Effect of Vibration Exercise on Upper Limb Strength, Function, and Pain: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Effect of Vibration Exercise on Upper Limb Strength, Function, and Pain (NCT02998021), a randomized na study. The primary outcome is Change in Strength.

2. Clinical Question

The study’s stated purpose was to explore whether vibration dumbbell resistance training could improve upper-limb strength, function, and pain compared with standard dumbbell resistance training among manual wheelchair users with paraplegia. The registry identifies change in strength as the primary outcome. It describes this measure as shoulder-adduction peak torque, recorded with the Biodex System and expressed in Nm/kg.

The comparison is clinically framed around two home-based exercise approaches, but the posted primary outcome does not provide a complete between-group comparison. The standard-dumbbell group has no participants in the reported primary outcome, and its numerical result is absent. The registry notes that participants in the control group withdrew before the 12-week visit. It also reports technical problems with strength data for one participant in the intervention group.

Accordingly, the posted data can describe the available strength changes in the vibrating-dumbbell group, but they cannot establish how the groups differed on this endpoint. Results for function and pain are not included among the listed secondary outcomes, and their status is not reported in the registry record.

3. Trial Design

The registry describes a randomized, parallel-group study with no masking. Participants were assigned to resistance training with either a vibrating dumbbell or a standard dumbbell, and each group was to complete an in-home exercise program. The study is marked completed. Its phase is listed as NA.

The registry enrollment is 10. The study start date is 2017-03-15, and the primary completion date is 2018-11-20. Those dates describe the registered study timeline; they do not indicate when individual participants completed their assessments. The allocation-concealment method, details of the randomization sequence, and any stratification are not reported in the registry record.

The primary outcome is change in strength, measured as shoulder-adduction peak torque with the Biodex System. The registry gives the timeframe as baseline and 12 weeks. The available primary-outcome result is for four participants in the vibrating-dumbbell group: a mean change of -4.0 Nm/kg with a standard deviation of 12.4. The comparator group has zero participants contributing a reported value. The registry explains that control participants withdrew before the 12-week visit and that technical problems affected strength data for one intervention participant.

Six secondary outcomes are listed: change in peak speed, change in acceleration, change in peak force, change in mechanical effective force, wheelchair transfer ability, and power output. The record lists 10 outcome measures overall, but the status and numerical results for the other measures are not reported in the registry record. The number of analyses is recorded as zero; whether analyses were conducted but not entered is not reported in the registry record.

The record identifies Alicia Koontz as the sponsor. It does not report masking procedures, a detailed statistical analysis plan, interim analyses, or the rationale used to select the enrollment target.

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:

Analysis population for the primary outcome, as defined in the registry: Subjects in the control group withdrew before the 12 week visit. There were technical problems with collected the strength data for one subject in the intervention group.

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 in Strength, measured over Baseline and 12 weeks.

The primary endpoint is change in strength from baseline to 12 weeks, operationalized as shoulder-adduction peak torque. The registry says the Biodex System was used and gives the unit as Nm/kg. Peak torque represents the maximum rotational force measured during the specified movement; expressing it relative to body mass can provide a scaled measure rather than an unadjusted torque value. That is a general description of the measure, not an additional result from this trial.

Strength is relevant to the study’s stated focus on upper-limb capacity in manual wheelchair users. Shoulder adduction is one specific movement, however, and this endpoint does not by itself represent every aspect of arm strength, everyday function, pain, or wheelchair performance. The listed secondary outcomes include several additional movement or performance measures, but their numerical results are not reported in the registry record.

The posted primary result is a mean change of -4.0 Nm/kg among four participants in the vibrating-dumbbell group, with a standard deviation of 12.4. The standard-dumbbell group has no reported primary-outcome value. The registry does not define the direction used to calculate change, so the negative sign should be quoted as recorded rather than interpreted as a particular increase or decrease. No confidence interval, standard error, or between-group estimate is reported in the registry record.

The endpoint is therefore useful for describing the small set of available intervention-group measurements, but the posted values do not support a complete comparative estimate of strength change between the randomized groups.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

What does a mean change describe?

