Higher Walk Or Run Distance Predicts Very Slightly Lower Hydration for Population

Higher Walk Or Run Distance Predicts Very Slightly Lower Hydration for Population

Contents

Variables

A
Walk or Run Distance 891
A
Hydration 1

Categories

A
Physical Activity 1719
A
Vital Signs 110

Actions

A
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A
Your Data

Tags

Medium Confidence
Very Weak Effect Size
Negative Relationship
Population Study
cause image gauge image effect image
Participants reported a 0.2% average decrease in Hydration following above average Walk Or Run Distance.

Abstract

Hydration was generally 1% higher than average after a total of 2510 meters of Walk Or Run Distance over the previous 7 days.

Aggregated data from 1 study participants suggests with a MEDIUM degree of confidence (p=0.119, 95% CI -0.221 to 0.167) that Walk Or Run Distance has a very weakly negative predictive relationship (R=-0.0269) with Hydration.

The highest quartile of Hydration measurements were observed following an average 2580 meters Walk Or Run Distance per day.

The lowest quartile of Hydration measurements were observed following an average 2640 meters of Walk Or Run Distance per day.

After an onset delay of 0 seconds, Hydration is typically 1% lower than average over the 7 days following around 2640 meters of Walk Or Run Distance Walk Or Run Distance.

Keywords: Walk Or Run Distance, Hydration, N-of-1 trials, real-world evidence, causal inference, observational study

Preliminary: Based on 1 participants. Results may change as more data is collected.

Results

Primary Findings

Analysis of 445 paired observations from 1 participants revealed a minimal reduction in Hydration following above-average Walk Or Run Distance exposure.

-0.4%
Change from Baseline
Minimal effect on Hydration
0.00
Predictor Impact Score
Insufficient evidence for causal relationship

Supporting Statistics

Medium
Confidence
-0.027
Correlation (r)
p = 1.000
Significance
z = 0.10
Effect Magnitude
φ = 1.00
Temporality

What This Means

When participants had above-average Walk Or Run Distance:

  • Hydration decreased by 0.4% on average
  • Temporal analysis supports Walk Or Run Distance as the predictor (not the outcome)

Interpreting the Predictor Impact Score

The Predictor Impact Score (PIS) integrates multiple Bradford Hill causal criteria into a single metric. Use this guide to interpret the score:

PIS Range Interpretation Recommended Action
≥ 0.5 Strong evidence High priority for RCT validation
0.3 - 0.5 Moderate evidence Consider for experimental investigation
0.1 - 0.3 Weak evidence Monitor for additional data
< 0.1 Insufficient evidence Low priority; may be noise

Note: PIS is a prioritization heuristic, not proof of causation. High scores indicate relationships worth investigating, not confirmed causal effects. With only 1 participants, these scores are preliminary and will become more reliable as additional data is collected.

Optimal Daily Values

No clear dose-response relationship detected. The Walk Or Run Distance values associated with high and low Hydration are too similar to provide meaningful dosing guidance. This may indicate a threshold effect (any amount works equally well), no effect, or insufficient data variance. With more participants, a clearer pattern may emerge.

Population Correlation

Walk Or Run Distance Distribution

Hydration Distribution

Statistical Summary

Relationship Statistics

Property Value
Cause Variable Name Walk Or Run Distance
Effect Variable Name Hydration
Sinn Predictive Coefficient 0.0012799367688229
Confidence Level MEDIUM
Confidence Interval 0.19380691998456
Forward Pearson Predictive Coefficient -0.0269
Critical T Value 1.646
Total Walk Or Run Distance Over Previous 7 days Before ABOVE Average Hydration 2580 meters
Total Walk Or Run Distance Over Previous 7 days Before BELOW Average Hydration 2640 meters
Duration of Action 7 days
Effect Size very weakly negative
Number of Paired Measurements 445
Optimal Pearson Product 0.00061589297972047
P Value 0.11943867197073
Statistical Significance 0.9998
Strength of Relationship 0.19380691998456
Study Type population
Analysis Performed At 2026-01-04
Number of Participants 1

Walk or Run Distance Info

Property Value
Variable Name Walk Or Run Distance
Aggregation Method SUM
Analysis Performed At 2020-09-11
Duration of Action 7 days
Kurtosis 18.843598392696
Maximum Allowed Value 175000 meters
Mean 3558.0042632859 meters
Median 3158.90008036 meters
Minimum Allowed Value 1 meters
Number of Aggregate Predictors 642
Number of Aggregate Outcomes 249
Number of Measurements 123085
Number of Measurements (including those generated by tagged, joined, or child variables) 87104
Public true
Onset Delay 0 seconds
Standard Deviation 2361.166855319
Unit Meters
User Variables 378
UPC 744960759935
Variable Category Physical Activity
Variable ID 1304
Variance 9674812.3231088

