Muscle Capillarization and Sarcopenia: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Muscle Capillarization and Sarcopenia (NCT03984994), a randomized na study. The primary outcome is Skeletal Muscle Capillarization.

2. Clinical Question

3. Trial Design

The registry record describes a randomized, single-masked, crossover trial, with an enrollment of 14. The condition listed is sarcopenia, and the sponsor is Baltimore VA Medical Center. The record lists the study as completed. Its start date is 2021-11-01, and its primary completion date is 2024-04-30.

The two sequences contain the same types of training in a different order. Participants assigned to aerobic exercise training followed by resistance training were to complete 3 months of aerobic exercise and then 3 months of strength training. Participants assigned to resistance training followed by aerobic exercise training were to complete 3 months of strength training and then 3 months of aerobic exercise. The record uses both “strength training” and “resistance training” in describing the interventions and sequence.

In a crossover design, participants receive interventions in a sequence rather than remaining in a single intervention group throughout. General interpretation of a crossover comparison can depend on sequence, period, and possible carryover effects. The registry record does not report whether a washout period was used, how period effects were handled, or whether carryover was assessed. It also does not describe the masking procedure beyond identifying the trial as single-masked.

The primary outcome analysis is restricted to the resistance-training portion: change from before to after that period. The registry states that participants completing resistance training in each arm were analyzed. The two reported arm counts are 5 and 6. No analysis of the aerobic-training period is reported. The registry lists skeletal muscle fiber size and muscle strength as secondary outcomes, but the numerical results for those outcomes are not included in the record summarized for this analysis. The phase is listed as NA.

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: Participants are assigned to groups upon completion of baseline testing.

Overall Study

Reasons for not completing this period:

Analysis population for the primary outcome, as defined in the registry: All participants completing the resistance training portion of the intervention in each arm were analyzed. Only data for the resistance training portion of the study are reported (change post-pre training). Data and analyses are not reported for aerobic exercise as this was not part of the aims/outcomes and was only assessed to gauge responses to only RT.

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: All participants assigned to an intervention are included.

6. Primary Endpoint

The registry lists the primary outcome as Skeletal Muscle Capillarization, measured over 3 months (post minus pre-resistance training).

The primary endpoint is skeletal muscle capillarization, expressed as capillaries per muscle fiber. It is a continuous measure summarized as a mean with standard error. The reported endpoint is the change from before to after the resistance-training period, over 3 months, rather than a measurement of change during aerobic exercise.

Capillarization describes the number of capillaries associated with muscle fibers. The study rationale proposes that increasing skeletal muscle capillarization through aerobic exercise might enhance muscular adaptations to strength training. Measuring capillarization change after resistance training therefore addresses a biological response relevant to that stated research question. The endpoint is not itself a direct measure of mobility or overall physical function, and the registry record does not say that it is intended to represent every aspect of sarcopenia.

The registry reports a mean change of 0.4 capillaries per muscle fiber in the aerobic-exercise-then-resistance-training arm and 0.2 in the resistance-training-then-aerobic-exercise arm. Each mean has a standard error of 0.1. The posted analysis describes the comparison as a mean difference in final values, while the primary endpoint description specifies post-minus-pre change over resistance training. That difference in wording is relevant when interpreting exactly what the reported test contrasts.

The endpoint is useful for examining the stated physiological question, but the reported result should be read as a comparison of this measure in the analyzed participants, not as a complete account of clinical outcomes. Results for the listed secondary outcomes are not reported in the registry record.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The posted primary endpoint is continuous: it is a numerical measure of capillaries per muscle fiber. The registry summarizes each arm with a mean and standard error. It reports changes after resistance training, defined as the value after training minus the value before training. The sponsor’s comparison is labeled a two-sided t-test and reports a mean difference in final values with a p-value.

What a mean describes

General statistical explanation: A mean is a measure of the center of a set of numerical observations. It can be useful for describing an average response, but it does not show how individual participant values are distributed. Two groups can have similar means while differing in variability or in the presence of unusual values. The registry record does not report participant-level measurements or a distributional summary beyond the means and standard errors.

In this study, the reported means are 0.4 and 0.2 capillaries per muscle fiber. They describe average changes in the analyzed arms, not the response of every participant. The registry reports standard errors of 0.1 for both means. An average change does not reveal whether individual changes were consistent, whether some participants changed in the opposite direction, or how the measurements were distributed.

