Assessment of Efficacy of Low Intensity Resistance Training in Women at Risk for Symptomatic Knee Osteoarthritis: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Assessment of Efficacy of Low Intensity Resistance Training in Women at Risk for Symptomatic Knee Osteoarthritis (NCT01440972), a randomized na study. The primary outcome is Change in Isotonic Double Leg-press 1 Repetition Maximum Strength Scaled to Body Mass.

2. Clinical Question

3. Trial Design

The registry record describes a randomized, parallel-group trial with triple masking. The intervention contrast was low-intensity resistance training with partial blood flow restriction (PBFR) versus the same general type of training without PBFR. The trial was completed, with enrollment recorded as 45. The start and primary completion dates are listed as 2011-09 and 2011-11. The phase is listed as NA.

The intended population was women at risk for developing symptomatic knee osteoarthritis. The primary outcome was change in isotonic double leg-press one-repetition maximum strength scaled to body mass, assessed at four weeks. The registry summary also identifies isokinetic knee extensor strength as part of the primary hypothesis, while the posted outcome results identify scaled leg-press strength as the primary outcome measure. The registry record does not report a separate posted result for isokinetic strength as a primary outcome.

The registry’s primary outcome results give arm-level means and standard deviations for 21 participants in the exercise-without-PBFR group and 19 in the exercise-with-PBFR group. The secondary outcome results use those same arm-level participant counts. These posted outcome counts are distinct from the enrollment figure; the record does not explain the difference between enrollment and the numbers contributing to the outcome summaries.

The record does not report the randomization procedure, allocation concealment, the specific masking roles, adherence, participant flow, or the handling of withdrawals. It also does not report the original sample-size justification or detailed intervention procedures. Those omissions limit assessment of how the planned design was implemented, but do not alter the basic comparison described by the registry: exercise with PBFR versus exercise without PBFR.

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

Reasons for not completing this period:

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 Change in Isotonic Double Leg-press 1 Repetition Maximum Strength Scaled to Body Mass, measured over 4 weeks.

The primary endpoint is change in isotonic double leg-press one-repetition maximum strength, scaled to body mass, with measurement at four weeks. Its unit, kg per kg body mass, expresses the change in leg-press strength relative to body mass rather than as an unscaled load. The posted outcome is continuous and is summarized by a mean and standard deviation in each arm.

In general, a one-repetition maximum is the greatest resistance a participant can move through the exercise for one repetition under the test conditions. A leg-press measure is relevant to the trial’s stated focus on quadriceps and lower-limb strength. Scaling to body mass provides a relative measure, which can help interpret strength across people of differing body mass. These are general measurement considerations; the registry record does not report why this particular scale or test was selected.

The registry identifies this outcome as the primary measure and frames the main comparison as the change after four weeks with PBFR versus without PBFR. A between-group contrast is needed to distinguish change associated with the PBFR exercise program from change observed under the comparison exercise program. The registry record does not describe the measurement protocol, assessor training, reliability, or whether the analysis adjusted for baseline strength. Accordingly, the posted summaries support interpretation of the reported group means and their estimated difference, but they do not answer those protocol-specific questions.

7. Results Posted in the Registry

• Exercise With PBFR: mean 0.40 versus 0.20 on control; difference 0.20 (95% CI 0.01 to 0.39), standardized effect d = 0.67; z-test p = 0.035.

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.

Change in Quadriceps Muscle Volume by Magnetic Resonance Imaging

• 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:
  • Exercise With PBFR: mean 1.30 versus 0.01 on control; difference 1.29 (95% CI 0.81 to 1.77), standardized effect d = 1.69; z-test p = <0.001.
• Interpretation:
  • The 95% confidence interval excludes no difference, so the mean is statistically higher for Exercise With PBFR than for the control. This is an unadjusted, secondary comparison, so it is suggestive rather than confirmatory.

Change in Lower Limb Muscle Power by Double Leg-press at 40% 1 Repetition Maximum

• 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:
  • Exercise With PBFR: mean 0.62 versus 0.42 on control; difference 0.20 (95% CI 0.04 to 0.36), standardized effect d = 0.76; z-test p = 0.017.
• Interpretation:
  • The 95% confidence interval excludes no difference, so the mean is statistically higher for Exercise With PBFR than for the control. This is an unadjusted, secondary comparison, so it is suggestive rather than confirmatory.

Change in Knee Injury and Osteoarthritis Outcome Score Pain Subscale

• 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:
  • Exercise With PBFR: mean 2.00 versus 1.80 on control; difference 0.20 (95% CI -1.51 to 1.91), standardized effect d = 0.07; z-test p = 0.819.
• Interpretation:
  • The 95% confidence interval includes no difference, so these data do not show a statistically significant difference between Exercise With PBFR and the control. The interval gives the range of effects that remain compatible with the data.

