Strength training linked to reduced risk of cancer
Growing research suggests the right kind of exercise helps beat cancer
Only couch potatoes could claim not to care about the benefits of regular exercise. Physical activity promotes general health and wellbeing.
In its cardio incarnation, it keeps your heart beating to a healthy rhythm, which helps protect you from heart attack and stroke. But regular exercise doesn’t just protect you from cardiovascular disease, it reduces your risk of many other diseases. Growing research suggests the right kind of exercise also helps beat cancer.
Like many people, when you think of "exercise" you probably think of walking, running, working out on a treadmill, swimming or other aerobic activities that get your heart rate up. Also like many people, you may overlook the value of strength-building exercises, particularly for cancer prevention. Or you may think it’s mostly for bodybuilders.
Zimbabwean sports and lifestyle physician Dr Austin Jeans is a big fan of strength-building (resistance) training. He defines it as training against a "progressive load primarily to develop increased muscle strength and size, in other words, increased lean mass".
There are several ways to subject muscles to a resistance-training load, Jeans says. These include body-weight exercises, using elasticated resistance bands, free weights, dumbbells, kettle bells or water-filled containers and gym machines.
Just doing a plank for a minute daily in the privacy of your own home can be good enough. A plank is also known as a front hold, hover or abdominal bridge. The experts call it "an isometric core strength exercise that involves maintaining a position similar to a push-up".
The experts also say that once you reach your 50s, if you haven’t started strength training, now’s the time to start. Harvard medical school physicians say strength training is critical to preserving the ability to perform "the most ordinary activities of daily living". In other words, it’s key to maintaining an active, independent lifestyle as you age.
Dr Robert Schreiber, an instructor in medicine at Harvard Medical School, says: "Unless you are doing strength training, you will become weaker and less functional."
YOU DON’T STOP EXERCISING BECAUSE YOU GROW OLD. YOU GROW OLD BECAUSE YOU STOP EXERCISING.
But should we all do resistance training to protect ourselves from cancer? Jeans thinks it’s an excellent idea. He cites a large 2009 Swedish study suggesting that "big muscles cut cancer risk by 40%" — as one media headline put it. Data showed that male bodybuilders are "40% less likely to die from cancer than men who never pump iron".
The same report noted that "the risk of dying from cancerous tumours was slashed even if men who lift weights had bigger than average waistlines or were overweight".
Most recently, an Australian study of 80,000 adults over the age of 30, published in the American Journal of Epidemiology, was even more encouraging. The University of Sydney researchers found that strength training was significantly more likely than cardio training to prevent cancer-related death.
Those studied who did strength training just twice a week were almost a third less likely to die from cancer. And while those who combined aerobic and strength training showed the best outcomes overall, data also showed that aerobic exercises alone did not reduce the risk of dying prematurely from cancer.
Of course, these studies are all epidemiological (associational) and, therefore, don’t show causation. Lead author Dr Emmanuel Stamatakis, from Sydney University’s School of Public Health, has acknowledged the limitations. "Assuming our findings reflect cause and effect relationships, [strength training] may be even more vital … to reducing risk of death from cancer," Stamatakis said.
But there’s good reason that researchers are focusing on novel ways to fight cancer.
Medical scientists are increasingly looking at cancer as a "metabolic" rather than purely a disease of damaged cell genetic machinery, says Jeans.
"Many cancers, especially those with an endocrine [hormonal] component, such as cancer of the colon, breast, prostate and pancreas, evolve and worsen in the presence of bodily inflammation, high insulin and elevated blood glucose levels [and associated insulin resistance]," he says.
Inflammation is like the "fertiliser" for cancer growth and cancer cells prefer sugar [glucose] for their energy needs, Jeans says.
Obesity also increases the risk of endocrine cancers. Healthy muscle (lean) mass as a consequence of resistance training has the potential to cut cancer risk through several mechanisms, he says. These include reducing inflammation, blood sugar fluctuations and body fat and improving muscle insulin sensitivity.
That’s especially the case with unhealthy "belly" (visceral) fat that is highly inflammatory.
Jeans isn’t suggesting that you should opt for resistance over cardio training. A balanced fitness programme ideally comprises components of both as well as stretching.
However, it’s important to emphasise, he says, that the most effective way to improve muscle strength and lean mass with the consequent positive rewards of that muscle gain is through a resistance training programme. How often you need to do resistance training to get the benefits? That depends on your aim. For health rather than sports performance or bodybuilding, Jeans says the general principles are:
Training sessions two to three times a week;
Performing two to three sets of each exercise involving major muscle groups in functional whole-body type exercises;
Six to 12 repetitions of each exercise to near failure to stimulate muscle growth.
How long before you’ll see visible improvement? Early strength change is measurable within six weeks of starting an effective resistance training programme, Jeans says. "True muscle growth requires three to six months of training."
And benefits really are legion, he says. Along with reduced cancer risk, others include reduced risk of type 2 diabetes and metabolic syndrome (prediabetes), improved blood pressure and blood lipid profiles that also reduce heart disease risk, and increased bone density that reduces osteoporosis risk.
Strength training also increases musculoskeletal function and gives a "younger" muscle physiology in older adults. That reduces the known risk of 2kg to 3kg muscle loss on average in adults per decade of inactivity from 20 to 80 years of age.
Like all good things in life, resistance training can pose risk. Contraindications include recent muscle injury or joint conditions; heart issues, such as high blood pressure; lower back pain; muscle weakness; and uncontrolled diabetes.
The late US aerobics guru Dr Kenneth Cooper said: "You don’t stop exercising because you grow old. You grow old because you stop exercising."
• Sboros is editor and publisher of Foodmed.net.