Pei-Hsi Chou

ELBOW LOAD DURING DIFFERENT TYPES OF BENCH-PRESS EXERCISE

The bench press is one of the most popular weight training open-kinetic chain exercise (OKCE) for the upper extremity. Reviewing the literature, there is a very little research regarding the biomechanical analysis of the OKCE of the upper extremity. The purpose of this study is to develop an OKCE testing model of the upper extremity by using the 3D Motion Analysis System. Furthermore, elbow joint loading of two different hand grip position during the bench-press exercise will be investigated. Thirteen male students volunteered for the study. Their average age was 26.1 years, with an average height of 170.6 cm, and an average weight of 70.3 kg. With both hands in neutral position, each subject was asked to perform bench-press type 1 (normal shoulder width), and bench-press type 2 (150% shoulder width). During the type 2 bench-press exercise, there is a significant increase in anterior–posterior and medial–lateral force on the elbow joint loading than the type 1 bench-press exercise. The valgus–varus, flexion–extension moment, and supination–pronation moment of the type 2 bench-press exercise are also greater than the type 1 bench-press exercise. As shown in this study, keeping the distance of both hand grips as shoulder width may reduce the elbow joint loading during bench-press exercise. These data will provide helpful information in clinical rehabilitation and treatment of the upper-extremity injures.

BIOMECHANICAL ANALYSES FOR THE EFFECTS OF ELBOW INITIAL FLEXION ANGLES ON UPPER EXTREMITY DURING A FALL

Elbow joint loading was evaluated during a forward fall at various elbow initial flexion angles, in order to determine which is the best elbow initial flexion angles to prevent the elbow injury during a fall. Subjects were asked to perform a forward fall and followed by a push-up motion in different elbow initial flexion angles: 0°, 20°, 40° and unrestricted group. Fall on the outstretched hand is the leading cause of upper extremity injury. There are far more extension type of supra-condylar fracture of the elbow than flexion type. Flexion of the elbow may represent the effects of damper and spring. Using the motion analysis system, the kinematics and kinetics of the elbow joint were investigated under various elbow initial flexion angles. The loading biomechanics of the elbow joint differed with various elbow initial flexion angles. The ground reaction forces decrease with increase of elbow flexion upon impact. Different initial elbow flexion angles would affect the biomechanics of upper extremities during falls. Forward fall with elbow in extension is more dangerous. Knowledge of elbow kinematics and kinetics may be helpful in preventing injuries by reducing the ground reaction force with changes of the elbow initial flexion angles during a fall.

COMPARATIVE ANALYSIS OF ELBOW JOINT LOADING IN PUSH-UP AND BENCH-PRESS

Upper extremity pain and dysfunction are common orthopedic problems in individuals who practice physical activities involving the upper limbs. Push-ups (PUs) and bench-presses (BPs), representing closed kinetic chain (CKC) and open kinetic chain (OKC) exercises, respectively, are among the most popular training exercises for the upper extremity in sports training and clinical rehabilitation applications. Utilizing a self-developed exercise testing model, the present study examines the difference in elbow joint loading between OKC and CKC exercises of the upper extremity. As many as 15 physically healthy male subjects with an average age of 19.8 years (S.D. 1.4), an average height of 176.8 cm (S.D. 4.2), and an average weight of 69.27 kg (S.D. 5.0) were studied. Each subject was asked to perform two different types of exercise, namely PUs and BPs. The kinematics, kinetics, and muscle activation of the elbow joint were calculated and analyzed using laboratory-developed motion analysis procedures. The PU exercises result in a greater loading on the elbow joint than the BP exercises, but produce a lower muscle activation. OKC exercises yield a greater muscle strengthening effect than CKC exercises. The increased shear stress on the elbow joint should be carefully noted when performing PU exercises. The results presented in this study provide valuable information for treatment and rehabilitation purposes in clinical applications.

Kinematical strategy to regain balance during a forward fall on a slippery floor

Slips and falls often occur in the industrial environments. They are not only caused by environmental hazards but also by some biomechanical factors related to deficient ability of postural control to arrest impending falls. The purpose of this study is to simulate the slip condition in human walking and to find out the possible related factors of biomechanics. Eleven male and 9 female recruited were healthful without any musculoskeletal and neurological impairments. In order to provide different disturbance level, three lean angles of tilting boards were designed as 10, 20, 30 degrees with respect to horizontal plane. Subjects wore a safety harness, stood on the tilting board and were released without awareness. A forceplate applied a soap patch was in front of the tilting board to serve the slippery perturbation and to measure the fool/floor reactions. Movements of body segments were measured using the motion analysis system. The results were shown that lean angle had a significant effect to all parameters except step length, response time, maximum ankle forward velocity, hip forward velocity, and ankle flex angle. The gender significantly affected on the step length, response time, maximum ankle forward velocity, and knee forward velocity. Larger lean angle made subjects to take a more rapid step. In order to absorb the shock in foot strike, subjects flexed more their knee and increased the foot landing angle in larger lean angle. Male tended to adopt the long step-length strategy to respond to the slippery perturbation and female tended to use the short step-length strategy instead. The results of maximum ankle forward velocity suggested that short step-length strategy could be belter to reduce the foot slip than long step-length strategy.

