Ankle Robotics Training After Stroke: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Ankle Robotics Training After Stroke (NCT01337960), a randomized na study. The primary outcome is Self-selected Floor Walking Velocity Change From Baseline to Post-training and Retention.

2. Clinical Question

3. Trial Design

The registry record describes Ankle Robotics Training After Stroke as a randomized, single-masked, parallel-group trial. It lists enrollment as 41 and status as completed. The record gives the study start as 2011-07 and primary completion as 2014-03. The phase is listed as NA, and the sponsor is the US Department of Veterans Affairs.

The three listed conditions correspond to Seated Robot Training (SRT), Treadmill Locomotor-based Training (TMR), and Treadmill Only (TMO). SRT used seated visuomotor practice with an ankle robot; TMR used the robot during treadmill locomotor training; and TMO used treadmill training without robotic support. The descriptions for the training arms specify 3x weekly sessions over 6 weeks (18 sessions).

There is an important design detail: the TMO arm description says its volunteers came from another treadmill training study and were evaluated at baseline and after training. Although the overall design is recorded as randomized, the registry record does not explain how volunteers from that other study were incorporated into random allocation, or whether all three groups were randomized together. Allocation procedures, concealment, and the identity of the masked party are not reported in the registry record.

The primary outcome timeframe includes baseline, a post-training assessment at 6 weeks, and retention at 12 weeks; the record notes that TMO had no retention period. The record lists additional outcomes related to gait kinetics, balance, dynamic gait, and anticipatory postural adjustments. It does not give enough detail to determine which assessments were available at every time point or how all planned outcomes were analyzed.

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: Seven subjects who were enrolled (via informed consent) did not receive the allocated intervention due to: relocation (3), lack of transportation (2), re-entry into physical therapy (1), and deemed too high functioning upon neurological re-examination (1). These pre-assignment losses were not counted in the subject tally of baseline assessments.

Overall Study

Reasons for not completing this period:

Analysis population for the primary outcome, as defined in the registry: Nonparametric Fisher's exact test was applied to compare between group changes at retention.

5. Baseline Characteristics

The table reproduces the baseline characteristics posted in the registry, which describe the participants analysed at baseline and help show whether the randomized groups were comparable.

Population: Groups were compared at baseline using Friedmans test and Wilcoxon Sign Rank tests

6. Primary Endpoint

The registry lists the primary outcome as Self-selected Floor Walking Velocity Change From Baseline to Post-training and Retention, measured over Baseline, Post-test training at 6 weeks; Retention at 12 weeks (note TMO control has no retention period).

The primary endpoint was self-selected floor walking velocity change from baseline to post-training and retention, measured in cm/sec. The description refers to velocity during self-selected, most comfortable and fastest floor walking over 10m, together with associated spatio-temporal gait parameters. The registry record therefore identifies walking speed as the central continuous measure, while also noting more than one walking condition and more than one assessment time.

Walking velocity is used to describe performance during walking in a standardized task. A change from baseline can express how a participant’s measured walking speed differs after training, while a retention assessment can describe later measurement after the training period. These are general interpretations of the measure; they do not establish what happened in this trial. The record does not report the group means, standard errors, changes, confidence intervals, or between-group estimates for this endpoint.

The record labels the measure as a mean with standard error as the dispersion. In general, a mean describes the average observed measurement, while a standard error describes the precision of an estimated mean. A standard error is not the spread of individual participant measurements. Without the numerical results and analysis details, the registry record does not permit a quantitative assessment of the size or precision of the walking-velocity changes.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The trial is recorded as randomized, single-masked, and parallel-group. In general, random allocation is intended to reduce systematic differences between groups at the start of a study. Masking can limit the influence of expectations on some aspects of measurement or conduct. The registry record does not say who was masked, how allocation was carried out, or how the study maintained masking. The TMO description says its volunteers came from another treadmill training study; the record does not clarify how those volunteers fit with the overall randomized design.

What does the endpoint summary tell the reader?

The primary outcome is a continuous measure: self-selected floor walking velocity, expressed in cm/sec. The record says the summary parameter is a mean and that dispersion is represented by the standard error. In general, the mean is an average of observed measurements. The standard error describes uncertainty in an estimated mean, rather than the variation among individual measurements. Interpreting a standard error requires knowing what estimate it accompanies and how it was calculated; the registry record gives no numerical endpoint summaries.

The endpoint description includes comfortable and fastest walking, baseline and post-training assessment, and retention. A change score compares a post-baseline measurement with the baseline measurement for the relevant participant or group. In general, comparing change between groups can help distinguish change associated with one training approach from change observed in a comparator group. It does not, by itself, resolve bias from missing data, differences in assessment, or other design issues. The record does not report the actual change estimates or the method used to construct them.

How should the stated retention test be understood?