The secondary outcomes cover several related but distinct domains: quadriceps muscle volume, lower-limb muscle power, knee pain, and isokinetic knee extensor strength. The posted results include arm summaries and comparisons for muscle volume, leg-press power, and knee-pain score; the registry’s secondary outcome list also names isokinetic strength, but a corresponding result is not included among the posted secondary summaries. This mix provides context around the primary strength measure, but it does not amount to a single unified measure of benefit or harm.

The overall pattern is not uniform across all outcomes. The posted muscle-volume and leg-press power comparisons have positive estimated mean differences, while the pain-score comparison has an interval that includes values on either side of zero. The outcomes use different units and scales, so their numerical estimates cannot be compared directly as if they measured the same quantity. Nor should a pattern across these outcomes be treated as proof that changes in one domain caused changes in another; the registry does not report such an analysis.

These outcomes relate to the primary result by offering additional measurements of muscle size, performance, and symptoms during the same four-week period. They may help characterize the range of observed changes, but the primary endpoint remains the designated outcome for the main comparison. The registry record does not report a prespecified hierarchy among the secondary outcomes or a plan to combine them.

The secondary comparisons are unadjusted, and the registry lists no reported secondary analyses. In general, when several outcomes are tested, the chance of at least one apparently notable result arising by chance increases unless the analysis accounts for multiplicity. This does not mean a particular secondary estimate is false; it means its evidential weight is reduced when it is considered alongside multiple outcomes without a reported adjustment or prespecified interpretation. The secondary findings are best read as exploratory context, with attention to their estimates, uncertainty, scales, and reporting limitations rather than as independent confirmation of the primary result.

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

• Change in Quadriceps Muscle Volume by Magnetic Resonance Imaging
• Change in Lower Limb Muscle Power by Double Leg-press at 40% 1 Repetition Maximum
• Change in Knee Injury and Osteoarthritis Outcome Score Pain Subscale
• Change in Isokinetic Knee Extensor Strength

9. Statistical Interpretation

10. Statistical Methods Explained

The trial used a randomized, parallel-group comparison. Randomization is intended, in general, to make assigned groups comparable on average at the start of a trial, including for factors that were not measured. It does not guarantee that groups will be identical in a particular small study. The registry identifies the allocation as randomized and the model as parallel, but the method used to generate the allocation sequence and conceal assignments is not reported in the registry record.

What does a mean change describe?

The primary outcome is continuous, and the registry summarizes each arm by its mean change and standard deviation. In general, a mean is the arithmetic average of the measured changes in a group. A standard deviation describes how dispersed individual measurements are around that group average. It is not a confidence interval and does not directly describe the precision of the estimated difference between groups.

For the primary endpoint, the posted mean changes were 0.2 kg per kg body mass without PBFR and 0.4 kg per kg body mass with PBFR, with a standard deviation of 0.3 in each arm. The posted comparison estimates a mean difference of 0.2. This is a between-arm contrast in average change, not the change of an individual participant. The registry record does not state whether the reported analysis adjusted for baseline measurements or other covariates.

What does the confidence interval add?

In general, a confidence interval expresses the uncertainty of an estimate under the assumptions of the statistical procedure. A narrower interval indicates greater precision, while a wider interval indicates less precision. An interval spanning zero is compatible with a range of effects that includes no between-group difference; an interval entirely on one side of zero excludes zero under that interval procedure. The primary interval has positive lower and upper limits, but still spans a range of possible difference sizes. Its width matters: a result that is separated from zero can nevertheless leave uncertainty about the magnitude.

A confidence interval does not assign a probability that the true effect lies in the particular calculated interval. Its usual interpretation concerns the long-run behavior of the method across repeated studies under its assumptions. Those assumptions include the statistical model and the way observations are sampled and measured. The registry record does not supply enough analysis detail to assess every assumption or reconstruct a sponsor-reported model.

How should the p-value be read?

In general, a p-value measures how unusual data at least as incompatible with a specified null hypothesis would be, if that null and the statistical model were correct. It is not the probability that the null hypothesis is true, and it does not measure the probability that a result is due to chance in a general sense. The primary unadjusted p-value is 0.035. Its interpretation belongs alongside the estimated difference and confidence interval, rather than serving as a measure of effect size or clinical importance.

