Sukhoon Yoon

The Influence of Short-term Aquatic Training on Obstacle Crossing in Gait by the Elderly

[Purpose] The purpose of this study was to examine the fall-prevention effect of 12 weeks of aquatic training for the elderly using variables representative of the relationship between the trailing foot and an obstacle. [Subjects] Ten healthy elderly participants, who lived in C city, (age: 77.15±5.21 yrs, height: 149.87±3.54 cm, body mass: 57.44 ±6.74, and BMI: 25.58±2.98 kg/m2), participated in this study. [Methods] To determine the effect of 12 weeks’ aquatic training, 3-D motion analysis with 7 infrared cameras and one force plate, was performed. [Results] TC, HC, MVHC, and CV significantly increased after intervention. For the all gait stability parameters, statistically significant training effects were found. [Conclusion] In conclusion, 12 weeks’ aquatic exercise can help the elderly become more stable when crossing a height obstacle, which is the most frequent cause of falls by the elderly.

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.

An 8-week Aquatic Exercise Program is Effective at Improving Gait Stability of the Elderly.

[Purpose] The purpose of this study was to investigate the effect of 8 weeks aquatic exercise on the gait stability of the elderly using dynamic factors: center of mass (COM), velocity of center of mass (COMV), and center of pressure (COP). [Subjects] Eleven elderly participants (age: 77.18 ± 4.96 yrs, height: 149.48 ± 3.61 cm, body mass: 56.94 ± 6.62 kg, and leg length: 82.36 ± 2.98 cm), participated in this study. [Methods] To identify the 8-week aquatic training effect, 3-D motion analysis with 7 infrared cameras and one force plate, was performed. [Results] For the COM-COP inclination angles, significantly decreased medial inclination angles were shown in both the posterior and anterior swing phases. For the COMV-COP inclination angles, decreased medial inclination angles were shown in both the posterior and anterior swing phases, but significant difference was found only in the posterior phase. [Conclusion] The results suggest that 8 weeks aquatic exercise is effective at improving the gait stability of the elderly. Further studies should extend the training period to gain statistically significant results for the effect of aquatic exercise in the anterior-posterior direction.

Comparisons between Skilled and Less-Skilled Players` Balance in Hakdariseogi

The purpose of this study was to investigate the balance differences between skilled players and less-skilled players during Hakdariseogi motion of Keumgang Poomsae in Taekwondo. To achieve the study goal, total of 10 Taekwondo athletes; 5 skilled players(S, body mass: kg, height: cm, age: yrs) and 5 less-skilled players(LS, body mass: kg, height: cm, age: yrs) participated in this study. A three-dimensional motion analysis with 8 infrared cameras and one force plate whose sampling frequency as 30 Hz and 300 Hz, respectively, were performed. Participants` motion were divided into three phases which were preparation phase(P1), performing phase(P2) and maintaining phase(P3). The range and velocities of COP, the range and RMS of ground reaction torque and displacement between COM and center of BOS of each phase were computed. In this study, at P1 and P3 which were double and single stance, respectively, the range and M-L velocities of COP revealed significantly higher in LS compared with those of S(p

Evaluation of Gait Stability using Medio-Lateral Inclination Angle in Male Adults

Human body is hard to be in perfect balance during walking. Most of time the trunk is supported by one leg and the center of mass(COM) falls to the contralateral side. Thus, dynamic variables such as the velocity of the COM should be considered when gait stability is evaluated. The purpose of this study was to investigate whether the extrapolated center of mass(XCom) which utilized the COM position and its velocity, is appropriate to evaluate gait stability. Ten healthy adults participated in this study and performed 3 different types of gaits(normal(NG), hands on waists(HWG), and hands on shoulders(HSG)) onto 4 different types of obstacle(obstacle height: 0%, 30%, 40% and 50% of leg length). Medio-lateral Com-CoP and XCom-CoP inclination angle were calculated during support phase. For all condition, greater M-L XCoM-CoP inclination angles were found(p

Evaluation of the Elderly Gait Stability Using the Center of Mass and Center of Pressure Inclination Angles

The gait instability in the elderly has been associated with age-related deterioration in physical strength and reducing the potential for elderly falls requires regular exercise. In 2005, National Center for Injury Prevention and Control(NCIPC) reported that most elderly falls occur during activities in daily living(ADL). To better reveal biomechanic mechanisms underlying age-related degeneration in gait stability, and to enhance the assessment of falls risk, an accurate quantification of a person`s balance maintenance during locomotion is needed. Instantaneous orientation of the line connecting COP and COM can characterize whole body position with respect to the supporting foot during gait and the angle between this line and the vertical line passing through the COP known as a good assessment to detect the elderly gait instability. Therefore the purpose of this study was to investigate a 6-month walking exercise effects in reducing elderly fall risk factors by using COP-COM inclination angles. Twenty-two community-dwelling elderly participated this study. The participants performed a walking exercise(3 times/week, 1 hour/visit) for 6 months. Laboratory kinematics during walking was assessed at months 0, 3 and 6. Significant increased in gait velocity was found among periods(p

