The Dynamics of the Development of Apneic Breathing Capacity Specific to Synchronized Swimming in Girls Aged 7–14 Years

: The purpose of the study was to identify the durations of maintaining apnea, in different static positions, with and without the use of a nose clip, in girls aged between 7 and 14 years,. The study included a total number of 92 girls, grouped by age into four groups of 2-year spans (7–8, 9–10, 11–12, 13–14 years), and depending on the experience of practicing synchronized swimming (6–42 months). In the study we applied five physical tests where apnea maintenance times were recorded in different static positions: Apnea Test of Facial floatation with and without nose clip, Apnea Test of Front tuck with and without nose clip and Apnea Test of Front layout with support to scull. The statistical analysis was performed with SPSS-24. During the study, a program of specific exercises to learn/consolidate the apneic breathing specific to artistic swimming was implemented, for a time interval of 3 months. The results were recorded at the beginning of the study (TI) and at the end of the study (TF). Analyzing the results of the study, we found positive and statistically significant improvements, related to age and experience. The most significant progress, taking into account the averages between the final and initial tests, was recorded in relation to Facial Flotation for 1.301 s for the 7–8-year-old group and 1.110 s for the 9–10-year-old group; the 11–12-year-old group recorded the most positive effect in the Facial Flotation test with a nose clip, with a result of 0.853 s, and in the 13–14-year-old group in the front tuck with nose clip test, a result of 0.807 s was reached. In all tests of the study, the Cohen’s values in all groups fell between 0.184 and 0.478, the size of the effect being small and medium. The ANOVA analysis of variance showed that the differences were statistically significant for p < 0.05 between the arithmetic means of the four groups according to age and sport experiences. For all groups, the value of Wilks’ Lambda was 0.009 ( p < 0.01) for age and 0 ( p < 0.01) for sports experience, highlighting large differences between groups. We conclude that the development of the ability to maintain apnea specific to synchronized swimming shows an upward trajectory, being conditioned by the training methodology, the age of the subjects and the sports experience. The small and medium values of the effect size highlight the fact that the improvement in apnea maintenance time is dependent on the duration and frequency of the apnea exercises performed in technical conditions specific to synchronized swimming. The training methodology must be adapted to the particularities of age, sports experience and the characteristics of synchronized swimming.


Introduction
Synchronized swimming involves the performance of some imposed figures, linked together by choreography movements, with a high level of technicality, precision and sometimes speed, performed above the surface of the water or in total or partial immersion.In synchronized swimming, the method of performing the elements in the warm-up part or the effective programs involves periods of alternating air (aerobic) breathing with underwater (apneic) breathing.The novelty of our study consists in the comparison of apnea maintenance times in different static positions performed in the water for synchronized swimming practitioners with and without the use of a nose clip in girls aged between 7 and 14 years and in relation to the sports training time interval.
The selection of synchronized swimmers for participation in specific competitions is related to the level of motor, technical and functional potential shown by the athletes [1,2].A series of previous studies have identified the fact that the results obtained in competitions are primarily influenced by functional skills, and secondarily by motor skills [3,4].The main specific functional adaptations affect vital and cardiac capacities, and to a lesser extent those of metabolism [4,5].The functional adaptations in synchronized swimming are related to the physical properties of the aquatic environment: viscosity, the hydrostatic pressure and surface tension [6,7].The transition from one initial position to another, in the chaining of figures specific to synchronized swimming, is achieved through transitional positions, involving functional mechanisms for the rapid adaptation of breathing [8,9].Precise synchronized movements and high-risk acrobatic maneuvers are mainly performed in immersion, requiring aerobic and anaerobic capacity [10,11].
The performance of the elements and their chaining in team programs requires the changing of the places and positions of the athletes during apneic time intervals, and due to the depth and duration of the immersion, respiratory effort is more difficult compared to the facial immersion [12,13].Currently, the trainers design the choreography of the programs by increasing the frequency of specific movements, which employ shorter apneic durations.An important factor in apneic breathing is the inverted vertical position, with the head down, which requires a considerable respiratory effort compared to that achieved in a horizontal position, with the face immersed in water, [12,14].In this way, the researchers monitored apnea times in routine competitions, finding a weight between 50% [15] and 66.7 ˘6.1%, mostly in seniors [16,17].A reference study has been undertaken on performance-level athletes, taking into account the time spent in apnea during international competitions, depending on the schedule, and the following weights were recorded: solo (62.2%), duets (56.1%), teams (51.2%) [15].Looking at the times of maintaining apnea, another study concluded that in free programs for seniors, the time of maintaining apnea is on average 43 s [13].According to specialists, the ability to maintain apnea for beginners should be over 25.5 ˘6.2 s [18].Taking into account the previous studies presented, the practice of synchronized swimming requires prolonged and repeated apnea exposures that improve the development of anaerobic capacity more than other water sports.A previous study carried out an assessment of the position of the body in the water during team programs for seniors, concluding that the horizontal position is weighted by 33.1% approximately 40% of the time and 72.4% at 60% vertically, this latter mainly occurring in conditions of apnea [19][20][21].
Based on the previously detailed arguments, we believe that the study will contribute to our understanding of the impact of the implementation of a specialized synchronized swimming program on improving apneic capacity.We have not identified any studies that address how the apneic capacity can be developed through specific exercises depending on age and sports experience in synchronized swimming.We also want to assess whether the apneic breathing capacity correlates with the chronological age of the subjects and with the sports experience in synchronized swimming.
The main aim of the study was to identify the impact of the implementation of an experimental program of synchronized swimming on the times of maintaining apnea, in different static positions, with and without the use of a nose clip, in girls (age 7-14), divided into four groups according to age and sports experience.The secondary goal was to identify the correlations between age and sports experience in relation to maintaining apnea specific to swimming in the subjects of the study.
H1-The hypothesis of the study is based on the assumption that the implementation of a specific synchronized swimming program will contribute to the improvement of the apnea maintenance time of athletes (girls aged 7-14 years).

