## 4 Discussion  
In this study, we studied relationship between mean and relative HGS and BMS and iMetS using a 16-year follow-up of the population-based cohort. The present study revealed that BMI-, weight-, and WC-relative HGS and BMS at baseline were independently associated with iMetS in men and women. In addition, the changes in muscle strength over 16 years was significant in iMetS in men. Unfortunately, baseline LPA and these changes were not associated with iMetS. The results of changes in muscle strength and LPA that had not been previously demonstrated were shown here. Additionally, we showed that iMetS components were strongly associated with a one standard deviation increase in relative HGS and BMS both in women and men. Muscle strength can be measured in various areas, such as the knee, elbow, hand, leg, and back [15; 35; 36]. Additionally, it can be measured by an isokinetic dynamometer, cardiorespiratory fitness, dual-energy X-ray absorptiometry (DEX), and bioelectrical impedance analysis (BIA) [37]. Several studies have been reported, varying by the measurement site and measurement method, but there are few studies compared to those for HGS due to problems such as the measurement difficulty, high test cost, and challenges in validation [37; 38]. Therefore, HGS is being used to research muscle strength in clinical and epidemiological studies [8]. Body composition and body size-independent measurements for muscle strength are important. The use of a relative method is recommended when investigating the relationship between diseases such as T2 DM, HTN, MetS, and dementia [8; 9; 10; 11]. Therefore, BMI-, weight-, and WC-relative muscle strength are frequently used methods for normalizing muscle strength [15]. The relevance of MetS components, iMetS, and HGS has also been reported in previous reports. Lower HGS was associated with incident T2 DM [15; 39; 40], and meta-analysis results using the results of 10 observational cohort studies also demonstrated its relevance to DM [8]. Weak HGS is associated with HTN [9; 41]. The results of HGS and MetSshowed contradictory results. In women, all results showed no association results [17; 18]. Some of the results showed significant results in men [24]. Weight- [16; 20; 21; 23] and BMI-relative [4; 17; 18; 19] HGS were consistently associated with MetS both men and women. In addition, weight-relative HGS was associated with iMetS in both men and women [26]. In our results, BMI-, weight-, and WC-relative HGS were related to iMetS. The mean HGS was not significant. Moreover, sarcopenia is the age-related loss of skeletal muscle mass, quality, and strength [42]. The results of the meta-analysis using the results of 13 observational studies also demonstrated its relevance to MetS (2.01 fold) [43]. The development of MetS by HGS change has not been reported. Our results show that the decrease in HGS in men was significantly associated with iMetS. Unfortunately, LPA was not relevant to the iMetS in our results. These results can be explained through previous reports that aerobic exercise does not significantly affect HGS. Therefore, resistance exercise is needed to improvement HGS [44; 45]. In addition, in a four-year follow-up study, iMetS did not differ by moderate-LPA, but was only 0.36-fold lower in groups with a vigorous LPA of more than 7.5 METs per week for more than 60 min [34]. Another study showed an association with a 0.54-fold increase in MetS of more than 990 MET-minutes per week [46]. The baseline average leisure activity of the subjects in this study was 127.0 MET-minutes per week for women and 125.3 MET-minutes per week for men, showing very low LPA compared to previous studies. The difference between baseline and eighth follow-up HGS and relative HGS were significantly reduced in women. LPA was not different in women. On the other hand, men showed significant increases in HGS, relative HGS, and LPA. In our results, men showed high iMetS and decreased HGS.