TAI CHI: MOVEMENT CHARACTERISTICS AND PREVENTION OF FALLS

In the recent guidelines released by the American Geriatrics Society and the British Geriatric Society Tai Chi is strongly recommended the exercise form for elderly people to prevent falls. Biomechanics is the most effective way to explain the underlying mechanism of Tai Chi in improving the balance stability and posture control. This article introduces the biomechanics studies reported in the last decades to explore the kinematics, kinetics and electromyography characteristics of Tai Chi movements. Through these studies the unique contribution of Tai Chi exercise to balance stability and posture control and subsequently prevention of falls has been better understood. This article also suggest that in order to understand the neurological basis of the effects of Tai Chi exercise on falls prevention, a Magnetic Resonance Image study should be conducted

BIOMECHANICS OF ORIENTAL MARTIAL ART: WHY PRACTICING TAl CHI CHUAN HELPS TO IMPROVE THE HUMAN BALANCE CONTROL

Four studies were devoted to explore the mechanism of why practicing Tai Chi Chuan (TCC) can improve balance control especially for elderly people. In the first study, it showed that foot stepping patterns of TCC were better than those of walking in simulating the gait challenges that may be encountered in daily activities. The second study found that the characteristics of plantar pressures in TCC movements not only enhances muscle strength, but also improves the somatosensory input and feedback in the great toe area to assist in balance control. The third study found that the elderly people who regularly practiced TC not only showed better kinesthesia in ankle and knee joints than sedentary controls, but also their ankle kinesthesia were better than the elderly regular swimmers/runners. In the fourth study the continuous shifting of the center of gravity (CG) and a wide range of motion (ROM) of lower extremity joints were found. The continuous alteration of muscle loading and contraction types produced different levels of muscle activity -vigorous contraction, moderate tension, or relaxation. All findings supported that TCC movement provides training possibility for proprioception and neuromuscular control, which made TC exercise to confer particular benefits for postural control

KINEMATICS AND ELECTROMYOGRAPHY OF TRUNK AND LOWER-LIMB DURING WALKING WITH NEGATIVE HEEL SHOES

A type of negative heel shoes (NHS) was designed for the purpose of training the muscles in trunk and leg. The negative heel shoes are characterized as having the heel section lower than the toe when the top of the shoe and the insole are removed. The shoe itself tilts the foot into about 10 degrees of dorsiflexion. It is noteworthy that the original objectives of the NHS designer were to build up and exercise the muscles in trunk and 'Iowerlimn as well as Achilles tendon. However, studies about the kinematics and muscle activities of trunk and lower-limb in walking with NHS are limited (Benz, et aI., 1998). And no scientific evidence supports that walking with the negative heel shoes benefits the muscle strength. The purpose of the present study was to investigate the kinematics and EMG activity in the muscles of trunk and lower-limb, as compared with walking with normal shoes. It is hoped that the results of this study will further the understanding of the effect of walking with NHS on biomechanical responses in humans

ANTROPOMETRIC FOOT MEASUREMENTS OF CHINESE ADULTS WITH DIFFERENT BMI

The purpose of this study was to examine whether foot shape was affected by different body weight levels in the same foot length. Foot shape data were collected from 476 male and 499 female subjects. Each gender was divided into two normal and overweight or obesity groups. The results showed that there are some differences in foot length, breadth, girth and height between different BMI groups in same foot size. Overweight or obese group have shorted fore foot length, longer girth length, larger foot breadth and larger size in some foot height. The results will help make shoe last and choose fitting shoe for overweight and obese group

APPLICATION OF PLANTER FORCE MEASUREMENT IN EVALUATION OF SOCCER SHOES

Normal soccer shoes are manufactured using homogenous material for midsole. Soccer game requires the players to tackle the soccer ball as quickly as possible. It was thought that a dual density material design of the midsole may provide better control to the foot. To study this question, we developed prototype soccer shoes with two different midsole designs. One was made up by homogeneous EVA material (Shore A 95) and the other (S2) was made up by the same material except for the forefoot area where a relatively soft EVA material (Shore A 85) was used. Both shoes have similar structure and material in all other aspects including the studs. The purpose of this study was to compare the plantar force generated during 30-m sprint wearing soccer shoes with homogeneous and dual density midsole designs