Experimental Design
To measure the anthropometric parameters in this interventional study, the following devices were used: the digital talliometer Seca for height investigation (cm); the Tanita body scale (digital) for assessing weight (kg); metal anthropometric tape for assessing arm span (cm).The test conditions were identical for all subjects and for all tests [22].
Periodization of the study: All the tests were carried out in a swimming pool, with a depth ranging from 1.50 to 2 m, at a water temperature of 28-29 degrees Celsius, after a 10-min preliminary warm-up on the ground, including basic gymnastics and specific swimming exercises, followed by an adaptation to the aquatic environment for 20 min, which included specific swimming and synchronized swimming exercises, performed with high amplitude and low intensity.
During the study, the technical and physical training specific to synchronized swimming consisted of two training sessions carried out in the aquatic environment and one training session in the gym, for all groups of girls.During the training sessions performed in the swimming pool, to the time spent in the water (according to Table 2), a warm-up on the ground was added to sum an average of 10-20 min, depending on the objectives of the training lesson.

Back Layout Position
During the study, the technical and physical training specific to synchronized swimming consisted of two training sessions carried out in the aquatic environment and one training session in the gym, for all groups of girls.During the training sessions performed in the swimming pool, to the time spent in the water (according to Table 2), a warm-up on the ground was added to sum an average of 10-20 min, depending on the objectives of the training lesson.training session in the gym, for all groups of girls.During the training sessions performed in the swimming pool, to the time spent in the water (according to Table 2), a warm-up on the ground was added to sum an average of 10-20 min, depending on the objectives of the training lesson.The specific exercises for improving the anaerobic respiratory capacity were performed during the training with varying weights depending on the targeted objectives.The exercises specific to the teaching program were selected from swimming procedures and synchronized swimming, including free exercises or using auxiliary materials; they were performed while moving and by maintaining a static position with the face and certain body segments immersed.In each training lesson, exercises were performed, with reference to the results of the initial testing by age category.The following describes how it was practiced: 2ˆthe initial average apnea time/age category/testing position with and without a nose clip, with a break of 1-2 min after each execution in which normal breathing was performed.

Position Name Figures Description Body Segments
The following is an example of an exercise program for the 7-8-year-old category: In the event that an athlete fails to maintain the mentioned time, work is done in relation to the maximum individual time of maintaining apnea, and later the exercises are performed in the same logical structure during the 3 months of preparation for the study.

Physical Tests of Study
The tests were carried out after a specific warm-up, and the time between individual tests was 10-15 min, this time interval being that during which the subjects performed relaxation movements, which involve normal aerobic breathing.In the present research, we applied 5 physical tests aimed at recording the apnea maintenance times in different static positions: For a better visualization of the positions, we will present images of the positions employed in the study (Figures 1-3).
Appl.Sci.2024, 14, x FOR PEER REVIEW 6  For all these tests, the time achieved individually while maintaining the correct body position was timed in seconds.We wanted to carry out these tests with the accessory (nose clip) and without it, because during the training period the subjects said that they felt more comfortable when they did not use the nose clip.We selected these three tests following discussions with synchronized swimming specialists who considered that for the levels of technical preparation of initiation and consolidation, these positions are the most applied and practiced in order to improve apneic breathing, because they are the basis of the initial position for most of the specific figures.For all these tests, the time achieved individually while maintaining the correct b position was timed in seconds.We wanted to carry out these tests with the accessory ( clip) and without it, because during the training period the subjects said that they more comfortable when they did not use the nose clip.We selected these three following discussions with synchronized swimming specialists who considered tha the levels of technical preparation of initiation and consolidation, these positions ar most applied and practiced in order to improve apneic breathing, because they are basis of the initial position for most of the specific figures.

Typology of Breathing in the Basic Figures Specific to Synchronized Swimming
According to the Artistic Swimming Figures Manual 2022-2025, edited by W Aquatic [23], of the 14 basic positions, 6 are horizontal and 8 are vertical.In ver positions, the body is perpendicular to the surface of the water, the head is down, breathing is apneic.The basic horizontal positions involve an alternation of breath from normal to apneic.To highlight the types of breathing involved in the basic horizo and vertical positions, we designed a table in which we describe the names of positions, giving an illustration of the figure, a description and the type of breat (Tables 2 and 3).The images were taken from the website of the synchronized swimm federation [23].For all these tests, the time achieved individually while maintaining the correct b position was timed in seconds.We wanted to carry out these tests with the accessory ( clip) and without it, because during the training period the subjects said that they more comfortable when they did not use the nose clip.We selected these three following discussions with synchronized swimming specialists who considered tha the levels of technical preparation of initiation and consolidation, these positions ar most applied and practiced in order to improve apneic breathing, because they ar basis of the initial position for most of the specific figures.

Typology of Breathing in the Basic Figures Specific to Synchronized Swimming
According to the Artistic Swimming Figures Manual 2022-2025, edited by W Aquatic [23], of the 14 basic positions, 6 are horizontal and 8 are vertical.In ver positions, the body is perpendicular to the surface of the water, the head is down, breathing is apneic.The basic horizontal positions involve an alternation of breath from normal to apneic.To highlight the types of breathing involved in the basic horizo and vertical positions, we designed a table in which we describe the names of positions, giving an illustration of the figure, a description and the type of breat (Tables 2 and 3).The images were taken from the website of the synchronized swimm federation [23].In vertical positions, the body is perpendicular to the surface of the water, the head is down, and breathing is apneic.The basic horizontal positions involve an alternation of breathing, from normal to apneic.To highlight the types of breathing involved in the basic horizontal and vertical positions, we designed a table in which we describe the names of the positions, giving an illustration of the figure, a description and the type of breathing (Tables 2 and 3).The images were taken from the website of the synchronized swimming federation [23].

Statistical Analysis
SPSS Statistics 24.0 software was used for the calculation of the parameters: arithmetic mean (X), standard deviation (SD), minimum (Min), maximum (Max), effect size, and Confidence Interval for the mean (CI-95%) with the lower and upper benchmarks.We calculated the Pearson correlations between age, sport performance and the results of the tests in the study.Cohen's effect sizes can be interpreted as <0.20 small, >0.50 medium, and >0.80 large effect size.Multifactor analysis (ANOVA) was performed using the F test and Multiple Comparisons (Turkey HSD).Wilks's lambda involves a multivariate analysis of variance (MANOVA) statistical parameters to reveal whether there are differences between the means of groups of subjects depending on a combination of dependent variables.A good Wilks' lambda value is close to 0. The statistical significance level for this study was p < 0.05.

Results
The evolution of the ability to maintain apnea, for all four groups of subjects, showed a positive dynamic in all five tests applied, with the execution variants.We will present descriptive results regarding the ability to maintain apnea in Table 3, for all age categories and applied tests.
After the data analysis, according to Table 4, it was found that the differences in the arithmetic averages between the tests fell within the confidence interval of 95% CI lower and upper for all evaluated parameters.The differences in arithmetic averages between the tests are statistically significant, for all parameters, at a reference threshold of p < 0.005.After analyzing the results, it has been found that the best result between the tests was derived in the facial floatation test for the 7-8-year-old group, with the arithmetic mean differences between the tests being 1.301 s, and for the 9-10-year-old group the result was 1.110 s.For the 11-12-year-old group, the best result of 0.853 s was recorded in the facial floatation with nose clip test, and in the 13-14-year-old group, the best result was 0.807 s in the front tuck with nose clip test (Table 4).After analyzing the results recorded with the Cohen's parameter, for all five motor tests, we have found that the values fell between 0.184 and 0.478, the size of the affect being between small and medium for all study groups (Tabel 4).For the E1 group (7-8 years), the Cohen's values were >0.3 for facial floatation, facial floatation with nose clip and front tuck, showing an average effect size; for front tuck with nose clip and front layout with scull support, the effect size was small <0.3.Analyzing the results of E2-group 9-10 years, we find that Cohen's values fell between 0.184 and 0.478, where it was >0.3 for facial floatation, facial floatation with nose clip and front tuck, the size of the effect being average.For front tuck with nose clip and front layout with scull support, the effect size was small, at <0.3. in the E3 group (11-12 years), the Cohen's values fell between 0.222 and 0.379, with >0.3 for facial floatation and front tuck, showing a medium effect size; for facial floatation with nose clip, front tuck with nose clip and front layout with scull support, the effect size was small, at <0.3.Analyzing the results of the E4 group (13-14 years), we found Cohen's values that fell between 0.200 and 0.403, with >0.3only for facial floatation, and for the other tests the value was <0.3, the size of the effect being small.The small and medium values of the effect size highlight the fact that the improvement in apnea maintenance time is dependent on the duration and frequency of the apnea exercises in technical conditions specific to synchronized swimming.
The application of the ANOVA analysis of variance (Table 5) allowed us to identify that the differences were statistically significant for p < 0.05 between the arithmetic means of the 4 groups of subjects, structured according to age and sport experiences, in all evaluation tests of the apnea maintenance times specific to synchronized swimming.Statistically significant differences were recorded both for the initial and final tests, for all the tests of the study.
By making multiple comparisons (Table 6) between the groups of subjects for each test and sample applied, it was found that between the 7-8-year-old group and the 9-10-year-old group, the results were not statistically significant (p > 0.005).The com-parisons between the other groups according to the age category were statistically significant.The differences of the arithmetic averages between tests for all tests and groups fell within the confidence interval (95% CI lower and upper) for all evaluated parameters.The biggest differences between the groups of 7-8 years and 9-10 years were recorded in the tests of facial floatation with nose clip-TI ´1.878 s and facial floatation without nose clip-TF ´1.751 s. Between the group of 9-10 years and 11-12 years, the biggest differences recorded in TI were in facial floatation-6.823s, and for TF in facial floatation with nose clip-6.520s. Between the 11-12-year-old and 13-14-year-old groups, the biggest differences recorded at TI were seen in front tuck without nose clip-17.314s and TF during front tuck with nose clip-TF ´17.614 s.According to Table 7, for the E1 group (7-8 years), chronological age correlates with the results of all motor tests, where p < 0.05, but sports experience does not influence the ability to maintain apnea.Analyzing the Pearson values for the age groups 9-10, 11-12 and 13-14 included in the study, we found that age does not influence the level of apnea maintenance specific to synchronized swimming.In contrast, sports experience correlates positively with the apneic capacity; the influence of sports experience on apneic capacity was statistically significant for all the tests of the study, p < 0.05.These results reflect the fact that in the initial stage, age has a major influence, but later through the continuation of training and the accumulation of sports experience, it acquires an essential role in relation to the apneic capacity.The multivariate analyses presented in Table 8 for age show that the Wilks' Lambda values were between 0.001 and 0.071, with p < 0.05, showing that the results of the implementation of the experimental training program were statistically significant for all groups (E1, E2, E3, E4).If we analyze the sports experience in relation to the results of the test groups of the study, we find that the values of Wilks' Lambda were statistically significant for p < 0.05.Referring to the sports experience, the values of Wilks' Lambda were 0 for the E2 group 9-10 years, E3 group 11-12 years and E4 group 13-14 years, and the Wilks' Lambda value for the E1 group 7-8 years was 0.034.Regarding age, the values of Wilks' Lambda were 0.071 for the E1 group 7-8 years, 0.001 for the E2 group 9-10 years, 0.008 for the E3 group 11-12 years and 0.021 for the E4 group 13-14 years.The low values of Wilks' Lambda show that the experimental program implemented in the study was effective, determining the optimization of apneic capacity in all four experimental groups.For all groups, the value of Wilks' Lambda was 0.009 (p < 0.01) for age, while it was 0 (p < 0.01) for sports experience, highlighting large differences between groups after the implementation of the experimental program.

Discussion
The main aim of the study was to identify the impact of the implementation of an experimental program of synchronized swimming on the times of maintaining apnea in different static positions with and without the use of a nose clip, in girls (age 7-14), divided into four groups according to age category and sports experience.The secondary goal was to identify the correlations between age and sports experience.The results of the study facilitate the expansion of the level of knowledge regarding the level of sports performance and especially the possibilities of developing the functional respiratory capacity in children practicing synchronized swimming.This assessment of the evolution of the ability to maintain breathing in the aquatic environment, assessed by age categories combined with the time interval of practicing synchronized swimming, contributes to the knowledge of the respiratory possibilities of children between 7 and 14 years old, which will offer specialists scientific guidance in the methodical approach to specific training in apneic exercise conditions.Analyzing the results, we find that for only the 7-8-year-old group, apnea maintenance performance is influenced by chronological age, but not by sports experience.In the groups of 9-10, 11-12 and 13-14 years, the apnea capacity correlates statistically significantly with sports experience, but not with chronological age.These results show that age matters only in the initiation stage (7-8 years of age), and subsequently the training methodology and the expansion of the sports experience have an essential and major influence on apnea capacity.
Following the application of the exercise program specific to apneic breathing, it was found that in all four groups of subjects and for all tests applied, between the initial and final testing, statistically significant progress was registered.These results align with previous studies that concluded that aquatic anaerobic capacity improves through prolonged and repeated apnea exposures, more evidently than in other aquatic sports [24,25].
In a study, it was highlighted that in preadolescents (10-14 years old), when performing aerobic training, there are no adaptive changes in VO2 max compared to the training stimuli, implying that this improves the size of the heart, and anaerobic capacity develops through anaerobic training [26].In accordance with the previously mentioned study, the results recorded in the present study show changes in the ability to maintain apnea, which increased on average by 0.6-1.2s in the category of 9-14 years.In agreement with our study, another study concluded that long-term apneic breathing training can yield positive results by increasing tolerance to hypoxia [27].
After performing an analysis of the current study between the minimum average time achieved and the maximum average time recorded by age category, we derived the following values: in the 7-8-year-old group, the minimum starting time was 9.320 s and the maximum was 11.702 in free apnea tests without a nose clip; for those with nose clips the minimum was 9.338 s and the maximum was 12.623; in the category of 9-10 years, in the tests without nose clip, the minimum was10.330s and the maximum was 12.777 s, and in the tests with the nose clip accessory, the minimum was11.206s and the maximum was 12.195 s.In the 11-12 year group without the accessory, the minimum was 15.958 s recorded at the initial test and the maximum was 17.800 s recorded at the final test, and in the tests with the nose clip, the minimum was 16.684 s and the maximum was 18.619 s.In the 13-14-year-old group, in the initial tests without the accessory, a minimum of 27.953 was recorded and a maximum of 32.352 s was found; in the tests with a nose clip, a minimum of 31.035s and a maximum of 33.908 s were found in the final test.Taking as a benchmark the statistical significance of the arithmetic averages from the tests, in the 7-8-year-old and 9-10-year-old groups, no statistically significant results were recorded, and the recorded results are in agreement with the level of development of the subjects by age category.Referring to the highlighted results, the recommendation given to synchronized swimming specialists regarding the average time to maintain the apnea for beginners should be 25.5 ˘6.2 s [18].The recorded results offer benchmarks of functional respiratory capacity related to synchronized swimming practice time intervals.
In order to explain the differences recorded in the present study, we should consider how, in the 7-10-year-old group, in accordance with the particularities of anatomicalfunctional development, a series of changes in respiratory capacity occur: the differentiation of lung sizes ends at the age of 7, and their growth continues; one moves from predominantly abdominal to thoracic breathing.The breathing rate decreases from 20-22 at the age of 7 years to 18-20 at the age of 10 years, and it becomes more rhythmic and deeper [28][29][30].Also, gradual increases were identified in the respiratory minute volume and the vital capacity of the lungs, which constitute 1800-2000 cm3 at 10 years.The vital capacity increases almost parallel to the anatomical capacity of the lungs, making an important leap between 6 and 8 years [31,32].
In the age category 11-14 years, the possibilities of respiratory capacity are as follows: the amplitude of respiratory movements increases on average from 230 mL of air current volume at the age of 11 years up to 300 mL of air at the age of 13 years and up to 350 mL of air at age 15 [33]; the respiratory rate decreases from 22 breaths/min at the age of 11 years to 20 breaths/min at the age of 13 years, and to 18 breaths/min at the age of 15 years; the vital capacity at 11 years is between 2000 and 2200 mL of air, a value that increases on average by 250 mL of air for girls, which occurs at the age of 14-15 years [34].In the first stage of puberty (10-13 years), the annual increase in vital capacity is up to 250 mL of air for girls and up to 300 mL of air for boys.In the second stage of puberty, the vital capacity develops rapidly, and the annual increase of this parameter reaches values of 3500 mL of air [25,35,36].Starting from these physiological benchmarks, it is considered that physical exercises aimed at holding the breath in water (apnea) performed in synchronized swimming can induce physiological adaptations as responses to the immersion of the body in water [20].Most of the studies looking at time spent above and below water during free exercise and apnea holding times were conducted on seniors, where they were found to range between 33 and 66 s, with an average of 43 s [13,19].Research in the lab has shown that, during a national competition, athletes dipped their face an average of 18 times, with an average apnea time of about 7 s, but the longest apnea period lasted ~39 s [18].In order to expand the potential of functional capacity and adaptation to various environments, sports-specific hypoxia training is applied, carried out in areas at high altitudes (natural or artificial) and at low altitudes, at sea level, and in aquatic environments [37].
In a number of studies, the use of training involving hypoxia with intervals proved that 12-14-year-old swimmers undergo development in their main motor qualities, such as execution speed, strength and general endurance [38][39][40][41].Through the specifics of the positions adopted making the figures-vertically or horizontally-it was identified that 43% of the total time of the routine is spent vertically with the head down, with an average duration of apnea of 21 s [42].Specialists consider that the use of apneic breathing exercises in training requires in-depth knowledge about functional mechanisms and adaptations to them [43,44].In the long term, training that applies apnea exercises improves the duration of maintenance, but also increases the tolerance to hypoxia [27].The approach to sports training must be made in an interdisciplinary way so as to identify how different specific factors contribute to improving sports performance [45][46][47].
The strengths of the study are that the ages of the subjects ranged from 7 to 14 years; the relatively large number of female subjects included in the study; the correlation of age with the duration of practicing synchronized swimming; performing tests while immersed in water; the number of tests performed with and without accessories; the test positions that correspond to the most practiced horizontal positions of the basic figures specific to synchronized swimming; the complexity of the specific evaluation tests; the analysis of four age samples divided into groups of two-year periods, ranging 7-14 years; the mode of evaluation of the impact of specific synchronized swimming training.

