Exercise as it relates to Disease/The Benefits of High- and Low-Intensity Exercise in Stroke Patients

This is a review of a paper entitled 'Exercise-induced changes in cardiovascular function after stroke: a randomized controlled trial' by Tang et al.

A brief overview of strokes

Strokes account for around 6% of all deaths in Australia and cost the economy $5 billion every year. Those who survive are often left with cognitive and/or physical disabilities, and many are dependent on others for their daily needs. With such significant health and economic impacts, a strong focus on preventing strokes is vital.

The most common type of stroke is an ischemic stroke, which is caused by atherosclerosis (a build up of plaque) in the arteries feeding the brain. Source: Blausen Medical Communications, Inc.

Mitigating the risk of stroke through exercise

Aerobic exercise, in which the heart rate and breathing rate are elevated, has long been linked to a decrease in the risk factors associated with cardiovascular disease (CVD), such as diabetes, hypertension (high blood pressure) and dyslipidemia (cholesterol problems), which in turn decreases the likelihood of having a stroke. The Australian Health Department recommends a minimum 150–300 minutes of moderate intensity physical activity or 75–150 minutes of vigorous intensity physical activity per week to improve cardiovascular function.

Background to this research

Stroke survivors face a high risk of recurrent stroke because the majority have CVD, thus exercise should be included in rehabilitation programs. However, many survivors suffer from physical impairment and/or cognitive dysfunction which make it difficult for them to partake in moderate or vigorous intensity physical activity. They may still be able to undertake non-aerobic exercise, that is lower-intensity physical activity such as resistance training or mobility exercises. A 2014 Canadian study aimed to compare the effects of aerobic and non-aerobic exercise on cardiovascular function in stroke survivors.

Where is the research from?

The study was conducted in Vancouver, Canada by a group of reputable researchers who have published extensively on exercise and strokes in peer-reviewed journals. No conflicts of interest were declared and the study was approved by the University of British Columbia Clinical Research Ethics Board.

What kind of research was this?

The research was based on a single-blinded randomised controlled trial. Meaning participants were assigned randomly to groups and researchers who assessed the outcomes had no knowledge of what program participants were involved in, thus reducing bias.

What did the research involve?

The trial involved 50 participants, all of whom had suffered a stroke over 1 year ago but were able to walk at least 5 metres independently. Participants were divided into two equal-sized groups (see Table 1).

Table 1. The two exercise groups

	Aerobic exercise program	Balance and flexibility program
Exercise	Walking and cycling	Stretching, balancing and weight-bearing movement
Intensity	Increased from 40% to 70-80% over the course of the trial	Below 40%

Each group partook in 3x60-minute classes per week for 6 months and underwent a variety of laboratory tests at the beginning and end of the trial to determine changes in VO_2peak (a measure of aerobic capacity), functional mobility, cardiac function as well as blood glucose and cholesterol levels.

Classes were supervised and intensity was monitored using heart rate devices, two measures which would have ensured greater accuracy. However, the findings could have been strengthened by including a control group.

What were the basic results?

Key findings are shown below:

• Neither group demonstrated an increase in VO_2peak.
• Only the group which undertook aerobic exercise showed improved cardiac function.
• Both groups showed improvements in blood glucose and cholesterol levels, and an increase in functional mobility.

The first finding was surprising because undertaking an aerobic exercise program typically improves cardiorespiratory fitness. Researchers suggested performance in VO_2peak tests in this study may have been affected by physical and/or cognitive disabilities suffered by stroke survivors.

What conclusions can we take from this research?

All stroke survivors should be encouraged to partake in some sort of physical activity. Aerobic exercise, such as walking or cycling at a moderate intensity, provides the most wide-ranging benefits. Those who are unable to partake in high intensity activities can consider alternatives including mobility exercises and resistance training in order to reduce the risk of CVD.

Practical advice

Physical activity can improve health and increase independence in stroke survivors, but the type and intensity of exercise must be appropriate for each individual's physical and mental condition, and is best assessed by a qualified health professional. A range of examples are provided in Table 2.

Table 2: Aerobic and non-aerobic exercise options for stroke survivors

Aerobic	Non-Aerobic
Walking (on flat ground or uphill)	Stretching (yoga, pilates, tai chi)
Cycling (outdoor or on a stationary bicycle)	Weight-bearing exercises (circuit training, free weights or weight machines)
Step-based activities (up stairs or on a stepper machine)	Coordination and balance activities (for example shifting weight between feet and hands)

Further information/resources

• Stroke Foundation
• Better Health
• American Heart Foundation
• Informme