An Evaluation of the Energy Expenditure From Wii Fit Games: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for An Evaluation of the Energy Expenditure From Wii Fit Games (NCT01561716), a randomized na study. The primary outcome is Energy Expenditure.

2. Clinical Question

3. Trial Design

This was a completed, randomized crossover study with 30 enrolled healthy young adults. In a crossover design, participants take part in more than one condition, so comparisons can use measurements from the same people across conditions. The registry lists six crossover sequences, which differ in the order of resting, Wii Fit Free Run, Wii Fit 3 bouts, and treadmill activity. Allocation was randomized and masking was listed as none.

The primary outcome was continuous energy expenditure, expressed in METs. The registry describes 30 min of continuous monitoring at rest and during each physical activity. The listed measurement method was computerized open-circuit indirect calorimetry, using oxygen consumption and carbon dioxide production and converting the measurements to METs.

The posted outcome summaries include rest, Wii Fit Free Run, Super Hula Hoop, Advanced Steps, Rhythm Boxing, and Treadmill Running/Walking, with 30 participants listed for each. The sequence descriptions do not list Super Hula Hoop, Advanced Steps, or Rhythm Boxing; how those activity summaries map onto the sequences is not reported in the registry record. The registry also does not explain how each participant’s repeated measurements were handled in the reported comparisons.

The study started in 2009-09, had primary completion in 2010-04, and is recorded as completed. Its phase is listed as NA. Details such as eligibility criteria beyond healthy young adults, the original sample-size justification, and the prespecified statistical analysis plan are not reported in the registry record. The posted results contain one primary outcome measure and no secondary outcomes.

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 participant was assigned to a crossover sequence based on a computer generated randomization schedule using SAS 9.2. A washout period of at least 24 hours separated each study session.

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.

Only the first 6 of 7 groups are shown.

6. Primary Endpoint

The registry lists the primary outcome as Energy Expenditure, measured over 30 min continuous monitoring at rest and during each physical activity.

The primary endpoint was energy expenditure, reported as a mean in metabolic equivalents, or METs. The registry describes continuous, computerized open-circuit indirect calorimetry: oxygen consumption and carbon dioxide production were measured and converted to METs. Monitoring was listed as 30 min at rest and during each physical activity.

METs provide a common scale for describing energy expenditure across resting and activity conditions. The endpoint therefore allows the registry to report a mean value for rest, each named Wii Fit activity, and treadmill walking/running in the same units. The reported means range from 0.9 METs at rest to 8.0 METs for Treadmill Running/Walking, with the Wii Fit activity means between 3.8 and 5.0 METs.

The standard deviations describe variation in the measured values among participants for each condition. They do not describe how consistently each individual changed from rest to activity, which would require within-person information. The registry does not report additional details about the endpoint’s calculation, quality control, or how repeated measurements were summarized. Nor does it report a separate endpoint definition for the Wii Fit 3 bouts condition.

7. Results Posted in the Registry

• Wii Fit Free Run: mean 5.00 versus 0.90 on control; difference 4.10 (95% CI 3.60 to 4.60), standardized effect d = 4.13; z-test p = <0.001.
• Wii Fit Super Hula Hoop: mean 3.90 versus 0.90 on control; difference 3.00 (95% CI 2.53 to 3.47), standardized effect d = 3.25; z-test p = <0.001.
• Wii Fit Advanced Steps: mean 3.80 versus 0.90 on control; difference 2.90 (95% CI 2.18 to 3.62), standardized effect d = 2.05; z-test p = <0.001.
• Wii Fit Rhythm Boxing: mean 4.10 versus 0.90 on control; difference 3.20 (95% CI 2.88 to 3.52), standardized effect d = 5.00; z-test p = <0.001.

8. Statistical Interpretation

9. Statistical Methods Explained

The registry identifies a randomized crossover design and reports means and standard deviations for a continuous endpoint. A crossover design differs from a parallel-group design because the same participant can contribute measurements under more than one condition. Such repeated measurements are related: a participant’s values across conditions may be more alike than values from different participants. A paired or repeated-measures analysis can use that relationship. The registry record does not report whether the sponsor’s analysis used such a model, nor does it report a model for sequence or measurement period.