NORMAL GAIT OF CHILDREN

The rapid development of gait analysis and its increasing application to pathological gait in children has created an urgent need for normative data. However, research on maturation of gait in children is just in the beginning stage in Taiwan. In order to care for the welfare of children, more data and knowledge in the field are mandatory. The first goal of this study is to offer some background data and basic studies to any other researchers who are interested in this topic. The second goal was to investigate the corresponding factors to gait parameters, such as body weight, height, angular deformities (genu varum and valgum) and torsional deformities (toe in and out). In this study, twenty-three children (five years old in average) were included and motion analysis and force plate system were applied to investigate the kinematics and kinetics of lower limbs. The results showed that body height and weight are both corresponding factors to gait development. Gait analyses revealed that there were no differences between boys and girls. Children with genu valgum attend to more gait stability using compensatory mechanism.

BIOMECHANICAL ANALYSES OF STRESS DISTRIBUTION WITHIN THE SEATED BUTTOCK AND CUSHION

The elderly wheelchair users frequently encountered the prevalence of pressure sore, also known as decubitus, since they have to be seated in the wheelchair for daily activities. The major cause induced the formation of pressure sore was that the soft tissues were over-stressed. The purpose of this study was to provide the information about internal stresses of soft tissues and establish a simplified finite element model to simulate the behavior of the interface between human buttock and cushion. Computational stresses were verified by comparing the buttock-cushion interface pressures, which was measured with Q.A. pressure pads. The displacement of the cushion was also validated with the experimental results of buttock measuring system. Two cushion geometries, fat and contoured, were adopted in this study to explore the effects on stress distributions. The results showed that the simplified finite element model was consistent with the experimental data. Contoured cushions had better stress distribution an...

THE BIOMECHANICAL ANALYSIS OF MYOSIN V IN MULTIPLE-PATHS MODEL

Myosin V, a two-headed motor protein, moves along actin filaments toward the positive end. Similar to other molecular motors, myosin V hydrolyzes Adenosine tri-phosphate (ATP) and releases its product to produce movement. This study proposes a multiple-paths model that considers the hydrolysis processes of catalytic sites at the two heads of myosin V as independent. The proposed model describes the myosin V transition process by seven states, with one load-dependent transition rate among these states. This model demonstrates how myosin V steps forward at different chemical reaction paths. This study also uses the enzyme kinetics to calculate the mean velocity. Stochastic processes are used to analyze the randomness as well. Analytical results reveal that the theoretical mean velocities, mean movement lengths, and randomness with various ATP concentrations under external load agree with the experimental data.

BIOMECHANICAL ANALYSIS OF CHAIR RISING IN THE PREGNANT WOMEN

There were so many changes in physiological and psychological aspects during pregnancy. Rising from a chair was an important functional activity of daily life. These changes impose postural demands and limit the performance of activities of daily living. The overall goals of this study were to quantify the effects of physiological change due to pregnancy on the performance of chair-rise and to analyze why some pregnant female have more difficulty with these tasks. Twenty-four pregnant women were included in this study to investigate the performance and possible related biomechanical factors of chair-rise. Body movements of these subjects were recorded using video-based motion analysis system. Three force plates were applied to obtain the ground reaction forces of foot, seat and armrest. Kinematics and kinetics data were analyzed to evaluate the angles and moments of the hip, knee and ankle joints. The result indicated that the maximum moment of the three joints occurred nearly in the beginning of extension phase. As the chair height increased, the maximum flexion angles decreased significantly at the hip, knee, and ankle joints. The chair height had great influence on knee joint and hip joint moments, but less on ankle joint. In the third stage (chair height: 65% KH), the maximum hip moment significantly decreased because of a remarkable increase in abdominal depth. In contrast to the hip moment, the maximum knee moment greatly increased. This result revealed the reason why pregnant female have more difficulty on the performance of chair-rise. Additionally, rising with the armrest for pregnant female would significantly decreased the maximum knee moment. This study suggested that pregnant female should select armrest or higher chair to decrease the joint loading during chair-rise.

The dynamics of balance control during slipping

This study investigates experimentally the velocity of the center of mass with respect to the base of support while subjects step on slippery flooring. The moments of the joints of both legs are also investigated to gain further insights into the source of any correlation found in reacting to slippery perturbation. Twenty-two healthy subjects dressed with safety harness walked first without and then with slippery perturbation, guided by a metronome at 120 steps/min and 90 steps/min cadence. Data were collected from a motion analysis system and force plates. Subjects falling had distinguishably slower velocity of center of mass with respect to the lead stance foot compared to the subjects maintaining balance at contralateral toe off. Larger knee flexion moment and ankle plantar flexion moment in the perturbed leg were found among subjects regaining balance. Faster velocity of center of mass with respect to base of support is noteworthy in subjects regaining balance from slippery perturbation. The response of lower extremities, especially about the thigh and leg in the lead stance limb, were important to improve the velocity of the center of mass with respect to base of support.

Biomechanical Analysis of Wrist Loading During Lifting Tasks

This study develops a kinematic/kinetic model to evaluate the effect of different handle angles on wrist loading during lifting task. An imaged-based motion analysis system is used to study the movement pattern, force and moment of the wrist joint among nine different handle angles. Six CCD cameras were used to record 3-D trajectories of limb-mounted markers based on the laboratory coordination system as defined by an 8-marker cube. Euler angles are used to describe the orientation of a distal segment reference frame relative to a proximal segment reference frame. Each segment of the upper extremities is regarded as a uniform rigid body with six degrees of freedom. The resultant loading of the wrist joints was determined using an inverse dynamic procedure. This study indicates that tool handles can be designed or selected to reduce manual loading and the potential for injury during tool use. The mean curve of joint force and moment provided consultations and understandings of the wrist loading during lifting task. In this study, handles that kept the wrist joints in a dorsiflexed and radial deviated position, showed significant reduction in stresses around the surrounding soft tissue.