Limitations of Study
The present study has the following limitations: the study did not take into account athletes from other categories over 14 years old; male subjects were not included in the study; our study could not be compared with previous studies because their number is extremely limited, and most of the tests were performed in laboratory conditions; the relatively small number of subjects included in the study, due to the small number of junior synchronized swimming practitioners in Romania; the duration of the experimental program was only 3 months and the subsequent development of the subjects was not followed; functional parameters (heart rate, number of breaths) were not monitored; the factors of the aquatic environment (water temperature) and the conditions of exercise and sports training (pool areas) were not monitored.

Practical Implications and Future Research Directions
Based on the results of the study, we consider that training methodologies should include specific exercises to improve the ability to maintain apnea from the beginner level in synchronized swimming.Trainers should constantly monitor the time of maintaining apnea in immersion conditions in order to identify the possibilities of adopting the figures and positions that involve prolonged apnea.We consider that the results of our study represent dynamic benchmarks of the development of the ability to maintain breathing according to age categories and sports experience in synchronized swimming.Future research could focus on the monitoring of functional parameters when adopting figures and undertaking synchronized swimming programs under conditions of training and sports competition, identifying the influence of water characteristics on the ability to maintain apnea in synchronized swimming, and extending our research to other age categories and sports experience, as well as to male and mixed synchronized swimming.Future research will be able to focus on identifying ways to improve the apnea time in different positions or figures specific to synchronized swimming, and identifying the factors that can facilitate improvements in the motor and functional capacity of synchronized swimming athletes.