What does a mean difference describe?

A mean difference expresses the distance between two condition means in the endpoint’s units. The posted comparisons use rest as the reference and report differences in METs. For example, the reported mean difference for Wii Fit Free Run is 4.1 METs, based on a rest mean of 0.9 and an activity mean of 5.0. A positive difference means that the activity mean is higher than the reference mean in the posted summary. The estimate alone does not explain individual responses or establish why the group means differ.

The comparisons are labeled as recalculated and are simple unadjusted calculations from the posted summary statistics. They are not reported as the sponsor’s original inferential analysis. Because this trial used a crossover design, a calculation using only condition-level means and standard deviations cannot represent the within-participant pairing unless the required paired information is incorporated. No paired correlation or participant-level data are reported. Thus the recalculated results provide a useful summary of the posted means, but they are not a substitute for a reported analysis that models the repeated measurements.

What do standard deviations and confidence intervals add?

A standard deviation describes the spread of participant measurements around a condition mean. It is not the uncertainty in the mean itself. For instance, the posted standard deviation is 2.0 METs for Advanced Steps and 0.9 for Rhythm Boxing, indicating different observed spreads in those conditions. A confidence interval instead describes uncertainty around an estimated difference under the assumptions of the calculation. Narrower intervals indicate greater precision in that estimate; wider intervals indicate more uncertainty. Neither measure describes the full range of possible responses for an individual.

The posted comparisons include confidence intervals and unadjusted p-values. A p-value is a measure of how incompatible the observed data are with a specified null model, if that model and its assumptions hold. It is not the probability that the null hypothesis is true, and it does not measure the importance of an effect. The reported p < 0.001 values should therefore be interpreted alongside the mean differences, intervals, design, and limits of the available analysis information.

Why does the crossover structure matter?

In a crossover study, order can matter if measurements differ by sequence or period, or if one condition affects a later measurement. Randomizing the sequence can help distribute order effects, but randomization by itself does not show that order effects were absent or that the analysis adjusted for them. The record lists six sequences, with different orders of rest, Wii Fit Free Run, Wii Fit 3 bouts, and treadmill activity. It does not report a sequence-effect assessment, a washout procedure, or other design details that would establish how order was handled.

There is also a difference between the sequence descriptions and the activity names in the outcome summaries. The summaries list Super Hula Hoop, Advanced Steps, and Rhythm Boxing, while the sequence descriptions do not name those conditions. The registry record does not explain that mapping. This documentation gap limits assessment of how the posted activity results relate to the stated crossover schedule.

What does the planning calculation represent?

The sample-size illustrations use the observed mean difference or a stated fraction of that observed effect, with two-sided significance level 0.05, equal allocation between two arms, and a normal approximation. These are planning assumptions for an illustrative calculation, not evidence about how this completed crossover trial was originally designed. The trial’s own design assumptions and sample-size justification are not reported in the registry record. In particular, the illustrations do not encode the crossover structure or a within-person correlation. They should not be interpreted as an analysis of the study’s actual power.

The record reports one primary outcome measure and no posted secondary outcome measures. It lists zero analyses. The registry record does not report the prespecified statistical methods, whether outcomes were transformed, how missing measurements were handled, or whether interim analyses were conducted. No specific approach to adjustment for multiple comparisons is reported. Without those details, the posted unadjusted comparisons should be read as descriptive statistical summaries rather than a complete account of the trial’s planned inferential framework.

10. Confidence Intervals and Precision

The posted confidence intervals quantify uncertainty in the recalculated mean differences under the assumptions used for those calculations. For Wii Fit Free Run, the reported mean difference is 4.1 METs, with a confidence interval from 3.598 to 4.602. For Super Hula Hoop, the mean difference is 3.0, with an interval from 2.533 to 3.467. For Advanced Steps, the difference is 2.9, with an interval from 2.183 to 3.617. Rhythm Boxing has a difference of 3.2 and an interval from 2.876 to 3.524. Treadmill Running/Walking has a difference of 7.1 and an interval from 6.312 to 7.888.

