Factors Affecting Performance HSC Core 2 Focus Question: How does training affect performance?
Energy can be defined as the capacity or power to do work, such as the capacity to move an object (of a given mass) by the application of force. Energy can exist in a variety of forms, such as electrical, mechanical, chemical, thermal, or nuclear, and can be transformed from one form to another. It is measured by the amount of work done, usually in joules or watts. For the purposes of human movement we are mainly concerned with the transfer of chemical energy into mechanical energy. In this process, the breaking of chemical bonds in molecules releases energy for use by the body. The body does not directly use the energy that is released in the breakdown of food; rather this energy is used to make a chemical compound called adenosine triphosphate. (ATP). The three macro nutrients, carbohydrate, fats and protein, all work in different ways to assist with the production of ATP and provide differing amounts of energy per gram. ATP releases energy when it splits to form adenosine diphosphate (ADP) plus a phosphate ion (P). ATP is found within the cells of the body and is an energy-rich chemical compound. However, only a small amount is stored in the muscles, only supplying a few seconds worth of intense activity. Therefore the body must be able to replenish stores in a process known as resynthesis. Energy systems • ADP • P • Energy • ATP (From breakdown of foods) (For Activity) (For Activity)
This involves rebuilding ATP from ADP using one of the three energy systems. The intensity (the effort needed) and duration (period of time) of the activity determines the way in which ATP is resynthesised. The human body requires a continuous supply of energy both to meet the metabolic needs and to power muscular contraction for movement. There are three energy systems which provide the working muscles with energy for movement. These include: the two energy systems which operate without the presence of oxygen - the alactacid (ATP/PC) system and the lactic acid system the energy system that operates with oxygen - the aerobic system The predominance of any system or systems during activity is dependent on the duration and intensity of the activity.
Energy Systems Alactacid system Source of fuel - ATP supplies in the body are very limited and there is often only enough energy to supply an explosive contraction such as a sprint start. The alactacid system is used by the body to produce ATP when there is insufficient time to break down glycogen in the presence of oxygen for the replenishment of ATP. At the same time that ATP is being broken down in the muscle, another high-energy substance which is stored in our cells – phosphocreatine (PC) – is also being broken down. (For resynthesising ADT to ATP)
Energy Systems Efficiency of ATP production - This system is very efficient as chemical reactions occur very quickly and are very simple. The breakdown of PC produces energy, which is used to join ADP and P back together to produce ATP, making this system very efficient in producing energy. Duration of the system - The amount of PC in muscles is limited. After about 5-10 seconds of maximal work supply is depleted. This reduces its ability to contribute to movement and therefore another energy system is activated. High intensity activity lasting for 10 seconds or less uses the ATP-PC system as the primary source of energy. Explosive activities such as 100m sprint, kicking a football, and athletic field events are examples of skills/activities that are primarily fueled by the ATP/PC system. Cause of fatigue - Fatigue is caused by the inability of the system to continually resynthesise ATP as PC stores are exhausted and need time to recover. By-products of energy production - There are no by-products of this system that will cause the body to fatigue however heat is produced during the process of muscular contraction. Rate of recovery - As the stores of PC are broken down, they are quickly restored. If the individual is resting most of the ATP and PC supplies are restored within 2 minutes. This allows for the activity to be repeated in intense, short bouts, without immediate exhaustion, for example field athletics athletes. The only way PC can be restored is to recombine the P and C release to resynthesise ATP. This is done during recovery. This system represents the most readily available source of ATP for use by the muscles.
