Is staying active enough?

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by Richard Chartrand

Many people believe that, if they are active, doing things like gardening, that they do not require formal exercise. In fact, when asked about why they don’t do formal exercise, they will usually point out that either their job is physical or that they have hobbies that “keep them active enough”.

Dr. Bryce Lee, DPT (www.strength-space.com) is both a doctor of physiotherapy, and he owns a strength training facility that specializes in high intensity strength training. In his article, of the same name as this one, he points out a number of very important points about why staying active alone does not replace proper exercise. The following is excerpted from the longer article on Dr. Lee’s website.

To answer, “is staying active enough?”, we have to define “enough.” Because the last thing I want is to imply that gardening (and many other activities) isn’t healthful. Fresh air, sunshine, and exertion are enormously beneficial, not to mention the deep satisfaction of seeing the fruits of our labors.

But there are some benefits that none of these activities can provide – benefits that are crucial to preventing age related decline in whole body muscle mass, bone density, and insulin sensitivity. It’s a scary fact that even active people can lose muscle and bone at an alarming rate. This starts in our 30’s, and accelerates significantly in our 60’s. Suddenly, we lack the strength and stability to garden, or do all those healthy activities we once treasured. We stop doing them, become increasingly sedentary, and the health consequences increase exponentially. How does this happen?

Our bodies are masterfully efficient. Our nervous systems always attempt to use the least amount of muscle, and to burn the fewest calories, to do a task. This is just sound biology – being efficient means you get to survive during the famine, or hard winter. And the more we do a given task (running, gardening, etc), the more efficient we get.

Maintenance is a myth.

Someone who takes up running will initially become fitter. But it is a cruel irony that if you run exactly 3 miles, 3 times a week, on the same course, and at the exact same speed, you will be weaker, less fit, and possibly less lean 10 years later than you are today. Their bodies will master the task and learn to shut off as many muscle fibres as possible, so the task can be done with the fewest calories burned, and the fewest muscle fibres in need of repair.

Efficiency makes it hard to keep muscle: When we go to exert ourselves, our bodies will always turn first to the smallest muscle fibres, which require the least energy, and recover the fastest. These smaller, “slow-twitch,” fatigue-resistant muscle fibres are the workhorses for most of activity. Small but numerous, our bodies rely on them for all the low to moderate force activities we do – any task that can be sustained for more than a few minutes can be done largely or exclusively with slow twitch muscle fibres.

Our body so efficiently cycles between slow twitch fibres for one purpose – to avoid having to recruit the larger, “fast-twitch,” easily fatigueable muscle fibres. These fibres take much longer to recover: hours, days, or even weeks! This is an eternity compared to the seconds or minutes that slow-twitch fibres take to be refreshed. What is more, when these larger fibres are deeply fatigued, they become very hungry.

Because of this, our bodies only call upon these fibres in true “emergencies,” or situations in which absolutely maximal amounts of effort are required.

Use muscle or lose it! When these fast twitch fibres go unused for long enough, the body, like a sensible business owner, starts asking the hard questions: “Are these big, expensive muscle fibres really necessary?” And that’s when the atrophy starts. After age 30, we lose 3-10% of our muscle mass each decade, and 10-40% of our strength! That means that, by the time we’re in our 70’s and 80’s, we may have lost between 25% and 50% of our muscle mass and strength. This is an unacceptable risk.

Nothing replaces high effort resistance training. Recreational activities like gardening, tennis, or yoga can feel very challenging at times. They can make you sweaty, winded, and quite fatigued. And those are very good things! What they are very unlikely to do is to deeply exhaust the fast twitch muscle fibres throughout your body. We’re just not going to achieve truly max-effort contractions during these activities, and instead tend to accumulate hundreds or thousands of fatiguing but low-force muscle contractions instead. It feels hard, but it isn’t maximal in effort.

Muscle is the best insurance policy for a “rainy day.” Are you comfortable hoping you’ll never get acutely ill or suffer a severe injury? After all, we can also live a long and healthy life without seatbelts or an emergency savings fund. But when an emergency occurs, these things go from “nice-to-have” to “absolutely essential.” Muscle and bone are the same.

We need to understand how muscle and bone are like an emergency savings fund. Maybe we are just strong enough to enjoy our day to day activities, but what happens when we have to spend a month in the hospital due to a severe, acute illness? Or when we sustain a serious fall? We have to start drawing upon this “emergency fund.”

According to the evidence, we need very little exercise to see major benefits. In fact, exercising less than an hour each week can reap many, if not most of the benefits of this higher effort training! By using what we understand about how the body works, we can save an enormous amount of time for what we really love to do, whether that’s playing tennis with our friends, or working in the sun on a new garden bed.

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