Gas Exchange Kinetics and Work Load During Exercise: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Gas Exchange Kinetics and Work Load During Exercise (NCT03770507), a randomized na study. The primary outcome is Maximum Oxygen Uptake (VO2) Measurements During Exercise.

2. Clinical Question

The registry describes the study’s purpose as understanding how different kinds of exercise affect the body, with attention to heart and lung measures. That purpose is broader than the specific primary endpoint: maximum VO2 is a measured exercise response, while the registry’s description also refers to gas-exchange kinetics and heart rate. The record does not state a directional hypothesis, identify a single prespecified pairwise contrast, or report which age group or protocol is intended to be the principal focus. Consequently, the clinical question can be described as a comparison of exercise responses across modalities and age groups, but not as a test of a specific superiority claim.

3. Trial Design

The registry identifies this as a randomized, single-masked crossover study, with an enrollment of 94. Its status is completed. The study began on 2016-04-26, and its primary completion date is 2016-12-01. The record names the sponsor as University of California, Irvine.

The crossover label indicates a design in which comparisons can be made across exercise conditions within participants, rather than relying solely on separate groups assigned to a single condition. That is a general description of crossover designs; the registry does not report the exercise sequence, randomization procedure, period structure, or how within-participant comparisons were modeled. It also does not say who was masked or how masking was implemented, so the meaning of single masking cannot be specified from the record.

The named groups cover cycle ergometer and treadmill exercise among children, adolescents and adults. These descriptions indicate which age and modality combinations were included, but do not establish that each participant completed every listed condition. The registry describes exercise on a bicycle ergometer or treadmill and says participants exercise in different protocols. Details such as protocol intensity, duration, order, and the definition of completion are not reported in the registry record.

The primary outcome is maximum oxygen uptake (VO2) during exercise, specified as a mean with standard deviation and measured in L/min. The outcome description refers to breath-by-breath gas exchange in response to exercise, with a timeframe listed as “At least 48 hours.” The record also lists heart-rate measurements during exercise as a secondary outcome. It does not report numerical outcome summaries, effect estimates, confidence intervals, or analysis results. The design information therefore supports describing the intended comparison and the kind of measures collected, but not the magnitude or precision of any observed difference.

4. Participant Flow and Accounting

The registry reports how participants moved through each stage of the study. All counts below are exactly as posted; missing counts are not inferred from other stages.

Overall Study

5. Baseline Characteristics

The table reproduces the baseline characteristics posted in the registry, which describe the participants analysed at baseline and help show whether the randomized groups were comparable.

6. Primary Endpoint

The registry lists the primary outcome as Maximum Oxygen Uptake (VO2) Measurements During Exercise, measured over At least 48 hours.

Maximum oxygen uptake (VO2) during exercise is the registry’s primary endpoint. It is specified in L/min and described as a mean with standard deviation. The measurement is based on breath-by-breath gas exchange in response to exercise; the registry’s timeframe is “At least 48 hours.” Numerical VO2 values and summaries by exercise protocol are not reported in the registry record.

In general, oxygen uptake measures the rate at which oxygen is taken up during exercise. A maximum value can describe the highest measured oxygen uptake reached under the exercise conditions used. It is relevant to this study because the stated purpose is to compare physiological responses to different exercise protocols and because the outcome directly concerns gas exchange. The record also names gas-exchange kinetics, which concerns how the response changes during exercise, but does not specify a kinetic parameter as the primary endpoint.

The endpoint should be interpreted in relation to the exercise conditions and participant groups studied. A mean describes the group’s average measurement, while a standard deviation describes the spread of individual measurements around that mean. These are general statistical interpretations, not a report of observed VO2 values in this trial. The registry gives no protocol-specific means, standard deviations, contrast estimates, or confidence intervals, so the size and precision of any difference cannot be assessed from its posted results. Heart rate is listed separately as a secondary outcome, not as part of the primary endpoint.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The registry specifies a continuous primary outcome summarized as a mean with standard deviation. It does not report the statistical analysis results for that outcome. The concepts below explain how such measurements are commonly interpreted; they do not describe an analysis confirmed by this trial’s registry record.

