HOMO - Journal of Comparative Human Biology 66 (2015) 379–386
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Asymmetry in body composition in female hockey players b ´ M. Krzykała a,∗, P. Leszczynski a
University School of Physical Education, Anthropology and Biometry Department, Pozna´ n, Poland Pozna´ n University of Medical Sciences, Department of Physiotherapy, Rheumatology and Rehabilitation, n, Poland Józef Stru´s Municipal Hospital, Pozna´ b
a r t i c l e
i n f o
Article history: Received 11 June 2013 Accepted 8 February 2015
a b s t r a c t The aim of the study was to determine if a sport in which one side of the body is dominant, like field hockey, influences regional body composition and bone mineral density (BMD) distribution in particular body segments, and whether the sporting level is a determining factor. Dual energy X-ray absorptiometry (DXA) method (Lunar Prodigy Advance; General Electric, Madison, USA) with the whole body scan was used to measure bone mineral density, fat mass and lean mass in 31 female field hockey players divided according to their sporting level. The morphological asymmetry level was assessed between two body sides and body segments in athletes from the National Team (n = 17) and from the Youth Team (n = 14) separately and between groups. Bone mineral density in the lower extremity and of the trunk was significantly asymmetric in favor of the left side in the National Team. In the case of the Youth Team, only the trunk BMD indicated clear left–right difference with left side dominance. Both the lean mass and fat mass values were relatively higher on the left side of all body segments and it related to both analyzed groups of athletes. The present study shows that playing field hockey contributes to laterality in body composition and BMD and that the sporting level is a determining factor. In most cases the left side dominated. A greater asymmetry level was observed in more experienced female field hockey players. © 2015 Elsevier GmbH. All rights reserved.
∗ Corresponding author. Tel.: +48 61 835 52 30. E-mail address: [email protected] (M. Krzykała). http://dx.doi.org/10.1016/j.jchb.2015.02.008 0018-442X/© 2015 Elsevier GmbH. All rights reserved.
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Introduction The asymmetry in the human body has been studied for a long time and its many aspects have been of interest to the representatives of many scientific disciplines, e.g. anthropology, physiology, anatomy, neurology and sport. It has been shown that within the internal structure of the body deviations from bilateral symmetry occur and result in asymmetry of internal organs, both paired and unpaired, reflected in differences in their size, shape, position, build and function (Bergman, 1993). Humans are characterized by cross asymmetry which is reflected in greater dimensions of the right upper extremity and – in terms of many dimensions – left lower extremity. This is related to the fact that more frequent use of the upper right (dominant) extremity determines more frequent use of the lower left extremity in order to maintain balance or to use force more effectively, which manifests in greater ´ circumferences of extremities which are more frequently used (Wolanski, 2005). The asymmetry in dimensions of upper and lower extremities was shown in many studies. According to some authors (Munter, 1936; Tomkinson et al., 2003; Ulijaszek and Mascie-Taylor, 2005) upper extremities present a greater morphological asymmetry compared to lower extremities, with dominance of the right side. On average, the right arm and forearm are longer and their circumferences are greater. The left hand is longer and narrower. The right upper extremity is longer by approx. 10 mm compared to the left one. The left foot is longer, and the circumferences of the thigh, lower leg and ankle of the left lower extremity are greater (Malinowski, 2004), as well as the length of the left lower ´ extremity compared to the right one (Singh, 1970; Wolanski, 1962). According to some studies, the development of the right and left body sides is determined by genetic and environmental factors (Al-Eisa et al., 2004; Livshits and Smouse, 1993). Bergman et al. (1962) drew similar conclusions, and according to them a significant part in the development of asymmetry is played by genetics (heredity). However, the asymmetry may increase due to functional factors, e.g. work or training (Bergman et al., 1962). Asymmetry is one of the phenomena which plays a very significant part in sports training, and its smaller or greater extent is determined by factors including the unique nature of a given sports discipline. There are many studies that confirm its existence in this area (Starosta, 1990; Dorado et al., 2002; Auerbach and Ruff, 2006). Some authors have reported that the level of body composition changes according to specific physical activity (Fornetti et al., 1999; Nindl et al., 2000; Greene and Naughton, 2006). It appears that a long-term preference of one extremity, e.g. the left hand and left leg, similar to a permanent tendency to turn in a given direction when rotating round the long body axis, may lead to asymmetry manifested in morphological characteristics, which as a consequence may affect the volume of bone mass in competitive athletes (Starosta, 2008). It has been shown that asymmetry is greater in the dominant extremity due to its more frequent use in the majority of activities performed during the day, which in turn leads to greater bone dimensions in this body segment (Chilibeck et al., 2000). According to Duncan et al. (2002) osteogenic response is related to the type of exercise which could lead to different values of bone mineral density (BMD) at different sites, while strength-based and high-impact sports seem to be associated with higher BMD. Non-weight-bearing sports have, in turn, neutral or negative relationships (Egan et al., 2006). Field hockey is a unilateral sports discipline with heavy demands on the athlete’s physiology (Reilly and Borrie, 1992). Whereas in most sports disciplines it is possible to choose the better limb to perform a movement (such as kicking a ball by a soccer player or an attack by a volleyball player), in field hockey athletes have to adapt themselves to the specific demands of the sport. This one-side dominant sport is characterized by very rigorously specific rules relating to holding the hockey stick and hitting the ball, which has an impact on body posture of the players, which is very unnatural. Moreover, every action with a stick and ball is generally carried out with the body performing a turn to the left (Kerr and Ness, 2006; McLaughlin, 1997). There are limited data concerning the BMD and body composition of female field hockey players (Calo et al., 2009; Sparling et al., 1998; Wassmer and Mookerjee, 2002) and, to our knowledge, no studies examining side-to-side differences in BMD, fat and lean body mass in female hockey players have been carried out.
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The aim of the present paper was to check if one-side dominant sport such as field hockey influences regional body composition and BMD distribution in particular body segments, and whether the sporting level is a determining factor.
