Judo is a combat sport that includes attacking or defending by using the 4 limbs (arms, hands, legs, and feet). Particularly in the mental aspect, it has the spirit of martial arts that is explained by Sun Tzu's wisdom words “Flexibility to the system recently, disabled the strong,” (15), and for this reason, it is popular not only in Asia but also throughout the world including Europe, North America, and Africa.
During judo competitions, Judoists score points by throwing their opponents down on the judo mat (pin) using hand, foot and leg, hip and sacrifice techniques (sutemiwaza). Other ways to obtain points are to make their opponent surrender by choking the carotid in the neck, locking the elbow joint (armbars), or holding the opponent's back against the judo mat within a given time (4 minutes for juniors and 5 minutes for adults). To win a judo competition, the Judoists must have strong physical ability (5,9,27) and the skill to perform quick movements after swift judgment. Although physical ability does not fully affect Judoists' judgment, their level of exhaustion does. As match length increases, Judoists become exhausted, which potentially disturbs their swift judgment and subsequently causes decreases in performance.
Judoists' physical factors are largely divided into aerobic and anaerobic systems. The aerobic system is closely related with the ability to recover energy during 10-second rest intervals in between 30-seconds of intermittent fighting in a competition (26) and for recompetition after a competition in a tournament (7). The anaerobic system is necessary for technique manifestation through fast movements and is supplied via energy from the adenosine triphosphate (ATP) and glycolytic systems. It is regarded as an important factor that determines victory or defeat in competitions. Anaerobic power is closely correlated with fat-free mass (FFM) among body compositions (13). Particularly for Judoists who perform within different weight classes, it is considered an indispensable condition for winning competitions to maintain FFM during the training phase and immediately before the competitions (32). However, previous research has not suggested objective data for the association between body composition and its effect on Judoists' anaerobic power and potential to win a competition. In Judoists, moreover, specific knowledge of association between anaerobic power and body composition among performance levels has not yet been concluded.
Therefore, the aim of the current study was to examine the difference in association between the Judoists' body composition and their anaerobic power by performance level. This information could provide Judoists with essential knowledge for training to create a more suitable body composition and potentially become superior Judoists.
Experimental Approach to the Problem
This descriptive, cross-sectional research examined the relationship between body composition and anaerobic power among Korean national team, university varsity team, and junior varsity male Judoists. All subject groups were tested for a difference among groups, used to assess the multiple analysis of covariance (MANCOVA) on the multiple criterion variable measure such as body composition and anaerobic power. From August 2007 through October 2007, body composition and anaerobic power were measured during summer and early autumn seasonal training. As a measurement of body composition, direct segmental multi-frequency body impedance analysis (DSM-BIA) was used to measure body composition at 6:00 am when Judoists woke up. Anaerobic power was also measured by the Judoist performing a 30-second anaerobic power test (Wingate) considered similar to the Tsukuri (positioning) and Kake (execution) phase of Judoists during a match. All Judoists were prohibited from taking ergogenic aids (i.e., caffeine, protein powder, creatine) for 1 month, and water intake was prohibited before the body composition and anaerobic power test.
South Korean male Judoists participated in this study, 10 were from the national team (NT), 26 from the university varsity team (VT), and 28 were from the junior varsity team (JT) (Table 1). Based on their weight, NT and VT Judoists were divided into 6 classes (−60, −66 g, −73, −81, −90, and −100 kg), and the JT judoists were divided into 6 classes (−55, −60, −66, −73, −81, −90 kg) (Table 2). The NT Judoists comprised athletes preparing for the 2008 Beijing Olympics; the VT Judoists were individuals who participated in the 2008 Beijing Olympic trials, and the JT Judoists were individuals who were scheduled to participate in the contest to select athletes for the International Teenage Championship Meet. The distributions of the subjects' height, weight and body composition, skewness, and kurtosis were all ≤|2.0|, so we assumed normal distributions. For selecting suitable participants, the Judoists victory records were considered. For example, the NT Judoists were selected from among Judoists who had won at the 2004 Athens Olympics, the 2005 Cairo World Championship Meet, or the 2006 Doha Asian Games. The VT were Judoists who had won at international competitions such as the 2006 Junior Asian judo championship in Jeju, the 2002 Jeju World Junior Championship Meet, and the 2005 Gwanju Universiade Game. The JT judoists were those who had won a silver medal at the 2006 Santo Domingo World Junior Championship Meet (Table 3). All experimental procedures were approved by the Human Research Ethics Committee of Yongin University, and the subjects gave their written consent to participate in this study.