The registry does not report adjustment of the primary p-value for multiple outcomes or other testing. The secondary outcomes each have their own comparisons, and no reported analysis section is listed for them. An unadjusted p-value is calculated without accounting for the number of outcomes or hypotheses examined. When many comparisons are considered, chance alone makes one or more small p-values more likely in general. That is why unadjusted secondary findings are usually treated as less definitive than a clearly specified primary result.

Why can variability matter?

In general, the standard deviation reflects variation among participant-level results. A larger standard deviation relative to the difference of interest makes a group contrast harder to estimate precisely with a given amount of information. Greater variability can arise from genuine differences among participants, measurement variability, or other sources. The registry reports standard deviations for the primary and secondary continuous outcomes, but does not describe the sources of variation or the measurement reliability.

Over-dispersion is a general concern for some statistical models when observed variability exceeds what the model assumes. In that situation, standard errors can be too small if the extra variability is ignored, and confidence intervals may be too narrow. The posted outcomes are described as continuous mean measures, and the record does not report a model-based dispersion assessment. There is no basis in the registry record to claim that over-dispersion was detected or to say how it was handled.

What is and is not documented about the analysis?

The registry provides outcome summaries and pairwise comparison estimates, but it does not report a detailed statistical analysis plan, analysis population definition, handling of missing observations, or any adjustment for baseline values. The number of reported analyses is listed as zero, and no secondary reported analyses are listed. This means the posted summaries should not be mistaken for a complete account of the trial’s statistical methods. In general, prespecification helps clarify which outcome and analysis were intended to carry the primary evidential weight, while transparent reporting of exclusions and missing data helps readers assess possible bias.

The registry’s planning illustrations use a two-sided significance level of 0.05, equal allocation between arms, and a normal approximation, with the effect to detect expressed as a stated fraction of the observed effect. These are assumptions for the displayed planning exercise, not documented assumptions for the original trial design. The registry record does not report the original sample-size justification. Planning numbers derived from an observed result are not a substitute for prospective design assumptions.

11. Confidence Intervals and Precision

The primary estimated mean difference is 0.2 kg per kg body mass, with a reported confidence interval whose lower and upper limits are both positive. The interval is the most direct indication of the precision of the estimated contrast in the posted results. Its positive limits indicate that the interval does not include zero under the reported procedure, while its span shows that the precise size of the difference remains uncertain. The unadjusted p-value of 0.035 is consistent with that interval-based description, but does not make the estimate exact.

The arm-level standard deviations are 0.3 in both groups, and the comparison is based on 21 participants without PBFR and 19 with PBFR. In general, limited information and participant-to-participant variability can leave a broad range of effect sizes compatible with the data. The standard deviation describes dispersion among individual changes; the confidence interval reflects uncertainty in the between-group estimate. These answer different questions and should not be conflated.

The results do not report a clinically meaningful threshold for the scaled leg-press outcome. Consequently, statistical evidence that an interval excludes zero cannot establish whether every value in that interval would represent a practically important difference. Interpretation also depends on how the measure was collected and on the population to which the result is applied; the registry record does not provide detailed measurement procedures or participant characteristics.

For secondary outcomes, precision differs across comparisons. The knee-pain interval includes both negative and positive values, while the intervals reported for the other secondary comparisons have positive limits. These comparisons should be considered in the context of their outcome-specific scales and the lack of reported multiplicity adjustment. An interval that includes zero does not prove that the groups are equivalent, just as an interval excluding zero does not by itself demonstrate clinical importance. The registry record does not report an equivalence margin or a threshold for meaningful change.

All intervals describe uncertainty conditional on the analysis and data available for the outcome. Since the record does not report missing-data handling, analysis populations, or an adjusted model, the precision displayed cannot resolve uncertainty about those methodological choices.

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 this continuous-outcome comparison, not total events. The stated planning assumptions are a two-sided significance level of 0.05, equal allocation between the two arms, and a normal approximation. The effect to detect is set at the stated fraction of the observed effect. The original trial’s own sample-size assumptions and justification are not reported in the registry record.

The 80% power column gives the illustrative number of participants per arm that the planning calculation associates with an 80% chance of detecting the selected effect under its assumptions, if that effect and model are correct. The 90% power column expresses the corresponding planning target for a 90% chance. These are design probabilities under assumed conditions, not guarantees about what a study will find. The figures change with the assumed effect: smaller effects require more participants to detect at the same power and significance level. The planning rows therefore illustrate how sample-size requirements depend on the effect size chosen for planning.

The effect fractions are based on the observed effect in this trial. An observed effect from a small study can be an unstable basis for planning a later study, so the alternative fractions are useful as sensitivity illustrations rather than definitive targets. The original enrollment of 45 does not establish that the study was designed around these later calculations; the registry record does not report that connection.

