This page provides an independent statistical analysis and educational interpretation of publicly reported results. ClinicalTrials.gov provides the official trial registry record. Numerical trial results on this page are restricted to the results posted in the ClinicalTrials.gov record; calculations added by Clinical Biostats are labelled as such.
1. Trial at a Glance
This page covers the registry results for The Effect of Various Strength Training Protocols in ACL Reconstructed Participants (NCT03364647), a randomized na study. The primary outcome is Measure Change in Isometric Peak Torque Quadriceps Strength.
| Feature | Registry value |
|---|---|
| ClinicalTrials.gov identifier | NCT03364647 |
| Phase | NA |
| Condition | Anterior Cruciate Ligament (ACL) Tear, Physical Therapy |
| Allocation | Randomized |
| Design model | Parallel |
| Masking | Triple |
| Enrollment | 55 |
| Arms in the primary outcome | n/a |
| Lead sponsor | Brian W. Noehren |
| Results posted | Yes |
2. Clinical Question
Population
Participants with an ACL tear who will or have had ACL reconstruction, as described in the study summary. The registry record reports an enrollment of 55, but does not report detailed eligibility criteria or the characteristics of participants included in an outcome analysis.
Intervention
Blood flow restriction training alongside standard of care. The summary describes physical therapy sessions during recovery, while the arm description identifies the combination of blood flow restriction training and standard care.
Comparator
Standard of care plus a sham version of blood flow restriction training. The intervention listing gives a shorter label for this arm; the arm description specifies the sham component.
Primary question
How does quadriceps isometric peak torque strength change from baseline to post-surgery, up to 5 months, and are there between-group or within-patient differences over time?
The question is about the measured course of quadriceps strength under two rehabilitation approaches, rather than a single post-treatment value alone. The registry description says the primary analysis may compare observations over multiple time points, with interest in differences between groups and changes within patients. It does not report a numerical group contrast, an estimate of change, or a confidence interval for the primary outcome. Consequently, the registry record does not establish the size or precision of any difference in strength.
3. Trial Design
This is a randomized, parallel-group trial with triple masking recorded in the registry. Its phase is recorded as NA. The study status is completed, and the registry reports enrollment of 55. The listed study dates are 2017-08-21 for the start and 2023-10-06 for primary completion. The sponsor is Brian W. Noehren.
The two groups are described as blood flow restriction training with standard care, and standard care plus sham blood flow restriction training. The intervention listing labels the second arm as standard of care, while its fuller arm description identifies the sham procedure. This difference in labeling is worth keeping in mind when interpreting the arm descriptions. The record does not report additional details about how randomization was generated, how allocation was concealed, or how masking was implemented.
The study summary describes training sessions 3 days a week for approximately 4 weeks before surgery and up to 24 weeks after surgery. Physical therapy visits are described as lasting 60-120 minutes, depending on recovery stage and activities. The summary also describes four additional study visits over a 7 month period, including assessments of knee and thigh muscle conditions, strength, walking mechanics, MRI, and muscle biopsy. These are descriptions of the intended study schedule; the registry record does not report each participant’s actual attendance or completed assessments.
The primary outcome is change in isometric peak torque quadriceps strength, assessed at baseline and post-surgery, up to 5 months. Other listed outcomes concern quadriceps muscle morphology and knee biomechanics. The record lists eight outcome measures, but reports zero analysis records. The number of participants included in the primary outcome analysis, participant flow by arm, and any exclusions from analysis are not reported in the registry record.
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: 647 participants were assessed for eligibility. Of those, 592 participants were excluded due to not meeting inclusion criteria or declining to participate. 55 participants were randomized of which 26 received the allocated intervention (BFRT) and 26 received the SHAM intervention. 3 participants withdrew after being randomized but before receiving the intervention.
Overall Study
| Stage | Arm A - Blood Flow Restriction Training | Arm B - Standard of Care Plus Sham |
|---|---|---|
| STARTED | 26 | 26 |
| COMPLETED | 23 | 25 |
| NOT COMPLETED | 3 | 1 |
Reasons for not completing this period:
| Reason | Arm A - Blood Flow Restriction Training | Arm B - Standard of Care Plus Sham |
|---|---|---|
| Withdrawal by Subject | 3 | 1 |
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.
| Characteristic | Unit | Arm A - Blood Flow Restriction Training | Arm B - Standard of Care Plus Sham | Total |
|---|---|---|---|---|
| Participants analysed | 26 | 26 | 52 | |
| Age, Continuous | years | 20.8 (SD 6.0) | 21.2 (SD 5.3) | 21.0 (SD 5.7) |
| Sex: Female, Male: Female | Participants | 11 | 11 | 22 |
| Sex: Female, Male: Male | Participants | 15 | 15 | 30 |
| Race and Ethnicity Not Collected | Participants | — | — | 0 |
| Region of Enrollment: United States | participants | 26 | 26 | 52 |
| Body Mass Index | kg/m2 | 25.3 (SD 4.2) | 25.7 (SD 4.4) | 25.4 (SD 4.5) |
| Time since injury | Days | 20.2 (SD 16.5) | 24.3 (SD 16.7) | 22.3 (SD 16.9) |
| Graft Type: Patellar | Participants | 24 | 24 | 48 |
| Graft Type: Hamstring | Participants | 1 | 2 | 3 |
| Graft Type: Unknown (lost to follow up before surgery) | Participants | 1 | 0 | 1 |
| Meniscal Injury: Lateral | Participants | 1 | 4 | 5 |
| Meniscal Injury: Medial | Participants | 7 | 6 | 13 |
| Meniscal Injury: Both | Participants | 16 | 14 | 30 |
| Meniscal Injury: None | Participants | 1 | 2 | 3 |
| Meniscal Injury: Unknown (lost to follow up before surgery) | Participants | 1 | 0 | 1 |
| Weight Bearing Status After Surgery: Weight Bearing as Tolerated | Participants | 23 | 25 | 48 |
| Weight Bearing Status After Surgery: Non-weight Bearing | Participants | 2 | 1 | 3 |
| Weight Bearing Status After Surgery: Unknown (lost to follow up before surgery) | Participants | 1 | 0 | 1 |
6. Primary Endpoint
The registry lists the primary outcome as Measure Change in Isometric Peak Torque Quadriceps Strength, measured over Baseline, and post-surgery (up to 5 months).
| Element | Registry entry |
|---|---|
| Result type | Mean |
| Measure of spread | Standard Deviation |
| Unit | Nm/Kg |
| Endpoint classification | Continuous Endpoint |
The primary endpoint is change in isometric peak torque quadriceps strength, measured in Nm/Kg. The registry states that strength was assessed with a Biodex Multi-Joint System 4 Isokinetic Dynamometer. Measurements are specified at baseline and post-surgery, up to 5 months. The description allows for comparison across multiple time points and identifies both between-group differences and within-patient differences as areas of interest.
In general, peak torque describes the maximum rotational force produced during a measured movement. Expressing the measure in Nm/Kg scales torque to body mass, making the recorded quantity relative to participant size. Isometric testing measures force during a contraction without the joint moving through a range of motion. These concepts explain what the endpoint is intended to quantify; they do not establish that the measure changed in this trial.
Strength is relevant to the study’s stated focus on rehabilitation and quadriceps function after ACL reconstruction. Repeated measurement can describe whether strength changes over time, while comparing groups can describe whether their measured courses differ. The record does not report the observed endpoint values, the scale or direction of any group contrast, or an estimate of change. The endpoint’s clinical interpretation therefore cannot be determined from the registry record alone.
7. Why No Re-analysis Is Shown
8. Statistical Interpretation
The registry record identifies a randomized comparison of blood flow restriction training plus standard care against standard care plus sham training. It gives the planned primary measure and assessment period, but does not report a statistical result for quadriceps strength. There is no posted group estimate, change estimate, confidence interval, or p-value for the primary endpoint in the record summarized by the available trial information. The direction, magnitude, and precision of any difference are therefore not reported in the registry record.
The record lists eight outcome measures and zero analysis records. It also indicates that the primary outcome has several categories or time points and was not reduced to one comparison. This means there is no single posted primary comparison to interpret as a treatment contrast. The outcome description allows for comparisons over multiple time points, but the actual model, contrast definitions, and results are not reported in the registry record.
In general, an estimate describes the size and direction of a measured difference, while a confidence interval describes the range of values compatible with the data and the analysis assumptions. Without either an estimate or its interval, the precision of the comparison cannot be assessed. A p-value alone would not show the size of an effect, but no p-value is reported for the primary outcome either. No conclusion about the observed difference between groups can be drawn from the enrollment, design, or endpoint description alone.
