The right knee is in a state of flexion and the right ankle is in plantarflexion, this is because the gastrocnemius and soleus are contracting concentrically whilst the tibialis anterior, tibialis posterior and the extensor digitorum longus are contracting eccentrically. This causes the ankle to be up on the toes of the foot and the muscles that make the knee flex are the biceps femoris, gracilis, semitendinosus and semimembranosus are all contracting concentrically while the vastus lateralis, rectus femoris and vastus medialis are contracting eccentrically. The reason the right leg is flexing is so that the most potential force can be exerted from it, therefore creating more power and a further throw due to an increased follow through with the legs.
The left knee is in a state of extension and the left ankle is in dorsi-flexion, this is where the ankle is on the heel of the foot. It is in dorsi-flexion because the gastrocnemius and soleus are contracting eccentrically whilst the tibialis anterior, tibialis posterior and the extensor digitorum longus are contracting concentrically. The left knee uses the top of the leg muscles to get in this position, the biceps femoris, gracilis, semitendinosus and semimembranosus are all contracting eccentrically while the vastus lateralis, rectus femoris and vastus medialis are contracting concentrically. The reason for the left leg extending is to get in a position where the next movement will be able to produce the most angular force; the leg will also act as a balance to support the body and to control the throw of the javelin.
Below is a picture of a cyclist, I am about to discuss the muscle actions, action at the joints, action of the limb segments and the muscle contractile velocity and force.
Class Notes
The right and left shoulder of the cyclist are in a horizontal adduction, this is because the pectoralis major is contracting concentrically and the deltoids are contracting eccentrically. The right and left elbow are both flexing by using the biceps to contract eccentrically and the triceps to contract eccentrically, the wrists are both pronated because the flexors are contracting concentrically and the extensors are contracting eccentrically to grip the handle bars. The reason for the right and left arm being in this position is so that the body becomes smaller creating a better air flow so that the cyclist is able to travel at greater speeds.
The hips are also in a horizontal adduction because the lower abdominals are contracting concentrically whilst the gluteus maximus, gluteus medius and the external obliques are all contracting eccentrically. This is because the body needs to reduce the amount of air flow over the body so by sitting as low as possible will reduce this although the back or the spine takes a major role in the reduction of airflow. The spine on the cyclist is arched towards the air so is flexing at the top of the back and extending at the lower back, the muscles that make this happen are the erector spinae which is contracting eccentrically as well as the latissimus dorsi which also contract eccentrically. This causes the external obliques to contract eccentrically and the rectus abdominis to contract concentrically. The reason for the back arching over is to get as low as possible to make the body smaller to reduce the air flow.
The left knee is in a state of flexion because the biceps femoris, gracilis, semitendinosus and semimembranosus are all contracting concentrically while the vastus lateralis, rectus femoris and vastus medialis are contracting eccentrically. The left ankle is in plantarflexion, this is because the gastrocnemius and soleus are contracting concentrically whilst the tibialis anterior, tibialis posterior and the extensor digitorum longus are contracting eccentrically. The reason for the leg being in this position is so that more angular force can be applied when he puts pressure on the pedal creating the bike to travel at faster speeds.
The right knee is in the state of extension because the biceps femoris, gracilis, semitendinosus and semimembranosus are all contracting eccentrically while the vastus lateralis, rectus femoris and vastus medialis are contracting concentrically. The right ankle is in plantarflexion, this is because the gastrocnemius and soleus are contracting concentrically whilst the tibialis anterior, tibialis posterior and the extensor digitorum longus are contracting eccentrically. This is because the right leg has jus been in the state of flexion and is following through although the ankle remains on its toes as the cyclists uses them to lift the pedal back around to create even more force creating even more speed.
Task 2 –
Below is a diagram of the knee joint, also known as a hinge joint.
Class Notes
The joint at the knee is called a hinge joint; it is only able to move in one plane which is flexion and extension. There are strong ligaments to prevent sideways movement. These ligaments are known as the cruciate ligaments in between the tibia and the femur, the lateral ligament and the medial collateral ligament. They prevent the knee from moving sideways which restricts the range of movement. The leg is able to flex till it hits the femur as it will not be able to pass through it restricting its range of movement also. When the leg extends is may be able to go just above 180 degrees which is known as hyper extension although this is not generally the case, it is restricted due to the knee itself. The total range of movement depends on the flexibility of the quadriceps and the hamstrings. For example a footballer kicking a ball will contract the hamstrings so a professional footballer will train the hamstrings to get more flexibility to get a more powerful shot.
Below is a diagram of the shoulder, this I known as a ball and socket joint.
The joint at the shoulder or the ball and socket joint allows the widest range of movement, this is where a rounded head fits into a cup shaped cavity. This allows the shoulder to abduct, adduct, flex, extend, media/lateral rotation and circumduction, the range of movement at the shoulder is far greater than that of the knee. If the pectoralis major and deltoids are more flexible then the range of movement will be greater, although the shoulder is unable to put the arm all the way around the body as the body will get in the way, or it cannot get straight around over the head because the capsular ligament will stop this affecting its range of movement. For example if you are a gymnast then the amount of flexibility will be far greater than that of an average person because you train to make the joints flexible as you can.
Below is a diagram of the wrist which is also known as an ellipsoid joint.
Class Notes
At the wrist or an ellipsoid joint it is a biaxial, which allows movement in two planes; this means it allows flexion, extension, abduction and adduction. The range of movement in this joint lets you think you are rotating the wrist although it is impossible to do this because the radius, ulna and certain ligaments prevent it. This reduces the range of movement, although if the joint has been well exercised, for example you are a table tennis player then you will gain more flexibility through your wrist as the muscles and ligaments are being used regularly.
