The Human Body
It is useful to have a working knowledge of how the human body works, how to describe parts of the body, and how the human body goes into motion.
Biomechanics is the science of human bodies in motion.
Here we are going to have a look at a selection of some of the information that is covered in the NZSIA E-Manual.
See the NZSIA E-Manual Section B – Skiing A Sport of Movement, Chapter – The Biomechanics of Skiing for more detail.
The Biomechanics of Skiing – Things To Know for Level 2
Proprioception
Developing the awareness of movement and the orientation in space of the body and its various parts, through internal sensors called proprioceptors. These are located primarily in the joints, muscles, tendons and the inner ear.
Types of Joints
Ball-and-socket joints – These joints have a wider range of movement than other joints, permitting movements in all planes, as well as rotational movement around a central axis. Ball and socket joints consist of a bone with a slightly egg-shaped head that articulates within the cup-shaped cavity of another bone. The hip and shoulder are ball-and-socket joints.
Gliding joints – These joints allow sliding or back-and-forth motion and twisting movements. The articulating surfaces are nearly flat or slightly curved. Most of the joints within the wrist and ankle, as well as those between adjacent vertebrae, are gliding joints.
Hinge joints – These joints flex and extend in a single plane. The convex surface of one bone fits into the concave surface of another. Such a joint resembles the hinge of a door in that it permits movement in one plane only. The elbow is a hinge joint, while the knee is a modified hinge joint as it glides and also allows a minimal amount of rotation.
Types Of Joint Movement
Flexion – bending body parts at a joint so that the angle between them decreases and the parts come closer together (bending the leg at the knee). Increasing angle with the frontal plane.
Extension – straightening body parts at a joint so that the angle between them increases and the parts move farther apart (straightening the leg at the knee). Decreasing angle with the frontal plane.
Abduction – moving a body part away from the midline (lifting the leg away from the body to form an angle with the side of the body). Moving away from the sagittal plane.
Adduction – moving a body part toward the midline (returning the leg from being away from the body to align with the body). Moving toward the sagittal plane.
Rotation – moving a body part around an axis of a bone, this movement occurs in the axial or rotational plane such as twisting the head from side to side, turning the femur in the hip socket. Medial or internal rotation involves movement toward the midline (inward), whereas lateral or external rotation involves movement in the opposite direction, away from the midline (outward).
Circumduction – moving a limb in a circular manner, this requires a combination of flexion, extension, abduction and adduction. The ball-and-socket joints of the hip and the shoulder are two of only a few joints that are capable of circumduction.
Ankle & Foot
Some of the ways the Ankle and foot can move.
The Knee Joint
The knee joint is a modified hinge joint and as the largest joint of the body it supports nearly all of the body’s weight. It connects the femur to the tibia and the patella (knee cap) and as a hinge joint the knee joint allows the leg to flex and extend.
The Hip Joint
The hip joint is a ball-and-socket joint made up of the side (socket) of the pelvis and the head (ball) of the femur. The femur moves at the hip joint in all three planes. Technically the femur rotates, abducts, adducts, flexes and extends at the hip joint.
The hip joint’s range of movement plays a vital role in skiing. It allows the legs to rotate and turn the skis (rotational movement). It allows the legs to flex and extend (fore/aft movement and pressure management). It also allows the legs to move sideways, relative to the pelvis, whether by moving the leg(s) out to the side or by moving the pelvis sideways, relative to the feet (lateral movement – edging).
Muscle Contraction
Skiing requires a blend of the following three types of muscular contraction, often simultaneously.
CONCENTRIC CONTRACTION – a type of muscle contraction in which the muscles actively flex (the fibres shorten) while generating force. Concentric contraction causes the muscle to shorten and change the angle of the joint. For example, when the hamstring muscles concentrically create tension to flex the knee.
ECCENTRIC CONTRACTION – the muscle elongates while under tension due to an opposing force being greater (such as gravity) than the force generated by the muscle. Rather than working to pull a joint in the direction of the muscle contraction, the muscle acts to decelerate the joint at the end of a movement, or otherwise control the repositioning of a load.
ISOMETRIC CONTRACTION – contraction of a muscle generates force without changing length. For example, the muscles of the hand and forearm grip the ski pole, and after the pole has been gripped the joints of the hand do not move but muscles generate sufficient force to prevent the pole from being dropped.
Connectors & Cushions
LIGAMENTS – important components of both structural and joint stability. For example, the anterior cruciate ligament (ACL) is a large ligament connecting the back of the femur to the front of tibia. When the hamstring stretches past an effective point, the ACL is one of the primary ligaments that serves to maintain knee joint stability.
TENDONS – are the tough fibrous cords that connect bone to muscle. When a muscle tenses, it applies force, pulling the tendon(s) connecting a muscle or muscle group to a bone. As force is transmitted through the tendon to the bone a joint flexes or extends. Tendons also have elastic qualities which help to manage forces acting on the body and aid in stability.
CARTILAGE – forms the slippery surface of the bone ends in the joints.