The body composition measurements were made on subjects when they were undressed and were repeated twice by the DSM-BIA method using In-Body 3.0 (Biospace, Seoul, Korea). This indirect method uses 6 analysis frequencies (1, 5, 50, 250, 500, and 1,000 kHz) and analyzes FFM, muscle mass (MM), total body water (TBW), and fat mass (FM) by using the tetra-polar 8-point tactile electrode method. Although the use of this indirect method on athletes has been reported in recent studies (17,23), we also previously evaluated its validity on male college Judoists (mean ± SD: age = 20.17 ± 1.14 years, weight = 78.67 ± 12.14 kg, and height = 176.85 ± 7.79 cm) by comparing with body fat variables measured by the hydrostatic weighting method (10), resulting in the following equation:
where Y and X represent body fat measured by body impedance analysis and the hydrostatic weighting method, respectively (N = 17, r2 = 0.88, and p < 0.0001).
Wingate 30-second Anaerobic Power Test
Subjects performed a Wingate 30-second anaerobic power test to measure peak and mean anaerobic power, which is considered vital during the tsukuri (positioning) and kake (execution) phase of judo throwing. To test the difference in the Judoists' body composition and anaerobic capacity among the groups and the correlations among variables, we used a computer-aided electrically braked cycle ergometer (Excalibur Sports, Lode B.V., Netherlands). Two weeks before the test, we explained the measuring procedure to the subjects and measured their saddle height and crank length. During the measurement, the subjects warmed up for at least 10 minutes at 60 rpm and 100 W so that their heart rate was maintained at >120-125 b·min−1, and another 5-minute warm-up after 5 minutes' rest (13). In the measurement, a tension of 8.0 N·m was applied, and the entire measuring procedure was controlled by a computer using Lode Wingate Version 1.0.7 (Lode B.V.). In addition, at 5 seconds before the end of warm-up, the computer gave a signal, and the tester made a synchronous oral count and signaled by saying “start” and measured Wingate 30-second anaerobic test. During the warm-up exercise, pedaling was maintained at 60 ± 5 rpm, and tension was applied consistently by means of the computer. During the measurement, strong vocal encouragement was given in an attempt to keep psychological conditions constant.
All data related to the Judoists' body compositions and anaerobic power by group are presented as mean ± SD, and a MANCOVA was performed to test difference among the groups using SPSS 15.0 for Windows (Chicago, IL, USA). A different approach to the analysis of body composition and anaerobic power would be to analyze the biological maturation of the groups, adjustment for age at baseline by ANCOVA. Statistical significance was set at p ≤ 0.05 for all analyses. In addition, Pearson's correlation coefficient was used to test the correlations among body compositions and anaerobic power variables. For all statistical tests, the p level adopted for significance was 2-tailed with p ≤ 0.05.
Multiple analysis of covariance revealed no effect between body composition and anaerobic power in comparison among age. However, as for the difference among the groups, NT judoists' values were significantly greater than those of JT judoists for FFM, MM, and TBW. National team judoists' values were significantly greater than those of VT judoists for MM, whereas VT judoists' values were significantly higher than those of JT judoists for FM (Wilks' Lambda = 1.031, p = 0.045) (Table 4). Absolute value % of body mass for FFM, MM, and FM was significantly different among the groups (Wilks' Lambda = 2.053, p = 0.046) (Table 5).
The difference in anaerobic capacity among the groups, NT and VT, were significantly greater than for JT in peak power (Wilks' Lambda = 6.496, p < 0.001). National team judoists' values were significantly greater than those of VT and JT for mean power, and no significant difference was observed between VT and JT judoists' values (Table 6).
As for the correlations of peak power (Figure 1) and mean power (Figure 2) with FFM, MM, and TBW, NT judoists (intraclass correlation ranged between 0.64 and 0.87, p < 0.05) showed a strong correlation and VT judoists showed a moderate correlation (r = 0.48-0.63, p < 0.05). However, JT judoists showed no statistically significant correlation (r = 0.14-0.24). The correlations among FM, peak power, and mean power were low in all the groups.
Judo is a combat sport that has different weight classes applicable for competition. As in most combat sports, weight classified sport athletes have the tendency of competing in a weight class lower than their natural weight through short-term weight loss for gaining an advantage in the competition. For this reason, weight classified sport athletes have a weight cycle that fluctuates during the season, and therefore, their average weight during the season is lower than that during the off-season. Fat-free mass and MM also decrease around the time of weight loss (8,10,22,28,33). In addition, instructors (i.e., coach, athletic trainer, strength trainer) and athletes apply various scientific methods during the training session and the competition season to prevent the reduction of FFM or MM.
