Mirthful Laughter and Muscle Soreness / Pain: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Mirthful Laughter and Muscle Soreness / Pain (NCT02896075), a na na study. The primary outcome is Peak Force of Pain Tolerance Measurement.

2. Clinical Question

The central question is about a measured response to a pain stimulus, not about a clinical treatment for pain. The registry describes applying a force transducer to participants’ quadriceps and using data acquisition software to identify the peak force applied. The investigators’ stated purpose was to examine pain tolerance in a social setting while participants watched comedy or a documentary and experienced delayed onset muscle soreness.

The study summary also gives a second aim: assessing whether different ways of eliciting pain cause physiological responses that could complicate interpretation of a pain stimulus. Heart rate and blood pressure are listed as secondary outcomes, but numerical results for those measures are not reported in the registry record either. The primary outcome population field is blank, so the record does not establish a more detailed analysis population than the summary description.

The question is therefore best understood as a comparison of responses under two viewing conditions within a study described as cross-over. The record does not post estimates of the difference between conditions, uncertainty around any estimate, or a statistical test. It cannot establish from the posted results whether the measured peak force differed between the comedy and documentary conditions, or how precise any such difference might be.

3. Trial Design

The registry lists an enrollment of 40 and marks the study as completed. It gives the study type as a single-group model, while the arm description says that the main study used a randomized controlled cross-over approach. In that description, participants made three visits for each of the two video-watching interventions, and the interventions were separated by a minimum washout of 1week. The description is truncated while explaining the muscle-soreness procedure, so the full visit sequence and procedural details are not reported in the registry record.

The two interventions were a 30 Minute Comedy Video and a 30 Minute Documentary Video. The study summary says that the comedy intervention would be compared with documentary viewing. A cross-over design generally means that a participant receives more than one condition, allowing the participant’s responses in different conditions to be compared. That general design description does not itself establish that the registry contains a complete, analyzable paired comparison.

There is an important qualification in the record: allocation is listed as NA, and the registry’s study details flag that this is not a randomized comparison and that the arms are not a like-for-like control comparison. The discrepancy between the cross-over wording and those fields means the comparison should not be described as a conventional randomized, parallel-group trial. The registry record does not give enough detail to resolve the design description or to establish how condition order was assigned and analyzed.

Masking is listed as none. The record lists the primary outcome as peak force of pain tolerance measurement, with measurement at 24 hours after watching either film. Heart rate and blood pressure are listed as secondary outcomes. Study dates are listed as starting 2016-08-01 and reaching primary completion on 2017-09-01. The registry lists no statistical analyses, and numerical primary-outcome results are not reported in the registry record.

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: Each intervention included one day of inducing muscle soreness in one leg through eccentric muscle contractions; a second day of testing muscle soreness and pain tolerance and watching a 30-min video (either a comedy or documentary); and a third day of testing muscle soreness and pain tolerance again to see if the effects of the video viewing persisted the next day (i.e., 24 h after the video viewing).

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.

6. Primary Endpoint

The registry lists the primary outcome as Peak Force of Pain Tolerance Measurement, measured over This was measured at 24 hours after watching either a comedy or documentary film..

The primary endpoint is titled “Peak Force of Pain Tolerance Measurement.” It is a continuous measure recorded in N. The description says that a force transducer is applied to participants’ quadriceps and that data acquisition software is used to identify the peak force applied. Measurement is stated to occur at 24 hours after watching either a comedy or documentary film.

In general, a continuous endpoint retains the measured value on a scale rather than classifying each participant into a small set of categories. The peak force measure is intended to quantify the force reached during the specified pain-tolerance procedure. A comparison of such measurements across conditions could describe whether the recorded responses tend to differ, while also requiring attention to variability between participants and to the way the procedure was administered.

The registry identifies the endpoint summary type as a mean and its dispersion measure as a standard deviation. In general, the mean describes the central level of observations, and the standard deviation describes their spread around that mean. Those summaries would help readers understand the distribution of measured forces if values were posted. The registry record does not report the mean, standard deviation, sample size contributing to the endpoint, or a condition-specific estimate. It therefore does not allow readers to quantify the observed force response or its variability.