Materials and methods The participants of this study were two groups of female field hockey players (n = 31). The first group consisted of 17 members of the Polish National Field Hockey Team (NT) from different regions of Poland, aged 16.1–30.4 years (average age 21.01 years, SD = 3.83); the second group included 14 youth athletes from the Sports School (YT) with a field hockey program in Poznan´ whose age ranged from 16.1 to 18.7 years (average age 17.27 years, SD = 0.85). All athletes were of European origin and healthy. They were all right-handed (determined by their preferred hand in handwriting). The athletes had experience in competing in national and international events. The training sessions in both groups of field hockey players were conducted in accordance with accepted sports training principles appropriate for this sport. The main sports aim for the NT was to participate in the European Championships. Global training and competitive loads included five training sessions a week (1.5 h each, about 9 h per week in total), individual exercise depending on the coach instruction, 1–2 matches per week (about 70 min each). Moreover, the members of the NT trained for 48 days during training camps. The girls from the YT participated in hockey-specific training for approx. 3 h per day and had approx. one match per week, typically at the weekend. Some information, such as the date of birth, menarche age, playing position and history of training were obtained in direct interview when taking body measurements. The female athletes were measured in the afternoon before training, barefooted and in minimal clothing. They were informed about the study procedure and they gave their written consent to participation in the research. All data collection ´ ´ Ethical approval was was conducted during one session, in Hetmanska Medical Center in Poznan. provided by the Bioethics Committee of the University of Medical Sciences and the Polish Field Hockey Association. The physical measurements included body height and body weight. Standing height was measured to the nearest millimeter using an anthropometer (GPM, Switzerland). Body weight was measured to the nearest 0.1 kg with a beam-balance scale (Radwag 150.0C, Poland), according to Martin’s (1928) measurement procedures. Bone mineral density (BMD), lean mass and fat mass were estimated with a dual energy X-ray absorptiometry instrument (Lunar Prodigy Advance; General Electric, Madison, USA) with enCORE software (GE Healthcare v.10.50.086). The whole body scan was used to measure BMD (g/cm2 ), fat tissue (g) and lean mass (g). All participants were measured while wearing standard light shirts to minimize clothing absorption, with all metallic objects removed before the assessment. The calibration was performed before measurement on a phantom, certified by the ISCD (International Society for Clinical Densitometry). Measurements were performed by a trained radiology technician certified by the ISCD. The precision of this method for % fat mass is about 1% according to Lohman (1996), 1% for bone mineral density and 2–3% for total body fat according to other authors (Ellis, 2001; Mattsson and Thomas, 2006). In the laboratory where the measurements were taken, the precision of the densitometer was less than 1% for fat mass. The densitometer is used in clinical trials and it is accredited by external organizations which control designation quality (Synarc, Bio-Imaging). Distribution of all variables was compared to the normal distribution using the Shapiro–Wilk’s test. A value of p ≤ 0.05 was adopted. For BMD, lean mass and fat mass values of mean (M), standard deviation (SD), median (Me), lower and upper quartiles (Q1 , Q4 ) were calculated. The significance of differences in mean values between right and left body segments for variables with normal distribution was checked with Student’s t-test for unpaired data. The significance of differences in mean value between right and left body segments for variables with distribution different from normal was checked with Wilcoxon’s test. Mann–Whitney’s U-test was used to compare the two groups of females in terms of body segments asymmetry. All data were analyzed using the statistical software program Statistica 9.0 version.
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Table 1 Characteristics of Polish female field hockey players with the differences between two groups. Variables
Age (years) Training experience (years) Menarche onset age (years) Body height (m) Body mass (kg)
National Team (n = 17)
Youth Team (n = 14)
p value
M
SD
Min–Max
M
SD
Min–Max
21.01 10.06 12.94 1.68 62.83
3.83 3.67 0.97 0.07 0.07
16.1–30.4 4.0–18.0 12.0–15.0 1.61–1.83 51.4–74.7
17.27 5.39 11.93 1.67 62.45
0.85 2.42 0.83 0.071 10.93
16.1–18.7 1.0–10.0 11.0–14.0 1.56–1.79 62.4–92.1
0.0004 0.0006 0.0012 0.5384 0.6058
n – number of participants; M – mean; SD – standard deviation; Min–Max – minimum–maximum. Numbers in bold – significantly different at p ≤ 0.05.
Results The overall characteristics of the two analyzed groups are presented in Table 1. The National Team competitors were older (M = 21.01 years, SD = 3.83) in comparison with the competitors from the Youth Team, whose age was less diversified with the mean of 17.27 years (SD = 0.85), whereas the difference was statistically significant (p < 0.05). The females from the first group had a longer training experience (M = 10.06 years, SD = 3.67) compared to the second team (M = 5.39 years, SD = 0.42). Also age at menarche differentiated both groups of females (13.18 years, SD = 0.88 and 11.93 years, SD = 0.83, respectively). In both cases the differences were statistically significant. Average body height of the National Team athletes was 1684.0 mm, SD = 65.1 mm and in youth athletes 1667.3 mm, SD = 71.2 mm; there were no statistically significant differences between the analyzed groups in those variables. Both teams had similar average body weight (62.83 kg, SD = 6.67 kg vs. 62.45 kg, SD = 10.93 kg), although the range of this characteristic was very wide. Table 2 shows the results of bone mineral density (BMD), fat mass and lean mass distribution on the right (R) and left (L) body segments in two groups of athletes, according to the sporting level. Side-specific BMD values demonstrated that there were statistically significant differences among the females from the National Team only in BMDlower extremity and BMDtrunk , whereas in the Youth Team only in BMDtrunk. In the case of BMDupper extremity there was only a tendency toward significance in both analyzed groups according to risk of Type II errors (associated with small sample sizes). Comparisons of BMD between athletes of the two sporting levels show that there was no regularity in the distribution of this variable. The NT had significantly lower BMD compared to the females in the YT for both upper extremities, a higher, but not statistically significant level of BMD for both lower extremities and very similar values for L–R trunk and L–R total. Side-specific lean mass analysis shows that significant differences between right and left body segments were noted for upper limbs, trunk and in total in the NT females and at every site in the YT. The NT females had greater lean mass compared to the YT at every site, but the difference was statistically significant only for the right and left lower limbs (p < 0.05). Generally, there were significantly greater values for upper limbs, trunk and in total in the NT on the left body side. The exception was lower extremities which did not differentiate body segments by side. In the case of younger females from the YT there was a clear dominance of the left side in every analyzed variable and the observed differences were statistically significant. Fat massupper extremity , fat masstrunk and fat masstotal had significantly different values for both body sides among the NT females, while in every case the left side dominated here. In the case of the YT, significant differences between each left and right body side also were observed and all values were greater for the left side. In the comparison of fat mass asymmetry according to the sporting level it was observed that generally the YT had a higher level of this component in comparison to the NT females in every segment of the body. At the same time, there were no statistically significant differences between both left sides and right sides between the two analyzed groups of athletes in this variable.
