The Effect of Eight Weeks of Proprioceptive Exercise with Closed Eyes on Static and Dynamic Balance in Ballerina Teenage Girls in Tehran Province

Ballet is not only a dramatic sport but also an activity with high physical needs. In ballet jumps and rotations, delicate movements, high flexibility and the final transition to the en pointe are performed in women (1). Every position and step in ballet requires postural control (2), and researchers consider static and dynamic balance and weight movement to be very important for motor function in ballet (3). A determining factor in maintaining balance is the size of the support surface, and ballerinas must perform some movements on very little support surface (3, 4). Doing these techniques on young ballerinas who have not had enough proper training can lead to numerous injuries (5). Balance is a key component of motor skills for maintaining posture and performing complex sports skills. It seems that maintaining balance and use training programs to improve it is a good solution that will help reduce the amount of falls during training or competitions (23). Balance is achieved through a variety of sensory input information to the CNS, including visual, vestibular, and sensorimotor (24, 25). It seems that by simultaneously stimulating the superficial and proprioceptive senses and creating sensory integration, it can increase the cortex's awareness of the organs and increase the balance this causes proper control during movement (9). Proprioceptive sense refers to the ability to integrate sensory information received from mechanical receptors and thus determine the position and movements of the body in space. Mechanical receptors for proprioceptive sensation in the muscles of the lower limb, soles of the feet, and around the ankle joint provide important information about the displacement and movement of the body mass center, as well as the characteristics of the impact surface for the CNS (7). Proprioceptive training includes activities that challenge the ability of the target joint to find and respond to input information about the position of the joint (11). Some evidence suggests that improving the proprioception of agonist muscle groups strengthens and stabilizes limb coordination, thus leading to improve movement during ballet (12, 13). Conversely, some studies show that ballerinas are more dependent on visual information to maintain balance (3, 14). Accordingly, the question of whether it is possible to increase balance by strengthening the sense of proprioception and also enhance performance in ballerinas has not been studied and needs to be investigated. Therefore, the purpose of this study was to investigate the effect of eight weeks of open or closed eyes balance training on static and dynamic balance in adolescent ballerina girls.

Twenty ballerina girls aged 8-15 years with a history of 6 months to 1 year ballet training were selected and divided into two groups of ten: 1- closed-eyes balance training (proprioceptive training) in addition to routine ballet training and 2- open-eyes balance training in addition to routine ballet training. Both groups participated in balance training for 8 weeks (3 sessions per week, 30 minutes to 1 hour each session) (15). The training movements used in the balance section were 14 items and were used from simple (exercises with hand support, with two legs and without interference) to complex (exercises without support, with one foot and with interference by the trainer) (14). 48 hours after the end of the last training session in both groups, post-test was taken. Stork balance test and star excursion balance test were used to measure static and dynamic balances, respectively. Before starting the research protocol, to eliminate the learning effects, the samples were asked to perform stork and star balance tests several times during the routine ballet training period. Analysis of variance with repeated measures was used to examine the data. If time was significant, the paired t-test was used to examine the post-test changes compared to the pre-test in each group, and if the group was significant, the independent t-test was used to examine the differences between the two groups in the post-test. Significance level was set at 0.05. All calculations were performed using SPSS statistical software version 21.

The results of repeated measures analysis of variance showed that the group (F1, 9 = 7.50, P = 0.023) and time (F1, 9 = 593.64, P = 0.001) effects on static balance were significant. The results of paired-samples t-test showed that there were significant difference in static balance scores between pre-test and post-test in the closed-eyes (P = 0.001) and open-eyes (P = 0.001) groups. The results of independent-samples t-test showed that static balance was significantly increased in the closed-eyes group compared to the open-eyes group (P = 0.006). The results of repeated measures analysis of variance showed that the time effect on dynamic balance (dominant foot and non-dominant foot) was significant but the group effect was not significant. The results of paired-samples t-test showed that there were significant difference in dynamic balance scores between pre-test and post-test in the closed-eyes (P = 0.001) and open-eyes (P = 0.001) groups.

The results of the present study showed that both types of balance training with open and closed eyes significantly improved static and dynamic balances in adolescent ballerinas. The result of the present study on the effect of exercise on dynamic balance is consistent with the results of Yalfani et al. (2017) (17), Ashoury et al. (2016) (18), and Sadeghi Dehcheshmeh et al (2015) (19). The results of the present study showed that closed-eyes training significantly increased static balance compared to the open-eyes training group, but in the dynamic balance there was no difference between the two groups. Gebel et al. (2018) set a minimum training duration of 12 weeks for significant balance improvement but found that 8 weeks could also be effective (15). In the present study, eight weeks of exercise improved balance in both groups, but the short duration of exercise probably had an effect on the results. Another reason could be the use of more static exercises in the present study, and therefore the significance of static balance in closed-eyes exercises compared to open-eyes exercises can be explained. The next point to consider is that open-eyes balance tests were used to assess balance in the present study, and it is possible that different results will be seen in closed-eyes balance tests. Finally, in the present study, the effect of exercise on ballet performance was not evaluated, and the stork and star tests used in the present study provide the opportunity to use more visual information to maintain balance, and as mentioned Ballerinas are more dependent on visual information to maintain balance. Therefore, if the ballet performance was evaluated according to its dynamics, it could be effective on the results. One of the limitations of the present study was the low volume of research samples, which was due to the small number of athletes active in this field according to the research criteria. Also, due to being in the growth ages, the age range of research samples was wide and it was not possible to form research groups in a more limited age range.