International Journal of Environmental Research and Public Health Article Asymmetry of Musculature and Hand Grip Strength in Bodybuilders and Martial Artists Anna Burdukiewicz * , Jadwiga Pietraszewska , Justyna Andrzejewska, Krystyna Chromik and Aleksandra Stacho ´n Department of Physical Anthropology, University School of Physical Education, 51-612 Wrocław, Poland; [email protected] (J.P.); [email protected] (J.A.); [email protected] (K.C.); [email protected] (A.S.) * Correspondence: [email protected]; Tel.: +48-71-3473313 Received: 9 June 2020; Accepted: 27 June 2020; Published: 30 June 2020 Abstract: The functional preference for the upper limb influences the occurrence of bilateral differences in other segments of the human body. The aim of the study is to assess the influence of the applied fighting technique and targeted physical effort on the occurrence of asymmetry in body musculature and isometric strength in bodybuilders and competitors of selected martial arts. Academic athletes practicing judo (J), jiu-jitsu (JJ), and bodybuilding (BB) were examined. The control group (C) consisted of students who do not practice any sports. The assessment of the body structure was conducted through segmental bioelectrical impedance analysis. Moreover, the study took into account the measurements of left- and right-hand grip strength. In judo, the uneven physical exertion of the right and left sides of the body further increases both directional and absolute asymmetry. Bilateral asymmetry of musculature in jiu-jitsu competitors and bodybuilders occurs to a lesser extent. The control group was characterized by cross-asymmetry. So as to avoid the risk of injury of sportsmen, it is important to consistently supervise and correct their body structure, which also includes the symmetrical participation of the active muscle mass in particular segments. The symmetrisation process should be individualized since each particular sportsman has their own side-to-side body morphology. Keywords: bilateral asymmetry; muscle mass; hand grip strength; bodybuilding; jiu-jitsu; judo 1. Introduction Humans are the only species among the primates that are characterized by directional asymmetry, which is caused by lateralization. It is manifested in their preference for the right upper limb [1]; this fact, in turn, means that bilateral discrepancies occur consistently across the population. In contrast, fluctuating asymmetry takes form of non-directional deviations from the expected symmetry. In addition, there is anti-symmetry, which is a non-systematic bilateral difference in the population. Directional asymmetry and antisymmetry are considered to be conditioned genetically to a certain extent, whereas fluctuating asymmetry is a manifestation of developmental instability [2,3]. It is estimated that the frequency of left-handedness equals 10–13%, although there is some degree of variance caused by socio-cultural and geographical factors [4]. Left-handedness appears to be quite advantageous in the context of one-on-one combat: A certain dose of unpredictable behavior may directly affect the outcome of a fight. The literature on the subject confirms this observation: The research has shown that left-handed sportsmen tend to be overrepresented on the professional level in the contact sports whereas no such dependence has been found in the non-contact sports [5]. In order to counteract the temporal and spatial limitations present in contact sports, the competitors develop their cognitive skills, perception, and motor abilities relevant to the actions they perform [6]. Int. J. Environ. Res. Public Health 2020, 17, 4695; doi:10.3390/ijerph17134695 www.mdpi.com/journal/ijerph Int. J. Environ. Res. Public Health 2020, 17, 4695 2 of 11 The prevalence of right-handed competitors may be causing the development of a skillset that allows sportsmen to better equipped against the right-handed opponents, rather than the left-handed [7]. This allows the competitors to be more effective at predicting the actions that the right-handed competitors intend to take whereas the actions of the left-handed competitors are more difficult to predict [8]. The research has also shown that the left-handed competitors also tend to perform better when under time pressure [9]. Vertebrates are characterized by behavioral lateralization, which manifests in directional asymmetry; the extent to which the asymmetry occurs is dictated by the differences in the mechanical strain that lead to deviations from perfect symmetry [10,11]. In humans, functional preference for the right upper limb means that the domination of the latter over the left upper limb in terms of the morphological features is very pronounced. Sports practice causes asymmetrical development of bones and musculature of the dominant limb [12]. Heavy labor can also impact the body in a similar way [13]. In turn, the asymmetry in palm size correlates with handedness [14]. Cross-asymmetry has also been observed within the upper and lower limbs, which may indicate that the