Dose-response of Physical Exercise on Pelvic Floor Muscle Function in Postmenopausal Women With Urinary Incontinence: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Dose-response of Physical Exercise on Pelvic Floor Muscle Function in Postmenopausal Women With Urinary Incontinence (NCT04351750), a randomized na study. The primary outcome is Pelvic Floor Muscle Function Measured by Digital Palpation.

2. Clinical Question

3. Trial Design

The registry record describes a randomized, parallel-group trial with no masking. The comparison involved three groups: high-intensity general exercise plus pelvic floor muscle training, low-intensity general exercise plus pelvic floor muscle training, and pelvic floor muscle training alone. The sponsor is National Cheng Kung University. The record lists the study as completed and records enrollment of 47 participants.

The primary outcome was pelvic floor muscle function measured by digital palpation, with absolute values assessed at 8 weeks. The primary result lists group sizes of 11, 12, and 12 for the high-intensity, low-intensity, and control groups, respectively. The registry record notes one missing primary assessment in each group because participants declined the test due to embarrassment.

The posted primary comparisons are each against the control group; they are not a direct high-intensity-versus-low-intensity comparison. Allocation concealment, how the random sequence was generated, the intended analysis population, and the original statistical analysis plan are not reported in the registry record. The record does not report the trial's original sample-size assumptions or justification, interim analyses, or a sponsor-reported inferential analysis for the posted outcomes.

4. Participant Flow and Accounting

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

Overall Study

Analysis population for the primary outcome, as defined in the registry: There were three missing data of pelvic floor muscle function (high-intensity group n=1, low-intensity group n=1, control group n=1) as the participants declined the assessment due to embarrassment with the test.

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 Pelvic Floor Muscle Function Measured by Digital Palpation, measured over absolute values at 8 weeks.

The primary endpoint is pelvic floor muscle function, described as muscle strength, measured through digital palpation. Participants performed three maximum contractions, each held for five seconds, with five seconds of rest between contractions. The maximum value from those attempts was recorded as maximal voluntary contraction. The score used the modified Oxford grading scale, a six-point scale running from 0, no contraction, to 5, strong contraction with lift. A higher score indicates stronger muscle function on this scale.

Digital palpation provides an assessment based on a physical examination rather than relying only on participants' reports. The registry description identifies the use of self-reported measures as a potential source of response bias, which is one reason for including an objective measure of pelvic floor muscle function. The endpoint is nevertheless a graded score, not a direct measurement in units of force. Its interpretation is tied to the scale and the examiner's assessment.

The posted primary endpoint is the absolute score at 8 weeks. The registry record does not report baseline scores alongside the results or describe a baseline-adjusted analysis. Consequently, these posted figures describe group scores at the stated follow-up time; they do not by themselves show the amount of change within each group.

7. Results Posted in the Registry

• High-intensity Group: mean 4.00 versus 3.75 on control; difference 0.25 (95% CI -0.58 to 1.08), standardized effect d = 0.24; z-test p = 0.556.
• Low-intensity Group: mean 3.25 versus 3.75 on control; difference -0.50 (95% CI -1.31 to 0.31), standardized effect d = -0.49; z-test p = 0.227.

8. Secondary Efficacy Endpoints

The registry also posts results for secondary outcomes. For each outcome below, the endpoint type, the test applied to the posted summary statistics, the result and its interpretation are given in turn. Secondary endpoints are usually not adjusted for multiple testing, so they support rather than confirm the primary finding.

International Consultation on Incontinence Questionnaire-Urinary Incontinence Short Form

• Endpoint type: Continuous: a mean value per participant, compared as a difference in means.
• Test: Unadjusted two-sample z-test for the difference in means, using the posted standard deviations.
• Result:
  • High-intensity Group: mean 6.75 versus 7.15 on control; difference -0.40 (95% CI -3.50 to 2.70), standardized effect d = -0.10; z-test p = 0.800.
  • Low-intensity Group: mean 4.92 versus 7.15 on control; difference -2.23 (95% CI -5.29 to 0.83), standardized effect d = -0.56; z-test p = 0.154.
• Interpretation:
  • The 95% confidence interval includes no difference, so these data do not show a statistically significant difference between High-intensity Group and the control. The interval gives the range of effects that remain compatible with the data.
  • The 95% confidence interval includes no difference, so these data do not show a statistically significant difference between Low-intensity Group and the control. The interval gives the range of effects that remain compatible with the data.