Table 2 Side-specific bone mineral density (BMD), lean mass and fat mass by sport level.
M
p value between sides
SD
Me
Q1
Q4
Youth Team
M
p value between sides SD
Me
Q1
p value between groups
Q4
2
BMD (g/cm ) Left upper extremity Right upper extremity Left lower extremity Right lower extremity Left trunk Right trunk Left total Right total
0.86 0.87 1.39 1.36 1.03 1.00 1.21 1.20
0.046 0.042 0.072 0.065 0.059 0.049 0.052 0.055
0.85 0.86 1.38 1.34 1.04 1.0 1.21 1.19
0.83 0.84 1.35 1.32 1.00 0.98 1.18 1.16
0.89 0.92 1.43 1.40 1.06 1.03 1.24 1.25
0.0537
Lean mass (g) Left upper extremity Right upper extremity Left lower extremity Right lower extremity Left trunk Right trunk Left total Right total
2352.12 2206.12 8045.76 7993.41 10478.18 10080.00 22,474.76 21,875.88
302.530 259.833 763.752 943.181 811.695 721.210 1964.952 1646.425
2388 2161 7963 7989 10542 10122 22,404 21,862
2107 1990 7551 7215 10241 9941 21,681 20,928
2583 2378 8470 8722 10986 10512 23,056 22,571
0.0007
Fat mass (g) Left upper extremity Right upper extremity Left lower extremity Right lower extremity Left trunk Right trunk Left total Right total
762.65 715.71 3092.82 3067.41 3739.12 3599.00 7856.94 7651.35
233.719 229.075 695.645 697.183 1347.111 1286.904 2269.223 2226.239
733 696 3136 3255 4139 3964 8360 8152
585 535 2417 2414 2582 2586 5554 5470
952 884 3611 3476 4676 4568 9682 9254
0.0008
0.0132 0.0033 0.1698
0.1930 0.0006 0.0113
0.2274 0.007 0.0007
0.98 1.01 1.35 1.33 1.01 0.99 1.22 1.21
0.079 0.060 0.088 0.077 0.063 0.058 0.055 0.063
0.99 1.02 1.32 1.31 1.00 0.99 1.21 1.22
0.93 0.98 1.29 1.27 0.97 0.95 1.18 1.15
1.02 1.05 1.39 1.41 1.12 1.02 1.27 1.28
0.0577
2232.07 2106.57 7474.57 7275.50 10069.71 10,069.71 21,587.21 21,138.14
329.266 317.530 947.823 1030.976 1103.984 1103.984 2475.080 2571.736
2150.0 2001.5 7173.0 6978.5 9995.0 9995.0 21,062.5 20,654.0
1989 1923 7048 6732 9330 9330 20,083 19,378
2384 2168 7594 7272 10614 10,614 22,165 21,596
0.0052
782.50 743.21 3442.29 3363.64 4231.00 4117.43 9730.43 8528.50
424.208 422.296 1296.865 1344.194 1966.955 1972.442 3690.452 3665.526
575.0 527.0 3035.0 2981.0 3386.5 3379.5 7133.0 6981.5
481 475 2711 2522 2829 2880 6281 6240
1145 1072 4004 3841 5734 5557 10,760 10,454
0.0076
0.0561 0.0266 0.2965
0.0092 0.0383 0.0219
0.0186 0.0303 0.0012
0.0001 0.0000 0.1970 0.3408 0.5649 0.4158 0.6480 0.6058 0.2579 0.2260 0.0276 0.0182 0.3509 0.6198 0.1036 0.1366 0.5649 0.6624 0.7659 0.9210 0.6480 0.6768 0.7964 0.7964
M. Krzykała, P. Leszczy´ nski / HOMO - Journal of Comparative Human Biology 66 (2015) 379–386
National Team
Numbers in bold – statistically significantly different at p ≤ 0.05.
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Discussion There are different specific kinds of movements in field hockey such as running, turning, twisting, starts, acceleration, stops, many stretching activities and a lot of changes of direction (Anders and Myers, 2008). Many of them involve a rapid rotation of the hips, shoulders and arms (Kerr and Ness, 2006). Some movements start with counter-rotated right side of the body following the left side (with respect to the direction of ball trajectory), which tends to increase energy expenditure (Reilly and Seaton, 1990). There are many high-intensity, intermittent activities that impose heavy demands on the aerobic energy system of a player. Also, the anaerobic system is very important because of brief bursts of high-energy release which are separated by periods of lower intensity (Reilly and Borrie, 1992). The whole body is engaged in this sport activity. The upper extremities are involved in different actions such as hitting and pushing a hockey ball, dribbling or just holding the hockey stick. The lower extremities and trunk are also very loaded during the game, because of unnatural semi-crouched position of athletes and uneven distribution of body weight. Altogether, field hockey could have a great impact on the distribution of tissue components on the left and right sides of the body. Significant differences were observed in site-specific analyzed variables both in the NT and in the YT and they could probably be an adaptive body response caused by physical demands. BMDlower extremity and BMDtrunk were significantly asymmetric in favor of the left side in the NT. BMDupper extremity and BMDtotal which were not significantly asymmetric are the exception. In the case of the YT, only BMDtrunk indicated a clear L–R difference when left side dominated. The values of lean mass were relatively higher on the left side of all body segments and it related to both the NT and the YT for upper extremities (3.2% and 2.9%, respectively), lower extremities (0.3% and 1.3%, respectively), trunk (1.9% and 1.2%, respectively) and total body (1.4% and 1.1%, respectively). For fat mass component the obtained values were also higher on the left body side in both the NT and the YT female athletes for upper extremities (3.2% and 2.6%, respectively), lower extremities (0.4% and 1.2%, respectively), trunk (1.9% and 1.4%, respectively) and finally total body (1.3% and 1.2%, respectively). This is probably related to greater loads on that side during many hours of asymmetric training. Similar observation was previously made of male field hockey players who revealed some muscle hypertrophy on the left side compared to the right side of the body for upper extremities (4.7%), lower extremities (0.8%), trunk (2.5%) and total body (2.3%) (Krzykała, 2010). Interestingly, in the present results greater asymmetry in lean mass and fat mass variables was noted in the younger, less experienced team only for lower extremities. In other cases greater asymmetry level was noted in the NT. The final results are similar to those obtained by Chinn et al. (1974), who concluded that the higher the sporting level, the higher morphological asymmetry in asymmetric sports disciplines. In the case of BMD the tendency was the same in the NT compared to the YT for lower extremities (1.1% and 1.5%, respectively), trunk (1.5% and 1.0%, respectively) and total body (0.4% and 0.4%, respectively). Only the upper extremities were an exception, because there was a right upper extremity advantage in BMD between the groups, but the difference was not statistically significant (0.6% in the NT and 1.5% in the YT). This could be related to the right upper extremity domination