Read time: 4 minutes

Lean bodies.

Rippling muscles.

A “balanced and visually pleasing” combo of muscle size, definition, and symmetry.

Some people are interested in the “aesthetic” benefits of exercise.

And that’s fine.

But there’s much more to fitness than how we look.

Or even how we feel.

It’s about what it means for your ability to stay independent - for longer.

Because once your fitness drops below a critical threshold, daily tasks you take for granted suddenly become a real grind.

Or worse - they become impossible.

And that critical fitness threshold is probably closer than you think.

All physical tasks have a metabolic “cost”

Movement requires muscle activity.

And muscle activity requires (metabolic) energy.

This means any physical task requires a certain amount of energy to perform.

A metabolic “cost” - if you will.

Here’s the energy requirements (as oxygen consumption or VO2) of common daily tasks:

The values shown are compared to the typical peak oxygen consumption (VO2peak) of someone with heart failure (15 mL/kg/min).

As you'll see later, this is just below the aerobic fitness needed to be physically independent in most daily tasks.

The point is, depending on your fitness level, a given physical task will demand a different “slice” of your fitness.

For some people, this slice is bigger than for others.

And for others, it’s so big it exceeds their maximum capacity.

The task becomes impossible.

At this point, quality of life - which is closely tied to your physical independence - suffers too.

This is what it really means to lose your fitness.

But what aspects of fitness are most important?

Let’s start with aerobic fitness

There’s a clear link between your aerobic fitness and your ability to perform daily tasks.

So what exactly is your “aerobic” fitness?

It’s your ability to consume and use oxygen (within your cells) to produce energy.

Your maximum capacity to do this is called your VO2max (maximum rate of oxygen consumption) - which is typically measured in:

• Millilitres of oxygen
• Per kilogram of body mass
• Consumed per minute (mL/kg/min)

The higher your aerobic fitness, the easier physical tasks become - because they require a smaller “slice” of your total capacity.

But once your aerobic fitness dips below a certain threshold, tasks get a lot harder (because that slice gets much bigger).

And below a certain point, the same tasks become impossible.

This so-called “disability threshold” for aerobic fitness is estimated to be 18.3 mL/kg/min.

For context, here’s how average VO2max values compare between those who are active and inactive across the lifespan:

As you can see, the VO2max of those who are inactive gets pretty close to (if not below) the disability threshold - particularly in their later years and especially if they have a chronic disease.

But those who remain active stay well above the dreaded red dotted line - for longer.

Being strong and powerful is critical too

Physical tasks of course require a certain amount of force (strength) to perform.

And the rate at which force is produced (or power) is often important too.

So is there a specific level of strength or power that protects against disability (like there is for aerobic fitness)?

This is a harder question to answer.

That’s because strength is very task-specific (much more than aerobic fitness).

This means how "strong" you are depends on:

• How your strength is tested (in particular the type of task performed)
• Which in turn influences how your “strength” impacts daily tasks

Despite this, there are clear links between muscle strength and physical task performance.

A 2020 meta-analysis of 45 studies found low measures of muscle mass, strength, and physical performance increased the odds of worsening performance in activities of daily living (by up to 3.5 times):

The bottom line?

If your performance in any of these measures drops, your risk of losing your independence goes up.

The impact of crossing the “disability threshold”

We’ve already touched on what happens if your fitness crosses the so-called “disability threshold”.

This of course renders many physical tasks either not possible or very difficult.

And this has an obvious impact on day-to-day activity levels.

It drops of course.

And from there, a viscous cycle ensues.

Lower fitness leads to more disability and less activity, and less activity leads to more disability.

Ultimately, those who become dependent in activities of daily living may not ever regain that function.

A 2004 study of 754 adults aged 70+ who were initially competent in daily activities and living in the community found that over the next 51 months (median follow-up):

• 56% experienced disability in 1 or more of 4 activities of daily living (bathing, dressing, walking, or transferring)
• But of these individuals, 81% recovered their independence in all 4 activities within 12 months

So, all hope if not lost if this does happen.

But there’s one thing that reduces the risk of losing the ability to perform daily tasks in the first place.

It’s physical activity of course.

A 2013 meta-analysis of 9 studies in over 17,000 participants found physical activity at medium/high levels reduced:

• The risk of disability in activities of daily living occurring by 49%
• The risk of existing disability getting worse by 45%

These figures show physical activity prevents or halts the loss of independence with ageing.

There’s only one solution here.

And that’s to remain as active as possible - for as long as you can.

To avoid losing the ability to perform daily tasks in the first place.

Being generally physically active can help - but including resistance training exercises in your repertoire, particularly those that mimic daily tasks - is even better.

So if you’re earlier in your life, there’s never a better time to start.

And if you’re older, it’s not too late either.

Because there’s much more to fitness than just looking better.

Your very independence and quality of life depends on it.

As always, thanks for being here!

Until next Saturday,

Jackson

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IMPORTANT:

The information contained herein is of general nature only and does not constitute personal advice. You should not act on any information without considering your personal needs, circumstances, and objectives. Any exercise program may result in injury. We recommend you obtain advice specific to your circumstances from an appropriate health professional before starting any exercise program.