An Exploratory Clinical Study on a Variable Speed and Sensing Treadmill System (VASST) for Hemiparetic Gait Rehabilitation: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for An Exploratory Clinical Study on a Variable Speed and Sensing Treadmill System (VASST) for Hemiparetic Gait Rehabilitation (NCT01811680), a na phase 1 study. The primary outcome is 6 Minute Walk Test (Metres).

2. Clinical Question

3. Trial Design

The record describes a Phase 1 feasibility and safety study of the Variable Speed and Sensing Treadmill for gait rehabilitation after stroke. The study is marked completed, with an enrollment of 10. Tan Tock Seng Hospital is listed as sponsor. The recorded start is 2012-08 and the primary completion is 2013-07. The brief summary describes the study as occurring over a period of 2 months.

The design is single group, with allocation listed as NA and masking listed as NONE. The intervention is supervised treadmill training on the variable sensing treadmill. There is no like-for-like control group in the record, so comparisons between an intervention arm and a control arm are not available. Assessments made at different times in the same study do not create a randomized or concurrent comparison.

The primary outcome is the 6 Minute Walk Test, recorded in metres, with a mean and standard deviation as the stated summary measures. It was assessed at weeks 0, 2, 4 and 8. The description calls it an assessment of distance walked within six minutes and a submaximal test of endurance. The primary outcome population is described as chronic stroke, while the title refers to subacute stroke patients. The record does not explain the difference.

The registry lists two outcome measures, but details for the other measure are not reported in the registry record. No statistical analyses are listed. The protocol, sample-size justification, interim analyses, and statistical analysis plan are not reported in the registry record. The study’s feasibility and safety framing is useful context, but it does not substitute for a reported account of how outcomes were analysed.

4. Participant Flow and Accounting

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

Overall Study

Analysis population for the primary outcome, as defined in the registry: chronic stroke

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 6 Minute Walk Test (Metres), measured over 8 weeks.

The primary endpoint is the 6 Minute Walk Test, measured in metres. Its description specifies the distance walked within six minutes and characterizes the test as a submaximal assessment of endurance. A distance measure offers a direct, interpretable way to describe walking performance, while repeated assessments can describe how recorded performance varies over the study schedule. The registry lists assessments at weeks 0, 2, 4 and 8.

The specified summary is a mean with standard deviation. In general, a mean describes the central value of measurements, while a standard deviation describes how spread out individual measurements are around that mean. Those summaries can help characterize both typical walking distance and variation among participants, but they do not by themselves show the uncertainty around a change or establish that a change is attributable to the intervention.

The registry record does not report the mean distances, standard deviations, or changes between assessment times. It also does not state how measurements from the same participant were handled in an analysis. As a result, the endpoint’s definition and schedule are available, but the observed walking-distance findings and their precision are not reported in the registry record. The clinical importance of any change cannot be assessed from the posted record without those results and an appropriate interpretation framework.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The statistical information in the registry record is sparse. It identifies a continuous primary measure summarized as a mean and standard deviation, but lists no analyses and does not report the endpoint values. The following concepts explain what such methods can contribute in general; they do not describe analyses confirmed for this study.

What does a mean and standard deviation describe?

For a continuous measure such as walking distance in metres, a mean gives a summary of the measurements’ central location. A standard deviation describes how much individual measurements vary around that mean. The two summaries answer different questions: the mean characterizes the group’s average distance, while the standard deviation characterizes variation among participants. Neither summary alone gives the uncertainty in an estimated mean or change. A standard deviation is not a confidence interval, and a larger or smaller standard deviation should not be read as a treatment effect.

The registry record specifies these summaries but does not report their values at the assessments. It therefore does not allow a reader to examine the observed distribution, compare the means across time, or assess how much participant measurements varied. The registry also does not report whether the endpoint was summarized at each assessment, as a change from an initial assessment, or in another way.

Why do repeated measurements need care?

In general, observations from the same participant over time tend to be related: a participant’s measurements may share characteristics that make them more alike than measurements from different participants. An analysis that treats every observation as independent can misstate uncertainty when this relationship is ignored. Methods for repeated measures account for this dependence, but the appropriate method depends on the data structure, assumptions and analysis objective. The registry record does not report which method, if any, was used for the assessments at weeks 0, 2, 4 and 8.

Repeated measurements can also be incomplete. If a participant misses an assessment, the amount and pattern of missingness can matter for interpretation. In general, analysts need to state how incomplete measurements were handled and what assumptions support that approach. The registry record does not report completion by assessment, reasons for missing measurements, or a missing-data method. It is therefore not possible to infer that every enrolled participant contributed every scheduled measurement.

What would a confidence interval add?

In general, a confidence interval communicates uncertainty around an estimate, such as a mean or a difference in means. Its width reflects both the variability in the data and the amount of information available, along with assumptions of the method. A narrow interval indicates greater statistical precision than a wide interval, but precision is not the same as clinical importance. An interval that includes values on different sides of no change can be compatible with a range of possible effects; interpretation depends on the actual estimate, interval and relevant clinical context.

