Competitive swimming performance can be determined by anthropometric, biomechanical, psychological, and physiological factors (30,36,38). The swimming performance is a multi-factorial phenomenon in which each factor probably plays a major role in the performance.
Competitive swimmers are dependent on physiological adaptations to enhance their performance. The physiology of all-out performance encompasses neuromuscular processes, cardiovascular components, intramuscular energy turnover, and respiratory elements (2). Swimming practice improves pulmonary function (24) and swimmers show higher lung volumes and pulmonary diffusion capacity compared with both nonathletic and athletic peers from other sports (6,8,35). These differences may be partly because of the restricted breathing (inhalation of elevated amount of air in limited time), water pressure on the thorax, and horizontal position of swimming. The respiratory muscle training has demonstrated improvements in swimming performance (17,20) and in pulmonary function (40). Despite this, the literature about pulmonary function parameters and swimming performance is limited (16,27). These evidences show the importance of the pulmonary function in swimmers, but it is unclear what specific pulmonary function characteristics influence sprint performance and hence what should be considered for talent identification of swimmers.
Some special anthropometric characteristics such as body mass, body height, and arm span must be analyzed when swimming sprint determinants are studied (15,19,30,37). These parameters are inherent to swimmer performance and have high influence in swimmer's biomechanics and physiology. Actually, anthropometric determinants such as upper and lower extremity length characterized upper-level swimmers. In young swimmers, anthropometric factors could explain ∼46% of 100-m front-crawl variability (19). Velocity in sprint swimming performance can be compromised by total body length, lean body mass, and upper extremity length in competitive young swimmers (10,37). However, data about these relationships among anthropometry and performance in young swimmers are scarce despite being essential in swimming performance.
Regarding conditional parameters, strength of the lower extremities is considered imperative in sprint swimming performance (18,41). In fact, mean force and velocity are related well with the 4 strokes and leg explosiveness can explain most of 100-m front-crawl variability in young swimmers (10,28). Strength of the lower extremities determines starts and turns that represent an important contribution in total swimming velocity (4,41). Despite the evidence, the data are dispersed and more analysis is required in young swimmers.
There are no data available regarding the relationship between pulmonary function, conditional, and anthropometric factors together with 100-m front-crawl performance in young elite swimmers training and competing at high competitive level. In consequence, the main objective of this study was to determine the extent to which specific anthropometric, conditional, and pulmonary function variables predict 100-m front-crawl performance of national young swimmers of both genders. The secondary objective was to compare the anthropometric, conditional, and pulmonary function variables between young sprint swimmers of both genders.
Given the elevated respiratory capacity of the swimmers (6), the improvement of the swimming plus respiratory muscle training in swimming performance (17,20) and pulmonary function (40), and the importance of the proper inspiratory velocity in front-crawl stroke cycle, we hypothesized the inspiratory parameters as possible determinants of front-crawl swimming performance. Based on previous findings, we also hypothesized the differences in pulmonary function (14), conditional (5), anthropometric (body fatness) (23,42), and performance variables between young male and female sprint swimmers.
Experimental Approach to the Problem
This study used a cross-sectional research design to determine the influence of some pulmonary function, conditional, and anthropometric variables in 100-m front-crawl sprint and to compare the aforementioned variables between young sprint swimmers of both genders. Correlation and regression analysis were calculated to quantify the relationships between trial time (dependent variable) and each variable potentially predictive (independent variables). Differences between means of both gender groups were analyzed. Tests were conducted over 2 sessions 48 hours apart. On the first session, subjects were tested on anthropometric and vertical jump measurements. On the second session, subjects were tested on pulmonary function and swimming performance measurements. All tests were performed in the same order and at the same hour of day (between 9:00 and 11:00 AM) to avoid a possible circadian effect.
Seventeen national competitive swimmers with ages between 15 and 22 years volunteered to participate in our investigation, 8 male swimmers (19.4 ± 0.7 years) and 9 female swimmers (16.9 ± 3.2 years). All male swimmers were in absolute category (19 years and older) and 5 female swimmers were in absolute category (17 years and older) and 4 in junior category (15–16 years old). They were all swimmers-sprinters, and their personal records in 100-m front-crawl sprint for male and female group were 56.1 ± 1.7 seconds and 65.2 ± 4.2 seconds, respectively (80.2 and 78.5% of world record, respectively). Swimmers were recruited from the Mairena del Aljarafe swimming club of Seville (Spain). Spanish national-level swimmers who had been able to maintain their level at least for the past 3 years participated in this study. They had trained during 6 days per week during the past 3 years. Testing was conducted in the middle of the competitive season (January). All swimmers and their parents were informed of the purpose, nature, testing procedures, possible risks, and their right to terminate participation at will, before they gave their voluntary written consent to participate. Written informed consent was signed by the participants older than 18 years and by the parents of minors before participation. There was a period of at least 1 week between the day when the information was provided to the swimmers and parents and the day when their informed consent was obtained. The study was approved by the Ethics Committee of the University Pablo de Olavide (Spain) and performed according to the Declaration of Helsinki 1961 (revision of Edinburgh 2000). All participants had normal spirometry and had no history of respiratory disease. Swimmers were instructed to avoid strenuous training the day before the tests and to maintain their normal diet, hydration, and sleep routine. Moreover, subjects ate their last meal at least 2 hours before each test and were asked not to ingest any potentially ergogenic product (i.e., caffeine).
