Exercise Therapy to Reduce Heart Failure Symptoms; Sorting Mechanisms of Benefit: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Exercise Therapy to Reduce Heart Failure Symptoms; Sorting Mechanisms of Benefit (NCT03648762), a randomized na study. The primary outcome is Oxygen Uptake (VO2) Peak.

2. Clinical Question

The study’s rationale is that heart failure can involve skeletal muscle changes as well as cardiac effects, and that reduced exercise capacity may be related to skeletal muscle. The research therefore combines functional testing with skeletal muscle assessment. Planned functional measures described in the record include ventilatory gas indices, lower-body strength, grip strength, sit-to-stand performance, six-minute-walk distance, gait speed, inspiratory muscle strength, and questionnaires about quality of life and physical activity. Skeletal muscle biopsies were collected before and after training to study histology and biology.

Those aims are broader than a single test of peak oxygen uptake. The record lists several functional and biological outcomes, but it does not identify a single reported contrast that answers whether one program is better than another on the primary outcome. The primary-outcome entry also says that the outcome has several categories or time points and was not reduced to one comparison. Consequently, the registry description establishes the research question and outcome framework, but it does not supply a numerical answer to the primary comparison.

3. Trial Design

This was a randomized, parallel-group study with no masking. The registry record lists the status as completed and the enrollment as 65. Its primary-outcome description refers to 45 randomized participants, while noting that only 33 had both baseline and post-training peak oxygen uptake data available for that outcome. The record also lists five people who consented but withdrew before randomization in the adverse-event groupings. These entries describe different stages or reporting populations; the record does not reconcile them into a complete participant-flow account.

Three behavioral exercise interventions were compared: aerobic exercise, combined aerobic and strength exercise, and inspiratory muscle training. Each arm description specifies 12 weeks, a minimum of 3 days per week, and 60 minutes of exercise. The study summary describes assessments before and after training. The primary endpoint timeframe is stated as baseline and through study completion, an average of 14 weeks. This timeframe refers to the endpoint assessment schedule as recorded, rather than changing the stated 12-week intervention duration.

Random allocation can support a fair comparison of groups at the start of a study, on average, when allocation is implemented as intended. However, randomization alone does not establish that later outcome measurements are complete or that an analysis accounts for missing data. The registry record does not describe the randomization method, allocation concealment, or any stratification factors. These design details are not reported in the registry record.

The masking entry is none. In an exercise intervention study, participants and intervention staff may know which program is being undertaken, but the record does not give further information about who assessed outcomes or whether any outcome assessors were masked. The study is listed as not applicable for phase, consistent with behavioral exercise interventions rather than a drug phase designation.

The sponsor is the VA Office of Research and Development. The recorded start date is 2017-05-08, and primary completion is listed as 2019-09-30. The record describes additional outcomes including metabolomics, skeletal muscle gene expression, quality-of-life and daily-function questionnaires, and frequency and duration components of a physical-activity questionnaire. It reports nine outcome measures but no analyses. The full protocol, detailed analysis plan, and participant flow by reason for non-completion are not reported in the registry record.

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.

Before assignment: 65 participants consented to enroll in the study. 45 participants completed a baseline assessment and were randomized to one of the three intervention arms. The remaining 20 participants withdrew prior to completing baseline and before being randomized to one of the three intervention arms, so they are not included in this table. Serious adverse events reported after consent but prior to withdrawal for the non-randomized participants are included in a separate group in the adverse events table.

Overall Study

Reasons for not completing this period:

Analysis population for the primary outcome, as defined in the registry: Pre and post peak VO2 data available for 33 of 45 randomized participants. Remaining randomized participants did not complete a post assessment so are excluded from the table.

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.

Population: 65 participants consented to enroll in the study. Baseline demographics were captured for 48 of the participants who consented. 20 participants who consented to participate withdrew consent prior to completing baseline and prior to randomization. Baseline data were captured for 7 of these 20 participants prior to withdrawal. 45 participants completed baseline and were randomized to one of the three study arms. Baseline demographics were missing for 4 of these 45 randomized participants.

6. Primary Endpoint

The registry lists the primary outcome as Oxygen Uptake (VO2) Peak, measured over baseline and through study completion an average of 14 weeks.

Peak oxygen uptake, also written as peak VO2, is the primary endpoint. It is measured during cardiopulmonary exercise testing and expressed in ML/KG/Min. The outcome description identifies a mean with standard deviation as the summary form. Cardiopulmonary exercise testing measures ventilatory gas indices during exercise; peak oxygen uptake is used as an indicator of exercise capacity. This is a general explanation of the measure, not a claim about the results of this study.