General: A mean change summarizes the average difference between participants’ measurements at the specified time points, according to the study’s chosen sign convention. It can make a set of individual measurements easier to describe, but it does not show the full pattern of participant-level results. The registry reports a mean change of -4.0 Nm/kg for four participants in the vibrating-dumbbell group. The sign convention is not reported in the registry record, so the value should not be translated into an increase or decrease without that information.

General: The standard deviation describes how spread out observations are around their mean. It is not an estimate of the treatment effect and is not the same as a confidence interval. The reported standard deviation is 12.4. Because the result is based on four participants, both the mean and the observed spread may be sensitive to individual observations. The posted summary does not provide participant-level data with which to assess that pattern.

Why is the missing comparator result consequential?

General: A randomized comparison is generally interpreted by examining outcomes in both assigned groups, using an analysis appropriate to the trial design and missing-data pattern. A value from one group alone cannot show how outcomes differed relative to the other group. In this record, the standard-dumbbell group has no participants contributing a reported primary endpoint, so a between-group estimate cannot be read from the posted values.

The registry says control participants withdrew before the 12-week visit. It also notes technical problems with strength data for one intervention participant. These explanations identify missing outcome information but do not describe a statistical method for addressing it. The handling of missing observations, including whether any imputation or sensitivity analysis was used, is not reported in the registry record.

What does randomization contribute?

General: Randomization is intended to reduce systematic differences between groups at the time of assignment. It does not guarantee that every group will be similar in a small study, nor does it remove problems caused by missing follow-up measurements. The registry identifies the allocation as randomized, but the sequence-generation and allocation-concealment procedures are not reported in the registry record. With no reported primary outcome in the comparator group, randomization alone cannot supply the missing comparison.

How should precision be considered?

General: A confidence interval communicates the range of effect estimates compatible with the data under the statistical model and assumptions used. A narrow interval indicates greater precision than a wide interval, while an interval that spans values of different directions or magnitudes can indicate substantial uncertainty. No confidence interval is reported for the primary outcome. The registry also supplies no between-group estimate or p-value, so comparative precision and statistical evidence cannot be evaluated from the posted primary result.

A p-value, when reported, addresses compatibility between observed data and a specified null hypothesis under a statistical model. It does not measure the size or importance of an effect. No primary-outcome p-value is reported in the registry record. There is also no reported inferential analysis for the primary outcome: the number of analyses is recorded as zero. The record does not clarify whether this means no analyses were conducted or whether analyses were not entered.

What can be said about variability and model choice?

General: Continuous outcomes may be summarized with means and standard deviations when those summaries appropriately describe the data. The registry identifies the primary measure as a mean with standard deviation. It does not report the distribution of individual changes, diagnostics, transformations, or a model specification. Whether the statistical analysis used a particular assumption about normality, baseline adjustment, or repeated measurements is not reported in the registry record.

General: Over-dispersion means that observed variability is greater than a model expects. When present, it can make model-based uncertainty estimates too small if the model does not account for the extra variation. The registry does not report a model or an over-dispersion assessment for this continuous endpoint, so no conclusion about either can be drawn for this trial.

How do planning illustrations differ from observed results?

General: Sample-size planning asks how many participants might be needed under stated assumptions about an effect, variability, allocation, and statistical error rates. A calculation based on an observed effect is an illustrative planning exercise, not evidence about the study’s achieved power and not a substitute for a treatment comparison. The registry’s planning assumptions describe a two-sided significance level of 0.05, equal allocation, a normal approximation, and effects defined as fractions of an observed effect. No numerical planning results are reported in the registry record. The study’s own sample-size justification is also not reported in the registry record.

The enrollment of 10 is the registered study enrollment, not the number contributing to the primary outcome in each group. The endpoint result is based on four intervention-group participants and no comparator participants. Those endpoint counts are the relevant limitation when interpreting the posted primary result; they should not be replaced by a planning calculation.

