Thursday April 5 2012
Research looked at heart health of older people who did tai chi
“Practising the ancient art of Tai Chi can boost elderly people’s hearts,” according to the Daily Mail. The slow-moving exercise is hugely popular in the far east, and is increasingly practised by people around the world in a bid to improve balance, strength and flexibility.
The news story is based on a study that found that older people who practised tai chi regularly had more elasticity in their arteries, as well as greater muscle strength in their knees, compared with those who didn’t practise the ancient art. Greater elasticity is associated with better circulatory health, and as we get older our arteries naturally lose elasticity. However, few conclusions can be drawn directly from this small study about whether tai chi has any benefits for the heart, as elasticity does not directly equate to having better heart health.
This study did not follow people over time so only provides a snapshot of people’s lifestyles and health at a single point in time. This means it cannot say how one factor affected another. Also, it did not compare tai chi directly to other forms of exercise such as swimming or yoga, so it cannot say which is more beneficial.
Overall, this study cannot tell us much about the benefits of tai chi, although there is an expanding body of research that demonstrates the heart and health benefits of this type of exercise for people with arthritis, or those at risk of falling.
Where did the story come from?
The study was carried out by researchers from The Hong Kong Polytechnic University and the University of Illinois, USA, which funded the study. It was published in the peer-reviewed European Journal of Preventive Cardiology.
Its findings were exaggerated in The Daily Telegraph and the Daily Mail, both of which incorrectly reported that tai chi practitioners were less likely to suffer high blood pressure. Although the study did measure people’s blood pressure it looked primarily at muscle strength and arterial compliance, which is a measure of the elasticity of the arteries.
What kind of research was this?
This was a cross-sectional study that investigated whether tai chi practitioners have better arterial compliance and muscle strength than non-practitioners. Arterial compliance is a measure of how well the arteries expand and contract in response to the blood being pumped through them. The researchers say that arterial stiffness is closely associated with cardiovascular diseases such as high blood pressure, heart disease and stroke, so arterial compliance can be one way of predicting the risk of these conditions in the elderly. Elasticity of the arteries tends to diminish naturally with age.
However, while arterial stiffness is an interesting phenomenon, it is only an interim or surrogate marker of cardiovascular disease. Aerobic exercise has been found to reduce arterial stiffness in older people, but research to date has found that muscle strength training combined with aerobic exercise does not. What is needed, say the researchers, is a form of exercise that improves both arterial elasticity and muscle strength. Muscle strength is important to older people as evidence suggests it improves stability and therefore helps to prevent falls.
Tai chi, which is a Chinese system of mind–body exercise, is usually regarded as aerobic and improves muscle strength. This research set out to test whether or not it improves arterial compliance.
What did the research involve?
The researchers recruited 65 elderly people with an average age of nearly 78 years, living in Hong Kong. They were all independent in their daily living activities. Some 29 of the participants (nine men and 20 women) were recruited from local tai chi clubs and had practised tai chi for a minimum of 1.5 hours a week for at least three years. A further six men and 30 women were recruited from elderly centres and had no previous tai chi experience, but were involved in activities such as morning walks, leisure hiking or household work. Researchers had previously excluded anyone with specific conditions and disorders, including dementia, lung disease and various heart conditions, although those with high blood pressure and diabetes were accepted.
Participants’ height and weight was recorded to calculate their body mass index (BMI) scores and each was asked to complete a validated questionnaire on their leisure time physical activity. They were then categorised into three different levels of usual physical activity – light, moderate and heavy.
Researchers used specialist technology, called a “cardiovascular profiling system” to measure arterial compliance in participants. This involved measuring the pulse of the heart as well as taking blood pressure and ultrasound measurements.
They also measured muscle strength within the knee. To do this participants were asked to extend and bend the knee of whichever was the “dominant leg” as far as possible, five times. The movements were recorded by a specialist machine for analysis. They looked at two types of muscle strength – called concentric and eccentric strengths. Concentric contraction occurs when a muscle shortens in length and develops tension. Eccentric contraction involves the development of tension while the muscle is being lengthened.
The researchers analysed their results using validated methods and adjusted the results for age, BMI, gender and activity levels.
What were the basic results?
The researchers say that the tai chi practitioners showed “better artery compliance” than the control group. The tai chi group also had statistically greater eccentric muscle strength (but not concentric muscle strength) in the muscles around the knee. That means they had greater strength when extending their legs but not when bending their knee.
They also say there was no difference in physical activity levels between the two groups. A higher proportion of subjects in the control group had high blood pressure than in the tai chi group (61% versus 38%). On average, people in the control group also had significantly higher BMIs than the tai chi practitioners.
How did the researchers interpret the results?
The researchers conclude that their findings suggest that tai chi could be a suitable exercise for older people who wish to improve both cardiovascular function and muscle strength. They also suggest that the lower blood pressure scores found in the tai chi group could have been an effect of tai chi and had an effect on arterial compliance.
Overall, few conclusions about the possible benefits of tai chi can be drawn from this small study. Apart from the limitations caused by its small size, as a cross-sectional study it did not follow people up over time and, therefore, cannot show that lifestyle factors, such as type of exercise lead to particular health outcomes. The researchers mention some limitations, for example:
- It is possible that those who practised tai chi prior to the research had healthier lifestyles generally than those who did not – for example they might have had better diets, or smoked less.
- As it did not look at cardiovascular health overall, but only looked at one intermediate factor – arterial compliance – at a single point in time, it is not possible to say how much cardiovascular health might be improved. Arterial compliance is a measure of how elastic the arteries are.
- It did not compare tai chi directly to other types of exercise – such as swimming or walking – so it cannot tell us whether one is more beneficial than another.
Although this research does not reveal much new information about tai chi, the ancient art is an attractive form of low-impact exercise that may well have benefits for older people, and there is a body of evidence demonstrating its value.