In general, a confidence interval gives a range of estimates compatible with the data and the calculation method at the stated confidence level. The registry does not state a confidence level in the posted results, so one should not assign a level to these intervals based only on the record. The interval endpoints are not guarantees about the true difference, and they do not describe the spread of individual measurements.

Precision also depends on whether the analysis reflects the trial design. These intervals come from simple, unadjusted recalculations using posted summary statistics. Since the study was a crossover, accounting for the relationship between repeated measurements could affect uncertainty. The registry does not provide the paired data or a reported crossover model needed to assess that issue. The intervals are therefore best understood as precision summaries for the recalculations, not as a full design-aware uncertainty analysis.

11. Planning a Similar Trial: Sample Size

This is a planning illustration, not a re-evaluation of the original trial. It asks: if a new study wanted to detect a difference like the one observed, or a smaller one, how large would it need to be? It is deliberately not “observed power” of the finished trial, which is not a meaningful quantity.

The sample-size figures are planning illustrations, not observed enrollment targets derived from the trial’s original design. The trial’s own sample-size justification and original design assumptions are not reported in the registry record. For these illustrations, the assumptions are a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation. The target effect is the stated fraction of the observed effect. The figures are participants per arm, not total events.

The 80% power column describes the planned number of participants per arm for a hypothetical study to have 80% power under those assumptions and for the chosen effect size. The 90% power column gives the corresponding per-arm planning figure for 90% power. Power is the probability of detecting an effect of the specified size under the assumed model and conditions, if that effect is present. The values are planning illustrations based on the observed effect, not observed power for the completed study.

The rows that use smaller fractions of the observed effect represent planning for smaller differences. Smaller effects are harder to distinguish from random variation, so they generally require more participants than larger effects under the same assumptions. The displayed figures should be used to understand how the assumed effect size and desired power influence a hypothetical sample-size calculation. They do not account for the crossover structure, and they should not be treated as a revised sample-size recommendation for this trial.

12. How the Sample Size Is Derived

Power is the probability that a study of a given size rejects the null hypothesis when a specific true effect exists. It depends on four things: the effect to detect, the variability of the outcome, the significance level (here a two-sided α of 0.05, so z_1−α/2 = 1.960) and the desired power (z_1−β = 0.842 for 80% and 1.282 for 90%).

Formula

n is the number of participants in each arm, Δ is the difference in means to detect and σ is the common standard deviation.

Worked calculation for this trial

1. Observed difference Δ = 4.100; pooled standard deviation σ = 0.992.
2. n = 2 × (1.96 + 0.842)² × 0.992² / 4.100² = 0.9, rounded up to 1 participants per arm for 80% power.

The smaller-effect rows in the table above repeat the same calculation with the effect multiplied by 0.75 and 0.5 (for ratios, applied to the logarithm of the ratio).

R code

alpha <- 0.05
z_a   <- qnorm(1 - alpha / 2)          # two-sided
delta <- 4.1                      # observed difference in means
sigma <- 0.99247166206396                     # pooled standard deviation
n_per_arm <- function(power, frac = 1) {
  ceiling(round(2 * (z_a + qnorm(power))^2 * sigma^2 / (delta * frac)^2, 6))
}
for (f in c(1, 0.75, 0.5))
  cat(sprintf("%3.0f%% of observed effect: n per arm = %s (80%% power), %s (90%% power)\n", 100 * f,
              format(n_per_arm(0.80, f), big.mark = ","), format(n_per_arm(0.90, f), big.mark = ",")))

# Check against R's built-in function (t-based, so very slightly larger)
cat("power.t.test:", round(power.t.test(delta = delta, sd = sigma, power = 0.80)$n, 1), "\n")

