Moon Jeong Kang

Identification of Muscle Forces and Activation of Quadriceps Femoris Muscles of Healthy Adults Considering Knee Damping Effects during Patellar Tendon Reflex

Most analytical models of the human body have focused on conscious responses. A patellar tendon reflex, a representative example of spinal reflexes, occurs without a neural command. Muscle forces and activation of the quadriceps femoris muscles in healthy adults during patellar tendon reflex are identified in this study. The model is assumed to move in the sagittal plane, and the thigh and the trunk are assumed to be fixed in a sitting position so that the shank can move similar to a pendulum. The knee joint is modeled as a revolute joint, and the ankle joint is modeled as a fixed joint so that the shank and the foot can be regarded as one rigid body. Muscle forces are calculated following the inverse dynamic approach. Kinematic data obtained from an experiment (Mamizuka, 2007) are used as input data. Muscle activations are identified using a Hill-type muscle model. The obtained simulation results are compared with experimental results for validating the model and the underlying assumptions. † Corresponding Author, hhyoo@hanyang.ac.kr C 2014 The Korean Society of Mechanical Engineers

Modeling of Stretch Reflex Activation Considering Muscle Type

Although the stretch reflex plays an important role in spasticity, so far the stretch reflex has not been sufficiently investigated. Previous stretch reflex activation models have some limitations, whereby they are not able to predict outcomes of some stretch reflex cases and do not consider uneven distribution of muscle length and stretch velocity on reflex activation. The purpose of this study was: 1) to develop a modified stretch reflex activation model employing a new muscle length threshold and weighting factors for slow-twitch fiber and fast-twitch fiber, and 2) to validate the model using pendulum experiments of the lower and upper limbs. The new muscle length threshold was defined using the optimal muscle fiber length. Based on the optimal fiber length, the new threshold allows for prediction of the stretch reflex activation at muscle lengths shorter than have been possible with previous models. The muscle type weighting factors realized unequal contributions between the muscle length and stretch velocity. We proved the validity of the proposed reflex activation model by using pendulum tests to induce patellar tendon and biceps brachii reflexes. Unknown parameters employed in the proposed model were obtained by minimizing differences in motion obtained with the proposed model and experiments. The proposed model can predict stretch reflex activation at shorter muscle lengths. In addition, the proposed model reflected nonhomogeneous characteristics related to the unequal contributions between muscle length and stretch velocity. As a result, patellar tendon and biceps brachii reflex phenomena were shown to be predicted more accurately in this study.

Analysis of Elbow Reflexes Using Activation Model for Stretch Reflex

삼두박근 반사는 인체 상지에서 발생하는 대표적인 신장반사이며 경추의 이상 등을 판단하는데 중요한 역할을 수행한다. 본 연구에서는 이를 생체역학적으로 해석하기 위하여 새롭게 정의된 신장반사해석 모델을 이용하여 해석적으로 상완 이두박근과 삼두박근의 근활성도 및 상완의 운동 정보를 예측하였다. 해석을 통해 예측된 운동 정보와 실험 결과가 같도록 하는 근활성도를 구하고, 이를 근전도 실험결과와 비교하여 해석 모델과 방법의 타당성을 검증하였다. 제안된 모델과 실험을 통해 얻은 관절의 각도들의 최소자승오차는 0.056 으로 기존의 모델을 사용하여 얻은 오차의 절반 수준이다. 이것은 제안된 모델이 실제 현상과 잘 부합한다는 것을 나타낸다.

Estimation of Human Lower-Extremity Muscle Force Under Uncertainty While Rising from a Chair

Biomechanical models are often used to predict muscle and joint forces in the human body. For estimation of muscle forces, the body and muscle properties have to be known. However, these properties are difficult to measure and differ from person to person. Therefore, it is necessary to predict the change in muscle forces depending on the body and muscle properties. The objective of the present study is to develop a numerical procedure for estimating the muscle forces in the human lower extremity under uncertainty of body and muscle properties during rising motion from a seated position. The human lower extremity is idealized as a multibody system in which eight Hill-type muscle force models are employed. Each model has four degrees of freedom and is constrained in the sagittal plane. The eight muscle forces are determined by minimizing the metabolic energy consumption during the rising motion. Uncertainty analysis is performed using a first-order reliability method. The one-standard-deviation range of agonistic muscle forces is calculated to be about 150–300 N. § 이 논문은 2014년도 대한기계학회 신뢰성부문 춘계학술대회 (2014. 2. 26.-28., 제주대) 발표논문임 † Corresponding Author, hhyoo@hanyang.ac.kr C 2014 The Korean Society of Mechanical Engineers 조영남 · 강문정 · 채제욱 · 유홍희 1148 P f : 수동요사가 발생시키는 수축력 φ : 우모각 t F : 건의 수축력 e : 건의 변형률