What the standard error describes

General statistical explanation: A standard error describes the estimated sampling variability of a statistic, such as a mean. It is not the same as the spread of individual observations. Standard errors are often used to construct confidence intervals or conduct tests, but the registry record does not provide confidence limits for the arm means or for the reported comparison. Without those limits, readers have less direct information about the range of values compatible with the data under a specified method.

The same reported standard error in each arm does not imply that the participant-level variability is the same. The standard error depends on both variability and sample size. The registry does not report the standard deviations or individual observations needed to examine those components separately.

What a two-sided t-test asks

General statistical explanation: A two-sided test evaluates departures from a null value in either direction. A t-test uses the observed data and a reference distribution to assess how unusual a test statistic would be under its null hypothesis and assumptions. The registry gives p = 0.27 for the sponsor-reported comparison. This value should be interpreted as a measure of compatibility with that test’s null model, not as a probability that a particular sequence is better or worse.

The test entry describes the parameter as a mean difference in final values, while the primary endpoint description identifies a post-minus-pre change. The record does not provide a fuller statistical model or explain this terminology. It does not report whether the test accounts for the crossover structure, repeated observations within participants, or sequence and period effects. Those details matter because measurements in a crossover trial can be related within the same participant, and the order of interventions may matter to the analysis.

Why confidence intervals matter

General statistical explanation: A confidence interval gives a range of estimates compatible with the observed data and a specified procedure. Its width communicates precision, while its location helps show the direction and magnitude of effects that remain plausible. A p-value alone does not provide this range. The registry record reports no confidence interval for the arm comparison, so the precision of the mean difference cannot be assessed from such an interval in the posted results.

The arm-level standard errors provide some information about the means, but they are not a substitute for a confidence interval on the contrast. In a crossover study, the precision of a within-participant contrast can depend on the relationship between measurements from the same person. That relationship is not reported, so it should not be reconstructed from the arm summaries.

Why over-dispersion can matter

General statistical explanation: Over-dispersion occurs when observed variation is greater than a statistical model expects. When it is present and not accounted for, standard errors can be too small and tests can appear more decisive than warranted. This is a general concern in some count-based or clustered data settings, but the registry reports a continuous endpoint and does not identify an over-dispersion assessment. There is no basis in the record to say that over-dispersion was present or that a particular correction was used.

More broadly, the registry does not describe model diagnostics, transformation decisions, adjustment for baseline values, or covariates. Their use or absence cannot be inferred from the reported t-test label. The analysis should be read using the information actually recorded, without attributing an unreported model to the sponsor.

Planning calculations and observed results

General statistical explanation: A sample-size planning illustration asks how many participants per arm might be needed to detect an assumed effect under specified design assumptions. The assumptions described for the planning illustration are a two-sided significance level of 0.05, equal allocation, and a normal approximation; the effect to detect is a stated fraction of the observed effect. Such illustrations are conditional on those assumptions and are not observed trial outcomes, nor do they establish the probability that this completed study detected an effect.

The registry record does not report the trial’s own sample-size justification. It also does not report interim analyses or a detailed statistical analysis plan. Planning illustrations should not be read as evidence that the trial was designed around those assumptions. The analyzed arm counts and the observed comparison remain distinct from any hypothetical planning calculation.

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("Aerobic Exercise Training Followed by Resistance T", "Resistance Training Followed by Aerobic Exercise T")
n   <- c(5, 6)
m   <- c(0.4, 0.2)
sp  <- c(0.1, 0.1)
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  Aerobic Exercise Training Followed by Resistance T  5  0.400  0.224  0.122  0.678
CARM  Resistance Training Followed by Aerobic Exercise T  6  0.200  0.245  -0.057  0.457

11. Analyses Reported by the Sponsor

The registry’s sponsor-reported analysis is a two-sided t-test. It labels the estimand as a mean difference in final values, reports a difference of 0.2, and gives p = 0.27. No confidence interval is reported for that comparison. The arm-level means are 0.4 and 0.2 capillaries per muscle fiber, each with a standard error of 0.1.

No recalculated comparison is reported in the registry record summarized for this analysis. Consequently, there is no independent recalculated estimate or p-value to set alongside the sponsor’s result. The sponsor’s reported analysis is the available inferential result; it should not be replaced by an unreported reconstruction from rounded arm summaries.

