Need an extra dose of motivation for those lockdown
workouts? Lisa Salmon finds out how exercise can benefit the immune
system.
Never before have the nation’s exercise routines been so visible, with
streets, parks and public spaces regularly dotted with walkers, joggers
and cyclists huffing and puffing their way through their permitted daily
exercise.
But while it’s well established that being physically active is good for
physical and mental health, how it affects the immune system has
sometimes been the topic of debate. Some studies have suggested immunity
is temporarily compromised after strenuous exercise, while other
research says exercise is beneficial for immunity – so what does this
mean for all those lockdown workouts?
Good news: a new University of Bath review has concluded that regular
exercise does help maintain a healthy immune system.
Immunity expert and study co-author Dr James Turner explains: “In the
context of coronavirus, the most important consideration is reducing
your exposure from other people who may be carrying the virus. But
people shouldn’t overlook the importance of staying fit, active and
healthy during this period. Provided it’s carried out away from others,
then regular, daily exercise will help better maintain the way the
immune system works.”
He says regular moderate-intensity aerobic exercise – such as walking,
running or cycling – is recommended, with the aim of achieving 150
minutes per week. “Longer, more vigorous exercise wouldn’t be harmful,
but if capacity to exercise is restricted due to a health condition or
disability, the message is to move more and that something is better
than nothing,” says Turner.
“Given the important role exercise has for reducing the risk of
cardiovascular disease, cancer and type 2 diabetes, the findings from
our analysis emphasise that people shouldn’t be put off exercise for
fear that it will dampen their immune system. Clearly, the benefits of
exercise, including endurance sports, outweigh any negative effects
which people may perceive.”
Study co-author Dr John Campbell adds: “It’s increasingly clear that
changes happening to your immune system after a strenuous bout of
exercise don’t leave your body immune-suppressed. In fact, evidence now
suggests your immune system is boosted after exercise.”
Here, Turner and Campbell outline some of the ways exercise is
beneficial to the immune system…
- Vigorous exercise can help improve the immune system rather than
suppress it
Research from the Eighties and Nineties led to the ‘open-window’
hypothesis, which suggests the immune system is compromised in the hours
after vigorous exercise, leading to an increased risk of infections in
subsequent days. Turner and Campbell say that although the behaviour of
almost all immune cells is altered during and after exercise, this
reflects a temporary redistribution of immune cells to outlying tissues.
This, they say, results in increased immune surveillance and immune
regulation, rather than immune suppression.
“It’s a misconception to label any form of acute exercise as
immunosuppressive, and instead, exercise most likely improves immune
competency across the lifespan,” explains Turner. “Exercise alone
doesn’t cause immune suppression, rather, in athletes for example, it’s
other things that suppress immunity, like inadequate sleep, diet and
psychological stress or anxiety.”
- Exercise may limit ageing of the immune system
Turner and Campbell say studies show regular physical activity and
frequent exercise might limit or delay ageing of the immune system.
Exercise has been shown to be the most successful way to delay the onset
of frailty in old age, and varied exercise including resistance,
balance, endurance and coordination training is the most effective,
according to a 2016 University of Valencia
review.
- Wounds heal faster if you’re fit
The immune system has three main lines of defence, say Turner and
Campbell, and exercise helps maintain the normal function of each of
these. The first defence is physical barriers like the skin, which stops
germs from entering the body. Studies have shown that skin wound healing
is faster in people who are regularly active compared to sedentary
people, thus reducing the risk of infections in people who exercise.
US research published in 2005, for example, found that when healthy
sedentary people aged between 55-77 took part in a three-month aerobic
exercise programme, exercising for an hour three days a week, as well as
achieving significant improvements in cardiorespiratory fitness, a small
wound made on their arms healed at a much faster rate than in a control
group that didn’t exercise.
- Exercise boosts natural ‘killer cells’
The immune system’s second line of defence is ‘innate’ (or natural)
immunity, which is mainly made up of cells called neutrophils, and
natural killer cells. “Exercise has a profound effect on these cells,”
explains Campbell. “For example, during a bout of exercise, natural
killer cells move into the bloodstream in vast numbers, and following
exercise these cells migrate to sites of inflammation to seek out
pathogens, damaged cells (e.g. muscle) and cancerous cells.”
- Regular exercise helps the immune system identify germs better
The third line of defence is ‘adaptive’ (or memory) immunity, which is
made of lymphocytes called T cells and B cells. Exercise also has a
profound impact on these cells. “It has been shown that lifelong regular
exercise may help maintain healthy numbers of young T cells as we age,
which may help the immune system better identify pathogens and cancer as
we reach older age,” says Turner.
- Exercise improves vaccination response
Vaccination is one of the best ways to see how the immune system works
because it tests the ability of many different immune cells to
coordinate and produce antibodies, explains Campbell. Exercise of almost
any type has been found to improve the way people respond to vaccines,
according to a 2014 University of Sydney review. “There’s even evidence
that elite athletes who train regularly have higher antibody responses
to vaccination than people who don’t exercise,” he adds.
- It’s good for health overall
Regular physical activity reduces the incidence of many chronic diseases
in older age, say Turner and Campbell, including communicable diseases
such as viral and bacterial infections, as well as non-communicable
diseases like cancer and chronic inflammatory disorders.
Remember to stay safe and sensible
While the beneficial effects of exercise on the immune system, as well
as general health, may encourage people to exercise during lockdown,
Turner and Campbell stress that Government advice should be followed at
all times if you’re experiencing symptoms of possible coronavirus
infection (this means stay home!).
Turner adds: “More generally, people can exercise moderately with mild
upper respiratory tract symptoms such as those of a common cold: e.g.
runny nose, congestion, and a mild sore throat. But given the difficulty
of determining whether some of these symptoms could be linked to
coronavirus, it would be sensible to exercise at home, away from other
people.
“You shouldn’t exercise if you’re experiencing a severe sore throat,
body aches, shortness of breath, general fatigue, a chest cough, or
fever.”