Exercise Training and Glucose Metabolism in Aging: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Exercise Training and Glucose Metabolism in Aging (NCT00701051), a non-randomized na study. The primary outcome is Baseline Glucose Utilization.

2. Clinical Question

3. Trial Design

The registry describes a completed, parallel-model study with nonrandomized allocation and no masking. Its listed enrollment is 90. The sponsor is the US Department of Veterans Affairs. The registry gives a start of 2006-10 and a primary completion of 2012-06, and lists the phase as NA.

The two arm descriptions identify older adults with normal glucose tolerance and older adults with impaired glucose tolerance. These are descriptions of participant groups, not evidence that one group was assigned to exercise and the other to serve as a control. Aerobic exercise training and detraining, defined in the record as cessation of exercise, are listed as behavioral interventions. The record does not explain how the interventions relate to the two arms, whether participants moved between conditions, or the timing and duration of any intervention.

This distinction matters for interpretation. In a randomized comparison, random assignment is used to make treatment groups comparable on average at baseline. Here, allocation is explicitly nonrandomized, and the listed arm descriptions distinguish groups by glucose-tolerance status. Differences between those groups could reflect factors other than glucose-tolerance status or exercise. The registry does not report an adjustment strategy that would address such differences.

The study summary frames the work around skeletal muscle capillarization, vascular growth factor expression, inflammation, insulin signaling, and glucose metabolism in older adults. Those are the proposed mechanisms and questions in the summary, not reported findings. The registry record does not provide a protocol-level account of intervention delivery, the analysis plan, participant flow, or the results needed to assess whether the proposed mechanisms changed.

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.

Screening

Reasons for not completing this period:

Exercise Intervention

Reasons for not completing this period:

Detraining Intervention (Optional)

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 Baseline Glucose Utilization, measured over baseline.

The primary measure is titled baseline glucose utilization and is described as insulin-stimulated glucose uptake. It is a continuous measure, with the unit µmol/kgFFM/pmol insulin/min. The registry identifies the summary statistic as a mean and the dispersion measure as a standard error. The timeframe is baseline.

In general, a measure of glucose uptake can describe how much glucose is taken up under the stated insulin-stimulated conditions. A baseline value can characterize participants before an intervention-related comparison, or provide context for comparisons between groups. Because this endpoint is explicitly listed at baseline, it should not be read on its own as a measure of change caused by exercise or detraining.

A mean gives a group-level summary of a continuous outcome. A standard error describes the precision of an estimated mean; it is not a description of how widely individual observations vary. A standard deviation is commonly used to describe individual variation, but the registry lists standard error instead. No endpoint mean, standard error, group-specific result, or inferential comparison is reported in the registry record. Consequently, the endpoint definition explains what was intended to be measured, but not the observed level of glucose uptake or the precision of an estimate.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The record identifies the primary outcome as a continuous measure summarized by a mean and standard error. It also identifies the study model as parallel and allocation as nonrandomized. These descriptors say something about the type of outcome and the broad design, but they do not provide a complete statistical analysis plan. No model specification, covariate list, hypothesis test, handling of repeated measurements, or confidence-interval procedure is reported in the registry record.

What does a mean describe?

In general, the mean is a measure of the center of a set of numeric observations. It can provide a concise description of a group’s average outcome, but it can conceal differences in the distribution of individual observations. For a continuous endpoint such as glucose uptake, the mean is interpretable as a group summary only alongside information about the measurement, participants, and variation. The registry supplies the endpoint definition and its intended summary, but no observed mean.

What does the standard error describe?

In general, a standard error describes the sampling precision of an estimated quantity, such as a mean. It concerns how much an estimate would vary across repeated samples under the statistical assumptions, rather than how much individual participants differ from one another. Standard error should not be mistaken for a standard deviation or a range containing most individual values. Because no standard error is reported for the primary endpoint, the precision of its mean cannot be evaluated from this record.

Why does nonrandomized allocation matter?

In general, random allocation helps balance both measured and unmeasured participant characteristics across comparison groups, on average. Nonrandomized allocation does not provide that protection. Differences between groups may reflect the group-defining characteristic, other participant characteristics, or the intervention, depending on how the groups and interventions were organized. Statistical adjustment can sometimes address measured differences, but it cannot automatically remove bias from unmeasured factors. The registry does not report whether adjustment was performed, what variables were considered, or how any adjusted estimate would be interpreted. The group descriptions alone do not justify treating the arms as a randomized comparison.

What can a confidence interval or test add?

In general, an effect estimate describes the size and direction of a contrast, while a confidence interval describes its statistical uncertainty under the analysis assumptions. A hypothesis test addresses compatibility of the data with a specified null hypothesis; a p-value is not the probability that a hypothesis is true and does not measure the size or importance of an effect. These quantities must be interpreted in light of the design, endpoint, and analysis choices. The registry record does not report an effect estimate, confidence interval, or p-value for the primary outcome, so no such interpretation can be made for this trial from the entry.

What do the planning assumptions mean?

