Hwai-Ting Lin

Three-dimensional characteristics of neck movements in subjects with mechanical neck disorder

STUDY DESIGN Controlled laboratory study. OBJECTIVES To examine characteristics of neck movement at three-dimensional planes for subjects with mechanical neck disorder (MND) and measure cervical range of motion, coupling motion, and calculation of the upper cervical rotation ratio. BACKGROUND MND is characterized by symptoms of neck pain, headache, dizziness and limited range of motion (ROM). However, the characteristics of neck movements across the three-dimensional planes in MND patients remain unknown. METHODS Forty participants were recruited, which consisted of twenty-seven subjects with MND and 13 healthy subjects. A three-dimensional electromagnetic motion capture device with custom data analysis software was used to measure the neutral position of the neck and the range of motion of upper and lower cervical spine. RESULTS The results indicate that subjects with MND had significantly decreased ROM in right rotation (p< 0.05) and extension (p< 0.05) movements compared to the healthy group. Increased coupling motion (p< 0.05) in the rotation plane during cervical flexion was also found in the MND group compared to control group. For rotations in neutral or in flexion positions, rotation to the right showed smaller range of motion compared to rotation to the left. CONCLUSION In this study, MND was associated with altered cervical movement patterns with increases in coupling motion. The findings may help to differentiate MND from whiplash-associated disorder. Increasing upper cervical spine rotation mobility may be crucial for treating deficiencies in neck rotation in patients with MND.

Use of Virtual, Interactive, Musculoskeletal System (VIMS) in Modeling and Analysis of Shoulder Throwing Activity

Our purpose in this study was to apply the virtual, interactive, musculoskeletal system (VIMS) software for modeling and biomechanical analysis of the glenohumeral joint during a baseball pitching activity. The skeletal model was from VIMS library and muscle fiber attachment sites were derived from the visible human dataset. The muscular moment arms and function changes are mainly due to the large humeral motion involved during baseball pitching. The graphic animation of the anatomic system using VIMS software is an effective tool to model and visualize the complex anatomical structure of the shoulder for biomechanical analysis.

Complex chain of momentum transfer of body segments in the baseball pitching motion

Abstract Baseball pitching requires contributions from and interaction among all limb segments. Most previous investigators have concentrated on the throwing arm itself, but the center of mass (COM) and contribution of all segments in the pitching motion have not been studied. The purpose of this study was to investigate the momentum transfer of all body segments in the pitching motion. The kinematics pitching motion data were captured from three experienced pitchers (one is professional, two are amateurs). A ten‐segment body system was modeled in this study. The results showed that the lowest position of the COM during the pitching cycle occurred around the ball release time and the fastest velocity (2.81±0.18 m/sec) of the COM was in the late cocking phase. The trunk and thigh on the throwing side showed the largest linear momentum among all segments in the late cocking phase. The upper throwing arm and forearm had peak linear momentum in the acceleration phase. The trunk also had the largest angular momentum during the pitching cycle and reached the maximum rotational momentum (4.17±1.22 Kg‐m2/sec) in the late cocking phase and medial bending momentum (9.03±5.78 Kg‐m2/sec) at the end of the late cocking phase. From the time sequence of linear momentum changes, especially in the leading direction, the force transfer from the foot to the trunk then through the upper extremity during the pitching motion was identified. The largest change rate of angular momentum found in the trunk meant that the trunk contributed the largest torque in the pitching motion. Better coordination of the body segments in the pitching motion not only enhances performance but also avoids injury. The coordination of motion by athletes in the pitching motion provides a guideline for better coaching and training.

EFFECT ON PLANTAR PRESSURE DISTRIBUTION WITH WEARING DIFFERENT BASE SIZE OF HIGH-HEEL SHOES DURING WALKING AND SLOW RUNNING

High heeled shoes may alter the regular loading pattern of the plantar pressure, especially increased in the forefoot area. Walking with narrow base of high heeled shoes may induce the brisk acceleration of the supported leg due to instability that increases the force on the plantar area. Particularly, this phenomenon may be amplified while slow running, but never been investigated. Materials and Methods: Plantar pressures were measured for different specific area of foot using the Pedar-X system. The effects on plantar pressure with different sized bases (1.2× 1.2 cm2 and 2.2 × 3.5 cm2) of high-heeled shoe (7.8 cm in height) were examined while walking in thirteen healthy female subjects and during slow running in nine healthy female subjects. Results: The plantar pressures of the hallux and toe while wearing narrow base high heel were significantly (p < 0.05) greater than those when walking with wearing wide base one. For both narrow and wide base heels, significantly increased (p < 0.05) plantar pressure were found in the medial forefoot while slow running at 2.0 m/s as compared with walking at 1.0 m/s and 1.5 m/s. While slow running with wearing narrow base high heel indicated significantly (p < 0.05) increased plantar pressures in the medial, central and lateral forefoot and toes regions compared with those with wearing wide base one. Conclusion: The findings suggest that if individuals have to wear high heeled shoes, it would be better to select one with a wide based heel to avoid running in at any circumstance.