Task 3 –
When the body is being described in certain regions, postions relative to the anatomical postion are used, The anatomical position is a person standing upright, facing forwards with their arms postioned downwards and the palms of the hands facing forwards. There are several common terms used to describe parts of the body. These include:-
- Superior – a structure higher or closer to the head than another
- Inferior – A structure lower or closer to the foot than another
- Medial – Towards the midline of the body
- Lateral – Away from the midline of the body
- Anterior/ventral – Towards the front of the body
- Posterior/dorsal – Towards the back of the body
- Superficial – Towards the surface of the body
- Deep – Internal of below the surface of the body
- Proximal – A structure or body part closer to the point of attatchment than another
- Distal – A structure or body part further away from the point of attachment than another
- Left – Towards the left side of the body
- Right – Towards the right side of the body
Below is a diagram of an anatomical position.
The midline of the body goes straight through the centre of the body; it is the middle of the body dividing it into left and right proportionally.
The planes and axes of the body is a way to describe the body’s movements, it is imagining the body has a series of lines running through it. These lines are known as the planes of movement, the lines divide the body into three ways. The median or saggital plane splits the body vertically into the left and right sides. The horizontal or transverse plane splits the body into superior and inferior sections running horizontally down the midline of the body, so the coronal or frontal plane runs vertically and divides the body into anterior and posterior sections. An example of using the horizontal plane would be a tennis shot when you swing for the ball because you are rotating the hips. With the saggital plane you are going forwards so jogging or sprinting will be an example of this, and for the frontal plane an example would be side stepping in a football match to get back into position. You can see this in the diagram below.
The body also has three axis, the anterior-posterior axis is in the centre of the body at the front, for example we use this axis when completing a cartwheel in gymnastics. We also have a horizontal axis, this is transverse or on the side of the body in the middle of the planes, an example of this could be a forwards somersault in gymnastics. The final axis is known as the longitudinal axis which is at the top of the body in the middle of the planes, in trampolining when completing a full twist will be an example of this axis.
A way to test the flexibility of a limb is by using a goniometer, it is a piece of equipment specifically designed to measure the range of movement at a join. The head of the goniometer is placed at the axis of rotation of a joint while the arms are aligned longitudinally with the bone. A measurement in degrees can be taken which gives a reading that can be asses to improvement. The disadvantage of this equipment is that it is not always easy to identify the axis of rotation of a joint.
Task 4 –
The classification of levers –
Levers are what make efficient and effective movement possible, they are mechanical devices used to produce turning motions about a fixed point, and this is known as a fulcrum. In the body the bones act as levers and joints act as fulcrum, a fulcrum is the point about which a lever rotates. Muscle contractions provide the force to move the lever about the fulcrum. A basic understanding of lever systems can be used to explain rotational motion, as well as helping athletes develop the most efficient technique for their sport.
There are three types of levers, each lever is determined by its relationship of the fulcrum, the point of application of force or effort and the resistance of load.
A first class lever is where the fulcrum lies between the effort and the resistive force as shown below.
An example of this is a seated dumbbell tricep extension in strength training
A second class lever is where the resistance lies between the fulcrum and the effort as shown below.
An example of this could be a standing heel lift
A third class lever is when the effort is between the fulcrum and the load as shown below.
An example of this could be a seated bicep curl in strength training
There maybe more than one lever system operating at a joint, for example when flexing the elbow as in a bicep curl, the effort comes from the point of insertion of the biceps brachii on the radius. This movement involves a 3rd class lever. Although when extending the elbow such as throwing a javelin, the effort is generated by the triceps brachii via its point of insertion on the ulna, this movement involves a 1st class lever.
Levers have two main functions which are to increase the resistance that a given effort can move and to increase the speed at which the body moves. First class levers can increase both the effects of the effort and the speed of the body; second class levers can only increase the effect of the effort force and third class levers can be used to increase the speed of a body. A good example of a third class lever in the body is the action of the hamstrings and quadriceps on the knee joint which causes flexion and extension of the lower leg. The extent to which this can increase, depends on the relative lengths of the resistance arm and the effort arm.
The resistance arm is the part of the lever between the fulcrum and the resistance; the longer the resistance arm the greater speed can be achieved.
The effort arm is the distance between the fulcrum and the effort, the longer the effort arm, the less effort required to move a given resistance. For example a tennis racket is used to increase the length of the effort arm which will increase the force that the tennis ball is struck. Although the optimal length of an implement should be determined by the strength or the person handling it, this is why junior tennis rackets are designed so they are able to control the racket.
The relative efficiency of the lever system is expressed as the mechanical advantage which is shown as follow:-
MA = Effort arm
Resistance Arm
We use levers in every sport, for example when we kick a ball in football we will use the leg as a lever, so the longer the leg the further the ball can be kicked. Or when you are in boxing the longer someone’s are the harder they are able to punch is this is their main lever.
Moments….
Bibliography –
Wesson, K., Wiggins, N., Thompson, G., Hartigan, S. (2001) Sport & PE a complete guide to Advanced level study. Hodder & Stroughton
Stafford-Brown, J. Rea, S. Chance, J. (2003) BTEC National in Sport & Exercise Science. Hodder & Stroughton
Honeybourne, J. Hill., Moors, H. (2000) Advanced Physical Education and Sport for Advanced Level. Nelson Thorne
SEEVIC College VLE