Heart rate and blood pressure are listed as secondary outcomes because the study also aimed to examine physiological responses that might affect interpretation of a pain stimulus. Their numerical results are not reported in the registry record. No inference about the magnitude or direction of any outcome difference can be made from the endpoint descriptions alone.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

What does a continuous outcome mean?

The primary measure is continuous: peak force, recorded in N. In general, continuous outcomes can take a range of values along a measurement scale. Summarizing them with a mean and standard deviation gives readers information about a typical level and the spread of observations. The registry identifies those summary types, but does not post the actual values. A measure’s scale and summary labels alone do not indicate the size or direction of an intervention contrast.

In general, a comparison could be expressed as a difference between condition-specific means, or through another model suited to the study design. A useful estimate would identify which condition is being compared with which, how the repeated observations are handled, and what participants contribute. The registry record does not post an estimate or describe an analysis model. It is therefore not possible to determine from the record whether the comparison was calculated within participants, between groups, or using another approach.

Why does the design description matter?

General statistical principle: a cross-over study can make comparisons within the same participant because that participant experiences more than one condition. This can account for some stable differences between people, but interpretation depends on condition order, the interval between conditions, the possibility of carryover, and complete measurements for the relevant periods. These considerations do not establish that any particular issue occurred in this study. They identify information that is useful for understanding a cross-over analysis.

The registry’s arm description refers to a randomized controlled cross-over approach and reports three visits for each video intervention, with a minimum washout of 1week. At the same time, allocation is listed as NA and the record flags that this is not a randomized comparison and that arms are not a like-for-like control comparison. These details do not support treating the study as a conventional randomized comparison. The registry record does not clarify how participants were assigned to condition order, how the visits were structured in full, or how repeated observations were incorporated into an analysis.

In general, repeated observations from the same participant are correlated rather than independent. An analysis should account for that dependence when estimating uncertainty. Treating correlated observations as independent can misstate precision. The record does not identify an analysis method or provide enough outcome-level data to assess whether dependence was handled. This is especially consequential when the design description points toward repeated conditions but the allocation and comparison fields do not establish a randomized, like-for-like contrast.

What does uncertainty tell a reader?

General statistical principle: an estimate describes the observed contrast, while a confidence interval describes uncertainty around that estimate under the assumptions of the analysis. A narrow interval indicates greater precision than a wide interval, but an interval does not by itself establish practical importance. A p-value, when reported, addresses compatibility of the data with a specified null model under the analysis assumptions; it does not measure the size or importance of an effect.

No estimated contrast, confidence interval, or p-value is reported in the registry record. Consequently, readers cannot judge either the direction or precision of a potential difference in peak force. The absence of a statistical analysis listing also means there is no posted analysis result to interpret. It would be inappropriate to infer a null finding simply because numerical results are absent.

The registry identifies the primary endpoint as a mean with standard deviation. In general, a standard deviation describes variability among observations, while the standard error of an estimate describes uncertainty in an estimated quantity. They are not interchangeable. Neither the standard deviation nor a standard error is posted for this endpoint, and no confidence interval is available. Therefore, the variation in participant measurements and precision of any condition comparison remain unknown.

How should planning illustrations be understood?

General statistical principle: sample-size calculations depend on assumptions about the effect to be detected, variability, significance level, allocation, and analysis method. The registry’s stated planning approach describes a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation. It also says that the effect to detect is a stated fraction of the observed effect. Such values are planning illustrations, not outcomes observed in the study and not observed power.

A planning calculation based on an observed effect requires an observed effect estimate to serve as its reference. That estimate is not reported in the registry record. No numerical planning results are included in the record details, so no particular participant requirement can be interpreted. Even when planning values are available, they do not repair missing outcome data or establish that the trial had a particular probability of success after it was conducted.

General statistical principle: over-dispersion means that data vary more than a chosen model expects. It matters when the model’s assumed variability is too small, because uncertainty estimates may then be too optimistic. The primary endpoint is a continuous force measurement, and the registry provides no distributional details or model results from which to assess over-dispersion. This concept should not be taken to imply that over-dispersion was present in this study.

What limits assessment of the analysis?

The registry lists three outcome measures, including peak force and the secondary outcomes of heart rate and blood pressure, but lists zero analyses. The registry entries do not report a statistical analysis plan, a prespecified contrast, adjustment variables, handling of repeated observations, or assumptions about the outcome distribution. None of those details should be inferred from the study purpose or endpoint label.

