Whey Protein Supplementation in High School Athletes: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Whey Protein Supplementation in High School Athletes (NCT05589129), a randomized na study. The primary outcome is Estimated VO2max.

2. Clinical Question

The broader study aim was to compare the groups on performance, recovery, and body composition changes in response to the intervention. Listed secondary outcomes include changes in muscular fatigue measured via repetitions to fatigue, speed, and muscular strength. The record also lists body weight changes, athletic performance, recovery, and sleep among the study conditions.

This is a question about a group comparison over time, not a comparison of a supplement with no intervention: both groups received a powder supplement, with whey protein in one group and a carbohydrate control in the other. The record identifies the trial as randomized, double masked, and parallel. It does not report the specific randomization procedure or who was masked. The intended contrast is therefore between the two assigned supplements, but the size and precision of any difference cannot be determined from the posted primary outcome information.

3. Trial Design

The registry record describes a randomized, double-masked, parallel-group trial. Participants were assigned to a whey protein supplement or a carbohydrate control. The overall aim was to compare performance, recovery, and body composition changes in adolescent soccer players during the competitive season in response to a 10-12-week intervention. The record lists enrollment of 31.

The whey supplement was a powder described as containing 20g of protein and 25.3g of product; the named product was Optimum Nutrition Double Chocolate Whey Protein Isolate. The carbohydrate control was described as a powder containing 20g of carbohydrate and 21.6g of product; the named product was Nesquik Chocolate Powder mix. The registry does not report the exact randomization method, the masking procedures, or which groups of people were masked.

The primary outcome was estimated VO2max, measured at baseline and post-intervention. The record says it was measured via a 1.5-mile run, with participants instructed to run as quickly as they can. The stated timeframe for the post-intervention measurement is 10-12-weeks. Secondary outcomes included changes in muscular fatigue via repetitions to fatigue, speed, and muscular strength. The record lists 13 outcome measures and 13 analyses, but does not describe each analysis or identify which procedures were applied to each measure.

The study is marked completed. Its start date is 2022-07-14, and its primary completion date is 2022-10-28. The sponsor is the University of Utah. The registry record does not report the protocol’s sample-size justification, a detailed schedule of assessments, adherence, or specific analysis populations. It also does not state whether there were interim analyses. These details should not be inferred from the trial’s randomized and double-masked labels.

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: Participants completed baseline testing after receiving written informed consent and assent. Participants were randomized to consuming whey protein or placebo. One participant withdrew before starting intervention.

Overall Study

Analysis population for the primary outcome, as defined in the registry: There were 10 in the Whey Protein Supplement as a result of participants dropping out, and there were 12 in Carbohydrate Control group as a result of participants dropping out.

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: Adolescent athletes

6. Primary Endpoint

The registry lists the primary outcome as Estimated VO2max, measured over Measured at baseline and post-intervention (10-12-weeks).

The primary endpoint is estimated VO2max, reported as a mean continuous measure in ml/kg/min. The record says it was estimated using a 1.5-mile run, with participants running as quickly as they can. Measurements were planned at baseline and post-intervention, with the latter described as occurring after 10-12-weeks.

As a general explanation, VO2max is used as an indicator of aerobic exercise capacity. A field test based on running performance can be used to estimate it without directly measuring oxygen uptake during a laboratory exercise test. The registry record describes the test procedure but does not provide the equation or other details used to convert run performance into an estimated VO2max value. Those measurement details are not reported in the registry record.

The endpoint is expressed as a mean, and its listed dispersion is the standard error. As a general statistical explanation, the mean describes the average measured value in a group, while the standard error describes the uncertainty around that estimated average. It is not a description of how much individual participants vary. The registry record does not include the endpoint values, standard errors, or an estimated difference between the groups, so the magnitude and precision of the observed comparison cannot be assessed.

Because measurements are described at baseline and post-intervention, interpretation would ordinarily consider both the values over time and the contrast between assigned groups. The registry record does not identify the precise primary contrast or report a single comparison. Its note indicates that the primary outcome has several categories or time points and was not reduced to one comparison.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The registry record identifies the design as randomized, double masked, and parallel. These labels describe broad features of the study design, but they do not give the detailed methods needed to reproduce the trial or its statistical analysis. The specific randomization procedure, allocation concealment, masking procedures, and analysis model are not reported in the registry record.

