Effects of Sex and Leg Dominance on Lower Extremity Alignment in Youth Korean Taekwondo Sparring Athletes: An Observational Study
Article information
Abstract
PURPOSE
To compare lower extremity alignment in young taekwondo-sparring athletes according to sex and leg dominance.
METHODS
Ninety-five young Taekwondo sparring athletes participated in this study. Additionally, 12 lower extremity alignment measurements (hip anteversion, Q-angle, tibiofemoral angle, genu recurvatum, navicular height, rearfoot and forefoot alignment, pelvic tilt, and tibial torsion) were obtained. An independent t-test was used to determine the differences in lower-extremity alignment based on sex and leg dominance.
RESULTS
Standing and supine Q-angles, standing and supine tibiofemoral angles, genu recurvatum, and rearfoot alignment (prone) differed significantly between dominant and non-dominant legs, with variations observed by sex (p<.05). For the non-dominant leg, significant sex-related differences were observed in standing and supine Q-angles, standing and supine tibiofemoral angles, genu recurvatum, as well as rearfoot (prone) and forefoot alignment. Hip anteversion also differed with leg dominance (p<.05).
CONCLUSIONS
Our results suggest that women may be at a higher risk of knee and ankle injuries, such as anterior cruciate ligament tears and lateral ankle sprains, compared to men due to greater deformities in lower extremity alignment which could negatively impact the skills and movements required for taekwondo sparring. Therefore, trainers and clinicians should consider implementing prevention programs to reduce injuries to specific body parts among women according to their alignment outcomes. In addition, evaluation of lower-extremity alignment is essential to minimize potential injuries.
INTRODUCTION
Overall, the training duration and frequency for junior varsity and varsity athletes in Korea are approximately 22 hours 9 minutes and 27 hours 35 minutes, respectively, for 5-7 times per week [1]. High training frequency may be linked to overuse injuries in adolescents, as shown by Eric G Post [2]. Accompanying injury rates of 43.7% during games and 56.3% during training have been reported [3,4]. Unlike adults, growing adolescents are vulnerable to stress because of their immature skeletons and growth plates, and their epiphyseal and epiphyseal tissues are more vulnerable than those of adults [5]. Based on these characteristics, musculoskeletal damage due to overuse or high training volume occurs more frequently in adolescents than in adults [6]. A previous study that investigated injuries in Taekwondo athletes reported the injury rate for youth athletes as 1.86 times higher than that in adults [6].
For sparring Taekwondo, injuries to athletes include contact injuries that involve direct physical contact with an opponent [7] and noncontact injuries that occur during instantaneous movements without physical contact or controlling internal power imbalances [8]. Lower extremity injuries, including contact and noncontact, are more frequent than upper extremity injuries [6] and noncontact injuries are reported to occur more frequently than contact injuries in lower extremity injuries [9]. This is because Taekwondo sparring players have a high incidence of injuries that occur due to the inability to properly deal with the internal forces generated in the body when landing incorrectly after a kick or jump due to imbalances in lower extremity alignment and muscle strength [9,10].
Female athletes have a higher injury rate than do male athletes. This may be explained by anatomical characteristics such as the quadriceps femoris angle and excessive hindfoot pronation, which are relatively higher for women than for men [11]. The Q-angle is the most noticeable parameter of alignment that differs with sex. It is used to predict the risk of damage to lower extremity joints, such as the pelvis, knees, and ankles [12]. In general, the normal range is approximately 16-17° in standing position and 14-16° in supine position for female, and approximately 13-14° in standing position and 12-14° in supine position for male [13-15]. The risk of injuries, such as patellar pain, walking disability, and osteo-chondral and cartilaginous plate damage, increases with increasing Q-angle [16]. Similarly, injuries in Taekwondo-sparring athletes are mark-edly influenced by internal factors, including the kicking mechanism during an attack [10].
There are several different kicks in sparring, including front kicks, side kicks, back kicks, and round kicks [17], but sparring athletes are more likely to use round kicks during competitions because they can score at high speed [18,19]. In addition, most sparring athletes have a dominant leg, which they use more frequently to increase the accuracy and power of an attack when using round kicks, and a non-dominant leg, which they use for weight support [20,21]. Differences in the movement characteristics of each leg during a roundhouse kick affect the tilt of the pelvis and the direction of rotation of the pelvis, thighs, knees, and ankles [22]. The dominant leg (attacking leg) begins rotating from the pelvis with accompanying rapid flexion and extension of the hip and knee joints [23]. At this time, the hip joint tilts and rotates toward the side of the pivot leg, and a clockwise torsional moment occurs at the knee joint because of the external rotation of the lower leg [20,22]. The thigh of the non-dominant leg, which contributes to stability during an attack, begins with external rotation and internal rotation, followed by repeated external rotation, and a counterclockwise torsion occurs at the knee joint. This occurs most significantly when striking an object [20]. The ankle remains in dorsiflexion until just before the kicking foot leaves the ground. There is plantar flexion at the moment of landing, and dorsiflexion resumes at the point of impact [22].
