High Intensity Training for Neurological Injury Using Overground Exoskeletons in Inpatient Rehabilitation: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for High Intensity Training for Neurological Injury Using Overground Exoskeletons in Inpatient Rehabilitation (NCT04973852), a na na study. The primary outcome is Percentage of Heart Rate Readings Within the Target Zone Achieved During HIT Gait Training Session.

2. Clinical Question

3. Trial Design

This completed study is registered as a single-group device study of the Ekso wearable exoskeleton for overground ambulation. The registry lists an enrollment of 11, phase NA, allocation NA, and no masking. Its sponsor is The University of Texas Health Science Center, Houston. The recorded study start is 2021-10-06, and the primary completion date is 2023-05-25.

The intervention description specifies 5 overground walking sessions with the wearable exoskeleton, with heart rate monitored over each session. The registry summary also describes two assessment sessions: one before and one after the training sessions. Those visits include seated balance, walking speed and endurance tests, and breathing assessments. The primary heart-rate outcome is measured during session 1, with its timeframe described as about day 2.

The design does not include a concurrent comparison group. Consequently, the record does not define a randomized contrast or a between-group treatment effect. Changes measured before and after training could be described over time, but the registry record does not report an analysis that separates any such changes from other explanations.

The registry lists 18 outcome measures and 0 analyses. It does not report the primary endpoint estimate or a statistical analysis plan in the record. The study status is completed, but completion alone does not establish what results were observed or how 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.

Overall Study

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: Baseline characteristics are reported for all who completed the study

6. Primary Endpoint

The registry lists the primary outcome as Percentage of Heart Rate Readings Within the Target Zone Achieved During HIT Gait Training Session, measured over During session 1 (about day 2).

The primary endpoint is the percentage of heart-rate readings that fall within a target zone during the first high-intensity gait training session. Heart rate is described as monitored continuously and recorded every 5 minutes throughout a session lasting about 60 minutes. The target zone is defined as 70–80% of heart-rate reserve. Heart-rate reserve is the difference between maximum heart rate and resting heart rate; the record describes estimating maximum heart rate from age and using the Karvonen formula to set the target range.

This measure is intended to assess whether participants reached the specified cardiovascular intensity while walking in the exoskeleton. Expressing the outcome as a percentage of readings within the zone gives a within-session summary of how often the recorded heart rate met the target, rather than a measure of walking speed, endurance, or change in walking ability.

The registry identifies the outcome as a mean with standard deviation. These statistics would describe the average percentage across participants and the spread of participant-level values. The endpoint value and its standard deviation are not reported in the registry record, so the degree to which the target was reached cannot be assessed from the posted results.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The registry describes a single-group study with a continuous primary outcome. Understanding what such an outcome can show depends on separating the measurement definition, the summary statistic, and the design used to interpret the result.

What does the primary outcome summarize?

For each participant, the endpoint is the percentage of heart-rate readings within the 70–80% heart-rate-reserve target during session 1. A participant-level percentage condenses the recorded readings from that session into one value. The registry specifies that the group result is to be expressed as a mean and standard deviation. In general, a mean describes the average across participant-level values, while a standard deviation describes how dispersed those values are around the mean. Neither statistic is reported for this endpoint in the registry record.

The readings occur repeatedly within a session for each participant. In general, repeated readings from the same person are related rather than independent observations. Treating every reading as if it came from a different person can give an overly precise impression of the evidence. The endpoint’s percentage is a participant-level summary, but the registry record does not describe the analysis details used to construct or analyze it.

What can a confidence interval tell a reader?

In general, a confidence interval describes the uncertainty around an estimated quantity under the assumptions of the statistical method. A narrower interval indicates greater precision for that estimate, while a wider interval indicates less precision. An interval does not correct for a biased design, missing data, or an unsuitable analysis. The registry record does not report a confidence interval for the primary endpoint.

A standard deviation and a confidence interval answer different questions. The standard deviation describes variability among participant-level observations; a confidence interval would describe uncertainty about an estimated group quantity. One cannot be substituted for the other. No inferential analysis for the primary measure is listed in the registry record.

How does the design affect interpretation?

