# Handgrip Strength as a Distinguishing Factor of People Training Partial Arts
## 2 Materials and Methods  
The authors of the study conducted the survey personally. All surviving participants attended several independent sports events, including instructor mastery courses and advanced training sessions that took place during 2018-2022 in Poland and Germany. The athletes were asked if they had undergone any surgeries in the past year, specifically involving the upper limbs. We also confirmed that they were free of muscle pain or stress injuries. No other specific criteria except age above or equal to 18 and higher belt ranks (higher skill levels) were used to choose survey participants. Those who did not meet the criteria were excluded from the analysis. Thus, the participants that accepted the invitation were weighed, had their HGS measured, and declared their belt rank, age, and years of training. The data were collected from 178 participants tested for their age, weight, years of training, style (modern Jujustu--two groups, karate Shotokan, karate Kyokushin), skill level (Kyu or Dan grade), gender, and handgrip strength (HGS).  
HGS is a widely used fitness test in judo and karate to evaluate upper-limb strength [46]; it correlates with body mass [47] and composition [16]. However, HGS has been shown to be ineffective in differentiating athletes who train in BJJ [48]. Studies have shown that HGS can differentiate between the skill levels of white and black belt judokas, making it a valuable tool in martial arts [49]. Moreover, experienced athletes practicing arm wrestling seem to have higher handgrip strength [50]. Taken together, these findings suggest that HGS could be useful in differentiating athletes practicing distinct martial arts.  
The Kyu and Dan ranks were incorporated into the analysis as they were suggested to be correlated with body mass and HGS [51].  
Groups of participants:  
Group 1--Jujustu 1, athletes from Poland (24 persons)  
Group 2--Jujustu 2, athletes from Germany (97 persons)  
Group 3--Karate Kyokushin (35 persons)  
Group 4--Karate Shotokan (22 persons)  
The HGS test, involving the dynamometric measurement of hand force, was carried out as follows: a KERN MAP 130K1 (manufactured by KERN) palm hand dynamometer was used. The subject squeezes the hand dynamometer with their stronger hand. The wrist should lie along the extension line of the forearm. During this testing, the test hand must not touch any part of the body [31; 52]. The strength of the hand is measured in kilograms. The better measurement of the two tests is selected for further analysis. The dynamometer should be adjusted to the size of the hand of the subjects so that the more distal finger joints fit in its handle. Hand swings during measurements are not allowed because they can alter the results. Subjects need to focus mentally on the task since the goal is to measure the maximum HGS force of the subjects [52].  
Pearson and Spearman correlation coefficients, analysis of variance, and principal component analysis (PCA) were conducted in XlStat (v. 2020.5.1) software [53]. ANOVA and Tukey's post-hoc test were performed in XlStat (v. 2020.5.1) software [53].