SPEAKER_07 16:41–19:22
And why do I talk about the imaginary sagittal plane? Because where does it go? Like, okay, we're straight ahead. Is it where your eyes are? Is it where your nose is? Is it where you're high eyed spacing? Is it where the pubis is facing? It's like, okay, where's the sagittal plane that everybody's talking about? It's like, give me a point of reference. Dead guys have a sagittal plane. They don't move. Good morning. Happy Wednesday. I have no coffee in hand and it is perfect. All right. So, today's Wednesday, that means tomorrow's Thursday, that means tomorrow's 6 a.m. Coffee and Coaches conference call. As usual, I think we're on call 103 or something like that. So we've been doing these for a while. Always a great time, great Q&A, grab yourself some coffee, and please join us. Digging in today's Q&A. This started off with Andrew, got a little help from Ian, got a little help from Max. And basically what we're doing is we're talking about how we use ground contacts to create relative motions. And so the foot's a great example of that in a number of cases. If you think about the bottom of the foot, as long as we have our four boning contacts, so two on the heel and first and fifth metatarsal heads, that's the foot contact that's going to provide us the greatest degree of relative motions. Generally speaking, we're forming a quadrilateral on the bottom of the foot, and that allows us to make these cool little turns and twists from ER to IR. If we lose any of those contacts, then we get a shape change that's no longer quadrilateral. If we have something that would move, say, into a triangular shape, so I lose one of my contacts, I now have a triangle, which is actually a very stable structure, and that's actually going to reduce relative motions. When we talk about propulsion that can involve walking, it can involve rolling, which we talk about in this video, is that we want to have those contacts with the ground. As long as we have those effective contacts with the ground, that's where our relative motions lie. When we don't have those, that's why we don't have relative motion. So when we're measuring people in the table, we're looking for the shape that is in physical contact with the ground or in this case with the table, that's going to allow us to be able to demonstrate the relative motions. When we have the shape change available to us, we can acquire the appropriate shapes in contact with the ground and we have relative motions. So, thank you guys. Appreciate the question. A great deal. If you'd like to participate in a 15-minute consultation, please go to askbillhartman at gmail.com. Askbillhartman at gmail.com. Please put 15-minute consultation in the subject line so we don't delete it. Please include your question in the email. We'll arrange that at our mutual convenience. Everybody have an outstanding Wednesday. I will see you tomorrow at 6 a.m. Coffee and Coaches Conference call. See ya.
sagittal planeground contactsrelative motionfoot mechanics