Introduction Analyses of the athlete's movements are done according to specific planes of motion and their axes. In this module we discuss the essential anatomical terminology that describes joint and body movements, and muscular actions. A description of body segment movements begins with the anatomical reference posture. In this posture the body faces the observer, feet are apart, toes and palms are facing forward. What you will learn The directions, planes and axes around which motion occurs Special motions of joints Movements that are specific to the hands and feet Anatomical directions, planes and axes Directions indicate the relative position of one body part with respect to other body parts. Anterior posterior: Anterior refers to the front portion of the body. Posterior refers to the back portion of the body. Medial lateral: Medial is a direction closer to the midline of the body. Lateral is a direction away from the midline of the body. Superior inferior: The superior direction is upward toward the head. The inferior direction is downward, toward the feet. The shoulders are superior to the hips and the hips are inferior to the head. Proximal distal: Proximal is a direction closer to the beginning of a structure or toward the center of the body. Distal is near the end of a structure or away from the center of the body. The hand is distal to the shoulder. 1
Planes and axes. Every movement takes place in one of three planes of movement and around one of three axes. A Plane of motion is an imaginary two-dimensional surface through which a limb or body segment is moved. In the human body there are three planes of motion. The sagittal plane slices the body into left and right portions. The frontal plane slices the body into anterior and posterior portions. The transverse plane slices the body into superior and inferior portions. We will examine movements that occur in each of these planes when we discuss special movements of joints. Axes of rotation The vertical axis or longitudinal axis runs from the top to the bottom of your body. When a gymnast performs a three hundred and sixty degree turn, the rotation occurs around the vertical axis. It is the easiest rotation to do. An ice skater uses this rotation when going into a spin. The transverse axis runs from side to side of the body. A somersault is a rotation through the transverse axis. The antero-posterior axis, or the median axis, runs from the front to back of your body. It is the least commonly used axis. When a gymnast performs a cartwheel rotation occurs around the antero-posterior or median axis. Challenging the athlete to move in all these planes, and around all the axes produces optimal muscular development, balance, flexibility, coordination. 2
Special motions of joints Flexion-extension: These are the most common types of movement. Flexion is a bending movement that decreases the angle between the body parts. Extension is the opposite. It is a straightening movement. Flexion and extension usually occur in the sagittal plane. Examples of flexion include: Wrist snap in basketball free throw shooting Front dumbbell raise Barbell biceps curl Examples of extension include: Conventional dead-lift Long jump take off Military press If a part of the body such as a joint is overstretched or bent backwards because of an exaggerated extension motion, this is called hyperextension. This type of movement puts a significant amount of stress on the ligaments of joint. Hyperextension may occur due to accidents, falls, or other causes of trauma. Adduction-abduction: These are the next most common movements. Adduction is a joint movement toward the centerline of the body. Abduction is a joint movement away from the center line of the body. These two movements are in the frontal plane. Examples of adduction include: Cable crossover pulldown Supine dumbbell flys Hip adduction machine Examples of abduction include: Straight arm dumbbell side raise Star jump Cricket bowl 3
Internal external Rotation: Medial (internal) rotation of a joint turns a limb inward, toward the central axis of the body. Lateral (external) rotation of a joint turns a limb outward, away from the central axis of the body. The movement occurs in the transverse plane. When knees are turned towards each other in a standing position the hips and legs are rotating internally. External rotation is the opposite direction. When the knees turn away from each other in a standing position the hips and legs are being externally rotated. Joint Shoulder Hip Knee Internal rotation Movement of the humerus rotates medially in the transverse plane along its long axis toward the midline of the body Medial rotary movement of the femur in the transverse plane around its longitudinal axis and towards the midline. Rotary movement of the lower leg is medially toward the midline. Internal rotation is a very common movement in the human body occurring in three key joints the shoulder, hip and knee. When we walk or run our hips undergo internal rotation with every stride. The run up in javelin demonstrates internal rotation of the hip joint. The consequence of this internal hip rotation is a forceful rotation of the trunk, that in turn, transfers momentum to the upper body and arm. Internal rotation of the hip joint is an important factor in a successful javelin throw. External rotation also occurs in the shoulder, hip and knee joint. Joint Shoulder Hip Knee External rotation Movement of the humerus laterally in the transverse plane along its long axis away from the midline Lateral rotary movement of the femur is in the transverse plane around its longitudinal axis and away from the midline. Rotary movement of the lower leg is laterally away from the midline. 4
