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Section A Chapter 1 Worksheet Fibre types in action – Teacher’s copy (see student textbook, pages 17–20) The diagram below shows a picture of a trampolinist during a routine. 1 Name the type of joint and identify the bones that articulate at the hip joint. Type of joint: ball-and-socket Articulating bones: pelvis and femur 2 During the routine the trampolinist performs a tuck jump. State the movement pattern that occurs at the hip and the muscles responsible during this skill Movement pattern: flexion Muscles responsible: iliopsoas (hip flexors) 3 The muscles of a trampolinist will contain a high percentage of fast-twitch muscle fibres. Using your knowledge of the structure and function of fast-twitch muscle fibres, explain why this is so: A trampolining routine is very explosive and only lasts a minute or so. Muscle fibres responsible for explosive activities are fast-twitch fibres. In this instance, I think that the trampolinist will have a high proportion of Fast-Oxidative Glycolytic (FOG or Type 2a) fibres. The functional characteristics of which are that they have a high speed and force of contraction as well as having a high anaerobic capacity, yet are able to withstand fatigue for a short while. It is due to the structure of the muscle fibres that these functions exist. The thick structure of the muscle fibre means that it contains high levels of ATP, PC and glycogen, which allow lots of energy to be produced quickly and have moderate levels of mitochondria and myoglobin, which help the FOG fibres to withstand fatigue. 4 State each of Newton’s three Laws of Motion and apply each to the trampolining routine. Newton’s First Law of Motion is the Law of Inertia. This states that ‘a body at rest or moving in a straight line with constant velocity will continue to do so unless acted upon by an external force’. The trampolinist will therefore remain stationary on the bed until his muscles contract producing a force to overcome his inertia. Newton’s Second Law of Motion is the Law of Acceleration and this states that ‘the rate of change of momentum of a body is proportional to the force causing it and takes place in the direction in which the force acts’. The greater the (reaction) force (of the bed), the greater OCR PE for AS © Hodder Education 2008 Dynamic Learning Network Edition CD-ROM Section A Chapter 1 Worksheet Fibre types in action – Teacher’s copy the acceleration of the trampolinist. As the reaction force is upwards the trampolinist will accelerate in an upwards direction. Newton’s Third Law of Motion states that ‘for every action there is an equal and opposite reaction’. With reference to the trampolinist, this means that as the trampolinist lands on the bed he produces a downwards ‘action’ force; in response, the trampoline bed produces an equal and opposite force back onto the trampolinist, propelling the trampolinist into the air. 5 Using examples from the routine, state the different types of motion used when trampolining. Explain how these types of motion are initiated. There are three different types of motion: • Linear motion: this is movement of a body or object that takes place in a straight line. For example, when moving directly upwards or downwards on the trampoline in a straight line • Angular motion: this is when all parts of a body or object move in a circle or part circle about a fixed axis of rotation. For example, when performing a tucked-back somersault • General motion: a combination of angular and linear motion. For example, when performing a tuck jump, the body is moving in a linear fashion upwards, but angular motion occurs at the hip to cause flexion. 6 Study the information given in the table below. Using the information in the table and reference to a range of sporting activities, suggest how the structure of each fibre type suits its particular function. The structure of Slow-Twitch fibres are suited to their function because they contain high levels of mitochondria, myoglobin and triglycerides, which all help to produce energy aerobically and offer great resistance to fatigue. They also have a high capillary density, enabling greater amounts of oxygen to reach the muscle and allow waste products such as lactic acid to be removed more quickly. A marathon runner or triathlete will undoubtedly possess a very high proportion of Slow-Twitch muscle fibres. The structure of Fast-Twitch Glycolytic fibres are suited to their function because they contain high levels PC, ATP and Glycogen stores and low levels of mitochondria, myoglobin and triglyceride stores. This means that they are used for very explosive activities that are anaerobic in nature, such as shot putt or a 100 m sprint. These fibres are very thick and therefore have a very high speed and force of contraction but fatigue really quickly. The structure of Fast Oxidative Glycolytic fibres are suited to their function because the thick structure of the muscle fibre means that it contains high levels of ATP, PC and glycogen, which allows lots of energy to be produced quickly and to moderate levels of mitochondria and myoglobin, which help the FOG fibres to withstand fatigue. They have greater anaerobic capacity but have some aerobic capacity so they will be useful in athletic events such as the 1500 m or swimming a competitive 100 or 200 m race. L OCR PE for AS © Hodder Education 2008 Dynamic Learning Network Edition CD-ROM Section A Chapter 1 Worksheet Fibre types in action – Teacher’s copy Slow-Twitch (Type 1) Fast-Oxidative Glycolytic (FOG) (Type 2a) Fast-Twitch Glycolytic (FTG) (Type 2b) Speed of contraction (ms) Slow (110) Fast (50) Fast (50) Force of contraction Low High Highest Resistance to fatigue Very high Moderate Low Aerobic capacity Very high Moderate Low Anaerobic capacity Low High High Fibre size Small Large Large Mitochondrial density High Moderate Low Capillary density High Moderate Low Myoglobin content High Moderate Low PC store Low High High Glycogen store Low High High Triglyceride store High Moderate Low Motor neuron size Small Large Large Activity suited Marathon 1500 m Shot putt Functional Characteristic Structural Characteristic OCR PE for AS © Hodder Education 2008 Dynamic Learning Network Edition CD-ROM