The Training and Detraining Effects of 8 Weeks of Water Exercise on Obstacle Avoidance in Gait by the Elderly

[Purpose] This study aimed to provide useful information for fall prevention for the elderly by investigating how safely the elderly cross an obstacle after 8 weeks water exercise, and how much of the training effect remained 8 weeks after finishing the exercise. [Subjects] Eleven elderly participants participated in this study. [Methods] To identify the training and detraining effect of 8 weeks of water exercise, a 3-D motion analysis with 7 infrared cameras and one force plate, was performed. [Results] In most of all variables, statistically significant training and detraining effects at obstacle heights of 30% leg length were found. At obstacle heights of 40% leg length, statistically significant training effects were found but only improvement pattern of detraining effects were found for all variables. [Conclusion] The findings of this study indicate that 8 weeks of water exercise at the level of RPE 12–13 may help the elderly to safely cross obstacles at the most common height associated with falls (30% of leg length) for at least 8 weeks after training termination. The training effect, however, should not be expected to last for 8 weeks after the training at obstacle heights of 40% height of their leg length, which is a more difficult height for the elderly to cross.

Comparisons of Foot Pressure Patterns between Experienced Skiers and Intermediate Skiers during Alpine Skiing

This study investigated foot pressure patterns between experienced skiers and intermediate skiers during alpine skiing. Five experienced skiers and five intermediate skiers participated in this study. Foot pressure measurement system was used to measure vertical ground reaction force (vGRF) and contact area under the six plantar regions. Each participant was asked to perform basic parallel turns and carved turns on a 18o groomed slope. Each right turn was divided into the initiation phase, the steering phase 1 and 2. For the initiation phase of the basic parallel turns, significantly greater contact area was found on the LRF and RRF of the intermediate skiers (p<.05) and significantly greater vGRF was found on the LRF of the intermediate skiers (p<.05). Also significantly greater vGRF and contact area were found on the LRF and RRF of the intermediate skiers at the steering phase 1 (p<.05) and on the LRF of the intermediate skiers at the steering phase 2 (p<.05). For the carved turns, significantly greater vGRF and contact area were found on the LRF and RRF of the intermediate skiers at all three phase (p<.05). On the other hand, significantly greater vGRF was found on the RFF of the experienced skiers at the steering phase 1 (p<.05). Also significantly greater vGRF and contact area were found on the RMF of the experienced skiers at the steering phase 2 (p<.05). In order to increase performance, we suggest that the intermediate skiers should be unweighted at the initiation phase and shift the body weight to the forefoot of the outer foot at the steering phase 1. Also, the outer ski should be loaded more than the both skis at the steering phase 1 and 2.

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.

Effects of a Water Exercise on the Lower Extremities Coordination during Obstacle Gait in the Female Elderly - Focusing on Training and Detraining Effects -

The purpose of this study was to investigate the training and detraining effects of a 8-week water exercise on lower extremities coordination during obstacle gait in the female elderly. Eight elderly participants (age: 76.58±4.97 yrs, height: 148.88±7.19 cm, body mass: 56.62±6.82 kg, and leg length: 82.36±2.98 cm), who stayed at the Seoul K welfare center, were recruited for this study. All participants had no history of orthopedic abnormality within the past 1 year and completed the aquatic exercise program which lasted for 8 weeks. To identify the training and detraining effect of 8 weeks of water exercise, a 3-D motion analysis with 7 infrared cameras and one force plate sampling frequency set at 100 Hz and 1,000 Hz, respectively, was performed. A two-way ANOVA was performed to find training and detraining effects among diferent obstacle heights. In this study significant level was set at .05. Significant training effects of LTS (lead foot thigh and shank) coordination in all obstacle height were found (p<.05). It is also found that the training effect of LTS remained 37%, 58%, and 25% in obstacle height of 30%, 40%, and 50%, respectively. Lead foot showed the greater detraining effect of coordination compared with trail foot, and SF (shank and foot) coordination revealed better detraining effects of coordination compare with TS (thigh and shank) in both feet. Based on the findings, a 8 week water exercise give an positive effects to the elderly in terms of segment cooperation which potentially helps reducing their accident falls. The magnitude of detraining may also help the elderly to find the retraining moment.