What does a randomized comparison estimate?

As a general explanation, random assignment is intended to make the groups comparable at the point of assignment, on average, by distributing measured and unmeasured characteristics without a systematic selection rule. A parallel-group design follows assigned participants in their respective groups rather than having each participant receive both interventions. The registry record names these design features, but does not report enough procedural detail to assess how assignment was implemented or whether the analysis followed the assignment groups.

The intervention contrast is whey protein powder versus carbohydrate control powder. Both groups are described as receiving a powder supplement. The primary endpoint is estimated VO2max, expressed as a mean in ml/kg/min and measured using a 1.5-mile run at baseline and post-intervention. The endpoint description is not itself a statistical method: it does not specify how the repeated measurements were incorporated into the analysis.

What do the mean and standard error describe?

As a general explanation, a mean is the arithmetic average of measured values in a group. A standard error describes the sampling uncertainty around an estimated statistic, such as a mean. It is distinct from a standard deviation, which describes the spread of individual observations. The registry record lists standard error as the dispersion measure for the primary endpoint, but reports no mean or standard error values. A confidence interval, if reported, would give a range of values compatible with the data and the chosen method, subject to the assumptions of that method. No confidence interval for the primary comparison is reported in the registry record.

Because the endpoint is measured at baseline and after the intervention, a statistical analysis could account for the repeated measurements in different ways. As a general explanation, an analysis may compare follow-up values between groups, compare changes from baseline, or model measurements across time. These methods can differ in their assumptions and in the exact contrast they estimate. The registry record does not say which method was used, nor does it report a primary contrast that would clarify the interpretation. The primary outcome is noted as having several categories or time points and not being reduced to one comparison.

How should significance and precision be read?

As a general explanation, a p-value measures how incompatible the observed data are with a specified null hypothesis under the statistical model. It does not describe the probability that a hypothesis is true, and it does not give the size or practical importance of a difference. A confidence interval conveys uncertainty about an estimate across a range of plausible values under its assumptions. In this case, the registry record does not report a p-value, an interval, or an estimate for the primary comparison, so neither statistical significance nor precision can be evaluated.

The record lists 13 outcome measures and 13 analyses. When several outcomes, time points, or comparisons are assessed, the chance of at least one apparently unusual result can increase if all are treated as independent opportunities for a finding. As a general explanation, multiplicity procedures can adjust the interpretation or testing threshold, or a protocol can designate a primary comparison in advance. The registry record does not report an adjustment strategy, a hierarchy of outcomes, or enough detail to determine how multiple comparisons were handled.

What do the planning assumptions mean?

The record describes planning illustrations based on the observed effect, with two-sided significance level 0.05, equal allocation between arms, and a normal approximation. The effect to detect is expressed as a stated fraction of the observed effect. As a general explanation, a sample-size calculation describes how many participants would be needed under specified assumptions for a planned study. It does not measure the probability that the completed trial found a true effect. These illustrations are not the trial’s reported design justification, and the protocol’s sample-size justification is not reported in the registry record. The displayed planning assumptions should not be interpreted as observed power.

The assumptions also depend on what effect is used as the target and on the statistical model. Planning around an observed effect is an illustration, not confirmation that the observed effect is stable or that a future study would reproduce it. No numerical planning outputs or observed primary effect are reported in the registry record, so no sample-size value or effect estimate can be stated.

Finally, the record gives outcome-specific counts of 10 in the whey protein group and 12 in the carbohydrate control group, attributed to dropout. As a general statistical principle, missing observations can affect both the precision and the validity of a comparison, depending on why data are missing and how they are handled. The registry record does not describe missing-data assumptions, imputation, or sensitivity analyses. Those methods must not be presumed.

10. Multiplicity, Missing Data and Analysis Populations

The registry record lists 13 outcome measures and 13 analyses. It does not explain how the outcomes were prioritized, whether a multiplicity adjustment was used, or whether there was a prespecified hierarchy of comparisons. The primary outcome is identified as estimated VO2max, but a note indicates that it has several categories or time points and was not reduced to a single comparison. The record therefore does not provide one clearly stated primary contrast with an estimate and uncertainty measure.

