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Hand Size Reduces the Reliability of K-Force® Grip Dynamometer
Feray Karademir1, Özgün Uysal1, Şule Tüzen Tek2
1Faculty of Phyical Therapy and Rehabilitation, Hacettepe University, Ankara, Turkey.
Hand Therapy
|June 16, 2025
Summary
The K-Force® Grip shows good reliability but systematically underestimates grip strength compared to the Jamar®Plus+ dynamometer. These devices should not be used interchangeably for research or clinical grip strength assessments.
Area of Science:
- Biomechanics
- Rehabilitation Medicine
- Medical Devices
Background:
- Objective grip strength evaluation is vital for assessing patient function and treatment efficacy.
- A new smart device, K-Force® Grip, offers novel capabilities but differs in design from the standard Jamar®Plus+.
- Differences in circumference and adjustable grip width necessitate validation of the K-Force® Grip.
Purpose of the Study:
- To assess the validity and reliability of the K-Force® Grip dynamometer.
- To compare K-Force® Grip measurements with the Jamar®Plus+ across diverse hand sizes in healthy individuals.
Main Methods:
- Recruited 123 healthy subjects (246 hands), categorized by hand length and span.
- Measured grip strength using both K-Force® Grip and Jamar®Plus+ hydraulic dynamometers.
Main Results:
- Excellent inter-device consistency (ICC=0.937) was observed overall and for larger hands.
- Good consistency was found for other anthropometric groups, but absolute agreement showed high variability.
- Bland-Altman plots indicated K-Force® Grip systematically yielded lower grip strength values than Jamar®Plus+.
Conclusions:
- The K-Force® Grip and Jamar®Plus+ dynamometers are not interchangeable for research purposes.
- For clinical follow-up, the Jamar®Plus+ is recommended, particularly for adolescents due to ongoing hand growth.