In general, a single-group study can describe what was observed among participants receiving the intervention. It cannot directly estimate a contrast against a concurrent control group when no such group is included. A pre-training and post-training comparison, if reported, would describe change over time in the measured participants. Without a control group, that change alone would not establish that the intervention caused it.

The endpoint is measured during the first training session, not as a comparison between baseline and a later session. It is therefore a session-specific intensity measure. The record’s other planned assessments address balance, gait, endurance, and breathing, but their presence does not change the meaning of the primary outcome.

What do the planning assumptions mean?

The registry describes sample-size calculations as planning illustrations based on an observed effect, not as the trial’s own design. The stated assumptions include a two-sided significance level of 0.05, equal allocation between two arms, a normal approximation, and effects defined as fractions of the observed effect. The registry also states that non-time-to-event illustrations are expressed as participants per arm.

These assumptions describe hypothetical planning for a two-arm study, whereas this trial is registered as single-group. The illustrations are not observed power, do not report the probability that this completed study detected an effect, and do not establish that the study was designed around those assumptions. Because the registry record does not report the primary endpoint estimate, the observed effect underlying such planning cannot be evaluated from the primary outcome information.

What is not specified?

The registry record does not report the statistical analysis plan, the method used to handle missing observations, the analysis population, or any interim analyses. These details matter because analysis choices can affect which observations contribute to an estimate and how uncertainty is calculated. Their absence from the registry record means that the reader cannot determine whether or how those decisions were made; it does not establish that no such decisions were made outside the record.

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("Exoskeleton")
n   <- c(6)
m   <- c(72.67)
sp  <- c(11.43)
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  Exoskeleton  6  72.670  11.430  60.675  84.665

11. Multiplicity, Missing Data and Analysis Populations

The registry lists 18 outcome measures, including the primary heart-rate outcome and secondary measures involving seated dynamic reach and spatial-temporal gait parameters. The listed gait measures include step length, stride length, single support, double support, swing time, stance time, and heel-to-heel base of support time. The record lists 0 analyses and does not report results for these outcomes.

When a study examines multiple outcomes or makes multiple statistical comparisons, the chance of a chance finding can increase. In general, a prespecified multiplicity strategy can address that issue, but the registry record does not report whether any adjustment or other strategy was planned. The statistical analysis plan is not reported in the registry record, so the intended hierarchy among outcomes and comparisons cannot be assessed beyond the designation of the primary outcome.

Missing-data handling is not reported in the registry record. The record also does not report the analysis population or how many participants contributed data to each outcome. The registered enrollment of 11 should therefore not be assumed to be the denominator for every outcome or analysis.

The record does not describe whether all participants completed every session, whether all scheduled measurements were obtained, or how incomplete observations were handled. These points are relevant to interpreting any outcome estimate, but the posted results do not provide the necessary details. No conclusion about the impact of missing data or multiplicity can be drawn from the registry record.

12. Safety Results

The registry reports serious adverse events as affected participants divided by participants at risk.

Deaths

Other (non-serious) adverse events

Participants with at least one non-serious event at or above the registry's 0% reporting threshold.

The registry reports 0 serious adverse events among 11 participants at risk in the Exoskeleton group. It also reports 0 other adverse events among 11 participants at risk and 0 deaths. No top serious adverse-event terms are listed.

These figures describe the events recorded in the registry for the stated group and at-risk counts. They are not evidence that no adverse events could occur, and they do not establish a rate for other populations or settings. The record does not report additional details such as event timing, duration, severity categories beyond the serious-versus-other classification, or participant-level circumstances. The safety counts should be interpreted as registry-reported observations, not as proof of absence of risk.

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

The study addresses whether people with spinal cord injuries can reach a specified heart-rate intensity while walking in an overground exoskeleton. Its primary outcome is the percentage of recorded heart-rate readings within the target zone during session 1. The registry record describes how that outcome was defined, but does not report its observed value or variability. The posted results therefore do not show whether participants reached the target zone.

The study also planned to evaluate walking ability and other measures, including seated balance and gait parameters, with assessments before and after training. Those measures could describe changes over the training period if results were reported. The registry record does not report those outcome results, so it does not establish whether any measured walking or balance outcome changed.