The endpoint is relevant to the study’s stated interest in functional capacity and exercise training. The registry summary describes an interest in whether exercise interventions are accompanied by changes in skeletal muscle and function. Peak oxygen uptake provides one physiological measure within that broader set of outcomes. It does not, by itself, describe every aspect of function, quality of life, physical activity, or skeletal muscle biology also considered in the study.

The record specifies baseline and follow-up assessment through study completion, with an average timeframe of 14 weeks. It states that paired pre- and post-training peak oxygen uptake data were available for 33 of 45 randomized participants and that participants without a post-assessment were excluded from the endpoint table. The mean values, standard deviations, change estimates, confidence intervals, and statistical test results are not reported in the registry record. Without those numerical results, the size and precision of any change in peak oxygen uptake cannot be evaluated.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

What the design means. A randomized parallel-group design assigns participants to one of several interventions and follows each group over the same general study period. Randomization is intended to reduce systematic differences between groups at enrollment. It does not guarantee that groups will be identical, particularly in a study with a limited number of participants, and it cannot prevent missing outcome measurements after assignment. The registry record identifies randomization, three parallel exercise groups, and no masking. The specific randomization procedure and the method used to conceal allocation are not reported in the registry record.

What a continuous outcome summary means. Peak oxygen uptake is a continuous measurement, and the registry entry identifies the mean and standard deviation as its descriptive summaries. In general, a mean is an average, while a standard deviation describes how spread out individual measurements are around that average. A group’s mean before training and its mean after training can describe observed values at the two assessment times. A within-group change, however, does not by itself establish that the group changed more than another group. A comparative question generally requires a contrast between intervention groups, with an uncertainty measure.

What a confidence interval would add. In general, a confidence interval gives a range of values compatible with the data and the statistical procedure used, under its assumptions. It communicates precision as well as the estimated direction and size of an effect. A narrow interval indicates greater precision than a wide interval, but interpretation also depends on the question and the range of effects considered important. No confidence interval or treatment-effect estimate for peak oxygen uptake is reported in the registry record, so precision cannot be judged from the posted primary-outcome information.

Why the comparison needs to be specified. With three active programs, possible questions include whether each program changes from baseline, whether one program differs from another, or whether there is an overall difference among all groups. These are not interchangeable analyses. A baseline-to-follow-up change within one arm does not answer whether that arm performs differently from another. The record does not report a single primary contrast; it notes that the primary outcome has several categories or time points and was not reduced to one comparison. The statistical plan identifying a preferred contrast is not reported in the registry record.

What missing observations mean. The record states that pre- and post-training peak oxygen uptake data were available for 33 of 45 randomized participants and that participants without a post-assessment were excluded from the outcome table. An analysis limited to participants with paired measurements describes those with observed data. If people with missing outcomes differ systematically from those measured, the observed group averages may not represent all randomized participants. This is a general concern, not a finding about why data were missing in this study. Reasons for non-completion, patterns of missingness by arm, and any imputation or sensitivity analysis are not reported in the registry record.

Why over-dispersion can matter. General statistical methods must match the type and distribution of an outcome. For count outcomes, over-dispersion means that observed variability is greater than a model assumes; a poorly matched model can make uncertainty estimates unreliable. Peak oxygen uptake is listed as a continuous mean outcome, not a count, so count over-dispersion is not the central issue for this endpoint. The record does not identify the statistical model used for the continuous endpoint. It would be inappropriate to infer one from the outcome’s measurement scale alone.

Planning calculations versus observed evidence. General sample-size planning asks how many participants would be needed for a specified analysis to have a chosen chance of detecting a stated effect under assumptions. The record describes a planning illustration based on a fraction of an observed effect, using a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation. It specifies that such illustrations are not the trial’s own design justification. It also states that continuous-outcome illustrations are expressed as participants per arm. The record does not report a numerical planning result for the primary endpoint in the registry record relevant to interpretation. A planning illustration is not an observed result, and it is not observed power. The trial’s original sample-size justification is not reported in the registry record.

What statistical testing cannot establish by itself. In general, a p-value measures how unusual data at least as incompatible with a specified null model would be, if that model and its assumptions held. It does not measure the probability that a treatment works, the size of an effect, or the practical importance of a result. A p-value should be interpreted alongside an effect estimate, its precision, the design, and missing-data concerns. The registry record reports no primary-outcome p-value or analysis, so no test-based conclusion can be drawn from it.