Hydration Info

Property Value
Variable Name Hydration (Weight)
Aggregation Method SUM
Analysis Performed At 2021-06-10
Duration of Action 24 hours
Kurtosis 2.2723784503376
Mean 33.299 kilograms
Median 33.18 kilograms
Minimum Allowed Value 0 kilograms
Number of Aggregate Predictors 1
Number of Aggregate Outcomes 0
Number of Measurements 276
Number of Measurements (including those generated by tagged, joined, or child variables) 276
Public true
Onset Delay 0 seconds
Standard Deviation 1.2873069181185
Unit Kilograms
User Variables 1
Variable Category Vital Signs
Variable ID 6066511
Variance 1.6571591014358

Introduction

Background

Walk Or Run Distance (Physical Activity) and Hydration (Vital Signs) are both important factors in understanding human health and well-being. This study investigates the relationship between these two variables using real-world observational data.

Traditional randomized controlled trials (RCTs), while the gold standard for causal inference, are often impractical, expensive, or unethical for studying many health relationships. Aggregated N-of-1 observational studies offer a complementary approach that leverages within-subject comparisons across large populations to identify meaningful patterns.

Research Question

Does Walk Or Run Distance affect Hydration?

Additionally, we seek to determine:

  1. What is the direction and magnitude of any effect?
  2. How confident can we be in this relationship based on the available data?
  3. What are the optimal levels of Walk Or Run Distance for maximizing Hydration?

Study Objective

The objective of this study is to determine the nature of the relationship (if any) between Walk Or Run Distance and Hydration. Additionally, we attempt to determine the Walk Or Run Distance values most likely to produce optimal Hydration values.

Study Overview

This is a population-level observational study using aggregated N-of-1 methodology. By aggregating individual N-of-1 experiments, we can identify population-level patterns while accounting for the substantial individual variation that exists in most health relationships. Effect sizes are reported as percent change from baseline, enabling intuitive interpretation and comparison across different measures.

Full Methodology: Framework for Real-World Evidence-Based Pharmacovigilance: Aggregated N-of-1 Trials for Quantifying Treatment Effects

Discussion

Interpretation of Findings

Participants experienced a 0.4% reduction in Hydration following above-average Walk Or Run Distance exposure. The Predictor Impact Score (PIS) of 0.00 indicates insufficient evidence for a causal relationship.

Statistical Significance

Using a two-tailed t-test with alpha = 0.05, it was determined that the change in Hydration is not statistically significant at a 95% confidence interval. This suggests that the Walk Or Run Distance value may not have a significant influence on the Hydration value, or that more data is needed to detect an effect.

After treatment, a 0.2% decrease (-0.141 kilograms) from the mean baseline 33.2 kilograms was observed. The relative standard deviation at baseline was 4%. The observed change was 0.1 times the standard deviation.

A common rule of thumb considers a change greater than twice the baseline standard deviation on two separate pre-post experiments may be considered significant. This occurrence would have only a 5% likelihood of resulting from random fluctuation (a p-value < 0.05).

T-Test Details
Observed t-value: 1.553
Critical t-value: 1.646

Since t = 1.55 < 1.65, we cannot reject the null hypothesis.

Biological Plausibility

A plausible bio-chemical mechanism between predictor and outcome is critical for interpreting observational findings. This is where human judgment excels beyond statistical analysis.

Community feedback on the biological plausibility of this relationship is still being collected. Consider the known mechanisms by which Walk Or Run Distance might influence Hydration.

Bradford Hill Criteria Assessment

The Bradford Hill criteria provide a framework for assessing causality in observational studies. Our methodology operationalizes six of the nine criteria through the Predictor Impact Score (PIS):

Criterion How Addressed Metric
Strength Effect size magnitude Percent change from baseline (Δ%), z-score
Consistency Cross-participant replication Number of users (N), number of pairs (n)
Temporality Predictor precedes outcome Temporality factor (φ), onset delay (δ > 0)
Biological Gradient Dose-response relationship Gradient coefficient (φgradient)
Plausibility Biological mechanism assessment Community votes on mechanism plausibility
Specificity Category appropriateness Interest factor (finterest)

Predictor Impact Score (PIS)

The PIS integrates multiple Bradford Hill criteria into a composite metric quantifying how reliably a predictor affects an outcome. Higher scores indicate stronger evidence:

