For a better understanding of both movement and posture is helpful to understand basic anatomy. A simple break down of four body parts three joints (not including the spine) and two general directions for joint movement. Then the essence of sports biomechanics can be distilled to three simple rules.
The Spine naturally has a S shape and is made up of multiple joints. The spine has the ability to flex (rounding ones back like a cat) extend (leaning backwards into a bridge).
The pelvis is a large structure protects and holds the organs and connects the Spine to each Leg. The pelvis makes up the socket of the ball and socket joint of hips.
The femur is a large bone that makes up the top of the leg. The head of the femur is the Ball of the ball and socket joint that makes up the hip joint. The bottom of the femur is a hinge joint that connects to the the Tibia
The tibia is the lower part of the leg, below the Knee joint. The Knee joint is a hinge joint allowing flexion and extension.
The three joints to be aware of are the Knee Joint, The Hip Joint and the Sacroiliac Joint. We can then divide the body in half at the hips. The top we have the Trunk and below the legs. The basic movements about these joints are Trunk extension, Trunk flexion, Knee flexion and Hip flexion. Note the difference between Trunk flexion and Hip flexion. Through trunk flexion the spine and Sacroiliac joint flex making a rounded back position. Through hip flexion the Trunk remains rigid and braced all movement happens at the hip joint.
- Functional movement generally weds the spine to the pelvis. The SI joint and spine were designed for small range movement in multiple directions. Endeavour to keep the trunk tight and solid for running, jumping, squatting, throwing, cycling, etc. This produces greater performance across all functional movements
- The dynamics of those movements come from the hip—primarily extension. Powerful hip extension is certainly necessary and nearly sufficient for elite athletic capacity. Our major lifts Deadlift, Clean, Snatch and variants of all develop a powerful Hip extension.
- Do not let the pelvis chase the femur instead of the spine. We’ve referred to this in the past as “muted hip function” see post Power From The Hip here We also call it “frozen hip” because when the pelvis chases the femur the hip angle remains open and is consequently powerless to extend.
A demonstration of the three principles in action. Number 1 midline stabilisation of the spine and pelvis. Number 2 power from the Hips and Number 3 incorrect movement can have the load on the knees and power will be lost at the Hips.