Overall, the registry provides a concise descriptive summary for one group but does not report the inferential procedures needed to quantify a between-group effect. The absence of a comparator outcome, confidence interval, and p-value leaves the comparative estimate and its precision undetermined in the posted 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("Resistance Training - Vibrating Dumbbell")
n   <- c(4)
m   <- c(-4)
sp  <- c(12.4)
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  Resistance Training - Vibrating Dumbbell  4  -4.000  12.400  -23.731  15.731

11. Multiplicity, Missing Data and Analysis Populations

The registry lists six secondary outcomes and 10 outcome measures overall. Considering multiple outcomes can raise the chance of finding an apparently notable result by chance if many tests are performed. General: Statistical approaches to multiplicity can include adjusting significance thresholds, defining a hierarchy of outcomes, or treating secondary findings as exploratory. The registry does not report a multiplicity strategy, an outcome-testing hierarchy, or inferential results for the secondary outcomes.

The number of analyses is recorded as zero. This means no analyses are listed in the registry record; whether analyses were conducted but not entered is not reported in the registry record. No primary-outcome p-value, confidence interval, or adjusted analysis is reported. Consequently, neither the handling of multiple comparisons nor the statistical evidence for the listed outcomes can be assessed from the posted results.

Missing outcome data are a major interpretive issue. The registry says control participants withdrew before the 12-week visit and notes technical problems with strength data for one intervention participant. The reported primary outcome includes four participants in the vibrating-dumbbell group and zero in the standard-dumbbell group. The record does not describe imputation, reasons for individual withdrawals, sensitivity analyses, or a comparison of participants with and without outcome measurements.

General: An intention-to-treat analysis ordinarily seeks to analyze participants according to their randomized group, while methods for missing outcomes must still be specified. A complete-case analysis uses only participants with observed outcomes and can be vulnerable to bias if observed participants differ systematically from those with missing data. The analysis population and missing-data strategy are not reported in the registry record, so it is not possible to determine which approach was used or how missingness may affect the result.

The registry enrollment is 10, but enrollment should not be confused with the number contributing a reported primary endpoint. The available outcome counts and the absence of a comparator result limit both the comparative analysis and any assessment of how representative the observed participants are.

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 serious adverse events for eight participants at risk in the vibrating-dumbbell group and two participants at risk in the standard-dumbbell group. It reports zero participants affected by serious adverse events in each group. The record also gives zero participants affected by other adverse events in each group, and deaths are reported as zero in both groups.

These figures are event counts as recorded, not estimates that an event is impossible. General: When no events are observed, the data still leave uncertainty about the range of event frequencies that could occur in a larger group or with longer observation. The registry does not report detailed adverse-event terms; the list of top serious-event terms is empty. The duration and completeness of safety follow-up are not reported in the registry record.

The at-risk counts should be read as the denominators recorded for the safety outcomes. The registry enrollment is 10, while the safety denominators differ between groups. The record does not explain the relationship between those denominators, randomization, and the missing primary outcome beyond noting control withdrawals and technical problems with intervention-group strength data. These safety figures describe what was recorded in this study; they do not by themselves establish comparative safety between the exercise programs.

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

The posted primary outcome gives a descriptive result for four participants assigned to vibrating-dumbbell resistance training: mean change in shoulder-adduction peak torque was -4.0 Nm/kg, with a standard deviation of 12.4. It documents the observed summary for those participants and identifies substantial uncertainty about how broadly it can be applied, especially because the sample contributing to the result is small.

The result does not show a comparison with standard-dumbbell training. The comparator group has no reported primary endpoint value because participants withdrew before the 12-week visit. Without an outcome estimate from that group, the posted data do not establish whether the groups differed, how large any difference was, or which direction it might have taken. The sign convention for the recorded change is not reported in the registry record.

The record also does not report a confidence interval, p-value, clinical-importance threshold, analysis population, or method for handling missing outcomes. Those omissions mean that the precision and inferential strength of the primary result cannot be assessed from the registry entry. No numerical results are reported for the six listed secondary outcomes.

General: A result that is uncertain or incomplete is not proof of no effect, just as a numerical change in one group is not proof of a comparative effect. Conclusions about a treatment contrast require relevant information from both groups and an analysis whose assumptions and handling of missing data can be evaluated. The available record does not provide that complete evidence for the primary endpoint.