The endpoint description says that the primary quantity is post-minus-pre change after resistance training, while the analysis entry says “Mean Difference (Final Values).” The registry does not explain whether these labels refer to the same analysis quantity. That wording should be retained as a limitation rather than resolved by assumption.

The reported p-value is evidence about the sponsor’s stated test under its assumptions; it is not a measure of the probability that the observed mean difference is real. The record does not provide enough methodological detail to reproduce the test or assess whether it accounts for the crossover structure.

12. Multiplicity, Missing Data and Analysis Populations

The registry lists skeletal muscle fiber size and muscle strength as secondary outcomes. It also reports four outcome measures and four analyses, but the results for the listed secondary outcomes are not reported in the registry record. The primary outcome description identifies capillarization change after resistance training as the outcome assessed for the study’s aims.

When multiple outcomes or multiple statistical tests are considered, the chance of at least one apparently unusual result can increase. General statistical explanation: Multiplicity procedures can control or describe that issue, depending on the analysis plan and the inferential goals. The registry record does not report a multiplicity adjustment, a prespecified hierarchy among outcomes, or a statistical analysis plan explaining how multiple tests were handled. It is therefore not possible to determine from the record whether the reported p-value was adjusted or whether other analyses were considered in interpreting it.

The analysis population is described as all participants completing the resistance-training portion of the intervention in each arm. That description indicates a completion-based analysis population for the primary outcome, rather than an explicit statement that all randomized participants were included. The arm-level outcome counts are 5 and 6, while the overall enrollment is 14. The registry does not report reasons for non-completion, the number of missing measurements, or how missing data were handled.

The record also does not describe an intention-to-treat analysis, imputation, sensitivity analyses, or exclusions beyond the completion criterion. Those methods should not be assumed. Because the trial is described as a crossover, it would also be useful to know how the analysis treated participants who completed only one period, if any, but that information is not reported in the registry record.

Without fuller information on outcome reporting, missingness, and the analysis population, the posted result should be interpreted as applying to the analyzed completers and the reported primary comparison. The available record does not establish whether unreported outcomes or missing observations would change the interpretation.

13. 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 registry reports serious adverse events for both training sequences. In each arm, 7 participants were listed as at risk, and 0 serious adverse events were reported. Deaths were also reported as 0 in each arm. The registry lists no serious adverse-event terms.

These figures are a record of what was reported for the groups and risk counts described. They do not show that no adverse events of any kind occurred. The registry separately reports 0 for other adverse events in each arm, with 7 participants at risk in each; however, the absence of reported events in these categories should not be read as proof that there was no risk.

General statistical explanation: Event counts from a small study can provide limited information about the frequency of uncommon outcomes. A zero count means that no event in that category was reported among the listed participants at risk; it does not establish that the underlying event probability is zero. The record does not describe the adverse-event collection period, severity definitions beyond the serious category, or how events were attributed to either training component.

The two sequences have different orders of the training periods, so these group figures should be read as reported rather than treated as a full assessment of comparative safety. They do not establish safety in other populations or settings.

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

The posted results describe changes in skeletal muscle capillarization after resistance training among participants who completed that part of the intervention. Mean changes were 0.4 capillaries per muscle fiber in the aerobic-exercise-first sequence and 0.2 in the resistance-training-first sequence. Both standard errors were 0.1. The sponsor-reported two-sided test gives p = 0.27 and reports a mean difference in final values of 0.2.

These results do not demonstrate that the sequences have the same effect. A p-value of 0.27 does not establish equivalence, and the registry does not report an equivalence margin or a confidence interval for the contrast. At the same time, the observed descriptive means alone do not establish a reliable difference. The uncertainty and the small analyzed arm counts limit how strongly the comparison can be interpreted.

The primary endpoint is a physiological measurement, not a direct measure of mobility, independence, or broader clinical benefit. Although the study rationale refers to muscular adaptations to strength training in older adults with sarcopenia, the reported primary result is confined to capillarization change after resistance training. The registry lists muscle fiber size and muscle strength as secondary outcomes, but their numerical results are not reported in the registry record.

The result also does not describe the effect of aerobic exercise itself on capillarization. The registry explicitly states that aerobic-exercise data and analyses are not reported because they were not part of the aims. Nor does the result establish how the two sequences compare across all periods of the crossover, because the record does not describe the analysis of period or carryover effects.