In general, FFM is used to estimate the total skeletal muscle (12,19), and this study gives similar results regarding the Judoists' MM measured by the DSM-BIA method. Both FFM and MM are estimated by the dilution of TBW in vivo (11) and are reported to be closely related with the performance of athletes who should have explosive muscular strength like power athletes (4,14). Judoists also have approximately 30 seconds of intermittent activity during a competition with 10 seconds of rest in between (6,26), and thus, their bodies demand high muscular strength.
In recent studies, the average FFM of male elite Judoists was reported to range from 66.5 to 74.9 kg (19,33), which was similar to our result for the NT Judoists but higher than that of the VT and JT Judoists. In a study conducted by Kubo et al. (19), which used similar participant groups, the mean FFM of the Japanese national team and university varsity team Judoists was higher than that of Korean Judoists. The difference may have come from the difference of the mean weight between the groups; therefore, it is believed that there is no significant difference in FFM between the Judoists of the 2 countries. With regard to MM and TBW, we could not make a direct comparison because there were few previous studies with Judoists' MM and TBW, but this study found that the average MM and TBW required for top level Judoists is 70 kg (SD, 14.25) and 50 L (SD, 7.49), respectively. Based on the levels, we obtained reference data for supplementing the average difference of 8-10% in VT and 18-20% in JT.
Although there was no statistical difference in mean weight between NT and VT judoists in this study, FFM (5.09 kg), MM (7.09 kg), and TBW (3.59 L) showed differences among groups, and these difference came from the difference in body fat. In judo competitions, Judoists with a larger FFM, MM, and TBW have a physical advantage (19). For VT Judoists to become NT Judoists, they need to decrease body fat and increase FFM while maintaining their current weight, and for this, both training and sitology efforts are required. This suggestion is based on the fact that the NT Judoists' percent body fat and the lower limit of its range were approximately 2% lower than that of the VT judoists, and therefore, lightweight Judoists needed to consider the increase of FFM resulting from the loss of body fat. According to early studies, NT Judoists' mean percent body fat ranges from 8.3 to 11.3% (5,9,25,27,33), which is somewhat lower than Korean Judoists' 12.50% (range: 8.8-18.7). Thus, to achieve better results in international competitions, Korean Judoists below the middle weight class need to make more effort to decrease percent body fat and increase FFM. For this reason, in the light-weight class, decrease of FM comes with the decrease of FFM as well. Therefore, Judoists of a light weight should consider regulation between FM and FFM more than those of the heavy weight class. In this study, the JT Judoists' percent body fat met the condition required for being a superior Judoist, but their height, weight, FFM, MM, and TBW needed improvement. Thus, to become a VT or NT Judoist, athletes should continue training, and sitology efforts are required to increase weight, FFM mass, MM, and TBW while maintaining body fat.
As discussed above, Judoists' FFM mass, MM, and TBW, etc., are very important for their judo-specific performance in competitions because they theoretically explain the skeletal MM of the body, which has a substantial effect on the Judoists' physical strength. In a judo competition, Judoists score points by forcing the opponent onto the judo mat forward or backward within a given time. For the Judoists' continuous and repetitive efforts during a very short time frame (intervals of 30-second activity with 10-second rest), anaerobic capacity is regarded as the most important physical condition for effective technique performance (26). From the viewpoint of energetic and exercise physiology, the maximum exertion of strength for 30 seconds and the anaerobic energy contribution ratio is 72% (adenosine [ATP] - phosphocreatine [PC] system: 23%, glycolysis: 49%) (24). Theoretically, this suggests that anaerobic capacity plays a very important role in judoists' activities during a competition. Because the anaerobic energy contribution ratio of 72% is highly dependent on PCr in skeletal muscle, it is directly affected by FFM or MM of body composition (31). Blimkie et al. (2) found that FFM is closely related to the mean (r = 0.85) and peak (r = 0.90) anaerobic power. Peak power is used as an index of maximum strength from muscle. According to recent research on elite judoists, the average range of peak power is 12-14 W·kg−1 (1,17), which is similar to the 14 W·kg−1 average found for our study. Previous research on junior Judoists also reported the average peak power of 11 W·kg−1 (21), which is similar to our results. This shows that South Korean Judoists' muscular strength is similar to that of world class Judoists.
