1. Introduction
ostural control is a complex process, involving the center of gravity maintenance within the base of support. Moreover, it requires the co-ordination of the somatosensory, visual, and vestibular systems [1]. The information provided by these three systems is executed by the Central Nervous System (CNS) and integrated in the form of an appropriate motor response to maintain body balance. Balance is actively controlled by the CNS, which predicts the perturbations of whole body or trunk movements. A key feature of balance is stability. Stability is related to motor control resistance and a smooth state without changing in response to a perturbation or oscillations creating perturbations. Typically, if the posture returns to its original state during the perturbation, it is considered as stable. Somatotype is a means of describing human body shape and condition in addition to height and weight; it can affect postural control [10-12]. Somatotype is also used to determine the body types most exposed to various diseases. Studies have examined the relationship between body type and health status [14-16] and physical activity [15, 17, 18]. Previous studies have reported that postural control is different in different somatotypes; however, they only examined the effect of somatotype on static or dynamic control in one age group. Thus, we examined the relationship between somatotype and static, semi-dynamic, and dynamic postural controls in adolescent, young, and middle-aged females.
2. Participants and Methods
A total of 140 females aged 12-50 years (Mean±SD of age=26.45±10.94 y) with no skeletal abnormalities, lower extremity pain, and injury, as well as vestibular and neuromuscular injury were included in the study. The study participants’ anthropometric characteristics were measured. Then, they were classified into three groups of ectomorph (n=46), mesomorph (n=45), and endomorph (n=49) based on the heath-carter method. Somatotype was determined based on the dominant component, i.e. ≥1.5 units of difference from the other two components [13]. After determining the somatotype, the Y Balance Test (YBT) was performed to evaluate the study subjects’ dynamic control.
3. Results
One-way Analysis of Variance (ANOVA) results suggested a significant difference in the mean static, semi-dynamic, and dynamic balance scores between the three groups of an ectomorph, mesomorph, and endomorph. Table 1 presents the postural control measurement results of the somatotype group. In total, 46.7%, 28.3%, and 18.4% of the mesomorphs, ectomorphs, and endomorphs had the lowest error <3 in static postural control, respectively. This was also observed in the next category (3-6 errors). Regarding the highest error rate >15, only 8.9% of the mesomorphs had ˃15 errors, followed by ectomorphs with 10.9%, and endomorphs with 16.3%. In terms of semi-dynamic balance, a high percentage of mesomorph subjects (66.7%) gained the lowest error rate <10, followed by 43.5% of ectomorphs, and 36.7% of endomorphs (Table 1).
4. Discussion
The current study investigated the relationship between somatotype, and static, semi-dynamic, and dynamic balance. The obtained results suggested a significant difference in the static, semi-dynamic, and dynamic balance between three ectomorph, mesomorph and endomorph female groups. The mean static balance (i.e. the number of errors in the Balance Error Scoring System test) in the mesomorph group (6.66) was significantly higher than the ectomorph (8.64) and endomorph (10.22) groups. Chi-square test results revealed that the mesomorph group indicated the best, and endomorphs demonstrated the poorest performance in static balance. This finding is consistent with those of Lee et al. [12] who reported that mesomorphic girls had substantially better one-sided static stability, compared to endomorphic and ectomorphic girls; they also reported the somatotype components effects on the postural stability in young girls.
The achieved data highlighted that the mesomorphic subjects had a better balance performance, while the performance of endomorphs was poor. Muscle strength and structure are useful for joint stability and postural control; the might be the main reason for the better performance of mesomorphs in our study (previous studies have supported the same finding) [11, 12, 29]. Unlike some previous studies, the ectomorphs in our study had better postural control than endomorphs. Although the high height-to-weight ratio is a characteristic of ectomorphs, the Mean±SD height of these subjects (1.59±5.92) was not significantly different from that of endomorphs (1.59±6.35); however, the difference between the two groups was significant in weight. Therefore, the height of the center of gravity to the base of support, which is one of the main determinants of stability, has not been increased; the mass distribution was probably the factor that differentiated the postural control of ectomorphs and endomorphs. Studies have documented that obese people with an asymmetric distribution of fat, especially in the abdomen, are more prone to fall [8].
5. Conclusion
The mesomorphic component of somatotype was associated with postural control. Besides, the endomorphic component impaired balance more than the ectomorphic component. Comparing these findings with those of other studies revealed the necessity for further investigations regarding the postural control of three somatotypes.
Ethical Considerations
Compliance with ethical guidelines
Prior to the study, a written informed consent was signed by the subjects or their parents. They were assured of the confidentiality of their information and were free to leave the study at any time.
Funding
The present paper was extracted from the MA thesis of the first author, Mahbubeh Keivan, Department of Sports Biomechanics, Faculty of Physical Education and Sports Science, Islamic Azad University Central Tehran Branch, Tehran.
Authors' contributions
Conceptualization, methodology, software, validation, formal analysis, investigation, resources, data curation, writing - original draft preparation, writing - review & editing, visualization: Mahbubeh Keivan; Supervision, project administration: Heydar Sadeghi. 
Conflicts of interest
The authors declared no conflict of interest.

References