Arches are gorgeous structures. Back in the days of the Roman empire when masonry was the primary construction material, the only way to span an opening was the arch. Be it windows, doorways or bridges, arches were the structure of choice to create a span out of brick or stone. Arches are compressive structures, and work brilliantly with stone since that material can really take the pressure.
The fascinating things is that we also find arches in our skeletal structure.
There are a pair of bones in our forearm: if you held your hand out with your thumb up, the bone above will be the radius, and the one below the ulna. It’s very similar to the midjoint (or wingette) of a chicken wing. One bone is stronger in compression and the other in tension. That’s because in the wings of a bird, the leading edge of the wing (the radius) during flight is pulled in tension, and is supported by the ulna which, like the force couple in a beam, goes into compression. A compressive member has a tendency to buckle, so that bone also develops thicker. And guess what shape is the ulna? Yep, a gentle arch!
When we look at the human foot, we see the arch once again in this magnificent piece of architecture. The metatarsal bones form arches in two ways: longitudinal and transverse. The large bone called the talus at the top of the arch acts just like a keystone. And just like an arch the foot was designed to take a fair bit of load, but that’s assuming you load it compressively.
Modern running shoes have a wedge-shaped mid-sole, giving lots of cushioning in the heel. Now that’s not a bad idea for walking shoes since we land on our heels when we walk. But it does leave one to wonder how people ran before the age of high tech shoes? It turns out that this running gait, known as heel strike, was only possible with heavily cushioned shoes that allowed the same gait between walking and running. Try running barefoot that way and the pounding on your knees becomes so unbearable your legs either protest and stop moving, or correct themselves by landing on the balls of your feet, known as forefoot strike.
With a forefoot strike, the foot gets to mobilise the entire foot structure. And the amount of shock absorption is quite phenomenal.
1. Landing initially on the fourth and fifth metatarsals, the foot flattens the transverse arch and rolls till the entire ball of the foot engages.
2. Then it compressing the longitudinal arch between the weight of the runner and the ground. As the weight bears down, it elongates the tendons under the foot (plantar apeoneurosis).
3. The foot that worked like an arch now works more like a roof truss, with the top chords in compression and bottom chord in tension.
4. This tensile force pulls around the ankle (archilles tendon) which is resisted by the calf muscles to cushions the heels from impact and stores the energy for a rebound.
If that all sounds too complicated, forefoot striking is exactly what you do when jumping, both feet together, like on a skipping rope.
It’s simply amazing how much architecture and engineering goes into our foot, and all that gets bypassed when we heel strike. Together with the revised gait I also switched to shorter strides, faster cadence, and a more upright posture. It took me some getting used to, and I had sore calves on most days. But aching muscles recover with a massage and a few days of rest. That’s way better than a heel pain (plantar fascitis), shin splints or the ultimate price of worn out knee cartilage. Suffer any injury and running becomes sheer punishment.
It turns out that this way of running is extremely natural, if only our feet received sufficient feedback. So in came the concept of minimalist shoes that are designed to protect from cuts, but are otherwise as unobtrusive as possible. I’ve given a good go of a few hundred kms on the New Balance Minimus and enjoyed them a great deal. In a recent trip to Melbourne I was finally able to try on some Vibram Five Fingers. They are quite different from regular shoes so you really have to try them to ensure you’ve got the right fit. Running with them I was blown away. Just by giving each toe a bit more individuality to express themselves. There is a nuanced but distinct sequence between each metatarsal when I land and take off. Guess what? That just made my feet happy. The feet can take a pounding, and they seem really happy when the whole structure is mobilised as intended, and each member allowed to do what it does best. Happy feet, happy runner!
I don’t measure my runs by distance or time. It has become simply a matter of enjoyment running pre-dawn under a starlit sky along the river. Bounding away on the gravel track like a happy deer in my ridiculous five finger shoes, I’m singing in my head,
Who but the Lord is God? but he who is a rock and stay?
‘Tis God that girdeth me with strength, and perfect makes my way.
He made my feet swift as the hinds, set me on my high places.
Mine hands to war he taught, mine arms brake bows of steel in pieces.
(Ps 18:31-34, Scotttish Metrical Version)