Energy Systems Lactic acid system Source of fuel - The other system that does not require the presence of oxygen to resynthesise ATP in muscles is the lactic acid system, which is also known as anaerobic glycolysis. Following the initial 10 -12 seconds of maximal exercise, PC stores are exhausted and ATP still needs to be produced to provide energy. The body needs to find an alternate fuel and the lactic acid system becomes the dominant supplier of ATP. This system involves the partial breakdown of glucose to form lactic acid in a number of chemical reactions know as glycolysis. The glucose for this process comes from either glucose stored in the blood or from the breakdown of glycogen in the liver or muscle. (For resynthesising ADT to ATP)
Energy Systems Efficiency of ATP production - The production of energy during this process is very efficient as there is a relatively quick supply of ATP; however it requires large amounts of glucose. Unfortunately, however, this process can yield only 5 per cent of the number of ATPs that are produced by the aerobic system, yet more than the ATP/PC system. Duration of the system - The lactic acid system is an important energy system because it provides a very quick supply of ATP for intense, short bursts of activity (usually 30-60 seconds, but may last up to 3 minutes). The duration of the system depends upon the intensity of the activity, therefore the less intense the activity, the longer it will last. Cause of fatigue - Fatigue and exhaustion occurs when lactic acid accumulates in the muscle cells. This will usually cause the athlete to decrease the intensity of the activity, or to stop altogether. The speed of lactic acid production depends again on the exercise intensity. Very high levels of lactic acid prevent muscles fibres from contracting and hence a deterioration in performance. By-products of energy production - Pyruvic acid/lactic acid is the main by-product of the lactic acid system. Rate of recovery - Post-exercise lactic acid diffuses from the muscle and into the bloodstream. It is then reconverted to glycogen in the liver and once again can be used as a source of fuel. To break down and remove lactic acid may take 30 minutes or up to 2 hours. An active recovery will aid this process.
Energy Systems Aerobic system Source of fuel - The aerobic energy system is the most complex of the three energy systems. It is the primary source of ATP at rest and during low-intensity exercise. Carbohydrates, fats and proteins are used as fuel sources. At rest, fats and carbohydrates are used as sources of fuel. Energy release from fats is very slow, as it must be converted from triglycerides into glycerol and free fatty acids. Although 1 gram of fat produces more energy than carbohydrates (9 kilocalories from fat, versus 4 kilocalories from carbohydrates), it requires more oxygen. Consequently, as exercise intensity increases there is a greater reliance on ATP production from glucose (energy is released much quicker) and less on fats. Aerobic glycolysis (or slow glycolysis) is used to produce this ATP. This process involves the partial breakdown of glycogen or glucose in the presence of oxygen to produce ATP, with pyruvate as the end product. The longer the duration of continuous exercise—more than 1 hour of continuous exercise, or more than 3 hours of intermittent exercise—the more important fat will be as a fuel source, as glycogen stores become depleted.
Energy Systems Efficiency of ATP production - The aerobic system is extremely efficient in metabolising fuel and providing energy. It produces large, almost unlimited amounts of ATP however chemical reactions are slow due to the necessity of oxygen to be present and the intricate chemical pathways involved. Compared to glucose, fats can supply up to 10 times as many ATP molecules. Duration of the system - Glycogen stores in the body are usually sufficient for 12 hours of rest or one hour of intense exercise. During intermittent activities, such as netball or touch, glycogen supplies can last for a number of hours. Fat supplies in the body are virtually unlimited and this is then used when glycogen stores are depleted. In well trained athletes, they can train their bodies to use fat earlier so that glycogen is available at a later stage, for example for a sprint finish in a long distance run. To maintain its everyday bodily functions the body predominantly uses the aerobic system. Cause of fatigue - Depletion of fuel sources, particularly glucose, causes fatigue. However the aerobic system is versatile in fuel usage so it is able to switch to another source if one runs out. Poor respiration and/or circulation, whereby oxygen is unable to be utilised efficiently by the muscles as well as subsequent poor removal of waste products such as carbon dioxide, may also cause fatigue in athletes. It has been recognised that the moment the body switches from using glycogen to fat as a fuel can cause a momentary feeling of fatigue, often termed ‘hitting the wall’. This is due to fat requiring more oxygen for metabolism than glycogen which can in turn increase an athlete’s respiration rate and body temperature.