International Consultation on Incontinence Questionnaire Lower Urinary Tract Symptoms Quality of Life

• Endpoint type: Continuous: a mean value per participant, compared as a difference in means.
• Test: Unadjusted two-sample z-test for the difference in means, using the posted standard deviations.
• Result:
  • High-intensity Group: mean 32.17 versus 32.69 on control; difference -0.52 (95% CI -7.09 to 6.05), standardized effect d = -0.06; z-test p = 0.877.
  • Low-intensity Group: mean 27.85 versus 32.69 on control; difference -4.84 (95% CI -10.94 to 1.26), standardized effect d = -0.61; z-test p = 0.120.
• Interpretation:
  • The 95% confidence interval includes no difference, so these data do not show a statistically significant difference between High-intensity Group and the control. The interval gives the range of effects that remain compatible with the data.
  • The 95% confidence interval includes no difference, so these data do not show a statistically significant difference between Low-intensity Group and the control. The interval gives the range of effects that remain compatible with the data.

International Prostate Symptom Score

• Endpoint type: Continuous: a mean value per participant, compared as a difference in means.
• Test: Unadjusted two-sample z-test for the difference in means, using the posted standard deviations.
• Result:
  • High-intensity Group: mean 7.25 versus 8.23 on control; difference -0.98 (95% CI -4.78 to 2.82), standardized effect d = -0.20; z-test p = 0.613.
  • Low-intensity Group: mean 6.31 versus 8.23 on control; difference -1.92 (95% CI -6.08 to 2.24), standardized effect d = -0.36; z-test p = 0.365.
• Interpretation:
  • The 95% confidence interval includes no difference, so these data do not show a statistically significant difference between High-intensity Group and the control. The interval gives the range of effects that remain compatible with the data.
  • The 95% confidence interval includes no difference, so these data do not show a statistically significant difference between Low-intensity Group and the control. The interval gives the range of effects that remain compatible with the data.

The posted secondary results cover urinary incontinence symptoms, lower urinary tract symptoms and quality of life, and urinary symptom scores. Across these outcomes, the group means and recalculated comparisons do not show a consistent pattern in which both exercise groups differ from control in the same direction. Some estimates are close to zero, while others place the low-intensity group mean below the control mean. The reported comparison intervals include zero, leaving substantial uncertainty about the direction and size of the differences.

This broad pattern does not sharpen the primary result into a clear conclusion. The primary endpoint concerns muscle function, whereas the secondary endpoints capture reported symptoms or quality-of-life measures. They address related but distinct aspects of the study question, so alignment or disagreement among their numerical patterns would not by itself establish a causal mechanism or resolve uncertainty in the primary comparison.

The registry lists additional outcomes, including a bladder diary and a physical activity questionnaire, but outcome results for those measures are not reported in the registry record. The available secondary comparisons are unadjusted recalculations from posted group means and standard deviations; no sponsor-reported inferential analyses are listed. Their p-values should be interpreted cautiously because the record does not describe a multiplicity strategy, such as how the chance of false-positive findings across multiple outcomes and comparisons was addressed.

Secondary outcomes are often useful for understanding the range of measured effects, but multiple comparisons make isolated findings less persuasive unless the analysis plan accounts for that multiplicity. In this record, the secondary results are best read as descriptive context alongside the primary endpoint, not as independent confirmation of a treatment effect.

