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Scientists have discovered that a hormone called irisin – produced during exercise – may protect against Alzheimer’s disease. Previous studies have shown that regular exercise can reduce the risk of developing Alzheimer’s by up to 45%, but exactly how and why hasn’t been understood until now.
Researchers from Massachusetts General Hospital (MGH) found that the production of irisin leads to a reduction in the plaques and tangles in the brain that cause Alzheimer’s. Irisin encourages the immune cells in the brain to produce more neprilysin - an enzyme which breaks down plaques in the brain, which are made from amyloid beta deposits.
When the researchers applied irisin to brain cells, the amount of amyloid fell considerably.
All exercise will use the muscles, which will in turn produce irisin. However, certain types of exercise will increase this hormone production even more. These are strength training, endurance training and high-intensity interval training (HIIT).
If you’re new to exercise or returning after a long time, or if you have any pre-existing medical conditions or injuries, speak to your GP before embarking on a new exercise regime.
Strength training is vital as we age. The benefits of strength training include protecting against muscle loss (sarcopenia) and preventing osteoporosis.
James Staring, founder and coach at Fit to Last, explains why having more muscle can lead to weight loss and better overall health: “When you build lean muscle, your body needs to burn more calories to maintain that muscle tissue, instead of storing excess calories as fat".
"Strength training leads to more sustainable weight loss as well as keeping your body weight at a consistent level. Additionally, when you undertake strength training, you’ll be stronger and more capable of completing daily tasks with relative ease. You’ll also have the physical endurance to do more, every day.”
Strength training doesn’t need to mean hours lifting weights in the gym, either - two sessions per week are recommended by the NHS.
You can do exercises at home using resistance bands, kettlebells, dumbbells, or even your own bodyweight.
The title might sound daunting, but endurance training doesn’t need to be hard. Staring says: “Endurance training is a longer bout of exercise (10 minutes and higher) at a constant pace of up to 65% of your maximum heart rate.”
It’s worth knowing more about heart rate zones in exercise if you want to undertake endurance training to increase irisin. Some people like to wear a heart rate monitor when exercising, in the form of a smart watch, fitness tracker or chest strap (the Garmin HRM-Pro Plus is a favourite).
This can enable you to understand how your heart responds to exercise and to work out what 65% of your maximum heart rate (MHR) would be. Alternatively, you can go by the rate of perceived exertion (RPE). This scale ranges from one to 10, with 10 being all-out max effort, and one being no movement at all.
For around 65% of your MHR, you want to be working at an RPE of six or seven – you should still be able to talk in sentences but slightly out of breath.
Staring says: “You’ll get the most benefit out of endurance training by choosing exercises that use large muscle groups like rowing, running and swimming."
Staring says: “HIIT involves short intervals of up to 60 seconds of high intensity exercise at up to 95% of maximum heart rate, followed by equally short rest periods of maximum 60 seconds.”
HIIT workouts have become popular thanks to celebrity trainers such as Joe Wicks, who use the principles of HIIT to encourage short bursts of activity with rest periods.
While true HIIT can be hard going, because you’re pushing your heart rate so high, working intensely (at a rate of exertion that suits you), followed by a brief rest, can be beneficial.
As well as increasing irisin, HIIT is good for the brain. Studies have shown that interval training increases blood flow to the brain, something that often declines with age.
HIIT is a form of cardio exercise, which also helps strengthen the heart and lungs, keeping us in good physical shape. HIIT can be as simple as introducing an element of briskness to whatever activity you’re doing:
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