Force Transfer & The Kinetic Chain
This video is a great tool for visualizing force transfer through the lower quarter and how it affects alignment in the frontal plane of motion.
If you start by looking at the foot and focus on only when the right leg first contacts the ground, we see a rapid succession of events as force is attenuated by the body.
1️⃣ The foot pronates almost immediately after initial contact in order to absorb shock and allow the foot to conform to the running surface.
2️⃣ A split second later, the knee collapses inwardly (dynamic valgus) due to adduction of the hip joint to a maximum of 10-13 degrees.
3️⃣ As force travels up to the hip and pelvis, the last notable characteristic we can identify is a contralateral pelvic drop (CPD). Watch the blue marker on the left side of her pelvis. After the knees moves inward, the blue marker on the pelvis drops as the hip abductors on the right leg (primary gluteus medius) work very hard to try and keep the pelvis close to level.
All of these movements are normal in most people as the body absorbs impact when running. However, poor strength and/or motor control can lead to increased movement in these areas and be associated with pain in various spots throughout the lower quarter. Common issues include shin splints, tendinopathy, patellofemoral pain syndrome, IT band syndrome, trochanteric bursitis and low back pain, to name a few.
If you are a runner and have pain or worker with runners in pain, an easy way to analyze your mechanics is with your phone camera and by placing colorful sticky dots on the areas seen in this video. You don't necessarily need fancy software to pick up biomechanical tendencies that may be associated with someone's pain.