Even if a before-and-after change were reported, the single-group design would not provide a concurrent control comparison. A change over time would not, by itself, establish that the exoskeleton training caused it. The absence of masking, recorded as none, is another design feature to consider when interpreting assessments, particularly outcomes involving measurement or judgment. The record does not describe additional safeguards or analysis details.

The enrollment of 11 and the reported zero event counts are relevant descriptive details, but they do not replace an endpoint estimate or resolve uncertainty about outcomes. The registry record is completed, yet completion does not mean that results are available in the record. The defensible interpretation is limited to the study’s design, planned measurements, and the safety counts that were posted. Claims about efficacy, comparative benefit, or causal effects are not supported by the reported information.

14. Why This Trial Matters Statistically

Statistically, the study highlights the distinction between feasibility-related measurement and clinical change. Its primary endpoint records how often heart rate falls within a prespecified intensity zone during an exoskeleton walking session. That is a direct summary of the session’s heart-rate readings, but it is not the same construct as walking speed, endurance, or improvement in functional mobility.

The repeated monitoring is also relevant. Heart-rate readings are collected at intervals within a session, so readings from the same participant are generally related. In general, statistical analyses should account for the participant as the source of repeated measurements rather than treating every reading as independent evidence. The registry specifies a participant-level percentage and a mean with standard deviation, but does not report the analysis details or results.

The single-group design makes descriptive interpretation central. It can characterize observations among participants who received the intervention, but it does not provide a concurrent control contrast. This distinction matters when interpreting any apparent change in the additional pre- and post-training assessments: a change over time is not, by itself, proof that training produced it.

The record also illustrates why registration details and posted results are separate. It identifies the primary measurement, intervention, timing, and planned secondary outcomes, while not reporting the primary estimate or listed analyses. Without those results, readers cannot assess the observed intensity measure, its variability, or the precision of an estimate. The methodological value of the record is therefore chiefly in clarifying the question and the limits of what can be concluded from the information reported.

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 study is the absence of a reported primary endpoint estimate. Although the record defines the target-zone measure and identifies its timing, it does not give the observed mean or standard deviation. The registry lists 0 analyses, so the posted record does not provide an inferential result for the primary outcome.

The single-group design has no concurrent control arm, and allocation is recorded as NA. Any change in the pre- and post-training assessments, if observed, could not be separated from other changes over time using a randomized between-group comparison. Masking is recorded as none, which is relevant when considering outcomes that involve assessment.

The registry records enrollment of 11, but does not report the analysis population, completion of each training or assessment session, or the number contributing to each outcome. Handling of missing data and the statistical analysis plan are not reported in the registry record. The record also does not provide further participant characteristics or eligibility details, limiting assessment of how well the enrolled group represents other people with spinal cord injuries.

The primary endpoint is specific to heart-rate readings during session 1. It does not establish sustained intensity across all training sessions or directly measure a change in walking ability. Although the registry lists 18 outcome measures, it does not report an approach to multiplicity. These limitations constrain interpretation of both the planned outcomes and any broader implications.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: High Intensity Training for Neurological Injury Using Overground Exoskeletons in Inpatient Rehabilitation — NCT04973852.
• Registry record last updated 2026-04-15; status last verified 2025-02.
• Results first posted 2026-04-15.
• 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

NCT04973852 is a completed, single-group device study sponsored by The University of Texas Health Science Center, Houston. It enrolled 11 participants with spinal cord injuries and evaluated 5 sessions of overground ambulation using the Ekso wearable exoskeleton. Allocation is recorded as NA and masking as none.

The primary outcome is the percentage of heart-rate readings within the 70–80% heart-rate-reserve target during session 1, identified as about day 2. The registry also describes pre- and post-training assessments and lists secondary balance and gait outcomes. It records 18 outcome measures and 0 analyses.

The registry record does not report the primary endpoint result, the statistical analysis plan, the analysis population, or missing-data methods. It reports 0 serious adverse events, 0 other adverse events, and 0 deaths in the Exoskeleton group, with 11 at risk for each adverse-event category.