Bilateral asymmetries in male and female young elite fencers in relation to fencing performance

1. Introduction

Limb asymmetries, e.g. over 10–15% strength deficits between the limbs, are thought to be of clinical importance because they have been linked with increased risks for sports-related injuries [1, 2] and unsuccessful readiness of the injured athlete for return to training or competition [3]. Thus, monitoring the bilateral asymmetries is a way to prevent athletes’ injuries as well as to determine injured athletes’ readiness to participate again in sports events and training programs [3]. Unfortunately, the nature of many sports seems to promote bilateral asymmetries [4] as they have been repeatedly reported after power [1, 6] or strength-based evaluations [2, 6]. However, according to a recent systematic review [4] there is an inconsistency about the impact of bilateral asymmetry on physical and sport performances highlighting the need of further investigation in this topic.

Fencing is an Olympic sport in which athletes’ attacking success is highly dependent on technical and powerful forward unilateral lunges [7, 8, 9, 10]. During these lunges the upper limb movement is followed by the robust extension of the front knee, the dominant (D) leg, and the vigorous lengthening of the back leg, e.g. ND leg, during the push-of phase [11, 12]. Considering this kinetic chain there is a significant dissociation between the role of the front and rear leg [13]. It seems that ND leg knee extension muscles and triceps surae are activated firstly and they are responsible for the power/force production and transmission during the propulsive (concentric) action, while leg extensor and triceps surae of the D leg is responsible for the “braking” (eccentric phase), and stabilization of the leg, during this phase [14]. These significant differences between the actions and movement induced differential mechanical stresses between the front and rear legs during the attacking lunches, resulting in strong bilateral asymmetries between the two legs with a significant impact on fencing performance and injury risk [14]. However, data about the possible strength and power asymmetries between the lower extremities in fencers, and especially in young athletes, are limited and inconsistent [14, 15, 16, 17, 18] while the majority of the existing studies investigate mostly the anthropometrical-morphological asymmetries between the D and the ND legs of fencers, again with controversial results [8, 10, 14, 15, 17, 18]. Taking together the above, it is interesting to identify if fencing and its training routine may or may not lead to bilateral asymmetries of young athletes as well as to explore these asymmetries in relation to fencing performance.

Probably, the reason for the inconsistency about the presence of bilateral asymmetry between the D and the ND leg of fencers may rely on the different tests and methodologies that are widely used to detect these asymmetries. Until now, both open (mostly isokinetic dynamometers) and close (vertical and horizontal jumps) kinetic chain tests have been used for this evaluation. Closed kinetic chain tests can provide sports-specific data because they include stretch-shortening cycle and force production in high velocities, relative to those observed during the real movement executions [19]. In contrast, through open kinetic chain tests, peak and mean forces and flexion/extension muscle strength ratios (F/E ratio) could be retrieved, providing more accurate data about the strength status of each muscle-muscle groups [6, 16, 20]. However, these assessments require specific and costly equipment while they have low sport-related specificity. On the other hand, the limited data about lower limbs asymmetries in fencers, even if some studies adapt the same kinetic chain tests, are highly inconsistent and not allowing a precise and clear view on this issue [14, 15, 16, 17, 18]. Finally, to the best of our knowledge whether open and close kinetic chain tests provide the same results regarding the existence of muscles and/or limb asymmetries, has not been examined, at least with respect to this specific cohort.

The aim of the present study was hence to investigate the asymmetries between D and ND legs of elite young male and female fencers in relation to performance in fencing specific tests. It was hypothesized that the D and ND leg of elite young male and female fencers would be characterized by a significant asymmetry, negatively related to fencing performance.

2. Methods

Significant differences between genders were found for height, body mass, body fat, arm span and leg’s length ( 0.05; Table 1). No significant differences were found, either for the comparison between the genders nor for the comparison between D and ND leg, for mid-thigh circumferences (MTC) and cross-sectional areas (CSA; $p>$ 0.05; Table 1).