in both groups of athletes. Because BMD showed a tendency to be greater in the left lower extremity, trunk and total in both groups of females, it suggests that this side of the body is probably more engaged during some activities such as counterbalancing the rotational torques generated during a swing before hitting the ball or balancing the body on the left side during pushing, or rolling the ball with a forehand on the ground. Similar findings were reported by Calbet et al. (1998), however their results were related to male tennis players. In the present study, a regional hierarchy of BMD accumulation on the left body side in both groups of females was as follows: lower extremity > total > trunk > upper extremity. A very similar situation, but not exactly the same, was noted in the case of the right body side. For the NT it was lower extremity > total > trunk > upper extremity, but the order in the YT was: lower extremity > total > upper extremity > trunk. The other two variables, lean and fat body mass, in both analyzed groups and for both body sides had the same order: total > trunk > lower extremity > upper extremity. It is worth mentioning that physical loads affect specific bones, which have higher BMD than non-weight bearing skeletal regions (Nazarian et al., 2010) and moreover, the BMD remains on a similar level also after the end of the sporting career (Uzunka et al., 2005). Regional body composition
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assessment by dual-energy X-ray absorptiometry in athletes is rather limited, especially in female competitors. This kind of analysis was carried out for example in 10 postmenopausal recreational tennis players, aged 59.7 years, SD = 4.8 years, whose inter-arm asymmetry in bone mineral content and bone area was examined (Sanchis-Moysi et al., 2004). It was shown that former athletes had 8% greater bone mineral content and 7% greater osseous area in the dominant compared to non-dominant arm (p < 0.05). The research indicated that participation in sports leaves a mark on the level of tissue components of the body. The study of Daly et al. (2004) illustrated the increase of lean mass and BMD (6–13%) in the playing arm of 47 female competitive tennis players (8–17 years). This observation, according to the authors, could be a result of direct effect of impact training loads, nutritional and hormonal factors applying to both upper extremities or genetic factors, including body mass. Generally, an athlete’s body reacts in a unique way to a motor stimulus it is subjected to and the size of change depends on the type of activity (the unique nature of a given movement). In symmetric sports the athletes are expected to achieve symmetrical preparation in terms of technical skills and symmetrical body build. According to some authors the best athletes should be more symmetrical, because symmetry positively correlates with sport results (Manning and Pickup, 1998). In asymmetrical sports however, one-sided nature of movement causes specific lateral changes in the body which often increase at higher levels of specialization and which are manifested in different levels of morphological characteristics on the left and right sides on individual body segments. Such observations were done on the example of tennis (Kannus et al., 1994), golf (Dorado et al., 2002) or fencing (Roi and Bianchedi, 2008). In field hockey the demands of discipline connected with a characteristic body posture and asymmetric movements during the game could explain some level of body asymmetry and could be related to adaptation to the asymmetrical mechanical loads in this sport (Krzykała, 2010). Finally, the most important findings of the presented study are that participation in field hockey is linked to body asymmetry manifested in different BMD, fat mass and lean mass values on the left and right body sides in female athletes. The results suggest that asymmetry level increases with the sporting level of athletes. It has been demonstrated that field hockey, as an unilateral sports discipline, increases side-to-side differences which could have a negative implication in the future in terms of an injury rate. These findings, however, should be interpreted with caution because of a limited sample size. Further investigation is needed which would include also other factors which influence side-toside differences and other methods of estimating morphological asymmetry in order to substantiate the obtained results. Furthermore, functional asymmetry assessment should be done together with a questionnaire concerning the injuries. Moreover, it would be interesting to monitor all athletes at short intervals determined by the training cycle to understand better the influence of different unilateral training loads on the level of morphological asymmetry. Acknowledgments The authors wish to thank all players and coaches for their contribution to the study. The study ´ Królowej Jadwigi Street No. was carried out at the University School of Physical Education in Poznan, ´ Poland. 27/39, 61-871 Poznan, References Al-Eisa, E., Egan, D., Wassersug, R., 2004. Fluctuating asymmetry and low back pain. Evol. Hum. Behav. 25, 31–37. Anders, E., Myers, S., 2008. Field Hockey: Steps to Success, 2nd ed. Human Kinetics Publishers, Champaign, IL. Auerbach, B.M., Ruff, C.B., 2006. Limb bone bilateral asymmetry: variability and commonality among modern humans. J. Hum. Evol. 50, 203–218. ´ Bergman, P., Gozdziewski, S., Welon, Z., 1962. Z badan´ nad asymetria˛ ko´sci ramieniowych człowieka. Mater. Prace Antropol. 59. Bergman, P., 1993. Rozwój i przejawy asymetrii u człowieka. In: Jezierski, A., Ogorzałek, A. (Eds.), Symetrie w naukach przyrodniczych, vol. 3. Wrocław “Leopoldinum”. Seria: Seminaria Interdyscyplinarne - Uniwersytet Wrocławski, Studium Generale: t.2. Calbet, J.A.L., Moysi, J.S., Dorado, C., Rodriguez, L.P., 1998. Bone mineral content and density in professional tennis players. Calcif. Tissue Int. 62, 491–496. Calo, C.M., Sanna, S., Piras, I.S., Pavan, P., Vona, G., 2009. Body composition of Italian female hockey players. Biol. Sport 26 (1), 23–31. Chilibeck, P.D., Davison, K.S., Sale, D.G., Webber, C.E., Faulkner, R.A., 2000. Effect of physical activity on bone mineral density assessed by limb dominance across the lifespan. Am. J. Hum. Biol. 12 (5), 633–637.