What do a mean and standard deviation describe?

In general, the mean is the arithmetic average of observed measurements in a defined group or condition. The standard deviation describes how dispersed individual measurements are around that average. They answer different questions: the mean locates the center of the observed values, while the standard deviation describes their variability. For this trial, the registry specifies these summary measures for maximum VO2 in L/min, but it does not report the actual means or standard deviations. No comparison can be reconstructed from the outcome specification alone.

How does a crossover design affect comparison?

In general, a crossover design can allow a participant’s measurement under one condition to be compared with that same participant’s measurement under another condition. This pairing can account for stable differences among participants, but the analysis must preserve the within-participant structure. The registry labels this trial crossover and randomized. It does not describe the order of conditions, the randomization procedure, the periods, or the model used. It is therefore not possible to determine from the registry whether, or how, paired observations were incorporated into the analysis.

Exercise responses may also depend on the order or timing of conditions. In general, crossover studies can consider period and sequence effects, and whether responses to an earlier condition could carry over to a later one. The registry does not report an assessment or adjustment for these issues, nor does it describe any washout interval. These are matters of reporting uncertainty, not evidence that a particular effect occurred.

What would a confidence interval contribute?

In general, a confidence interval expresses uncertainty around an estimated quantity under a specified statistical procedure. Its width reflects both the variability of measurements and the amount of information available, along with assumptions of the method. A confidence interval for a difference between protocols would help readers assess which values of the contrast are compatible with the data under that procedure. The registry record does not report an estimate or confidence interval for maximum VO2. Statistical precision and the range of plausible differences therefore cannot be evaluated.

A p-value, when reported, addresses how compatible the data are with a specified null model under the analysis assumptions. It does not measure the size or importance of a difference, and it does not establish that two conditions are equivalent. No p-value or test result is reported for the primary outcome in the registry record. The lack of a reported test should not be interpreted as a null finding.

How should the planning illustration be read?

The record describes planning assumptions using a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation. It also describes planning for a stated fraction of an observed effect. These are assumptions for a planning illustration, not a description of the trial’s original design justification or a report of observed power. The registry does not report the trial’s own sample-size justification, and no analysis estimates are reported to anchor an interpretation of the observed effect. The illustration cannot be treated as evidence that the study had a particular probability of detecting a true effect.

General sample-size planning asks how much information a study might need for a defined effect and statistical procedure. The answer depends on the assumed variability, effect, allocation, and analysis. For a crossover study, the within-participant variability and correlation of measurements can also matter. The registry does not report those quantities or the assumptions behind the original design. No sample-size conclusion about adequacy can be drawn from the enrollment figure alone.

Why does the outcome structure matter?

The registry indicates that the primary outcome includes several categories or time points and is not reduced to one comparison. In general, multiple outcomes, comparisons, or time points create a multiplicity question: the more inferences considered, the more important it is to understand which analyses were planned and how interpretation accounts for that set. The registry does not report a multiplicity strategy, an analysis plan, or results by time point. Without these details, no single contrast can be identified as the definitive statistical test.

Continuous measurements may also have distributions that depart from assumptions used by a model. In general, a method’s assumptions should be considered in relation to the data and the design. The registry does not describe a model, diagnostics, transformations, or sensitivity analyses. It is not possible to assess whether distributional or other modeling assumptions were checked.

These statistical concepts clarify what would be useful for interpreting the study, but they do not fill gaps in its reported results. Numerical summaries, a defined contrast, an analysis method, and uncertainty estimates are not reported in the registry record.

10. Multiplicity, Missing Data and Analysis Populations

The registry lists two outcome measures: maximum VO2 during exercise as the primary outcome and heart-rate measurements during exercise as a secondary outcome. The primary outcome is described as having several categories or time points and is not reduced to one comparison. Numerical results for either outcome are not reported in the registry record.