Analysis details that remain unknown. The registry record reports no analyses and does not give the statistical model, handling of repeated measurements, covariate adjustments, or analysis population for the primary endpoint. It does not report whether an intention-to-treat approach was used or whether there were interim analyses. Such details cannot be reconstructed from the randomized design or from the fact that paired measurements were available for a subset. They are not reported in the registry record.

10. Multiplicity, Missing Data and Analysis Populations

The study includes three exercise groups and a broad range of outcomes. The registry lists peak oxygen uptake as the primary endpoint and also identifies functional measures, questionnaires, metabolomics, and skeletal muscle gene expression. When several outcomes, time points, or pairwise comparisons are examined, the chance of at least one apparently notable result can increase. General approaches to multiplicity include specifying a primary contrast in advance, adjusting tests, or clearly treating additional analyses as exploratory. The registry record does not report a multiplicity strategy or a hierarchy of comparisons.

The primary-outcome entry itself says the endpoint has several categories or time points and was not reduced to one comparison. No numerical primary-outcome analysis is listed, and the record reports no analyses. The statistical analysis plan, including how repeated measurements and comparisons among the three arms would be handled, is not reported in the registry record. It is therefore not possible to identify which inferential result, if any, was intended to be the main test.

For peak oxygen uptake, the record states that paired measurements were available for 33 of 45 randomized participants; those without a post-assessment were excluded from the endpoint table. The record does not provide reasons for missing post-assessments, missingness by arm, or analyses that include participants without paired data. It also does not describe imputation, sensitivity analyses, or whether all randomized participants were included in any analysis. The analysis population and missing-data methods are not reported in the registry record.

These omissions matter because complete-case summaries can be affected if the people with observed follow-up differ from those without it. This is a general limitation of interpreting incomplete follow-up, not evidence that bias occurred. Without a reported analysis plan and numerical results, neither the impact of missing observations nor the handling of multiple outcomes can be evaluated.

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.

Most frequent serious adverse event terms

Most frequent non-serious adverse event terms

Serious events with the highest arm-level rate: mechanical fall with fractures (20.0%), hypertension (20.0%), unknown respiratory disorder (20.0%), hypotension (20.0%), thigh skin flap removal (20.0%).

The registry record lists serious adverse events by group. It reports 10 affected participants among 16 at risk in the aerobic exercise group, 3 among 17 in the combined aerobic and strength group, and 5 among 12 in the inspiratory muscle training group. For the five participants who consented but withdrew before randomization, it reports 5 affected among 5 at risk. The record reports zero deaths in each listed group.

For other adverse events, the record reports zero affected among 16 at risk in the aerobic group, zero among 17 in the combined group, and 1 among 12 in the inspiratory muscle training group. It reports zero among the five people who withdrew before randomization. These are registry counts, not adjusted comparisons. The record does not provide a comparative risk estimate or statistical test for these figures.

The listed serious-event terms include Mechanical Fall with Fractures, Hypertension, Unknown Respiratory Disorder, Hypotension, Thigh skin flap removal, and Gout. The record gives 20.0% for each of the first five terms and 8.3% for Gout. The denominator and event-count basis for these percentages are not explained in the record, so they should not be treated as percentages of participants in an intervention arm. Serious-event counts alone do not establish cause, timing, or whether an event was related to exercise. Those details are not reported in the registry record.

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

The study record describes a randomized comparison of aerobic exercise, combined aerobic and strength exercise, and inspiratory muscle training in older adults with heart failure. Its primary outcome is peak oxygen uptake measured by cardiopulmonary exercise testing. The record also describes assessments of other aspects of function, quality of life, physical activity, and skeletal muscle. These features make the research question broader than a single physiological measurement.

The available registry information does not report numerical primary-outcome results or a single primary comparison. It therefore does not show how peak oxygen uptake changed in any arm, how the arms compared, or how precisely any difference was estimated. The absence of a reported result is not evidence that there was no effect, and it is not evidence that an intervention was beneficial. It means that the registry record does not supply the information needed to assess the primary treatment comparison.

The record notes paired peak oxygen uptake data for 33 of 45 randomized participants, with participants lacking a post-assessment excluded from the outcome table. This limits the number of randomized participants represented in that endpoint summary. Without information about why follow-up was missing or how missingness was handled analytically, the representativeness of the observed measurements cannot be assessed.

Safety counts are also reported, including serious adverse events and other adverse events. They describe events in the groups as recorded, but they do not on their own establish that an intervention caused an event or allow a reliable comparative estimate. Timing, event attribution, and detailed ascertainment procedures are not reported in the registry record.