TEMPORAL ANALYSIS OF TYPICAL TAl CHI FORM -BRUSH KNEE TWIST STEP

The purpose of the study was to compare the difference of movement time of typical Tai Chi form -Brush Knee Twist Step in Tai Chi practitioners at different stages during their years of training. Fifteen subjects were recruited and assigned to three groups according to their years of Tai Chi training. The subjects' years of training in Groups 1,2, and 3 were 2.4 0.7, 5.4 0.6, and 18.2 9.7 years, respectively (N =5 in each group). Two Kistler force platform was employed to measure the instant of touch down and take off in the selected Tai Chi form. The results indicate that the movement time of the subjects with longer training duration (Group 3) was significantly longer than those with shorter training duration in Group 1 and Group 2. On further analysis, it was found that the double leg support time in Group 3 was longer than in Group 2 and Group 1

CHANGES OF KINEMATICS IN ROPE SKIPPING AFTER FATIGUE

Rope skipping is a popular indoor exercise which enhances cardiorespiratory fitness. A lot of researches investigated the physiological effects of rope skipping. However, biomechanical analysis in this exercise was limited. The purpose of this study was to compare the changes of kinematics of double-leg forward skipping, before and after fatigue. One male subject participated in the study. The subject skipped for 2 minutes and 55 seconds. Results showed that, after fatigue, the subject decreased the jump height, more trunk and head movement in the forward-backward direction, and might recruit more quadriceps and hamstrings muscles during skip

ELECTROMYOGRAPHIC ANALYSIS OF TAI CHI CHUAN: A PILOT STUDY

This investigation determined the electromyographical characteristic of the Tai Chi Chuan. An experienced Tai Chi Chuan Master was asked to perform the basic movements of Ward off, Roll Back, Press and Push. Both “gentle practising mode” and “strenuous defense mode” were performed. The Push movement was used for data analysis. The results revealed that the large muscle groups of the entire body were activated during Tai Chi Chuan. In most of the time, the work of muscles was quite low in both modes. However, it could generate a peak electromyographic activity as high as the fourth times of the maximal voluntary contraction in the ”strenuous defense mode”. It’s ability for defense combat shouldn’t be neglected. The results also demonstrated that Tai Chi Chuan involves the work of muscles of the trunk and the lower limbs greater than the upper limbs

THE EFFECT OF LOAD CARRIAGE ON GAIT PATTERN AND TRUNK POSTURE IN SCHOOL CHILDREN

The purpose of this study was to examine the way in which the weight of schoolbags combined with walking distance effects the gait pattern and trunk posture of school children over a long period of time in field situations. Twenty-three male primary school students were randomly assigned to carry loads of 0%, 10%, 15% and 20% of their body weight. Subjects were required to walk along a basketball court for 22 laps, i.e. 1892 meters were analyzed, using natural cadence for the duration of the session. The gait pattern and trunk posture at about 10, 700, 1300 and 1890 meters were analyzed. From the data that was obtained it was apparent that there were significant differences in trunk inclination angle, stance duration, double leg support duration, and swing duration between the loads of 0% and 20% body weight

THE EFFECTS OF ROPE SKIPPING ON MOVEMENT CO-ORDINATION IN CHILDREN - AN ELECTROMYOGRAPHY STUDY

INTRODUCTION: The issue of rope skipping as a method of fitness training is of great concern to the community. But little is known about the effects of rope skipping on the coordination ability of children. The purpose of this study was to examine the effects in terms of EMG responses of eight weeks of rope skipping exercises on the coordination ability of school children. METHODS: Twenty male Form 5 school students who did not have rope skipping experience were randomly recruited from a secondary school and formed paired exercise- and control groups, in accordance with the Body Mass Index. The age, body height and body weight of the exercise group were 15.60±0.52 years, 173.83±5.05 cm and 59.93±5.73 kg, and for the control group 15.70±0.68 years, 170.28±6.05 cm and 55.20±6.49 kg respectively. The subjects in the exercise group took part in rope skipping for eight weeks, 5 times weekly, twenty minutes each time, and at an intensity that produced a mean heart rate of an estimated 75% of maximal oxygen uptake. The subjects in the control group did not participate in any programmed exercise except the physical education courses for all students in the school. Two testing sessions were arranged for both groups: one week before and one week after the training program. In each session, the subjects were asked to perform rope skipping for 10 minutes at a rate which induced the heart rate of each subject to reach its maximal value. During testing, the remote EMG signals of eight muscles on the leg were detected and full-wave rectified. The duration of each muscle’s contraction and the timing sequence of the contraction among different muscles were calculated for the supporting phase. T-tests were used to examine the differences in the data to be compared. RESULTS: The trained group showed significantly shorter duration in vastus medialis contraction than the untrained group (