Effect of four weeks of ocular-motor exercises on dynamic visual acuity and stability limit of female basketball players

Highlights

• Postural and visual stability depends on the afferent visual-auditory and deep sense.

• Dynamic vision is very essential in dynamic sports such as basketball.

• Oculomotor exercises can be used to enhance the limit of stability and dynamic visual.

Abstract

Introduction

Visual skills are an integral part of most daily activities and an effective indicator of the functional ability of athletes, particularly in the fields of dynamic sports like basketball. Despite the important role of vision and effect of ocular exercises on functional skills in athletes, a few studies have been conducted in this regard. Thus, this study aimed to investigate the effect of ocular-motor exercises on dynamic visual acuity and stability limit of female basketball players.

Methods

In this semi-experimental study 30 club elite female basketball players aged between 18 and 24 years, with at least three years of specialized basketball experience, were randomly assigned to two intervention and control groups. The athletes in the intervention group participated in the designed four-week program (six sessions per week) of the oculo_motor exercises. The control group did just their own daily routine exercises. The limit of stability was measured by the Biodex balance system SD and dynamic visual acuity was measured by the PowerPoint, which is for detecting dynamic visual acuity. Also, the SPSS software version 19 was used to analyze the data by using descriptive statistics methods: independent t and Paired t tests, at a significance level of P ≤ 0.05.

Results

The results showed that doing four weeks of the oculo_motor exercises led to a significant increase in the overall stability index (OSI) from 28/66 ± 7/23 to 51/60 ± 6/38 (p = 0.001), as well as in dynamic visual acuity from 29/73 ± 4/19 to 56/20 ± 8/81(p < 0.001); in the intervention group, these changes were also statistically significant in comparison with the control group and before doing the exercise protocol (p < 0.05).

Conclusion

According to the obtained results, the oculo_motor exercises can be used to enhance the limit of stability and dynamic visual acuity in basketball players and other dynamic sports.

Introduction

Basketball is a dynamic sport, in which the players are constantly moving and taking a new position every moment [1]. This displacement requires a re-analysis of visual information obtained from the new position, dynamic visual acuity, keeping balance, and controlling posture [2]. Basketball skills are based on the correct functioning of the visual system in addition to the physical fitness and specialized skills [3]. During this process, a basketball player focuses his eyes on the spatial position of the ball with environmental awareness of other players [1]. In fact, the sense of sight measures the orientation of the eyes and head towards the surrounding objects and plays an important role in keeping balance [4]. In order to attain the visual information, the eyes should be considerable time fixed on the ball before touching it with hand. Therefore, in order to create enough time to fixation and consequently the processing of visual information, object deployment should be done as soon as possible with the advent of an object or its quick movement or sudden change of position [1]. In such situations, the vestibulo-ocular reflex plays an important role in the coordination between the eyes and the hand [1,5]. Also, changing the head position leads to the activation of the atrial system and a change in the distribution of postures in the neck and organs influenced by the vestibulo-spinal and vestibulo-ocular reflexes [6].

Fast tracking the ball with eye is very important in the professional basketball game. In this sport, the dynamic visual acuity has a significant effect on the performance of athletes in addition to the static visual acuity [7]. Dynamic visibility refers to the clear vision of the athlete while moving or when the athlete follows an animated object [8]. Dynamic vision is very essential in dynamic sports such as basketball, volleyball and motorcycles [9].

Several studies have been conducted on whether vision skills are inherent in athletes or improved by regular practice [10]. In fact, the visual system responds to the loading principle like the musculoskeletal system [1,8]. Studies show that doing visual exercises results in an improvement in both vision skills and sport performance [11,12].

Ocular-motor can be mentioned as one of the visual exercises (Fig. 1). These exercises include neuromuscular control skills, which have evolved for the focus of vision system on the target and smooth pursuit for the moving target or one target jumping on another target [13]. The components of ocular-motor exercises include fixation, saccadic movements, smooth pursuit, and optokinetic and vestibular movements [3]. Saccadic and smooth pursuit movements of the eyes are important and essential in many aspects of sport [13]. Although dynamic visual acuity and the limit of stability are of the greatest importance, no study has been conducted on the effect of ocular-motor exercises on athletes to date. Therefore, the objective of the present study was to investigate the effect of oculo_motor exercises on dynamic visual acuity and limit of stability in female basketball players.

The current research is a clinical trial study. Thirty club female athletes with at least three years of continuous activity in basketball, with normal vision and hearing and the age range 18–24 years, were entered the study. The participants did not have a history of a direct blow to the neck or upper limb during the past month, lower limb injury in the last six months, history of drug consumption affecting neuromuscular function, acute and specific pains affecting the process of the test run. The people with musculoskeletal disorders affecting balance (forward head Posture), neuropathy, diabetic foot, dizziness and the problems related to the vision including refractive errors disorder, history of ankle fracture, double-sided ankle sprain, ankle injury in six months before the time of the research (history of ACL knee injury), performing surgery in the lower limb or participation in other rehabilitation programs, which were simultaneous with the present research, were excluded from the study [14]. Ethics approval was taken from the Research Ethics Committee for Tehran University of Medical Sciences, and all the participants were given a written informed consent. Then, the subjects were randomly divided into two intervention-control groups. The practice group did the exercises six days per week in the morning and evening during four weeks (morning exercises were done at home and evening exercises were done at the club). During the research, the control group maintained their own activity levels prior to participating in the study. The height and weight of each subject were measured using a Seca digital scale (model 703). In the pretest, PowerPoint and metronome were used to measure dynamic vision [4] and Biodex was used to measure the limit of stability [15]. It should be noted that all measurements were done before and after the exercise protocol (Table 1).

In order to measure the limit of stability, a Biodex Balance System SD (USA) was utilized. The intraclass correlation coefficient of this device ranged from 0.64 to 0.89. The subject's status when standing on the Biodex balance device was as follows: both feet were on the balance sheet, both hands were on the side of the body, and the trunk was straight and the subjects held their heads with open eyes opposite the monitor of the device. The test was repeated three times for 30 seconds and the rest interval between each repetition was considered to be 10 seconds. This test was done at difficulty level II. Also, the overall stability index and the time to reach balance were considered as the limit of stability [15].

In fact, dynamic vision is defined as the ability to detect details when there is a relative movement between the observer and the target object. It was measured by reading the numbers during neck rotation. A PowerPoint containing 10 slides, each of which randomly had 5 numbers, was used to measure dynamic vision (the size of all numbers was 12 to 20 at the center of the page). Each page had 5 numbers with the same font and each person evaluated 10 pages. The person sat down on the chair and was placed centimeters at a distance of 70 cm of the paper at same level with the eye. The person was asked to rotate the neck with a frequency of 2 Hz to see the numbers (the pain in the rotation of the neck was 70 degrees with a frequency of 2 Hz). Also, the person was asked to maintain approximately the frequency of 2 Hz during testing using the metronome and verbal feedback. The dynamic vision score of the person was calculated based on the number of correct answers. The person had 5 seconds to answer the questions on each page during the rotation of the neck. Before doing the test, it was confirmed that all the individuals were able to read the smallest font size 12 at a distance of 70 cm without moving head [16].