# Handgrip Strength as an Indicator of Overall Strength and Functional Performance--Systematic Review
## 3 Results
### Dependence Between Hand Grip Strength and the Values of the Moments of Muscle Forces in Upper limbs
[33] performed isokinetic tests of adduction and abduction in the shoulder joint, as well as the isometric flexion and extension of the trunk. They applied a multiple linear regression model and developed four predictive equations. The regression equations obtained for the trunk flexion and extension were statistically significant. The authors found that predictive equations calculated for the shoulder joint may constitute an alternative method to the measurement of hand grip strength. Scientific literature features investigations searching for the dependences between hand grip strength and the moments of muscle forces in the trunk and lower limbs [11; 26; 34; 35; 36]. Such studies focus on the testing of muscle force moments in isometric conditions [23; 34] and isokinetic conditions [26] in the scope of the hip, knee and tarsal joints [11; 34], as well as on the measurements of moments of forces in the trunk muscles [34]. One can also find studies which search for the dependence between hand grip strength and global muscle strength, which was defined as the total sum of force moments of the muscle groups tested [34; 36]. Hand grip strength was most often tested in a sitting position [11; 26; 34; 35]. The tests were performed mainly with the participation of elderly individuals and focused on the comparison of the correlation coefficient values between age groups of elderly people [11; 26; 34; 35], for instance, in the following age ranges: 60-70 and 71-86 years of age [26], or 60-69, 70-79, 80 years of age and more [35]. As a result of the literature review, only one article was found where the study group was in the age range from 8 to 20 years of age [36]. Only [PERSON] et al. [11], seeking out dependences, decided to apply Orthogonal Projection to Latent Structures, i.e., the OPLS regression model. Other authors used the Pearson linear correlation for the assessment of dependences [26; 34; 35; 36]. [PERSON] et al. [11] showed that there exists a strong and valid model demonstrating the relationship between hand grip strength and lower limb strength. [PERSON] et al. [34] tested not only the dependence between hand grip strength and the moments of muscle forces exerted on the joints in the lower limb and the trunk, but also calculated global muscle strength, defined as the total sum of all measured moments of muscle forces. Value R of the Pearson linear correlation was within the range of 0.369 to 0.7 (all values statistically significant). The authors observed that hand grip strength may be applied to show global muscle strength in elderly people (HG and global muscle strength--R = 0.69, \(p<0.05\)). The researchers noticed that the dependence between hand grip strength and all muscle groups reached low-to-moderate values. The authors think that positive linear dependence eliminates the necessity of testing different muscle groups, if necessary. [PERSON] and [PERSON] [35] obtained different results while testing the extensors and flexors of the knee and hip, as well as the adductors and abductors of hips. On the basis of the results obtained by the authors, it was possible to determine the range within which correlation values fall, i.e., from 0.56 to 0.78 (\(p<0.01\)). On the grounds of their results, they came to the conclusion that hand grip strength poorly reflects the changes in the muscle forces of lower limbs. The researchers suggested that a better alternative method was the measurement of the maximum isometric moment in the knee joint. Additionally, within the scope of their research, they estimated how strength decreases in the age groups of octogenarians in relation to sexagenarians, and found that the relative reduction in muscle strength falls into the range from 14.3% to 27%. [PERSON] et al. [26] also obtained the Pearson correlation coefficients between hand grip strength and the moments of muscle forces of lower limbs in isometric and isokinetic conditions. However, they were deemed scarce or low (r from \(-0.067\) to 0.391), and most of them did not show any statistical significance.