Biomechanics Activity Analysis

­Since I have been back home in East Tennessee in quarantine, I have taken over the job of feeding our horse and donkey (Pedro and Rufus) in the morning and evenings. The horses get a certain amount of grain at each feeding and the bag is on the floor. When I arrive at the bag of feed, I am facing the bag with my feet slightly apart, my left arm adducted at my side, and my right elbow is flexed at a 90 degree angle holding the food container. Since the horse feed is on the ground, I will then slightly flex at the hip to bend over and flex my knees to get closer to the ground. The plane of motion involved for both movements is in the sagittal plane within a frontal axis. I will then reach forward to scoop up the feed, which involves shoulder flexion, which is also done in the sagittal plane within a frontal axis.

I am going to focus on the movements at my knee joint for this activity analysis, since I cannot reach the feed without flexion at the knee joint. The arthrokinematics of knee flexion involves the convex/concave rule which is the convex segment (femur) is the moving surface and rolls posteriorly and glides anteriorly on the tibia, which is the concave segment and the stable surface.

During flexion, the quadriceps muscles are eccentrically activating (lengthening) while the hamstring muscles are concentrically contracting (shortening). But, I have to hold my flexed position to scoop the feed into the container, so during the time I am filling the feed container, my muscles are isometrically contracting. Once I have filled the container I will then need to extend my knees, which will involve the hamstrings to eccentrically activate and the quadriceps to concentrically contract. The osteokinematics involved during this include flexion and extension. I will then end my position fully upright with my feet apart, my left arm adducted at my side, and my right elbow flexed at a 90 degree angle. I will then head down to the barn and feed those two little stinkers, all while Rufus is hee-hawing loud enough to wake up the whole town!