Taekwondo is a native Korean fighting art that originated thousands of years ago and has become a popular sport with over 120 million children and adults participating worldwide (4). The sport of taekwondo became an Olympic event in 2000 at the Sydney games and is characterized by high-intensity anaerobic activity interspersed with submaximal aerobic work (14,34). Taekwondo is a full contact free-sparring sport that awards points for body and head contact resulting in an increased incidence of head injuries compared to other sports (17). Taekwondo in the Olympics consists of 3× 2-minute rounds with a 1-minute rest period between each round. Points are scored in taekwondo competition via punches and kicks to the torso and kicks to the head. Matches can be won via knockout or via points.
Because of the emphasis on kicks in taekwondo, it requires athletes to have highly explosive leg power, aerobic endurance, and flexibility (14,20). The ability of taekwondo athletes to rapidly generate muscle force through kicks is imperative because 80% of the taekwondo skills are related to kicking (30). This necessitates that a large emphasis be placed on lower leg power generation in strength training activities. In previous studies on combat sports, lower leg power has been assessed through the use of a 30-second Wingate or assessment of anaerobic thresholds on a cycle ergometer (14,20,33). Because these methods lack mechanical specificity to taekwondo, a more specific indication of lower leg power may come through the assessment of jumping activities that have been used in the aforementioned papers; however, only height jump has been recorded (14,20,33). Recent developments in technology have seen the use of linear encoder systems to assess power, velocity, and acceleration during such movements, and thus, this technology may provide a more specific power profile of an athlete (6,13). Improvements in power as a result of an intervention mesocycle have been studied previously showing that weightlifting movements and combinations of heavy and light load power training is best for improvements (10,12,18,26). These reviews and studies did not consider fluctuations in power throughout the course of a training intervention and only considered a pre–post power increase.
The profiling of combat sport athletes has been performed at one discrete time point providing a snapshot of the anthropometrical, nutritional, and physiological make-up of the athletes (1,14,20). Although useful, the profile is then dependent on which point in the training macrocycle the tested athlete resides. No studies have presented profiling data of Olympic combat sport athletes in the lead up to Olympic competition nor have tracked variables during a mesocycle before Olympic Competition. Information on physical and anthropometrical profiles of elite level athletes is of benefit because more successful athletes have been shown to possess better physiological characteristics compared to nonelite athletes (20). Although these characteristics are not the only determinants of success, they do serve to provide a strength coach with a reference physique and may aid in the development of strength and conditioning programs to optimize athlete potential. The aim of this study is to identify the anthropometrical and physiological profiles of an Olympic taekwondo team and to track the power profile of these athletes in the 9 weeks before Olympic departure.
Experimental Approach to the Problem
This study is a retrospective analysis on 4 Olympic Taekwondo Athletes in the 9 weeks before the August 2008 Beijing Olympics (May–July 2008). Subjects gave informed consent to be tested and strength trained while on residence at the Australian Institute of Sport. At the start of the 9 weeks fitness, data including anthropometrics and fitness test data were documented. Over the subsequent 9-week period, an unweighted double-leg and single-leg squat jumps were tracked for power, velocity, and acceleration variables in addition to jump height using a linear encoder system. Results were reported on the weekly progress of the athlete's power production throughout the 9-week period. This was a nonintervention study and did not impact on the normal preparation of the athletes by the coaches and strength and conditioning team. All subjects took part in testing on the same point in their programs, and were tracked at the same time each week. Independent variables related to the tests administered to the athlete; dependent variables were the aerobic, anaerobic, and anthropometrical measures during the profiling and the power, velocity, and acceleration measures during the monitoring up to Olympic departure.
The subjects consisted of 4 taekwondo athletes (2 male; 2 female) selected to represent Australia in Taekwondo at the August 2008 Beijing Olympic games (age: 23.3 ± 1.7 years; height: 1.74.1 ± 0.02 m; mass: 67±4.1 kg). The female athletes competed in the 67+ kg heavyweight category and the 67-kg welterweight category; the male athletes competed in the flyweight (58 kg) and featherweight (68 kg) category. The subjects in this study were regarded as 1 group to assess the profile of the Olympic squad. Previous papers have pooled the athletes or split them by gender (1,2,17,20,27,33). Because of the low subject numbers, we decided to pool the athletes for analysis. All subjects had >1-year strength training history when selected for the Olympic team.