Asymmetric and dynamic movements between the lower limb segments owing to functional differences in each leg result in deformation/alterations of the lower extremity alignment, which is considered a cause of malalignment in Taekwondo athletes [24]. In adolescents, functional and structural changes such as alignment in growing adolescents increase the likelihood of musculoskeletal injury [25,26]. However, research on the alignment characteristics of young athletes is lacking. Therefore, this study aimed to provide basic data for predicting the cause of injuries by investigating the sex- and dominant leg-related differences in lower extremity alignment in young Taekwondo sparring athletes.
METHODS
1. Participants
Ninety-five youth taekwondo sparring athletes participated in the study. The athletes were registered as sparring athletes by the Korea Taekwondo Association in 2021. All subjects were between 14 and 19 years of age and had at least one year of playing experience. The subjects participated in this study voluntarily. None of the subjects had a history of lower extremity injury that could affect leg alignment in the past 6 months. The minimum sample size for an effect size of 0.5, α-value of 0.05, and power (1-β) of 0.8 was 102, as determined by the G*Power program (G-power Power Analysis Software; Universitat Kiel, Germany) [27,28]. However, due to limitations in recruiting eligible athletes within a single competition year, only 95 participants were included (Table 1).
Demographic characteristics of study participants
2. Measurement tools
We established intraclass correlation coefficient (ICC) levels for mea-suring the lower extremity alignment. Lower extremity alignment was assessed using a set of validated instruments, each selected based on its suitability for specific anatomical variables. A bubble inclinometer was used to assess hip anteversion, while a goniometer and a mobile application with a built-in camera (Alignment, alpha version 1.0.2, Yonsei University, Seoul, Korea) were used to measure Q-angle, tibiofemoral angle, genu recurvatum, tibial torsion, rearfoot alignment, and forefoot alignment. A height gauge (H4-20, Mitutoyo Mfg. Co. Ltd., Tokyo, Japan) was used to conduct the navicular drop test, due to its high resolution and precision for small-distance measurements. A palpation meter (Baseline Evaluation Instruments, White Plains, NY, USA) was employed to assess pelvic tilt angle. Each tool was selected based on its clinical utility, re-peatability, and appropriateness for evaluating structural alignment in adolescent Taekwondo athletes (Table 2).
Measurement tools
3. Measurement
Lower extremity alignment was measured in the prone, standing, and supine positions, and the measurement method was based on a previous study [41]. The measurement items and methods were as follows.
1) Hip anteversion
With the participant in the prone position, the knee was flexed at 90° and the examiner passively rotated the leg by holding the ankles until the most prominent part of the greater trochanter (GT) was palpated on the palm of the other hand. When the most prominent part was palpated, the bubble inclinometer was placed at the 1/3 point on the medial side of the tibial shaft, and the angle was measured. The measurement ICC value in this study was 0.952.
2) Quadriceps angle (Q-angle)
The Q-angle was measured twice in the standing and supine positions. First, the midpoint of the patella was marked. The fulcrum of the goniometer was aligned with the midpoint, with the reference arm pointing to the tibial tuberosity and the moving arm pointing to the anterior superior iliac spine (ASIS). The measurement ICC values in this study were 0.888 in standing and 0.822 in supine.
3) Tibiofemoral angle
The tibiofemoral angle was measured twice in the standing and supine positions, marked on the midpoint of the knee joint line between the ASIS and GT and the medial and lateral malleoli. The fulcrum of the goniometer was located at the midpoint of the knee joint line, the reference arm pointed to the midpoint between the ASIS and GT, and the moving arm pointed to the marked point between the medial and lateral malleoli. The measurement ICC values in this study were 0.891 in standing and 0.907 in supine.
4) Genu recurvatum
With the study participants in the supine position, a foam roller was placed under the ankle. The fulcrum of the goniometer was located at the midpoint of the lateral knee joint line, the reference arm was aligned with the GT, and the moving arm was pointed towards the lateral malle-olus. The measurement ICC value of this study was 0.944.