This is not observed power. It is a planning illustration that applies stated assumptions to an effect-size scenario. It should not be used to infer that the completed trial had a particular probability of detecting its result after the data were collected. In general, interpretation of the completed trial should focus on the estimate and its precision rather than retrospective power calculations.

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 = 0.200; pooled standard deviation σ = 0.300.
2. n = 2 × (1.96 + 0.842)² × 0.300² / 0.200² = 35.3, rounded up to 36 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 <- 0.2                      # observed difference in means
sigma <- 0.3                     # 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(1440972)
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 = 36 (80% power), 48 (90% power)
 75% of observed effect: n per arm = 63 (80% power), 85 (90% power)
 50% of observed effect: n per arm = 142 (80% power), 190 (90% power)
power.t.test: 36.3 
Simulated power at n = 36 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 identifies a primary outcome and lists several secondary outcomes, but does not report a statistical plan describing how multiplicity was handled. Multiplicity arises when several hypotheses or outcomes are examined. In general, if every comparison is interpreted using an unadjusted significance threshold, the chance of at least one small p-value across the full set of tests can be greater than for a single prespecified test. Adjustment procedures or a clearly specified hierarchy can help manage that issue, but no such procedure is reported in the registry record.

The primary comparison has an unadjusted p-value of 0.035. The secondary comparisons also have unadjusted p-values, but there is no reported analysis section for them and no stated correction across outcomes. Accordingly, a secondary p-value should not be treated as having the same confirmatory status as a primary test within a prespecified testing strategy. The record does not establish whether any analysis plan outside the registry addressed this issue.

Missing-data methods are not reported in the registry record. The outcome summaries list 21 participants in the exercise-without-PBFR arm and 19 in the exercise-with-PBFR arm, while enrollment is recorded as 45. The record does not explain whether all randomized participants contributed to each outcome, why the outcome counts differ from enrollment, how missing measurements were handled, or whether participants were analyzed according to assigned group. It would be inappropriate to infer a particular reason for the counts or a particular missing-data method.

The analysis population is also not reported in the registry record. In general, an intention-to-treat analysis includes participants according to randomized assignment, while other analysis populations may exclude participants for specified reasons. Without a stated population definition and participant flow, readers cannot determine which approach generated the posted summaries. Baseline adjustment, handling of protocol deviations, and sensitivity analyses are likewise not reported. These omissions do not invalidate the descriptive results, but they limit assessment of how robust the estimated comparisons are to choices about missing observations and analysis membership.

15. 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.

The registry reports zero serious adverse events among 24 participants at risk in the exercise-without-PBFR group and zero among 21 participants at risk in the exercise-with-PBFR group. It also reports zero other adverse events among the same respective at-risk group sizes. These entries describe the recorded event counts over the safety reporting period; they do not establish that no event could occur or that the two approaches have identical safety profiles.

In general, event counts need to be interpreted together with the number of people observed, the duration and completeness of monitoring, and the way events were defined and collected. The registry record does not provide detailed event definitions, monitoring procedures, or a fuller account of safety ascertainment. Death counts are not reported in the registry record.

Zero recorded events in these groups should therefore be read as a limited observation from this trial, not as evidence that uncommon events are absent. The small at-risk groups also make it difficult to characterize rare harms. The registry record does not report a comparative statistical analysis of adverse events.

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

The primary result describes an estimated difference in average change in scaled leg-press strength after four weeks between women assigned to low-intensity resistance training with PBFR and women assigned to the exercise program without PBFR. The estimated mean difference is 0.2 kg per kg body mass. The confidence interval has positive limits, and the unadjusted p-value is 0.035. These statistics describe the observed comparison and its uncertainty under the reported analysis; they are not a guarantee that the same estimate would occur in another sample.

The result does not establish the clinical importance of the difference. The registry does not report a threshold for a meaningful change in this measure, nor does it provide patient-level interpretation of the scaled value. Statistical compatibility with a nonzero difference is not equivalent to proof that the difference matters to participants. It also does not establish that the result will persist beyond the four-week assessment or apply to other populations, exercise programs, or settings.

The comparator is exercise without PBFR, not absence of exercise. Therefore, the result addresses the added contrast between the two exercise approaches as described in the record. It does not estimate the effect of exercise relative to no intervention. The trial summary describes women at risk for symptomatic knee osteoarthritis, but further eligibility and participant characteristics are not reported, limiting assessment of how broadly the findings might apply.

The secondary outcomes add observations on muscle volume, muscle power, and knee pain, but they do not resolve these limitations. Their interpretation is constrained by multiple unadjusted comparisons and the absence of a reported secondary analysis plan. The registry also does not report a result for every secondary outcome listed. Likewise, the absence of recorded adverse events in the listed groups cannot establish absence of risk.