Energy Systems By-products of energy production - As with most fuels that are burnt, by-products are produced, in this case, carbon dioxide and water. Carbon dioxide is breathed out during the process of respiration and the water is available to the cells or is lost through sweat or expiration. Lactic acid does not accumulate during aerobic metabolism because oxygen is present. Rate of recovery - The recovery rate of the aerobic system depends on the type of activity that has taken place. If used for a short period of time, where glycogen stores have not been depleted, the system recovers quickly. However, if used for hours, glycogen stores could be well exhausted and it may take days to fully restore glycogen reserves. An important factor to consider in regards to the recovery of the aerobic system is to replenish lost glucose and glycogen. The energy systems should not be thought of as working independently of one another, but more so where one system is used predominantly at any given point, depending on the duration and intensity of the activity. For example, netball centre players use the aerobic system to provide constant energy required to continually move back and forth on the court – usually at moderate levels of intensity. Occasionally, they may need to sprint down the court to assist in attack or defence or jump to intercept a ball. These movements usually last a few seconds, and use the anaerobic energy systems. In most sporting situations, energy systems are used in various combinations. Middle to long distance track athletes should be able to pace themselves to ensure that their ATP supplies are not depleted too early in the race. If they push too hard, or begin the final sprint too soon, lactic acid will accumulate to high levels and decrease their performance.
Energy Systems in Practice Although the systems have been referred to individually, they actually function together. This gives rise to the term predominant energy system, or the system that is being most utilised at that point in time. During exercise an athlete will move through the various energy pathways. As exercise begins, ATP is produced through anaerobic metabolism from both the ATP/PC system and the lactic acid system. With an increase in breathing and heart rate, there is more oxygen available and aerobic metabolism begins and continues to resynthesise ATP molecules over an extended period of time. energy systems
For athletes to be prepared to perform they need to train. Coaches and athletes need to understand that there are various types of training that are specifically designed to develop aerobic capacity, strength and flexibility, and that each is closely linked to the energy systems and principles of training. The most common types of training are: Aerobic (continuous, fartlek, aerobic, interval & circuit) Anaerobic (anaerobic interval) Flexibility (Static, ballistic, PNF, dynamic) Strength training (free weights, fixed weights, elastic, hydraulic). Types of training and training methods
Aerobic Aerobic training involves training the larger muscle groups (e.g. legs) to efficiently combine with the cardiorespiratory system to supply a higher volume of oxygen to the working muscles and therefore improve performance. Aerobic training develops the capacity of the aerobic energy system and aims to: increase cardio respiratory efficiency (the ability of the body to deliver and utilise oxygen) reduce coronary heart disease and improve general health assist in weight control. There are four common methods to improve aerobic capacity; Continuous Fartlek Aerobic interval Circuit training One method of training will not meet the training needs of any given sport and therefore it is important to use a variety of methods to effectively train for the specific activity as well as provide variety in training. Types of training and training methods
Types of training and training methods Aerobic, eg Continuous, fartlek, aerobic, interval, circuit Continuous Training: The most common form of aerobic training is called continuous training. In this form of training, the heart rate is elevated and maintained by using jogging, power walking, cycling, swimming, aerobic floor classes, or any other form of exercise that elevates the heart rate. It should be performed continuously for a minimum of 20 minutes. Continuous training is generally of a long duration and moderate intensity: 70-85 per cent of maximum heart rate for 30 mins to 2 hrs. Although continuous training is effective in producing a training effect, it might not necessarily replicate the performance requirements. In other words, it might not be specific enough for the requirements of some sports or positions, or it might be too difficult to train at the same level as the competition requires. Consequently, other forms of aerobic endurance training have been developed
Types of training and training methods Interval Training: Interval training involves the breakdown of the training period into intervals of exercise or work, followed by periods of rest or relief. Two basic rationales underpin interval training. These are that such training: • Is better for adapting the nervous system to the movement patterns experienced in competition. • Allows the athlete to exercise for a longer period of time at high intensity, thereby aiding adaptations in the aerobic metabolic systems in the muscle The major variables that are manipulated in interval training are: • Time • Type These can be adjusted to provide improvements in both aerobic and anaerobic training.