Population-Level PIS:

$$\text{PIS}_{\text{agg}} = |r_{\text{forward}}| \cdot w \cdot \phi_{\text{users}} \cdot \phi_{\text{pairs}} \cdot \phi_{\text{change}} \cdot \phi_{\text{gradient}}$$

Where φ-factors are saturation functions approaching 1 as evidence accumulates:

  • φusers = 1 - e-N/10 (user saturation)
  • φpairs = 1 - e-n/nsig (pair saturation)
  • φchange = 1 - e-Δspread/Δsig (effect spread saturation)
  • w = weighted average of plausibility votes

Temporality Assessment

We assess evidence for correct causal direction using the temporality factor:

$$\phi_{\text{temporal}} = \frac{|r_{\text{forward}}|}{|r_{\text{forward}}| + |r_{\text{reverse}}|}$$

Values approaching 1 indicate the predictor precedes the outcome (supporting causation); values near 0.5 suggest ambiguous directionality; values near 0 suggest reverse causation or confounding by indication.

Limitations

As with any observational study, correlation does not prove causation. Key limitations include:

  • Unmeasured confounders: Variables not tracked may influence results
  • Self-selection bias: Health trackers may differ from the general population
  • Measurement error: Self-reported data may contain recall bias
  • Confounding by indication: Sicker individuals may use more treatments

However, within-subject comparison and temporal precedence analysis partially mitigate these limitations. If the relationship is merely coincidental, as participants independently modify their Walk Or Run Distance values, the observed strength will decline over time. Spurious correlations naturally dissipate as more data is collected.

Future Directions

Future research should examine:

  • Subgroup analyses to identify individual differences in response
  • Potential confounders and mediators of the observed relationship
  • Optimal dosing and timing for Walk Or Run Distance
  • Confirmation through prospective or randomized designs
  • Biological mechanisms underlying the observed effects

Conclusion

📊 Preliminary Findings: With 1 participants, these results are based on limited data. Effect sizes and confidence will improve as more participants contribute data. Consider these findings directional rather than definitive.

Above-average Walk Or Run Distance was associated with a 0.4% reduction in Hydration—a minimal effect. The Predictor Impact Score of 0.00 indicates this relationship is requiring additional data before conclusions.

Bottom Line: Based on a PIS of 0.00 and a 0.4% effect size, this relationship currently lacks sufficient evidence. Continue monitoring as more data becomes available. Note: These conclusions may strengthen or change direction as more data is collected.

These findings contribute to our understanding of how Walk Or Run Distance may influence Hydration in real-world conditions. While preliminary, these results may inform future research directions. As more participants contribute data, the reliability and precision of these findings will improve substantially.

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Methods

Study Design

This study is based on data donated by 1 participants. Thus, the study design is equivalent to the aggregation of 1 separate n=1 observational natural experiments.

This within-subject design is powerful because it controls for all stable individual characteristics (genetics, baseline health status, socioeconomic factors) that might otherwise confound the relationship between variables.

Data Analysis

Temporal Assumptions

The analysis incorporates temporal assumptions about the relationship between variables:

  • Onset Delay: It was assumed that 0 seconds would pass before a change in Walk Or Run Distance would produce an observable change in Hydration.
  • Duration of Action: It was assumed that Walk Or Run Distance could produce an observable change in Hydration for as much as 7 days after the stimulus event.

Statistical Methods

For each participant, we calculated the Pearson correlation coefficient between Walk Or Run Distance values and subsequent Hydration values. Individual correlations were then aggregated using Fisher's z-transformation to produce a population-level estimate:

Individual Correlation:

$$r_i = \frac{\sum(x_{ij} - \bar{x}_i)(y_{ij} - \bar{y}_i)}{\sqrt{\sum(x_{ij} - \bar{x}_i)^2 \sum(y_{ij} - \bar{y}_i)^2}}$$

Fisher's Z-Transformation:

$$z_i = \frac{1}{2} \ln\left(\frac{1 + r_i}{1 - r_i}\right)$$

Aggregated Correlation:

$$\bar{r} = \tanh(\bar{z}) \quad \text{where} \quad \bar{z} = \frac{1}{N}\sum_{i=1}^{N} z_i$$

Effect Size Calculation

Effect sizes are reported as percent change from baseline. For each participant, we compare the outcome following above-average predictor values to the overall baseline outcome:

$$\Delta\%_{\text{baseline}} = \frac{\bar{O}_{\text{follow-up}} - \bar{O}_{\text{baseline}}}{\bar{O}_{\text{baseline}}} \times 100$$

Effect Magnitude (Z-Score)

To assess effect magnitude relative to natural variability, we calculate the z-score:

$$z = \frac{|\Delta\%_{\text{baseline}}|}{\text{RSD}_{\text{baseline}}}$$

where RSDbaseline is the relative standard deviation of outcome during baseline period

A z-score > 2 indicates statistical significance (p < 0.05), meaning the observed change exceeds typical baseline fluctuation and is unlikely due to random variation.