After a standard warm-up, performance level was analyzed by 100-m all-out trial in 25-m swimming pool during simulated competitions. Time in 100-m front-crawl was adopted as performance measure. Starts were made from the starting blocks with a whistle as the starting signal. Participants were asked to perform 100-m front-crawl as fast as possible and data were registered by video analysis (Panasonic SDR-H250) at a frequency of 50 Hz. The camera was placed perpendicular to the longitudinal axis of the pool to record the start and finish of swimmers. Sound was used to synchronize start signal and video camera. The software Dartfish (version 5.5; Dartfish Company, Lausanne, Switzerland) of video analysis was used to obtain total time of all-out test.
Physiological parameters of lung function were measured using portable spirometer (Microquark; Cosmed, Rome, Italy) according to American Thoracic Society recommendations (1). The pulmonary function technician and spirometer were the same throughout the study. Subjects performed 1 enforced spirometry by executing maximal inspiration followed by an enforced exhalation. This protocol was repeated 3 times (1-minute recovery between repetitions), and subjects were encouraged to continue exhaling until finishing it. Participants were asked to do both the inspiration and the expiration “explosively.” Maximum voluntary ventilation test (MVV12) was executed 2 minutes later. The data obtained by spirometry were as follows: FVC = forced vital capacity; PIF = peak inspiratory flow; FIV1 = forced inspiratory volume in the first second; FEV1 = forced expiratory volume in the first second; FEV1/FVC = relationship between forced expiratory volume in the first second and FVC; FEF25–75 = forced expiratory flow between 25 and 75% of FVC; and MVV12 (26). For each parameter, the best value was chosen from at least 3 consecutive maneuvers differing by no more than 5% (31).
Measurements of height, body mass, and skinfolds were measured at the same time of day (i.e., the morning). The swimmer presented before training in a fasted state, and all anthropometric variables were measured by a well-trained technician to avoid the interobserver coefficients of variation. Body height (to the nearest 0.1 cm) and body mass (to the nearest 0.1 kg; Seca 780; SECA Hammer Steindamm, Hamburg, Germany) were measured using standardized procedures and body mass index (BMI; in kilogram per square meter) was calculated. Subcutaneous skinfolds (triceps, biceps, subscapular, suprascapular, abdominal, right thigh, right gastrocnemius, pectoral, and axillary) were measured to the nearest 1 mm using skinfold caliper (Holtain, Crymych, United Kingdom) on the right side of the body (21). For each skinfold, 3 measurements were obtained, then the mean was calculated. The sum of the skinfold thickness was used as indicator of total body fat.
Conditional parameters of strength were measured using force platform (Quattro Jump; Kistler Instrumente AG, Winterthur, Switzerland). All subjects were asked to perform both squat jump (SJ) and countermovement jump (CMJ). Squat jump started with leg on 90° flexion and hands on hips and CMJ started with leg on extension and hands on hips to go down to 90° flexion and jump immediately as high as possible. Each jump was performed 3 times and the best jump was used. Two-minute rest was carried out between repetitions and a standard warm-up of 10 minutes was performed before jumps trial (low-intensity aerobic exercise, dynamic stretching, and 5 submaximal jumps) (7,39). All subjects were verbally encouraged to jump with maximal effort. Only the best performance for each jump was retained for statistical analysis.
Normality of distribution and homoscedasticity of the data were verified by the Shapiro-Wilk and Levenne tests, respectively. Scatter plots were used to examine linearity in relationship between dependent (100 m time performance) and independent variables potentially predictive to meet the assumptions of linear regression. Mean and SD values were calculated for all parameters (Table 1). Coefficient of variation of performance was calculated. The differences between mean of both genders groups were compared by analysis of variance of a single factor. Bivariate Pearson's correlation coefficient was calculated to quantify the relationships between trial time and each variable potentially predictive. The relative contribution of independent variables on 100-m front-crawl performance was calculated by stepwise multiple linear regression analysis (p of F for inclusion ≤0.05, p of F for exclusion >0.1), including all variables showing a significant association with 100 m time after bivariate analysis as covariates in the model. Variables were included in order from the variable explaining the greatest to the least variance. The intraclass correlation coefficients were calculated for each dependent variable to determine test-retest reliability, obtaining values always greater than 0.95. A p-value ≤0.05 was considered to be statistically significant. SPSS for Windows (version 18.0; SPSS Inc, Chicago, IL, USA) was used for all analyses.
