Handgrip strength assessment in breast cancer patients: validity and reliability of the Activ5 dynamometer

Hand dynamometry is a widely accepted method for measuring muscle strength and serves as a crucial clinical indicator, particularly in populations with chronic health conditions, such as cancer. Despite its growing use, no prior study has evaluated the validity of the Activ5 portable dynamometer in individuals with cancer. This study aimed to determine the reliability and validity of the Activ5 for assessing handgrip strength (HGS) in a population of female cancer survivors. The sample consisted of 22 women (mean age 53.91 ± 5.93 years; body mass 65.85 ± 14.52 kg; height 1.65 ± 0.04 m), who were assessed across two testing sessions in a cross-sectional concordance design. Reliability and validity were analyzed using Pearson correlation coefficients, intraclass correlation coefficients (ICC), and Lin's concordance coefficient. Results demonstrated very strong correlations between the Activ5 and the gold-standard Jamar dynamometer. For the right hand, r = 0.895 (p = 0.001), and for the left hand, r = 0.893 (p = 0.001). Lin's ICC for the right hand was 0.995 (95% CI: 0.974-1.016), and for the left hand 0.990 (95% CI: 0.959-1.020). These findings indicate excellent agreement and support the use of the Activ5 as a valid and reliable tool for evaluating HGS in cancer survivors. Its portability and ease of use make it a practical option for both clinical and research settings.