In general, multiplicity arises when a study makes several statistical comparisons, such as across outcomes, time points, groups, or conditions. A prespecified analysis plan helps clarify which comparisons are primary and how interpretation should account for multiple testing. The registry does not report a statistical analysis plan, a multiplicity adjustment, or a hierarchy among comparisons. It is therefore not possible to determine which contrasts were planned, which were analyzed, or how any multiplicity was handled.

The registry does not report missing-data counts, reasons for missingness, or methods used to address missing measurements. It also does not report whether participants completed all exercise conditions or how incomplete crossover records were handled. In general, missing measurements can affect the analyzed population and the interpretation of comparisons, particularly when availability differs across conditions. No conclusion about the extent or impact of missing data can be made from the record.

Analysis populations are not reported in the registry record. The enrollment of 94 does not establish how many participants were included in each primary or secondary outcome analysis, and the group-specific adverse-event counts should not be read as outcome-analysis denominators. The analysis set, exclusions, and handling of participants with partial measurements are unspecified. Consequently, the scope of the analyzed data cannot be determined.

11. Safety Results

The registry reports serious adverse events as affected participants divided by participants at risk.

Deaths

Other (non-serious) adverse events

Participants with at least one non-serious event at or above the registry's 0% reporting threshold.

The adverse-event record lists six exercise groups: cycle ergometer and treadmill exercise among children, adolescents and adults. For each listed group, the reported count of participants affected by a serious adverse event is zero, and the reported death count is zero. The count for other adverse events is also zero in each group. The at-risk counts differ among groups; these are the group-specific denominators entered for adverse-event reporting, not necessarily the numbers contributing data to the primary outcome.

These figures describe what was entered in the registry’s adverse-event fields. They do not establish that no event occurred outside the reporting period or among participants not represented in those fields. The record does not provide serious adverse-event terms, and no serious adverse-event terms are listed. The figures also do not supply information about event ascertainment, monitoring procedures, or completeness of reporting.

In general, a zero count in a registry entry means that no affected participants are recorded in that category for the listed group; it is not a statistical estimate that risk is absent. With no further safety details reported, the counts should be read narrowly as registry-reported events rather than as a comprehensive assessment of safety.

12. What the Result Does, and Does Not, Mean

The registry record describes a completed randomized crossover study evaluating exercise responses in children, adolescents and adults using cycle ergometer and treadmill protocols. Maximum VO2 during exercise is identified as the primary outcome, and heart rate during exercise is listed as a secondary outcome. These registry entries establish the intended subject of the comparison and the types of measurements considered.

The record does not report numerical outcome results, estimated differences, confidence intervals, or p-values. As a result, it does not show how maximum VO2 or heart rate varied across the named protocols, how large any difference was, or how precisely it was estimated. The absence of reported estimates is not evidence that the exercise conditions had identical responses, and it does not support a claim of a meaningful difference.

The crossover label is relevant to how comparisons might be made, but details of condition order and analysis are not reported. The enrollment of 94 is not, by itself, evidence about the number analyzed or the precision of an outcome estimate. Likewise, the adverse-event counts are limited to registry entries and do not provide a substitute for results on exercise response.

In general, a trial’s conclusions depend on the specific contrast, analysis population, statistical method, and uncertainty around estimated effects. Those elements are not available for the primary outcome in this record. The record therefore supports a description of the research question and design, but not a conclusion about which protocol produced a higher or lower maximum VO2, or whether any difference was statistically distinguishable from chance.

The registry’s broader rationale mentions potential relevance to fitness assessment and personalized exercise programs. Those are stated aims and possible applications, not findings demonstrated by the posted results. No claim about fitness assessment or individual exercise programming can be inferred without reported results and further evidence. The appropriate interpretation is limited to what the record documents: a study designed to compare physiological measurements during different exercise protocols, without analyzable primary-outcome results reported in the registry.

13. Why This Trial Matters Statistically

This study raises a useful statistical question because exercise responses are measured across different protocols and age groups, and the registry identifies the design as crossover. In general, within-participant comparisons can be informative when the same person contributes measurements under multiple conditions. They also require analysis that respects pairing and the structure created by condition order and timing. The registry record does not describe those analytic details, making the study a reminder that a design label alone is not enough to evaluate the comparison.