Secondary outcomes registered for this trial, for reference (only those above were recalculated):

• International Consultation on Incontinence Questionnaire-Urinary Incontinence Short Form
• International Consultation on Incontinence Questionnaire Lower Urinary Tract Symptoms Quality of Life
• International Prostate Symptom Score
• 3-day Bladder Diary
• International Physical Activity Questionnaire

9. Statistical Interpretation

10. Statistical Methods Explained

Continuous outcome results are reported as group means and standard deviations. A mean describes the average score among participants contributing to that outcome; a standard deviation describes how dispersed individual scores were around that mean. The means summarize the observed group results, while the standard deviations help characterize variation within each group. Neither statistic alone describes the uncertainty in a between-group comparison.

What does a mean difference represent?

Each primary comparison subtracts the control-group mean from the mean in one exercise group. The high-intensity comparison is 4.0 versus 3.75, giving a reported mean difference of 0.25. The low-intensity comparison is 3.25 versus 3.75, giving a reported mean difference of -0.5. Positive values indicate a higher mean in the exercise group than in control; negative values indicate a lower mean. Because the scale assigns higher scores to stronger muscle function, the sign describes the direction of the score difference, not its cause or clinical importance.

These are unadjusted comparisons of the posted summary statistics. They do not account for baseline scores or other participant characteristics. The registry record does not report a sponsor analysis for the primary outcome, so the recalculated comparisons should not be mistaken for an adjusted or prespecified model. The record also does not state whether a particular model was intended in the original analysis plan.

Why is variability relevant?

Participants in the same group can have different outcome scores. Standard deviations describe that spread, and greater spread generally makes the group mean less precisely estimated when sample size is held constant. The primary outcome standard deviations were 0.89, 0.87, and 1.14 in the high-intensity, low-intensity, and control groups. With relatively few observations contributing to each mean, estimates of both the group averages and their differences can be sensitive to the individual observations.

When data are more dispersed than a model assumes, uncertainty can be understated if the analysis does not accommodate that extra variability. This is a general statistical concern; the primary endpoint is a graded scale, and the registry record does not report a model checking or variance adjustment. A mean-based summary is easy to compare across groups, but it may not describe the full distribution of a bounded, discrete score.

How should the intervals and p-values be read?

An interval around a mean difference conveys a range of values compatible with the estimate under the method used. Narrower intervals indicate greater precision; wider intervals indicate less precision. For the primary comparisons, each reported interval covers zero and includes values on both sides of zero. That pattern indicates that the estimates do not pin down whether the exercise-group mean was higher or lower than the control mean. The confidence level and detailed interval method are not reported in the registry record.

A p-value describes how unusual data at least as inconsistent with a specified null hypothesis would be under the statistical assumptions used. It is not the probability that the null hypothesis is true, and it does not measure the size or importance of a difference. The posted primary p-values are unadjusted. The record does not report whether these comparisons were prespecified or how the wider set of outcomes and comparisons was handled.

Randomization supports a comparison of assigned groups, but the registry record does not report enough detail to evaluate sequence generation, concealment, adherence, or the analysis population. The observed outcome counts are smaller than the enrollment count, and the reason for missing primary assessments is stated, but the analysis method for missing observations is not. These limitations matter when interpreting results as causal effects.

What do the planning figures mean?

Sample-size illustrations use an assumed effect and variability to estimate how many participants would be needed for a chosen statistical design. The illustrations associated with this trial use fractions of the observed effect, a two-sided significance level of 0.05, equal allocation between the two arms, and a normal approximation. They are not the original design assumptions, which are not reported in the registry record. A smaller target effect requires more participants to distinguish it from random variation at a given power and significance level. These calculations do not establish that the original trial had a particular power or that its observed estimates are stable.

11. Confidence Intervals and Precision

Precision concerns how tightly the data locate a group difference. The primary high-intensity-versus-control estimate is 0.25, with a reported interval from -0.582 to 1.082. The low-intensity-versus-control estimate is -0.5, with a reported interval from -1.311 to 0.311. Both intervals extend across zero, so each allows for a range of possible differences in either direction. The registry record does not specify the confidence level or the method used to construct the intervals.

