Background: This study investigates differences in muscle co-contraction and peak electromyography (EMG) activity between novice and advanced Taekwondo athletes during consecutive roundhouse (bandal chagui) kicks, examining the influence of body composition and experience level. Methods: Sixteen Taekwondo athletes (12 males, 4 females; mean age: 20.5 ± 4.3 years) were divided into novice (n = 8) and advanced (n = 8) groups. Muscle co-contraction indices and peak EMG activity across 15 consecutive kicks were assessed in key lower limb muscles, including the biceps femoris (BF), lateral gastrocnemius (LG), rectus femoris (RF), soleus (SO), semitendinosus (ST), tibialis anterior (TA), vastus lateralis (VL), and vastus medialis (VM). Results: Advanced athletes exhibited significantly higher co-contraction indices in BF–RF, VM–BF, and SO–TA pairs (p < 0.05) and increased peak EMG trends in the BF and LG (p < 0.05). Novice athletes showed significantly reduced peak EMG increases in the RF, VM, and VL. EMG trends were influenced by body composition, with principal component analysis indicating that higher fat mass and lower muscle mass were associated with greater variations in muscle activation. Conclusions: These findings suggest that advanced athletes refine motor control through increased co-contraction, improving stability and efficiency, while novices exhibit less optimized coordination patterns. This study provides insights into the neuromechanical adaptations associated with expertise development in Taekwondo.

Background: This study investigates differences in muscle co-contraction and peak electromyography (EMG) activity between novice and advanced taekwondo athletes during consecutive roundhouse (bandal chagui) kicks, examining the influence of body composition and experience level. Methods: Sixteen taekwondo athletes (12 males, 4 females; mean age: 20.5±4.3 years) were divided into novice (n=8) and advanced (n=8) groups. Muscle co-contraction indices and peak EMG activity across 15 consecutive kicks were assesed in key lower limb muscles, including the biceps femoris (BF), lateral gastrocnemius (LG), rectus femoris (RF), soleus (SO), semitendinosus (ST), tibialis anterior (TA), vastus lateralis (VL), and vastus medialis (VM). Results: Advanced athletes exhibited significantly higher co-contraction indices in BF–RF, VM–BF, and SO–TA pairs (p < 0.05) and increased peak EMG trends in BF and LG (p< 0.05). Novice athletes showed significantly reduced peak EMG increases in RF, VM, and VL. Body composition in-fluenced EMG trends, with higher fat mass and lower muscle mass associated with greater variations in muscle activation. Conclusions: These findings suggest that advanced athletes refine motor control through increased co-contraction, improving stability and efficiency, while novices exhibit less optimized coordination patterns. This study provides insights into the neuromechanical adaptations associated with expertise development in taekwondo.

Objectives: This study examined the influence of hearing status and loneliness on verbal fluency trajectories in adults aged 60 years and older, assessing their contributions to baseline performance and longitudinal change over time. Methods: Data were drawn from 4,929 participants in the Health and Retirement Study (HRS) with objective hearing assessment in 2018 and three waves of semantic verbal fluency and loneliness measured in 2018, 2020, and 2022. Latent growth curve models were estimated to examine longitudinal change. Results: Verbal fluency showed a small but statistically significant increase over time, whereas loneliness showed a slight decrease over time. Worse hearing status predicted lower baseline verbal fluency and higher baseline loneliness. The association between hearing status and longitudinal change in verbal fluency was observed in partially adjusted models but was attenuated and did not reach statistical significance after full covariate adjustment. Discussion: These findings support an association between hearing status and baseline levels of verbal fluency and loneliness, while evidence for longitudinal change in verbal fluency was limited to partially adjusted models.