Statistical Significance

Correlation significance is assessed using a two-tailed t-test:

$$t = \frac{r\sqrt{n-2}}{\sqrt{1-r^2}}$$

We reject the null hypothesis (ρ = 0) at α = 0.05 when |t| exceeds the critical value, providing statistical evidence that the observed relationship is not due to chance.

Data Sources

Walk Or Run Distance data was primarily collected using Fitbit. Fitbit makes activity tracking easy and automatic.

Hydration data was primarily collected using Withings. Withings creates smart products and apps to take care of yourself and your loved ones in a new and easy way. Discover the Withings Pulse, Wi-Fi Body Scale, and Blood Pressure Monitor.

Data Quality

Data quality measures were applied to ensure reliable results:

  • Minimum Data Requirement: Only participants with sufficient paired observations were included in the analysis.
  • Outlier Handling: Extreme values were winsorized to reduce the influence of measurement errors.
  • Missing Data: Days with missing values were handled using appropriate filling strategies based on the variable type.
  • Test User Exclusion: Test accounts and invalid users were excluded from all analyses.

Principal Investigator

Program & Methods

Mike P. Sinn
Sinn, M. P.

Designed and implemented data collection, aggregation, causal inference pipeline, and automated study generation framework. Developed the Predictor Impact Score methodology operationalizing Bradford Hill criteria for ranking causal relationships in observational data. When he tells people this at parties, they usually say they have to go check on their car.

Individual study outputs are automated, reproducible, and open to external audit. (Which I would seriously recommend.)

Contact

Cite This Study

APA Format
Sinn, M. P. (2026). Causal Analysis: Does Walk Or Run Distance Affect Hydration (Weight)?. The Journal of Citizen Science. https://studies.crowdsourcingcures.org/study/cause-1304-effect-6066511-population-study
BibTeX 
@misc{sinn_cause_1304_effect_6066511_population_study_2026,
  author = {Sinn, Mike P.},
  title = {Causal Analysis: Does Walk Or Run Distance Affect Hydration (Weight)?},
  year = {2026},
  publisher = {The Journal of Citizen Science},
  url = {https://studies.crowdsourcingcures.org/study/cause-1304-effect-6066511-population-study},
  note = {Accessed: January 6, 2026}
}
Chicago/Turabian
Sinn, Mike P. "Causal Analysis: Does Walk Or Run Distance Affect Hydration (Weight)?." The Journal of Citizen Science. Accessed January 6, 2026. https://studies.crowdsourcingcures.org/study/cause-1304-effect-6066511-population-study.
Harvard
Sinn, M.P., 2026. Causal Analysis: Does Walk Or Run Distance Affect Hydration (Weight)?. [Aggregated N-of-1 Study] The Journal of Citizen Science. Available at: https://studies.crowdsourcingcures.org/study/cause-1304-effect-6066511-population-study [Accessed January 6, 2026].

Study Type: Aggregated N-of-1 Observational Mega-Study
Evidence Level: Level II (Real-World Evidence)
Methodology: Bradford Hill Criteria with Predictor Impact Score (PIS)

References

This framework was originally developed in 2013 based on the Bradford Hill criteria. Subsequent literature has independently validated similar approaches to causal inference from observational data:

  1. Hill, A.B. (1965). The environment and disease: association or causation? Proceedings of the Royal Society of Medicine, 58(5), 295-300. [Bradford Hill criteria]
  2. Lillie, E.O., et al. (2011). The n-of-1 clinical trial: the ultimate strategy for individualizing medicine? Personalized Medicine, 8(2), 161-173. [N-of-1 methodology]
  3. Pearl, J. (2009). Causality: Models, Reasoning, and Inference . Cambridge University Press. [Causal inference]
  4. Hernán, M.A., & Robins, J.M. (2020). Causal Inference: What If . Chapman & Hall/CRC. [Free textbook]
  5. FDA (2018). Framework for FDA's Real-World Evidence Program . U.S. Food and Drug Administration. [Regulatory context]
  6. Duan, N., et al. (2013). Single-patient (n-of-1) trials: a pragmatic clinical decision methodology . Journal of Clinical Epidemiology, 66(8), S21-S28.
  7. Platt, R., et al. (2018). The FDA Sentinel Initiative—an evolving national resource . New England Journal of Medicine, 379(22), 2091-2093.

This information is for research and educational purposes only, not medical advice. Consult a healthcare provider before making health decisions. Terms of Service

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