# Simulation: exact two-sample t-test using simulated means and variances
set.seed(1561716)
n    <- n_per_arm(0.80)
reps <- 20000
m_diff <- rnorm(reps, delta, sigma * sqrt(2 / n))             # difference in sample means
s2     <- sigma^2 * rchisq(reps, 2 * (n - 1)) / (2 * (n - 1))   # pooled sample variance
tstat  <- m_diff / sqrt(s2 * 2 / n)
cat(sprintf("Simulated power at n = %s per arm: %.3f (%d replicates)\n", format(n, big.mark = ","), mean(abs(tstat) > qt(0.975, 2 * (n - 1))), reps))

Output from running the code

100% of observed effect: n per arm = 1 (80% power), 2 (90% power)
 75% of observed effect: n per arm = 2 (80% power), 3 (90% power)
 50% of observed effect: n per arm = 4 (80% power), 5 (90% power)
power.t.test: 2.4 
Simulated power at n = 1 per arm: NA (20000 replicates)

The simulation draws many sets of group means and variances at the planned sample size and counts how often the two-sample t-test rejects the null. It should land close to the target power; at very small required sample sizes it can fall below it, because the normal approximation is rough there.

13. Multiplicity, Missing Data and Analysis Populations

The registry posts comparisons of each listed activity with rest, and each comparison reports p < 0.001. The record does not report a multiplicity adjustment or a prespecified plan for handling multiple comparisons. When several hypotheses are tested, the chance of at least one false-positive result can increase if each test is interpreted separately without adjustment. Whether an adjustment is appropriate depends on the prespecified questions and analysis plan, which are not reported in the registry record. The posted p-values are explicitly unadjusted.

The registry lists one primary outcome measure and no secondary outcomes, and it records zero analyses. It does not report whether all planned analyses or outcomes were posted, how the primary comparison was specified, or whether any additional analyses were conducted. Consequently, the set of posted results cannot establish how the reported tests fit into a broader prespecified analysis plan.

Missing-data methods and analysis populations are also not reported in the registry record. The record does not say whether all randomized participants contributed complete measurements, how incomplete activity sessions were handled, whether exclusions occurred after randomization, or whether the results use an intention-to-treat or other analysis population. Although 30 participants are listed for each condition, those summary counts do not provide information about the completeness of each participant’s repeated measurements.

For a crossover study, analysis choices can include how to account for within-person correlation, order, period, and possible carryover. The registry record does not report whether these factors were examined or incorporated into the sponsor’s analysis. It also does not describe interim analyses or a strategy for handling multiplicity across outcomes or conditions. These reporting gaps limit interpretation of the unadjusted recalculations, but they do not by themselves establish that the original analysis was inadequate.

14. 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.

The adverse-event information is listed by crossover sequence. Each of the six sequence groups reports 5 participants at risk for serious adverse events and 0 affected; each also reports 5 participants at risk for other adverse events and 0 affected. The registry therefore records no affected participants in the posted serious or other adverse-event fields for these groups.

These figures are limited to the registry’s reported groups and categories. They do not describe event types, severity grades, timing, or attribution to a particular activity. The death counts are not reported in the registry record. The absence of affected participants in the posted fields should not be read as proof that no event of any kind occurred or that all possible harms were assessed. The record does not provide further detail about safety monitoring or how adverse events were collected.

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

The results describe energy expenditure measurements for healthy young adults during rest and the activity conditions named in the registry. In the posted summaries, the mean was 0.9 METs at rest, 3.8 to 5.0 METs for the listed Wii Fit activities, and 8.0 METs for Treadmill Running/Walking. The reported unadjusted differences from rest were positive for each listed activity, and all posted comparisons had p < 0.001.

These findings address the measured endpoint under the study’s monitoring conditions. They do not establish how the activities affect fitness, health, weight, or any other outcome not reported in the registry. They also do not establish how people outside this study population would respond, or how energy expenditure might differ with other activity durations or settings. Those questions are not answered by the posted summaries.

The trial used a randomized crossover design, but the reported comparisons are recalculated from condition-level summary statistics and do not report an analysis of paired measurements. The record does not provide a direct adjusted comparison between Wii Fit activities and treadmill activity. Descriptive means can be compared for context, but the reported inferential tests are comparisons with rest, not tests of differences among the activity conditions.