An interval is not a guarantee that the true difference lies within its limits, and it does not assign probabilities to individual values after the data are observed. In general, an interval produced by a statistical procedure reflects the values that are compatible with the estimate under that procedure and its assumptions. Wide intervals indicate limited precision. Here, the group means are based on small outcome counts, which contributes to uncertainty, though the registry record does not report a precision target or a design justification.

The primary intervals include differences that could represent higher or lower scores in an exercise group relative to control. The estimates therefore do not precisely establish the direction or magnitude of a between-group difference. The unadjusted p-values are consistent with this uncertainty, but neither an interval crossing zero nor a non-small p-value demonstrates that groups are equivalent.

The reported intervals are for each exercise group compared with control. They do not provide an interval for a direct high-intensity-versus-low-intensity comparison. The registry record also does not report an adjusted analysis or a confidence level. Those omissions limit how far the precision statements can be taken.

12. Planning a Similar Trial: Sample Size

This is a planning illustration, not a re-evaluation of the original trial. It asks: if a new study wanted to detect a difference like the one observed, or a smaller one, how large would it need to be? It is deliberately not “observed power” of the finished trial, which is not a meaningful quantity.

The planning figures are participants per arm for the continuous outcomes in these comparisons; they are not total event counts. They use a two-sided significance level of 0.05, equal allocation between the two arms, and a normal approximation. The assumed effect is set to 100%, 75%, or 50% of the observed effect. These are planning illustrations based on observed trial results, not the trial's original design assumptions, which are not reported in the registry record.

The 80% power column gives the estimated participants per arm for a design with an 80% chance of detecting the assumed effect under the stated statistical assumptions, if that effect is real. The 90% power column uses a higher chance of detection under those assumptions. Higher power generally requires more participants. When the assumed effect is smaller, it is harder to distinguish from random variation, so the required number of participants increases. For example, the primary comparison estimates give different planning figures when the assumed effect is reduced from 100% to 75% or 50% of the observed effect.

A curve relating sample size to effect size expresses the same planning relationship: smaller effects generally require larger groups to achieve the same target power. The figures should be treated as conditional illustrations, not as a recommendation for a future study; the original design parameters, including its assumptions about the effect and variability, are not reported in the registry record. These calculations are not observed power.

13. How the Sample Size Is Derived

Power is the probability that a study of a given size rejects the null hypothesis when a specific true effect exists. It depends on four things: the effect to detect, the variability of the outcome, the significance level (here a two-sided α of 0.05, so z_1−α/2 = 1.960) and the desired power (z_1−β = 0.842 for 80% and 1.282 for 90%).

Formula

n is the number of participants in each arm, Δ is the difference in means to detect and σ is the common standard deviation.

Worked calculation for this trial

1. Observed difference Δ = 0.250; pooled standard deviation σ = 1.029.
2. n = 2 × (1.96 + 0.842)² × 1.029² / 0.250² = 265.7, rounded up to 266 participants per arm for 80% power.

The smaller-effect rows in the table above repeat the same calculation with the effect multiplied by 0.75 and 0.5 (for ratios, applied to the logarithm of the ratio).

R code

alpha <- 0.05
z_a   <- qnorm(1 - alpha / 2)          # two-sided
delta <- 0.25                      # observed difference in means
sigma <- 1.0285588623571                     # pooled standard deviation
n_per_arm <- function(power, frac = 1) {
  ceiling(round(2 * (z_a + qnorm(power))^2 * sigma^2 / (delta * frac)^2, 6))
}
for (f in c(1, 0.75, 0.5))
  cat(sprintf("%3.0f%% of observed effect: n per arm = %s (80%% power), %s (90%% power)\n", 100 * f,
              format(n_per_arm(0.80, f), big.mark = ","), format(n_per_arm(0.90, f), big.mark = ",")))

# Check against R's built-in function (t-based, so very slightly larger)
cat("power.t.test:", round(power.t.test(delta = delta, sd = sigma, power = 0.80)$n, 1), "\n")