The sample-size assumptions describe planning illustrations based on a stated fraction of an observed effect, with a two-sided significance level of 0.05, equal allocation, and a normal approximation. These are planning calculations, not observed power and not evidence that a difference was detected. The actual trial’s sample-size justification is not reported in the registry record. The numerical planning illustrations and the effect estimate from which they are based are also not reported in the registry record information available for this interpretation.
The registry’s completion status and enrollment count describe the conduct and scale of the study, not its outcome. Likewise, the presence of a randomized design does not replace reporting of the analyzed data or methods. Participant counts for the primary analysis, missing outcome data, and the handling of repeated observations are not reported in the registry record. The strength question therefore remains statistically unresolved in the posted record, rather than answered in either direction.
9. Statistical Methods Explained
The registry describes a continuous primary measure summarized as a mean with standard deviation. It identifies repeated measurement at baseline and post-surgery, up to 5 months, and notes interest in both between-group and within-patient differences. It does not report the statistical model or a numerical analysis result for this endpoint. The explanations below describe general statistical ideas relevant to this kind of design, not methods confirmed as used in this trial.
What does a mean and standard deviation convey?
In general, a mean describes the center of a set of measurements. A standard deviation describes how spread out individual measurements are around that mean. Together, they can characterize outcome values in a group, but they do not by themselves quantify the uncertainty in a comparison between groups. That uncertainty depends on factors including the number of analyzed participants, the variability of the measurements, and the analysis method. The registry record does not report primary outcome means or standard deviations.
For repeated measurements, a mean at one assessment time does not describe the full course of change. A comparison of changes can account for the fact that measurements from the same participant are related. In general, repeated-measures analyses model that relationship rather than treating every observation as independent. The registry description mentions possible comparisons across multiple time points, but the particular approach to repeated observations is not reported in the registry record.
What is the distinction between a group contrast and within-patient change?
In general, a between-group contrast compares outcomes between participants assigned to different groups. A within-patient change compares measurements from the same participant across time. These answer related but distinct questions. A group contrast in change can ask whether the average course differs between groups, while a within-patient change describes how measurements shifted over time in a group or individual. The registry expresses interest in both types of differences, but it does not specify the exact estimand or contrast used for the primary analysis.
Randomization is intended, in general, to make treatment groups comparable at assignment, but it does not guarantee that every characteristic will be balanced in a particular trial. Nor does randomization itself specify how outcomes are analyzed. The registry records randomized allocation and a parallel model, but the sequence-generation method, concealment details, analysis population, and statistical model are not reported in the registry record. The recorded triple masking likewise does not disclose which study roles were masked or how masking was maintained.
Why do confidence intervals matter?
In general, a confidence interval presents uncertainty around an estimated effect. A narrower interval indicates greater precision under the assumptions of the analysis, while a wider interval indicates less precision. The interval also helps readers assess which effect sizes are compatible with the observed data. A p-value does not replace the estimate or interval: it addresses compatibility with a specified null hypothesis under a statistical model, not the magnitude or practical importance of an effect. No primary-outcome estimate, confidence interval, or p-value is reported in the registry record.
For this continuous endpoint, an analysis could report group means, changes, a contrast between changes, and uncertainty around that contrast. Those examples are general possibilities, not a statement of what the investigators used. The registry record does not report whether the primary comparison was adjusted for baseline strength or other variables, which time points were included in a model, or how the results were parameterized. The absence of those details prevents assessment of the analysis assumptions and the exact meaning of a hypothetical contrast.
What do the planning illustrations represent?
The stated planning assumptions describe illustrations using a two-sided significance level of 0.05, equal allocation between arms, and a normal approximation. They describe the effect to detect as a stated fraction of an observed effect. In general, such calculations estimate how many participants per arm would be needed to detect a specified effect under chosen assumptions. They are planning illustrations and should not be read as observed power for the completed trial. The numerical planning values and the observed effect used as their basis are not reported in the registry record information. The trial’s own sample-size justification is not reported in the registry record.
In general, planning calculations depend on assumptions about the effect size, variability, allocation, significance level, and desired power. If assumptions differ from the eventual data or analysis, the calculation does not guarantee a particular result. A sample-size illustration also cannot substitute for a confidence interval around the trial’s actual estimate. The record does not report an interim analysis plan, a stopping rule, or any adjustment for multiple comparisons.
How should multiple time points be considered?