EFFECTS OF SPEED AND INCLINE ON LOWER EXTREMITY KINEMATICS DURING TREADMILL JOGGING IN HEALTHY SUBJECTS

Recently, there are more people jogging with a treadmill at the gym or the home setting. The main available selected modes for treadmill jogging are speed and slope of incline. Increased speeds and incline slopes will not only increase the cardiopulmonary loading but may also alter the lower extremity (LE) movement patterns. There are few systematic investigations of the effect of the speed and incline on LE kinematics. Most studies have used 2D methods which focused on movements in sagittal plane only and this has limitations in the acquired data since lower extremity movements also include frontal and transverse planes. The current study aimed to investigate LE movement during jogging at different speeds and incline slopes using a high speed three-dimensional (3D) motion analysis system. Eighteen young healthy males were recruited. The video-based motion capture system with six CCD cameras, HIRES Expert Vision System (Motion Analysis Corporation, CA, USA), was used to collect kinematic data at a sampling frequency of 120Hz. Nineteen passive reflective markers were attached to bilateral lower extremities of the subject. The joint angle is calculated by Euler angle using the rotation sequence: 2-1-3 (y-x′-z″). Four speeds were selected: 2 m/s, 2.5 m/s, 3 m/s, 3.5 m/s with the slope at 0, and four slopes were selected: 0%, 5%,10%,15% at a speed of 3 m/s. Repeated-measures ANOVA was used to test hypotheses regarding changes in jogging condition on LE kinematic variables. The significance level was set at 0.05. As the jogging slope increased, the hip, knee and ankle demonstrated a significantly greater maximum flexion in swing phase (p<0.001), but the maximum extension angles in stance phase were relatively unchanged. Increased LE flexion during swing phase is important to ensure foot clearance with increased slope. For increased speed, the hip and ankle joints had significantly greater maximum joint extension angles during stance phase and the hip and knee joint had significantly larger maximum flexion angles in swing phase (p<0.001). Increased motion during swing phase account for a larger step length and increased motion during stance phase may facilitate the generation of power during forward propulsion as the jogging speed increased. As the slope and speed increased, LE movement patterns were changed in the transverse plane: the significantly increased (p<0.01) internal hip rotation at terminal stance, the increased toe-in of foot (p<0.001) during terminal stance phase and decreased (p<0.05) toe-out during swing phase. Increased hip motion in transverse plane could lengthen the stride distance and increase foot toe-in for providing a stable lever for push off to increase propulsion force as speed or slope is increased. By way of systematic 3D kinematic investigation of the LE in jogging, the results further elucidate the effect of changing speed and incline on LE joints movements. This information could provide guidelines for rehabilitation clinicians or coaches to select an appropriate training mode for jogging.

EMG AND PLANTAR PRESSURE PATTERNS AFTER PROLONGED RUNNING

The aim of this paper is to investigate the effect of prolonged running on lower limb muscle activity, foot pressure and foot contact area. The treadmill running test was performed at a running velocity of 12 km/h for 20 minutes. Twenty-nine male students from the Army Infantry School took part in this study. For all subjects in our study, a number of variables were analyzed by the prolonged running. The EMG variables included the signal maximum amplitude of EMG linear envelope of all the muscles. Meanwhile, maximal forces and peak foot pressures in 10 anatomically defined areas of the foot, and contact area of the whole foot were analyzed. Running EMG data in each of the phases (phase 2–4) were compared to those at the beginning of the run (phase 1). Dynamic pedography data in phase 4 was compared to those of phase 1. Pedography analysis revealed a significant increase in the maximal forces and peak pressures under the medial midfoot and all forefoot regions. From phase 1 to phase 4, the maximal force increased by 32% under the medial midfoot, 29% under the first metatarsal, 34% under the second and third metatarsal, and 21% under the fourth and fifth metatarsal. The peak pressure under the medial midfoot increased by 19%, under the first metatarsal increased by 21%, under the second and third metatarsal increased by 31%, and under the fourth and fifth metatarsal increased by 21%. The averaged maximum EMG amplitudes of almost all the muscles were increased gradually as time increased. Among them, rectus femoris, gastrocnemius, soleus, and tibialis anterior muscles reach a significant amplitude at the p < 0.05 level. In conclusion, our results showed that a prolonged running under a 20 minutes limitation led to a greater increase in muscle amplitude, midfoot and forefoot loading compared with the beginning of running.