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HOMO - Journal of Comparative Human Biology journal homepage: www.elsevier.com/locate/jchb
Asymmetry in body composition in female hockey players b ´ M. Krzykała a,∗, P. Leszczynski a
University School of Physical Education, Anthropology and Biometry Department, Pozna´ n, Poland Pozna´ n University of Medical Sciences, Department of Physiotherapy, Rheumatology and Rehabilitation, n, Poland Józef Stru´s Municipal Hospital, Pozna´ b
a r t i c l e
i n f o
Article history: Received 11 June 2013 Accepted 8 February 2015
a b s t r a c t The aim of the study was to determine if a sport in which one side of the body is dominant, like field hockey, influences regional body composition and bone mineral density (BMD) distribution in particular body segments, and whether the sporting level is a determining factor. Dual energy X-ray absorptiometry (DXA) method (Lunar Prodigy Advance; General Electric, Madison, USA) with the whole body scan was used to measure bone mineral density, fat mass and lean mass in 31 female field hockey players divided according to their sporting level. The morphological asymmetry level was assessed between two body sides and body segments in athletes from the National Team (n = 17) and from the Youth Team (n = 14) separately and between groups. Bone mineral density in the lower extremity and of the trunk was significantly asymmetric in favor of the left side in the National Team. In the case of the Youth Team, only the trunk BMD indicated clear left–right difference with left side dominance. Both the lean mass and fat mass values were relatively higher on the left side of all body segments and it related to both analyzed groups of athletes. The present study shows that playing field hockey contributes to laterality in body composition and BMD and that the sporting level is a determining factor. In most cases the left side dominated. A greater asymmetry level was observed in more experienced female field hockey players. © 2015 Elsevier GmbH. All rights reserved.
∗ Corresponding author. Tel.: +48 61 835 52 30. E-mail address: [email protected] (M. Krzykała). http://dx.doi.org/10.1016/j.jchb.2015.02.008 0018-442X/© 2015 Elsevier GmbH. All rights reserved.
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Introduction The asymmetry in the human body has been studied for a long time and its many aspects have been of interest to the representatives of many scientific disciplines, e.g. anthropology, physiology, anatomy, neurology and sport. It has been shown that within the internal structure of the body deviations from bilateral symmetry occur and result in asymmetry of internal organs, both paired and unpaired, reflected in differences in their size, shape, position, build and function (Bergman, 1993). Humans are characterized by cross asymmetry which is reflected in greater dimensions of the right upper extremity and – in terms of many dimensions – left lower extremity. This is related to the fact that more frequent use of the upper right (dominant) extremity determines more frequent use of the lower left extremity in order to maintain balance or to use force more effectively, which manifests in greater ´ circumferences of extremities which are more frequently used (Wolanski, 2005). The asymmetry in dimensions of upper and lower extremities was shown in many studies. According to some authors (Munter, 1936; Tomkinson et al., 2003; Ulijaszek and Mascie-Taylor, 2005) upper extremities present a greater morphological asymmetry compared to lower extremities, with dominance of the right side. On average, the right arm and forearm are longer and their circumferences are greater. The left hand is longer and narrower. The right upper extremity is longer by approx. 10 mm compared to the left one. The left foot is longer, and the circumferences of the thigh, lower leg and ankle of the left lower extremity are greater (Malinowski, 2004), as well as the length of the left lower ´ extremity compared to the right one (Singh, 1970; Wolanski, 1962). According to some studies, the development of the right and left body sides is determined by genetic and environmental factors (Al-Eisa et al., 2004; Livshits and Smouse, 1993). Bergman et al. (1962) drew similar conclusions, and according to them a significant part in the development of asymmetry is played by genetics (heredity). However, the asymmetry may increase due to functional factors, e.g. work or training (Bergman et al., 1962). Asymmetry is one of the phenomena which plays a very significant part in sports training, and its smaller or greater extent is determined by factors including the unique nature of a given sports discipline. There are many studies that confirm its existence in this area (Starosta, 1990; Dorado et al., 2002; Auerbach and Ruff, 2006). Some authors have reported that the level of body composition changes according to specific physical activity (Fornetti et al., 1999; Nindl et al., 2000; Greene and Naughton, 2006). It appears that a long-term preference of one extremity, e.g. the left hand and left leg, similar to a permanent tendency to turn in a given direction when rotating round the long body axis, may lead to asymmetry manifested in morphological characteristics, which as a consequence may affect the volume of bone mass in competitive athletes (Starosta, 2008). It has been shown that asymmetry is greater in the dominant extremity due to its more frequent use in the majority of activities performed during the day, which in turn leads to greater bone dimensions in this body segment (Chilibeck et al., 2000). According to Duncan et al. (2002) osteogenic response is related to the type of exercise which could lead to different values of bone mineral density (BMD) at different sites, while strength-based and high-impact sports seem to be associated with higher BMD. Non-weight-bearing sports have, in turn, neutral or negative relationships (Egan et al., 2006). Field hockey is a unilateral sports discipline with heavy demands on the athlete’s physiology (Reilly and Borrie, 1992). Whereas in most sports disciplines it is possible to choose the better limb to perform a movement (such as kicking a ball by a soccer player or an attack by a volleyball player), in field hockey athletes have to adapt themselves to the specific demands of the sport. This one-side dominant sport is characterized by very rigorously specific rules relating to holding the hockey stick and hitting the ball, which has an impact on body posture of the players, which is very unnatural. Moreover, every action with a stick and ball is generally carried out with the body performing a turn to the left (Kerr and Ness, 2006; McLaughlin, 1997). There are limited data concerning the BMD and body composition of female field hockey players (Calo et al., 2009; Sparling et al., 1998; Wassmer and Mookerjee, 2002) and, to our knowledge, no studies examining side-to-side differences in BMD, fat and lean body mass in female hockey players have been carried out.
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The aim of the present paper was to check if one-side dominant sport such as field hockey influences regional body composition and BMD distribution in particular body segments, and whether the sporting level is a determining factor.