Significant gender differences were found in unilateral drop jumps height for the D ( p = 0.004, d = - 0.19) and the ND leg ( p : 0.006, d = - 0.04 Table 2), as well as for both legs’ triple hop distance (D: p : 0.000, d = 2.09; ND: p : 0.000, d = 1.53; Table 2), with male athletes to achieve higher performances. Significant gender differences were observed for peak velocities and power production in lunge ( p : 0.000; d : 1.35 and 1.47 for velocity and power respectively) and step lunge ( p : 0.000; d : 1.52 and 1.67 for velocity and power respectively) fencing tests in favor of male athletes (Table 2). In addition, significant differences between male and female athletes were observed in all isokinetic tests (Table 3). Specifically, male athletes achieved higher absolute peak moments in all angular velocities in both D (Extension: 0.001, d : 1.53, 1.49, 1.55; Flexion: 0.001, d : 1.44, 1.38, 1.45 for 60, 180 and 300 ∘ /s respectively) and ND legs (Extension: 0.001, d : 1.30, 1.46, 1.63; Flexion: 0.001, d : 1.65, 1.75, 1.37 for 60, 180 and 300 ∘ /s respectively). Similarly, male athletes achieved higher relative to BW peak moments in all angular velocities in both D (Extension: 0.001, d : 1.22, 1.08, 1.57; Flexion: 0.001, d : 1.42, - 0.11, 0.37 for 60, 180 and 300 ∘ /s respectively) and ND legs (Extension: 0.001, d : 1.39, 0.84, 1.40; Flexion: 0.001, d : 1.49, 0.34, 0.97 for 60, 180 and 300 ∘ /s respectively; Table 3). No significant differences were found for F/E and rF/E ratios, at any angular velocity ( $p>$ 0.05). No significant differences were found between D and ND legs in all cases (Bilateral asymmetries; $p>$ 0.05; Tables 2 and 3). No significant interaction between gender and laterality effects were found for drop jump ( p = 0.65), triple hop ( p = 0.56), absolute ( p = 0.273–0.789), relative ( p = 0.351–0.974) peak moments in all isokinetic tests and lunge and step lunge performances ( $p>$ 0.450; (Tables 2 and 3).

Step lunge peak velocity and power were negatively correlated with D leg’s F/E and rF/E ratios at 300 ∘ /s in male fencers (r: - 0.570 and r: - 0.619 respectively, 0.05; Table 4). In contrast, positive correlations were found between step lunge peak velocity, power, F/E and rF/E ratios at 300 ∘ /s in male fencers (r: 0.522 and r: 0.557 respectively, 0.05; Table 4). D leg’s F/E ratio at 300 ∘ /s was positively related to lunge peak velocity and power in female athletes (r: 0.562–0.649; 0.05; Table 4). Finally, only in female athletes, triple hop distance either of D or ND leg, was significantly related to lunge peak velocity and power (r: 0.442–0.500; 0.05; Table 4).

4. Discussion

The main finding of the present study was the existence of symmetry between D and ND legs either in close or in open kinetic chain tests in young elite male and female fencers. In contrast, as it expected, significant gender differences were found in unilateral drop and triple jump, in isokinetic absolute and relative peak moments at all angular velocities for both legs and in fencing specific kinetic patterns (peak velocity and power of lunge and step and lunge) in favor of males. Finally, fencing specific performances were highly related to the extent of isokinetic knee muscles’ flexion/extension ratio during high angular velocities (300 ∘ /s) as well as to performance in the unilateral triple hop test.

Fencing is characterized by close kinetic movements of the lower limbs in which knee flexors and extensors muscles of D and ND limb contract differently and not on the same phase during fencing assault [8, 9, 10, 11, 12, 13, 17, 18]. Indeed, during fencing training or competitions massive and repeated eccentric forces are applied at the final phase of lunge on the D limb while propulsive forces are produced from the ND limb during the initial phase of the lunge. Thus, these differential actions may lead to morphological, functional and dynamic asymmetries between the limbs as well as between each leg’s muscles as it has been previously reported [8, 9, 10, 13, 14, 15]. However, the results of the present study do not agree with these reports indicating the absence of any morphological, functional and dynamic asymmetries at least in elite young male and female fencers.

In the present study mid-thigh circumferences and crossectional areas of the D and ND leg did not differ either in male or female young fencers. Recently, significant differences between D or ND legs’ cross-sectional areas have been reported in moderate trained but not in elite fencers [14]. In addition, the observation of these asymmetries in cross-sectional areas of D and ND legs can strongly distinguish the elite from non-elite fencers [14]. Furthermore, mid-thigh crossectional area asymmetries between lower limbs have been reported only in adult fencers and not in the young athletes [18]. Thus, the absence of any asymmetries between lower limbs’ mid-thigh crossectional areas that were observed in the present study could be due to the young age and level (elite), verifying the previous reports [8, 14].

Until now only two studies investigated asymmetries in fencers using isokinetic strength evaluations [15, 16]. Males’ peak moment values at 60 ∘ /sand 180 ∘ /s of the present study were lower than those previously reported [15]. However, these differences can be easily explained since our participants were younger and less experienced in comparison to the Olympic level Swedish fencers who have participated the study of Nyström et al. [15]. The present study revealed no significant asymmetries between legs but only between genders in all angular velocities. This is in agreement with Poulis et al. [16], who showed significant differences only between elite and moderate trained fencers in all angular velocities (30 ∘ /s, 60 ∘ /s and 240 ∘ /s). Furthermore, and in accord with Poulis et al. [16], no significant differences in F/E ratios were observed either within or between gender groups. Thus, the present study supports the observation that sports dominance does not necessarily induce asymmetries either between the limbs or within the muscle of each limp at least when asymmetries are evaluated thought isokinetic tests [16].