No confidence interval or endpoint estimate is reported in the registry record. There is consequently no basis to characterize the precision of the walking-distance outcome. A p-value, if available, would address compatibility of the data with a specified statistical model or null hypothesis; it would not by itself show the magnitude, importance, or cause of a change. No p-value or hypothesis test is listed.

What does over-dispersion mean in general?

Over-dispersion occurs when data vary more than a statistical model expects. It is particularly relevant to certain count outcomes and can make standard errors too small if the extra variation is ignored. The primary endpoint in this study is described as a continuous distance measure, not a count outcome, and the registry record does not indicate that an over-dispersion model was used. More generally, choosing a model requires examining the outcome’s scale and distribution; it would not be appropriate to assume a specific model from the endpoint name alone.

How should the planning illustration be read?

The registry’s sample-size assumptions describe a planning illustration computed from an observed effect, with a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation. The illustration varies the effect to detect as a stated fraction of the observed effect. For time-to-event calculations it describes total events; for other calculations it describes participants per arm. These are planning assumptions, not a description of the actual single-group design. The study itself has no two-arm allocation in the registry record, so hypothetical participants per arm must not be mistaken for actual enrollment or a control comparison.

Such planning values are not observed power. In general, a planning calculation describes the sample size implied by specified assumptions; it does not establish the probability that a completed study detected an effect. The registry record does not report a sample-size justification for the actual study, and the endpoint results needed to judge an observed effect are not reported. The planning illustration therefore cannot fill the gaps in the outcome reporting or establish the study’s sensitivity to a clinically meaningful change.

10. Confidence Intervals for Each Arm

No two-arm comparison is shown for this trial, but each arm's mean can be given with a t-based 95% confidence interval computed from the posted mean, spread and number of participants.

R code and output

arm <- c("Supervised Treadmill Training")
n   <- c(10)
m   <- c(54.3)
sp  <- c(30.9)
sd  <- sp      # posted standard deviations
for (i in seq_along(n)) {
  se <- sd[i] / sqrt(n[i]); h <- qt(0.975, n[i] - 1) * se
  cat(sprintf("CARM|%s|%d|%.3f|%.3f|%.3f|%.3f\n", arm[i], n[i], m[i], sd[i], m[i] - h, m[i] + h))
}

CARM  Supervised Treadmill Training  10  54.300  30.900  32.195  76.405

11. Multiplicity, Missing Data and Analysis Populations

The registry lists two outcome measures, but gives details for the 6 Minute Walk Test as the primary outcome. The identity, definition, timing and analysis of the other measure are not reported in the registry record. The record lists no analyses, so it does not indicate which outcomes were tested, whether multiple time points were compared, or whether any adjustment for multiple comparisons was planned or used.

In general, multiplicity arises when several outcomes, time points, subgroups or statistical tests are considered. Examining many results can increase the chance of finding an apparently notable result by chance. A statistical plan may identify a primary analysis in advance and describe how other analyses will be interpreted. The registry record does not report such a plan or any multiplicity procedure. This absence does not show that no procedure was used; it means the approach is not reported in the registry record.

Missing-data reporting is also limited. The record lists the enrollment and scheduled assessment times, but does not report the number of measurements available at each time, reasons for missing data, or methods for handling incomplete outcomes. It does not state whether an analysis used all available measurements, a restricted set, or another approach. No assumptions about missingness can be established from the schedule alone.

The analysis population is not reported in the registry record. It does not say whether outcome summaries included all enrolled participants, only those who began training, or participants meeting another definition. No participant flow information is included in the stated details. These gaps make it difficult to assess how the analysed population relates to the enrolled group or how robust any estimate would be to incomplete data. Since numerical endpoint results and analyses are not listed, neither multiplicity nor missing-data methods can be evaluated empirically.

12. 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 5% reporting threshold.

The registry lists 10 participants at risk for serious adverse events and records 0 affected. It separately lists 10 at risk for other adverse events and records 0 affected. These counts mean that no affected participants are recorded in either of those posted categories. They should be read as registry entries for the specified categories, not as proof that no symptoms or events of any kind occurred.

The record does not describe event definitions, surveillance procedures, duration of follow-up for safety, severity grading beyond the serious-event category, or how events were attributed. It also does not report the relationship of any event to training or to the treadmill. The deaths entry is null; deaths are therefore not reported in the registry record, rather than documented as zero.

In general, a zero count in a small study still leaves uncertainty about the frequency of uncommon events, and the count depends on how events were sought and recorded. The posted figures are descriptive and do not establish that the device or training is free of risk. They also do not permit a comparative safety estimate because there is no separate comparison group. The registry’s feasibility and safety purpose is relevant context, but the available counts alone cannot characterize safety comprehensively.

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

The record establishes that a Phase 1, single-group feasibility and safety study evaluated supervised treadmill training using the Variable Speed and Sensing Treadmill. It identifies the 6 Minute Walk Test in metres as the primary outcome, specifies a mean and standard deviation, and lists assessment times at weeks 0, 2, 4 and 8. It also posts counts for serious and other adverse events. Those details define the study’s intended measurement and give limited descriptive information about recorded safety categories.

