# Hand Joint Hypermobility among Dental Students--A Cross-Sectional Study
## 4 Discussion
### Hypermobility Is Associated with Lower Muscle Strength  
Our results suggested that individuals with higher finger hypermobility exhibited lower muscle strength, namely reduced bilateral lower grip and pinch strength. This corroborated the findings of other investigations that have revealed strength and proprioception deficits in patients with hypermobility [15; 42; 43]. The main reason for this appears to be attributed to a significant tendon laxity, rendering them unable to effectively transmit the power generated by the muscles [44]. Interestingly, a study found that males, but not females, with hypermobility showed lower muscle strength [22]. Future studies should be designed to confirm our findings, as to the best of our knowledge, this is the first study that specifically assesses a correlation between muscle strength and hypermobility in participants' hands. Moreover, for the present study, three measures of muscle strength were selected (e.g., grip pinch, lateral pinch, and three-point pinch strength). Future research should incorporate other assessment measures, such as palmar pinch strength, power grip strength, key grip strength, finger abduction/adduction strength, or finger flexion/extension strength, among others. It is important to note that the negative association between the severity of hypermobility and muscle strength did not take into consideration potential confounding factors derived from one's age, body mass index (BMI), and/or physical activity level. Age is a crucial factor as muscle strength tends to naturally decline with increasing age, attributable to a 3-8% loss of muscle mass per decade after the age of 30 [45] and reduced muscle function [46]. As such, failing to adjust for age may lead to an inaccurate overestimation of the relationship between these variables. However, the age range within our sample population was limited, spanning from 21 to 27 years. Given that previous studies have consistently reported a notable decline in muscle strength beyond the age of 30 [45], it is unlikely that this confounding factor significantly impacted our findings. Moreover, the results of another study have questioned the existence of a relationship between age and hypermobility [47]. However, that study focused specifically on 14-year-old adolescents, which may not accurately reflect possible associations observed in older age groups. A second confounding factor is the body mass index (BMI). BMI can influence muscle strength in that higher BMI values are often associated with increased body weight and potentially more muscle mass [48]. This has also been confirmed in studies specifically examining handgrip strength [49]. Although in this study the students' BMI was not assessed, it should also be noted that BMI alone does not provide a complete picture of body composition, and other factors such as the muscle-to-fat ratio can vary among individuals with the same BMI [50]. Finally, physical activity levels can significantly affect muscle strength. Individuals who engage in higher levels of physical activity tend to exhibit overall stronger muscles, regardless of their joint hypermobility status. Various studies have specifically examined the impact of structured exercise programs on muscle strength in people with generalized joint hypermobility. These investigations have shown increased muscle strength in specific areas, such as knee extensor muscle torque [51], shoulder strength [52], and trunk muscle endurance [53]. Nevertheless, a recent randomized controlled trial involving women with joint hypermobility failed to demonstrate any improvement in muscle mass and muscle strength in knee extensors [54]. These differences in findings may be attributed to variations in the studies' assessments of strength, different resistance levels, and training frequency. Moreover, the fact that the aforementioned study exclusively included females could also contribute to the contradictory findings.