In general, an outcome estimate should be interpreted in light of its magnitude, precision, study design, missing data, and the analysis that produced it. Here, the primary endpoint estimates and inferential statistics are not reported in the registry record. The appropriate statistical conclusion is therefore limited: the registry describes the study and some participant and safety counts, but it does not provide enough primary-outcome evidence to quantify or compare the exercise programs’ outcomes.

13. Why This Trial Matters Statistically

This study is statistically notable for asking a comparative question across three active exercise programs while measuring several dimensions of function and muscle biology. That structure makes a clearly specified primary contrast important. A within-group pre/post change, an overall difference among groups, and a pairwise comparison answer different questions. The registry record identifies peak oxygen uptake as primary but does not reduce its several categories or time points to one reported comparison.

The record also illustrates why participant flow and outcome availability matter in interpreting randomized studies. Although it lists 45 randomized participants in the primary-outcome description, paired peak oxygen uptake observations were available for 33. A randomized assignment describes how treatment groups were formed; it does not ensure that every participant contributes a follow-up measurement. Reporting the reasons for missingness and the analysis population would help readers judge how the available data relate to the randomized groups.

Another statistical issue is the breadth of outcomes. The record names functional tests, questionnaires, physical-activity measures, metabolomics, and gene expression in addition to peak oxygen uptake. Looking at many outcomes or contrasts can complicate interpretation unless the primary test and multiplicity approach are clear. Those analysis details are not reported in the registry record.

Finally, the record distinguishes planning illustrations from the trial’s own design justification. This distinction matters because calculations based on an observed effect are not proof that a study was adequately designed, and planning values are not observed results. With no numerical primary-outcome analysis reported, readers cannot evaluate effect magnitude or precision. The statistical contribution of the record is therefore mainly its description of the design, endpoint, follow-up availability, and limits of the posted results.

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.

A central limitation of the registry record is that it does not report numerical results for peak oxygen uptake, despite identifying it as the primary endpoint. Mean values, standard deviations, estimated changes, between-group contrasts, confidence intervals, and p-values are not reported in the registry record. This prevents assessment of both the direction and precision of the primary outcome.

The primary-outcome description states that 33 of 45 randomized participants had pre- and post-training data, and that the remaining randomized participants did not complete a post-assessment and were excluded from the endpoint table. Reasons for non-completion, timing of withdrawal, and follow-up completeness by arm are not reported. The approach to missing outcomes and the analysis population are also not reported in the registry record.

The study has three active intervention groups and a range of functional and biological outcomes, but the record does not identify a single primary between-group contrast or a multiplicity strategy. It does not report the statistical model, covariate adjustment, treatment of repeated measures, or any interim analyses. These details are not reported in the registry record, so the analysis cannot be reconstructed from the design description.

The overall enrollment entry is 65, while the primary-outcome description refers to 45 randomized participants and the adverse-event listings include five people who withdrew before randomization. The record does not provide a full participant-flow explanation linking those counts. It also does not report detailed outcome-assessor masking, intervention adherence, or reasons for differences in outcome availability.

Safety reporting gives counts and selected event terms, but detailed timing, attribution, ascertainment procedures, and the basis for the listed term percentages are not reported. These limitations concern what can be concluded from the registry record; they do not establish that the underlying study lacked these procedures or analyses.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: Exercise Therapy to Reduce Heart Failure Symptoms; Sorting Mechanisms of Benefit — NCT03648762.
• Registry record last updated 2024-06-24; status last verified 2024-02.
• Results first posted 2024-06-24.
• 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

The registry record describes a completed, randomized, unmasked, parallel study of three exercise programs for older adults with heart failure. The interventions were aerobic exercise, combined aerobic and strength exercise, and inspiratory muscle training, each described as 12 weeks with a minimum of 3 days per week for 60 minutes. The listed sponsor is the VA Office of Research and Development, and enrollment is 65.

Peak oxygen uptake measured by cardiopulmonary exercise testing is the primary outcome. The record states that paired measurements were available for 33 of 45 randomized participants. It lists additional functional, questionnaire, activity, metabolomics, and skeletal muscle outcomes, but reports no analyses and no numerical primary-outcome comparison. Serious adverse-event counts are listed by group, with zero deaths reported in each group.

The registry information therefore supports a description of the trial design and selected safety counts, but not an estimate of the primary treatment effect or its precision. The analysis plan, missing-data methods, and multiplicity approach are not reported in the registry record.