Characteristics of the Motor Units during Sternocleidomastoid Isometric Flexion among Patients with Mechanical Neck Disorder and Asymptomatic Individuals

Mechanical neck disorder is a widespread and non-neurological musculoskeletal condition resulting from modern lifestyles. Presently, the fundamental electrophysiological properties of the motor units of the sternocleidomastoid muscles and the characteristics of the short-term synchronization of the motor unit in patients with neck pain are ambiguous. This study therefore aims to clarify the fundamental electrophysiological properties of the motor units of the sternocleidomastoid muscles in patients with mechanical neck disorder and in asymptomatic individuals. We further investigated whether alterations in the degree of motor unit short-term synchronization occur. The surface electrophysiological signals of the bilateral sternal heads of the sternocleidomastoid muscles of twelve patients with mechanical neck disorder and asymptomatic individuals were detected at 25% of the maximum voluntary contraction during cervical isometric flexion and then decomposed into individual motor unit action potential trains. We found that the patients with mechanical neck disorder showed significantly higher initial and mean firing rates of the sternocleidomastoid muscles and displayed substantially lower motor unit short-term synchronization values compared with the asymptomatic subjects. Consequently, these convincing findings support the assertion that patients with mechanical neck disorder display altered neuromuscular control strategies, such as the reinforcement of motor unit recruitment firing rates in the sternocleidomastoid muscles. The motor units of these patients also revealed neural recruitment strategies with relatively poor efficiency when executing the required motor tasks.

THE ACUTE EFFECT OF TRAINING FREQUENCIES AND NUMBER OF SETS OF WHOLE BODY VIBRATION ON KNEE JOINT PROPRIOCEPTION

Whole body vibration affects neuromuscular systems through the stimulation of receptors in muscles and tendons. This study investigated the acute effects of different training intensities of WBV on knee joint proprioception. A total of 18 untrained males participated in this study. Joint position sense was tested as an index of joint proprioception ability. Frequencies of 20, 35, and 50 Hz with two mm of displacement vibration training were tested. Each frequency was tested in different numbers of sets (four, six, eight, and ten sets). As it turned out, the results indicated a significant improvement in active JPS at 35 Hz for all testing sets, and only at 20 Hz with ten sets. As for passive JPS, significant improvements were obtained only at 35 Hz with ten sets of training. WBV training affected knee joint proprioception in active JPS with shorter vibration exposure at lower frequencies and amplitude. Coaches, athletes and physical therapists should consider using WBV training for its potential benefits in warm-ups and rehabilitation.

Motor Learning of Normal Subjects Exercised with a Shoulder-Elbow Rehabilitation Robot

A shoulder-elbow rehabilitation robot has been developed as clinical treatments to facilitate motor learning and accelerate recovery of motor functions for stroke patients. However, the connection between motor learning and muscle activation patterns for stroke patients remained unknown. This study was tried to fulfill the gap by examining the muscle coordination and motor learning strategies of normal subjects while they interacted with the rehabilitation robot. A Hill-type biomechanical model based on twelve shoulder and elbow muscles was hence constructed for the upper-limb to simulate the interaction. Two normal subjects were recruited to perform upper limb circular tracking movements, clockwise and counterclockwise, on transverse plane at shoulder level in a designed force field generated by the rehabilitation robot. From the inverse dynamics analysis, the interaction was analyzed and the patterns of muscle activation were calculated. EMG signals of eight upper limb muscles were also measured for model validation and muscle coordination observation. The principle component analysis (PCA) was performed to distinguish different groups of muscle co-activation. Results showed that the constructed biomechanical model may be used as a tool for evaluating effects of treatment and be utilized as a blueprint for the design of the training protocol for the stroke patients.

KINEMATIC WRIST AND THUMB POSTURE ANALYSIS OF SCHOOL CHILDREN DURING THE MANIPULATION OF THE MOUSE

The wrist and thumb postures adopted during the use of three different types of computer mouse (mini mouse; standard mouse; MouseMan) to perform eight standardized tasks were evaluated. Thirty elementary students between seven to twelve years of age were studied using a magnetic tracking system. The peak value and angular range of motion of the wrist and thumb extension/flexion and radial/ulnar deviation were measured during performing 8 standard tasks. There were statistically significant larger values in the standard mice with regard to extreme wrist extension. Angular range of wrist extension observed for the standard mice were also much higher than the mini mouse and MouseMan. There were statistically significant larger values in the MouseMan with regard to extreme wrist ulnar deviation, and an average decrease in extreme thumb flexion and angular range of thumb flexion. The results from the questionnaire showed that most elementary students preferred to use the standard mouse (40%) next was the MouseMan (37%); and the last the mini mouse (23%). The recommendation of mouse types based on the hand length for elementary students was not statistically significant in our study.