INTRODUCTION

Functional Movement Screen (FMS) test battery has been proposed as a reliable instrument to assess athletes' functional movement patterns in daily sports practice (^{Kraus et al, 2014}; Grible et al, 2013, ^{Onate et al., 2012}; ^{Teyhen et al., 2012}, ^{Minick et al., 2010}). Moreover, despite controversial evidence (Mokka, Sprague, & Gatens, 2016), FMS composite scores under 14 points have been suggested as a cut-off point to predict musculoskeletal injury risk among athletes (^{Chorba et al., 2010}; ^{Kiesel, Plisky, & Voight, 2007}; ^{O`Connor et al., 2011}). FMS comprises 7 fundamental movement patterns that require mobility, neuromuscular control, balance, and stability. To evaluate movement functionality, athletes are assessed on a scale from 0 to 3, in which 0 denotes experienced pain and 3 indicates that the movement was completed without any compensation (^{Cook et al., 2014}a). The highest total score that can be attained on the FMS is twenty-one points(Cook et al., 2014b). Even though the FMS test battery has been used by sports professionals to assess functional movement patterns in several sports (^{Anderson, Nrumann, & Bliven, 2015}, ^{Marques et al., 2017}; ^{Kuzuhara, et al, 2018}; Kiesel, Plisky, & Butler, 2011; ^{Nicolazakes et al., 2017}), only a few applied it to swimmers (^{Bond et al., 2015}; ^{Gunay, et al., 2017}, ^{Bullock et al, 2017}).

Swimming is a sport that involves closed and continuous motor skills (^{Duarte-Mendes et al, 2019}) and the performance can be influenced by several factors such as physiological, biomechanical, and anthropometric characteristics (^{Okada, Huxel, & Nesser, 2011}). The relationship between physical characteristics and sprint swimming performance in young swimmers has been studied (^{Connaboy, et al., 2015}; ^{Geladas, Nassis, & Pavlicevics, 2005}; ^{Garrido et al, 2012}). Ankle, knees, hip, and shoulder mobility have been referred to as key kinematic determinants of undulatory underwater swimming at maximal velocity (Connaboy, et al., 2015). Interestingly, ankle and shoulder mobility were not related to swimming performance in male swimmers, whereas shoulder mobility was significantly related to 100m freestyle performance in female swimmers (Geladas, Nassis, & Pavlicevics, 2005). To aid scientific research on this topic, the relationship between FMS scores and young swimmers' performance has been analyzed (^{Bond et al., 2015}; ^{Gunay, et al., 2017}). Despite the few studies, higher FMS composite scores have been positively related to 100m freestyle performance in youth swimmers (Bond et al., 2015), while 200m individual medley performance does not seem to be related to FMS composite scores in youth swimmers (Gunay, et al., 2017). However, given that in freestyle races any swimming stroke may be used (FINA rules, 2017), this technique may be more representative of swimmers' functional movement patterns. Further, the 100m freestyle long course event is the key distance in competitive swimming and has been on every Olympic program since 1904 (men) and 1912 (women) (^{Post et al., 2020}).

To the best of our knowledge, there are no studies comparing FMS scores in elite and non-elite swimmers, specifically at young ages (under eighteen years old). In fact, swimming performance from a young age is highly valued and considered as a strong predictor of success (KNZB, 2020). Assessing the physical skills of young swimmers is important for coaches, sports professionals and swimmers (^{Bond et al., 2015}). This knowledge could be relevant for swimming coaches, being able to effectively manage young elite and non-elite swimmers' movement functionality according to their specific needs, maximizing performance. Thus, the aim of the current study was to assess and compare FMS scores between young elite and non-elite swimmers, as well as to verify their relationship with 100m freestyle performance. It was hypothesized that elite swimmers would have higher FMS scores compared to non-elite swimmers. A secondary hypothesis was that FMS composite scores would be positively correlated to 100m freestyle performance.

MATERIAL Y MÉTODOS

RESULTADOS

The subject's anthropometric characteristics and FINA points are displayed in Table I.

Table I.  Anthropometric characteristics and FINA points of young elite and non-elite swimmers. 

Table note: Data are expressed as mean ± standard deviation (SD).

Table II presents the values of FMS individual-test scores and FMS composite scores, as well as differences between group analysis. Differences were found between elite and non-elite groups on the Deep Squat (p = 0.005; ES = 0.99, large effect), Right Hurdle Step (p = 0.005; ES = 0.99, large effect), Left Hurdle Step (p = 0.002; ES = 1.08, large effect) and Trunk Push Up (p < 0.001; ES = 1.4, large effect) tests. Although there were no statistically significant differences between groups on the Left Rotary Stability, the effect size indicates a moderate effect (p = 0.114; ES = 0.52). The elite group achieved higher scores for all tests, except for the Left Shoulder Mobility. However, no statistical differences were found in the aforementioned test (p = 0.472; ES = 0.2). The elite group FMS composite scores were significantly higher (p < 0.001; ES = 1.35, large effect) compared to the non-elite group.

Table II.  Descriptive statistics (mean ± SD) of FMS individual-test, FMS composite score, and differences between group analysis. 

There was a positive and moderate relationship (r = 0.596, r² = 40.9%, p < 0.001) between FMS composite scores and 100m freestyle performance (FINA points) (Figure 1).

Figure 1.  Correlation between FMS composite scores and FINA points (r = 0.596, p < 0.001). 

DISCUSIÓN

The purpose of the current study was to assess and compare FMS scores in young elite and non-elite swimmers and to verify their relationship with 100m freestyle performance. The main findings of the present study were: (i) young elite swimmers achieved significantly higher Deep Squat, Left Hurdle Step, Right Hurdle Step, Trunk Stability Push Up and FMS composite scores compared to young non-elite swimmers; (ii) FMS composite scores were positively correlated with 100m freestyle performance.

