The Plumb Line PDF

In standing posture, small amounts of concentric & eccentric contractions happen all the time but overall looks like isometric story How do we ”stack” up relative to gravity? Body's mass is equally distributed from front to back & side to side Theoretically requires least amount of muscular effort...

In standing posture, small amounts of concentric & eccentric contractions happen all the time but overall looks like isometric story How do we ”stack” up relative to gravity? Body's mass is equally distributed from front to back & side to side Theoretically requires least amount of muscular effort to maintain Neutral or “standard” posture? Muscles active in the sagittal plane Kendall, F. P., McCreary, E. K., & Provance, P. G. (1993). Muscles, Testing and Function: With Posture and Pain. Baltimore, Md: Williams & Wilkins. 1 Anatomic images have been modified from the 3D4 Medical app: Complete Anatomy 2022 2  #1 - FOOT Plumb - small weight tied to a cord that is hung from a ceiling plumb line Pull of gravity straight down gives Vertical Line of Reference 3 Calcaneal Cuboid Joint Estimates center of pressure of the foot 2 cm infront of lateral malleolus Just behind base of 5th metatarsal Moves back & forth Swaying feeling on a small scale  #2 - HEAD In neutral posture, the plumb line travels through External auditory meatus (EAM) - entry point to ear canal Approximate the centre of mass of the head EAM is deep to the Tragus - small flap to the ear 4 Axis of rotation for neck Gravity is trying to draw the head & neck down infront of the axis → flexion of the neck → cervical extensors are on COM of the head & line of gravity are infront In the lumbar region, line of gravity acts #3 - LUMBAR REGION right through the centers of vertebral bodies Gravity wants flexion, i.e, lumbar extensors are on Infront of lumbar spine joints 5 Gravity wants to tip the trunk & pelvis backward over At the hip, line of gravity is at level of greater trochanter the femur → extension of the hip → hip flexors are on Behind the axis at the hip joint Iliofemoral ligament (front of hip joint) is very strong Limits hip extension At the knee, line of gravity falls in front of center of knee joint #4 = KNEE Gravity wants to rotate the femur forward over the tibia around the axis of rotation → extension of knee → knee flexors are on People who rest in a passively hyperextended knee position Line of gravity is really infront of knee joint axis Use passive tissue tension from joint capsule & ligaments to fight knee extension 6  #5 - ANKLE At the ankle, plumb line falls anterior to talocrural joint Leg will rotate forward → gravity wants dorsiflexion of ankle → plantarflexors are on 7 The gravity-body relationship Leaving “neutral” behind Looking for surface anatomy clues 8