Sang-Kyoon Park

Dynamically adjustable foot-ground contact model to estimate ground reaction force during walking and running.

Human dynamic models have been used to estimate joint kinetics during various activities. Kinetics estimation is in demand in sports and clinical applications where data on external forces, such as the ground reaction force (GRF), are not available. The purpose of this study was to estimate the GRF during gait by utilizing distance- and velocity-dependent force models between the foot and ground in an inverse-dynamics-based optimization. Ten males were tested as they walked at four different speeds on a force plate-embedded treadmill system. The full-GRF model whose foot-ground reaction elements were dynamically adjusted according to vertical displacement and anterior-posterior speed between the foot and ground was implemented in a full-body skeletal model. The model estimated the vertical and shear forces of the GRF from body kinematics. The shear-GRF model with dynamically adjustable shear reaction elements according to the input vertical force was also implemented in the foot of a full-body skeletal model. Shear forces of the GRF were estimated from body kinematics, vertical GRF, and center of pressure. The estimated full GRF had the lowest root mean square (RMS) errors at the slow walking speed (1.0m/s) with 4.2, 1.3, and 5.7% BW for anterior-posterior, medial-lateral, and vertical forces, respectively. The estimated shear forces were not significantly different between the full-GRF and shear-GRF models, but the RMS errors of the estimated knee joint kinetics were significantly lower for the shear-GRF model. Providing COP and vertical GRF with sensors, such as an insole-type pressure mat, can help estimate shear forces of the GRF and increase accuracy for estimation of joint kinetics.

Effect of forefoot bending stiffness of badminton shoe sole on lower leg kinematics during match-like situations

While the subject number is low, barefoot running does not appear to strengthen foot structures. In fact, the FHB tendon was stiffer in traditionally shod runners. This difference may be related to loading as there appears to be a relationship between tendon stiffness and average running mileage in traditionally shod runners (see Figure 2). Even with a larger mileage range (20–80 miles/week), FHB tendon material stiffness for barefoot runners seems to have no relationship with average running mileage. The results of the current study do not support the idea that running in minimalistic footwear strengths foot structures. More subjects will be recruited to increase statistical power. Ideally, an experimental, longitudinal study will also be performed to test for causation.

Relationship between lower limb muscle strength, self-reported pain and function, and frontal plane gait kinematics in knee osteoarthritis

BACKGROUNDnThe relationship between muscle strength, gait biomechanics, and self-reported physical function and pain for patients with knee osteoarthritis is not well known. The objective of this study was to investigate these relationships in this population.nnnMETHODSnTwenty-four patients with knee osteoarthritis and 24 healthy controls were recruited. Self-reported pain and function, lower-limb maximum isometric force, and frontal plane gait kinematics during treadmill walking were collected on all patients. Between-group differences were assessed for 1) muscle strength and 2) gait biomechanics. Linear regressions were computed within the knee osteoarthritis group to examine the effect of muscle strength on 1) self-reported pain and function, and 2) gait kinematics.nnnFINDINGSnPatients with knee osteoarthritis exhibited reduced hip external rotator, knee extensor, and ankle inversion muscle force output compared with healthy controls, as well as increased peak knee adduction angles (effect size=0.770; p=0.013). Hip abductor strength was a significant predictor of function, but not after controlling for covariates. Ankle inversion, hip abduction, and knee flexion strength were significant predictors of peak pelvic drop angle after controlling for covariates (34.4% unique variance explained).nnnINTERPRETATIONnPatients with knee osteoarthritis exhibit deficits in muscle strength and while they play an important role in the self-reported function of patients with knee osteoarthritis, the effect of covariates such as sex, age, mass, and height was more important in this relationship. Similar relationships were observed from gait variables, except for peak pelvic drop, where hip, knee, and ankle strength remained important predictors of this variable after controlling for covariates.

The relationship between shoe torsion and athletic performance during badminton maneuvers

Torsion is defined as the relative movement between the forefoot and rearfoot along the longitudinal axis of the foot. It has been suggested that increased torsional movement between forefoot and rearfoot may reduce pronation of the foot and thus, reduce the risk of injuries during running (Stacoff et al. 1991). However, whether a large torsional movement would be beneficial for other sport activities is unknown. Badminton is characterized as a sport that requires highly intense activity with short rest pauses (Fahlstrom et al. 2002). During badminton, the foot experiences dynamic movement as it requires diverse foot-steps on the court (Wang et al. 2009). Currently, no study has investigated how torsional characteristics of the shoe influence athletic performance.