Duration and Frequency of Testing
This retrospective analysis uses the data from the testing of the athletes in the 9 weeks before embarking for Olympic competition. All testing and strength training took place at the Australian Institute of Sport strength and conditioning facility under the guidance of an accredited strength and conditioning coach. The first testing session took place in May 2008. Before this date, the subjects were part of a larger 9-person squad.
The first focus of the paper looks at the group anthropometric and physiological profiles of these athletes after Olympic selection. The second focus of the paper tracks the athlete's weekly progress on 2 of the power-based tests up to Olympic departure. The frequency of analysis was broken down into 2 parts. Part 1 was collected immediately after Olympic selection. These were discrete measures and not collected subsequently. Part 2 relates to the constant recording of unweighted single-leg and double-leg squat jumps. These measures were recorded weekly up until Olympic departure in August 2008.
Part 1: Anthropometric Measurements and Fitness Testing
Body mass (kg), body height (m), and 7 site skinfolds (mm) were measured from each athlete. These measurements were incorporated into a formula to calculate the lean mass index (LMI ). The LMI provides an indication of the lean mass the athlete possesses adjusted for changes in skinfold thickness and is measured in mm per kg (31). The equation for the LMI is M/Sx, where M is the total mass, S is the skinfold thickness, and x is the fat mass as a fraction of the total mass. Rugby players have been shown to have an LMI of 53.1 mm·kg (15); however, no LMI guidelines for combat sports have been provided. Skinfolds were measured with Harpenden calipers (Baty International, West Sussex, United Kingdom) from the triceps, subscapular, biceps, supraspinale, abdominal, front thigh and calf according to the International society for the Advancement of Kinanthropometry guidelines.
All strength tests were conducted in accordance with the National Sports Science Quality Assurance Scheme National Protocols. In the bench press, bench pull, and squat, athletes specified their personal 3 repetition maximum (3RM) load from training experience. After an appropriate warm-up of 90% of 3RM lifted in training, athletes were instructed to lift the load for 3 repetitions. Repetitions were performed in a continuous manner, and not more than 2 seconds was allowed between reps. A minimum of 2.5-kg weight increments were used between each trial. A maximum of 5 minutes was allowed between trials. The 3RM was found within 4 trials and deemed to be reached once either 3 repetitions were unable to be completed or the technique had failed on the judgment of the strength coach. Using the individual's body mass on the date of testing, the relative upper body and lower body strength measurements were then calculated.
A multistage shuttle test (19) was used to calculate maximal oxygen uptake (O2max). Physical work capacity (PWC/75%) was performed using a submaximal ergometer bike test (LODE) and a telemetered heart rate monitor (Polar Electro RS400, Pursuit Performance, Adelaide, Australia). Athletes cycled for 3 workloads at 100–110, 115–130, and 130–145 b·min−1 with loads and cadence recorded at each heart rate. Athletes cycled for 3 minutes at each workload until a steady-state heart rate was found. Each steady-state heart rate and workload were then graphed with the line of best fit for the 3 points extrapolated to estimate the workload that would elicit 75% of the maximum heart rate. This was done on a bike to allow for those athletes who were unable to run because of injury and who still needed capacity assessment.
Lower body power was assessed bilaterally using a countermovement jump test using Gymaware (Kinetic, Canberra, Australia) and unilaterally using single-leg countermovement squat jumps. Speed was assessed using a 20-m sprint test, from self-selected stationary start and measured using wireless infrared timing lights (Speedlight timing gate system, SWIFT, Queensland, Australia). The results for these fitness sessions were taken as the last available test battery. Because of injuries of the athletes, some of the test data dated back to February 2008.
Part 2: Power Assessment and Monitoring
Power analysis of the single-leg squat jumps and the unweighted squat jumps were collected each week over the course of the 9-week program (S1 = testing session 1; S2 = testing session 2, etc.). The power, velocity, and acceleration variables for the concentric portion of the exercises were recorded using the Gymaware optical encoding system (Kinetic) with the linear position transducer being attached to the right side of a wooden dowel rod and placed on the upper portion of the scapula region of the athletes back. The bar was maintained in contact with the body at this position by the athlete placing the hands on the bar and pulling it into their body. The retraction tension of the linear position transducer was 5 N, which was adjusted for calculating peak power, velocity, and acceleration. Displacement time data was sampled at 29 kHz and downsampled to 50 Hz where position points were time stamped when a change in position was detected, with time between samples limited to a minimum of 20 milliseconds (www.kinetic.com.au) (29).
