Winter is just around the corner. The temperature outside has fallen. The nights are drawing in. The leaves have fallen from the trees. The squirrels and other small animals are gathering up the last of the fallen nuts before they hibernate.

Like the squirrel, you might be tempted to hide away until spring, to curl up in front of the fire all snug and warm. But being dormant for too long can be bad for your health⁽¹⁾. If you want to keep fit and healthy, be sure to break up long sedentary periods with light activity.

But is that enough?

Your immune system plays a critical role in fighting the flu; it sends out white blood cells to track down and destroy viruses⁽²⁾.
During the flu season, when your immune system is working overtime, you would be wise to do 150 minutes of moderate aerobic activity each week if you are fit and healthy⁽³⁾, i.e. anything that makes you breathe more heavily and feel warm⁽⁴⁾. This might include brisk walks, cycling, dancing or an over-50s aerobics class.

Alternatively, if you’re very fit, 75 minutes of a vigorous aerobic activity⁽⁵⁾ such as running, jogging or cycling over a hilly terrain would be equivalent. Exercising outside is also good for boosting your mood during the winter months⁽⁶⁾. Talk to your doctor first to check what level of exercise is suited and recommended to your health.

How does exercise help us fight the flu?

Research has shown that exercise boosts your immune system. One study found that regular walking may increase white blood cells numbers⁽⁷⁾. Another found that 65-year-olds who exercised regularly have as many T-cells – a specific type of white blood cell – as someone in their 30s⁽⁸⁾.

There are also some unproven theories as to why exercise helps us fight – and even prevent – the flu. The first is that physical activity may help to flush bacteria out of our lungs and airways, lowering the chances of us catching the virus⁽⁹⁾.

Other theories suggest that the increase in body temperature during and after exercise may stop bacteria from growing⁽¹⁰⁾ or that exercise may help white blood cells detect viruses earlier by helping them circulate faster⁽¹¹⁾ – both of which would help us to fight off the infection.

One thing is, however, clear: remaining active during the winter months is key to keeping the flu at bay – particularly for the over 65s.

Sources
(1), (3), (5) http://www.nhs.uk/Livewell/fitness/Pages/physical-activity-guidelines-for-older-adults.aspx
(2) http://www.webmd.com/cold-and-flu/flu-guide/use-your-immune-system-to-prevent-flu#1
(4), (6) http://www.webmd.boots.com/healthy-ageing/features/active-ageing
(7) http://www.ageuk.org.uk/health-wellbeing/conditions-illnesses/how-to-avoid-catching-colds-or-flu/
(8) http://www.webmd.com/cold-and-flu/cold-guide/exercise-when-you-have-cold#1
(9), (10), (11) https://medlineplus.gov/ency/article/007165.htm