Enhancing Skeletal Adaptations to PTH and Exercise: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Enhancing Skeletal Adaptations to PTH and Exercise (NCT05029128), a na na study. The primary outcome is Change in C-terminal Peptide of Type 1 Collagen (CTX).

2. Clinical Question

The study’s stated rationale is that exercise can coincide with a decline in blood calcium and mobilization of calcium from bone. Its broader aim was to assess whether further research on pre-exercise calcium supplementation to minimize that decline is warranted. That rationale is not itself evidence that calcium was tested: the listed intervention is endurance exercise training, and the design has no comparator. The primary endpoint instead concerns an acute bone-resorption marker around exercise. The registry record describes the question and measurement schedule, but it does not report numerical CTX findings that would answer whether CTX changed or how consistently any change occurred.

3. Trial Design

The registry record identifies the trial as NCT05029128, titled “Enhancing Skeletal Adaptations to PTH and Exercise.” Its official title is “Enhancing Skeletal Adaptation to Exercise by Attenuating the Acute Disruption of Calcium Homeostasis During Exercise.” The listed sponsor is the VA Office of Research and Development. The record lists the phase as NA, allocation as NA, masking as NONE, and model as SINGLE GROUP. Status is COMPLETED.

Enrollment is recorded as 18. The intervention is behavioral endurance exercise, and the arm description says all participants engage in exercise training. There is no separately described control arm or randomized allocation. Consequently, the study design describes observations in an exercise group rather than a between-group comparison. It cannot, on its own, separate changes associated with exercise from changes that might also occur over time or under other conditions.

The recorded start date is 2023-01-01, and the primary completion date is 2025-04-01. The primary outcome timeframe specifies CTX change from immediately before exercise to 60 minutes after exercise during the 1st, 8th, and 16th exercise bout. The registry also states that results are for each exercise bout and for the average of all the bouts combined. It does not give further details about how exercise training was delivered or how the bout assessments were scheduled beyond this outcome description.

The study lists secondary outcomes concerning P1NP during exercise, urinary calcium excretion, serum ionized calcium, total calcium, parathyroid hormone, phosphorus, hematocrit, and hemoglobin. The record lists 15 outcome measures and 0 analyses. Numerical outcome estimates and a detailed statistical analysis plan are not reported in the registry record. The record therefore supports a description of the design and intended measurements, but not an assessment of observed changes or comparative effects.

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: Screening assessments occurred between consent/enrollment and the start of data collection. Of the 18 who signed the consent, 8 passed the screening assessments. All 8 participants who passed screening started the study and 6 completed the study. There is no randomization to a study arm so all participants completed the same exercise intervention (4 weeks of treadmill exercise).

Screening Eligibility Determination

Reasons for not completing this period:

Exercise Collection

Reasons for not completing this period:

Analysis population for the primary outcome, as defined in the registry: CTX was only analyzed for those who completed the study (N=6).

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: Baseline characteristics are only reported for those who proceeded to data collection.

6. Primary Endpoint

The registry lists the primary outcome as Change in C-terminal Peptide of Type 1 Collagen (CTX), measured over The primary outcome for Aim 1 is the change in CTX from immediately before exercise to 60 minutes after exercise during the 1st, 8th, and 16th exercise bout. Results are for each exercise bout and for the average of all the bouts combined..

The primary endpoint is change in the C-terminal peptide of type 1 collagen, abbreviated CTX, measured in ng/mL. CTX is described in the registry record as a marker of bone resorption. The stated rationale for using it is that an increase in CTX in response to exercise is evidence of an acute catabolic response of bone. Thus, the endpoint focuses on a short-term biological response around exercise, rather than a long-term change in bone mass, bone strength, or fracture occurrence.

The specified change compares the measurement immediately before exercise with the measurement 60 minutes after exercise. This assessment is specified for the 1st, 8th, and 16th exercise bout, with results intended for each bout and for the average across all bouts combined. These repeated time points make it possible in principle to describe whether an acute response differs across the listed bouts, but the registry record does not report the estimates or the method used to combine them.

