Differences in Pivot Leg Kinematics and Electromyography Activation in Various Round House Kicking Heights.

The round house kick (RHK) is a common technique in taekwondo (TKD). The kicking action originates from the dynamic stability of the pivot leg. However, some knee injuries are caused by more difficult kicking strategies, such as kicks to the opponent's head. This study analyses the effects on TKD players in the lower extremity kinematic and neuromuscular reactions from different kicking heights. This study recruited 12 TKD players (age=20.3 ± 1.3 years, height = 1.72 ± 0.09 m, mass = 62.17 ± 9.45 kg) with no previous lower extremity ligament injuries. All athletes randomly performed 3 RHK at different heights (head, chest, and abdomen), repeating each kick 5 times. During the RHK action, the kinematics and muscle activations of the pivot leg were collected using six high-speed cameras and electromyography devices. The results found that during the RHK return period a high kicking position demonstrated larger knee valgus with the straight knee, and more hamstring activation on the pivot leg. The RHK pivot foot for TKD players encountered more risk of injury from high target kicking. The hamstring muscle played an important stabilizing role. It is recommended that sports medicine clinicians or sports coaches use this information to provide further protective injury prevention strategies.

Effects of land vs water jump exercise: Implications for exercise design targeting bone health.

PURPOSE: To quantify ground reaction force (GRF), osteogenic index (OI), muscle activity, and blood lactate levels during continuous jumping performed in water and on land. METHODS: Thirteen post-menopausal women (59.5 ± 6.8 years) performed two bouts of jumping, on land (LND) and in water at a depth of 1 m (WEX). Each 10-minute, 40-second bout consisted of 2 consecutive sets of squat, lunge, jumping jax, countermovement, and single legged jumps as intervals: 10 seconds maximal effort and 60 seconds recovery at 50% of heart rate reserve (HRR). Pre- and post-exercise lower extremity rate of perceived exertion (RPE) was recorded, and 10-µL earlobe blood samples were collected to assess lactate concentration. During exercise, data were collected for electromyography, GRF, and heart rate. Total GRF (TGRF) and total muscular activity (TMA) during each 10 seconds of jumping were measured. OI for one bout of continued jumps was determined by averaging GRF·ln (number of jumps + 1). RESULTS: There were no differences between WEX and LND for percent HRR and RPE. TGRF, OI, TMA, and lactate concentration on LND jumps were significantly higher than WEX. CONCLUSION: At similar cardiorespiratory and RPE levels, the lower impact loading of 10 minutes 40 seconds of interval continuous jumping exercise in 1-m depth was less osteogenic than on land. However, one daily bout of water jumping, 5 days per week resulted in a similar OI as 3 days of jumping on land. WEX might substitute or provide an adjunct to LND exercise to promote bone health.

Differences in kick-leg kinematics in various side-kick heights.

This study aims to explore the variation of lower extremity kinematic characteristics when elite taekwondo athletes perform the side-kick on protective gear placed at various heights. Twenty distinguished male national athletes were recruited and were asked to kick targets at three different heights adjusted according to their body height. A three-dimensional (3D) motion capture system was used to collect kinematic data. Kinematic parameters differences in the side-kick at three different heights were analyzed by using a one-way ANOVA (p < .05). The results revealed significant differences in the peak linear velocities of the pelvis, hip, knee, ankle, and centre of gravity of the foot during the leg-lifting phase (p < .05). Significant differences between heights were noted in the maximum angle of pelvis left tilting and hip abduction in both phases. In addition, the maximum angular velocities of pelvis left tilting and hip internal rotation were only different in the leg-lifting phase. This study found that, to kick at a higher target, athletes increase the linear velocities of their pelvis and all lower extremity joints of attacking leg in the leg-lifting phase; however, they only increase rotational variables on the proximal segment at the peak angle of the pelvis (left tilting) and hip (abduction and internal rotation) in the same phase. As an application in actual competitions, according to the opponent's body height, athletes can adjust both linear and rotational velocities of their proximal segements (pelvis and hip) and deliver into distal segements (knee, ankle, foot) linear velocity to perform accurate and rapid kicks.