Materials and methods The participants of this study were two groups of female field hockey players (n = 31). The first group consisted of 17 members of the Polish National Field Hockey Team (NT) from different regions of Poland, aged 16.1–30.4 years (average age 21.01 years, SD = 3.83); the second group included 14 youth athletes from the Sports School (YT) with a field hockey program in Poznan´ whose age ranged from 16.1 to 18.7 years (average age 17.27 years, SD = 0.85). All athletes were of European origin and healthy. They were all right-handed (determined by their preferred hand in handwriting). The athletes had experience in competing in national and international events. The training sessions in both groups of field hockey players were conducted in accordance with accepted sports training principles appropriate for this sport. The main sports aim for the NT was to participate in the European Championships. Global training and competitive loads included five training sessions a week (1.5 h each, about 9 h per week in total), individual exercise depending on the coach instruction, 1–2 matches per week (about 70 min each). Moreover, the members of the NT trained for 48 days during training camps. The girls from the YT participated in hockey-specific training for approx. 3 h per day and had approx. one match per week, typically at the weekend. Some information, such as the date of birth, menarche age, playing position and history of training were obtained in direct interview when taking body measurements. The female athletes were measured in the afternoon before training, barefooted and in minimal clothing. They were informed about the study procedure and they gave their written consent to participation in the research. All data collection ´ ´ Ethical approval was was conducted during one session, in Hetmanska Medical Center in Poznan. provided by the Bioethics Committee of the University of Medical Sciences and the Polish Field Hockey Association. The physical measurements included body height and body weight. Standing height was measured to the nearest millimeter using an anthropometer (GPM, Switzerland). Body weight was measured to the nearest 0.1 kg with a beam-balance scale (Radwag 150.0C, Poland), according to Martin’s (1928) measurement procedures. Bone mineral density (BMD), lean mass and fat mass were estimated with a dual energy X-ray absorptiometry instrument (Lunar Prodigy Advance; General Electric, Madison, USA) with enCORE software (GE Healthcare v.10.50.086). The whole body scan was used to measure BMD (g/cm2 ), fat tissue (g) and lean mass (g). All participants were measured while wearing standard light shirts to minimize clothing absorption, with all metallic objects removed before the assessment. The calibration was performed before measurement on a phantom, certified by the ISCD (International Society for Clinical Densitometry). Measurements were performed by a trained radiology technician certified by the ISCD. The precision of this method for % fat mass is about 1% according to Lohman (1996), 1% for bone mineral density and 2–3% for total body fat according to other authors (Ellis, 2001; Mattsson and Thomas, 2006). In the laboratory where the measurements were taken, the precision of the densitometer was less than 1% for fat mass. The densitometer is used in clinical trials and it is accredited by external organizations which control designation quality (Synarc, Bio-Imaging). Distribution of all variables was compared to the normal distribution using the Shapiro–Wilk’s test. A value of p ≤ 0.05 was adopted. For BMD, lean mass and fat mass values of mean (M), standard deviation (SD), median (Me), lower and upper quartiles (Q1 , Q4 ) were calculated. The significance of differences in mean values between right and left body segments for variables with normal distribution was checked with Student’s t-test for unpaired data. The significance of differences in mean value between right and left body segments for variables with distribution different from normal was checked with Wilcoxon’s test. Mann–Whitney’s U-test was used to compare the two groups of females in terms of body segments asymmetry. All data were analyzed using the statistical software program Statistica 9.0 version.
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Table 1 Characteristics of Polish female field hockey players with the differences between two groups. Variables
Age (years) Training experience (years) Menarche onset age (years) Body height (m) Body mass (kg)
National Team (n = 17)
Youth Team (n = 14)
p value
M
SD
Min–Max
M
SD
Min–Max
21.01 10.06 12.94 1.68 62.83
3.83 3.67 0.97 0.07 0.07
16.1–30.4 4.0–18.0 12.0–15.0 1.61–1.83 51.4–74.7
17.27 5.39 11.93 1.67 62.45
0.85 2.42 0.83 0.071 10.93
16.1–18.7 1.0–10.0 11.0–14.0 1.56–1.79 62.4–92.1
0.0004 0.0006 0.0012 0.5384 0.6058
n – number of participants; M – mean; SD – standard deviation; Min–Max – minimum–maximum. Numbers in bold – significantly different at p ≤ 0.05.
Results The overall characteristics of the two analyzed groups are presented in Table 1. The National Team competitors were older (M = 21.01 years, SD = 3.83) in comparison with the competitors from the Youth Team, whose age was less diversified with the mean of 17.27 years (SD = 0.85), whereas the difference was statistically significant (p < 0.05). The females from the first group had a longer training experience (M = 10.06 years, SD = 3.67) compared to the second team (M = 5.39 years, SD = 0.42). Also age at menarche differentiated both groups of females (13.18 years, SD = 0.88 and 11.93 years, SD = 0.83, respectively). In both cases the differences were statistically significant. Average body height of the National Team athletes was 1684.0 mm, SD = 65.1 mm and in youth athletes 1667.3 mm, SD = 71.2 mm; there were no statistically significant differences between the analyzed groups in those variables. Both teams had similar average body weight (62.83 kg, SD = 6.67 kg vs. 62.45 kg, SD = 10.93 kg), although the range of this characteristic was very wide. Table 2 shows the results of bone mineral density (BMD), fat mass and lean mass distribution on the right (R) and left (L) body segments in two groups of athletes, according to the sporting level. Side-specific BMD values demonstrated that there were statistically significant differences among the females from the National Team only in BMDlower extremity and BMDtrunk , whereas in the Youth Team only in BMDtrunk. In the case of BMDupper extremity there was only a tendency toward significance in both analyzed groups according to risk of Type II errors (associated with small sample sizes). Comparisons of BMD between athletes of the two sporting levels show that there was no regularity in the distribution of this variable. The NT had significantly lower BMD compared to the females in the YT for both upper extremities, a higher, but not statistically significant level of BMD for both lower extremities and very similar values for L–R trunk and L–R total. Side-specific lean mass analysis shows that significant differences between right and left body segments were noted for upper limbs, trunk and in total in the NT females and at every site in the YT. The NT females had greater lean mass compared to the YT at every site, but the difference was statistically significant only for the right and left lower limbs (p < 0.05). Generally, there were significantly greater values for upper limbs, trunk and in total in the NT on the left body side. The exception was lower extremities which did not differentiate body segments by side. In the case of younger females from the YT there was a clear dominance of the left side in every analyzed variable and the observed differences were statistically significant. Fat massupper extremity , fat masstrunk and fat masstotal had significantly different values for both body sides among the NT females, while in every case the left side dominated here. In the case of the YT, significant differences between each left and right body side also were observed and all values were greater for the left side. In the comparison of fat mass asymmetry according to the sporting level it was observed that generally the YT had a higher level of this component in comparison to the NT females in every segment of the body. At the same time, there were no statistically significant differences between both left sides and right sides between the two analyzed groups of athletes in this variable.
