Minji Son

Effects of chronic ankle instability and induced mediolateral muscular fatigue of the ankle on competitive taekwondo athletes

[Purpose] The purpose of this study was to investigate the effects of chronic ankle instability and induced mediolateral muscular fatigue of the ankle on competitive Taekwondo athletes during single-leg drop landing. [Subjects and Methods] Fourteen competitive taekwondo athletes with chronic ankle instability and 14 healthy adults participated, and they performed three single-leg drop landings from a 40-cm height before and after induced fatigue. Ankle angular position, peak vertical ground reaction force, loading rate, eccentric work, and contribution were calculated and analyzed. [Results] Athletes had lower ankle eversion and abduction angle than the controls did at maximum knee flexion both pre- and post-fatigue. Furthermore, athletes had lower eccentric work of the hip than the controls did post-fatigue, and they had lower eccentric work of the knee than controls at both pre- and post-fatigue. The eccentric work of the knee increased while, peak vertical ground reaction force decreased in both, athletes as well as controls post-fatigue. [Conclusion] Taekwondo athletes with chronic ankle instability who participate in a high-intensity training program are continuously exposed to potential injuries of their ankle or knee joints. Therefore, competitive taekwondo athletes with chronic ankle instability should limit their participation in regular training until they complete the rehabilitation process.

Postural stability for taekwondo athletes with repetitive ankle sprains during a single-leg stance

[Purpose] The purpose of this study is to investigate postural stability in such group of taekwondo athletes by measuring the center-of-pressure variables in both the injured limb and uninjured limb during a single-leg stance with eyes closed. [Subjects and Methods] The study includes eleven taekwondo athletes with repetitive ankle sprains (RASs) and eleven healthy taekwondo athletes (the controls) at the college level participating in taekwondo training sessions. For the controls, the “injured” limb was taken to be the left limb. [Results] The postural stability measured in both the anteroposterior and mediolateral directions using center-of-pressure variables was lower in the uninjured limb of the RAS group than in the control group during a single-leg stance with eyes closed. However, for the injured limb, there were no significant differences between the two groups. Furthermore, compared to the RAS group, the control group had higher stability in the injured limb than in the uninjured limb. [Conclusion] Individuals with RASs should ensure improvements in their proprioceptive and neuromuscular functions, as well as muscle strength, through an adequate period of rehabilitation to reduce the risk of re-injury.

Depression and posture in patients with Parkinson’s disease

BACKGROUND Depression is an important non-motor symptom of Parkinsons disease (PD) that significantly impacts the daily activities of affected patients. Furthermore, the stooped posture that characterizes patients with PD has also been associated with depression. The purpose of this study was to investigate the relationship between the presence of depressive symptoms and body posture in patients with PD. METHODS Forty-six patients with mild-to-moderate PD were recruited. The patients were divided into depression and no depression groups based on Beck Depression Inventory scores. All patients underwent kinematic analysis conducted in the upright standing posture with a motion capture system. RESULTS There were no differences in clinical characteristics between the depression (n = 22) and no depression groups (n = 24). In the standing position, patients with depression showed anterior tilting of the head from the pelvis and an increased distance between head and pelvis. The severity of depression was correlated with the degree of flexion at the lower trunk level and the degree of anterior tilting of the head, neck, and trunk from the pelvis and base of support. CONCLUSIONS Patients with PD and depression showed increased flexion at pelvis level, which caused the trunk to tilt anteriorly. In addition, the severity of depression was correlated with the degree of anterior tilting of the head and trunk. These findings suggest that stooped posture, especially from the pelvis level, could be a marker of depression in patients with PD.

