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Exercise: what’s the bare minimum I can do?

Minimum effort, maximum reward

Is it boom time for the fitness business? One in seven people in the UK is believed to be a member of a gym, 2018 saw the number of gyms exceed 7,000 for the first time, and by 2022 the private health and fitness club market alone is predicted to be worth a whopping £3.9bn. Such is the demand for workout spaces that the Financial Times wondered: “Is gym the new pub?”

But other stats suggest that we’ve never been so idle. A 2017 survey from Kantar Public found that more than a third of the UK population never exercise, with the Department of Health estimating that such inactivity costs the economy around £8.2bn each year through treatment costs for lifestyle-related diseases such as obesity, and the indirect costs of sickness absence at work. And a recent study by the World Health Organisation found that little progress had been made in improving physical activity levels in the UK between 2001 and 2016.

While many of us start with good intentions, various surveys suggest that a substantial number of those gym memberships go largely unused, with many of us citing lack of time, or tiredness after work, as the major hurdles. It is perhaps telling that some of the most popular fitness trends on the market are regimes like CrossFit and Tabata, intense workout programmes that promise high gains in the shortest possible time, often a matter of minutes.

Rather than emphasising targets, governing bodies are increasingly adopting an “anything is better than nothing” mantra; so much so that in the past decade, increased amounts of funding and research have been devoted to understanding the minimum amount of exercise we can get away with in order to maintain optimum health.

So what does science tell us?

Existing recommendations

For many years, the official recommendations from Public Health England and the Centers for Disease Control and Prevention in the US have stated that we need at least 150 minutes of moderate-intensity cardio per week – which roughly equates to about five park runs – and at least two sets of strengthening activities, on all of the major muscle groups.



NHS Direct recommends cycling as part of a 150-minutes-per-week cardio fitness regime. Photograph: Getty Images/Image Source

These numbers are based on intensive statistical analysis of more than 40 years of research. Scientists define the “150 minute” mark as the average amount of time where the majority of people will see benefits in everything from cholesterol levels to body fat percentage, sleep quality, mental health, bone density, and even holding back the ageing process.

“We did a study where we took skin biopsies, and in people who exercised regularly we found that the skin looked 20 years younger,” says Mark Tarnopolsky, professor of paediatrics and medicine at McMaster University in Hamilton, Ontario. “And when we took sedentary older adults, and trained them for three months with this amount of exercise, there was a youthening of the skin by about 20 years.”

Scientists agree that 150 minutes a week of moderate-intensity cardio has consistently been shown to extend lifespan by an average of three to four years, as well as a reduction in incidence of everything from cardiovascular disease to depression, and most cancers.

“All the recent data we have on exercise suggests a lot of powerful things with respect to diseases being minimised,” says Jinger Gottschall, associate professor of kinesiology at Penn State University, Pennsylvania. “It’s really motivating to see what can be achieved, but the sad thing is, so many people don’t do it.”

More intensity, less time

To try to make exercise more palatable, scientists have been investigating ways to get the same physiological benefits in much shorter periods of time. When it comes to cardio, one way to do this appears to be upping the intensity, as is the case with Tabata and other high-intensity interval training (HIIT) programmes.



It’s thought that 10 minutes of skipping offers similar benefits to a 45-minute run. Photograph: Getty Images

“There’s good evidence that if you increase the intensity, workouts which involve just a few minutes of exercise in total can still be extremely effective,” says Martin Gibala, professor of kinesiology at McMaster University, Ontario, and one of the scientists who has pioneered research in this area. Scientists think this is because the body registers that it is losing a lot of energy, and so provides more stimulation to key molecular signalling pathways involved in everything from maintaining muscle health to regulating blood-sugar levels. This can happen after 150 minutes of moderate exercise, or far shorter periods of vigorous exercise.

The most extreme end of this is something dubbed the “one-minute workout”, a form of HIIT. In total, it involves three 20-second bursts of all-out exertion, with one to two minutes of recovery in between, a three-minute warm-up, and a two-minute cool-down at the end.

Gibala believes that this can have the same health benefits as a half-hour jog in the park – ideal for busy office workers trying to squeeze in a workout in their lunch break. This is because it’s conducted at the highest possible intensity, up to 90% of your maximum heart rate – roughly calculated as 220 minus your age.

