Reliability and validity of two hand dynamometers when used by community-dwelling adults aged over 50 years

The Jamar hydraulic dynamometer is a widely recognized tool for measuring grip strength. Nevertheless, the devices used most often in Asian countries are spring-type dynamometers, represented by the CAMRY dynamometer or Smedley dynamometer. We aimed to evaluate the reliability and validity of the CAMRY dynamometer compared with the Jamar dynamometer.

This was a cross-sectional study using a random crossover design in the grip strength test with two dynamometers. A total of 1064 healthy community-dwelling older adults aged 50-90 years old, which included 686 minorities and 378 Han Chinese, were recruited into the study from July to September 2021. We assessed the reliability and validity of the CAMRY EH101 dynamometer, and the Jamar dynamometer was regarded as the reference device. The order of testing with two dynamometers was randomized in a 1:1 ratio, with a 10-min gap between the two devices. Intraclass correlation coefficients (ICCs) and Bland-Altman analysis were calculated to assess reliability and validity between the two devices.

The average handgrip strength (HGS) values at six times by the Jamar and CAMRY devices were 25.0 ± 7.9 kg and 24.6 ± 7.5 kg, respectively. The ICC values between the two devices were 0.815-0.854, and the systematic bias underestimated by the CAMRY dynamometer was 0.5 kg in men and 0.6 kg in women. We carried out a linear regression equation by sex, and their relationship was found as follows: male HGS (kg)_Jamar = 8.001 + 0.765 × HGS (kg)_CAMRY; female HGS (kg)_Jamar = 3.681 + 0.840 × HGS (kg)_CAMRY.

The CAMRY EH101 dynamometer provides excellent reliability and validity. This device can serve as a reliable, inexpensive, and practical device to assess grip strength in geriatric clinical practice.

Chinese Clinical Trial Registry: ChiCTR2100046367 ; Date of clinical trial reistration: 15/05/2021.