Our results show that the Camry dynamometer is a valid tool for measuring handgrip strength in older adults before elective surgery, with an excellent agreement that did not differ significantly from zero when compared with the currently gold standard Jamar® dynamometer.

To our knowledge, there are few studies comparing the Camry dynamometer to the gold standard Jamar® dynamometer in older adults, with conflicting results. Huang et al. carried out a study on 1064 healthy community older adults showing excellent reliability and validity when comparing both devices (Huang et al. 2022). However, Diaz Muñoz et al., who studied 133 healthy adults over 18 years old, only showed a good agreement in the age group from 40 to 59 years old; nevertheless, the study only includes 43 older adults (Muñoz and Millán 2019). Handgrip strength might change with different shoulder and elbow positions (Su et al. 1994) without a significant difference between standing and sitting positions (Sousa-Santos and Amaral 2017). This could explain partially the lower average difference obtained in our study compared to the abovementioned ones. In our study, patients were seated with their forearm resting on the arm of the chair using Southampton protocol (LinY et al. 2021) using the same position for both devices. Instead, in Diaz Muñoz et al.’s study, measuring posture was standing with the elbow flexed at 90° for both devices (Muñoz and Millán 2019), and in Huang et al.’s study, measurements with Jamar devices were in a sitting position with a 90° flection using American Society of Hand Therapists protocol and in standing position for Camry dynamometer (Huang et al. 2022). When using a sitting position with the forearm resting over the chair’s arm, it is difficult to use other muscles from the arm and shoulder, and this could give smaller variability between measuring tools.

Previous research shows a variation in grip strength by gender with a higher grip strength in men than in women at all ages and a change associated with age, with a lower grip strength at older age which is concordant with the results of our study (Sousa-Santos and Amaral 2017).

In our secondary analysis, we found an homogenic decline of hand grip strength with age and a difference between women and men, with greater hand grip values for men, which is consistent with previous evidence (Mancilla et al. 2016; Dodds et al. 2016).

Low handgrip strength can be used as a sole predictor of bad outcomes in older adults (Rijk et al. 2016), and in surgery settings, there is evidence that low hand grip strength is associated with increased postoperative morbidity, mortality, and hospital length of stay (Sultan et al. 2012). Having a less expensive device and a valid tool to assess hand grip strength could be broadly used among health centers with different financial resources.

This study has several limitations: the Camry dynamometer we used was newly purchased, and the manufacturer suggests a periodic calibration every 18 months and not in the beginning of its use, so we assumed the device was calibrated. Also, future studies are needed to assess the results after the time of recommended calibration.

There are different recommendations in regard to how many trials should be done to reach maximal handgrip effort and also regarding the rest time between attempts. Most studies suggest 2 to 3 trials with 15 to 60 s of rest between them (Núñez-Cortés et al. 2022). Since the aim of our work was to assess the reliability between two tools, we decided to do 2 attempts to achieve the device’s learning objective of repetition but avoid fatigue. This could have compromised our results since the Camry measurement was the third and fourth (after 2 attempts with Jamar) and could have been systematically better, but there are no biased results in our study given the limits of the agreement are not positively biased. To avoid this issue, a randomized assessment could have been done, but it was not considered in our research, which implies a limitation. Finally, this study was done in an elective preoperative setting, but might be applicable to other settings.

In conclusion, the Camry dynamometer is a valid device to measure hand grip strength in older adults, and it could be considered as an alternative to Jamar gold standard in a preoperative setting and it might be considered in other settings as well. Moreover, being a less expensive device, it could be broadly used among medical centers regarding their budget.