Effect of Electromyographic Biofeedback on Quadriceps Neuromuscular Function in Patients With Quadriceps Inhibition: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Effect of Electromyographic Biofeedback on Quadriceps Neuromuscular Function in Patients With Quadriceps Inhibition (NCT02095223), a randomized na study. The primary outcome is Change From Baseline in Quadriceps Central Activation Ratio.

2. Clinical Question

The clinical question concerns a measure of quadriceps activation, rather than a direct measure of symptoms, daily function, or later injury. The registry record describes central activation ratio as a relationship between force produced during a maximal voluntary knee-extension effort and the highest force achieved after electrical stimulation of the quadriceps. The study aimed to compare whether adding electromyographic biofeedback to exercise was associated with a different change in that measure than traditional exercise alone.

The registry record also lists change from baseline in the quadriceps Hoffmann reflex as a secondary outcome. That measure is distinct from the primary central activation ratio endpoint. The study is listed as randomized, single blind, and parallel, but the record does not identify who was blinded. The record reports a terminated status; the reason for termination is not reported in the registry record.

3. Trial Design

The registry record describes a randomized, single-blind, parallel-group trial sponsored by the University of Miami. It lists the condition as knee injuries and the study status as terminated. The record lists enrollment as 4, while the study description planned to enroll 30 participants aged 18-40. These are different pieces of information: the planned enrollment in the description is not the same as the enrollment recorded for the trial.

The groups were electromyographic biofeedback supplemented exercise and traditional exercise. The biofeedback description says participants would be instructed in use of the device and would use it during exercises. The traditional-exercise description refers to a 14-day program containing four quadriceps-strengthening exercises, with both non-weight-bearing and weight-bearing exercises. The descriptions do not establish how closely participants followed either program, and compliance results are not reported in the registry record.

The primary outcome was change from baseline in quadriceps central activation ratio, with the stated timeframe of baseline and 14 days. The registry record describes an isometric knee-extension effort and electrical stimulation of the quadriceps as part of the measurement. Change from baseline in quadriceps Hoffmann reflex was listed as a secondary outcome.

Random allocation can help make treatment groups comparable on average, but it does not ensure comparability in a trial with very few observations. The record does not report the allocation sequence method, allocation concealment, who was blinded, the reason for termination, or the intended analysis plan. It also does not report a sample-size justification. Those details cannot be inferred from the randomized and single-blind labels alone.

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 From Baseline in Quadriceps Central Activation Ratio, measured over Baseline and 14 days.

The primary endpoint is change from baseline in quadriceps central activation ratio, reported in the unit “percentage change from baseline.” The stated assessment timeframe is baseline and 14 days. The registry record describes a participant exerting maximal voluntary force during knee extension while secured in a dynamometer chair. Electrical stimulation is then applied to the quadriceps, producing a twitch and a temporary increase in force. The central activation ratio is calculated from the voluntary effort and the highest force achieved after stimulation.

As a general measurement concept, a central activation ratio is used as an indicator of how completely a person can voluntarily activate a muscle during a maximal effort. The comparison of voluntary force with the stimulated response provides information about activation that a simple strength measurement alone may not capture. This makes the measure relevant to the trial’s focus on quadriceps inhibition.

The endpoint is a physiological measure, not a direct report of pain, knee-related function, activity, or recovery. A change in the measure should therefore be interpreted as a change in the measured activation outcome, not automatically as a change in how participants feel or function. The registry record does not report a threshold for a clinically important change, or evidence linking a particular change in this measure to a patient-important benefit.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

General: The primary endpoint is continuous: it can take values across a scale rather than classifying each participant into a category. The registry record specifies a mean as the summary measure and standard deviation as the measure of spread. A mean describes the average recorded change in a group. A standard deviation describes how dispersed individual observations are around that group mean, when enough observations are available for the measure to be informative.

For the biofeedback group, the record reports a mean change of 15.0 and a spread of 0.0, with n=1.0. A single observation cannot show how much participants in a wider population might vary. Thus, the reported spread does not establish that the population has no variation. For traditional exercise, the reported mean is 20.5 and the standard deviation is 11.4, with n=2.0. With so few observations, the mean and spread are unstable descriptions of what might be seen in other participants.

General: A treatment comparison ordinarily focuses on an estimated difference between groups, accompanied by an assessment of uncertainty. A confidence interval is one way of expressing a range of values reasonably compatible with the data and analysis assumptions. Wider intervals indicate less precision. A hypothesis test can summarize how compatible the observed data are with a specified null hypothesis, but a p-value does not measure the probability that a treatment works, nor does it communicate the size or clinical importance of an effect.