The endpoint is reported as a mean with standard deviation. In general, a mean describes the average observed value or change, while a standard deviation describes variation among observations. Neither measure by itself establishes a causal effect, especially in a single-group study without a comparison arm. CTX was analyzed only among study completers (N=6). The numerical mean, standard deviation, and any interval estimates for the primary outcome are not reported in the registry record, so the observed magnitude and variability cannot be described.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

What does a mean and standard deviation describe?

The primary outcome is classified as continuous and reported using a mean and standard deviation. In general, a mean summarizes the central level of measured values, while the standard deviation describes how dispersed the values are around that mean. The mean can make an average pattern easier to interpret, but it can conceal differences among participants. The standard deviation provides information about variability in the observations; it is not the same as the uncertainty in the estimated mean.

The registry record does not report a numerical mean or standard deviation for CTX. It also does not report confidence intervals, standard errors, or test statistics for the primary outcome. As a result, the outcome type and summary approach are known, but the empirical distribution and uncertainty of the estimate cannot be evaluated. General statistical interpretation of means and standard deviations cannot fill in those missing results.

How should the before-and-after change be understood?

The primary endpoint is defined as the change from immediately before exercise to 60 minutes after exercise. This is a within-participant temporal contrast in the described exercise setting, not a contrast between a treatment group and a control group. In general, comparing measurements from the same person can account for stable differences between people when estimating change, but the registry record does not state the statistical model used for this endpoint. It would be inappropriate to assume a particular paired test, repeated-measures model, or adjustment procedure.

The outcome timeframe names the 1st, 8th, and 16th exercise bout and says results are for each bout and the average of all bouts combined. Measurements at multiple bouts may be statistically related because they come from the same participants. General methods for repeated observations account for such dependence rather than treating all measurements as unrelated. The registry record does not say how dependence was handled or how the average across bouts was constructed. It also does not report bout-specific estimates, so no pattern across bouts can be evaluated.

What does the analysis population imply?

The CTX outcome was analyzed only for participants who completed the study (N=6). This identifies the population included in the stated primary analysis, but it does not explain how completion was defined, why other enrolled participants were not included, or whether all completers contributed data at every specified bout. These details are not reported in the registry record. In general, restricting an analysis to completers can affect how well its findings represent all enrolled participants if completion is related to outcomes or other participant characteristics. Whether that concern applies cannot be determined from the available record.

The record lists enrollment as 18, but it does not describe an intention-to-treat analysis or another analysis population. It also does not state whether missing measurements were imputed, excluded, or handled by a model. Those are distinct methodological choices, and none can be inferred from the completer-only statement.

What can a significance test or interval show?

In general, a significance test evaluates how compatible observed data are with a specified null model under stated assumptions. A p-value does not express the probability that a treatment works, and a threshold alone does not describe the size or importance of a change. A confidence interval gives a range of effect values compatible with the data and analysis under the chosen method; its width helps communicate precision. The registry record does not report a p-value, confidence interval, or other inferential statistic for CTX, so statistical significance and precision cannot be assessed.

Nor does the record describe whether an analysis adjusted for other variables. Adjustment can change the estimated association and its uncertainty, but no covariates or adjustment plan are listed. The registry record reports 0 analyses, and a detailed statistical plan is not reported in the registry record. The design and endpoint description should not be mistaken for a full specification of the analysis.

What do the planning assumptions mean?

The sample-size assumptions describe planning illustrations based on an observed effect, using a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation; the effect to detect is a stated fraction of the observed effect. These are planning assumptions, not evidence that the trial itself used a two-arm design. The actual registry design is single-group, and no control arm is listed. The stated planning assumptions also do not establish that the trial's own sample-size justification used those choices; its sample-size justification is not reported in the registry record.

Planning illustrations describe the number of participants that might be needed under specified assumptions. They are not observed power and do not show that an observed outcome is reliable. Here, the record does not report numerical CTX results from which the observed effect or precision could be assessed, and no calculated planning counts are stated in the registry record. Any planning value should therefore be understood as conditional on the assumptions used, not as an observed feature of the single-group study.