5) Navicular drop test
While the participant was standing, the examiner made a mark on the navicular tubercle and palpated the talar head using the thumb and index finger to determine the neutral position of the talus. The height of the navicular tubercle was measured in the neutral position. The height of the navicular tubercle was re-measured in a comfortable weight-bearing standing position. The difference in the height of the navicular tubercle between the neutral and weight-bearing standing positions was calculated by subtracting each other. The measurement ICC value of this study was 0.846.
6) Rear foot angle
Measurements were performed in the standing and prone positions. The examiner marked a dot at the midpoint between the medial and lateral malleoli, the calcaneus, and two-thirds of the calf. The center of the fulcrum was located at the midpoint between the medial and lateral malleoli, and the reference and moving arms were aligned with the midpoint of the calcaneus and calf, respectively. The measurement ICC values of this study were 0.802 in standing and 0.857 in prone.
7) Forefoot angle
This measurement was performed with the participant in the prone position. With the subtalar joint in a neutral position, the angle between the plantar surface of the forefoot and the virtual axis was measured using a goniometer. The measurement ICC value of this study was 0.914.
8) Pelvic tilt angle
Pelvic tilt angle was measured in a relaxed standing position as com-monly described in clinical assessment. The palpator's arms were placed on the anterior superior iliac spine (ASIS) and posterior superior iliac spine (PSIS) respectively, and the angle between these two points was re-corded. To ensure consistency of measurement, participants were in-structed to assume a posture with their feet shoulder width apart, their arms naturally at their sides, and their gaze fixed straight ahead. This standardized posture is consistent with established protocols in physical therapy assessment. In this study, the ICC value for this measurement was 0.801.
9) Tibial torsion
Measurements were performed with the participants in the supine position. The knee was neutralized by paralleling the lateral and medial epicondyles and marking dots at the midpoint between the medial and lateral malleoli. An imaginary vertical axis was created with respect to an imaginary line connecting the malleoli on both sides, and the angle was measured using a goniometer. The measurement ICC value of this study was 0.838.
All the measurements of lower extremity alignment were performed in the same manner for both sides.
3. Statistical analysis
Data processing for this study was performed using SPSS software (version 26.0; SPSS, Chicago, IL, USA) to calculate the mean, percentage, and standard error of all measurements. An independent t-test was used to determine the differences in each variable (α-value=0.05).
RESULTS
1. Differences in lower extremity alignment of the dominant leg according to sex
The differences in the lower extremity alignment of the dominant leg according to the sex of the young Taekwondo sparring athletes are presented in Table 3. The standing (F=0.396, p <.001) and supine (F=0.310, p <.001) Q-angles and standing (F=0.090, p <.01) and supine (F=0.488, p <.001) tibiofemoral angles were significantly different in males and females (p<.05). The genu recurvatum (F=3.090, p<.001) also showed a significant difference (p <.05), and the rear foot angle (F=0.662, p <.05) showed a significant difference only in the prone position (p<.05).
Differences in lower extremity alignment of the dominant leg according to sex
2. Differences in lower extremity alignment of the non-dominant leg according to sex
The differences in the lower extremity alignment of the non-dominant leg according to the sex of the young Taekwondo sparring athletes are presented in Table 4. The standing (F=4.740, p <.001) and supine (F=8.969, p <.001) Q-angles and standing (F=0.001, p <.01) and supine (F=0.705, p <.001) tibiofemoral angles were significantly different for males and females (p <.05). The genu recurvatum (F=2.186, p <.01) was also significantly different for males and females (p <.05), while the rear foot angle (F=4.807, p <.05) showed a significant difference only in the prone position (p <.05). The forefoot angle (F=6.568, p <.05) was significantly different for males and females, unlike for the dominant leg (p<.05).
Differences in lower extremity alignment of the non-dominant leg according to sex
3. Differences in lower extremity alignment in the dominant and non-dominant leg
The lower extremity alignment differed in the dominant and non-dominant feet of the young Taekwondo sparring athletes only for hip anteversion (F=1.495, p <.05) as shown in Table 5.
Differences in lower extremity alignment according to dominant and non-dominant leg
DISCUSSION
1. Sex-related differences in lower extremity alignment in the dominant leg
When comparing lower extremity alignment of the dominant leg by sex, female athletes exhibited greater Q-angle, tibiofemoral angle, and rear foot angle values compared to male athletes, indicating a tendency toward knee valgus and ankle pronation alignment. In addition, the higher genu recurvatum values observed in female athletes suggest an increased propensity for hyperextension alignment of the knee. These results are consistent with those of previous studies reporting that the Q-angle, tibiofemoral angle, and genu recurvatum were greater in women than in men, and women had more frequent ankle abduction than did men [29,30].