# Simulation: exact two-sample t-test using simulated means and variances
set.seed(4351750)
n    <- n_per_arm(0.80)
reps <- 20000
m_diff <- rnorm(reps, delta, sigma * sqrt(2 / n))             # difference in sample means
s2     <- sigma^2 * rchisq(reps, 2 * (n - 1)) / (2 * (n - 1))   # pooled sample variance
tstat  <- m_diff / sqrt(s2 * 2 / n)
cat(sprintf("Simulated power at n = %s per arm: %.3f (%d replicates)\n", format(n, big.mark = ","), mean(abs(tstat) > qt(0.975, 2 * (n - 1))), reps))

Output from running the code

100% of observed effect: n per arm = 266 (80% power), 356 (90% power)
 75% of observed effect: n per arm = 473 (80% power), 633 (90% power)
 50% of observed effect: n per arm = 1,063 (80% power), 1,423 (90% power)
power.t.test: 266.7 
Simulated power at n = 266 per arm: 0.799 (20000 replicates)

The simulation draws many sets of group means and variances at the planned sample size and counts how often the two-sample t-test rejects the null. It should land close to the target power; at very small required sample sizes it can fall below it, because the normal approximation is rough there.

14. Multiplicity, Missing Data and Analysis Populations

The registry record lists one primary outcome and several secondary outcomes, with comparisons between each exercise group and control. It does not report a statistical analysis plan, a hierarchy for testing outcomes, or an adjustment for multiple comparisons. When many outcomes or group comparisons are examined, the chance of at least one apparently unusual result can rise. This general issue makes unadjusted secondary p-values less conclusive than a single prespecified test interpreted under a clearly described plan.

The primary outcome description reports three missing assessments: one participant in each group declined digital palpation because of embarrassment. The group counts contributing to the primary results are 11 for high-intensity exercise, 12 for low-intensity exercise, and 12 for control. The registry record does not report an imputation method, a sensitivity analysis, or whether the missing observations were excluded under a complete-case approach. It also does not report whether the reason for missingness was considered in the analysis.

Outcome counts differ across the posted secondary results, and the registry record does not explain those differences. The intended analysis population, handling of deviations from assigned treatment, adherence, and follow-up completeness are not reported in the registry record. Consequently, it is not possible from the posted information to determine whether the estimates represent an intention-to-treat analysis or another analysis population.

The record also does not report baseline-adjusted comparisons, a formal model for the repeated or grouped measurements, or a prespecified approach to missing data. These are not assumptions that can be inferred from the randomized design. They remain important uncertainties when considering the strength and reproducibility of the reported comparisons.

15. 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 serious adverse event figures list zero affected participants in the high-intensity group, the low-intensity group, and the control group. The corresponding numbers at risk are 12, 13, and 13. The record lists zero deaths in each group and no serious adverse event terms.

These counts describe what was recorded for the groups and the reported safety observation. A count of zero does not establish that an event is impossible or that the interventions have no safety risks. The registry record does not provide further detail about how adverse events were collected, the duration of safety follow-up, or the criteria used to attribute an event to an intervention. The figures therefore offer a limited description of recorded serious events, not a comprehensive assessment of safety.

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

The posted results describe pelvic floor muscle function scores at 8 weeks among participants with available primary outcome data. The high-intensity group's mean score was 4.0, compared with 3.75 in control; the low-intensity group's mean was 3.25. On the modified Oxford grading scale, higher scores represent stronger muscle function. The unadjusted comparisons are imprecise, and their reported intervals include zero. The registry record therefore does not precisely establish the direction or size of a difference between either exercise group and control.

These findings are not evidence that the groups are equivalent. A result that does not clearly distinguish a difference from zero can arise because the true difference is small, because the data are variable, because the sample is limited, or through a combination of factors. The posted estimates cannot separate those explanations. Nor do the two comparisons directly test whether high-intensity exercise differs from low-intensity exercise.

The endpoint is a graded measure obtained by digital palpation, not a direct force measurement or a report of urinary symptoms. The study also listed symptom and quality-of-life outcomes, but their posted comparisons are unadjusted and have the same general limitations of imprecision and incomplete analysis detail. The available results do not establish how any score difference relates to a participant's experience or to outcomes beyond the measurement time.

