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Normalized data may have limitations in determining the reliability of MVC measurements
Christoph Anders1, Christin Alex2, Max Herzberg2
1Division of Motor Research, Pathophysiology and Biomechanics; Experimental Trauma Surgery, Department for Hand, Reconstructive, and Trauma Surgery, Jena University Hospital, Friedrich-Schiller-University Jena, Jena, Germany. Christoph.anders@med.uni-jena.de.
Scientific Reports
|September 25, 2025
Summary
Normalization of measurement data can impact reliability parameters. This study found that using normalized force values for trunk extension and flexion decreased reliability, suggesting original data is better for these calculations.
Area of Science:
- Biomechanics
- Human Movement Science
- Measurement Science
Background:
- Reliability of measurement data is crucial for scientific findings.
- Normalization is often used to reduce variability and improve interpretability.
- The impact of normalization on reliability parameters is not fully understood.
Purpose of the Study:
- To investigate how normalization affects reliability parameters.
- To examine the impact of normalization on maximum force values for trunk extension and flexion.
- To determine if normalized data is suitable for reliability calculations.
Main Methods:
- 85 healthy individuals (42 women) underwent maximum isometric force tests for trunk muscles at two-week intervals.
- Measurements included original and anthropometrically normalized force values.
- Reliability and agreement were assessed using intraclass correlation coefficient (ICC), standard error of measurement (SEm), standard error of the mean (SEM), and coefficient of variation of the method error (CVME).
Main Results:
- Original force data showed good reliability (ICC > 0.88).
- Normalization led to lower ICC values for the entire group (Extension: 0.803, Flexion: 0.768).
- Deviations in ICC varied between subpopulations (women and men).
Conclusions:
- Normalization of measured values can alter calculated reliability parameters.
- The use of normalized data is not recommended for reliability calculations.
- Original measurement data should be preferred for assessing the reliability of trunk muscle force measurements.
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