Kicking begins with the activation of the hip flexor muscle, followed by the lateralis muscle, biceps femoris, rectus femoris, gluteus maximus, and gastrocnemius [31].
Kicking starts with the rotation of the waist with the eccentric con-traction of the quadriceps muscle [31,32], and the amount of shock generated by the reaction to the impact is transmitted to the lower extremity segment. Thus, the tibia is pushed backward, and the femur is pushed forward. This generates a translation (shear) force that causes abnormal knee joint positioning [32]. According to previous studies, ground contact using an asymmetric foot, shifting unilateral weight, and hyperextension during kicking cause abnormal movement of the knee joint [33]. Genu recurvatum refers to chronic hyperextended knee alignment and is characterized by weakness of the anterior muscles of the thigh, such as the quadriceps femoris and vastus medialis [34]. Female athletes are easily exposed to this type of misalignment because their quadriceps muscle activity is insufficient relative to that of male athletes [35,36], and women have a more internally rotated femur and knee valgus alignment than do men. This results in decreased hip adduction and increased knee abduction. Mitani reported that high Q-angle, hip internal rotation, and low plantar arch were associated with a higher history of sports injuries in female athletes [37]. Additionally, the alignment of the valgum, which appears as a hyperextension of the knee, results in internal rotation of the femur and external rotation of the tibia [38]. This leads to the internal rotation of the ankle, which is related to the abduction angle of the rear foot [34]. The dominant foot of sparring athletes kicks with the forefoot on the ground, and the ankle tends to rotate internally, leading to the abduction of the rear foot. This can easily result in ankle injuries because of the increased tension of the lateral ligaments and joints [11] and pressure on the talus [39]. Continuous kicks and steps also frequently involve lifting the heel and supporting only the forefoot; thus, the resulting imbalance of plantar pressure interrupts the stability of the body [40]. Female Taekwondo athletes have a relatively larger valgus angle than do male Taekwondo athletes, and their alignment is more easily affected by the movement characteristics of the dominant foot when kicking in Taekwondo. Therefore, it speculates that excessive repetitive movements with genu valgum, genu recurvatum, and flat foot in female athletes may cause injuries such as ankle sprain, patellofemoral pain syndrome, anterior cruciate ligament rupture, osteoarthritis, and ankle and knee instability.
2. Sex-related differences in lower extremity alignment of the non-dominant leg
When comparing the lower extremity alignment of the non-dominant leg by sex, female athletes showed significantly greater values in Q-angle, tibiofemoral angle, genu recurvatum, and rearfoot angle measured in the prone position than their male counterparts. These patterns were consistent with the results observed in the dominant leg. However, in contrast to the dominant side, female athletes had significantly lower values for the forefoot angle, indicating a significant sex difference and suggesting a greater tendency for forefoot valgus alignment and foot overpronation in females. These results are similar to those of previous studies. These studies reported that female have greater Q-angles, tibiofemoral angles and genu recurvatum values and lower dynamic postural stability and valgus rear foot than male [25]. On the other hand, this result is contrary to previous studies that showed no significant difference in the forefoot angles of men and women [41].
In the pivot leg, where the dynamic stability of the hip and knee is important, activation of the hamstrings and gluteus medius occurs first when performing a kick [36,42]. Subsequently, the biceps femoris, rectus femoris, and hip adductors are activated. Additionally, hip abduction and valgus knee valgus worsen, generating forces that internally rotate the femur and externally rotate the tibia [43]. As sparring athletes often attempt head strikes to achieve high scores, the opposing rotational forces between the femur and tibia place a greater load on the knee joints.
In addition, the pivot leg supports the impact and all body weight during an attack, while the foot is fixed to the ground. The knee is hyperextended, and each segment rotates. Owing to this characteristic movement, the alignment of the valgum is such that the patella is heavily biased toward the medial side. Female athletes with flexible joints have an excessively formed genu recurvatum relative to male athletes when supporting the impact force during an attack with the knee hyperextended. The quad-to-hamstring ratio is also unbalanced relative to that in male athletes, resulting in increased knee dynamic valgus angle, Q-angle, and tibiofemoral angle. As a result, knee ligament and cartilage damage, such as in the ACL and meniscus, which are noncontact injuries, frequently occur in the pivot leg [43].
