💁Bodyweight: How bad is too much?

LIFETIME HIP & KNEE

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#028: Bodyweight: How bad is too much?

Evolution has relentlessly moved us upright.
Upright, into a beanpole posture.

Think about how our ‘snouts’ have shrunk.
Shrunk, and almost disappeared.

How difficult would it be to run upright if they hadn't?
With, say, the snout of a donkey?

The biomechanical cost of moving a large nodding snout would be ENORMOUS. What a picture that conjures up...(!)

Indeed, the biomechanical cost of moving any extra bodyweight around is HIGH. And we don't have anywhere else to put extra bodyweight, other than away from the midline. Away from evolution's beanpole-like plan.

What's in ~10cm?

The ~10cm from our midline to the centre of our hip has been hard fought over.

Recent evolution DOUBLED the size of our bodies while TRIPLING the size of our human brain.

Our BIG brain IS our survival advantage. But the BIG head that contains it indirectly plays havoc with our hip biomechanics.

Evolution negotiated the birth of that BIG head against the biomechanics of everyday walking.

I’ll tread carefully with this next sentence...

Childbirth would be a LOT easier if the centre of the hip was 15cm from our midline. A much wider pelvis...

BUT our bum muscles would not thank us.
They'd have to pull with 50% more force.

AND our hips would not thank us.
As all of that force multiplied through our joints.

So ~10cm it is.

The right biomechanical balance to maintain our healthy hip joints.

AND the reason why any excess bodyweight only multiplies by FIVE.
BUT multiplies by FIVE, every step we take.

AND we take over ONE MILLION steps per year.

One stone OVERWEIGHT (that's 14lbs or 6kg) is like hitting our joints with a 5-stone mallet (that's 70lb or 30kg) ONE MILLION times per year.

No wonder our hip hurts.

That back of an envelope calculation points to the cost of excess bodyweight.
That's the biomechanics of excess bodyweight.

If that mechanical disadvantage was not bad enough, there is increasing evidence that obesity affects our biochemistry.

Obesity ⬆ inflammation

Whole body inflammation....

That is, obesity increase the level of inflammatory mediators in our bloodstream.
Mediators that are the essence of inflammation

Mediators that circulate in the blood from excess body fat.
Circulating, and interacting with local mediators that inflame our joints.

Obesity is therefore DOUBLY bad

Both mechanical force and whole-body inflammation go up.

Go up, and combine to cause joint inflammation and pain.

Biomechanics and biochemistry.

All very well.

BUT how does the biomechanics and biochemistry of joint pain translate into the real world?

John, Mr Jones, George and Iain were hitting their joints with the equivalent of a 250kg mallet. Over ONE MILLION times per year.

Each had destroyed at least one joint.

Individual people and cases make for good stories.
But let's combine the stories of many people.
Let's take a look at the evidence...

The evidence for how excess bodyweight affects our joints when we look at 100s of people together.

AND before that, let's take a look at how a less clear cut example came about. Amanda's story comes next...

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Good luck, and see you next week :)

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