Conclusions
Analyzing the results, it was found that the development of the ability to maintain apnea specific to synchronized swimming shows an upward trajectory, being conditioned by the specific methodology applied, the age of the practitioners and the time interval of practicing synchronized swimming, with implications for the execution technique.The most significant progress between the final and initial tests was recorded in the facial flotation test, at 1.301 s for the 7-8-year-old group and 1.110 s for the 9-10-year-old group; the 11-12-year-old group showed the most positive effect in the facial flotation test with a nose clip, 0.853 s, and in the 13-14-year-old group, in the front tuck with nose clip test, the result was 0.807 s.The progress recorded between the age groups was statistically significant in all the motor tests, except for the 7-8-year-old group and the 9-10-yearold group.The small and medium values of the effect size highlight the fact that the improvement of apnea maintenance time is dependent on the duration and frequency of the apnea exercises under technical conditions specific to synchronized swimming.In this study, we found that age influences apnea capacity only at the age of 7-8 years old, and subsequently the training methodology and the expansion of sports experience have an essential and major influence on the improvement of apnea capacity.The results of the present study have practical and scientific implications regarding knowledge, and the optimization and dosing, of sports training methodologies.

‚ 28 -
31 March 2023-performing initial testing on all four subject groups; ‚ 4 April-10 July 2023-implementing the training program; ‚ 12-15 July 2023-conducting the final testing for all subject groups.

Front
, trunk and leg horizontally parallel to the surface of the water.Face at the surface of the water.b.The body immersed under water, one leg perpendicular to the surface with the water level between the knee and the ankle.a. normal breathing b. apneic breathing extended with head, upper back, buttocks and heels at the surface of the water.The face submerged in water b.Idem, head and face above the surface of the water a. apneic breathing b. normal breathing Flamingo Position a b a.The trunk, head, tibia and foot of the leg bent parallel to the surface of the water.Face at the surface of the water.b.The body submerged, water level between knee and ankle of extended leg.a. normal breathing b. apneic breathing Ballet Leg Double Position a b a. Trunk and head parallel to the surface of the water.Face at the surface of the water.b.Submerged body, water level between knees and ankles of extended legs.a. normal breathing b. apneic breathing Tuck Position a b a. Calves, chest and head parallel to the surface of the water, facing the surface of the water b.With the exception of the foot, the whole body is submerged under water a. normal breathing b. apneic breathing Tub Position Feet bent close together, thighs perpendicular to the water, shins parallel to the surface of the water.Face at the surface of the water normal breathin 2.3.Periodization of Training The periodization of training by age category is as follows:  E1-3 training sessions, 2 of which were in the swimming pool, each lasting 60 min;  E2-3 training sessions of which 1 training session was on the ground, with a duration of 60 min, and 2 were in the swimming pool with a duration of 90 min;  E3 and E4-3 training sessions, of which 1 was on the ground with a duration of 90 min, and 2 were in the swimming pool, with a duration of 90 min.a. Head, trunk and leg horizontally parallel to the surface of the water.Face at the surface of the water.b.The body immersed under water, one leg perpendicular to the surface with the water level between the knee and the ankle.a. normal breathing b. apneic breathing Front Layout Position ming consisted of two training sessions carried out in the aquatic environment and one training session in the gym, for all groups of girls.During the training sessions performed in the swimming pool, to the time spent in the water (according to Table 2), a warm-up on the ground was added to sum an average of 10-20 min, depending on the objectives of the training lesson.
, trunk and leg horizontally parallel to the surface of the water.Face at the surface of the water.b.The body immersed under water, one leg perpendicular to the surface with the water level between the knee and the ankle.extended with head, upper back, buttocks and heels at the surface of the water.The face submerged in water b.Idem, head and face above the surface of the water a. apneic breathing b. normal breathing Flamingo Position a b a.The trunk, head, tibia and foot of the leg bent parallel to the surface of the water.Face at the surface of the water.b.The body submerged, water level between knee and ankle of extended leg.a. normal breathing b. apneic breathing Ballet Leg Double Position a b a. Trunk and head parallel to the surface of the water.Face at the surface of the water.b.Submerged body, water level between knees and ankles of extended legs., chest and head parallel to the surface of the water, facing the surface of the water b.With the exception of the foot, the whole body is submerged under water a. normal breathing b. apneic breathing Tub Position Feet bent close together, thighs perpendicular to the water, shins parallel to the surface of the water.Face at the surface of the water normal breathin 2.3.Periodization of Training The periodization of training by age category is as follows:  E1-3 training sessions, 2 of which were in the swimming pool, each lasting 60 min;  E2-3 training sessions of which 1 training session was on the ground, with a duration of 60 min, and 2 were in the swimming pool with a duration of 90 min;  E3 and E4-3 training sessions, of which 1 was on the ground with a duration of 90 min, and 2 were in the swimming pool, with a duration of 90 min.a. Body extended with head, upper back, buttocks and heels at the surface of the water.The face submerged in water b.Idem, head and face above the surface of the water a. apneic breathing b. normal breathing Flamingo Position , trunk and leg horizontally parallel to the surface of the water.Face at the surface of the water.b.The body immersed under water, one leg perpendicular to the surface with the water level between the knee and the ankle.extended with head, upper back, buttocks and heels at the surface of the water.The face submerged in water b.Idem, head and face above the surface of the water a. apneic breathing b. normal breathing Flamingo Position a b a.The trunk, head, tibia and foot of the leg bent parallel to the surface of the water.Face at the surface of the water.b.The body submerged, water level between knee and ankle of extended leg.a. normal breathing b. apneic breathing Ballet Leg Double Position a b a. Trunk and head parallel to the surface of the water.Face at the surface of the water.b.Submerged body, water level between knees and ankles of extended legs., chest and head parallel to the surface of the water, facing the surface of the water b.With the exception of the foot, the whole body is submerged under water a. normal breathing b. apneic breathing Tub Position Feet bent close together, thighs perpendicular to the water, shins parallel to the surface of the water.Face at the surface of the water normal breathin 2.3.Periodization of Training The periodization of training by age category is as follows:  E1-3 training sessions, 2 of which were in the swimming pool, each lasting 60 min;  E2-3 training sessions of which 1 training session was on the ground, with a duration of 60 min, and 2 were in the swimming pool with a duration of 90 min;  E3 and E4-3 training sessions, of which 1 was on the ground with a duration of 90 min, and 2 were in the swimming pool, with a duration of 90 min.a.The trunk, head, tibia and foot of the leg bent parallel to the surface of the water.Face at the surface of the water.b.The body submerged, water level between knee and ankle of extended leg.a. normal breathing b. apneic breathing Ballet Leg Double Position training session in the gym, for all groups of girls.During the training sessions performed in the swimming pool, to the time spent in the water (according to Table 2), a warm-up on the ground was added to sum an average of 10-20 min, depending on the objectives of the training lesson.