The first and second derivates of position with respect to time was taken to calculate instantaneous velocity and acceleration, respectively. Acceleration values were multiplied by the system mass to calculate force, and the given force curve multiplied by the velocity curve to determine power. Peak power and mean power (W), peak velocity and mean velocity (m·s−1) and peak and mean acceleration (m·s2) were calculated. Peak power was allometrically scaled using the equation Pn = P/S b where Pn is the allometrically scaled power, P is the absolute power, S is the index of body size, in this case body mass, and b is the allometric exponent which was 0.67 (24). Height of the jumps (m) was also recorded. This system and it calculation methods have been used previously to assess reliability and validity of parameters during countermovement jumps using similar methodologies (9,16).
Pre-Olympic Conditioning Program
The group undertook 3× strength sessions per week with a high priority on acceleration at the start of each session and core stability work conducted at the end of each session. A 1× group conditioning session was also implemented per week consisting of repeated sprint work over distances of 5–100 m with an 1,800- to 2,200-m total load during the session. In addition, the athletes did 5 taekwondo skills based sessions per week (∼3 h·d−1) and had 3 recovery sessions per week (hydrotherapy and sports massage).
All athletes followed a periodized strength training programs whereby intensity was undulated until the Olympic Games. Intensity level was either medium or high throughout these 9 weeks. The first 3 weeks of the program consisted of 60% strength, 25% power, and 15% other biomotor abilities. The main focus here was to increase volume in addition to increasing strength and power. Three to five sets of 2–5 reps were prescribed based on using 5 major lifts (Power cleans; Squats; Stiff legged deadlifts; Bench Pull; Bench Press). In the following 6 weeks, the sessions were broken down to be dedicated to 50% strength based exercises, 40% power based exercises, and 10% to specific drills. The main goal of these sessions was to increase power and train for maximum strength. Three to five sets of 2–5 repetitions were implemented based on the aforementioned 5 major lifts in addition to sessions incorporating plyometric exercises. Uncoached sessions were continued upon arrival in Beijing and tapered down up to 2 days before competition; however, no physiological performance data were collected for this period.
All descriptive statistics were calculated using PASW statistics 17 package. Coefficients of variation (CVs %) were used to assess the intrasubject reliability of the concentric peak power from the single-leg squat jumps and unweighted squat jumps. Concentric peak power for single-leg squat jumps (right leg) showed a 4% CV, single-leg squat jumps (left leg) showed a 6% CV and unweighted squat jumps showed a 3% CV. The results within the tables are reported as means and SDs. Percentage change statistics between each session for each variable were also calculated in addition to percentage difference values between left- and right-leg single-leg squat jumps. Because of the small numbers of athletes, further statistical analysis was not performed.
Part 1: Anthropometric Measurements and Fitness Testing Profiles
Body composition and LMI scores are shown in Table 1 and indicate large ranges in the sum of skinfolds, triceps, front thigh and calf skinfolds. Table 2 depicts the fitness test profile of the athletes. Aerobic performance depicted a variation among the group with the lowest O2max (46.1 ml·min−1·kg−1) and bleep test score (Level 9.02) occurring in the female athlete in the heavyweight division and the highest scores from the male in the flyweight category (O2max 59.84 ml·min−1·kg−1; bleep test: Level 13.03). A small variation in the PWC of the athletes was recorded. Right-leg dominance was shown in the single-leg jumps, and as expected, the lower relative strength measure is greater than the upper body measure. In the upper body strength movements, the bench pull is shown to be greater than the bench push. A power loading profile from the bench throw showed that optimal power occurred at 35 kg where 4.35 W·kg was exerted (Figure 1).
Part 2: Power Assessment and Monitoring
Tables 3–7 show the absolute and percentage change variables in the 8 testing sessions. Training load indicators (H = heavy, M = moderate, and U = unloading) for the week leading up to testing are shown in each table.
