CAPABLE of boosting heart, lung and bone health, warding off depression and keeping cancer at bay, it's no exaggeration to call exercise a wonder drug.
And now researchers are discovering another upside: it can improve the effectiveness of drugs, such as those used in chemotherapy. It can also counteract the side-effects of some treatments, with one recent study showing that 30 minutes of moderate-intensity cycling three times a week can dramatically improve the heart health of dialysis patients.
Cardiovascular disease is the leading cause of death in patients with end-stage kidney disease. This is as a result of dialysis; while it helps to remove excess fluid and toxins (which build up as the kidneys fail), over time it can weaken the heart as the fluctuating fluid levels put it under stress.
In a trial run by Leicester University involving 130 dialysis patients, half cycled on an exercise bike at moderate intensity for at least 30 minutes three times a week while undergoing treatment.
The other half received standard care, with no exercise. After six months, scans revealed there was nearly 10 per cent less inflammation in the hearts of the cycling group, the journal Kidney International reported earlier this year.
"Doctors often treat things with a pill, but in order to improve treatment long term, we also want to focus on more innovative ways of tackling the unique risk factors kidney patients face, particularly heart disease," says James Burton, a professor of renal medicine at Leicester University, who led the study.
"Once scarring occurs, it's irreversible," he adds. "But what the study showed is exercise could prevent inflamed heart tissue from progressing to scar tissue which would then be associated with bad outcomes including heart failure."
One reason for this might be that a cellular messenger released from the muscles during exercise causes the heart to turn off inflammation.
The study also noted the cycling group had fewer hospital admissions with kidney-related problems, and shorter hospital stays.
Exercise has been shown to protect against the risk of certain cancers returning, too. A 2019 review of studies showed that the most active people who exercised while undergoing treatment for colorectal cancer were up to 30 per cent less likely to die over the following eight to 10 years.
Keri Schadler, an assistant professor of paediatrics research at the University of Texas MD Anderson Cancer Center in the United States, suggests the benefits may be due to the fact chemotherapy needs to be distributed via blood vessels, but these are "immature and poorly functional" in a tumour.
"Only 50 per cent are carrying blood, and therefore chemotherapy," she told Health & Lifestyle.
"Most of the drugs end up being delivered at the periphery of the tumour, which explains why treatment isn't as effective as it could be."
In a 2019 study, published in the journal Scientific Reports, Dr Schadler demonstrated that exercise increased the number of blood vessels within a pancreatic tumour in mice. She found there were five times more blood vessels in tumours in mice that exercised (on treadmills for 45 minutes a day, five days a week) compared with mice that didn't.
"We treated them until the tumours had disappeared, and the mice that got the combination of exercise and chemotherapy then had slower regrowth of the tumour," says Dr Schadler.
"This showed that chemotherapy combined with exercise worked better when the tumour was present, but also that it seemed there was a delay in regrowth of tumour after the treatment stopped."
But why does exercise have this effect? "The evidence suggests that as you're exercising and your blood is flowing faster, you're getting a stronger mechanical signal on the endothelial cells that make your blood vessels, and that is signalling to those cells to behave differently and become more mature, functional blood vessels," says Dr Schadler.
In a study of pancreatic cancer patients who did 60 minutes of aerobic activity and 60 minutes of strengthening activity a week, Dr Schadler found "significant change" in the number of blood vessels within the tumours compared with patients who didn't do the exercise.
It also has a direct role in mobilising our immune cells, especially natural killer cells which can kill tumour cells; a 2016 trial in the journal Cell Metabolism found that exercise boosts the mobilisation of these natural killer cells.
Further trials are examining the potential benefits of exercise, including one due to start at Sheffield Hallam University this autumn, where patients with cancer of the lungs, colon, oesophagus, stomach and small intestine will be prescribed exercise alongside their cancer treatment, including chemotherapy.
© Daily Mail
