So there is a lot of, ‘Old man yells at cloud‘ with this, but have you noticed that Ducks don’t actually have ‘Duck Feet’?
Look closely, do those feet look like they are pronated to you? On the contrary, if anything ‘Duck Foot’ looks a lot more like supination in actual ducks, NOT pronation. Do we really need to ‘fix duck feet’ in humans?
When we look a little closer, we find that Birds walk on their phalanges (toes) and that the first digit of a Duck’s foot is actually pointed behind. We humans however, are walking on our metatarsals and calcaneus whilst Ducks have a fused structure called the ‘tarsometatarsus’. The metaphorical use of a Duck’s foot in talking about over-pronation quickly starts to collapse.
There is a variation of digital alignment in birds. In Anisodactyl birds (3 toes fore and 1 hind toe), of which Ducks are, you will see further variations in webbing. The alignment of the toes is a key feature in understanding that Ducks are NOT over-pronating when they walk. Over-pronation in humans occurs when the Medial Longitudinal Arch collapses and falls in…….
A Duck just can’t do that, they are on their toes, there is no ‘arch’ that CAN collapse and if anything, particularly in the case of totipalmate birds like Gannets and Boobies, the 1st digit supports the foot medially. The Wood Duck is also like this.
The Ducks’ ‘waddling gait‘ is actually an overt lateral movement of the trunk and lateral displacement/elevation of the hip during the swing phase. It results in circumduction; the foot steps across the midline from a wide abducted position.
Even when underwater, ducks have a gait that positions their ‘toes’ forward, and as noted above, if anything there is circumduction.
Much needs to be made of aquatic vs terrestrial locomotion. The Duck has evolved to Paddle int he water, Walk on the land and also fly……. it is a remarkable combination of adaptations. Remember though, these adaptations did not all occur at the same time, but that they are all present in one animal is worth recognizing and in particular, worth seeing how the terrestrial locomotion shows up in the aquatic. How a Duck walks and recovers its feet from one step into the next also happens in the water and even more worthy is comparing the systems that humans and ducks have to achieve similar results.
In humans, the Windlass mechanism describes the ‘winding up’ of the plantar fascia, creating a pawing or shortening of the foot. It is described here….
All birds however have a system that creates a very similar effect to the Windlass Mechanism in humans.
Birds do not have muscles in their feet. Instead the Avian foot has an automatic clawing system that is acted by the tendons originating in the hip and knee of the bird. As a bird ‘sits’ or perches, the feet automatically grip tight. You may have noticed this with a pet budgerigar that grips your finger automatically. A shortening during a perching or sitting action by the bird will create a griping and clawing of the toes.
Humans do not use their feet in the water to swim like a duck does, the duck paddles, the human uses a fin and flipper locomotion. But just as the human has the Windlass Mechanism in walking, the ‘Digital Tendon Locking Mechanism of the Avian Foot’ assists with the hydrodynamic effect of the swing phase of a Duck’s paddling stroke. As the foot is recovered, and swings forward again, the Digital tendons act to minimize the profile of the foot in the water. It reduces the drag.
There is no doubt that there is much to be concerned about with over-pronation in humans. In the coaching of lifting, running, football and gymnastics, over-pronation will stick out immediately. Its not a particularly difficult phenomena to get an improvement with, indeed the interface with the ground by the foot is a massive part of improving lifting, running, football and gymnastic skill anyhow, so in un-coached individuals, application to the efficient model of any of these skills can improve over-pronation just by itself.
I don’t think its the case here, but its worth considering whether the misapplication of Avian foot mechanics as a metaphor can lead to a misunderstanding of human gait, stultifying the remedies.