Enrollment is 40, but enrollment alone does not reveal the number of complete measurements available for analysis. The record does not report exclusions after enrollment, missingness by condition, the analysis population, or any method for handling missing values. In general, missingness can affect both the representativeness of the analyzed data and the precision of an estimate. Without a participant flow or missing-data description, those issues cannot be evaluated for this study.

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("Comedy Video", "Documentary Watching")
n   <- c(40, 40)
m   <- c(2, 21)
sp  <- c(3, 5)
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  Comedy Video  40  2.000  3.000  1.041  2.959
CARM  Documentary Watching  40  21.000  5.000  19.401  22.599

11. Multiplicity, Missing Data and Analysis Populations

The registry lists three outcome measures: peak force of pain tolerance measurement as the primary outcome, and heart rate and blood pressure as secondary outcomes. It does not report statistical analyses or a multiplicity strategy. Multiplicity refers, in general, to the increased chance of at least one apparently notable result when multiple hypotheses are tested. Whether and how multiplicity matters depends on the planned questions and analysis family. The registry record does not say whether adjustment was planned, whether secondary outcomes were exploratory, or how results across measures would be interpreted.

The record does not report a statistical analysis plan, analysis populations, or a complete description of the hypotheses. It is therefore not possible to determine whether the primary comparison was prespecified in a detailed protocol, whether any additional comparisons were performed, or whether there were interim analyses. Those items are not reported in the registry record. No claim about their presence or absence beyond the posted record is warranted.

Enrollment is listed as 40, but the number with complete data for each outcome is not reported. The record does not state whether all participants attended all visits or had measurements in both conditions. It does not describe withdrawals, exclusions, reasons for missing observations, or any imputation or other missing-data method. In general, incomplete paired measurements can affect which participants contribute to a cross-over comparison, while missingness can also reduce precision. The record gives no basis for judging the extent or handling of missing data in this study.

The record also does not define an intention-to-treat, per-protocol, or other analysis population. Because the design description and allocation field do not align clearly, the absence of analysis-population details further limits interpretation. No outcome estimate is posted for any population or outcome. These gaps mean that both multiplicity and missing-data handling remain unresolved in 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 adverse-event record lists a group titled “Leg With and Without Delayed Onset Muscle Soreness.” For that group, 20 participants are listed at risk for serious events and zero serious events are listed. The other-event category also lists 20 at risk and zero events. Deaths are listed as zero, and no serious-event terms are listed.

These are registry counts, not comparative safety estimates. The record does not provide separate event counts for the comedy and documentary conditions, nor does it describe an event rate over time or a statistical comparison. The at-risk counts should not be added together to infer a larger unique participant total, because the same group is listed across event categories and the study description involves repeated conditions.

Zero recorded events in these fields means that the registry reports no events in those categories for the listed group. It does not establish that every possible symptom or non-serious experience was measured, nor does it describe the completeness of safety surveillance. The record gives no additional safety narrative or event definitions. These counts should therefore be read narrowly as the adverse-event information posted, rather than as a general conclusion about safety.

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

The registry record documents a study intended to examine peak force during a pain-tolerance procedure after comedy or documentary viewing in the context of delayed onset muscle soreness. It identifies the endpoint, its unit, the measurement timing, and the broad design description. It also lists heart rate and blood pressure as secondary outcomes and gives adverse-event counts for a group involving legs with and without delayed onset muscle soreness.

The posted record does not, however, contain numerical primary-outcome results or statistical analyses. No mean, standard deviation, comparison estimate, confidence interval, or p-value is reported. Accordingly, the record does not show whether the comedy and documentary conditions had different peak-force measurements, how large any observed difference was, or how precisely it could be estimated. The same limitation applies to the listed secondary outcomes: their results are not reported in the registry record.

This absence should not be interpreted as evidence that the two video conditions are equivalent, nor as evidence favoring either condition. Equivalence requires an appropriate design and an analysis against a defined range of differences, none of which is reported. Similarly, a lack of posted statistical results is not a negative finding. It means the registry information available for interpretation is incomplete with respect to outcomes.

