Sometimes Inertia is a Good Thing

At this time last week, I was very stressed.  On Friday afternoon I was nervously comparing pictures and trail maps, trying to figure out what course I would be riding for the King of the Mountain enduro race at Mountain Creek Bike Park. (Race coverage HERE.)

I was was so glad when I realized that we were not riding down the trail named “D.M.L.H.”  We rode it last year, and the name “dude my loins hurt” is well chosen.  Instead, they sent us down a trail named Utah, which included easily the gnarliest rock garden I’ve ever ridden.

Here’s a clip from my race run:

So I got kicked off line and hung up on a rock, no big deal.  You should have seen my first impression of this boulder field, I could barely hike it! I wandered around in the rocks for a bit, until a far braver, ballsier, or boneheaded rider came flying in at speed.

He seemed to float over most of the rocks as if they weren’t there.  That was my lightbulb moment.

In that rock garden, the lines smooth out with more speed.  Your wheels float, or skid, over the holes more than when you’re trying to control every single inch of forward momentum.  It’s inertia.  That made sense, and making it through that rock garden was the best moment of my riding that weekend.

Let’s talk about inertia.

When we discuss inertia and exercise, it’s frequently discussed as a bad thing.  We’re advised to move slowly, steadily, and with great care.  I love all of these things, but how the hell are you going to jump or throw something in slow motion?! Slo mo isn’t real life, people!

At MFF we use a number of exercises that, when well controlled, have moments where there is no control.  If you’re swinging a kettlebell, throwing a medicine ball, or jumping up and down, there are moments when you’re not actually able to stop the weight.  There is enough momentum on your ‘bell, ball, or body, that good ol’ gravity has to catch up first.

For example, look at how the bell floats in front of me when I swing:

I could be setting myself up for some real problems by attempting to slow that swing down enough to control every inch of movement.  It’s not an exercise designed to go slow, it’s an exercise designed to go fast.  When it’s designed to go fast, we should let that happen!

Many of the exercises that we use that focus on creating power, including skipping, jumping, medicine ball throws, and kettlebell swings, all benefit when we allow the implement to move fast.

These exercises are designed to help you move a relatively lighter weight at a relatively faster speed and we see the best results when we allow ourselves to honor that intention.

Speed vs Load

The speed of movement and the load being moved exist on a continuum known as the “Absolute Strength to Absolute Speed Continuum.”  For the real nerds amongst us, Eric Cressey gives a great explanation of it HERE.

This picture provides a quick visual explanation:

As the speed of movement, or velocity, increases, the force we can create is reduced.  That means we can move lighter objects at faster speeds, and heavier objects at faster speeds.  Remember in high school physics when you first learned that Force = Mass x Acceleration?  They should have compared a swing to a deadlift as a reference!

When it comes to heavier objects moving slower, we see this:

And when we see lighter objects moving faster, we see this:

In both cases, the boats are moving at the desired speeds to get the desired results, and I think we’ll all agree on which one looks more controlled to the untrained eye.  The relationship between these boats is the relationship between speed and load that we experience every time we train.

Exercises such as a heavy barbell deadlift or your 3 rep max chin-ups are likely going to move pretty slowly, despite your best efforts to move the bar fast.  Exercises such as a sandbag clean or a lateral hop are going to involved such speed that your body, or the bag, is floating for the briefest of moments.

That is okay.  That is encouraged.  That is you practicing power, practicing control, and getting better.  The inertia is making you better.  It can be a mental challenge, to allow something to float without exacting control the whole time.  That’s how I felt as I smashed through those rocks, hoping I wouldn’t smash myself.  The inertia made it better.

Inertia is your friend. Embrace it.

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