For this primary endpoint, the registry record does not report a two-arm estimate, confidence interval, or p-value. It states that values were missing or not estimable for a two-arm comparison of the continuous endpoint. The descriptive arm means are therefore not substitutes for a comparative analysis. No result should be constructed by subtracting one posted mean from the other; a recalculated comparison is not reported in the registry record, and the information needed to assess an appropriate analysis is not available.

General: Small samples can make estimates imprecise and can make statistical procedures sensitive to assumptions about the outcome distribution. A standard deviation calculated from very few observations is itself uncertain. In addition, randomization does not remove chance imbalances when only a few observations are available. These issues limit how confidently a result can be generalized beyond the observed participants, regardless of whether a numerical group mean can be reported.

The record identifies random allocation, single masking, and a parallel model. Those labels describe broad design features, but do not specify the random-sequence method, allocation concealment, the identity of the blinded party, or the details of the planned statistical analysis. Those methods are not reported in the registry record. The record also reports zero analyses, so it does not document an inferential analysis of the posted primary endpoint.

The registry record includes sample-size planning illustrations based on the observed effect. The stated assumptions are a two-sided significance level of 0.05, equal allocation between arms, and a normal approximation; the planned effect is expressed as a fraction of the observed effect. These are planning illustrations, not evidence that the completed trial had a particular probability of detecting an effect. They should not be described as observed power. Because the underlying primary comparison is not estimable in the registry record, such illustrations also cannot replace a prespecified design justification. The sample-size justification for the trial itself is not reported in the registry record.

General: Over-dispersion means that outcome variation is greater than a model assumes. When a model underestimates variation, its uncertainty estimates can be too small and its tests can appear more decisive than warranted. The posted summaries do not support a meaningful assessment of over-dispersion: there are too few observations, and no comparative model or analysis is reported. No particular model choice or variance adjustment can be attributed to the investigators from this record.

A “recalculated” analysis, when available, would be a simple unadjusted calculation based on posted summary statistics and would not necessarily reproduce an investigator’s analysis. No such comparative recalculation is reported for this endpoint. The record does not flag a discrepancy between a sponsor analysis and a recalculation, but it also supplies no sponsor-reported comparative analysis to interpret. The appropriate conclusion remains that the registry record presents descriptive group summaries without an estimable between-group result.

10. Multiplicity, Missing Data and Analysis Populations

The registry record lists one secondary outcome: change from baseline in quadriceps Hoffmann reflex. It also reports two outcome measures, but does not provide a posted secondary-outcome result in the registry record for interpretation. The record lists zero analyses. It does not report whether the primary and secondary outcomes were handled in a prespecified hierarchy or whether any adjustment for multiple comparisons was planned.

Multiplicity is the general issue that arises when several outcomes, time points, or statistical tests are examined. As the number of analyses increases, the chance of finding an apparently unusual result by chance can also increase. Statistical approaches to multiplicity can control this risk, but the appropriate approach depends on the study’s objectives and analysis plan. Since the registry record does not report that plan or inferential analyses, it is not possible to determine whether multiplicity was addressed.

The primary outcome counts are n=1.0 for electromyographic biofeedback and n=2.0 for traditional exercise, while the record lists enrollment as 4. The reason those counts differ is not reported in the registry record. The record does not state whether outcome data were missing, whether participants were excluded from an analysis, or whether the posted counts represent a particular analysis population. A participant flow account and the rules used to define the analysis population are not reported in the registry record.

Missing-data handling is also not reported. The record does not describe imputation, assumptions about missing outcomes, or sensitivity analyses. Without those details, it is not possible to assess whether the available outcome summaries could be affected by missing data. The reason for the terminated status is not reported, and the record does not indicate whether termination affected outcome collection or analysis.

11. 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 adverse-event record lists 2 participants at risk in each group for serious adverse events, with 0 affected in each group. It also lists 2 participants at risk in each group for other adverse events, with 0 affected in each group. These are the posted counts; they should be read as event summaries for the recorded risk groups, not as comparative safety estimates.

Zero reported events in these small groups does not establish that an event cannot occur or that the interventions have equivalent safety. With few participants, uncommon events may not appear in the observed record. The adverse-event counts also do not provide a precise estimate of event frequency in a broader population. No statistical comparison of adverse events is reported.

The deaths field is null for both groups. A null entry is not the same as a recorded count of zero; deaths are not reported in the registry record. The record lists no top serious-event terms. The timing, collection method, severity definitions, and relationship assessment for adverse events are not reported in the registry record. The figures should therefore be read narrowly as the event counts posted, rather than as a complete account of safety.

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

The record documents a randomized comparison of electromyographic biofeedback supplemented exercise and traditional exercise, with quadriceps central activation ratio change identified as the primary endpoint. It posts a mean change of 15.0 for the biofeedback group and 20.5 for the traditional-exercise group, alongside the reported group sizes and spread. Those values describe the recorded observations; they do not establish a dependable difference between the interventions.

