The Gait Guys. Two weeks ago you talked about a dog’s gait, now cockroaches ? Yup, watching nature at work fosters much insight into gait principles.
Biomimetics, also known as Bionics, is another name for engineering systems that copy principles found in nature.
If you are real gait geeks you have probably seen some of the cool robots inspired after the insect world. Many of these robots are called hexapods (six legged robots), just like insects. With 6 legs alternating limbs on opposite sides of their exoskeleton (see diagram above) it can provide an inherently stable tripod mechanism that is effective and efficient in when it comes to locomotion. Insects are great models because they have an extremely stable and efficient model of locomotion through something called a tripod gait. We have a video link demonstrating this a little further down. At any time, cockroaches for example have 3 limbs in contact with a surface. This tripod structure makes them very stable and mobile.
The stability of the hexapod comes from its ability to establish this gait pattern in which at least three legs are on the ground at any time. Just like the 3 legs of a tripod, when they are firmly planted, the platform is very stable. You will notice from our year of blogging that we continue to talk about the foot tripod, consisting of stability points at the head of the 1st and 5th metatarsals and the heel. These 3 points of stability of the foot are necessary to make up the longitudinal and transverse arches of the foot. Without the ability to anchor these 3 points effectively on the ground the foot becomes unstable and compromised. Hence why we see bunions, hallux valgus, metatarsalgia, abnormal plantar callus patterns as well as various presentations of foot pain in feet that have lost the tripod ability. The key however is then to place, and maintain, the body mass within the confines or borders of the triangle made by joining these 3 tripod points (see the colored area in the diagram above). In humans, if your body mass deviates towards the outside of the tripod, in other words approaching or violating an imaginary line drawn from your 5th metatarsal to the heel (ie. approaching supination), you tip the foot laterally and begin to compromise the anchoring of the medial foot tripod (under the 1st metatarsal) and risk formation of bunions and hallux valgus among other functional pathologies of excessive or constant supination. On the other hand, If your body mass approaches or exceeds the arbitrary medial border of the triangle delineated by a line drawn from the head of the metatarsal to the heel you are considered a possible hyperpronator and all of the functional pathologies that accompany it (ie. plantar fasciitis etc). Bottom line … a tripod is stable, just stay withing the colored lines. Note in this cool video (click here) how clear the 3 pronged tripod engages and how the body mass of the robot stays within the borders of the tripod limbs. In other words, keep your ankle and more specifically the force vector, over your foot tripod (the colored lines), and most pathology issues will be absent. The closer you get to tipping the tripod, the closer you are getting to developing biomechanical pathology in the lower limb. Put another way, by increasing weaknesses in the foot intrinsic and extrinsic muscles and possibly the other stabilizers of the lower limb and pelvis, the closer your body mass will fall towards the edges/limits of the tripod triangle borders. And the closer you are to the risk of gait pathology and pain.
( In the diagram above, for you hexapod insect loving gait fans, the most basic hexapod walking pattern is called the alternating tripod gait. Taken from this site, in this gait, the six legs are treated in two groups of three. Either group of three is a tripod formed by the front and rear legs of one side, and the middle leg of the opposite side. The three component legs of each tripod are moved as a unit. As one tripod is lifted, the other tripod pushes forward. In this gait it can be helpful to think of each tripod as a foot and compare it to your own bipedal walking where as one foot is lifted the other foot pushes forward.)
And you still thought we were just your average Gait Guys, didn’t you ?! If it walks, trots, gallops, canters, jumps, runs, jogs or whatever….. we are on top of it. Yes, even if that means cockroaches ! We are here to stay gang, in 2012 we will begin to execute our plan for intergalactic dominance, gait related only of course.
Nerd Shawn & Geek Ivo
The Gait Guys
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