Table 3 shows the absolute values for the selected variables during a single-leg squat jump for both the left and right legs. Table 4 shows the percentage change in these variables across the course of the 8 sessions leading up to the Olympics. Overall increases in peak (<23.49%) and mean (<15.15%) power for both left and right legs occur from session 1 to session 8 testing. Undulations in peak and mean power occur across the 9-week cycle with decreases in power occurring in sessions 5–7 for the right leg in all 4 athletes. Minimal imbalances in power between the left and right legs are evident for each variable with the single-leg jump on the right leg being 0.05 m greater than on the left (Table 5). Power, velocity and acceleration variables displayed a minimal difference (<5%) between legs, apart from the allometrically scaled values that indicated a 14% difference between legs had developed.
Unweighted Squat Jumps
Table 6 shows the absolute values for the selected variables during an unweighted squat jump. Table 7 shows the percentage change in these variables across the course of the 8 testing sessions leading up to the Olympics. From session 1 to session 8, increases in all variables are shown. In particular, a 12.9% increase in peak power and a 9.54% increase in mean power are shown between sessions 1 and 8. When allometrically scaling these values, these percentage increases changed to 14.49 and 9.34%, respectively.
The athletes in this study were selected for the Olympic squad on the basis of their physical, technical, and performance-based skills. This study documents the physical qualities of the athletes and presents the first paper to track variables across the course of a pre-Olympic training phase. All athletes in this study successfully competed in the Beijing August 2008 Olympics. All athletes won at least 1 bout at the games with the highest placed athlete competing in the repechage.
The mean anthropometrical measurements of the Australian Olympic quartet show a large sum of skinfolds range. The stature and mass of this group of athletes were greater than other taekwondo Olympic squad profiles of height and weight for Check Republic and Croatia (14,20) but not as much as the average mass and stature of the taekwondo athletes competing at the 2000 Olympic games (17). The LMI has only been used previously with rugby players showing an average value of 53.1 mm·kg−1 (15), the mean LMI shown in this study (37.1 mm·kg−1) is expected to be lower as taekwondo requires a more lean body mass because of weight categories within taekwondo competition being adhered to. The sum of skinfolds (75.6 mm) is much higher than that shown in kung fu athletes of 49.7 mm (1); however, this study used a 7 skinfold sum on 4 athletes, whereas the kung fu athletes had a 4-site sum of skinfolds on 14 athletes; furthermore, the range of skinfold thickness in Artioli's (1) study was 19–79.2 mm for men and women combined, which does compare to the values in this study.
The fitness tests revealed a similar work capacity to judo athletes (2.1 W·kg−1) (33) however lower than other male and female taekwondo athletes (3.1 W·kg−1) (14). The athletes in this study did have higher O2max scores (53.29 ml·min−1·kg−1) compared to values of other taekwondo athletes (47.25 ml·min−1·kg−1) (14), 36.45 ml·min−1·kg−1 (27) indicating that the athletes had a good aerobic base going into the Olympic training power mesocycle. Heller et al. (14) indicated that a good aerobic capacity was an important trait of elite-level taekwondo athletes, although a direct link to taekwondo performance is yet to be determined. No data are available to compare the 20-m sprint performance with other combat sport athletes; however, the times recorded in this study are comparable to those of physically active men (3.1–3.4 seconds) (22) and slower than a mixed-gender group of track and field athletes (3.17 seconds) (25).
Explosive power in lower limbs may be of paramount importance in elite taekwondo because it facilitates jump kicks and contributes to more powerful standing and airborne kicks (14,28,32). Furthermore, Yiau et al. (37) found that winning Malaysian female taekwondo athletes jumped higher than the less successful athletes. The results of this study show fluctuations in all power variables across the 9 weeks leading up to Olympic departure; however, the power with reference to body weight is high indicating a good power-to-weight ratio. This is expected because of the intensity of the training weeks shown and the competition. The highest peak power values were shown in the unloading week possibly because of the reduced effects of fatigue and also the conjugated effect of the previous 3 weeks' training. This agrees with the findings of previous literature wherein a reduced volume equates to greater power in tests (3). Intensive training usually suppresses power production with these levels being shown to return or super compensate during a taper or unloading cycle. The mechanisms responsible for this may have been related to enzymatic and type II muscle fiber size growth characteristics (23) and increases in contractile velocity of both type I and type II muscle fibers (35). Because of the small reduction in body mass across the 9 weeks in this study, these changes in muscle power may also be attributable to other factors such as improved coordination through neural firing and more efficient recruitment of muscle fibers as a result of the training (11).