Table 2 Side-specific bone mineral density (BMD), lean mass and fat mass by sport level.
M
p value between sides
SD
Me
Q1
Q4
Youth Team
M
p value between sides SD
Me
Q1
p value between groups
Q4
2
BMD (g/cm ) Left upper extremity Right upper extremity Left lower extremity Right lower extremity Left trunk Right trunk Left total Right total
0.86 0.87 1.39 1.36 1.03 1.00 1.21 1.20
0.046 0.042 0.072 0.065 0.059 0.049 0.052 0.055
0.85 0.86 1.38 1.34 1.04 1.0 1.21 1.19
0.83 0.84 1.35 1.32 1.00 0.98 1.18 1.16
0.89 0.92 1.43 1.40 1.06 1.03 1.24 1.25
0.0537
Lean mass (g) Left upper extremity Right upper extremity Left lower extremity Right lower extremity Left trunk Right trunk Left total Right total
2352.12 2206.12 8045.76 7993.41 10478.18 10080.00 22,474.76 21,875.88
302.530 259.833 763.752 943.181 811.695 721.210 1964.952 1646.425
2388 2161 7963 7989 10542 10122 22,404 21,862
2107 1990 7551 7215 10241 9941 21,681 20,928
2583 2378 8470 8722 10986 10512 23,056 22,571
0.0007
Fat mass (g) Left upper extremity Right upper extremity Left lower extremity Right lower extremity Left trunk Right trunk Left total Right total
762.65 715.71 3092.82 3067.41 3739.12 3599.00 7856.94 7651.35
233.719 229.075 695.645 697.183 1347.111 1286.904 2269.223 2226.239
733 696 3136 3255 4139 3964 8360 8152
585 535 2417 2414 2582 2586 5554 5470
952 884 3611 3476 4676 4568 9682 9254
0.0008
0.0132 0.0033 0.1698
0.1930 0.0006 0.0113
0.2274 0.007 0.0007
0.98 1.01 1.35 1.33 1.01 0.99 1.22 1.21
0.079 0.060 0.088 0.077 0.063 0.058 0.055 0.063
0.99 1.02 1.32 1.31 1.00 0.99 1.21 1.22
0.93 0.98 1.29 1.27 0.97 0.95 1.18 1.15
1.02 1.05 1.39 1.41 1.12 1.02 1.27 1.28
0.0577
2232.07 2106.57 7474.57 7275.50 10069.71 10,069.71 21,587.21 21,138.14
329.266 317.530 947.823 1030.976 1103.984 1103.984 2475.080 2571.736
2150.0 2001.5 7173.0 6978.5 9995.0 9995.0 21,062.5 20,654.0
1989 1923 7048 6732 9330 9330 20,083 19,378
2384 2168 7594 7272 10614 10,614 22,165 21,596
0.0052
782.50 743.21 3442.29 3363.64 4231.00 4117.43 9730.43 8528.50
424.208 422.296 1296.865 1344.194 1966.955 1972.442 3690.452 3665.526
575.0 527.0 3035.0 2981.0 3386.5 3379.5 7133.0 6981.5
481 475 2711 2522 2829 2880 6281 6240
1145 1072 4004 3841 5734 5557 10,760 10,454
0.0076
0.0561 0.0266 0.2965
0.0092 0.0383 0.0219
0.0186 0.0303 0.0012
0.0001 0.0000 0.1970 0.3408 0.5649 0.4158 0.6480 0.6058 0.2579 0.2260 0.0276 0.0182 0.3509 0.6198 0.1036 0.1366 0.5649 0.6624 0.7659 0.9210 0.6480 0.6768 0.7964 0.7964
M. Krzykała, P. Leszczy´ nski / HOMO - Journal of Comparative Human Biology 66 (2015) 379–386
National Team
Numbers in bold – statistically significantly different at p ≤ 0.05.
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Discussion There are different specific kinds of movements in field hockey such as running, turning, twisting, starts, acceleration, stops, many stretching activities and a lot of changes of direction (Anders and Myers, 2008). Many of them involve a rapid rotation of the hips, shoulders and arms (Kerr and Ness, 2006). Some movements start with counter-rotated right side of the body following the left side (with respect to the direction of ball trajectory), which tends to increase energy expenditure (Reilly and Seaton, 1990). There are many high-intensity, intermittent activities that impose heavy demands on the aerobic energy system of a player. Also, the anaerobic system is very important because of brief bursts of high-energy release which are separated by periods of lower intensity (Reilly and Borrie, 1992). The whole body is engaged in this sport activity. The upper extremities are involved in different actions such as hitting and pushing a hockey ball, dribbling or just holding the hockey stick. The lower extremities and trunk are also very loaded during the game, because of unnatural semi-crouched position of athletes and uneven distribution of body weight. Altogether, field hockey could have a great impact on the distribution of tissue components on the left and right sides of the body. Significant differences were observed in site-specific analyzed variables both in the NT and in the YT and they could probably be an adaptive body response caused by physical demands. BMDlower extremity and BMDtrunk were significantly asymmetric in favor of the left side in the NT. BMDupper extremity and BMDtotal which were not significantly asymmetric are the exception. In the case of the YT, only BMDtrunk indicated a clear L–R difference when left side dominated. The values of lean mass were relatively higher on the left side of all body segments and it related to both the NT and the YT for upper extremities (3.2% and 2.9%, respectively), lower extremities (0.3% and 1.3%, respectively), trunk (1.9% and 1.2%, respectively) and total body (1.4% and 1.1%, respectively). For fat mass component the obtained values were also higher on the left body side in both the NT and the YT female athletes for upper extremities (3.2% and 2.6%, respectively), lower extremities (0.4% and 1.2%, respectively), trunk (1.9% and 1.4%, respectively) and finally total body (1.3% and 1.2%, respectively). This is probably related to greater loads on that side during many hours of asymmetric training. Similar observation was previously made of male field hockey players who revealed some muscle hypertrophy on the left side compared to the right side of the body for upper extremities (4.7%), lower extremities (0.8%), trunk (2.5%) and total body (2.3%) (Krzykała, 2010). Interestingly, in the present results greater asymmetry in lean mass and fat mass variables was noted in the younger, less experienced team only for lower extremities. In other cases greater asymmetry level was noted in the NT. The final results are similar to those obtained by Chinn et al. (1974), who concluded that the higher the sporting level, the higher morphological asymmetry in asymmetric sports disciplines. In the case of BMD the tendency was the same in the NT compared to the YT for lower extremities (1.1% and 1.5%, respectively), trunk (1.5% and 1.0%, respectively) and total body (0.4% and 0.4%, respectively). Only the upper extremities were an exception, because there was a right upper extremity advantage in BMD between the groups, but the difference was not statistically significant (0.6% in the NT and 1.5% in the YT). This could be related to the right upper extremity domination in both groups of athletes. Because