Trends & Features

Why your running shoes should be carbon-free

Way back in 1500, Leonardo da Vinci knew that, ‘The human foot is a work of art consisting of 26 bones, 107 ligaments and 19 muscles’. He was right: with the human foot, Mother Nature created an anatomical wonder which can change from a flexible, adaptable shock absorber to a rigid, propelling lever in the space of milliseconds.

In biomechanical terms, this is how it works: the foot is built as a kind of twisted, spring- like plate with toes attached to the front to anchor the plate to the ground. When the foot touches the ground, the plate unwinds and extends to absorb the impact. The plantar fascia pulls the toes into the ground (reverse windlass mechanism), anchors the foot and provides a stable foundation. When the runner’s weight starts to move across the foot, the heel lifts off the ground, using the toe joints as pivots (windlass mechanism). Now, it is the toes’ turn to pull on the plantar fascia, which lifts the arch, twisting and shortening the foot to make it a tighter, firmer spring in readiness for the all-important push-off phase of running.

‘Nature perfected’ instead of ‘nature corrected’

To create the perfect running shoe, the sports shoe industry should basically imitate nature and perfect it as much as possible. However, its so-called innovations such as carbon plates actually tend to work against nature. This is because running shoes with carbon plates and a heel-to-toe drop keep the big toe at a fixed angle throughout the ground contact phase, almost as if it were in a plaster cast. The joints and muscles are immobilised when they would be actively working if they were in their natural state.

Anyone who has ever broken their arm or leg knows all too well what happens when muscles cannot move: the muscles inside the cast very quickly lose their strength and the arm or leg becomes weaker. Running shoes with carbon plates cause a similar phenomenon.

Imagine a marathon runner. He takes an average of 40,000 steps between the start and the finishing line. This means that the muscles in his toes contract and relax 40,000 times during the marathon; his toe joints work within their natural range during push- off. Stiff carbon plates usually have an excessive heel-to-toe drop which substantially restricts the toe joints’ range of motion and muscle activity in the toes. This affects the four muscles attached directly to the big toe in particular.

Weak toes increase the risk of injury

The toe-spring effect causes the muscles to become weak and deconditioned. The forefoot becomes unstable and the foot’s natural ability to transform itself into a rigid driving force for push-off is inhibited. This considerably increases the risk of pain in both the forefoot and the heel (plantar fasciitis).

We would be much better off taking Leonardo da Vinci’s view and seeing the human body as a fine-tuned machine which does not need any help. If we mess with this machine, we upset the whole mechanism and end up losing the one thing that every runner wants: a lifetime of pain-free running.

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