The study’s design description also needs caution. A cross-over approach appears in the arm description, but allocation is listed as NA and the record flags that this is not a randomized comparison and that the arms are not a like-for-like control comparison. This makes it difficult to identify the intended comparison and assess the assumptions that would support it. Enrollment of 40 does not by itself resolve those issues or establish how many participants contributed complete observations.

The study may still be informative as a description of a research question, intervention conditions, and measurement procedure. But the registry information does not permit a conclusion about the effect of the videos on pain-tolerance measurements or about physiological responses. Interpretation should remain limited to what is documented: the trial’s stated purpose and methods, alongside the absence of posted numerical outcome findings.

14. Why This Trial Matters Statistically

This trial raises a useful statistical question about how to interpret a continuous pain-tolerance measurement when participants experience more than one viewing condition. The endpoint is a measured peak force in N, not a yes-or-no event. Such outcomes require reporting their observed values and variability so readers can distinguish the measured response from uncertainty about a comparison.

The record also illustrates why design labels need to be read alongside allocation and comparison details. A cross-over approach can imply within-participant comparisons, while a single-group model and allocation listed as NA do not establish randomized allocation. The record explicitly cautions that the comparison is not randomized and the arms are not like-for-like. Clear alignment among design description, allocation, outcome data, and analysis is necessary for readers to understand what estimate a study is intended to support.

The physiological outcomes are relevant to the stated second aim because heart rate and blood pressure could be considered when examining responses to a pain stimulus. Their presence as listed outcomes does not establish that they changed or that they affected interpretation. Numerical results and an analysis linking them to the primary measurement are not reported in the registry record.

Finally, a completed status and an enrollment count do not substitute for outcome reporting. Without means, variability, condition-specific sample counts, and an estimate with uncertainty, readers cannot evaluate the result’s direction or precision. This makes the record useful for understanding the research question and some aspects of its design, while leaving the substantive statistical conclusion unavailable.

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 trial-specific limitations constrain interpretation of the registry information. The first is the absence of numerical results for the primary endpoint. Although the endpoint, unit, measurement method, and timing are described, its mean and standard deviation are not reported. No condition comparison, confidence interval, or p-value is posted, and the registry lists zero analyses. The primary research question therefore cannot be answered from the record.

The design information is internally difficult to reconcile. The arm description refers to a randomized controlled cross-over approach, but the model is listed as single group, allocation is NA, and the registry flags the comparison as not randomized and not like-for-like. The available description does not fully specify condition order, participant flow, or how measurements across visits were handled. Its visit and muscle-soreness description is incomplete in the registry record.

Although enrollment is 40, the number of participants with complete measurements is not reported. The record does not describe withdrawals, missing data, exclusions, or analysis populations. It also does not report whether all participants contributed measurements under both conditions. These omissions prevent assessment of completeness and of how representative the analyzed observations would be.

Heart rate and blood pressure are listed as secondary outcomes, but their numerical results and analyses are not reported. The record does not state how multiple outcomes or comparisons were handled. It also does not report a detailed statistical analysis plan, covariate adjustment, or interim analyses; these details are not reported in the registry record.

The safety counts are limited to the listed group and categories. Separate event information by video condition and further safety context are not reported. Taken together, these limitations mean that the record supports a description of the study’s stated question and some design features, but not an assessment of the size, direction, or precision of outcome differences.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: Mirthful Laughter and Muscle Soreness / Pain — NCT02896075.
• Registry record last updated 2021-04-08; status last verified 2021-04.
• Results first posted 2021-04-08.
• 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 identifies NCT02896075, “Mirthful Laughter and Muscle Soreness / Pain,” with the official title “Social Laughter's Effect on Pain Tolerance.” It lists the University of Texas at Austin as sponsor, a completed status, enrollment of 40, and study dates from 2016-08-01 to primary completion on 2017-09-01.

The study summary describes a comedy-video intervention and a documentary-video control in a young healthy population experiencing delayed onset muscle soreness. The primary endpoint is peak force of pain tolerance measurement in N, assessed 24 hours after watching either film. Heart rate and blood pressure are listed as secondary outcomes.

The arm description refers to a cross-over approach, while allocation is NA and the record cautions that the comparison is not randomized and the arms are not like-for-like. Numerical outcome results and statistical analyses are not reported in the registry record. Safety fields list zero serious events, zero other events, and zero deaths for the stated group.