In short, the record offers a small-sample comparison of the reported resistance-training-associated changes and the sponsor’s test result. It does not establish a definitive presence or absence of a sequence difference, a clinical benefit, or a general effect of either training type.

15. Why This Trial Matters Statistically

This trial poses a statistical question that is more specific than whether exercise changes muscle. It asks whether resistance-training-associated capillarization change differs when aerobic exercise comes before strength training rather than after it. Keeping the sequence and the measured period clear is important: the primary result concerns resistance training, while aerobic-period data are not reported.

The crossover structure also makes the design relevant to how researchers analyze repeated observations. General statistical explanation: In a crossover study, observations from the same participant can be related, and outcomes may depend on the period or order in which interventions occur. An analysis that accounts for those features can differ from a simple comparison of independent groups. The registry identifies a crossover model but does not explain how the sponsor handled within-participant dependence, period effects, or carryover.

The registry’s compact result illustrates why a p-value is not enough to characterize evidence. The means, standard errors, arm counts, and p-value each convey different information. A confidence interval would help describe the range of contrasts compatible with the data, but none is reported. The trial therefore offers a useful example of the distinction between a descriptive difference and a precisely estimated comparative effect.

It also highlights the importance of clear endpoint and analysis labels. The endpoint description specifies change from before to after resistance training, whereas the sponsor analysis calls its parameter a mean difference in final values. Without clarification, readers should avoid assuming the exact estimand or reconstructing an analysis from summary values alone.

These are broadly useful statistical lessons for clinical researchers: define the outcome and analysis population precisely, make crossover methods transparent, report uncertainty for contrasts, and distinguish planning assumptions from observed findings. In this record, the findings remain bounded by the analyzed participants and the primary outcome reported.

16. 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 main trial-specific limitation is the small number of participants represented in the primary outcome summaries: the reported arm counts are 5 and 6, compared with an enrollment of 14. The registry does not give reasons for the difference between enrollment and the analyzed counts, nor does it report the number or pattern of missing measurements. The completion-based population description further limits conclusions to participants completing the resistance-training portion.

The registry gives no confidence interval for the sponsor-reported mean difference. The two arm means and standard errors provide descriptive summaries, but they do not show the uncertainty around the contrast itself. Individual observations, standard deviations, and the within-participant association relevant to a crossover analysis are not reported.

There is limited detail about the statistical methods. The registry labels the comparison as a two-sided t-test but does not state whether the analysis accounts for the crossover design, repeated measures, sequence, period, or carryover. It also does not clarify the difference between the endpoint description’s post-minus-pre change and the analysis label “Mean Difference (Final Values).” The statistical analysis plan and sample-size justification are not reported in the registry record.

The registry says that only resistance-training data and analyses are reported. Numerical results for skeletal muscle fiber size and muscle strength, both listed as secondary outcomes, are not reported in the record summarized for this analysis. Multiplicity handling is also not reported. These omissions prevent a broader assessment across all outcomes and analyses.

Finally, the outcome is a muscle capillarization measure, and the posted primary result does not directly establish effects on mobility, physical function, or other clinical outcomes. The record’s description does not support extrapolation beyond the participants and comparison analyzed.

17. Related Tutorials

18. Related Statistical Calculators

19. Sources

• ClinicalTrials.gov: Muscle Capillarization and Sarcopenia — NCT03984994.
• Registry record last updated 2025-10-29; status last verified 2025-10.
• Results first posted 2025-10-29.
• 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.

20. Record Summary

The registry record describes a completed randomized, single-masked crossover trial with an enrollment of 14 and sarcopenia as the listed condition. One sequence placed 3 months of aerobic exercise before 3 months of strength training; the other placed 3 months of strength training before 3 months of aerobic exercise.

The primary outcome is change in skeletal muscle capillarization after the resistance-training period, measured as capillaries per muscle fiber. The reported means are 0.4 and 0.2, with standard errors of 0.1 in each arm and analyzed counts of 5 and 6. The sponsor reports a two-sided t-test, a mean difference in final values of 0.2, and p = 0.27. A confidence interval is not reported.

The registry does not report aerobic-period analyses, numerical results for the listed secondary outcomes, detailed crossover modeling, missing-data methods, or the trial’s sample-size justification. The primary finding should therefore be read as a limited comparison of the reported resistance-training changes in the analyzed participants.