In general, analyzing several time points and several outcomes creates choices about which contrasts to emphasize. If many comparisons are tested, the chance of at least one apparently notable result can increase unless the analysis accounts for multiplicity or interprets results accordingly. Repeated observations also require attention to within-person correlation. The registry identifies multiple time points for the primary measure and lists additional outcomes, but the analysis strategy for these features is not reported in the registry record. No inferential claim about a particular time point or outcome can be reconstructed from the endpoint descriptions alone.
10. Multiplicity, Missing Data and Analysis Populations
The registry lists eight outcome measures, including the primary quadriceps strength outcome and additional measures concerning quadriceps morphology and knee biomechanics. It describes primary strength observations at baseline and post-surgery, up to 5 months, and says the primary analysis may compare observations across multiple time points. However, the record does not identify a single primary time-point contrast or give a hierarchy among the secondary outcomes. A multiplicity adjustment or strategy for interpreting multiple comparisons is not reported in the registry record.
In general, testing multiple outcomes or time-point contrasts creates more opportunities for chance findings. A prespecified hierarchy, adjustment, or clearly qualified interpretation can help readers understand the implications. None of those approaches should be assumed for this trial without a registry report of the analysis plan. No interim analysis plan or stopping-rule details are reported in the registry record.
Missing outcome data are also important for a repeated-measures strength endpoint. The registry record does not report the amount or pattern of missingness, reasons for missing assessments, or how missing values were handled. It does not identify whether the primary analysis followed an intention-to-treat principle, used another analysis population, or included only participants with specified measurements. The analysis denominator for the primary endpoint is not reported in the registry record.
These omissions limit interpretation independently of whether a statistical test was significant. Without analysis-population definitions and missing-data methods, readers cannot determine how the analyzed participants relate to the randomized groups or assess the assumptions underlying the reported estimate. In this case, the primary outcome analysis itself is not reported in the registry record.
11. Safety Results
The registry reports serious adverse events as affected participants divided by participants at risk.
| Arm | Participants with serious adverse events | Participants at risk | Percentage |
|---|---|---|---|
| Arm A - Blood Flow Restriction Training | 1 | 23 | 4.3% |
| Arm B - Standard of Care Plus Sham | 0 | 25 | 0.0% |
Deaths
| Arm | Deaths (participants affected of at risk) |
|---|---|
| Arm A - Blood Flow Restriction Training | 0 of 23 |
| Arm B - Standard of Care Plus Sham | 0 of 25 |
Other (non-serious) adverse events
Participants with at least one non-serious event at or above the registry's 0% reporting threshold.
| Arm | Participants affected of at risk |
|---|---|
| Arm A - Blood Flow Restriction Training | 0 of 23 |
| Arm B - Standard of Care Plus Sham | 0 of 25 |
Most frequent serious adverse event terms
| Event term | Organ system | Arm A - Blood Flow Restriction Training | Arm B - Standard of Care Plus Sham |
|---|---|---|---|
| Patellar Fracture | Musculoskeletal and connective tissue disorders | 1 of 23 | 0 of 25 |
Serious events with the highest arm-level rate: patellar fracture (4.3%).
The safety record reports serious adverse events among 23 participants at risk in the blood flow restriction training arm and among 25 participants at risk in the standard of care plus sham arm. One serious adverse event affected a participant in the blood flow restriction training arm; zero affected participants are reported in the comparator arm. Other adverse events affected zero participants in either arm, and deaths are reported as 0 in both arms. The listed serious adverse event term is Patellar Fracture, with 4.3% shown in the registry.
These are descriptive safety counts. In general, adverse-event figures depend on how events are defined, collected, and attributed, and they do not by themselves establish a causal relationship to an intervention. The registry record does not report event timing, event narratives, severity beyond the serious classification, or an assessment of relatedness. The denominator underlying the listed 4.3% is not reported in the registry record. The arm counts should not be treated as a comparative safety estimate without an analysis that accounts for the study design and the available exposure information.
12. What the Result Does, and Does Not, Mean
The registry record establishes that a randomized, parallel-group study was completed, with 55 participants enrolled, and that its central stated question concerned quadriceps strength during rehabilitation associated with ACL reconstruction. It describes a comparison between blood flow restriction training plus standard care and standard care plus sham training. It also identifies the primary strength measure, its units, assessment method, and planned period of observation.
Those details do not provide an answer about the observed strength comparison. The registry record does not report an analyzed group difference, a change estimate, a confidence interval, or a p-value for the primary endpoint. It therefore does not show how large or precise a difference was, whether either group changed over time, or whether the groups’ measured trajectories differed. No conclusion about the study’s primary statistical result can be drawn from the design description alone.