The record does not report the walking-distance measurements, changes over time, or uncertainty around any estimate. It therefore cannot establish the direction or size of a change in walking distance, whether an estimate is precise, or whether an observed change would be clinically important. The absence of endpoint results is a reporting gap, not a result indicating no improvement or deterioration.

The study has no concurrent control group in the registry description. Even if measurements had been reported as changing over time, a within-group pattern would not by itself isolate the effect of the device from other influences. The registry record also does not report a statistical analysis plan, analysis population, missing-data approach, or inferential analyses. Conclusions about causality, statistical significance, or generalizability would go beyond the available record.

The safety counts are similarly bounded. Zero affected participants are recorded in the serious and other adverse-event categories, but the record does not describe ascertainment or follow-up, and deaths are not reported. These figures should not be extended to claims about all possible events or used as a comparative risk estimate.

In short, the posted information describes the intervention, study structure, primary measure and certain safety counts, but it does not provide the outcome results needed to quantify walking-distance findings. It supports a careful account of what was planned and recorded, not a conclusion about effectiveness or a definitive safety judgment.

14. Why This Trial Matters Statistically

This study is statistically instructive because it separates a clearly defined outcome from evidence about that outcome. Naming the 6 Minute Walk Test, its unit, summary type and assessment schedule makes the intended measurement understandable. But without the actual means, standard deviations or changes, readers cannot assess the observed walking distances or their precision. Outcome definition and outcome reporting are both necessary for interpretation.

The single-group design also illustrates the difference between measuring change and estimating a comparative effect. Repeated assessments can describe a trajectory within a group, but they do not supply the counterfactual comparison needed to distinguish intervention effects from changes that might occur for other reasons. This is a design limitation, not a statistical defect that can be repaired merely by choosing a more elaborate model.

The record further highlights why analysis details matter. Measurements repeated within participants are generally related, and incomplete follow-up can affect interpretation. Without a reported analysis method, analysis population and missing-data approach, it is difficult to understand what a numerical estimate would represent even if one were posted. The registry record also lists two outcome measures but does not describe both, leaving multiplicity and outcome selection unclear.

Finally, the safety figures show the limits of zero-event reporting. Counts need context about definitions and observation procedures, and a single-group study cannot provide a comparative safety estimate. The record supports a narrow description of the entries, while broader claims require information not reported in the registry record. These distinctions are useful when reading feasibility studies, where design aims and available data may not support the same inferences as a controlled efficacy study.

15. 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 main limitation for interpreting the primary endpoint is the absence of numerical outcome results. The registry record identifies the measure and schedule but does not report walking distances, standard deviations, changes, or uncertainty estimates. As a result, neither the direction nor magnitude of any outcome pattern can be described. The second listed outcome measure is not identified in the registry record, which further limits understanding of the full set of collected outcomes.

The single-group design has no concurrent control, and masking is listed as NONE. This leaves no randomized comparison for estimating what would have happened under another condition. The registry does not report how training exposure was delivered in detail, adherence, concurrent care, or participant-level outcomes; those details should not be inferred from the intervention description.

The record uses both subacute and chronic stroke wording: the official title refers to subacute stroke patients, whereas the primary outcome population and brief summary describe chronic stroke. The registry does not resolve this difference. That ambiguity makes the intended population less clear from the record alone.

Other limitations include the lack of reported analysis methods, analysis population, missing-data handling, multiplicity approach, and sample-size justification for the actual study. The planning illustration described in the registry is not the trial’s single-group design and does not replace a protocol-based justification. Safety reporting is also limited: event definitions and ascertainment are not stated, and deaths are not reported. Together, these gaps restrict assessment of precision, completeness, and the extent to which findings—if available elsewhere—would apply beyond the recorded study participants.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: An Exploratory Clinical Study on a Variable Speed and Sensing Treadmill System (VASST) for Hemiparetic Gait Rehabilitation — NCT01811680.
• Registry record last updated 2015-01-05; status last verified 2015-01.
• Results first posted 2014-12-04.
• 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.

19. Record Summary

The registry record describes a completed Phase 1, single-group feasibility and safety study sponsored by Tan Tock Seng Hospital, with an enrollment of 10. It evaluates supervised treadmill training using the Variable Speed and Sensing Treadmill for gait rehabilitation after stroke. The title refers to subacute stroke, while the primary outcome population is described as chronic stroke.

The primary outcome is the 6 Minute Walk Test in metres, summarized as a mean and standard deviation and assessed at weeks 0, 2, 4 and 8. The registry record does not report numerical outcome results or analyses. It records 0 affected among 10 at risk for serious adverse events and 0 affected among 10 at risk for other adverse events. Deaths are not reported in the registry record.

The design has no separate control group. The posted information permits description of the study structure and specified measurements, but not a quantified estimate of walking-distance change or a comparative conclusion.