In general, a trial result is most informative when interpreted with the design, outcome definition, uncertainty interval, missing-data procedures, and analysis plan. Several of those details are not reported in the registry record. The posted evidence should consequently be understood as a short-term comparison with an estimated primary difference, rather than a definitive account of clinical benefit, long-term outcomes, safety, or mechanism.

17. Why This Trial Matters Statistically

This trial is statistically interesting because it contrasts two active exercise approaches rather than exercise with no exercise. That design makes the primary estimate relevant to the incremental question of adding partial blood flow restriction to low-intensity resistance training, as defined in the registry. It also illustrates why the comparator must be kept clear when interpreting an estimated difference: the result is not a general comparison of exercise with inactivity.

The primary outcome is continuous, and the record reports means, standard deviations, an estimated mean difference, a confidence interval, and an unadjusted p-value. These complementary summaries show different aspects of the evidence. The mean difference describes the estimated contrast, the interval describes uncertainty in its size, and the p-value describes compatibility with a null comparison under statistical assumptions. None alone conveys clinical importance, and the registry does not report a threshold for interpreting the endpoint in clinically meaningful terms.

The outcome set also shows how a trial may examine multiple domains that are related but not interchangeable. Strength, muscle volume, power, and pain each represent different constructs and use different measurement scales. A consistent interpretation requires attention to the intended primary endpoint, the additional outcomes, and the possibility of chance findings when several comparisons are considered. The registry does not report a multiplicity strategy, which makes that distinction especially important.

Finally, the planning illustrations demonstrate how assumptions about effect size influence required sample size. Their estimates use the observed effect and specified planning assumptions, whereas the original design justification is not reported. Keeping those two uses separate is important: retrospective planning figures can illustrate design sensitivity, but they do not reveal what investigators anticipated when the trial was designed or how likely the completed trial was to detect its 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 registry record leaves important details about trial conduct and analysis unspecified. It does not report the randomization method, allocation concealment, the roles included in triple masking, or the detailed exercise and PBFR procedures. It also does not provide participant characteristics beyond the intended population of women at risk for symptomatic knee osteoarthritis. These omissions limit assessment of implementation and applicability.

The primary and secondary outcome summaries report participant counts that are smaller than the enrollment figure, but the record does not explain participant flow or the difference. Missing-data methods and analysis populations are not reported. The record also does not say whether the primary comparison was adjusted for baseline outcome values, how protocol deviations were treated, or whether sensitivity analyses were performed. These uncertainties limit the ability to assess possible bias from attrition or analytic choices.

The primary assessment is at four weeks, and the registry does not report longer-term follow-up. The result therefore cannot describe durability from these posted data. No threshold for clinically meaningful change is reported for the primary measure or the secondary outcomes. The registry also does not give detailed measurement procedures or reliability information.

Several secondary outcomes are listed, while the registry provides no reported secondary analyses and no multiplicity procedure. This makes secondary comparisons more exploratory. The listed isokinetic knee extensor strength outcome does not have a corresponding posted secondary result in the record. Safety reporting gives zero serious and zero other adverse events for the reported groups, but does not describe event definitions or monitoring in detail, and death counts are not reported in the registry record.

These limitations concern reporting and the scope of the available results. They do not determine whether an unreported method was or was not used; they mean that it cannot be assessed from the registry record.

19. Related Tutorials

20. Related Statistical Calculators

21. Sources

• ClinicalTrials.gov: Assessment of Efficacy of Low Intensity Resistance Training in Women at Risk for Symptomatic Knee Osteoarthritis — NCT01440972.
• Registry record last updated 2016-12-05; status last verified 2016-10.
• Results first posted 2015-07-30.
• 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

The University of Iowa registry record describes a completed randomized, triple-masked, parallel-group trial of low-intensity resistance training with versus without partial blood flow restriction in women at risk for symptomatic knee osteoarthritis. Enrollment is recorded as 45, with the trial starting in 2011-09 and primary completion in 2011-11.

The primary outcome was four-week change in isotonic double leg-press one-repetition maximum strength scaled to body mass. The posted mean changes were 0.4 with PBFR and 0.2 without PBFR, with an estimated mean difference of 0.2 and an unadjusted p-value of 0.035. Secondary results cover muscle volume, leg-press power, and pain; an isokinetic strength outcome is listed but has no corresponding posted secondary result.

The registry reports zero serious and zero other adverse events in the groups at risk. Detailed analysis methods, missing-data handling, multiplicity procedures, and the original sample-size justification are not reported in the registry record.