Reliability and validity of the K-force grip dynamometer in healthy subjects: do we need to assess it three times?

The K-force is reliable, but it underestimates grip strength by 4.5-8.5 kg compared to the Jamar dynamometer. K-force can be used to monitor progress over time but cannot be used to compare results against normative data. The use of a single measurement when assessing grip strength is sufficient when assessing healthy subjects.