How a short burst of intense exercise can make your immune system stronger

For years the official exercise advice has been that 150 minutes of moderate exercise a week, such as brisk walking, brings the same broad health benefits as 75 minutes of more vigorous activity, such as running or cycling.But that advice is now being challenged by new research that appears to show doing shorter bursts of intense exercise – which leaves us much more out of breath – can help us live longer than exercising moderately will.In fact, you might need to do only a few minutes of higher-intensity exercise to achieve the same benefits.A study published in the International Journal of Behavioral Nutrition and Physical Activity earlier this month analysed data from more than 147,000 adults aged 40 to 74 who wore activity monitors.The researchers compared this against the participants’ health records over the next eight years. As expected, 150 minutes of moderate exercise a week was linked to lower risk of dying during the study.But remarkably the researchers also found just 12 minutes a week of vigorous exercise was linked to the same (30 per cent) reduction in early death.Other new research suggests why intense exercise could have this effect – by making our immune systems much better at finding and destroying infected and abnormal cells (before they turn cancerous).For example, when 24 men did two weight-training sessions – lifting half the maximum they could for sets of 12 repetitions, or lifting around 85 per cent of their maximum in short bursts until close to exhaustion – blood tests showed the high-intensity workout produced a bigger rise in key immune cells. New research appears to show doing shorter bursts of intense exercise – which leaves us much more out of breath – can help us live longer than exercising moderately willBut crucially the researchers found high-intensity exercise created high levels of chemokine receptors – proteins on immune cells that pick up chemical signals released by tissues.These signals help the immune cells travel from the bloodstream and into the tissues to hunt for and kill infected or abnormal cells, reported the European Journal of Applied Physiology.‘Studies in humans have shown these immune cells have special “powers” that allow them to leave the blood and travel to other body sites,’ says James Turner, an associate professor in exercise physiology and immunology at the University of Birmingham.Studies have ‘found them accumulating in places including the lungs and gut – key entry points for infections’, he says. ‘They go there to look for infections.’It’s long been thought intense exercise can temporarily weaken the immune system, as blood tests showed levels of some immune cells plunged in the hours afterwards.But Dr Turner says that conclusion was based on a misunderstanding. ‘Immunity has not been weakened – in fact, the opposite is the case,’ he says.Instead, many of those immune cells disappear from the bloodstream for a short period to search for infected, damaged or abnormal cells. So while blood tests suggest immune cell levels have dropped, they’ve actually just relocated to where they could be more effective.A second study, published in Nature Communications in January, suggests short bursts of intense exercise may also make immune cells more capable of attacking and destroying infected or abnormal cells.When researchers at TU Dortmund University in Germany put 23 healthy, active adults through two different 50-minute treadmill workouts – a steady run, or six three-minute bursts of hard running, each followed by three minutes at an easier pace – they discovered a significant change in some of the 6,000 proteins inside the participants’ immune cells.These proteins help control what the cells actually do. After the intense exercise, the levels of 1,377 proteins changed significantly, compared with changes in just 64 proteins after the steadier workout.One protein that increased after intense exercise, called SYTL2, helps immune cells release chemicals that punch holes in infected or abnormal cells, triggering their destruction.Another, BST2, helps prevent new virus particles that have been made inside an infected cell from escaping and spreading.And TLR1, a protein that helps immune cells recognise microbes and launch an attack, rose after the intense exercise but fell after the moderate workout.David Walzik, the study’s lead author, said: ‘What surprised us was that the same amount of exercise produced a much greater response when it was done at high intensity [ie in less time].’Glen Davison, a professor in sport and exercise sciences at University of Kent, says this does not mean ever longer and harder workouts are necessarily better for the immune system.‘One hard workout could help prime and activate it,’ he says, but ‘repeated hard workouts over successive days before the body has recovered can be counterproductive as, combined with other factors such as poor sleep, this could affect your ability to fight off infection’.And if you are already feeling ill, ‘don’t try to train through it’. Hard exercise can put extra stress on the body and may prolong the illness, he says.