However, HIIT has not been without its controversies. Other scientists have found cases of a rare condition called rhabdomyolysis among HIIT newcomers unaccustomed to the intense strain of these workouts. This occurs when intracellular muscle constituents break down in an uncontrollable fashion and leak into the bloodstream, causing pain and potentially leading to kidney damage if ignored.

Wary of this, governing bodies are holding back on officially advocating these regimes to the public until more data is available on who is and isn’t suitable for HIIT training, and whether it can be done safely over the course of years and decades without risking injuries.

The latest Public Health England guidelines have still tried to embrace higher-intensity exercise, but with a more cautionary approach. They suggest a minimum of 75 minutes of exercise per week at a vigorous intensity: not as full-on as HIIT, but a brisk enough jog or cycle for you not to be able to speak in full sentences while exercising – and as the recommended alternative to 150 minutes a week of moderate-intensity exercise.

“This means you could do three 25-minute cardio workouts a week and you’re meeting the minimum health requirements,” Gottschall says. “That’s still much more feasible for people.”

Exercise more with age

While more intense workouts can cut the amount of weekly time we need to spend on cardio, the same doesn’t apply for other categories of exercise, such as strength training and stretching.



Yoga strengthens our muscles – and we lose 3-5% of muscle in each decade after 30. Photograph: Getty Images

In fact, while pumping iron may be typically associated with young bodybuilders, working on muscle strength and flexibility through sets of weight training or yoga sessions actually becomes more important as we age.

“As you get older, you’re naturally losing connections between the nerves and the muscles, leading to weakness, and eventually lack of independence, and increased risk of falling,” Gottschall says. “But studies have shown that strength training such as cycling on an exercise bike with a high resistance can help negate this, and even improve other things, such as bone density.”

In fact, Tarnopolsky believes that the minimum amount of exercise we need to do to stay healthy increases with age, especially past 50, to the extent where we should try to do some kind of muscle-strengthening activity every day, and an hour of stretching a week.

“Keeping all the balls in the air does take a lot more time as you get older,” he says. “Just doing cardio alone doesn’t help with strength, which is continuously declining throughout middle and old age. Flexibility is more important to work on as you get older, because there’s increased collagen deposition in muscle, which makes you feel stiffer; so stretching keeps your joints healthy.”

While this may sound impractical to some, Tarnopolsky points out that time restrictions are often less of an issue when you’re older. “You have more time to fit these things in, especially once you’re retired,” he says. “And the key thing is, you can always improve what you have. We’ve done many studies with strength training which show that the body does respond, even with people in their 80s who have never done it before in their life.”

Bespoke workouts

There’s also growing evidence that the minimum exercise requirements each of us has to stay healthy is very individual, something that depends as much on our genes as our age.



Running can protect against stroke, heart disease and type-2 diabetes. Photograph: Getty Images

Currently, public health guidelines prescribe the same exercise requirements across the board. However, people who are suffering from – or have a family history which suggests they are genetically at risk of developing – chronic illnesses such as type 2 diabetes, cardiovascular disease, sarcopenia (the degenerative loss of skeletal muscle mass, quality and strength associated with ageing), arthritis and osteoporosis are thought to have a greater minimum exercise requirement than those outside this category. According to Tarnopolsky, “As a rough approximation, these people should probably be exercising 50% more than the minimum recommendation.”

Of course, a regime would need to be tailored to the person’s condition and individual requirements. Those at risk of sarcopenia would probably need to devote more minutes to strength training, while type 2 diabetics are thought to require both more cardio and more weights than the rest of us.

“Blood sugar is greatly impacted by daily bouts of physical activity, so a type 2 diabetic really should be doing cardio every day,” says Gary Liguori, professor of health sciences at the University of Rhode Island. “Blood sugar is absorbed by the muscles, so strength training has benefits too, because if you can increase muscle surface area, that allows it to clear so much more sugar from the blood.”

Persuading people to do even more exercise for their particular health condition, when so few even hit the minimum requirements, may seem a stretch, but Tarnopolsky says this simply shows that our perspectives on exercise need to change.

“We have to start thinking of exercise as a drug,” he says. “Therefore, if you have a strong family history, which indicates a genetic risk factor, or something happens which proves you have that disease, you should make the time. Even if you exercised for half an hour every single day for seven days a week, that’s a tiny fraction of 16 waking hours. And after all, time doesn’t really matter when you’re dead.”