The outcomes also distinguish a measured exercise response from its interpretation. Maximum VO2 is specified as the primary measure, while heart rate is secondary and gas-exchange kinetics appears in the outcome description. Clear reporting of estimates by condition, their uncertainty, and the exact comparisons would let readers judge the magnitude and precision of the observed responses. Those numerical results are not reported in the registry record.

Multiplicity is another relevant issue because the primary outcome includes several categories or time points and the study spans multiple age and exercise groups. In general, readers need to know which comparisons were planned and how the analysis addressed a family of possible inferences. Such information is not reported. This limits the ability to distinguish a primary finding from exploratory comparisons.

The registry does report zero serious adverse events and zero deaths in each listed group, but these entries are not a substitute for the primary outcome results or for detailed safety reporting. Taken together, the record illustrates why design, outcome definitions, analysis methods, denominators, and uncertainty estimates all matter for interpreting a clinical study. It documents the comparison of interest, but does not provide the quantitative results needed to assess its findings.

14. Limitations

• The posted summary statistics are the only data these results rest on; patient-level data, full protocols and statistical analysis plans are not available.
• Recalculated results are simple, unadjusted calculations from posted summaries. They do not replace the sponsor's prespecified analysis.

The central limitation for interpretation is that numerical primary-outcome results are not reported in the registry record. There are no group or condition summaries, estimated contrasts, confidence intervals, or test results for maximum VO2. Heart-rate results are also not reported. The direction, magnitude and precision of any observed differences therefore remain unknown.

The registry identifies a randomized crossover design but does not describe condition sequence, periods, washout, or the statistical model. It does not report who was masked or how single masking was implemented. These omissions prevent assessment of key design and analysis details, including whether within-participant dependence was incorporated.

The primary outcome is described as having several categories or time points and is not reduced to one comparison. The record does not specify the statistical analysis plan, multiplicity approach, analysis population, or handling of missing measurements. It also does not report protocol intensity, duration, or detailed eligibility criteria. Generalizability to populations beyond those identified as healthy children, adolescents and adults cannot be assessed from the information recorded.

Enrollment is 94, but the number contributing data to each outcome analysis is not reported. The adverse-event denominators do not establish outcome-analysis sample sizes. The registry lists zero affected participants for serious and other adverse events and zero deaths in each group, but does not supply event terms or details about ascertainment and completeness.

Finally, the record does not report the trial’s sample-size justification or numerical analysis results that would allow readers to assess the planning illustration. These limitations concern what is documented in the registry; they do not establish that particular procedures or analyses were not performed outside the record.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: Gas Exchange Kinetics and Work Load During Exercise — NCT03770507.
• Registry record last updated 2026-03-23; status last verified 2025-07.
• Results first posted 2026-03-23.
• Data retrieved from ClinicalTrials.gov on 2026-11-09.
• Group sizes, means, event counts and sponsor-reported p-values are reproduced as posted. Effect estimates, confidence intervals and p-values not attributed to the sponsor are independently calculated from the posted summary statistics.

18. Record Summary

NCT03770507, titled “Gas Exchange Kinetics and Work Load During Exercise,” is a completed randomized, single-masked crossover study sponsored by University of California, Irvine. Enrollment is 94. The registry describes exercise protocols using a cycle ergometer or treadmill among children, adolescents and adults.

The primary outcome is maximum oxygen uptake (VO2) during exercise, measured in L/min and specified as a mean with standard deviation. Heart-rate measurements during exercise are listed as a secondary outcome. The primary outcome description refers to breath-by-breath gas exchange and gives the timeframe as “At least 48 hours.”

Numerical primary- and secondary-outcome results, statistical estimates, confidence intervals, p-values, analysis methods, and analysis populations are not reported in the registry record. The adverse-event entries report zero serious adverse events, zero other adverse events and zero deaths in each named group.