The effect of knee flexor and extensor fatigue on shock absorption during cutting movements after a jump landing

BACKGROUND Sporting situations include instances of continuous and/or integrated movements. However, the effect of fatigue on the performance of these movements remains unclear. PURPOSE To investigate the effect of knee flexor and extensor fatigue on the shock absorption strategy of the lower limb during cutting movements performed after jump landings. METHODS Twenty-four healthy participants performed cutting movements following jump landings from two heights - 30cm and 40cm - and under three levels of lower limb fatigue: pre-fatigue (100% peak knee extension torque), and post-fatigue 50% (post-50%) and 30% (post-30%) peak knee extension torque. Fatigue was induced by repeated isokinetic flexion/extension of the knee (60°/s). RESULTS Compared to the pre-fatigue condition, power and work at the knee joint decreased under both post-50% and post-30% conditions (P<0.001), while the work performed by the ankle (P<0.001) increased significantly. An increase in height from 30cm to 40cm was associated with an increase in the range of motion of the ankle (P<0.001) and knee (P=0.022), peak vertical ground reaction force (P<0.001), rate of loading (P<0.001), knee stiffness (P=0.026) and peak power of the knee (P<0.001), as well as the work performed by the knee (P<0.001) and hip (P<0.001) joints. CONCLUSIONS Under substantial muscle fatigue the proportion of shock absorption contributed by the knee for cutting movements performed after jump landings from a height of 40cm decreased; there was an adaptive increase in the contribution by the ankle.

Golf club characteristics and vertical force distribution associated with pitch and lob shots of different carry distances

The purpose of this study was to investigate the club characteristics and vertical force distribution of pitch and lob shots of 20 and 30 m in female golfers from the Korean Ladies Professional Golf Association (age: 21.3 ± 1.7 years; height: 161.5 ± 4.4 cm; body weight: 60.3 ± 5.6 kg; career: 7.5 ± 1.7 years). Ten infrared cameras and two force plates were used to record the swing of each golfer. The test golf swings included a pitch and lob shot to target distances of 20 and 30 m. The carry distance for the 20 and 30 m shots was affected by club shaft angle, loft angle, projected ball angle, and club head speed. Pitch and lob shots were distinguished by ball position, club shaft angle, loft angle, vertical force distribution, projected ball angle, and club head speed. For the lob shot, the ball was positioned about 6 cm toward the left foot from the center of the heel marker, compared to the ball position in the pitch shot for the 20 and 30 m shots. In addition, the loft angle was 10° wider and the vertical force of the right foot was 4% greater than for the pitch shot. The projection angle of the ball for the 30 m lob shot was 57°, while that for the pitch shot was about 47°. Taken together, the within-player between-task design and the realistic well-practiced goal-directed experimental tasks provided an opportunity to determine how individual players modify their control strategies to regulate shot distance and ball trajectory when using the same club. These findings have practical implications for coaches and for golfers aiming to improve their short game ability.

Effects of Foot Type and Ankle Joint Fatigue Levels on the Trajectories of COP and COM during a Single-Leg Stance

The purpose of this study was to investigate the effects of foot type and ankle joint fatigue levels on the trajectories of center of pressure and center of mass during a single-leg stance. The study subjects included 24 healthy women (normal foot group, n=10; pronated foot group, n=14). Ankle joint muscle fatigue was induced by using an isokinetic dynamometer, where the fatigue levels were measured on plantar flexion and dorsiflexion at angular velocities of 30°/s at 50% and 30% of the peak torque of ankle plan- tar flexion. Following assessments in the anteroposterior direction according to the level of fatigue, the pronated foot group showed decreased single-leg stance ability at 50% and 30% of the fatigue level. Moreover, the normal foot group showed better single- leg stance ability than the pronated foot group at 30% of the fatigue level. Following assessments in the mediolateral direction, we noted that the single-leg stance ability did not differ significantly according to the levels of fatigue or foot type. In conclusion, ankle plantar flexion at 50% and 30% of the peak torque reduced the ability of the pronated foot group to achieve a single leg stance in the anteroposterior direction. Moreover, the normal foot group showed better single-leg stance ability than the pronated foot group.