In general, a nonsignificant result would not prove that groups are equivalent, and a statistically significant result would not on its own establish that a difference is important. Interpreting either kind of finding requires estimates, uncertainty, outcome context, and the analysis population. Since the record does not report the primary analysis, those interpretations cannot be made for this trial from its registry information.
The planning illustrations are not evidence of an observed effect and are not observed power. They rely on assumptions described for planning and cannot stand in for the completed trial’s results. Similarly, the serious adverse event counts describe reported events but do not by themselves establish whether an event was caused by a study intervention. The registry summary supports a description of the study’s question, design, planned outcome, and reported safety counts; it does not support a claim about efficacy or a definitive comparative safety conclusion.
13. Why This Trial Matters Statistically
This trial raises a statistical question that is common in rehabilitation research: how to compare the course of a continuous measure when participants are assessed repeatedly. The registry describes baseline and post-surgery strength measurement, with interest in both differences between groups and changes within participants. Those questions require clarity about the time points, the contrast of interest, the handling of correlated observations, and the uncertainty around the estimate.
The randomized parallel design is relevant because the intended comparison is between two assigned rehabilitation approaches. But the design label alone does not explain how the analysis treated repeated measurements, missing follow-up values, or multiple outcomes. The registry record does not report those methods or the results for the primary endpoint. This makes transparent reporting of estimates and analysis details especially important for readers seeking to evaluate the strength comparison.
The registry also lists morphology and biomechanics outcomes in addition to strength. In general, several related measures may offer different views of a rehabilitation process, but they also create choices about outcome priority and multiplicity. A clear distinction between the primary question and secondary measures helps prevent selective emphasis. The record identifies the primary measure but does not report a hierarchy or multiplicity strategy.
The study is therefore statistically instructive even without a posted primary result: it shows why a completed randomized trial cannot be interpreted from enrollment and design information alone. Readers need the analyzed data, effect estimates, uncertainty, and analysis population to judge what the observations support. The available registry account leaves those outcome-level questions unresolved.
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 principal limitation for statistical interpretation is that the registry record does not report the primary outcome analysis. It gives no numerical quadriceps strength results, group contrast, confidence interval, or p-value. The description of a planned comparison across time points does not identify which contrast was ultimately estimated or how it was modeled.
Participant flow and outcome availability are also not reported. Although enrollment is listed as 55, the number assigned to each group, the number contributing primary outcome data, and reasons for missing assessments are not provided in the registry record. The registry does not report the analysis population or whether all randomized participants were included in the primary analysis. The record also does not specify how missing observations were handled.
Important design and analysis details are absent from the registry record, including the randomization procedure, allocation concealment, the roles covered by triple masking, and any baseline adjustment. The planned measurement period is described, but the analysis model, time-point contrasts, and handling of repeated measurements are not reported. The approach to multiplicity across time points and the listed additional outcomes is likewise not reported.
The study summary describes training and assessment schedules, but actual adherence, treatment exposure, and completion by arm are not reported in the registry record. The serious adverse event information is limited to group counts and a listed event term; further details about timing, attribution, and participant-level circumstances are not reported. These limitations constrain both outcome interpretation and assessment of the precision and generalizability of any treatment comparison.
15. Related Tutorials
16. Related Statistical Calculators
17. Sources
- ClinicalTrials.gov: The Effect of Various Strength Training Protocols in ACL Reconstructed Participants — NCT03364647.
- Registry record last updated 2025-01-13; status last verified 2025-01.
- Results first posted 2024-12-04.
- 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.
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18. Record Summary
NCT03364647 is a completed randomized parallel-group trial with triple masking recorded and an enrollment of 55. The study compares blood flow restriction training with standard care against standard care plus sham blood flow restriction training in participants described as having an ACL tear and undergoing or having undergone ACL reconstruction.
The primary outcome is change in isometric peak torque quadriceps strength in Nm/Kg, measured with a Biodex Multi-Joint System 4 Isokinetic Dynamometer at baseline and post-surgery, up to 5 months. The registry lists eight outcome measures and zero analysis records. A primary outcome estimate and its uncertainty are not reported in the registry record. Safety entries report one serious adverse event in the blood flow restriction training arm and zero in the comparator arm, with no other adverse events or deaths reported in either arm.