Aerobic interval training involves alternating periods of exercise or work, followed by periods of rest or relief. Interval training involves moderate duration (time) and moderate to high intensity training, for example, 80-90 per cent of maximum heart rate (MHR) for 30-60 minutes in intervals of 4-10 minutes. The rest period between each repetition is short in relation to the work period, approximately 1-2 minutes. This does not allow for full recovery and thus maintains stress on the aerobic system. These can be adjusted to provide improvements in both aerobic and anaerobic training and can be designed to match the athlete’s sport and conditioning levels. Time - The duration of the intervals should be long enough to allow athletes to reach their maximal oxygen uptake (max VO2), but be short enough not to bring on fatigue. Type - The intensity should allow athletes to reach their max VO2, but the rest intervals should usually be active, such as walking or jogging slowly. This aids in removing accumulated lactic acid and therefore allows athletes to train longer. Types of training and training methods
Types of training and training methods Fartlek Training: Fartlek training is the Swedish name for Speed Play. Speed Play is a combination of continuous training and interval training in that it involves continuous effort with periods of high intensity, followed by a recovery period. Generally speaking, the bursts of speed are usually of 5-10 seconds duration, and are repeated every 2-3 minutes. Speed Play is usually performed over undulating terrain (such as up and down hills) and is less formalised than interval training. The degree of aerobic versus anaerobic work is dependant on the athletes, and how they feel during the workout. The predominant improvement is seen in aerobic capacity. Speed Play can be easily adjusted to meet the needs of most athletes, and the needs of both interval and continuous systems.”.
An example of a Fartlek training session is: Jog for 10 minutes to warm up, then stretch Run for 800-1500 metres at a fast, steady speed. Walk rapidly for 3 minutes Run continuously for 2000 metres, interpersing with a 50 metre sprint every 300 metres Run three lots of 400 metres at a fast pace, with a 400 metre jog between each fast run Run slowly for 2 minutes Cool down and stretch Types of training and training methods
Types of training and training methods Circuit Training: Circuit training is an arrangement of exercises that requires the athlete to spend some time completing each exercise before moving on. It is an excellent way to improve mobility and at the same time, build strength and stamina. Depending on the equipment available, circuits can be developed to improve general fitness or can be highly specialised to meet the specific needs of certain athletes. Circuit training usually consists of 6-10 strength type exercises that are completed one after the other. Body parts are also alternated so that consecutive exercises don’t work the same muscle groups
BASIC CIRCUIT Types of training and training methods
Types of training and training methods Anaerobic Anaerobic training involves high intensity activities, mostly in excess of 85 percent of maximum heart rate (max HR), with limited recovery to develop the two anaerobic energy pathways. One of the most effective ways to train the anaerobic system is to use interval training, which is often referred to as sprint training over short distances using maximal effort. This has some similarities to aerobic interval training; however anaerobic intervals tend to use higher intensity with longer rest breaks. Anaerobic intervals are characterised by brief, maximal activity, generally ranging between 10 seconds and 2 minutes, with a work rest ratio of 1:3, meaning for every 10 seconds you work you rest for 30 seconds. The rest component, also known as the relief interval, may involve sitting or stretching or gentle work such as walking or slow jogging.The intervals are performed in sets of repetitions that are designed to overload the anaerobic energy systems. Maximal effort repetitions (lasting 10 seconds or less) are designed to improve the ATP-PC stores, whereas slightly longer efforts (up to 2 minutes) aim to improve the body’s tolerance to lactic acid to be removed from the body between repetitions and sets. Most anaerobic interval training is directed towards the development of speed as might be required for short bursts in games such as touch football.