10. Multiplicity, Missing Data and Analysis Populations

The registry record lists 15 outcome measures, including the primary CTX outcome and secondary measures involving P1NP, urinary calcium excretion, calcium, PTH, phosphorus, hematocrit, and hemoglobin. It lists 0 analyses. A detailed statistical analysis plan, including which outcomes or contrasts were treated as confirmatory, is not reported in the registry record.

When several outcomes or repeated contrasts are examined, the chance of at least one apparently unusual result can increase if each is assessed separately. General approaches to multiplicity may define a primary test in advance, adjust thresholds, or interpret a family of results together. The registry record does not state whether any multiplicity procedure was planned or used. With no numerical results or analysis descriptions, it is not possible to determine how multiple outcomes or bout-specific comparisons were handled.

The primary outcome population is described as participants who completed the study (N=6). Missing-data methods, reasons for non-completion, and the extent of missing measurements are not reported in the registry record. The record does not state whether analyses included all available observations, required complete measurements at each bout, or used imputation or another method. It also does not identify any sensitivity analysis addressing missing data.

These omissions limit assessment of both the analysis population and the stability of conclusions. They do not establish that a particular method was absent from the study; they mean that the method is not reported in the registry record. The enrolled population, completer population, and observations available at each scheduled measurement should not be treated as interchangeable.

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 non-serious adverse event terms

The adverse-event summary lists an Aerobic Exercise group with 8 participants at risk for serious adverse events and 0 participants affected by serious adverse events. It lists 8 participants at risk for other adverse events and 2 affected by other adverse events. Deaths are recorded as 0, and no serious adverse-event terms are listed.

These are event-summary figures, not a comparison between groups: the trial has a single-group design and no separate control arm is described. The figures also do not provide event-level detail, timing, severity beyond the serious-versus-other classification, or an attribution assessment. Those details are not reported in the registry record. The adverse-event group count at risk should not be assumed to represent all enrolled participants, since the registry separately lists enrollment as 18 and does not explain the difference.

Zero reported serious adverse events means none are listed for the stated group and risk count in this record; it does not establish that serious events are impossible or that the intervention has been shown to be safe. Similarly, the record’s count of other adverse events does not by itself establish a causal relationship with exercise. The registry record does not report a control comparison that could help distinguish background events from events associated with the study intervention.

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

This registry record is informative about the study question, intervention category, primary measurement, and analysis population. It describes an exercise-training study in which the primary endpoint is acute change in CTX, a marker of bone resorption, measured before and after exercise at specified bouts. The primary outcome was analyzed only for participants who completed the study (N=6).

It does not report numerical CTX estimates, variability, confidence intervals, or statistical tests. Consequently, the record does not show whether CTX changed after exercise, how large any change was, how precise an estimate might be, or whether the response differed across exercise bouts. The biological interpretation in the endpoint description explains why CTX was selected; it is not a result showing that an acute catabolic response occurred in this study.

The single-group design also limits causal interpretation. There is no like-for-like control group in the registry record, so any reported before-and-after change would not alone isolate the effect of exercise from other influences. The listed intervention is endurance exercise training. Although the study rationale raises pre-exercise supplemental calcium as a question for further research, calcium supplementation is not listed as an intervention and the record does not directly test it.

The study’s findings therefore cannot be used from this record to quantify a change in bone resorption, establish the effect of exercise on skeletal outcomes, or judge the effect of calcium supplementation. The record does not report long-term bone mass, bone strength, or fracture results as outcomes in the listed primary endpoint. It offers a description of a measurement question, not the numerical evidence required to answer that question.

For interpretation, the distinction between intended measurements and reported results is central. The trial is marked completed, but completion status does not supply missing outcome estimates. The absence of detailed analysis and missing-data methods further limits evaluation. These limitations are reasons to keep conclusions within the information the registry record actually reports, rather than to infer a favorable, unfavorable, or null result.