The record describes planning illustrations based on an observed effect, rather than the trial’s own design. It states that the illustrations use a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation, with the detectable effect expressed as a stated fraction of the observed effect. It also distinguishes the planning convention for time-to-event outcomes from other outcomes. These are assumptions for a planning calculation, not evidence about how the trial was designed or analyzed. The registry does not report the numerical observed effect or the planning results in the registry record for interpretation here, so no planning sample size can be stated.

In general, such planning calculations ask how much information a future study might need to detect a chosen effect under specified assumptions. They depend on the effect size, variability, allocation, significance level, and analysis method. If an effect is smaller than the observed effect used as a reference, a larger sample may be needed to detect it with the same target power, all else being equal. This is a general statistical relationship, not a reported finding about this study. A planning illustration is not “observed power,” and it cannot substitute for an uncertainty interval around an actual study estimate.

How should continuous outcomes be analyzed?

In general, continuous outcomes can be compared using methods that estimate group means or differences, with the choice depending on the design, measurement schedule, distribution, and analysis assumptions. If multiple measurements are taken from the same participant, their correlation must be considered rather than treating them as independent observations. If outcome variability differs substantially across groups, a method that assumes equal variability may not be appropriate. These considerations explain why an analysis plan matters; they do not establish which method was used. The registry record does not report the measurement schedule in enough detail to identify a suitable model, nor does it list an analysis method.

The registry identifies a baseline primary measure and lists secondary measures related to postprandial glucose, cardiorespiratory fitness, and body composition. Those labels do not specify the statistical contrasts, the timing of every measurement, or how results were handled when a participant had more than one measurement. The record reports nine outcome measures but does not report analysis results for them. Any conclusions about change over time, relationships among outcomes, or a treatment effect would therefore go beyond the reported statistical information.

10. Confidence Intervals for Each Arm

No two-arm comparison is shown for this trial, but each arm's mean can be given with a t-based 95% confidence interval computed from the posted mean, spread and number of participants.

R code and output

arm <- c("Older Adults - Normal Glucose Tolerance", "Older Adults - Impaired Glucose Tolerance")
n   <- c(19, 12)
m   <- c(0.0062, 0.0035)
sp  <- c(8e-05, 0.0004)
sd  <- sp * sqrt(n)      # standard errors converted to SDs
for (i in seq_along(n)) {
  se <- sd[i] / sqrt(n[i]); h <- qt(0.975, n[i] - 1) * se
  cat(sprintf("CARM|%s|%d|%.3f|%.3f|%.3f|%.3f\n", arm[i], n[i], m[i], sd[i], m[i] - h, m[i] + h))
}

CARM  Older Adults - Normal Glucose Tolerance  19  0.006  0.000  0.006  0.006
CARM  Older Adults - Impaired Glucose Tolerance  12  0.004  0.001  0.003  0.004

11. Multiplicity, Missing Data and Analysis Populations

The registry lists a primary measure and reports nine outcome measures, with secondary measures concerning postprandial glucose, cardiorespiratory fitness, and body composition. It does not report the full set of outcome definitions, the planned contrasts for each measure, or an analysis plan describing how multiple comparisons would be handled. Multiplicity is the challenge of interpreting results when many outcomes or tests are considered: the more opportunities to identify a statistically unusual result, the more important it is to distinguish prespecified questions from exploratory analyses. No adjustment method, hierarchy, or testing strategy is reported in the registry record.

The record reports zero analyses. It does not provide participant-level missingness, the number of observations available for each outcome, reasons for missing measurements, or a method for handling missing data. It also does not report whether any analysis used all enrolled participants, only participants with observed outcomes, or another analysis population. Thus, the completeness and representativeness of outcome data cannot be assessed.

These omissions matter because missingness can affect both precision and interpretation. In general, a complete-case analysis may be biased if the availability of an outcome is related to participant characteristics or the outcome itself. Methods that use imputation or likelihood-based modeling require assumptions about the missing-data process and should be described. No such method or assumption is reported. The registry’s listed enrollment does not establish how many participants contributed to each endpoint analysis.

Without analysis methods, analysis populations, missing-data information, and multiplicity procedures, numerical outcome claims cannot be evaluated for robustness. These details are not reported in the registry record.

12. Safety Results

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

Other (non-serious) adverse events

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

Most frequent non-serious adverse event terms

The registry’s aggregate safety summary lists the Older Adults group with 90 at risk for serious events and 90 at risk for other events. It reports zero participants affected by a serious event and one participant affected by another event. These are counts as recorded, not estimates of comparative risk, and no rates or risk differences are reported.

The record does not list any serious event terms. It does not identify the other event, explain its severity, or state whether it was considered related to aerobic exercise training or detraining. The death count is not reported in the registry record. The aggregate group label also does not provide a safety comparison between the two glucose-tolerance arms or between intervention conditions.

In general, a zero count in a registry summary means no events were recorded in that category for the reported group and information; it does not establish that the risk is absent. Interpretation depends on follow-up, completeness of reporting, event definitions, and exposure. Those details are not available. The posted safety counts should therefore be read as limited descriptive information, not as evidence that an intervention caused or prevented an adverse event.