The registry record documents randomization and the intervention groups, but key details about analysis populations, missing-data handling, and the original statistical plan are not reported. The results should therefore be understood as limited estimates from the posted outcome data, rather than a definitive assessment of the effect of exercise intensity. The record also does not support conclusions about longer-term outcomes or populations beyond those studied.

17. Why This Trial Matters Statistically

This trial illustrates why a randomized design and a numerical difference between means do not automatically produce a precise answer. The primary result is a score on a defined scale, and the group means are easy to compare, but the outcome counts are small and the reported intervals cover values on both sides of zero. Statistical interpretation depends on the estimated difference together with its uncertainty, not on the means alone.

The comparison structure also matters. Each exercise program is compared with pelvic floor muscle training alone, while the stated hypothesis concerns both improvement and a possible difference by intensity. Separate comparisons against control do not substitute for a direct high-intensity-versus-low-intensity analysis. Without that direct estimate and its uncertainty, the relative effect of the two exercise intensities remains unresolved in the posted results.

The record is also a useful example of the distinction between study planning and retrospective illustration. Sample-size calculations based on observed differences can show how assumptions about effect size influence planning, but they cannot recover the original design rationale. That rationale is not reported in the registry record. Likewise, a list of p-values does not reveal whether multiple testing, missing outcomes, or baseline differences were addressed in the original analysis.

For biostatisticians and clinical researchers, the record highlights the value of clear outcome definitions, transparent analysis populations, explicit missing-data methods, and prespecified comparisons. Those details help readers distinguish descriptive summaries from confirmatory inference and judge how much confidence to place in a result.

18. 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 primary outcome group counts are small, and one assessment is missing from each group because of participant embarrassment with digital palpation. The record does not describe an approach to handle these missing assessments or show how results might change under alternative assumptions about them. Since the endpoint depends on a physical assessment, the absence of masking may also be relevant to measurement, but the registry record does not describe assessor procedures or whether the assessor knew group assignment.

The posted endpoint is an absolute score at 8 weeks. Baseline scores and a change-from-baseline analysis are not included in the posted primary results, and the registry record does not report a baseline-adjusted comparison. The score is bounded and discrete, while the summaries and comparisons are based on group means. No information is reported about checking model assumptions or using methods suited to the scale.

The group comparisons are against control rather than directly between exercise intensities. The registry record does not report sponsor inferential analyses, a multiplicity strategy, the analysis population, adherence, or the handling of protocol deviations. Several listed outcomes do not have group results in the posted outcome data. These omissions restrict both the interpretability and completeness of the evidence available in the record.

Finally, the primary outcome is measured at 8 weeks, and the posted data do not establish longer-term patterns. The record does not report the original sample-size justification or statistical plan, so the intended precision and confirmatory status of these comparisons cannot be assessed.

19. Related Tutorials

20. Related Statistical Calculators

21. Sources

• ClinicalTrials.gov: Dose-response of Physical Exercise on Pelvic Floor Muscle Function in Postmenopausal Women With Urinary Incontinence — NCT04351750.
• Registry record last updated 2023-03-31; status last verified 2022-06.
• Results first posted 2023-03-31.
• 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.

22. Record Summary

NCT04351750 is a completed, randomized, parallel-group trial with no masking, sponsored by National Cheng Kung University. The registry record lists 47 participants enrolled and compares high-intensity general exercise plus pelvic floor muscle training, low-intensity general exercise plus pelvic floor muscle training, and pelvic floor muscle training alone.

The primary outcome is pelvic floor muscle function measured by digital palpation at 8 weeks. The posted means were 4.0 for high-intensity exercise, 3.25 for low-intensity exercise, and 3.75 for control. Unadjusted recalculated comparisons with control have intervals spanning zero. The registry record notes one missing primary assessment per group and does not report a sponsor inferential analysis, the original sample-size rationale, or the statistical plan.