###### Abstract  
Manual dynamometry (HHD) allows for the assessment of musculature because its use has been supported as an indicator of health in different population groups. The objective of this study was to examine the reliability and validity of the Activ5 dynamometer for assessing grip strength in a population of adults. A total of 106 individuals with an age of 20.38 \(\pm\) 1.64, body mass of 71.52 \(\pm\) 11.32 kg, and height of 1.70 \(\pm\) 0.11 m were evaluated during two sessions. A cross-sectional agreement study was conducted on Sports Science students from a university community, and 106 individuals were evaluated during two sessions. Statistical analysis of reliability and validity was performed using intraclass correlation coefficients (ICCs), Pearson correlations, and Lin's coefficient. According to Lin's coefficient, both instruments measure grip strength for both conditions, either for the right hand or the left hand. The correlation coefficient to determine the linear relationship between both instruments determined that between the Jamar right-hand dynamometer and the right-hand Activ5, a coefficient R\({}^{2}\) = 0.580, \(p\) = 0.00, was obtained. In contrast, the correlation between the Jamar left-hand dynamometer and the left-hand Activ5 had a coefficient R\({}^{2}\) = 0.543, \(p\) = 0.001. Both intraclass correlation coefficients and Cronbach's alpha presented high values, indicating that both instruments have good reproducibility in their measurements. The Activ5 dynamometer cannot be used interchangeably with the Jamar dynamometer; however, the close values reported make it a reliable tool in grip strength assessment. The different characteristics of the Activ5 instrument, such as its ergonomics, weight, portability, wireless connection, dimensions, and applications, make it a promising daily- use tool for assessing, monitoring, and the prescription of physical activity and exercise. Manual Muscle Tester is valid and highly reliable for testing between trials and days. Clinicians should be diligent in ensuring that their HHD instruments are clearly marked so that the same device is used consistently to evaluate a given patient [9]. Meanwhile, the study developed by [PERSON] [10] affirms that manual dynamometry is a good portable alternative that allows objective measurements of muscle strength to be obtained where measurements must be reliable and valid. According to [PERSON] [11], manual dynamometry is a reliable tool for isometric muscle assessment, providing valuable information in different population groups, especially those characterized by physical inactivity, sedentary lifestyle, and low grip strength [12; 13]. In the scientific community, grip strength assesses people's physical function based on muscle strength measurement, frailty [14], sarcopenia [15], and cardiovascular risk [16; 17]. Grip strength assessment has also been a determining variable in the physical condition of healthy populations, especially as a predictor of mortality risk and to monitor the rehabilitation process [18; 19; 20]. Although various instruments have been developed to assess grip strength, including fixed dynamometers and manual grip dynamometers, the Jamar hand dynamometer (Lafayette Instrument, Lafayette, IN, USA)) is the most widely used for clinical contexts and research [21]. This is because the Jamar dynamometer guarantees excellent reliability and is considered the gold standard in grip strength assessment [22; 23]. However, manual grip as a health indicator demands appropriate reference values and cutoff points aiming to classify grip strength to adjust these parameters to the specificities of each context [24; 25]. Here, grip strength assessment using the Jamar dynamometer has allowed for the establishment of reference values for various age groups to make future clinical decisions [26; 27]. In the same vein, manual grip assessment responds to a specific methodology for its evaluation.