The primary endpoint comparison is not estimable in the registry record. No comparative effect estimate, confidence interval, or test result is reported. Accordingly, the posted means do not establish that either group had a larger change in the underlying population. The small outcome counts also mean that the summaries may be strongly influenced by individual observations and do not provide a precise account of typical responses.

The outcome itself is a measure of quadriceps activation during a laboratory-style voluntary effort and stimulation procedure. It is not a direct measure of pain, everyday knee function, physical activity, or quality of life. The registry record does not report a threshold that would distinguish a clinically important change from a smaller change in this measure. The results therefore cannot be translated into a claim about patient experience or broader clinical benefit.

Likewise, the adverse-event record reports zero serious adverse events and zero other adverse events among the participants listed at risk in each group, but the numbers are too limited to establish comparative safety. The death entries are null rather than recorded zeros. The terminated status and the reason for termination are important context, but the reason is not reported in the registry record.

In statistical terms, the most defensible reading is that the registry contains very limited descriptive outcome information and does not answer the planned between-group question. It does not establish benefit, lack of benefit, or equivalence. It also does not show that the interventions are interchangeable. The absence of an estimable comparison is an absence of usable comparative evidence in this record, not evidence that the true effect is zero.

13. Why This Trial Matters Statistically

This trial is statistically instructive because it illustrates the difference between reporting group summaries and answering a comparative research question. The primary question concerns whether change differs between randomized groups. Means for each group are not, by themselves, an estimate of that contrast, and they do not communicate the uncertainty around it. Here, the registry record reports the group summaries but says the two-arm comparison is missing or not estimable.

The small outcome counts matter for both precision and interpretation. With n=1.0 in one group, the data cannot describe variation among participants in that group. With n=2.0 in the other, the reported mean and standard deviation remain vulnerable to the influence of individual observations. Randomization is valuable for controlling confounding in a well-conducted study, but a randomized label cannot compensate for very limited outcome information.

The record also demonstrates why planned enrollment, recorded enrollment, and outcome counts should not be treated as interchangeable. The study description planned 30 participants, the registry lists enrollment as 4, and the posted primary summaries have their own group counts. The record does not explain these differences. It also gives the study a terminated status without reporting the reason.

Finally, physiological endpoints require careful interpretation. A change in central activation ratio addresses a specific measurement question, not every aspect of knee health or recovery. Without a reported comparative analysis, uncertainty estimate, and context for clinical importance, readers should resist turning descriptive values into a conclusion about the intervention. The statistical contribution of this record is chiefly a reminder that incomplete or non-estimable outcomes cannot support a firm comparative claim.

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 primary limitation is that the registry record does not report an estimable comparison of the two groups for the continuous primary endpoint. The posted means are based on n=1.0 and n=2.0, leaving very limited information about either group’s outcome distribution. The mean and spread for such small groups cannot provide a stable account of expected responses in a wider population.

The record lists enrollment as 4, whereas the study description planned to enroll 30 participants. The primary outcome counts do not account for every participant represented by the enrollment field, and the reason is not reported in the registry record. There is no reported participant flow, missing-data explanation, analysis-population definition, or sensitivity analysis to clarify how the outcome summaries arose.

The terminated status is another limitation in interpreting the record. The reason for termination and its relationship to recruitment, follow-up, or analysis are not reported. The registry record does not provide an analysis plan, sample-size justification, allocation details, identity of the blinded party, or a comparative primary result. No inferential analysis is listed.

The outcome is specific to quadriceps activation and is not accompanied by a reported clinically important threshold. The registry record also does not post a result for the listed secondary outcome in the registry record for interpretation. Adverse-event counts are small, and the death entries are null rather than reported as zero. Taken together, the record supports only a cautious description of a limited set of posted observations, not a precise or generalizable treatment comparison.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: Effect of Electromyographic Biofeedback on Quadriceps Neuromuscular Function in Patients With Quadriceps Inhibition — NCT02095223.
• Registry record last updated 2017-02-01; status last verified 2016-12.
• Results first posted 2016-08-30.
• 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.

18. Record Summary

The registry record describes NCT02095223, a randomized, single-blind, parallel trial sponsored by the University of Miami and listed as terminated. It compared electromyographic biofeedback supplemented exercise with traditional exercise in people with knee injury and quadriceps inhibition. The primary endpoint was change from baseline in quadriceps central activation ratio at baseline and 14 days; change from baseline in quadriceps Hoffmann reflex was listed as a secondary outcome.

The primary summaries report mean changes of 15.0 and 20.5, with outcome counts of n=1.0 and n=2.0, respectively. The registry record states that a two-arm comparison for the continuous endpoint is missing or not estimable and lists zero analyses. The reason for termination, missing outcome information, and analysis methods are not reported in the registry record. The adverse-event entries report zero serious and other events in each group; death entries are null.