Front
, trunk and leg horizontally parallel to the surface of the water.Face at the surface of the water.b.The body immersed under water, one leg perpendicular to the surface with the water level between the knee and the ankle.a. normal breathing b. apneic breathing extended with head, upper back, buttocks and heels at the surface of the water.The face submerged in water b.Idem, head and face above the surface of the water a. apneic breathing b. normal breathing Flamingo Position a b a.The trunk, head, tibia and foot of the leg bent parallel to the surface of the water.Face at the surface of the water.b.The body submerged, water level between knee and ankle of extended leg.a. normal breathing b. apneic breathing Ballet Leg Double Position a b a. Trunk and head parallel to the surface of the water.Face at the surface of the water.b.Submerged body, water level between knees and ankles of extended legs.a. normal breathing b. apneic breathing Tuck Position a b a. Calves, chest and head parallel to the surface of the water, facing the surface of the water b.With the exception of the foot, the whole body is submerged under water a. normal breathing b. apneic breathing Tub Position Feet bent close together, thighs perpendicular to the water, shins parallel to the surface of the water.Face at the surface of the water normal breathin 2.3.Periodization of Training The periodization of training by age category is as follows:  E1-3 training sessions, 2 of which were in the swimming pool, each lasting 60 min;  E2-3 training sessions of which 1 training session was on the ground, with a duration of 60 min, and 2 were in the swimming pool with a duration of 90 min;  E3 and E4-3 training sessions, of which 1 was on the ground with a duration of 90 min, and 2 were in the swimming pool, with a duration of 90 min.a. Trunk and head parallel to the surface of the water.Face at the surface of the water.b.Submerged body, water level between knees and ankles of extended legs.a. normal breathing b. apneic breathing Tuck Position training session in the gym, for all groups of girls.During the training sessions performed in the swimming pool, to the time spent in the water (according to Table 2), a warm-up on the ground was added to sum an average of 10-20 min, depending on the objectives of the training lesson.