Do running speed and shoe cushioning influence impact loading and tibial shock in basketball players

Background Tibial stress fracture (TSF) is a common injury in basketball players. This condition has been associated with high tibial shock and impact loading, which can be affected by running speed, footwear condition, and footstrike pattern. However, these relationships were established in runners but not in basketball players, with very little research done on impact loading and speed. Hence, this study compared tibial shock, impact loading, and foot strike pattern in basketball players running at different speeds with different shoe cushioning properties/performances. Methods Eighteen male collegiate basketball players performed straight running trials with different shoe cushioning (regular-, better-, and best-cushioning) and running speed conditions (3.0 m/s vs. 6.0 m/s) on a flat instrumented runway. Tri-axial accelerometer, force plate and motion capture system were used to determine tibial accelerations, vertical ground reaction forces and footstrike patterns in each condition, respectively. Comfort perception was indicated on a 150 mm Visual Analogue Scale. A 2 (speed) × 3 (footwear) repeated measures ANOVA was used to examine the main effects of shoe cushioning and running speeds. Results Greater tibial shock (P < 0.001; η2 = 0.80) and impact loading (P < 0.001; η2 = 0.73–0.87) were experienced at faster running speeds. Interestingly, shoes with regular-cushioning or best-cushioning resulted in greater tibial shock (P = 0.03; η2 = 0.39) and impact loading (P = 0.03; η2 = 0.38–0.68) than shoes with better-cushioning. Basketball players continued using a rearfoot strike during running, regardless of running speed and footwear cushioning conditions (P > 0.14; η2 = 0.13). Discussion There may be an optimal band of shoe cushioning for better protection against TSF. These findings may provide insights to formulate rehabilitation protocols for basketball players who are recovering from TSF.

Effects of forefoot bending stiffness of badminton shoes on agility, comfort perception and lower leg kinematics during typical badminton movements

Abstract This study investigated whether an increase in the forefoot bending stiffness of a badminton shoe would positively affect agility, comfort and biomechanical variables during badminton-specific movements. Three shoe conditions with identical shoe upper and sole designs with different bending stiffness (Flexible, Regular and Stiff) were used. Elite male badminton players completed an agility test on a standard badminton court involving consecutive lunges in six directions, a comfort test performed by a pair of participants conducting a game-like practice trial and a biomechanics test involving a random assignment of consecutive right forward lunges. No significant differences were found in agility time and biomechanical variables among the three shoes. The players wearing the shoe with a flexible forefoot outsole demonstrated a decreased perception of comfort in the forefoot cushion compared to regular and stiffer conditions during the comfort test (p < 0.05). The results suggested that the modification of forefoot bending stiffness would influence individual perception of comfort but would not influence performance and lower extremity kinematics during the tested badminton-specific tasks. It was concluded that an optimisation of forefoot structure and materials in badminton shoes should consider the individual’s perception to maximise footwear comfort in performance.

Influence of pilates training on the quality of life of chronic stroke patients

[Purpose] This study was to observe the influence of Pilates training on the quality of life in chronic stoke patients. [Subjects and Methods] Forty chronic stroke patients participated in this study. They were divided into same number of experimental group (EG) and control group (CG). EG participated in a 60-min Pilates training program, twice a week for 12 weeks, while the CG did not participate in any exercise-related activities for the duration and participating in general occupational therapy without any exercise-related activities. Then the MMSE-K was performed before and after Pilates training to observe the influence of Pilates training on the quality of life in chronic stroke patients. [Results] Statistically significant improvement in the physical, social, and psychological domains was found in EG after the training. No statistically significant difference was found in all three quality of life domains for the CG. EG experienced a statistically significant improvement in all quality of life domains compared with that of CG. [Conclusion] Therefore, participation in Pilates training was found to effectively improve the quality of life in stroke patients. Pilates training involves low and intermediate intensity resistance and repetition that match the patient’s physical ability and can be a remedial exercise program that can improve physical ability and influence quality of life.

A new approach to quantify the centre of pressure (COP) trajectory using a shoelace formula as a potential measure of movement control during walking and running

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Tibial accelerations and ground reaction forces in basketball shoes from different landing heights

Tibial accelerations and ground reaction forces in basketball shoes from different landing heights Wing Kai Lam*, Jeonghyun Woo, Jacobus Noel Liebenberg, Jason Cheung, Professor Jiseon Ryu, Sukhoon Yoon and Sang-Kyoon Park Li Ning (China) Sports Goods Co., Ltd, Sports Science Research Center, Beijing, China; Motion Innovation Centre, Korea National Sport University, Seoul, South Korea; Li Ning Sports Science Research Center, Beijing, China; Institute of General Kinesiology and Athletic Training, University of Leipzig, Leipzig, Germany; Sport Science Institute, Korea National Sport University, Seoul, South Korea