# Handgrip Strength as an Indicator of Overall Strength and Functional Performance--Systematic Review
## 4 Discussion
In five analyzed articles [11; 26; 34; 35; 36], the dependence was sought between hand grip strength and muscle strength of the lower limbs, including three articles indicating a positive linear dependence [11; 34; 36], 1 showing the lack of dependence [26] and 1 revealing a weak dependence [35]. Among other researchers, [PERSON] et al. [34] reached the conclusion that the very measurement of hand grip strength was sufficient to assess the strength abilities of a particular muscle group; however, it could not be used if there were contraindications against using an isokinetic dynamometer, e.g., recent injuries. However, the greatest interest among researchers was aroused by the search for dependence between hand grip strength and strength abilities of the muscles in the knee joint. Such a relationship was sought after in 16 articles in total [8; 11; 24; 25; 26; 32; 34; 35; 37; 38; 39; 40; 41; 42; 43; 44]. Seven independent studies found a positive correlation [11; 34; 37; 38; 40; 41; 42]; four articles [24; 32; 35; 44] advised a cautious approach to hand grip strength as a muscle strength predictor or recommended further investigations; three articles informed about the lack of dependences [25; 26; 39]; finally, two articles did not clearly state if it was a proper predictor [8; 43]. At the same time, one of the articles, which defined the dependence as weak, informed that the best approximate predictor is the values of moments of extension and flexion forces in the knee joint [32]. It is important to note the correlation values that have been obtained in previous studies. Some authors have conducted studies on a large group of people and obtained low statistically significant correlation coefficients [25; 36; 38], so caution should be exercised in drawing firm conclusions. The observed relationships between hand grip strength and muscle torque may be influenced by anatomical factors, neuromuscular coordination (motor unit recruitment), lifestyle and diet. Hand grip strength is a function of muscle mass and cross-sectional area. Greater muscle mass throughout the body (e.g., in the upper limbs, arms or forearms) is directly related to a greater ability to generate force in the hand. In addition, the type of muscle fibers (fast-twitch or slow-twitch) affects both hand grip strength and the strength generated by other muscle groups. Based on the review, we suggest that hand grip strength tests should be conducted in accordance with the recommendations of the American Society of Hand Therapy. However, in the case of muscle force moments, the test position depends on the joint being tested, so we recommend that it be in accordance with the recommendations of the manufacturer of the measuring device. As results from the conducted systematic review of the literature, only half of the analyzed scientific articles showed correlation between hand grip strength and the moments of muscle forces in the trunk, upper and lower limbs. Methodological differences in testing, such as different measuring position of participants, elbow placement, age, gender, presence of disabilities, type of instruments used [45; 46; 47], and study size, can influence the analyzed correlation results. These factors may reduce comparability between studies, and lead to discrepancies in findings. Therefore, standardizing measurement protocols is crucial to ensure more reliable and consistent outcomes. No irrefutable conclusion about the existence of dependences can be reached in age groups and with reference to the results obtained for particular parts of the body. Due to significant discrepancies in the research so far, hand grip strength should not be automatically applied as an indicator of overall strength and functional performance. The measurements of hand grip strength and the moments of muscle forces should complement each other.