However, as for mean power, which estimates the degree of muscle fatigue after high levels of muscular exertion, the NT Judoists in this study were similar to international elite Judoists, but the VT Judoists were below average compared to what was reported in previous research. Thus, for VT Judoists to become better Judoists, they need to increase anaerobic mean power by increasing FFM or MM. Recently, Aziz et al. (1) quoted by Kim et al. (16) reported that Korean Judoists' peak power and mean power are around 2 W·kg−1 lower on average than the European and North American Judoists', and data from a survey by Ko et al. (18) entitled “Development of Sports Aptitude Diagnosis Model for Finding Talented Athletes” also showed that Korean Judoists' mean power is 2 W·kg−1 lower on average. A possible reason for the difference is that the 2 research studies above measured VT Judoists or club Judoists rather than Judoists representing Korea, and therefore, there were differences within the international Judoists. Moreover, the participants in the research of Kim et al. (16) and Ko et al. (18) were limited to those weighing 66-81 kg, and so this restriction might have caused differences in peak power and mean power.
As for the characteristics of the groups in this study, tendency differences were observed in peak power and mean power among NT, VT, and JT judoists. These significant differences might come from the difference in FFM and MM of body composition. It is believed that there were tendency differences among the groups because FFM and MM contain muscle fibers indispensable for the contraction and recovery of muscle (29). Based on the results of this study, we found that Judoists' FFM and MM are directly correlated with their peak power and mean power and show tendency differences among groups. Fat-free mass and MM showed a very high correlation with peak power and mean power in NT and VT judoists (r = 0.63-0.77, p < 0.05). This suggests that to improve themselves, JT Judoists need to increase FFM and MM. Similar to the results of our research, other research studies on the relationship between body composition and anaerobic performance in wrestlers, Vardar et al. (28) reported that FFM is closely correlated with peak power (r = 0.90) and mean power (r = 0.95) and emphasized the increase of FFM for high anaerobic power.
The major strength of this study includes intensive baseline population, including objective measure of anaerobic power, body composition and confounder, the relatively small sample, the cross-sectional study design, and the short period of follow-up. There are several limitations that need to be considered when interpreting our data. The direct comparison of our results to other studies may need awareness of different criteria to define anaerobic power. We defined anaerobic power by using the Wingate 30-second anaerobic test, but other studies used vertical jump and 50-m sprint run as criteria. Even though the population of this study consists of well-trained Asian men of youth, our findings may not be generalized to groups with different demographics. Another limitation of the present study is that body composition analysis method data were not available. Further studies are warranted to confirm our finding reported here.
In conclusion, the present study found the necessity of increasing the FFM (VT: 5.09 kg, JT: 12.79 kg) and MM (VT: 7.09 kg, JT: 14.47 kg) for university varsity team and junior varsity team Judoists to improve performance. It was reported that there were differences resulting from the gap of anaerobic capacity peak power (VT: 0.62 W·kg−1, JT: 3.04 W·kg−1) and mean power (VT: 0.81 W·kg−1, JT: 1.43 W·kg−1) between groups. These differences very closely correlated with FFM and MM. In judo competitions, attack frequency has a direct influence on victory and defeat. We can predict that VT and JT Judoists will become slower at attack frequency with the passage of time because they have a lower peak power and mean power than do the NT judoists. Therefore, both JT and VT judoists should consider methods to increase FFM, MM, and TBW at the same time. These methods will develop peak power and mean power. In addition, VT judoists should try to maintain their weight while decreasing their FM, and JT judoists should maintain their FM.
From this study in Judoists, we found the importance of FFM, MM, TBW, and anaerobic power as peak power and mean power. Judoists' coaches and athletic trainers are very interested in Judoists' body composition changes during periods of weight loss and training sessions, although they do not know much about changed body composition. Based on this study, FM was lower when Judoists' levels were higher, whereas FFM, MM, and TBW were higher. Therefore, it is recommended that their coaches should consider athletes' body composition cycle with their levels.
We hope that the results of this study may serve as a useful reference for training elite Judoists, and we express our wholehearted thanks to the Judoists of the South Korean national team, Yongin University, Chungbuk Physical Education High School, and Beomgye Middle School, who participated in this study despite their busy training schedules. This work was done using the sports promotion fund from the Korea Institute of Sport Science, Seoul Olympic Sports Promotion Foundation (04/KISS-08-A04004).
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