13. Why This Trial Matters Statistically

The study highlights a statistical distinction between a physiological measurement question and a clinical outcome question. CTX is described as a marker of bone resorption, and the endpoint focuses on acute change around exercise. That measure may characterize a short-term response, but it is not itself a direct measure of long-term bone strength or fracture risk. Interpreting a biomarker requires keeping its measurement timescale and intended meaning in view.

Design is equally important. A single-group study can describe measured changes in participants undergoing exercise training, but without a comparison group it cannot provide the same contrast as a controlled trial. This matters especially when the broader rationale raises a possible nutritional intervention: the listed intervention is exercise, and calcium supplementation is not listed. The primary question and the intervention actually studied are not interchangeable.

Analysis population and reporting also shape what can be learned. Enrollment is listed as 18, while CTX was analyzed only for study completers (N=6). The registry record does not explain the difference or report numerical results. Without estimates and their uncertainty, readers cannot assess the magnitude, variability, or precision of the endpoint. Without documented missing-data and multiplicity methods, they also cannot evaluate how the analysis choices may affect interpretation.

These features make the record a useful illustration of why statistical interpretation depends on more than a stated endpoint and completed status. The design, analyzed population, outcome estimates, uncertainty, and reporting of methods all matter. In this case, the record describes a potentially relevant question about exercise-related calcium balance and skeletal biomarkers, but it does not report the results needed to determine what the CTX measurements showed.

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 most consequential limitation for interpreting the primary outcome is that numerical CTX findings are not reported in the registry record. No mean change, standard deviation, confidence interval, or test result is available. Thus, the observed direction and magnitude of the endpoint, its variability, and its precision cannot be assessed.

The primary outcome population is restricted to study completers (N=6), whereas enrollment is listed as 18. The record does not explain why the outcome analysis includes only completers, give reasons for non-completion, or describe available CTX measurements by bout. It does not report how missing outcome data were handled. The effect of these unknowns on representativeness or estimate stability cannot be determined.

The single-group design lacks a separate control comparison. This limits causal attribution for any change between the pre-exercise and post-exercise measurements. The record does not list calcium supplementation as an intervention, even though the study rationale discusses whether further research on pre-exercise calcium is warranted. The study therefore should not be read as a direct test of that supplement.

The registry lists 15 outcome measures but 0 analyses, and it does not report a detailed statistical analysis plan, multiplicity procedure, covariate adjustment, or method for handling repeated observations across bouts. The record also does not provide enough information to assess whether all participants contributed data at each stated time point or how the average across bouts was formed.

Finally, the adverse-event summary has a group at-risk count of 8, distinct from the enrollment count, with no explanation of that denominator. It reports counts but not event descriptions or attribution details. These reporting gaps do not establish that methods or events were absent; they limit what can be concluded from the registry record.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: Enhancing Skeletal Adaptations to PTH and Exercise — NCT05029128.
• Registry record last updated 2026-04-06; status last verified 2026-03.
• Results first posted 2026-04-06.
• 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.

18. Record Summary

NCT05029128 is a completed, single-group study of endurance exercise training sponsored by the VA Office of Research and Development. Enrollment is listed as 18. The primary outcome is change in CTX from immediately before exercise to 60 minutes after exercise during the 1st, 8th, and 16th exercise bout, with the primary analysis limited to study completers (N=6).

The registry record describes CTX as a marker of bone resorption and lists secondary outcomes involving P1NP, urinary calcium excretion, serum calcium, PTH, phosphorus, hematocrit, and hemoglobin. It lists 15 outcome measures and 0 analyses. Numerical primary and secondary outcome results, detailed analysis methods, and missing-data procedures are not reported in the registry record.

The design has no listed comparator, and pre-exercise calcium supplementation is discussed as a rationale for possible further research rather than as a listed intervention. The adverse-event summary records 0 serious events, 2 other adverse events, and 0 deaths among the stated group counts. These details describe the registry entry but do not provide a controlled estimate of exercise effects or numerical CTX findings.