Please use this identifier to cite or link to this item: http://hdl.handle.net/10397/6222
Title: The effects of Tai Chi training on the cardiovascular health and postural control of older adults : a mind-body perspective
Authors: Lu, Xi
Keywords: Tai Chi.
Equilibrium (Physiology)
Cardiovascular system -- Diseases -- Prevention.
Hong Kong Polytechnic University -- Dissertations
Issue Date: 2013
Publisher: The Hong Kong Polytechnic University
Abstract: Aging is a worldwide phenomenon which causes health, social and economic problems. Healthy aging has been the focus of many scholarly investigations, particularly with regard to cardiovascular disease and postural control problems causing falls. Arterial compliance is an index reflecting artery function, and it is closely related to cardiovascular health. Decreased arterial compliance is associated with aging and many kinds of cardiovascular disease. This makes strategies directed at improving arterial compliance important for improving the health of older adults. Aerobic exercise is beneficial for arterial compliance. Improving and maintaining muscle strength through resistance exercises is also known to be beneficial for older adults, but it has been found to decrease arterial compliance. Therefore, exercise protocols which combine muscle strength training with improved arterial compliance are needed. Falls often occur when older adults attempt dual-tasking such as postural control with concurrent cognitive tasks. Modern falls prevention programmes focus on improving postural control while dual-tasking. Stepping down is a common functional task which is quite demanding in terms of postural control, and negotiating stairs concurrently with a cognitive task is a common setting for falls among older adults. Therefore, exercises which could enhance older adults' handling of dual motor-cognitive task performance would be useful. Tai Chi requires good mind and body coordination. It trains both cognitive and physical functioning. Previous studies have explored the effects of Tai Chi training on postural control or on cognitive performance, but never the two perspectives combined together. In other words, research on the interaction of Tai Chi's mind and body elements is lacking. Since there is an urgent need to develop an exercise programme which would promote BOTH physical and mental/cognitive health, this study was launched to investigate the mind and body effects of Tai Chi on cardiovascular function, muscle strength, and dual postural-cognitive task performance. Three different experimental series/designs were adopted to examine five inter-related study objectives. In experimental series 1, a cross-sectional study was conducted to compare older Tai Chi practitioners with healthy older adults. The objectives were to investigate the extent to which older Tai Chi practitioners had 1) better arterial compliance and muscle strength, and 2) better cognitive performance and/or postural control when dual-tasking than healthy controls similar in age, gender, height and weight. In experimental series 2, a randomized control trial (RCT) was conducted to examine whether 16 weeks of short-form Tai Chi training improved 3) the arterial compliance and lower limb muscle strength and 4) the cognitive performance and postural control during dual-task performance in older adults when compared with control subjects who attended music, English and handicrafts classes. This was followed by a pilot single-case study 5) which compared Tai Chi with arm ergometer cycling (exercise with no cognitive component) with respect to modulating the autonomic nervous control and prefrontal activity during exercise. The investigation involved five studies. Study 1 was a cross-sectional study which compared a group of experienced older Tai Chi practitioners (n=29, mean age of 73.7 years) and a group of older healthy control adults (n=36, mean age of 71.4 years). The arterial compliance (both larger arterial compliance [C1] and small artery compliance [C2]) and concentric and eccentric knee extensors and flexors muscle strength were measured. The second study was a RCT in which 31 older women (aged more than 60 years) were randomly assigned to receive either Tai Chi training or an interest, three sessions per week for 16 weeks. The arterial compliance (both C1 and C2) and knee muscle strength were measured before and after training. Study 3 was a cross-sectional study comparing the dual-tasking performance between older experienced Tai Chi practitioners (n=28, means age of 73.6 years) and healthy older controls (n=30, means age of 72.4 years). The dual-tasking involved a stepping down balance task and an auditory Stroop test. The sway parameters of center of pressure (COP) including total sway path and sway area while the auditory task included reaction time and error ratio. Study 4 was a RCT which investigated the effects of 16 weeks short-form of Tai Chi training on the dual-tasking paradigm. The fifth one was a pilot study investigating the heart rate variability and cranial oxyhaemoglobin level while a Tai Chi master performing Tai Chi and arm ergometer cycling with similar exercise intensity.
Findings from Study 1 showed that experienced older Tai Chi practitioners had significantly better arterial compliance in both C1 and C2 index when compared with controls (14.7±4.4 versus 10.5±2.8, p<0.001; 3.5±1.5 versus 2.7±1.2, p=0.002, respectively). They also had better muscle strength than those of controls as indexed by the peak torque-to-body weight ratio; being stronger in concentric knee extensors (1.17±0.42 versus 0.96±0.33, p=0.026), eccentric knee extensors (1.68±0.62 versus 1.31±0.49, p=0.01) and flexors muscle strength (0.89±0.35 versus 0.71±0.31, p=0.03). The results of Study 2 confirmed the training effects of Tai Chi. Older Tai Chi participants showed significant improvements in their arterial compliance (pre-training: 10.3±2.7, 2.8 ±1.3 for C1 and C2, respectively while after-training, the value increased to 13.0±3.8, 3.3±1.1; both p<0.05) and lower limb muscle strength (with eccentric knee extensors increased to 21.3%, p<0.05) after training while controls did not. For the dual-tasking performance, the cross-sectional Study 3 showed that experienced Tai Chi practitioners achieved better performance in a dual motor-cognitive-task test involving stepping down and an auditory Stroop test than healthy older controls. Tai Chi practitioners had faster response time (1.58s±0.46s versus 1.87s±0.48s, p=0.023), made fewer mistake (13%±12% versus 26±15%, p=0.001) for the auditory Stroop tasks, less COP sway as indicated by the total sway path (258.3mm±41.8mm versus 293.1mm±74.9mm, p=0.033) and sway area (9.0±2.5cm versus 11.3±4.9cm, p=0.034). Study 4 was a RCT conducted in the healthy older adults with one group underwent 16 weeks of Tai Chi training while another group served as a control group. After training, older women in the Tai Chi group made fewer errors (25.8%±15.5% to 16.3%±14.5% pre and post, respectively, p<0.05) and incurred less attentional cost (post-training: 0.5±0.4 versus pre-training: 0.6±0.5, p<0.05). The Tai Chi subjects also improved their postural control in both single-and dual-tasking conditions after training (both COP total sway path and sway area, p<0.05) while the controls did not. The Study 5 was a pilot study which showed that at similar exercise intensity, an older subject showed more prefrontal oxygenation and higher parasympathetic control during Tai Chi practice than during arm ergometer cycling. The better arterial compliance and greater muscle strength achieved through Tai Chi practice may be related to its mind-body characteristics. The mental concentration during Tai Chi's physical movements may shift the autonomic nervous system to parasympathetic control. This may prevent arterial stiffness and counterbalance the strength training effects on the arteries. This idea was suggested by the findings of Study 5 which showed that Tai Chi practice involves parasympathetic dominance compared with arm ergometer cycling. The better postural control after stepping down while dual-tasking may also be explained by the training effects of both the mind and body components of Tai Chi practice. The Tai Chi drills may have improved both attention and postural stability, which might be reflected in dual-tasking performance. The increased prefrontal activity observed during Tai Chi practice might be related to improve mental capacity. These findings show that Tai Chi could be a suitable exercise for improving the arterial compliance and muscle strength of the older adults. Moreover, it could enhance older adults' dual-tasking performance and may help to prevent falls.
Description: xxiii, 221 leaves : ill. ; 30 cm.
PolyU Library Call No.: [THS] LG51 .H577P RS 2013 Lu
URI: http://hdl.handle.net/10397/6222
Rights: All rights reserved.
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