Flexibility refers to the range of motion of a joint or group of joints. There are a number of ways in which flexibility can be utlised, including static stretching, proprioceptive neuromuscular facilitation (PNF), dynamic stretching and ballistic stretching – the first two involve passive stretching and the last two involve movement. The degree of flexibility of motion varies among people and depends on the structural characteristics of their joint and its connective tissue. Flexibility decreases with age primarily due to loss of elasticity and joint mobility. Generally, females are more flexible than males. A flexible person will have improved neuromuscular pathways, which will minimise injuries. Temperature also influences flexibility, as an increased range of motion is available in warmer temperatures. To understand flexibility you need to understand the mechanics involved in stretching. When a muscle is stretched, receptors within the muscle, known as muscle spindles are stimulated. They record the change in length and send a signal to the spine, which then sends a message to the brain that the muscle is being extended. If the muscle is overstretched or stretched too fast, the spinal cord sends a reflex message to the muscle to contract. This is a basic protective mechanism, referred to as the stretch reflex, to help prevent over stretching and injury. Types of training and training methods
Types of training and training methods Flexibiltyeg Static, PNF, Dynamic ,Ballistic Static stretching This is a form of passive stretching and consists of stretching a muscle to its farthest point or limit and then maintaining or holding that position for a period of 15-30 seconds. This is the most commonly used flexibility technique and is very safe and effective, because it is done in a controlled slow manner and because it overcomes the stretch-reflex mechanism and allows the muscle to be stretched to its fullest possible length. Static stretching is used extensively with athletes recovering from injury to ensure that the muscle fibres are being aligned properly in the rehabilitation phase. This stretch should be performed without discomfort of pain
Types of training and training methods PNF Stretching: This has emerged from the field of rehabilitation, and is one of the most effective forms of stretching. The PNF (proprioceptive neuromuscular facilitation) method is a combined technique of static stretching and isometric stretching and works with the muscle spindle to get used to the new length of the muscle. PNF stretching involves: • A muscle group is statically stretched • An isometric contraction against resistance while in the stretched position that is held for 6 seconds • A relax • Then statically stretched again through the resulting increased range of motion, which may be assisted. PNF stretching usually requires the use of a partner to provide resistance against the isometric contraction; the static stretch will help the muscle spindle get used to the new length of the muscle after it has been isometrically stretched.
Types of training and training methods Dynamic stretching Dynamic stretching is also called ‘active’ or ‘range-of-motion’ (ROM) stretching. It stretches muscle groups that cross over joints. Dynamic stretching involves the gentle repetition of the types of movements that will be experienced in a performance. It is usually very specific to the performance. Such stretching is commonly carried out in an exercise class to music. First the body is warmed up using rhythmic movements of the large muscle groups. Following the warm-up, the body is stretched to gently take the major joints through their full range of motion before increasing the intensity. An example of this type of stretching is a full lunge where the back knee touches the ground before the next leg is moved forward. Ballistic stretching Ballistic stretching is generally known as ‘bounce stretching’. It was very popular in the 1950s and 1960s but has since been discredited because of the damage it causes to muscles. Due to the force of the stretch, the stretch reflex comes into play and places great pressure on the muscle fibres. Extended use of ballistic stretching will, in fact, decrease flexibility. This is because it leaves muscles in a state of contraction and the repair of the micro tears (and, in some cases, macro tears) leads to a further reduction in flexibility. However, ballistic stretching can be useful in some performances where ballistic and explosive actions are required. In these cases it should form part of the third stage of warm-up after a general warm-up, a static stretch period and an active stretch period.
Strength The term ‘strength training’ implies that strength can be improved through training. Strength can be defined as the ability of muscles to exert force. The greatest force that muscles can exert in a single maximal eff ort is said to be the performer’s absolute strength. There is a close relationship between strength and sports performance. To develop strength, resistance must be applied to muscles as they contract. Often strength training is called resistance training. This resistance can take the form of: the person’s own body weight barbells or dumb-bells weight machine systems hydraulic resistance machines elastic bands water (such as swimming or aquarobics) pulleys or levers. Types of training and training methods
When exploring weight training programs, you need to understand the terminology used to describe the organisation of the exercises. repetitions (reps): how many times the exercise is done without a rest. sets: the number of times you complete a group of repetitions resistance: the weight you are using as a load repetition maximum (RM): the maximum number of times you can lift a given resistance recovery (rest): the time taken between each set spotter: someone who assists the person doing the exercise. Types of training and training methods
Types of training and training methods Strength training is fundamental to improvement in most sports, particularly those in which lifting a weight or opposing a force (such as in football) is involved. Strength programs can be divided into two categories: • isotonic programs — participants raise/lower or pull/push free weights to contract/lengthen muscle fibres. Nearly all strength training is isotonic. • isometric programs — participants develop strength by applying a resistance and using exercises in which muscle length does not change. These programs are useful for body building, improving muscle tone, increasing strength/power and rehabilitation following injury. The differences are illustrated.