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

The record supports a description of the study’s design, its stated scientific questions, and the endpoint it intended to measure. The primary measure is baseline insulin-stimulated glucose uptake in older adults, expressed as a continuous outcome. The study summary concerns impaired glucose tolerance, skeletal muscle capillarization, and possible responses to aerobic exercise training and detraining.

It does not support a conclusion about the size or direction of a difference in baseline glucose utilization. No mean, standard error, effect estimate, confidence interval, or p-value for that endpoint is reported in the registry record. Nor does the record report analyses showing whether aerobic exercise training changed glucose uptake, capillarization, insulin signaling, vascular growth factor expression, inflammation, fitness, or body composition. Those topics appear as study questions or listed outcomes, not as findings.

The nonrandomized design and arm descriptions also constrain causal interpretation. The listed groups differ by glucose-tolerance status, and the record does not establish that they were exchangeable or that they form a direct exercise-versus-control comparison. Even if group results were available, an observed difference would need to be interpreted in light of group composition, intervention exposure, and the analysis method. These details are not reported.

The safety summary records zero serious events and one other event among the Older Adults group, but it does not identify the other event or its relation to an intervention. This limited information cannot establish comparative safety or exclude unrecorded events.

Accordingly, this registry entry is useful for understanding the intended research questions and the limits of the posted record. It does not provide sufficient analyzed outcome data to determine whether the proposed biological mechanisms were supported or whether exercise-related changes occurred. Lack of reported results should not be interpreted as a finding of no effect.

14. Why This Trial Matters Statistically

This study raises a statistical question that is important in aging research: how to distinguish differences associated with glucose-tolerance status from changes associated with an intervention. The registry frames the biology through skeletal muscle capillarization and glucose metabolism, while describing groups by normal or impaired glucose tolerance. Because allocation is nonrandomized, the design requires careful separation of descriptive group differences from causal claims about exercise.

The endpoint definition also illustrates why timing matters. Baseline insulin-stimulated glucose uptake can describe participants at the start of an intervention-related inquiry, but it is not itself a measure of an intervention’s effect. To evaluate change, the outcome values and comparison over time would need to be reported, along with the methods used to account for the design and repeated measurements if applicable. Those results and methods are not reported in the registry record.

The study’s proposed mechanisms make precise outcome reporting especially important. A biological rationale involving vascular growth factors, inflammation, insulin signaling, capillarization, and glucose metabolism can motivate a study, but each link requires evidence rather than inference from the rationale alone. Reporting effect estimates and their uncertainty would help readers distinguish the measured outcome from the proposed explanation.

Finally, the entry demonstrates the limits of registry-level safety summaries and planning illustrations. Aggregate event counts do not provide a detailed comparative safety analysis, and planning assumptions are not a substitute for observed results. Clear reporting of analysis populations, missing data, prespecified outcomes, and estimates would be necessary to judge how strongly the evidence addresses the study’s questions.

15. 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.

Important design and reporting details are absent from the registry record. Although the study is described as parallel and nonrandomized, the record does not explain how the glucose-tolerance groups relate to the exercise-training and detraining interventions. It does not describe the intervention regimen, duration, adherence, timing of detraining, or whether participants were measured before and after these conditions. Consequently, the intended intervention contrast cannot be reconstructed from the entry.

The primary endpoint is specified as a baseline measure, but no group-specific means, standard errors, or comparison are reported. The record lists nine outcome measures but reports zero analyses. It does not provide results for the stated mechanistic questions or the listed secondary measures. This prevents assessment of effect size, uncertainty, or consistency across outcomes.

The record does not describe eligibility criteria beyond the broad population labels, participant characteristics, outcome measurement procedures, or the statistical methods used. It also does not report covariate adjustment, missing-data methods, analysis populations, or multiplicity handling. With nonrandomized allocation, the absence of information about baseline balance and adjustment makes causal interpretation particularly limited.

Safety information is aggregated for Older Adults rather than presented by glucose-tolerance arm or intervention. The other event is not named, serious-event terms are not listed, and the death count is not reported. The record therefore does not allow detailed evaluation of event types, timing, or relation to an intervention.

These limitations concern what can be concluded from the registry record. They do not establish that analyses or additional information do not exist elsewhere; those details are simply not reported in this record.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: Exercise Training and Glucose Metabolism in Aging — NCT00701051.
• Registry record last updated 2015-04-06; status last verified 2015-03.
• Results first posted 2015-04-06.
• 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.

19. Record Summary

NCT00701051, titled “Exercise Training and Glucose Metabolism in Aging,” is listed as completed, with nonrandomized allocation, no masking, and a parallel model. Enrollment is listed as 90, and the sponsor is the US Department of Veterans Affairs. The arms describe older adults with normal glucose tolerance and older adults with impaired glucose tolerance.

Aerobic exercise training and detraining are listed as behavioral interventions. The primary measure is baseline insulin-stimulated glucose uptake, summarized as a mean with standard error. The registry also lists secondary measures concerning postprandial glucose, cardiorespiratory fitness, and body composition.

The record reports zero analyses and does not provide primary or secondary outcome results. Its safety summary lists zero serious events and one other event affecting participants in the Older Adults group; event details and the death count are not reported in the registry record.