FMS has been used to assess functional movement patterns in several sports (^{Anderson, Nrumann, & Bliven, 2015}, ^{Marques et al., 2017}; ^{Kuzuhara, et al, 2018}; ^{Kiesel, Plisky, & Butler, 2011}; ^{Nicolazakes et al., 2017}). However, only a few applied FMS to swimmers (^{Bond et al., 2015}; ^{Gunay, et al., 2017}, ^{Bullock et al, 2017}) and no studies have compared FMS scores between young elite and non-elite swimmers.

In the present study, the elite group achieved significantly higher Deep Squat, Left Hurdle Step, Right Hurdle Step, Trunk Stability Push Up and FMS composite scores than the non-elite group. These results suggest that young non-elite swimmers may have relevant functional deficits in tasks involving mobility of the hips, knees and ankles (Deep Squat test), proper stride mechanics during a stepping motion (Hurdle Step test), and also stabilization of the core and spine in an anterior and posterior plane during a closed-chain upper body movement (Trunk Stability Push Up test). Future studies aiming to identify or differentiate movement functionality deficits in young elite and non-elite swimmers are needed. This would allow swimming coaches to provide training programs according to swimmers' specific needs in an early stage of their careers, which has been suggested to predict future competitive success (^{Post et al., 2020}).

Interestingly, even though we have not found significant differences between young elite and non-elite swimmers in the Shoulder Mobility test, the non-elite group achieved higher scores on Left Shoulder Mobility test. The Shoulder Mobility test assesses bilateral and reciprocal shoulder range of motion, combining internal rotation with adduction of one shoulder and external rotation with the abduction of the other. The test also requires normal scapular mobility and thoracic spine extension (^{Cook et al., 2014}b). It is widely agreed that swimming injuries are overuse in nature (^{Hill, Collins, & Posthumus, 2015}; Kerr et al., 2013) and highly frequent in shoulders during an athlete's career (^{Barbosa et al, 2000}; ^{Blache, 2018}). Despite the higher scores on the Left Shoulder Mobility test, the non-elite group revealed higher asymmetry incidence when compared to the elite group. That might be due to the breathing technique used during freestyle swimming if there is a lateral dominance that may lead to incorrect swimming technique and increase those imbalances (^{Higson, 2018}). Therefore, more research is needed to clarify the potential influence of swimming techniques on movement functionality asymmetries which may predispose swimmers to overuse injury.

There is limited data regarding the relationship between FMS scores and physical performance among athletes (^{Kraus, 2014}; Silva et al., 2015). In fact, a thorough search of the relevant literature yielded only two studies analyzing the relationship between FMS composite scores and swimming performance (^{Bond, 2015}; ^{Gunay, 2017}). When analyzing the referred relationship, we found a positive correlation between FMS composite scores and 100m freestyle performance, i.e., young swimmers with higher levels of movement functionality were able to achieve better performances. These results supported previous research where 100m freestyle performance was also positively related to movement functionality in young swimmers (Bond, 2015). In another study, the authors analyzed the relationship between FMS composite scores and 200m individual medley swimming performance (Gunay, 2017). Although they did not find a correlation between the aforementioned variables, it should be noted that the distance and swimming stroke analyzed were not the same as ours. Since FMS comprises 7 fundamental movement patterns that require mobility, neuromuscular control, balance, and stability, our results also support previous research that referred to ankle, knees, hip and shoulder mobility as key kinematic determinants of sprint swimming performance (^{Connaboy, 2015}). Interestingly, ankle and shoulder mobility have not been related to swimming performance in male swimmers, whereas shoulder mobility was significantly related to 100m freestyle performance in female swimmers (Geladas, Nassis, & Pavlicevics, 2015). However, these authors did not use FMS test battery and thus more research is needed to clarify the relationship between swimmers' functional movement patterns assessed through FMS and 100m freestyle performance.

There are some limitations that we should be aware in the current study. First, we should mention the sample's dimension and heterogeneity (elite group n = 32; non-elite group n = 17). Secondly, we have considered neither the athlete's history of injuries nor the training frequency. Past injuries and training frequency should be considered since those variables potentially impact on swimming performance (^{Okada, Huxel, & Nesser, 2011}). Our sample consisted of only young swimmers and we should be careful when generalizing our findings for older trained swimmers. All variables were assessed at one moment (cross-sectional design) (^{Cid et al., 2019}; ^{Monteiro et al., 2018}, ^{Rodrigues et al., 2019}). Finally, we have not analysed analyzed relevant variables such as anthropometric data (e.g.: skinfolds, body fat percentage, waist-to-hip ratio). By including anthropometric data, we could have been able to draw more accurate comparisons with previous studies. Further research including longitudinal and experimental investigation on functional movement development and physical performance in young swimmers is needed.

CONCLUSIONES

Our findings have shown that young elite swimmers have higher movement functionality compared to young non-elite swimmers. In fact, young non-elite swimmers might have relevant functional deficits in tasks involving mobility of the hips, knees and ankles, proper stride mechanics during a stepping motion, and also stabilization of the core and spine in an anterior and posterior plane during a closed-chain upper body movement. Furthermore, our results suggest that young swimmers with higher movement functionality are able to achieve better performances in 100m freestyle.

PRACTICAL IMPLICATIONS

Swimming coaches/medical staff should be aware of the potential movement functionality differences between young elite and non-elite swimmers since specific deficits require adjusted training programs in order to maximize performance.