Descriptive statistics for pulmonary function, anthropometric, demographic, conditional, and performance parameters and their differences between genders are presented in Table 1. The coefficient of variation of the swimming performance showed homogeneity of the male (3.0%) and female (6.5%) groups. Male swimmers were older, taller, and heavier and showed less amount of adipose tissue than female swimmers (p ≤ 0.05). Male swimmers showed higher level of performance in the trial time, higher height in SJ and CMJ test, and higher values in almost all pulmonary function parameters than female swimmers (p ≤ 0.05), except for FEV1/FVC and FIV1, showing the last parameter a trend toward significance (p = 0.061).
Relationships between 100-m front-crawl performance time and variables of male and female swimmers are presented in Table 2. Correlation coefficient analysis showed that FIV1 was negatively correlated with 100-m front-crawl time in male swimmers. Forced inspiratory volume in the first second and FVC were negatively correlated with time trial in female swimmers.
Multiple linear regression analysis results for male (F = 9.53, R2 = 0.66, p = 0.027) and female (F = 9.60, R2 = 0.58, p = 0.017) swimmers are presented in Table 3. In this regression, all variables with significant relationship with time trial were introduced. Multiple linear regression analysis demonstrated that FIV1 was the only significant determinant of 100-m performance and explained 66% of the variance in male swimmers. As in the analysis of male swimmers, FIV1 was the only significant determinant of 100-m performance and explained 58% of the variance in female swimmers.
The main findings show that FIV1 is the only predictor of front-crawl performance among different anthropometric, conditional, and pulmonary function parameters in male and female young sprint swimmers and that there are significant differences between both genders in anthropometric, conditional, pulmonary function, and performance parameters.
This is the first study that determines the influence of FIV1 in 100-m front-crawl sprint in national-level competitive swimmers. According to our finding, FIV1 is able to explain 66% of 100-m time trial variance in male swimmers and 58% in female swimmers. The high influence of FIV1 in 100-m front-crawl sprint can be partly explained because greater FIV1 makes it possible to achieve faster maximum inspirations, and this is important for elite swimmers because this would allow them to increase the amount of air they can inhale in the limited time (0.3–0.5 seconds) (40) their face is out of the water (25). The expiratory phase can basically be executed at any time in the stroke cycle, while the appropriate inspiratory timing and velocity can affect swimming performance and must adhere to the stroke cycle as a whole (22). Swimmers with high FIV1 may need less respiratory frequency, produce less inspiratory muscle fatigue, increasing active limbs blood flow and reducing fatigue in these limbs (33), and consequently may improve performance. Increases in FIV1 may be a direct result of an increase in the velocity of shortening of the inspiratory muscles as a consequence of enhanced inspiratory muscle strength (25). Elevated lung volumes observed in swimmers have been suggested to be related to elevated inspiratory muscle strength (6). Consequently, we suggest evaluating pulmonary function parameters routinely and analyzing them as swimming performance predictors.
Previous studies support that inspiratory muscle training improves performance in untrained subjects (11) and trained subjects of different endurance sports as athletics (9) or rowing (12). To our knowledge, only 2 studies (17,20) evaluated young local-level competitive swimmers and showed that respiratory muscle training improves time trial. Another study (40) showed significant correlation between inspiratory muscle training and FIV1 in adolescent national-level competitive swimmers. These findings indicate that the inspiratory muscle training may be an option to reach optimal level of swimming performance (17,20). A recent meta-analysis demonstrated that swimming performance showed inconsistent improvements in response to respiratory muscle training compared with control group (13). Small sample sizes (≤10 swimmers per group) and the facts that restricted breathing, prone position of swimming, and water pressure on the thorax during regular swim training already elicit effects upon the pulmonary system similar to those of isolated respiratory muscle training may explain these inconsistencies. Future studies to examine the optimal type of training to improve respiratory parameters and swimming performance in competitive swimmers are clearly needed.