BMD showed a tendency to be greater in the left lower extremity, trunk and total in both groups of females, it suggests that this side of the body is probably more engaged during some activities such as counterbalancing the rotational torques generated during a swing before hitting the ball or balancing the body on the left side during pushing, or rolling the ball with a forehand on the ground. Similar findings were reported by Calbet et al. (1998), however their results were related to male tennis players. In the present study, a regional hierarchy of BMD accumulation on the left body side in both groups of females was as follows: lower extremity > total > trunk > upper extremity. A very similar situation, but not exactly the same, was noted in the case of the right body side. For the NT it was lower extremity > total > trunk > upper extremity, but the order in the YT was: lower extremity > total > upper extremity > trunk. The other two variables, lean and fat body mass, in both analyzed groups and for both body sides had the same order: total > trunk > lower extremity > upper extremity. It is worth mentioning that physical loads affect specific bones, which have higher BMD than non-weight bearing skeletal regions (Nazarian et al., 2010) and moreover, the BMD remains on a similar level also after the end of the sporting career (Uzunka et al., 2005). Regional body composition
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assessment by dual-energy X-ray absorptiometry in athletes is rather limited, especially in female competitors. This kind of analysis was carried out for example in 10 postmenopausal recreational tennis players, aged 59.7 years, SD = 4.8 years, whose inter-arm asymmetry in bone mineral content and bone area was examined (Sanchis-Moysi et al., 2004). It was shown that former athletes had 8% greater bone mineral content and 7% greater osseous area in the dominant compared to non-dominant arm (p < 0.05). The research indicated that participation in sports leaves a mark on the level of tissue components of the body. The study of Daly et al. (2004) illustrated the increase of lean mass and BMD (6–13%) in the playing arm of 47 female competitive tennis players (8–17 years). This observation, according to the authors, could be a result of direct effect of impact training loads, nutritional and hormonal factors applying to both upper extremities or genetic factors, including body mass. Generally, an athlete’s body reacts in a unique way to a motor stimulus it is subjected to and the size of change depends on the type of activity (the unique nature of a given movement). In symmetric sports the athletes are expected to achieve symmetrical preparation in terms of technical skills and symmetrical body build. According to some authors the best athletes should be more symmetrical, because symmetry positively correlates with sport results (Manning and Pickup, 1998). In asymmetrical sports however, one-sided nature of movement causes specific lateral changes in the body which often increase at higher levels of specialization and which are manifested in different levels of morphological characteristics on the left and right sides on individual body segments. Such observations were done on the example of tennis (Kannus et al., 1994), golf (Dorado et al., 2002) or fencing (Roi and Bianchedi, 2008). In field hockey the demands of discipline connected with a characteristic body posture and asymmetric movements during the game could explain some level of body asymmetry and could be related to adaptation to the asymmetrical mechanical loads in this sport (Krzykała, 2010). Finally, the most important findings of the presented study are that participation in field hockey is linked to body asymmetry manifested in different BMD, fat mass and lean mass values on the left and right body sides in female athletes. The results suggest that asymmetry level increases with the sporting level of athletes. It has been demonstrated that field hockey, as an unilateral sports discipline, increases side-to-side differences which could have a negative implication in the future in terms of an injury rate. These findings, however, should be interpreted with caution because of a limited sample size. Further investigation is needed which would include also other factors which influence side-toside differences and other methods of estimating morphological asymmetry in order to substantiate the obtained results. Furthermore, functional asymmetry assessment should be done together with a questionnaire concerning the injuries. Moreover, it would be interesting to monitor all athletes at short intervals determined by the training cycle to understand better the influence of different unilateral training loads on the level of morphological asymmetry. Acknowledgments The authors wish to thank all players and coaches for their contribution to the study. The study ´ Królowej Jadwigi Street No. was carried out at the University School of Physical Education in Poznan, ´ Poland. 27/39, 61-871 Poznan, References Al-Eisa, E., Egan, D., Wassersug, R., 2004. Fluctuating asymmetry and low back pain. Evol. Hum. Behav. 25, 31–37. Anders, E., Myers, S., 2008. Field Hockey: Steps to Success, 2nd ed. Human Kinetics Publishers, Champaign, IL. Auerbach, B.M., Ruff, C.B., 2006. Limb bone bilateral asymmetry: variability and commonality among modern humans. J. Hum. Evol. 50, 203–218. ´ Bergman, P., Gozdziewski, S., Welon, Z., 1962. Z badan´ nad asymetria˛ ko´sci ramieniowych człowieka. Mater. Prace Antropol. 59. Bergman, P., 1993. Rozwój i przejawy asymetrii u człowieka. In: Jezierski, A., Ogorzałek, A. (Eds.), Symetrie w naukach przyrodniczych, vol. 3. Wrocław “Leopoldinum”. Seria: Seminaria Interdyscyplinarne - Uniwersytet Wrocławski, Studium Generale: t.2. Calbet, J.A.L., Moysi, J.S., Dorado, C., Rodriguez, L.P., 1998. Bone mineral content and density in professional tennis players. Calcif. Tissue Int. 62, 491–496. Calo, C.M., Sanna, S., Piras, I.S., Pavan, P., Vona, G., 2009. Body composition of Italian female hockey players. Biol. Sport 26 (1), 23–31. Chilibeck, P.D., Davison, K.S., Sale, D.G., Webber, C.E., Faulkner, R.A., 2000. Effect of physical activity on bone mineral density assessed by limb dominance across the lifespan. Am. J. Hum. Biol. 12 (5), 633–637.
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