During the January lockdown, Marilyn Law thought she was doing the right thing in using her new exercise bike to keep fit while gyms were shut.
Marilyn, a keen walker who previously had attended a weekly exercise class, furiously pedalled away for 40 minutes four or five days a week — often building up quite a sweat.
But within two weeks of starting her new regimen, Marilyn developed blinding headaches. The excruciating pain centred on one eye and would come on without warning, often in the middle of the night.
‘The throbbing started in the early hours of the morning,’ says Marilyn, 75, a retired caterer and mother of two, who lives in Bury, Greater Manchester, with her husband Robert, also 75, a retired driving instructor.
‘It was bizarre because the room was quiet and I was asleep — and yet it would wake me up,’ she says. ‘I started to worry I was having a stroke or that it was a tumour.’
After two months of fearing there may be something seriously wrong, Marilyn finally went to the GP, only to discover an unlikely culprit.
During the January lockdown, Marilyn Law thought she was doing the right thing in using her new exercise bike to keep fit while gyms were shut
The GP gave Marilyn a print-out about possible causes of her headaches.
‘I looked through the list of triggers, and one of them was excessive exercise and profuse sweating,’ she says. ‘I thought: ‘Bingo! Now I know how to cure myself.’ ‘
Sure enough, Marilyn stopped cycling for three weeks and then gradually reintroduced her sessions — starting with 20 minutes one day a week — and the headaches disappeared.
Exercise — while being beneficial in cutting the frequency of some headaches — can, confusingly, trigger them, too: from mild to the sudden severe pain experienced by Marilyn and even migraines (which causes not just a severe headache but also has other symptoms such as nausea).
A 2013 study in The Journal of Headache and Pain, involving more than 100 migraine patients, found 38 per cent had experienced exercise-triggered migraine, often starting with neck pain.
More than half quit the type of exercise that had triggered them and found they could safely practise lower-intensity exercise without developing a migraine.
The study suggested one explanation for this could be that higher lactic acid levels (a natural by-product of exercise produced in the body) in the brain can lead to higher migraine frequency, possibly because people who are susceptible to migraines may metabolise lactic acid more slowly.
Another theory is that many exercise-induced headaches are triggered by an increase in intrathoracic pressure (in the chest).
Sure enough, Marilyn stopped cycling for three weeks and then gradually reintroduced her sessions — starting with 20 minutes one day a week — and the headaches disappeared
When you’re lifting a weight you tend to hold your breath and push the weight up with the diaphragm and chest,’ explains Dr Ben Turner, a consultant neurologist at London Bridge Hospital.
‘This intrathoracic pressure feeds back into the brain and can destabilise the nerves, and by altering the vagal nerve (which runs from the head to the abdomen), it possibly makes the brain more unstable.
‘People can feel as if their blood vessels are pounding in their head, but it’s been debunked that these types of headaches have anything to do with the vascular system.
‘Going back to the gym after lockdown, and doing sudden bursts of activity are risk factors,’ he adds. There is a telltale sign of headaches brought on by exercise.
‘Exercise-induced headaches should usually get better within an hour,’ says Dr Turner. Research has found that the type of exercise is important, with headaches sparked by weight-lifting typically lasting only a few minutes, whereas those triggered by aerobic exercise, such as jogging or cycling, last an hour or more, and may be aggravated by dehydration, heat or hypoglycaemia (low blood sugar).
Running or jogging was the main culprit, with 6 per cent of women citing cycling as a trigger, according to a study of 129 people who get exercise-induced headaches, reported the Journal of Sports Medicine in 1994.
And a 2008 study published in The Journal of Headache and Pain suggests that around 1.5 per cent of headaches are brought on by exercise and other forms of exertion.
The study monitored more than 6,000 patients prone to headaches provoked by one of three types of exertion — coughing, sex or exercise — for ten years.
It found coughs to be the most common trigger, accounting for 70.1 per cent of exertion-induced headaches, followed by sex (18.6 per cent) and exercise (11.35 per cent). The study found that the average age for onset of exercise-induced headaches was 40.
To avoid these, Dr Turner says: ‘Build up your workout slowly. If you get headaches from one type of exercise, try a different type.
‘Exercise-induced headaches remain a bit of a mystery — they start and persist for a while and then they disappear again, but may return a few years later.’
However, as Dr Turner explains, while people often seek one specific trigger for their headaches, it’s more likely they are caused by a combination of factors.
‘It’s all about homeostasis [the ability to regulate our internal mechanisms],’ he says. ‘Nerves want to be in a perfect condition. Hormones, dehydration, hypoglycaemia, periods can make your nerves unstable, and make you more likely to get headaches.’
Marilyn, who had not previously had regular headaches, knew none of this when she took to her exercise bike, given to her by her son and daughter-in-law in December last year as a silver wedding anniversary present.
Research has found that the type of exercise is important, with headaches sparked by weight-lifting typically lasting only a few minutes, whereas those triggered by aerobic exercise, such as jogging or cycling, last an hour or more, and may be aggravated by dehydration, heat or hypoglycaemia (low blood sugar)
‘Like everyone else we had put on a ‘corona stone’, which was a bit of a worry,’ she says.
‘In normal times, I do a weekly exercise class with friends and am always out and about, but in the January lockdown it was hard.
‘I wasn’t keeping fit by gardening and walking as I had before, and it can be difficult to motivate yourself to do online classes.’
So Marilyn threw herself into exercising on the static bike. Within two weeks, the headaches had started.
The first lasted for three days, clustered around her right eye and causing it to weep.
Marilyn suspected a deterioration in her eyesight, but a trip to the optician confirmed her eyes were healthy.
The headaches continued with excruciating regularity.
‘I always say I have to be virtually dying to take a paracetamol, but I was just popping them to relieve the pain,’ she says.
‘I was walking around with dark glasses as one eye was weeping. I made a note of the headaches and their symptoms — they’d start on one side and then move. By the end of February, I was feeling it across my whole head.’
Marilyn stopped exercising for three weeks, and then gradually reintroduced the bike.
‘I don’t use the bike if I’ve gone for an eight-mile walk, or done a lot of gardening, because I think that might trigger my headaches,’ she says. ‘But if I’m not doing much then I’ll cycle.’
She’s also making sure she keeps hydrated. Her GP warned Marilyn that the headaches might last for three months to a year, but since she adjusted her exercise regimen, she’s found that they have disappeared.
However, Dr Turner cautions: ‘Anyone over 50 who develops headaches should be investigated for an underlying cause.
‘The most important thing to rule out is temporal arteritis, which happens in the over-50s and can cause sudden blindness.’
As for Marilyn, she is glad to have found a solution: ‘I feel very fortunate that I have been able to get rid of these headaches — my GP had warned me they could last a while.’