Chien Ju Lin

BIOMECHANICS OF WHEELCHAIR PROPULSION

With progress of modern technology, manually-propelled wheelchairs are still of importance for individuals with mobility impairments. The repeated wheelchair propulsion and strenuous daily activities cause high loads and thus injuries on the upper extremity joints. Over the past few years, a considerable number of studies have been made on biomechanical analysis of wheelchair propulsion and wheelchair-related activities. Thorough investigation of biomechanics during wheelchair propulsion enhances comprehension of mechanism of injuries and provides information to improve wheelchair design and fitting. Numerous investigations have been made to demonstrate factors which cause low effectiveness of force application and inefficiency of movements. Emphasis was also placed on developing analytical models to simulate wheelchair propulsion.

MULTIJOINT COORDINATION OF LOWER EXTREMITY IN TAI CHI EXERCISE

The goal of this study was to investigate the movement coordination among the hip, knee, and ankle joints during solo performance of the Tai Chi (TC) basic movements in order to understand its dynamic postural control. Nine male community-dwelling adults with experienced TC pushing hands participated in this cross-sectional study. The Eagle® motion analysis system with eight cameras was used to collect the trajectories of all reflective markers at sampling rate 100 Hz while the subject performed the ward-off, rollback, press, and push movements. Motion among the hip, knee, and ankle joints was highly coupled. Coupled joint motion, hip flexion-knee flexion-ankle dorsiflexion or reverse, existed in ward-off, rollback, and press phases for the front leg. However, in the push phase, the hip joint angle was kept almost constant with coupled knee and ankle motions. For the rear leg, coupled motion existed between the hip and the knee joints only. The ankle joint motion differed between the front and the rear legs during the basic movements of TC (p < 0.05). Basic characteristics were documented such as the forward knee never extending further than forward toe and both legs maintaining flexion during the full exercise cycle with hip and knee of front and rear legs having synchronized movements in opposite directions. The forward and backward shifts of TC basic movements have considerable contributions to the posture control in terms of the fine coordination of three lower extremity joints. This information could improve training protocol design for TC Chuan teaching and help beginners make an efficient and less damaging movement.

GROUND REACTION FORCE AND POSTURAL ADAPTATION OF THE PUSH MOVEMENT IN TAI CHI

INTRODUCTION The basic principles of Tai Chi Chuan (TCC) are the same in spite of several different schools or styles [1]. For increasing ones skill, Tai Chi is practiced from single action to a complete boxing frame and learned from a single-practitioner practice to push-hands, two-person training. The push-hands in TCC is an important skill to make the opponents lose their own balance while practitioners still maintain the stability through changing defensive positions without losing ground. How do Tai Chi (TC) practitioners sense and adapt themselves to their opponent’s demands without losing their root? The purpose of this study was to investigate postural stability in terms of ground reaction forces during pushing hands in Tai Chi.

Comprehensive simulation on morphological and mechanical properties of trigger finger – A cadaveric model

Trigger finger has long been a common disorder in hand orthopedics. To clarify the unknown causative factors regarding the disease, numerous experiments were done on human cadavers, including tendon forces, tendon moment arm, mechanical properties of the pulley, gliding resistance, etc. However, most of these studies were conducted on normal fingers. As the etiology of trigger finger is still controversial on whether it is an outcome of tendon nodule or pulley scarring, in this study, a trigger finger model was built combining both the nodule created by silicone gel injection and pulley constriction by external compression. Indentation and gliding resistance tests were performed on cadaveric specimens to verify the model. Results showed that after silicone gel injection into the tendon, a significant increase in thickness was found. In addition, no significant difference was found in the toe region compressive modulus of the tendon after injection. Moreover, maximum, drop of gliding resistance and work of extension were all found to be significantly larger as the severity of triggering increased. Our results indicated we have developed a feasible cadaver model simulating trigger finger nodule which could be utilized for further experiments to elucidate other causative factors and biomechanical features of trigger finger in the future.