The registry record says that a nonparametric Fisher's exact test was applied to compare between-group changes at retention. In general, Fisher's exact test evaluates association in categorical count data and is often used when a count-based comparison is appropriate. The primary endpoint, however, is described as a continuous mean. The record does not explain whether continuous changes were categorized for this test, what data were entered, or what comparison the test evaluated. It also does not report the test result. The method statement should therefore be read as a registry description, not as enough information to reconstruct or validate the analysis.

More generally, nonparametric methods can be useful when an analysis does not rely on a particular parametric distributional assumption. The term alone does not specify how observations were summarized, which test statistic was used, or what assumptions remain. The registry record does not report those details for the retention comparison. Nor does it describe methods for the post-training comparison, the comfortable and fastest conditions, or the secondary outcomes.

What do planning assumptions mean?

The record describes a planning illustration based on the observed effect, using a two-sided significance level of 0.05, equal allocation between the two arms, and a normal approximation. It says the effect to detect is a stated fraction of the observed effect. Such an illustration is a planning exercise: it asks what participant count per arm would be needed under the stated assumptions to detect a specified effect with a chosen power. It is not observed power and does not show that the trial had a particular chance of finding an effect.

Those planning assumptions are not a report of the trial’s original design justification. The record does not report the original sample-size calculation, the effect assumed when the study was planned, or the power target used by investigators. Numerical planning results are not reported in the registry record. The illustration should not be treated as evidence about the observed outcomes or as proof that an analysis was adequately powered.

Why can a confidence interval be useful?

In general, a confidence interval communicates uncertainty around an estimate, making it possible to assess which effect sizes are compatible with the data under the method’s assumptions. A p-value, when reported, addresses compatibility with a specified null hypothesis under an analysis model; it does not describe effect size or clinical importance. Neither measure substitutes for a clear description of the comparison, the participants included, and the data analyzed. The registry record does not report confidence intervals or p-values for the primary endpoint, so those interpretations cannot be made for this trial.

Over-dispersion is a general issue in count analyses: observed variation can exceed what a simple model assumes, potentially making uncertainty appear too small if the model does not account for the extra variation. The record does not identify a count model for the primary outcome, and no over-dispersion assessment is reported in the registry record. This concept is not a finding about the trial; it illustrates why interpretation depends on the outcome scale and the specified analysis.

10. Multiplicity, Missing Data and Analysis Populations

The primary outcome description encompasses comfortable and fastest floor walking, post-training assessment, and retention. These create multiple outcome conditions or time points rather than a single reported comparison. The registry record explicitly does not reduce the primary outcome to one comparison. It also notes that TMO had no retention period, which means the retention assessment is not described as available for that group.

The record lists secondary outcomes of gait kinetics, Berg Balance Scale, Dynamic Gait Index, and Anticipatory Postural Adjustments. It gives 5 outcome measures and 4 analyses, but does not explain how those counts relate to the listed outcomes. It does not report whether a primary contrast was selected in advance, whether secondary analyses were exploratory, or whether any adjustment was made for multiple comparisons. Without this information and the outcome results, the chance of a false-positive finding across multiple analyses cannot be assessed.

Missing-data methods, the number of participants with measured outcomes at each assessment, and the analysis populations are not reported in the registry record. The record does not say whether analyses followed assigned groups, included only participants who completed training, or used another population definition. It also does not describe how missing endpoint values were handled. These details matter because exclusions or missing measurements can affect both the estimated changes and the interpretation of comparisons. The record identifies enrollment, but does not establish how many participants contributed to each outcome 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.

Most frequent serious adverse event terms

Most frequent non-serious adverse event terms

Serious events with the highest arm-level rate: chest pain (16.7%), jacksonian seizure (7.1%), ankle sprain (7.1%).

The registry record gives serious and other adverse-event counts separately by training group. For SRT, 14 were listed as at risk for serious events and 2 as affected; 14 were listed as at risk for other events and 3 as affected. For TMR, the corresponding counts were 14 at risk and 0 affected for serious events, and 14 at risk and 9 affected for other events. For TMO, the record lists 6 at risk and 1 affected for serious events, and 6 at risk and 0 affected for other events.

These are recorded counts, not evidence that an event was caused by the training. The record does not supply event-level context, severity details for the other events, or a method for comparing safety across groups. The serious-event terms listed are Chest pain (16.7%), Jacksonian Seizure (7.1%), and Ankle sprain (7.1%). The record does not specify the denominator or group attribution for those percentages, so they should not be assigned to a particular arm.

Deaths are listed as null for each group; death counts are therefore not reported in the registry record. A null entry should not be interpreted as a confirmed count of zero. The counts also do not indicate how long each participant was observed or whether participants had comparable exposure time.

