I want to talk about the um the Kinesiology um um of the muscle force and uh what's its impact to the spine um typically if you look at this picture right here and uh if you have a mirror I encourage you to look into the mirror um I wonder how much your posture is like this gentlemen uh if you're quite similar to him um you're in danger um you need to listen to next uh to next lecture uh carefully okay um I'm going to uh walk you through uh this um so if we look at the neck um let's look at the picture first um if um this person sit um um in upright position the add is in in the in the Middle with neutral position right like this um um this is like we talk about it's a classic um first class lever system okay um the the weight of the head kind of kind of function you know in in this direction and then the neck extension kind of counter um the weight of the head so if the head is in upright position the liver arm is close to zero right so uh the neck extensor kind of need kind of minimum um muscle Force to maintain the head in upright position so this per this lady won't feel uh too much trouble or um um weirdness after um using her cell phone like this okay so if um she kind of Bend her neck to about 45° um checking her uh cell phone which I bet uh 80% of um you including me are having this kind of position like this so what it what it ca us is the head is in uh 45 degrees uh flexion the moment arm is longer you know when you compare to the um um upright position right with the same weight but longer uh moment arm that in that create a larger uh external torque which means you uh the neck extensor we will will need to generate a lot more muscle Force to counter and remember when we go over the um the structure of the spine and the uh and the muscle the muscle has a very little short moment arm so you know whenever the moment arm can increase U when you bend the neck a lot more muscle force is required to counter and not to mention you if you bend the head more okay so what that causes is it when if we uh keep in the flection position for a long time we add more stress on on the sepine and the dis is more at risk um to develop um herniation or rupture okay so the longer the head uh that we keep in the flex position the greater um effect of the gravity that you can expect and that means the more uh strength are required from the erector spin a to kind of counter the head okay and what I causes is you know um that would lead to poor coordinate bilateral activation of the the sternal cidal muso if we keep our our head in this position a long time right and like we talk about the SCM muscles kind of uh couple with longest cly that uh that do the the tuen change uh kind of position right so if um um one person is keeping the head in flexion and that person may have difficulty in chewing and swallowing because that talking um the chin movement is lacking okay and what should we do oh we should always encourage people to maintain the upright position right and and if you can't well try and um make frequent breaks okay and doing the breaks uh you can you can do uh some stretch to the neck either uh to faction and or sorry either to fraction or um extension or fractor and extensor okay so let's move our Focus to the trunk right here so see this gentleman because he's carrying uh you know big U boxes or heavy boxes so what I what I mean is um um if the box is too big the center of gravity is really at the center of the box right so it um it it um the the moment arm will be longer compared to smaller box right here right and um if it's heavier if it's heavier again we typically kind of kind of live it um we want to to make it closer to the body because the the momentum is shorter that the torque is smaller however um we tend not to do so uh when we carry a heavy object because we we like to lock our um elbow and shoulder but instead of using that we uh we can extend or we're going to compensate with our spine by you know Le leaning backward so it's it feels easier but in in uh it it it kind of increase the stress to the L spine when we do so okay if this person choose to stand upright for carrying these big box again you have longer moment arm compared to the smaller box again that would require more strengths uh uh require uh more strength from the erectus SP name okay and same thing here when you bend over say uh drinking water U from the fountain again that that ankle will will increase the the um um moment arm as opposed to standing upright right now your center of gravity of the upper U body is kind of moving from here to here right because you bend over that increase the moment arm that would get that would require more um from the erector SP a and again we'll put more stress on the L spine especially L4 and L5 because that allows more movement over there okay and that is why um people typically develop um kind of pan at the uh at the uh waist or L4 L5 level or the C spine okay well because we are you know right now we are U becoming a zombie uh using the cell phone or we kind of use a a not so good posture of in our daily life so a lot of us according me we have pain or chronic pain at the spine like C spine or L spine okay if you're not convinced try um this slide how many of you how many of you um have this posture when you're using your laptop um you kind of do a little bit kyphosis and then your pelvic kind of tilt posteriorly uh to compensate this kyphosis you uh have um U active cervical lores to help you kind of um gaze to to to operate the computer or you see uh in this way so you have that pelvic kind of tilt to one side so all these would just add more stress either to the Lumar or to the C spine okay and in the long run we're going to hurt ourselves okay and uh it is our um responsibility as an ot to help uh to uh correct or make uh the performance of this occupation better and we will talk more about about that next week so this week is just a int introduction of how our posture can affect um the spine thank you