Youngsuk Kim’s research while affiliated with Jeonbuk National University and other places

The primary objective of the study was to evaluate the risk of lower-extremity injury during landing, after catching a basketball in the air for a rebound or a steal. A total of 32 (15 females and 17 males) recreational basketball players were asked to perform 4 different arm-reaching movements during the flight phase: no reaching, left (LAR), right (RAR), and bilateral (BAR) arm reaching. Knee and hip flexion and abduction angles at initial ground contact, peak ground reaction force within 100 milliseconds after contact, and peak moments for the hip and knee joints were analyzed. LAR, RAR, and BAR showed significantly smaller peak hip and knee flexion angles, while LAR demonstrated a significant increase in the knee’s peak abduction angle. Furthermore, the peak abduction moments of LAR were significantly increased in both males and females. Aerial basketball catching movements resulted in stiffer leg joints and larger knee abduction during landing, which was a potential factor in increasing the risk of lower-limb injury upon landing. It is recommended to include a softer landing technique and implement a training program for enhancing knee joint stabilization in the frontal plane.

This study aimed to investigate the effects of 60-second static stretching on the neuromuscular control strategies of lower limb muscles during a squat jump (SJ), with a specific focus on changes in muscle synergy patterns, muscle weightings, and temporal activation characteristics. The muscles targeted for stretching included the quadriceps, hamstrings, and triceps surae. Electromyography (EMG) was used to assess the activity of the biceps femoris (BFL), triceps surae(TS), rectus femoris (RF), vastus lateralis (VL), and vastus medialis (VM). Twenty-five active males completed experiments under both a static stretching condition (SS) and a non-stretching condition (NS). Electromyography and non-negative matrix factorization (NMF) were employed to extract muscle synergy and the muscle weightings along with temporal activation characteristics were subsequently analyzed. The results revealed two distinct muscle synergy patterns in both the SS and NS. 60-second static stretching had no significant impact on the number of muscle synergy patterns during the squat jump. However, it significantly altered the contribution and temporal activation characteristics of individual muscles. Notably, post-stretching muscle activation levels were lower during the early phase of the jump, necessitating compensatory activation in the later phase to maintain performance. Additionally, jump heights were significantly lower in the stretched compared to the non-stretched condition.These findings suggest that while 60 seconds of static stretching before explosive movements may impair neuromuscular efficiency, ensuring proper and balanced static stretching for all muscle groups could help mitigate over-reliance on individual muscles.

Background Long-term training focused on specific skills significantly influences athletes’ physical control abilities. Aim To evaluate the balance control capabilities during kicking actions of different Taekwondo skill groups (kyorugi (K); poomsae (P); demonstration (D)), and long-term training effects of the different Taekwondo skills on body control. Subjects and methods The present study utilised a motion capture system and a ground reaction force system to compare and analyse the balance control abilities of athletes across various Taekwondo practices (kyorugi, poomsae, demonstration) during the execution of an identical kicking motion. All participants’ (23 male college athletes) kicks were aimed at nose height. Results The results indicate that K exhibited distinct COM trajectories in left–right and front–back directions during front kicks, whereas differences of COM lateral displacement during kicking moments existed across all groups. P demonstrated greater COP movements in forward, backward, left, and right directions. Long-term training in different skills affected mechanisms of body control during the kicking technique. K and D tended to prioritise maintaining vertical stability, upward power output, and efficient movements to ensure rapid, accurate striking while maintaining balance and stability, whereas P emphasised the horizontal posture, flexibility, expressive qualities, and artistry of their movements, which may be involving more body sway and adjustments during competitions. Conclusions Athletes in different skill groups should develop personalised training plans tailored to their specific skill characteristics and competition demands. These plans aim to enhance the movement control abilities of athletes in various disciplines, ensuring they can deliver optimal performance during competitions.

Fatigue causes the lower limb to land in an injury-prone state, but the underlying neuromuscular control changes remain unclear. This study aims to investigate lower limb muscle synergies during landing in basketball players, both before and after fatigue, to examine alterations in neuromuscular control strategies induced by fatigue. Eighteen male recreational basketball players performed landing tasks pre- and post-fatigue induced by 10 × 10 countermovement jumps. Electromyographic (EMG) data from eight muscles, including the erector spinae (ES), rectus abdominus (RA), gluteus maximus (GM), rectus femoris (RF), biceps femoris (BF), lateral gastrocnemius (LG), soleus (SM), and tibialis anterior (TA) muscles, were analyzed using non-negative matrix factorization to extract muscle synergies. Post-fatigue results revealed significant changes: synergy primitive 1 decreased before landing (18–30% phase) and synergy primitive 2 decreased after landing (60–100% phase). Muscle weights of the LG and SM in synergy module 2 increased. Fatigue reduced synergistic muscle activation levels, compromising joint stability and increasing knee joint loading due to greater reliance on calf muscles. These changes heighten the risk of lower limb injuries. To mitigate fatigue-induced injury risks, athletes should improve thigh muscle endurance and enhance neuromuscular control, fostering better synergy between thigh and calf muscles during fatigued conditions.