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

The registry record establishes that a randomized, single-masked, parallel-group study was registered as completed, with three training approaches and a primary endpoint focused on self-selected walking velocity. It describes the intervention schedules and names a retention assessment. It also reports group-level adverse-event counts and identifies several serious-event terms.

It does not report numerical results for walking velocity or the listed secondary outcomes. There is no basis in the registry record to state whether average walking speed increased or decreased, whether one group changed more than another, or how precise any estimated difference was. The record also does not provide the outcome data needed to evaluate the stated retention test. Consequently, it cannot establish a comparative benefit or lack of benefit for any training approach.

General statistical interpretation distinguishes the size of an estimated effect from its uncertainty. A small p-value, if one were reported, would not by itself establish that a difference is important; a non-significant result would not establish equivalence. Confidence intervals can help show the range of effects compatible with an estimate, but none are reported for the primary outcome. These are general principles, not conclusions about this trial.

The safety counts describe events recorded in the groups, but they do not establish causation or allow a fair comparison of risk without further context. The registry record does not report event-level descriptions, observation time, or a method for statistical safety comparisons. The listed percentages for serious-event terms also lack a reported denominator and group attribution.

In practical terms, the record supports a description of the question, design, training approaches, endpoint, and some safety entries. It does not provide the outcome findings needed to judge the observed walking-velocity changes. Conclusions about efficacy, clinical importance, or comparative safety would go beyond what is reported in the registry record.

13. Why This Trial Matters Statistically

This trial is statistically notable because it describes multiple training approaches that target gait and balance through different routes: seated ankle-robot practice, ankle-robot use during treadmill walking, and treadmill walking without robotic support. The primary measure, self-selected floor walking velocity, directly represents a walking performance outcome. The combination of post-training and retention assessment also raises a distinction between immediate change and whether a measured change is present at a later assessment.

Those design features make clarity about the estimand especially important. A comparison of average change after training is not necessarily the same question as a comparison at retention, and comfortable and fastest walking conditions are not interchangeable. The registry record does not identify a single primary contrast or provide outcome estimates for these conditions. The TMO group’s lack of a retention period also limits the stated scope of retention comparisons.

The record further illustrates why reporting the analysis method matters. It describes the endpoint as continuous and summarized by a mean and standard error, yet names a Fisher's exact test for between-group changes at retention without explaining the data representation or test application. Clear descriptions of the contrast, analysis population, missing-data handling, and uncertainty would help readers assess whether the method matches the question.

Finally, the reported adverse-event counts are useful descriptive information, but the record leaves denominators for listed serious-event percentages and the relationship of those terms to groups unclear. Together, these features show why a trial’s question and design can be interpretable while its comparative results remain uncertain when numerical outcome findings and analysis details are not reported in the registry record.

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 for interpreting this trial is that numerical results for the primary and secondary outcomes are not reported in the registry record. No group means, changes, standard errors, confidence intervals, test statistics, or outcome p-values are given. It is therefore not possible to assess the magnitude, direction, or precision of the reported endpoint changes from the record.

The primary outcome covers multiple walking conditions and assessment times, but the record does not identify a single comparison or provide a full account of the analysis. It states that Fisher's exact test was used for between-group changes at retention, without explaining how this test was applied to the continuous endpoint. The record also notes that TMO had no retention period, limiting what can be inferred about a retention comparison involving that group.

The TMO arm description says its volunteers came from another treadmill training study. Although the overall design is recorded as randomized, the record does not explain how this group relates to random allocation. Detailed eligibility criteria, participant characteristics, allocation procedures, masking details, adherence, and treatment fidelity are not reported in the registry record.

Analysis populations and missing-data handling are not reported. Nor are multiplicity procedures, the original sample-size justification, or a complete statistical analysis plan. Safety information is also limited: event narratives and observation time are absent, deaths are listed as null, and denominators or group attribution for the listed serious-event percentages are not specified. These gaps constrain interpretation of both outcome and safety comparisons.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: Ankle Robotics Training After Stroke — NCT01337960.
• Registry record last updated 2015-06-12; status last verified 2015-05.
• Results first posted 2015-06-12.
• 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

NCT01337960, Ankle Robotics Training After Stroke, is recorded as a completed, randomized, single-masked, parallel-group trial sponsored by the US Department of Veterans Affairs. Enrollment is listed as 41. The record identifies SRT, TMR, and TMO training groups and describes the primary outcome as change in self-selected floor walking velocity from baseline to post-training and retention.

The intervention descriptions distinguish seated robot training, treadmill walking with an ankle robot, and treadmill-only training. The primary outcome is a continuous mean measured in cm/sec, but numerical outcome results are not reported in the registry record. The record names a Fisher's exact test for retention changes without explaining its application to the continuous endpoint.

Group-level adverse-event counts are reported, while deaths are listed as null. Important details about outcome estimates, missing data, analysis populations, multiplicity, and safety-event context are not reported in the registry record.