As a general explanation, testing several outcomes or time points can make it more likely that at least one result appears noteworthy by chance. A prespecified primary comparison and a stated approach to multiplicity help readers interpret a collection of tests. The absence of this information in the registry record means the treatment of multiple comparisons cannot be evaluated; it does not establish that an adjustment was or was not performed outside the record.

For the primary outcome, the record reports 10 participants in the whey protein group and 12 in the carbohydrate control group, attributing the counts to participants dropping out. It does not report how many participants were initially assigned to each group, when or why participants dropped out, whether outcome measurements were missing for other reasons, or how missing observations were handled. The analysis population is not reported in the registry record. It is therefore not possible to determine whether the reported counts represent all randomized participants with available measurements or a different analysis set.

As a general explanation, excluding participants with missing outcomes can change the composition of the groups being compared, while methods for handling missing values rely on assumptions about the missingness process. The registry record does not report an imputation method, a missing-data model, or sensitivity analyses. It also does not report interim analyses or the protocol’s sample-size justification. No particular procedure should be inferred from the study’s randomized or double-masked design.

11. 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.

Most frequent non-serious adverse event terms

The registry record reports no serious adverse events among the 10 participants at risk in the whey protein group and none among the 12 participants at risk in the carbohydrate control group. It reports no deaths in either group. For other adverse events, it reports none among the 10 participants at risk in the whey protein group and one among the 12 participants at risk in the carbohydrate control group.

These are the event counts and at-risk group sizes reported in the record; they do not by themselves establish whether the groups differ in safety. As a general explanation, a small number of observed events gives limited information about how often events might occur outside the observed participants. The record does not provide event descriptions for the non-serious event, timing, duration, severity details beyond the serious-event classification, or an assessment of whether it was related to the intervention. The list of top serious-event terms is empty.

The adverse-event information should be read separately from the primary performance endpoint. It is a registry summary of reported event counts, not a comprehensive characterization of every possible risk or an estimate of comparative safety. The record does not state the method for collecting events, the observation period used for these counts, or whether all participants were monitored for the same duration. No inference about unreported events is warranted.

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

The record establishes that a randomized, double-masked, parallel-group comparison was registered for adolescent soccer players. It describes a whey protein powder and a carbohydrate control powder, identifies estimated VO2max as the primary outcome, and states that the measurement was made at baseline and post-intervention using a 1.5-mile run. It also reports outcome-specific group counts after dropout and a small number of adverse-event counts.

What the record does not establish is the direction or magnitude of the primary outcome comparison. Group means, standard errors, confidence intervals, p-values, and a single comparison are not reported in the registry record. Without an estimate and its uncertainty, it is not possible to say how closely the observed data align with no difference or with a range of possible differences. The absence of reported results should not be interpreted as evidence for equivalence, benefit, or harm.

As a general explanation, a difference in sample means is not automatically a reliable or important difference. Its interpretation depends on the estimate, its uncertainty, the measurement process, the analysis plan, and the study context. The registry record describes the run-based measure but does not report the conversion details for estimated VO2max or the model used to analyze baseline and post-intervention values. It also does not report a clinical or performance threshold for interpreting the size of a difference.

The listed secondary outcomes broaden the study’s stated scope to fatigue, speed, and strength, while the overall aim also mentions recovery and body composition. However, the registry information does not provide numerical findings for those outcomes. Their presence in the record is not evidence that changes were observed. Similarly, the adverse-event counts document what was reported in the registry, but the details available do not support a broad safety conclusion.

The planning assumptions are not trial findings. They describe illustrations based on an observed effect, a two-sided significance level of 0.05, equal allocation, and a normal approximation. They do not replace a reported effect estimate, and they are not observed power. The protocol’s own sample-size justification is not reported in the registry record.

Accordingly, the most defensible reading is descriptive: the study question and design are recorded, but the posted information does not allow a quantitative assessment of the primary comparison or its precision. Any conclusion about the intervention’s effects would require outcome results and analysis details that are not reported in the registry record.