Training programs need to challenge athletes physically if the aim is to improve performance. The principles of training guide the athletes about what will work to produce a training effect. These include progressive overload, specificity, reversibility, variety, training thresholds and warm-up and cool-down. It is also important to understand how these principles relate to each type of training. principles of training
Principles of training Progressive overload The basic principle of progressive overload is that a training effect is produced when the system (for example, the cardiovascular system) or tissue (for example, muscle tissue) is worked harder than it is accustomed to working (that is, when it is ‘overloaded’). As the body adapts to the new levels, training should continue to be progressively increased. This progressive overloading, over time, will produce greater maximal eff orts in the system or tissues being trained. Progressive overload can be achieved by varying the frequency, duration and intensity of the training, with increases in intensity having the greatest effect. Considerable stress must be placed on the system or tissue so that improvements can occur. If there is too much overload, fatigue can result as well as potential injury; if training load is too little, the training effect will plateau or decrease. Athletes need to be aware that not all adaptations will occur in the same timeframe and that it is important to increase the workload gradually over a long period so improvements are maintained and overtraining is avoided.
Principles of training Specificity The principle of specificity implies that the greatest gains are made when activity in the training program replicates the movements in the game or activity. That is, training should be specific to the: • task requirements • energy systems required in the task • muscle groups required in the task • components of fitness involved in the task. For example, to be competitive in their chosen sport, long distance runners need to develop the aerobic energy system and leg muscles. A javelin thrower needs to develop the ATP-PC system to throw while, at the same time, developing shoulder, back and arm muscles specific for throwing and power. A squash player will benefit from playing tennis during practise sessions as there is a transfer of skill even though the technique is slightly different.
Principles of training Reversibility The principle of reversibility states that effects of training are reversible, even only after one or two weeks of stopping or reducing training. That is, the training effects will be quickly lost, and the person's performance will decline, and unfortunately often at a rate faster than gains were made. This is often referred to as the detraining effect. Reversibility is evident in all components of fitness such as aerobic and anaerobic fitness, power, strength, muscular endurance, flexibility, and speed. Many athletes take part in off-season training programs to maintain their fitness until the next season begins or injured athletes may take part in other activities to maintain their fitness until recovery takes place. Variety The principle of variety states that athletes need to be challenged by not only the activity but also by the implementation of the activities and this is often achieved by cross-training. Training can often become repetitious and boring, especially if done for many hours over many weeks over many years. This is particularly evident in endurance activities involving few technical skills, for example swimming and running. While the principle of variety is not essential to improve performance it does make training more interesting and enjoyable. Aerobic, anaerobic, strength and flexibility training can take many forms so it can be easy to incorporate this principle into training programs.
Principles of training Warm up and cool down Warming up and cooling down are important components of all training and performance sessions. The warm up aims to prepare the body in readiness for the activity that is to follow by stimulating the cardiorespiratory system thereby increasing blood flow to working muscles, increasing body temperature, making the muscles, ligaments and tendons more supple and elastic, and reducing the possibility of a muscular tear causing injury. A warm up should include three stages: a general warm up; stretching; and a specific warm up and should last for a minimum of 10 minutes. The general warm up involves a gentle use of the large muscle groups in a rhythmic manner that progressively increases in intensity. The stretching stage of the warm up involves stretching the major muscle groups in a slow manner, holding each stretch for 10-30 seconds. This is followed by stretching of specific muscles then dynamic stretching to prepare the muscles for the training or performance. The specific warm up stage involves practising performance-like activities and skills that progressively increase the heart rate and use the muscles and ligaments involved. The cool down, which follows the training or performance session, is effectively the same as the warm up, but in reverse, and is aimed at minimising muscle stiffness and soreness. The cool down, while not as intense or involved as the warm up, allows for the active recovery and gives the body time to return the blood to the heart, rather than letting the blood pool in the muscles. This allows the oxygenated blood to 'flush out' the waste products that form during activity and begin to rebuild the energy stores required for the next performance. The cool down should include a period of aerobic work, gradually decreasing in intensity as well as stretching aimed at reducing muscle soreness and aiding recovery.
