My Elbow and Non-Newtonian Fluids

When my physiotherapist measured my elbow extension two weeks ago, it was at -20º. This morning’s measurement was -6º.

I’m really happy about that.

As Lisa will attest, I’ve been annoyingly religious about doing my physio three times a day.

With my eye on the 0° prize, this hasn’t been as difficult as I thought it would be. This means that, more often than not, if you were to pop into our house by surprise, you’d find me lying on the couch with a 5 pound weight hanging off the end of my right arm.

My physio program got updated again today, and for the next two weeks, here’s what I’ll be doing:

Forearm Pronation and Supination with Dumbbell
Supine Elbow Extension with wrist in neutral
Putty Squeezes
Supine Elbow Flexion
Elbow Extension Mobilization
Seated Wrist Radial Deviation with Dumbbell
Standing Single Arm Bicep Curls Supinated with Dumbbell
Seated Wrist Flexion with Dumbbell
Wrist Extension with Dumbbell
Standing Alternating Triceps Extension with Dumbbells

To think that, just three months ago, I would’ve had no idea what pronation and supination were. Now I live and breathe them.

It’s been 10 weeks since I fell off the box and injured my elbow an 8½ weeks since my surgery. My arm is still uncomfortable, at least a little, most of the time. I can’t reach as far as I’m used to, and I certainly can’t lift what I used to. But doing the physiotherapy, and seeing it demonstrably pay off, helps bolster my faith that, eventually, this will all be a satisfying memory.

Those “putty squeezes” you see in the list of physio exercises are done with a ball of goo called “therapy putty” that looks and behaves a lot like the Silly Putty of my childhood. It comes in different colours, each denoting a different amount of resistance it offers. I started with yellow, and have levelled up to pink.

One of the interesting characteristics of therapy putty is that the harder you squeeze it, the more resistance it offers.

This is because it’s what’s called a non-Newtonian fluid:

In physical chemistry and fluid mechanics, a non-Newtonian fluid is a fluid that does not follow Newton’s law of viscosity, that is, it has variable viscosity dependent on stress. In particular, the viscosity of non-Newtonian fluids can change when subjected to force. Ketchup, for example, becomes runnier when shaken and is thus a non-Newtonian fluid.

I prefer to think of it is simply being kind of freaky, slightly outside nature.

Here’s a time-lapse video I shot showing it slumping slowly, over several minutes, from a ball into a lump: