Musculoskeletal injuries can be a result of participation in sports activities or carrying out physical activities for health benefits [1]. The causes of musculoskeletal injuries result from a complex interaction of multiple risk factors and events [2]. Range of motion (ROM) has been known as one of the risk factors for increased musculoskeletal injuries [3,4]. Musculoskeletal flexibility is defined as the ability to move a joint through its complete ROM, and therefore it is important to maintain flexibility as decreased ROM is a contributing risk factor for injuries [5].

Exercises to enhance flexibility can improve overall performance of athletes by preventing injuries with subsequent increase in ROM. Moreover, many athletes and others continue with their daily physical activities to increase the rate of performance in an event and for various health benefits; at the same time they are exposed to the risk of injuries caused due to fatigue. Arnason et al. [6] established that injuries occurring during the time of training or physical activity were musculoskeletal injuries. Thus, it is important to increase flexibility or ROM for enhancement in performance and to prevent musculoskeletal injuries.

Type V collagen is a minor component of tissues containing type I collagen, such as skin, tendons, ligaments, bone, cornea, and blood vessels [7]. COL5 Va1 (COL5A1, SNP rs12722) has been located on chromosome 9 in humans [8], and SNP rs 12722 produces two alleles of the COL5A1 gene, namely, the COL5A1 rs 12722 C-and T-alleles. Recently, studies on COL5A1 have been represented 1) Ehlers-Danlos syndrome (EDS) and 2) injuries (running performance, achilles tendon injuries, and ROM). Most patients with classic EDS have disease-causing mutations within one copy of their COL5A1 genes, which results in a loss of function of the mutated gene and a 50% reduction in the production of type V collagen [9].

A common C to T single nucleotide polymorphism within the COL5A1 gene is associated with a number of sports injuries or performance-related phenotypes [10]. Posthumus et al. [11] suggested that the CC genotype of COL5A1 was under-represented in female subjects with anterior cruciate ligament ruptures. The causes of ‘‘increased risk’’ phenotype may be the result of increased musculotendinous stiffness and decreased ROM [12]. Moreover, Collins et al. [10] established that COL5A1 is independently associated with lower limb ROM in Caucasian subjects. Since the abnormal ROM has been reported to be associated with injuries, it is important to identify genetic factors for ROM.

However, association between COL5A1 genotype and ROM in Asian people is still unclear. Therefore, the aim of our study was to investigate the association between COL5A1 genotype and flexibility as measured by the passive straight leg raise (SLR) and whole body join laxity in general Asian college students.

The present study is the first of its type to investigate the association between COL5A1 genotype and ROM in general Asian college students. The main finding of the study was the presence of association between SLR ROM and COL5A1. Moreover, an increasing trend in WBJL ROM was noted in subjects with COL5A1 CC genotype, which was not significant. The physical parameters including height, weight, and BMI were higher in < 90° group than > 90° group. Previously, association between COL5A1 genotypes and straight leg raise ROM in Caucasian population has been reported [16]. In addition, a positive correlation between COL5A1 genotype and ROM has been established in a group of South African participants [1]. An overexpression in CC genotype has been reported in individuals with greater ROM [17]. CC genotype collagen fiber containing large irregular and small fibrils. These mutations cause Ehlers-Danlos Syndrome (EDS), which has been demonstrated to have a detrimental effect on the habitual level of physical activity within the patients. Also, the study demonstrates presence of a mixture of large and small irregular fibrils in EDS. In addition, TT genotype collagen fibers containing smaller more densely packed fibrils have been reported. The fibrils, which are proposed to have an increased stiffness and/or creep inhibition, are associated with reduced joint ROM, increased risk for specific musculoskeletal soft tissue injuries, and faster endurance running performance. [10]. COL5A1 gene encodes ɑ1 (V) chain of type V collagen and a mutation in this gene, which causes haploinsufficiency, results in 50% reduction of type V collagen, and leads to poorly organized fibrils, decreased tensile strength, and reduced stiffness of connective [11]. It has been suggested that due to reported association with tendons, individuals with a TT genotype would have less extensible tendon structures, resulting in a lower range of motion (ROM) as compared to individuals with at least one copy of the C allele [10].

The reduction in ROM leads to concomitant reduction in physical activity [18], or an alteration in collagen integrity with increasing age [19]. Brown et al. [1] reported that SR ROM tended to increase with age in those subjects with COL5A1 CC genotype, while there was little or no correlation in the other two genotypes. Bertuzzi et al. [20] reported no significant differences between COL5A1 genotypes for ROM in physically active men. Saunders et al. [21] stated that COL5A1 genotypes might interact with age for ROM in physically active subjects. On the other hand, Goncalves-Neto et al. [22] and Satomi et al. [23] reported that damaged and pathological tendons contained relatively higher proportion of collagen type V, and these alterations were accompanied by a reduction in type I collagen. Thus, according to COL5A1 genotype might be increase rate of injuries in elderly. However, in the present study, subjects were young college students, and there were significant differences in the three COL5A1 genotypes with SLR.

The present study has some limitations. We did not consider the levels of physical activity and exercise. We assumed that there were no significant differences in physical activity levels and exercise experienced. However, physical activity and exercise levels should be considered in future studies. Another limitation is that sample size was relatively small, and further studies with larger populations are required to validate our findings. The primary aim of the study was not intended to investigate gender-specific genetic risk factors, and therefore further research is required.

In conclusion, our data indicates association between the COL5A1 genotypes and SLR in young Asian population. CC genotype of COL5A1 has been found to be associated with increased SLR ROM. Although present study shown that did not significantly in WBJL but increased tended to CC genotype. Therefore, present findings provide preliminary evidence on association of COL5A1 genotype with ROM in Asian population.