The registry’s documentation also leaves uncertainty about how all activity summaries map to the listed crossover sequences, and it does not report missing-data procedures, analysis populations, or a multiplicity plan. The results are therefore best read as a description of the posted measurements and simple unadjusted contrasts, with the limits of the available statistical detail kept in view. They should not be translated into a general claim about the effectiveness or suitability of any activity.

16. Why This Trial Matters Statistically

This study is statistically interesting because its crossover design allows the same participants to be measured under multiple conditions. That structure can make within-person comparisons informative, but it also means that the analysis should account for the dependence among repeated measurements. The registry lists randomized sequences, yet the posted comparisons are simple unadjusted recalculations from group summaries. The difference between a repeated-measures design and an analysis that does not use the paired data is important when judging uncertainty and what the estimates represent.

The endpoint is measured on one continuous scale, METs, across rest and physical activity conditions. The results provide means, standard deviations, mean differences, confidence intervals, and unadjusted p-values. Reading these elements together illustrates how an estimate’s size, variability, and uncertainty are distinct pieces of information. A small p-value alone does not communicate the spread of individual measurements or answer whether a difference is meaningful for a broader research question.

The record also demonstrates why registry detail matters. The activity names in the outcome summaries do not fully match the conditions named in the sequence descriptions, and the analysis plan, missing-data handling, and multiplicity approach are not reported. These gaps do not erase the descriptive measurements, but they constrain evaluation of the statistical analysis and the relation between the randomized design and posted comparisons. The planning illustrations also show how assumed effect size and desired power shape hypothetical participant counts, while remaining separate from the original design justification.

17. 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 registry describes the participants only as healthy young adults and reports enrollment of 30. Broader eligibility criteria, demographic characteristics, and details needed to assess how representative the participants were are not reported in the registry record. The findings therefore describe the recorded study population rather than people in general.

The outcome summaries and sequence descriptions do not align fully: the outcome summaries include Super Hula Hoop, Advanced Steps, and Rhythm Boxing, while the sequence descriptions name rest, Wii Fit Free Run, Wii Fit 3 bouts, and treadmill activity. The registry record does not explain how these condition lists relate. This makes the activity schedule and the relation between the sequence allocation and each posted mean harder to assess.

The posted comparisons are unadjusted recalculations based on summary statistics, not a reported analysis using the crossover pairing. Participant-level measurements and the within-person correlations are not reported. The record also does not describe adjustment for sequence or period, assessment of carryover, missing-data procedures, the analysis population, or a multiplicity strategy. These limitations affect interpretation of the inferential results and their precision.

The endpoint reflects energy expenditure during 30 min of continuous monitoring at rest and during each activity. The registry does not report outcomes beyond this measurement, and it does not provide details about the measurement protocol beyond indirect calorimetry and conversion to METs. The original sample-size justification is not reported. Finally, the death counts are not reported in the registry record, and the adverse-event fields do not provide event descriptions or attribution by activity.

18. Related Tutorials

19. Related Statistical Calculators

20. Sources

• ClinicalTrials.gov: An Evaluation of the Energy Expenditure From Wii Fit Games — NCT01561716.
• Registry record last updated 2015-10-01; status last verified 2015-09.
• Results first posted 2012-04-25.
• 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.

21. Record Summary

NCT01561716 is a completed randomized crossover study of energy expenditure from Wii Fit activities, rest, and treadmill walking/running in healthy young adults. The registry records enrollment of 30 and reports continuous monitoring for 30 min at rest and during each activity. Energy expenditure was measured using indirect calorimetry and expressed in METs.

The posted means range from 0.9 METs at rest to 8.0 METs for Treadmill Running/Walking; listed Wii Fit activity means range from 3.8 to 5.0 METs. Unadjusted recalculated mean differences compare each activity with rest, and each posted comparison reports p < 0.001. The registry does not report a paired crossover analysis, the original sample-size justification, missing-data methods, or a multiplicity plan. The record lists no participants affected in the posted adverse-event fields by sequence; death counts are not reported.