13. Why This Trial Matters Statistically

This trial is statistically informative as an example of the difference between a registered study question and a reportable estimate. The registry record identifies a randomized, double-masked, parallel comparison and a continuous primary outcome measured at baseline and post-intervention. Those elements describe the question and broad design, but they are not enough to evaluate the result without group estimates and uncertainty.

The participant counts for the primary outcome are reported as 10 in the whey protein group and 12 in the carbohydrate control group after participants dropped out. These counts make attrition relevant to interpretation, yet the record does not explain when or why participants left, how missing measurements were treated, or which analysis population was used. Those details matter because the analyzed participants and the method for handling missing outcomes can affect a group comparison.

The record also lists 13 outcome measures and 13 analyses while noting that the primary outcome has several categories or time points and is not reduced to a single comparison. This makes clarity about outcome prioritization and multiplicity especially important. Without a clearly specified contrast and a reported approach to multiple comparisons, readers cannot assess how the reported tests relate to the study’s primary question.

As a general statistical principle, an estimate and its interval are usually more informative than a statement of statistical significance alone: they describe both the size of a comparison and its uncertainty. Neither is reported for the primary outcome in the registry record. The planning assumptions, including a two-sided significance level of 0.05 and equal allocation, are not a substitute for those results or for the protocol’s design justification.

The study’s focus on adolescent soccer players and a competitive-season intervention makes the population and setting explicit. Statistical interpretation still depends on the completeness and transparency of the reported outcome data. The record therefore illustrates why design labels, endpoint definitions, participant counts, and numerical results all serve distinct roles in evaluating a clinical trial.

14. 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 trial-specific limitation for interpreting the primary endpoint is that the registry record does not report numerical outcome results. There are no group means, standard errors, confidence intervals, p-values, or a single estimated comparison for estimated VO2max. The record notes that the primary outcome includes several categories or time points and was not reduced to one comparison, which leaves the precise target contrast unclear.

Outcome-specific participant counts are reported as 10 for the whey protein group and 12 for the carbohydrate control group, with both counts attributed to dropout. The registry record does not give a complete participant flow, the initial number assigned to each arm, reasons or timing of dropout, or details of missing outcome data. It also does not report the analysis population or how missing measurements were handled. The impact of attrition on the comparison therefore cannot be assessed from this record.

The record describes estimated VO2max as measured via a 1.5-mile run but does not report how run performance was converted to the estimate, or specify the statistical model used for baseline and post-intervention measurements. The multiplicity approach for 13 outcome measures and 13 analyses is not reported. The protocol’s sample-size justification, a detailed analysis plan, and any interim analyses are also not reported in the registry record.

The adverse-event counts are limited in detail: the record does not describe the one other adverse event reported in the carbohydrate control group, its timing, or its relation to the intervention. It provides no serious adverse-event terms. These reporting gaps constrain interpretation and should not be filled by assumptions about the protocol or results.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: Whey Protein Supplementation in High School Athletes — NCT05589129.
• Registry record last updated 2026-04-27; status last verified 2026-01.
• Results first posted 2026-04-27.
• 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.

18. Record Summary

The registry record describes NCT05589129, titled “Whey Protein Supplementation in High School Athletes,” with an official title focused on performance, recovery, and body composition in adolescent soccer players during the competitive season. The study is marked completed, with enrollment of 31. The sponsor is the University of Utah. The listed start date is 2022-07-14, and the primary completion date is 2022-10-28.

The design is randomized, double masked, and parallel. The intervention is a whey protein supplement, compared with a carbohydrate control. The primary outcome is estimated VO2max, measured using a 1.5-mile run at baseline and post-intervention. The record reports 10 participants in the whey group and 12 in the control group for that outcome after dropout, but does not report numerical primary results or a single comparison.

The record lists 13 outcome measures and 13 analyses, as well as secondary outcomes involving muscular fatigue, speed, and muscular strength. Serious adverse events and deaths are reported as zero in both groups; one other adverse event is reported in the carbohydrate control group. The registry record does not report detailed analysis methods, missing-data handling, or a protocol sample-size justification.