This study showed that the power profiles increased from the first testing session to the last when following the prescribed strength and conditioning program. This is in line with previous research where a combination program of high force and high power exercises is best to increase power overall compared to solely power exercises alone (12,17). Even though the level of these athletes is greater than those of previous studies, it has been shown that the combination program implemented has served to further enhance the neuromuscular pathways, possibly via shifts in the force–velocity curve and quantitative changes of neuronal input to the muscle although this is unconfirmed (8). More specifically, the strength programs adopted incorporated the major weightlifting movements and strength exercises of varying loads, therefore, emphasizing the speed and strength elements of the power development equation. A combination of heavy and light load training has been shown to be preferable in power development compared to isolated heavy load or light load power training (6,7,10,26).
The 9-week training mesocycle under assessment focused on power development opposed to seeing instant benefits. Despite this study showing considerable increases in power in the short term, the conjugated long-term effects of this power cycle may have come from the taper program implemented after departure. Increased strength and power as a result of a taper has been commonly shown in different events such as swimming (35) and cycling (21). However, these require different metabolic demands and power requirements compared to combat sports; thus, investigation into tapering in combat sports is an area for future research. Greater power outputs for both single-leg and double-leg jumps were shown in weeks 2–5. This could be related to the increased volume and intensity of training and the increase in individualized training sessions as a result of the selection of the Olympic team.
Jump height was the only measure that showed a consistent increase throughout the testing sessions for both legs in the single-leg jump and for the squat jump. In some cases, this was not concomitant with the highest power or velocity recorded; indeed, in some cases, power seemingly dropped, yet jump height was improved. This indicates that the athlete may have become more neurally coordinated via the training program or through the learning effect, thus making the power generation more efficient; either way, this is a desirable outcome of the training program. A jumping action involves a triple extension of the hip, knee, and ankle, which facilitates a proximal-to-distal momentum transference within the jump (39). Coordination via correct motor patterns induces a transport of muscle power produced by monoarticular muscles via the biarticular muscles in a proximal to distal direction, which increases the efficiency of center of mass movement (5,36,38).
The monitoring of the left- and right-leg SL jumps showed that a bilateral difference was evident from session 1. This bilateral difference in power increased in the second half of the mesocycle; however, this was associated with athlete injury. This may be particularly evident by increases in bilateral difference being shown in the peak values, indicating that maximum power was unable to be achieved in both legs because of injury recovery phase possibly preventing the recruitment of the fast twitch muscle fibers necessary for maximal power. This is further supported as differences in concentric mean power and allometrically scaled mean power were reduced.
To conclude, power, height, velocity, and acceleration are all improved in the final weeks of an Olympic training cycle with a suitable strength and conditioning program. Bilateral differences are not exacerbated in a 9-week training cycle using major lifts and in fact serve to reduce the bilateral difference present. Although anthropometrics and physiological performance markers are important, technical skills also need to be explored to emphasize the importance of correct physique in combats sport. The results from this study are comparable with those of other elite combat sport athletes. Despite power being tracked successfully using jumps, an alternative test examining repeated leg kicking speed may be useful. Furthermore, more comprehensive tracking of athlete's anthropometrical measurements would be advised especially considering the importance of weight category and lean mass for combat sports, which would then be able to be correlated with performance data.
The retrospective analysis of taekwondo athletes who competed at an Olympic games provides strength coaches with indicative anthropometric and power values from elite-level combat sport athletes for reference in their work with similar combat sport groups. This study showed that power is able to be increased considerably in the final 9 weeks of a strength and conditioning program in elite-level Olympic athletes. Thus, coaches can use a method of training based on this mesocycle that has a strong potential to improve power. Furthermore, programs that incorporate major lifts will be effective in improving power in combat sport athletes. In addition, linear encoder systems are a convenient and potentially useful method of tracking alterations in power across time.
The authors would like to acknowledge the Australian Institute of Sport Strength and Conditioning department for the use of the athletes and equipment in this study. The results of this study do not constitute endorsement of the Gymaware linear encoder system by the authors or the National Strength and Conditioning Association.
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Keywords:© 2011 National Strength and Conditioning Association
power monitoring; squat jump; single-leg jump; combat sport