The record does report no serious adverse events, other adverse events, or deaths among the listed at-risk participants. These observations describe the recorded safety experience in this study, but the small study and unreported follow-up details limit what can be inferred beyond those counts. The findings should therefore be understood as a limited account of the registered outcomes, not as a definitive judgment about benefit or harm.

14. Why This Trial Matters Statistically

This trial illustrates why a randomized design and a complete outcome comparison are separate requirements for interpretation. Random assignment is intended to support a fair comparison, but the primary endpoint is reported for the vibrating-dumbbell group only. With no standard-dumbbell participants contributing a posted strength value, the registry cannot provide a direct comparison of the two training approaches on the primary measure.

The record also demonstrates how follow-up and data-quality issues can affect a trial’s usable evidence. Control participants withdrew before the 12-week visit, and technical problems affected strength data for one intervention participant. Those details are important because the registered enrollment of 10 does not equal the number with an analyzable primary outcome. Clear reporting of outcome counts by group, reasons for missingness, and analysis populations helps readers understand which randomized participants contribute to a result.

Precision is another central statistical issue. The intervention-group mean and standard deviation are reported, but no confidence interval or comparative estimate is available. A point estimate alone cannot convey the range of uncertainty around a treatment contrast. In small studies, uncertainty can be substantial, and the absence of a comparator result makes that uncertainty impossible to quantify as a between-group effect.

The registry lists multiple secondary outcomes but does not report their numerical results or a multiplicity approach. Prespecifying which outcomes are primary, explaining how multiple tests are handled, and reporting results transparently are important for distinguishing planned comparisons from exploratory observations. Here, the listed outcomes provide context for the study’s scope, but not additional evidence about results.

These statistical features matter because they determine what readers can conclude from a trial record. The available primary summary is informative as a description of four observations, while the missing comparator data and unreported inferential methods leave the central comparative question unresolved in the posted results.

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.

Several limitations are specific to the information recorded for this study. The primary strength outcome is available for four participants in the vibrating-dumbbell group and none in the standard-dumbbell group. The registry attributes the absent control-group values to withdrawal before the 12-week visit and notes technical problems with strength data for one intervention participant. These missing results prevent a posted between-group estimate for the primary endpoint.

The reported intervention-group mean and standard deviation summarize a small set of observations. No participant-level data, confidence interval, standard error, p-value, or inferential comparison is reported in the registry record. The direction convention for change and the criterion for clinically important change are also not reported in the registry record. These gaps limit interpretation of both the numerical sign and the precision or practical importance of the result.

The registry lists 10 outcome measures and six secondary outcomes, but numerical secondary results are not reported in the registry record. The number of analyses is recorded as zero, and it is not reported whether analyses were conducted but not entered. The statistical plan, analysis population, allocation-concealment method, missing-data strategy, and multiplicity approach are not reported in the registry record.

The study is described as unmasked, but the record does not specify whether outcome assessors were masked. It also does not report a sample-size justification, detailed adherence information, or the completeness and duration of safety follow-up. These points should not be assumed either way. Together, the incomplete outcome reporting and missing comparator data restrict what can be inferred from the registry entry.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: Effect of Vibration Exercise on Upper Limb Strength, Function, and Pain — NCT02998021.
• Registry record last updated 2019-12-23; status last verified 2019-12.
• Results first posted 2019-12-23.
• 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

This completed randomized, parallel-group study compared in-home vibrating-dumbbell resistance training with standard-dumbbell training for manual wheelchair users with paraplegia. The registry lists an enrollment of 10 and no masking. The primary endpoint was change from baseline to 12 weeks in shoulder-adduction peak torque, measured with the Biodex System in Nm/kg.

The posted primary result is a mean change of -4.0 Nm/kg with a standard deviation of 12.4 among four participants in the vibrating-dumbbell group. No primary endpoint value is reported for the standard-dumbbell group; the registry notes withdrawals before the 12-week visit and technical problems with strength data for one intervention participant. No inferential comparison is reported.

Six secondary outcomes are listed, but their numerical results are not reported in the registry record. The safety record reports zero serious adverse events, zero other adverse events, and zero deaths in both groups. The missing comparator outcome and limited intervention-group observations are central to interpreting the available results.