Similar to the dominant leg, the genu valgum alignment is associated with ankle eversion. During kicking, the pivot leg contributes to stability by supporting the overall body weight and rotational force with the forefoot while the heel is raised and the ankle is plantar-flexed [44]. This forefoot-centered pressure distribution causes valgus of the forefoot and hy-perpronation of the ankle. These characteristics are thought to cause significant differences in the forefoot, albeit only in the non-dominant leg. Therefore, female athletes with overpronation of the ankle and a smaller forefoot angle than male athletes are thought to be vulnerable to injuries such as plantar fasciitis and ankle sprains due to foot instability [45-47].
3. Differences in lower extremity alignment in the dominant and non-dominant leg
The difference in lower extremity alignment between the dominant and non-dominant feet was higher in the dominant foot than in the non-dominant foot only in the anterior hip tilt, and no significant differences were found for the other factors. These results are similar to those of a previous study [48] that reported that elite Taekwondo athletes had no asymmetry between their feet during round kicks.
These results are attributable to the frequent use of anomalous kicks rather than typical round kicks by athletes after the introduction of electronic body protectors. To manage a match that is more suitable for scoring with electronic protectors [6,49], high-difficulty attacks were reduced and anomalous kicks, such as cut kicks and monkey kicks, were introduced [49]. The cut kick is a movement that raises the leg height and interrupts the opponent's attack, whereas the monkey kick is a technique of pushing the body of the opponent with the sole or scoring points when the opponent is in close range [49]. Anomalous kicks and monkey kick in Taekwondo sparring are known to require bilateral en-gagement, as emphasized in previous studies [45]. Unlike the roundhouse kick, these techniques are characterized by linear motion and lower rotational demand, which is believed to reduce torsional stress on lower limb segments [27]. On the other hand, anomalous kicks, including the monkey kick, demand substantial flexibility and muscular strength of the hip joint. Previous electromyographic research reported higher activation of the hip flexors in the dominant leg during the exe-cution of such techniques [31]. This supports the findings of the present study, where the dominant leg demonstrated greater hip anteversion compared to the non-dominant leg.
In addition, it is speculated that the continuous kick used to attack immediately after defending against quick steps when the distance to the opponent is small may have had an impact. This technique has a high scoring rate even with a small number of close attacks; therefore, it has been widely used by sparring athletes and has recently been reported as the preferred technique, especially among heavyweight female athletes who have lower speed and power than male athletes [50]. Therefore, a continuous kick leads to the even use of both feet rather than primary use of only one foot [51], which is believed to have played a role in the results of this study.
Considering these results, the lower extremity alignment of young Taekwondo athletes appears to be more influenced by sex than by leg dominance. Previous studies have reported that female Taekwondo sparring athletes have the highest rates of ankle and knee injuries [52,53], and suggested that Q-angle and pronation of the Rear foot angle are significantly related to the lower extremity injury rates of female athletes [45,54]. Therefore, the results of this study may serve as predictors of increased risk of ankle and knee injuries in female Taekwondo athletes.
This study had limitations. The judgment of alignment and prediction of injuries were based only on movements within the lower extremity segment during Taekwondo sparring kicks. Several internal and external factors affect lower extremity alignment in Taekwondo through complex and difficult mechanisms. In addition, there may be an effect of the small sample size. Therefore, for a more accurate analysis, the height of the kick, the distance from the point of impact, various types of kicks, and the movement patterns of the upper extremities should be considered, and a retrospective study with a secured sample size is needed.
CONCLUSION
Based on our results, women may have a higher risk of knee and ankle injuries such as ACL tears and lateral ankle sprains, than men because of some excessive deformity in the lower extremity alignment that could affect their skills and movements required for taekwondo sparring. Therefore, trainers and clinicians should consider prevention programs to reduce injuries among women in specific body parts according to their alignment outcomes. Also, an implementing the evaluation of lower extremity alignment should be essential to minimize potential injuries.
Notes
CONFLICT OF INTEREST
The authors declare no conflicts of interest.
AUTHOR CONTRIBUTIONS
Conceptualization: MO Han; Data curation: MO Han; Formal analysis: JS Jeong; Funding acquisition: HP Jun; Methodology: MO Han; Proj-ect administration: MO Han, HP Jun; Visualization: J Jeong; Writing - original draft: JS Jeong; Writing - review & editing: MO Han, HP Jun.