Cristina Cadenas-Sanchez, Guillermo Sanchez-Delgado, Borja Martinez-Tellez, José Mora-Gonzalez, Marie Löf, Vanesa España-Romero, Jonatan R. Ruiz, Francisco B. Ortega; Reliability and Validity of Different Models of TKK Hand Dynamometers. Am J Occup Ther 2016;70(4):7004300010. https://doi.org/10.5014/ajot.2016.019117
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© 2021 American Occupational Therapy Association
OBJECTIVE. We examined the reliability and validity of the analog and digital models of TKK handgrip dynamometers using calibrated known weights.
METHOD. A total of 6 dynamometers (3 digital and 3 analog; 2 new and 1 old for each model) were used in this study.
RESULTS. Intrainstrument reliability was very high; systematic error for test–retest reliability was ≤|0.3 kg|. The systematic error among different instruments (same model) and between different models (digital vs. analog) ranged between |0.4 kg| and |0.6 kg|. The systematic error between new and old dynamometers ranged from |0.8 kg| to |1 kg|. All dynamometers provided lower values for the same known weights than a SECA scale, with a systematic error ranging from −0.94 to −2.64 kg.
CONCLUSION. This study indicates that clinicians and investigators who provide treatment to address handgrip strength should use the same instrument and model for repeated measures. Distinguishing meaningful change from dynamometer variability is discussed.
The TKK dynamometer is a useful tool for hand grip assessment with good reliability and validity and higher precision, reliability, and validity than other dynamometers such as the Jamar (España-Romero et al., 2010).
Practitioners providing hand therapy should use the analog version of TKK, rather than the digital version, because it allows assessment of handgrip strength in patients with very low strength levels.
Findings support the recommendation to use the same instrument to measure hand strength because interinstrument reliability adds a certain amount of error.
This study provides objective estimates of systematic error so that practitioners, researchers, and anyone who needs to compare data from two different time points can distinguish between the variability of the instrument itself and a meaningful change in handgrip strength attributable to an intervention program or hand therapy.
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