Principles of training Training Thresholds Thresholds generally refer to a specific point that, when passed, take the person to a new level. When we train, we expect an improvement in our physical condition. However, for improvement to occur, no matter how small, we must work at a level of intensity that causes our bodies to respond in a particular way. These changes are called adaptations or fitness gains. The magnitude of improvement is approximately proportional to the threshold level at which we work. The lowest level at which we can work and still make some fitness gains is called the training threshold or (where it concerns developing aerobic fitness) aerobic threshold. Thresholds are determined by work intensity, which can be calculated using heart rate. A person’s maximal heart rate (MHR) is estimated at 220 beats/ minute minus age. Therefore, a 20-year-old person would have an MHR of 200 beats per minute. If the aerobic threshold is 70 per cent of MHR, the athlete would be working at a level of intensity that would cause the heart to beat at approximately 140 beats per minute. For most people between 16 and 20 years of age, this is equivalent to a moderately paced jog. When a person is working at a level of intensity above the aerobic training threshold and below the anaerobic threshold, they are working in the aerobic training zone. Exercise here is referred to as steady-state exercise and results in improvements in physical condition. The uppermost level is called the anaerobic threshold.
The aerobic threshold refers to a level of exercise intensity that is sufficient to cause a training effect. This is approximately 70 per cent of a person’s maximal heart rate (MHR). The aerobic training zone refers to a level of intensity that causes the heart rate to be high enough to cause significant training gains. The anaerobic threshold refers to a level of intensity in physical activity where the accumulation of lactic acid in the blood increases very quickly. ANAEROBIC THRESHOLD AEROBIC THRESHOLD principles of training
While training will cause immediate physiological responses in the body, athletes are looking for adaptations and long term responses to improve performance. These adaptations allow the athlete to achieve higher levels of work. They include changes to resting heart rate, stroke volume and cardiac and cardiac output, oxygen uptake and lung capacity, haemoglobin level, muscle hypertrophy, and effects on fast/slow twitch muscle fibres. When an athlete participates in regular aerobic training the body begins to adapt physically to the demands placed upon it. These adaptations allow the body to function more comfortably at existing levels of stress and respond more efficiently to new levels of stress. This makes the body more efficient and capable of more work. Many of the changes occur in the cardiorespiratory system and lead to an improved ability to deliver oxygen to working muscles. When we talk about these changes, terms such as sub-maximal exercise and maximal exercise need to be explained. Sub-maximal exercise is performed at a level below maximum heart rate and the heart rate remains constant or near constant during the activity. Examples include jogging, cycling or swimming for more than 20 minutes. Maximal exercise is activity which leads to a heart rate that approaches its maximal level, such as sprinting. physiological adaptations
Physiological adaptations in response to training Resting heart rate Heart rate is measured in beats per minutes and at rest will beat enough times per minute to deliver oxygen via the blood stream to all the cells of the body. This minimum requirement for oxygen is reflected by the resting heart rate. The amount of oxygen required at rest is determined by your basal metabolic rate. Your level of fitness does not have a significant influence on this requirement. When you undertake an aerobic training program your heart will undergo a significant change and this can lead to a reduction in the number of beats required to meet the needs of the body at rest. In other words, your resting heart rate will fall as your body adapts to the training program being undertaken. Your heart rate will also be lower while undertaking sub-maximal work, such as a step test or other exercises where the same amount of work needs to be performed.
