High-intensity interval training (HIIT) is safe for people who have had a heart attack or other cardiac event and may improve their fitness faster than conventional rehabilitation exercise programmes, according to a clinical trial.
In many countries – including the UK, US and Australia – individuals who have had a cardiac event can be referred to cardiac rehabilitation programmes, which are designed to improve heart health via exercise training and lifestyle education.
To avoid putting too much strain on the heart, these usually involve moderate-intensity, steady-state exercises, such as walking on a treadmill at a continuous, comfortable pace.
Now, Gordon McGregor at University Hospitals Coventry and Warwickshire NHS Trust in the UK and his colleagues have found that HIIT – vigorous bursts of exercise interspersed with short rest periods – is safe for people doing cardiac rehabilitation and more effectively improves their cardiorespiratory fitness, a marker of heart health, than moderate-intensity exercises.
The team looked at 382 adults, with an average age of 59, who had been referred to six UK cardiac rehabilitation centres.
They had previously been diagnosed with coronary heart disease or had a heart attack, bypass surgery – to divert blood around narrowed or clogged parts of major arteries – or a stent procedure, involving the insertion of a balloon-like device to keep arteries open. The participants needed to be clinically stable for at least two weeks to take part in the research.
They were then randomly chosen to do either standard moderate-intensity exercises or HIIT twice a week for eight weeks.
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The moderate-intensity sessions involved 20 to 40 minutes of continuous exercise on a stationary bike or other exercise machine at 60 to 80 per cent of their maximum aerobic capacity. HIIT involved 1-minute bursts of exercise on a stationary bike repeated 10 times at more than 85 per cent of their maximum capacity, with 1-minute recovery periods in between.
The HIIT group showed greater improvements in cardiorespiratory fitness, determined by measuring their peak oxygen uptake during exercise. This fitness advantage would be expected to reduce the risk of premature death by around 15 per cent, says McGregor.
One participant developed chest pain during a HIIT session and was diagnosed with atrial fibrillation, an irregular heart rhythm, but it was non-life-threatening and probably unrelated to the training, says McGregor.
David Hare at Austin Hospital in Melbourne, Australia, says that atrial fibrillation is common and could have happened in either group of participants.
The Association of Chartered Physiotherapists in Cardiovascular Rehabilitation, which writes the UK’s cardiac rehab guidelines, is reviewing this trial, among others, and will release updated guidelines this year.
“I think there’s enough evidence now that HIIT should be seen as another tool in the bag,” says McGregor.
Journal reference:
European Journal of Preventive Cardiology DOI: doi.org/10.1093/eurjpc/zwad039