Front
, trunk and leg horizontally parallel to the surface of the water.Face at the surface of the water.b.The body immersed under water, one leg perpendicular to the surface with the water level between the knee and the ankle.a. normal breathing b. apneic breathing extended with head, upper back, buttocks and heels at the surface of the water.The face submerged in water b.Idem, head and face above the surface of the water a. apneic breathing b. normal breathing Flamingo Position a b a.The trunk, head, tibia and foot of the leg bent parallel to the surface of the water.Face at the surface of the water.b.The body submerged, water level between knee and ankle of extended leg.a. normal breathing b. apneic breathing Ballet Leg Double Position a b a. Trunk and head parallel to the surface of the water.Face at the surface of the water.b.Submerged body, water level between knees and ankles of extended legs.a. normal breathing b. apneic breathing Tuck Position a b a. Calves, chest and head parallel to the surface of the water, facing the surface of the water b.With the exception of the foot, the whole body is submerged under water a. normal breathing b. apneic breathing Tub Position Feet bent close together, thighs perpendicular to the water, shins parallel to the surface of the water.Face at the surface of the water normal breathin 2.3.Periodization of Training The periodization of training by age category is as follows:  E1-3 training sessions, 2 of which were in the swimming pool, each lasting 60 min;  E2-3 training sessions of which 1 training session was on the ground, with a duration of 60 min, and 2 were in the swimming pool with a duration of 90 min;  E3 and E4-3 training sessions, of which 1 was on the ground with a duration of 90 min, and 2 were in the swimming pool, with a duration of 90 min.a. Calves, chest and head parallel to the surface of the water, facing the surface of the water b.With the exception of the foot, the whole body is submerged under water a. normal breathing b. apneic breathing Tub Position training session in the gym, for all groups of girls.During the training sessions performed in the swimming pool, to the time spent in the water (according to Table 2), a warm-up on the ground was added to sum an average of 10-20 min, depending on the objectives of the training lesson.
, trunk and leg horizontally parallel to the surface of the water.Face at the surface of the water.b.The body immersed under water, one leg perpendicular to the surface with the water level between the knee and the ankle.a. normal breathing b. apneic breathing Front Layout Position a b a. Body extended with head, upper back, buttocks and heels at the surface of the water.The face submerged in water b.Idem, head and face above the surface of the water a. apneic breathing b. normal breathing Flamingo Position a b a.The trunk, head, tibia and foot of the leg bent parallel to the surface of the water.Face at the surface of the water.b.The body submerged, water level between knee and ankle of extended leg.a. normal breathing b. apneic breathing Ballet Leg Double Position a b a. Trunk and head parallel to the surface of the water.Face at the surface of the water.b.Submerged body, water level between knees and ankles of extended legs.a. normal breathing b. apneic breathing Tuck Position a b a. Calves, chest and head parallel to the surface of the water, facing the surface of the water b.With the exception of the foot, the whole body is submerged under water a. normal breathing b. apneic breathing Tub Position Feet bent close together, thighs perpendicular to the water, shins parallel to the surface of the water.Face at the surface of the water normal breathin 2.3.Periodization of Training The periodization of training by age category is as follows:  E1-3 training sessions, 2 of which were in the swimming pool, each lasting 60 min;  E2-3 training sessions of which 1 training session was on the ground, with a duration of 60 min, and 2 were in the swimming pool with a duration of 90 min;  E3 and E4-3 training sessions, of which 1 was on the ground with a duration of 90 min, and 2 were in the swimming pool, with a duration of 90 min.Feet bent close together, thighs perpendicular to the water, shins parallel to the surface of the water.Face at the surface of the water normal breathin 2.3.Periodization of Training The periodization of training by age category is as follows: ‚ E1-3 training sessions, 2 of which were in the swimming pool, each lasting 60 min; ‚ E2-3 training sessions of which 1 training session was on the ground, with a duration of 60 min, and 2 were in the swimming pool with a duration of 90 min; ‚ E3 and E4-3 training sessions, of which 1 was on the ground with a duration of 90 min, and 2 were in the swimming pool, with a duration of 90 min.

‚
Apnea test of facial floatation with and without nose clip-from the free-floating position with the face immersed under the surface of the water, the arms outstretched to the sides and the legs outstretched and apart, called facial floatation; ‚ Apnea test of front tuck with and without nose clip-assuming a floating position from crouching with the face immersed on the surface of the water, the arms grab the knees, a position named "Front tuck".In these two tests, two parameters were assessed, namely, the times of maintaining apnea with the use of a nose clip and without this accessory; ‚ Apnea test of front layout with support scull-consisted of maintaining the front layout position, whereby the arms perform a movement to keep the body at the surface of the water (support scull) with the legs extended and closed, performed only with the use of a nose clip.The support scull is performed by holding the arms to the side and the forearms at 90-degree angles to the body, with the palms facing the bottom of the swimming pool.The forearms move back and forth, maintaining a right angle, and the hydrostatic pressure resulting from the movement of the hands allows the swimmer to maintain the position of the feet on the surface of the water while they are faced down.

2. 5 .
Typology of Breathing in the Basic Figures Specific to Synchronized Swimming According to the Artistic Swimming Figures Manual 2022-2025, edited by World Aquatic [23], of the 14 basic positions, 6 are horizontal and 8 are vertical.

Funding:
This research received no external funding.Institutional Review Board Statement: The present study was conducted according to the guidelines of the Declaration of Helsinki and approved by the Review Board of Physical Education and Sports, UMFST Targu Mures, Romania, no.17/22.03.2023.Informed Consent Statement: Informed consent was obtained from all subjects of the sample involved in the present study.

Table 1 .
Characteristics of the groups of study (mean ˘standard deviation).

Table 2 .
Figures and their specific respiratory typology.

Table 2 .
Figures and their specific respiratory typology.

Table 2 .
Figures and their specific respiratory typology.

Table 2 .
Figures and their specific respiratory typology.

Table 2 .
Figures and their specific respiratory typology.

Table 2 .
Figures and their specific respiratory typology.

Table 2 .
Figures and their specific respiratory typology.

Table 4 .
Descriptive statistics of the apnea tests of the study by age category.
E-experimental group; TI-initial test; TF-final test; X-mean; SD-standard deviation; ∆X-the difference of the arithmetic means; CI 95%-confidence interval of the difference; t-Student test value; p-statistical probability.

Table 5 .
ANOVA (analysis of variance) between 4 groups in the tests of the study.
TI-initial test; TF-final test;ř -sum of squares; df-degrees of freedom; MS-mean square; F-Fisher test value; p-probability level.

Table 6 .
Multiple comparisons (Turkey HSD) of the groups of the subjects and tests.

Table 6 .
Cont. ∆X-the difference of the arithmetic means; SE-Standard error; 95% CI-interval of confidence; p-statistical significance values; * Correlation is significant at the 0.05 level (2-tailed).

Table 7 .
Pearson correlation between motor test results with chronological age and sports experience.

Table 8 .
Wilks' Lambda of multivariate analysis (MANOVA) between age, experience and results of tests.
a Exact statistic, E-experimental group, F-Fisher test, p-level of probability.