An example of external rotation is evident is during the tennis serve in the shoulder joint. This accomplished a couple of things. First, it stores elastic energy across the chest muscles that is used to generate force and momentum of the arm. External rotation also increases the time over which force can be applied during the forward phase. External shoulder rotation is used in all throwing motions for the same reason. Here is another example of external rotation in the volleyball spike. An example of external knee rotation occurs when sprinting the curve on a track at very high speed during a 200m and 400 m race. The right leg is loaded on every step around a turn forcing external rotation at the knee. Often both internal and external rotation can occur simultaneously. This is seen during a pivoting movement: The upper body and femur externally rotate during the start of pivoting. While the fore foot is sticking on the ground, the tibia internally rotates as a result. As you can imagine, this places considerable force on the knee ligaments. Circumduction is a cone-shaped movement of a limb that includes flexion, abduction, extension, and adduction. An example of circumduction is moving the arms in a windmill motion. Circumduction occurs when performing a serve in tennis or bowling a cricket ball. Valgus Varus: A valgus condition occurs when the knees are medial to the line from the hip to the heel, commonly called knock-kneed. A varus condition is when the knees are lateral to the line from hips to heel, commonly called bowlegged. Under normal conditions, the mechanical axis (red line) crosses the center of the knee joint (yellow dot). In the varus knee, the mechanical axis runs inside the joint center, while in the valgus knee it passes externally. 5
Examples When performing a squatting movement one instruction is to actively push the knees outward during the movement. This will help prevent valgus collapse, or inward caving of the knees. Another example is seen during a cutting maneuver in basketball. The female athlete appears to be susceptible to knee injuries when performing these cutting maneuvers. One explanation is that women perform cutting maneuver using a different technique from their male counterparts. Two different side step techniques are observed. Male athletes demonstrate VARUS moment where the knee is positioned over the 2nd toe. When the knee demonstrates a valgus moment, the ACL is at greater risk for injury. This is the typical technique used by the female athlete. You can imagine the strain placed on the knee joint when running with a valgus or varus condition. In this case here it is a valgus condition. Terms for movements of the feet and hands The hands and feet have a number of terms that are specific to each. Dorsiflexion and plantarflexion: Dorsiflexion is the bending of the foot upward, decreasing the angle of the dorsal aspect of the foot to the leg. Plantarflexion is the opposite. It extends the foot using the calf muscles. These actions are important in the walk and run foot movements. Inversion-Eversion. Eversion is the movement of the sole of the foot away from the center line of the body. Inversion is the opposite. It is movement of the sole of the foot toward the center line. Force inversion is a common cause of ankle sprains. Supination and pronation: Supination is the natural (that is without force applied) lateral displacement of the ankles beyond normal. Shoes will wear 6
on the outside edge, and runners may develop iliotibial band syndrome. A varus knee condition may also contribute to supination. In pronation, the ankles are displaced medially to normal. Shoes will wear on the inside edge. Pronation can also lead to ankle, knee and other joint pain. A valgus knee condition may also contribute to pronation. Supination and pronation of the forearm: Rotation of the forearm is often used to perform certain aspects of sport skills. The movement is described as either pronation or supination. This motion permits hitting a ball, throwing a ball and javelin among other skills involving the upper body. Pronation of the forearm is medial rotation of the forearm toward the center of the body. Supination of the forearm is lateral rotation of the forearm away from the center. Pronation and supination of the forearm are often done in coordination with shoulder rotation. Shoulder rotation is confined to the movement of the humerus. Pronation and supination occur at the elbow. Here you see what is happening in the bones themselves. This cartilage up here protects the bones during forearm rotation. We have not considered the muscles in any of the movements we have discussed, but you will ultimately need to know these so you can design the correct exercises for strengthening or stretching. One great exercise for strengthening exercise for the muscles of pronation and supination, and stimulating the cartilage of the bones of the shoulders, elbows and wrists is the Yoga Downward facing dog. How muscles move joints The muscles in the arm and thigh are among the largest and strongest skeletal muscles in the body. Many muscles work in pairs. One muscle of the pair contracts to bend the joint and the opposite muscle relaxes. To straighten knee, for example, the quadriceps femoris on the front of the thigh works with the biceps femoris, or hamstring in back of the thigh. The quadriceps contract and the hamstrings relax and the knee straightens. To bend the knee the hamstring contracts and the quadriceps relaxes. The biceps muscle on the front of the arm works with the triceps muscle on 7
the back of the arm in a similar fashion. When the biceps contracts the elbow bends and the forearm lifts. The triceps relaxes at the same time. To straighten the elbow and lower the forearm the triceps contracts and the biceps relaxes. 8