In our study, anthropometric and conditional variables did not show significant correlation with swimming performance and consequently were not determinants in the performance prediction. However, another studies found that anthropometric factors could explain ∼46% of 100-m front-crawl variability in young regional-level competitive swimmers (19). Strzała and Tyka (37) found that velocity in sprint swimming performance can be compromised by total body length and lean body mass in young swimmers. Geladas et al. (10) showed high correlation between upper extremity length and 100-m front crawl in adolescent swimmers. These discrepancies with our results may be resulting from our lack of assessments of important specific anthropometric variables (i.e., arm span, lean body mass) and to our small sample. Strength variables such as SJ and CMJ and their relationship with swimming performance have been poorly studied (3,29,41), although lower limb power may be determinant in sprint starts (4,41). West et al. (41) found high correlation between start crawl time and 1 maximal repetition strength, jump height in CMJ, and peak and relative power in international sprint swimmers. Breed and Young (4) showed a correlation between CMJ performance and flight distance in swimming starts. The absence of correlation between strength variables and swimming performance in our data may be because of the lack of additional plyometric and dry-land strength training programs that enhance the development of the explosive strength of the swimmers and also to the small sample.
The results of the present study reveal significant differences between both genders in pulmonary function, anthropometric, and conditional parameters. Male swimmers show higher values than female swimmers in some pulmonary function, such as FVC, PIF, FEV1, FEF25–75, and MVV. These differences were consistent with previous studies (14) and could be explained by reduced lung size, reduced airway diameter, decreased maximal expiratory flow rates, and smaller diffusion surface in women. As expected, our female swimmers had greater fat stores, measured by skinfolds, compared with male swimmers. These findings were consistent with previous studies (23,32,42). In addition, weight, height, and BMI were decreased in female swimmers compared with male swimmers, as shown by previous studies (23,32). It has been suggested that female swimmers have greater fat mass and lower BMI compared with male swimmers because the latest have a greater proportion of muscle mass and therefore greater weight and BMI, given that BMI does not distinguish between fat and lean mass (23). Our female swimmers reached 75 and 83% of values obtained by males in SJ and CMJ height, respectively. It may be explained by elevated fat mass and reduced muscle mass in female swimmers, being these differences probably influenced by hormonal differences (e.g., higher production of testosterone in male swimmers).
The present study presents several limitations. First, the lack of sample size minimizes the representativeness of the same, although Mairena del Aljarafe swimming club is the Andalusian club with the highest number of national-level swimmers. Therefore, it is difficult to find a homogeneous group with these characteristics in our region. Second, specific anthropometric variables for swimmers, such as hand and arm span or hand and feet surface, were not taken in to consideration (10,19). Third, our study could have included upper strength variables to value the relation to final performance. Finally, biomechanical variables significant in swimming performance have not been taken into account because of the large number of studies performed about this issue. Lätt et al. (19) found that biomechanical variables explain ∼90% of 100-m swimming performance variance. Other biomechanical parameter such as stroke length is a good predictor in the global competitive performance (34). Therefore, although biomechanical variables have not been measured in our study, it seems important to emphasize the value of a good technique teaching from the beginning of swimming learning. Despite all these limitations, it is observed for the first time a relationship between swimming performance and FIV1 in male and female homogeneous groups of front-crawl sprint swimmers. Further studies with higher sample size are needed to analyze relationship between swimming performance and pulmonary function parameters in all 4 competitive strokes and all race distances.
In conclusion, our study demonstrates that FIV1 is the only predictor of 100-m front-crawl performance of all anthropometric, conditional, and physiological variables measured in young national competitive swimmers. Other finding is that female swimmers present lower limb strength and pulmonary function parameters and more body fat mass than male swimmers with better time trial.
It could be suggested that FIV1 may be an important limiting factor for optimal front-crawl performance in young sprint swimmers. In this sense, FIV1 value tested in the present study could be a good predictor of performance and it should be evaluated routinely and used by coaches for talent identification in front-crawl sprint swimmers. Therefore, it makes sense to include inspiratory musculature training exercises in swimmers training routines for sprint swimmers. Future research may analyze different inspiratory training exercises to help the coaches and swimmers to design those training stimuli more related to success.
This study provides a comprehensive profile of elite young sprint swimmers based on pulmonary function, conditional, and anthropometric characteristics. The information in this study can be used by coaches to compare characteristics of their front-crawl swimmers with a group of male and female national level young sprint swimmers.
Differences between the male and female sprint swimmers were for anthropometrics, conditionals, and pulmonary function measures. These differences may adversely affect swimming performance and potentially explain gender differences in performance. These findings suggest that the swimming performance for female swimmers may be improved through training programs designed to reduce body fatness and increase parameters of strength of the lower extremities and pulmonary function.
The authors thank Antonio Reina and the many swimming coaches for their assistance in subject recruitment, and the swimmers for volunteering their time to participate in the study. The authors state that the results of the present study do not constitute endorsement of the equipment by the authors or the National Strength Conditioning Association.
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