Physiological adaptations in response to training • Stroke Volume and Cardiac Output • The stroke volume is the amount of blood pumped out of the heart per beat. The heart consists of cardiac muscle and like any muscle that undergoes training it will undergo hypertrophy and become more efficient. As the heart becomes more efficient the left ventricle actually becomes bigger and as a result will pump more blood out per beat than pre training. The heart is also more forceful now with each beat as an adaptation. • Cardiac output is the amount of blood pumped out of the heart per minute by the heart. To calculate this, multiply the stroke volume by the heart rate. The heart rate will rise normally under maximal or submaximal activity to increase the ventilation rates around the body. As the stroke volume is bigger, the cardiac output will rise accordingly due to training. This then increases the amount of blood being sent around the body: • Cardiac output (CO) = Stroke volume (SV) X Heart rate (HR)
Physiological adaptations in response to training • Oxygen Uptake and Lung Capacity • Oxygen uptake or consumption (VO2 = volume of oxygen) is a measure of the amount of oxygen that the body can deliver and use at rest and during exercise. As exercise intensity increases, the demand for oxygen in the mitochondria of working muscle cells increases, hence the need for VO2 to increase. VO2 is measured in litres/min and is usually expressed relative to a persons body weight (mls of oxygen/kg body weight/min) so individuals can be compared to each other. Endurance athletes typically record VO2 max values of 60+ ml/kg/min. VO2max is the maximum amount of oxygen, that can be used in one minute, and is a good predictor of fitness in the general population. Endurance training can cause improvements in VO2max of 15-20%. • Lung capacity is the amount of air that can move in and out of the lungs during a breath. The lung capacity of athletes after undergoing training will remain the same as they were before training. As a result of training their is an increased efficiency of the lungs, rather than changes in the size of the lungs.
Physiological adaptations in response to training • Haemoglobin Level • Haemoglobin is found in red blood cells (RBC’s) and binds to O2 in order to transport it around the body. Blood can carry about 18-20ml O2 per 100ml of blood. Men have higher levels of haemoglobin (compared to women), as do people who live at high altitude and those who have artificially increased levels of RBC’s (eg blood doping). Studies suggest with training, an individual can increase their haemoglobin levels by up to 20%. VO2max of 15-20%. • Muscle hypertrophy • Muscle hypertrophy is the increase of the size of muscle cells that generally occurs with anaerobic forms of training such as weight/resistance training. • During weight training (or other strenuous activity), microscopic damage occurs to the muscle fibres, referred to as microtrauma. When microtrauma occurs, the body responds by overcompensating, replacing the damaged tissue and adding more, so that the risk of repeat damage is reduced – this is thought to be the basis of muscular hypertrophy.
Fast/slow twitch muscle fibres • There are two types of muscle fibre: • slow-twitch muscle fibres • fast-twitch muscle fibres • Slow-twitch fibres contract slowly and release energy gradually as required by the body during steady-state activity such as jogging, cycling and endurance swimming. These fibres are efficient in using oxygen to generate energy (ATP), making them resistant to fatigue but unable to produce the power of fast-twitch fibres. When the body is engaged in endurance-type activity, slow-twitch fibres are preferentially recruited for the movement because they are more efficient in meeting the immediate demands of the working muscles. • Fast-twitch fibres contract quickly and release energy rapidly however, they fatigue rapidly due to anaerobic metabolism providing the energy. The body preferentially recruits fast-twitch fibres to perform explosive type activities such as weight-lifting, field athletics and sprint track athletics. Physiological adaptations
The individuals ratio of fast-twitch to slow-twitch muscle fibre is genetically determined, making them more suited to certain sports or activities. The ratio of both types of muscle fibre varies in each individual and each muscle. In summary: • The metabolic capabilities of both types of fibres can improve through specific strength and endurance training. • Sprinters and weight lifters have a large percentage of fast-twitch fibres. • Marathon runners generally have a higher percentage of slow twitch fibres. • Muscles that primarily maintain posture against gravity (core strength) require more endurance and generally have a higher percentage of slow-twitch fibres. • Muscles that produce powerful, rapid, explosive strength movements tend to have a greater percentage of fast-twitch fibres. • Sport specific training will assist in appropriate development and adaptation of each type of muscle fibre. Fast-twitch muscle fibres benefit most by anaerobic training, such as sprint or interval training and resistance training. Slow-twitch muscle fibres benefit most from endurance type activities that engage the aerobic system, such as running, cycling and swimming. Physiological adaptations
Physiological adaptations in response to training • Summary of Physiological Adaptations in Response to Aerobic Training • • Lower resting heart rate • • Lower heart rate for submaximal workload • • Increased maximal stroke volume • • Increased maximal cardiac output • • Increased maximal oxygen consumption • • Anaerobic threshold increased • • Increase in the ability to withstand a greater oxygen debt • • Faster recovery after completion of exercise • Note: the number of fast/slow twitch muscle fibres is not significantly affected by training.