Unfortunately, the use of open kinetic chain tests only (their accuracy notwithstanding) fails to reflect the mechanical and metabolic demands of a close kinetic chain sport [4] like fencing. Therefore a more sport-specific approach using muscle contractions that incorporate the stretch-shortening cycle such as unilateral vertical and horizontal jumping tests [7, 20] might have provided a better insight of this issue [4]. Indeed, drop jump performance seems to be the stronger predictor of fencing performance compared to other types of strength and power performance tests [7, 8, 18] while it has been recently reported that after strength and conditioning programs with horizontal jumps fencing performance is significantly increased [33]. In the present study no significant asymmetries in unilateral drop and triple jump performances were found, both in elite male and female young fencers, observations that were in accord with that of the isokinetic test reinforcing the conclusion that the unilateral nature of fencing and the differential activation/movement pattern of the D and ND leg’s muscles do not lead to lower extremities’ asymmetries.

Furthermore, the current results agree with those of a previous study which indicated that in elite fencers there was an absence of any lower extremities’ performance asymmetries during vertical close kinetic chain test in contrast to sub-elite fencers where significant asymmetries were found [14]. Thus, considering all the above it seems that elite young male and female fencers are not characterized by any strength/power performance asymmetries in both open and close kinetic chain tests. However, if this is a genetic outcome or a specific training induced adaptation is something that should be further investigated.

Specific only to the female participants lunge and step lunge performances were significantly correlated with D and ND leg’s triple hope performances, a finding that shows that although both legs are characterized by different kinetic patterns during fencing they contribute equally to fencing performance. In contrast, these correlations were not found in male participants. Moreover, F/E ratios of D leg, during the high angular velocity effort (300 ∘ /s) were positively correlated with lunge and step-lunge performances in female fencers but negatively in male young athletes. According to these results it seems that lower (significantly stronger knee extension muscles) F/E ratios in male fencers, and higher (almost equal strength between knee flexion-extension muscles) F/E ratios in male fencers are related to higher step lunge performances. The previously mentioned differential correlations indicated that young male and female fencers may rely on differential, biomechanical, but mostly physiological parameters, during their fencing efforts. Indeed, performances in explosive activities are highly affected by the muscle size, muscle fiber composition and the neural activation [25, 27, 29, 34, 35, 36]. However, the function of the nervous system (e.g. agonist muscle activation, antagonist muscle coactivation or inactivation, etc.) may have the most important contribution on gender-related differences in sports performances [37, 38], while the training-induced increases of muscle size and activation are significantly different between genders of this age [37, 38]. On the other hand, these correlations may also indicate that male athletes rely mostly on their D leg strength and musculature, mainly of the quadriceps, to stop/control their movement during the “braking” phase. On the other hand, women rely mostly on high power production. Unfortunately, a limitation of the present study was that eccentric knee flexion/extension muscles isometric maximum strength was not evaluated. Thus, the previously mentioned suggestion could not be verified from the data of the present study and future studies should investigate this conjecture. However, this conclusion may be supported by the fact that these correlations were found only during the isokinetic test with high angular velocities while significant correlations were found between triple hop and lung performance only in the female participants. In addition, during the triple hop test, as a close kinetic chain action which includes the stretch-shortening cycle and force production in high velocities, participants performance depends on high muscle power production and not on their maximum strength [30]. However, further exploration are needed to explain the correlations of this study, as well as examine the relationships between neuromuscular qualities, different forms of strength (isometric, concentric-eccentric contractions) and fencing performance (force plates) to provide additional information to the coaches that could lead to a design of more effective strength and conditioning training programs to maximize fencing performance.

5. Conclusion

The results of the present study suggest that in young male and female fencers the differential activation/movement pattern of the dominant, non-dominant leg’s muscles, and the lower extremities’ movement specificity of the fencing do not lead to anatomical, dynamic and functional lower extremities asymmetries.

Author contributions

CONCEPTION: PanagiotisKoulouvaris and Charilaos Tsolakis.

PERFORMANCE OF WORK: Vasiliki Drakoulaki, Nikolaos Kontochristopoulos, Theocharis Simeonidis, Evgenia Cherouveim and Olga Savvidou.

INTERPRETATION OR ANALYSIS OF DATA: Spyridon Methenitis, Vasiliki Drakoulaki, Nikolaos Kontochristopoulos, Theocharis Simeonidis, Evgenia Cherouveim and Olga Savvidou.

PREPARATION OF THE MANUSCRIPT: Spyridon Methenitis.

REVISION FOR IMPORTANT INTELLECTUAL CONTENT: Spyridon Methenitis, Evgenia Cherouveim, Panagiotis Koulouvaris and Charilaos Tsolakis.

SUPERVISION: Charilaos Tsolakis.

Ethical considerations

The present study was approved by the School of Health Sciences, National and Kapodistrian University of Athens ethics committee (Ref. Number: 24-7-2019/1819041221) while written parental consent forms were obtained prior to the entry of each athlete in the study, after a detailed written description of the procedures.

Funding

The authors report no funding.