Biomechanical efficiency of baseball pitch is considered to be a better indicator for evaluating pitching skills. Since there is a relationship between elbow varus and elbow mechanics during the arm cocking phase, we attempted to include this variable in the multiple regression analysis to improve the understanding of the biomechanical efficiency of baseball pitching. The fastest pitching of 68 college baseball pitchers was used for analysis. The regression results showed that maximum elbow flexion angle (β: −2.615, p: 0.003), shoulder external rotation angle at the moment of maximum external rotation (MER) (β: 2.881, p: 0.004), maximum trunk rotation velocity (β: −0.333, p: 0.001), trunk rotation angle at the moment of stride foot contact (SFC) (β: −2.031, p:0.006), time between maximum pelvic rotation velocity and maximum trunk rotation velocity (β: 1.238, p: 0.023), and shoulder abduction angle at the moment of SFC (β: −2.048, p: 0.033) correlated with biomechanical efficiency and explained 45% of the variance in biomechanical efficiency. Therefore, further improvements in elbow mechanics during the arm cocking phase, based on improvements in early pitching mechanics, may help to increase pitching velocity per unit of elbow varus torque.

The aim of this study was to elucidate the effect of shooting distance and skill level on the arm movements (kinematics, kinetics and electromyography) during the release phase of basketball shooting. 14 males were student-athletes from local college basketball teams(skilled) and 14 were recreational basketball players from local colleges(unskilled). Each participant completed three successful shots at two distance conditions (5 m, 6.8 m). The energy generated by the joint during the shot and electromyographic variables of the anterior deltoid (AD), triceps brachii (TB), and flexor carpi radialis (FCR) muscles were evaluated. The results showed that S and US groups showed decreases in shooting success with increasing shooting distance (P < 0.001), and increases in muscle activation and joint energy production in shoulder and elbow joints (P < 0.001). During longer distance shooting, S and Us groups showed significant differences in wrist flexion angle (P < 0.001). In addition, S demonstrated more energy production at the shoulder, elbow, and wrist joints (P < 0.01), and greater activation (P < 0.05) in the anterior deltoid (AD), triceps brachii (TB), and flexor carpi radialis (FCR) corresponding to the joints (MVIC%). These results suggest that the skills of shooting arm to produce proper force, and active muscle coupling of joints to produce energy are important for adaptation to different basketball shooting distance.

Prior studies have suggested that dance may mitigate fall risks by enhancing muscular strength; despite its apparent safety, compelling evidence substantiating its efficacy in fall prevention remains scarce. The objective of this study was to examine whether individuals with prolonged dance training demonstrate distinct biomechanical responses to fall risk in contrast to those without dance experience. Methods: Thirty-two participants were recruited internally from a university setting (comprising 8 non-dancers, 8 ballet dancers, 8 korean dancers, and 8 modern dancers) for this investigation. Kinematic and kinetic data were scrutinized using Visual-3D software, and subsequent analyses involved data normalization, with One-way ANOVA conducted using SPSS 23.0 software. Results: Ballet dancers and modern dancers displayed longer stride lengths, narrower step widths, and quicker walking speeds compared to non-dancers; Korean dancers exhibited shorter stride lengths, narrower step widths, slower walking speeds, and higher gait symmetry. Modern dancers demonstrated the highest MTC during swing phase, while korean dancers showed the smallest HCV, thus yielding the lowest RCOF. Conclusion: Korean dancers demonstrated the lower risks of falls and trips; rigorous professional training in dancers fosters distinctive, stable gaits, superior joint control, and robust body balance, all contributing to a decrease of the likelihood of risks of falls and trips. Conversely, while modern dancers similarly showed the reduced risks, the varied styles in modern dance may be introducing some uncertainty in mitigating risks of falls and trips.

Background: the objective of this study is to evaluate gait symmetry in female dancers of different dance styles aged 19–21 years. The findings would enable us to understand the effects of long-term training on dancers’ gait. Material and methods: 21 dancers (8 modern dancers, 6 ballet dancers, and 7 Korean dancers) and 15 normal participants completed three validated walking tests at normal speed on a 5 m × 1 m walking track. Results: The modern dancer group showed a significant difference from the control group in terms of step length symmetry index. The right hip sagittal plane ROM was smaller in both the ballet dancer group and the Korean dancer group than in the control group. There was a significant difference in sagittal plane hip ROM in the Korean dancer group compared with the control group. The hip symmetry index in the horizontal plane was greater in all three groups of dancers than in the control group. Conclusions: Long-term training between different dance styles leads to different gait asymmetry effects in dancers.