Accelerometer-based prediction of ground reaction force in head-out water exercise with different exercise intensity countermovement jump.

BACKGROUND: Water jumping exercise is an alternative method to achieve maintenance of bone health and reduce exercise injuries. Clarifying the ground reaction force (GRF) of moderate and high cardiopulmonary exercise intensities for jumping movements can help quantify the impact force during different exercise intensities. Accelerometers have been explored for measuring skeletal mechanical loading by estimating the GRFs. Predictive regression equations for GRF using ACC on land have already been developed and performed outside laboratory settings, whereas a predictive regression equation for GRF in water exercises is not yet established. The purpose of this study was to determine the best accelerometer wear-position for three exercise intensities and develop and validate the ground reaction force (GRF) prediction equation. METHODS: Twelve healthy women (23.6 ± 1.83 years, 158.2 ± 5.33 cm, 53.1 ± 7.50 kg) were recruited as participants. Triaxial accelerometers were affixed 3 cm above the medial malleolus of the tibia, fifth lumbar vertebra, and seventh cervical vertebra (C7). The countermovement jump (CMJ) cadence started at 80 beats/min and increased by 5 beats per 20 s to reach 50%, 65%, and 80% heart rate reserves, and then participants jumped five more times. One-way repeated analysis of variance was used to determine acceleration differences among wear-positions and exercise intensities. Pearson's correlation was used to determine the correlation between the acceleration and GRF per body weight on land (GRFVLBW). Backward regression analysis was used to generate GRFVLBW prediction equations from full models with C7 acceleration (C7 ACC), age, percentage of water deep divided by body height (PWDH), and bodyweight as predictors. Paired t-test was used to determine GRFVLBW differences between values from the prediction equation and force plate measurement during validation. Lin's CCC and Bland-Altman plots were used to determine the agreement between the predicted and force plate-measured GRFVLBW. RESULTS: The raw full profile data for the resultant acceleration showed that the acceleration curve of C7 was similar to that of GRFv. The predicted formula was - 1.712 + 0.658 * C7ACC + 0.016 * PWDH + 0.008 * age + 0.003*weight. Lin's CCC score was 0.7453, with bias of 0.369%. CONCLUSION: The resultant acceleration measured at C7 was identified as the valid estimated GRFVLBW during CMJ in water.

Traditional Chinese acupressure massage ameliorates systemic inflammatory responses and joint mobility limitation after acute repeated jumping exercise.

CONTEXT: Alternative medical and training approaches to accelerate recovery among athletes are growing in popularity. The potential benefits of acupressure massage on attenuating muscle soreness and promoting post-exercise recovery capacity are still unclear. OBJECTIVE: This study compares the effects of traditional Chinese acupressure massage (TCAM) and active recovery, on subject recovery capacity after acute repeated jumping exercise. DESIGN: Twenty healthy male athletes were randomly assigned to traditional Chinese acupressure massage (TCAM; N = 10) or active recovery (AR; performing low-intensity exercise during post-exercise recovery; N = 10) groups. TCAM and AR intervention were applied after repeated jumping exercise. Pain scale, knee active/passive range of motion (AROM/PROM), jumping performance, quadriceps maximum voluntary contraction force, creatine kinase, and leukocyte subpopulations were measured at baseline, after and 48 h after exercise. RESULTS: No significant interaction effects were observed between the jumping performance, quadriceps maximum voluntary contraction (MVC) force, power-to-weight ratio for the two groups before the exercise, after the exercise, and 48 h post exercise. However, the knee flexion AROM/PROM was greater in the TCAM group than that for the AR group (p = 0.005). There were no differences in the VAS, MVC, and jumping performance between treatments. The white blood cell (p = 0.024), and monocytes (p = 0.023) responses were lower in the TCAM group. CONCLUSIONS: We demonstrated that TCAM generates beneficial effects on attenuating joint mobility limitations and lowering systemic inflammatory responses after acute exercise in athletes. These findings suggest that TCAM may be a practical alternative approach for athletes participating in consecutive competitions containing eccentric elements.