise and should be considered when using these variables to evaluate an intervention.