Why running slowly may be better for your heart and protect against colds

Slow and steady wins the race, the old saying goes – and now it also seems to apply to the health benefits of exercise.

In fact, the evidence increasingly suggests that regular, slow runs could strengthen your heart, reduce your risk of type 2 diabetes and support your immune system and overall fitness far better than running at full tilt.

The same goes for other cardiovascular exercise taken at a slower pace, such as swimming, rowing and cycling.

Indeed, running clubs are now being set up just for plodders and joggers.

“Slow running is increasingly popular among recreational exercisers,” says Dan Gordon, an associate professor in cardiorespiratory exercise physiology at Anglia Ruskin University.

“We went through a craze for high-intensity interval training (HIIT) over the past decade or so, and while I’m not disputing the potential benefits of HIIT, one downside is that it’s challenging, and so it’s difficult to get into if you’re not particularly fit.”

This means a high dropout rate, he says – whereas with slower, less strenuous exercise, people are less likely to give up.

There are also “proven physiological benefits of running at this effort level”, he says.

These were shown in a Danish study published in 2015, in which 5,000 people were monitored for 12 years.

They were put into four groups: non-joggers (sedentary), and light, moderate or strenuous joggers.

The slow and moderate-paced joggers had the lowest rate of death from any cause, while strenuous runners had a similar death rate to the sedentary group.

One theory is that this might be due to the way that slow running reduces resting blood pressure and strengthens the heart.

Professor Gordon explains: “Fundamentally, it improves the efficiency by growing the heart muscle. If you have a bigger heart muscle, it can squeeze harder. It also increases the size of the chambers within the heart so it can hold more blood per pump.”

Slow running improves endurance too, as you can run at a slower pace for longer – this increases the production of red blood cells, which in turn means the blood can carry more oxygen.

These adaptations to the heart muscle are not increased by training at any higher intensity.

Another benefit of slow cardio – also known as ‘zone 2’ cardio, when working at 60-70 per cent of our maximum heart rate – is that it causes the body to use stored fat as fuel, says Dr Lindsy Kass, an exercise physiologist at the University of Hertfordshire, rather than carbohydrate, as happens with higher intensity exercise.

Metabolising fat is more efficient and better for health overall, adds Professor Gordon: “It’s associated with better blood glucose levels and reduces the risk of type 2 diabetes.

“Studies have shown that gains in VO2 max [oxygen capacity] and speed on race day are about 1 per cent better for athletes who include more slow running in their training programmes.”

That is a significant competitive advantage, and once you know this it is not surprising to find that most elite athletes spend as much as 80 per cent of their training in zone 2.

“I used to work with British Rowing, and although their races are about six minutes long, they spend an hour-and-a-half slow rowing three times a week,” says Dr Kass.

“The first year they trained like that was the year they started winning all the medals.”

Another reason elite athletes spend time training at lower intensities is to reduce the stress on their bodies, helping them avoid infection or injury.

Professor Gordon says: “If we’re sedentary, we’re quite susceptible to illness. But if we do moderate-intensity exercise we develop a better immune response and reduce our susceptibility to illness.

“But when we start doing more high-intensity exercise, we require a lot more time to recover [as much as 48 to 72 hours afterwards], and during that recovery period you are immune-suppressed.”

“So the more high-intensity exercise you do, especially if you don’t take an adequate amount of recovery time between sessions, the more likely you are to get illness and infection – and to injure yourself.”

So what do we mean by slow running?

Experts say it’s not about speed but how intense the effort feels.

“Try singing to yourself while jogging, and if you can do it without gasping you’ve got it about right,’ advises Professor Gordon.

The same philosophy applies to resistance work using weights.

Slowing down removes the momentum in a movement, which encourages good form and reduces injury risk.

Some studies show that taking twice as long on the lengthening ‘eccentric’ phase of a lift (for instance, coming down from a pull-up) than on the shortening ‘concentric’ phase (the pull-up bit) can improve muscle growth.

But don’t go too slow – you will fatigue quicker and not be able to lift as heavy weights as you should for full muscle-strengthening benefits, says Dr Richard Blagrove, a senior lecturer in physiology at Loughborough University.

He adds: “The majority of people would be better off doing a “controlled” [not super slow] eccentric phase and an explosive [as fast as possible] concentric phase with moderate to heavy loads for most of their resistance training, with some exercises geared towards developing power.”