asymmetrical use of the upper limbs may also impact the asymmetry of the lower limbs in the opposite direction [11]. The research has also shown a significant degree of morphological discrepancy within the pelvis, which indicates the domination of the left side of the lower body; this is in line with the models that describe the influence of right-handedness on the lower body [15]. The directional asymmetry within the lower limbs is less marked, especially in terms of their length; it is, however, visibly marked in terms of the width of diaphysis and epiphysis of the bones [9,16]. The degree of asymmetry is caused by both by the mechanical and genetic factors. Any strain caused by the performed jobs or systematic participating in workout influence the discrepancies in the distribution of morphological features on both sides of the body [17,18]. In the case of the younger competitors in whom epiphyseal closure has not occurred yet, excessive physical strain may cause further discrepancies as well [19]. In sports, the morphological discrepancies of the body sides also depend on the particular discipline that the sportsmen practice. Moreover, in sports, participating in the disciplines that mainly involve a particular side of the body entails asymmetrical changes in certain tissues. These changes are visible especially in soft tissue [20]. The analysis of bilateral differences in javelin throwers has indicated that the asymmetry occurs in the upper limb circumference and is particularly visible in skinfold thickness [21]. The research has also confirmed the significant influence of sports practice on the asymmetry in the distribution of the upper limb muscle mass in young tennis players. In these sportsmen, the muscle mass was far greater in their dominant upper limb if compared to the non-dominant upper limb. Moreover, no significant correlation was found between the age of the sportsmen, the length of their sports practice experience, and the asymmetry coefficients [22]. The research has also shown that the level of asymmetry rises with the sports proficiency of the competitors. In professional field hockey players, both male and female, the research found a significant increase in the muscle mass and in bone mineral density on the left side of the body [23]. In football players, long-term routine physical strain influences the morphological structure of their lower limbs and, as a result, the expansion of the bone mass, the bone cross-sectional area and the thickness of the cortical layer of the bones [24]. The relationship has also been found between the accuracy of marksmen and the increase in their lean mass and the reduction in their fat mass. Moreover, the more efficient marksmen were also characterized by the lesser degree of asymmetry in the lean mass and the strength of their lower limbs [25]. Examination of sportsmen through the DXA method has shown the influence of asymmetry in the lean body mass of the lower limb on the asymmetry of strength and power when jumping [26]. In competitors participating in 100 m runs, a trend to perform better was found in the athletes with more symmetrical structure of their knee joints and ankle joints [27]. The research cited hereinabove shows the multitude of body asymmetries found in the sportsmen from various disciplines; these asymmetries are a result of one-sided strain during sports practice. Int. J. Environ. Res. Public Health 2020, 17, 4695 3 of 11 Though it has not yet been sufficiently described in academic studies, martial arts are potentially an example of a discipline that involves one side of the body over the other. Moreover, this phenomenon should not be present in bodybuilding for it is a discipline that highly emphasizes the balanced modelling of one’s physique. The aim of the study is to assess the influence of the applied fighting techniques and targeted physical effort on the occurrence of asymmetry in body musculature and isometric strength in bodybuilders and competitors of selected martial arts. 2. Materials and Methods The study examined 120 men aged 21.6 2.6 who do sports in academic sports clubs at the major ± universities in Wrocław. The sportsmen belonged to the following disciplines: Judo (J), Brazilian jiu-jitsu (JJ), and the amateur group of natural bodybuilders (BB). The control group (C) consisted of students (n = 30) aged 20.8 2.5 who do not practice any sport. All groups consisted of 30 participants ± each. Variance analysis was used to confirm that there were no significant age differences across the groups. However, statistically significant differences were present in the group members in terms of the length of their sports practice experience (judo 9.9 3.2; ju-jitsu 4.8 1.8; bodybuilding 3.7 2.4). ± ± ± All subjects gave their informed consent for inclusion before they participated in the study. The study was conducted in accordance with the Declaration of Helsinki, and the protocol was approved by the Ethics Committee of the University School of Physical Education in Wrocław, Poland (23.10.12).