Establishing the reliability and validity for GripAble: A handheld sensor-based dynamometry device

Evaluation of maximum grip strength (MGS) is commonly conducted to guide intervention planning and evaluate treatment outcomes for individuals with hand or upper limb impairments. While the hydraulic Jamar dynamometer is recognised as the gold standard measurement instrument, it has several limitations and there has not been a consensus on whether alternative instruments can replace or complement it. This study aimed to determine whether a new electronic rehabilitation device, the GripAble, is a reliable and valid instrument for measuring the MGS of healthy adults when compared to the gold standard hydraulic Jamar dynamometer. It also sought to compare the user's experience when using the two instruments.

Fifty-five healthy adults completed two MGS assessments ten minutes apart using a standardised protocol. Test-retest and inter-instrument reliability were evaluated using intraclass correlation coefficient. Concurrent validity was established using a Bland-Altman plot. Relationship and level of agreement between measurements on the two devices were evaluated. Participants' user experience was explored through a quantitative survey.

The GripAble was found to have excellent test-retest reliability (ICC = 0.971-0.975) and good-to-excellent inter-instrument reliability (ICC = 0.898-0.922) with the Jamar dynamometer. Its measurement output is equivalent to approximately 63.3% of that of the Jamar dynamometer. The mean difference value between the measurements on the two devices was 9.44 kg (SD = 4.47). Users preferred the GripAble.

While the GripAble is a reliable MGS assessment instrument, it should not be used interchangeably with the Jamar dynamometer for repeated measurements of the same individual owing to the differences in their readings.