Heart Rate
Resting heart rate averages 60 to 80 beats per minute in healthy adults. In inactive, middle aged individuals it may reach as high as 100 beats per minute. In elite endurance athletes there heart rates as low as 28 to 40 beats per minute. Before exercise begins heart rate increases in anticipation. This is known as the anticipatory response stage. It occurs through the release of neurotransmitters called epinephrine and norepinephrine also known as adrenaline and noradrenaline. After the initial anticipatory response, heart rate increases in a direct quantity to exercise intensity until a maximum heart rate is reached. The only direct method for determining maximum heart rate is to exercise at increasing intensities until a plateau in heart rate is found despite the increasing work rate (cannot do anything more). Although the heart rate increases quickly with the beginning of exercise, providing the intensity remains constant, the heart rate will then level off. This is known as steady-state heart rate where the demands of the active tissues can be sufficiently met by the cardiovascular system. Aerobic processes in cellular respiration can only happen if oxygen is present whereas anaerobic processes do not use oxygen, so the pyruvate product ATP is one kind of pyruvate which remains in place to be broken down and/or catalysed by other reactions.
Stroke Volume
Stroke volume is the amount of blood released per beat from the left ventricle and measured in ml per beat. Stroke volume increases proportionately to the exercise intensity. In untrained individuals stroke volume at rest averages around 50-70ml per beat increasing up to 110-130ml per beat during intense, concentrated physical activity. In elite athletes resting stroke volume averages 90-110ml per beat increasing to as much as 150-220ml per beat. Stroke volume may increase only up to 40-60% of maximal volume after which it plateaus and levels off. Past this relative exercise intensity, stroke volume remains unaffected right up until the point of exhaustion and fatigue. However it has been said stroke volume continues to rise until the point of exhaustion. Swimmers see a smaller increase in stroke volume compared to runners or cyclists. Stroke volume increase with the start of exercise because the left ventricle fills more completely, stretching it further, with the elastic retreat producing a more powerful contraction. Other contributing factors include increased contractility of the ventricles and reduced exterior resistance due to greater vasodilation of the blood vessels. An increase in stroke volume is only seen through aerobic exercises like running, swimming or cycling. Many anaerobic exercises like weightlifting are short periods of time and affect your heart in a different way.
Cardiac Output
Cardiac output is the amount of blood pumped by the heart in 1 minute measured in Litres per minute. It is a produce of stroke volume and heart rate (SV x HR). If either the heart rate or stroke volume increases, or both, the cardiac output increases to. Cardiac output increases proportionally with exercise intensity, which is expectable because of the response of heart rate and stroke volume to activity. At rest the cardiac output is about 5Litres per minute. During intense exercise this can increase to 20-40 litres per minute. Achieving a steady state in exercise is the aim of many aerobic training, which is training at a set intensity for a lengthy period of time. In anaerobic fitness there is a greater demand for the cardiovascular system to remove the build-up of waste products (CO2 and lactate). As there is less recovery time between work periods with muscular endurance and anaerobic training, the heart rate tends to rise highly throughout the workout as well as having peaks at the end of each set. Because of this it takes longer (between 20 and 40 minutes) for heart rate and stroke volume to return to normal resting levels at the end of the workout.
Blood Flow
The vascular system can reallocate blood to those tissues with the greatest instant demand and away from areas that have a smaller amount of demand for oxygen. At rest, 15-20% of circulating blood is supplied to the skeletal muscle. During vigorous, high intensity exercise this increases to 80-85% of cardiac output. Blood is pushed away from major organs such as the kidneys, liver, stomach and intestines and is then redirected and transported to the skin to promote heat loss. Athletes are often recommended not to eat several hours before training or competing. This is due to having food in the stomach will lead to a struggle for blood flow between the digestive system and muscles.
Blood Pressure
Blood pressure is affected both during and after steady-state exercise. During steady-state exercise, there is a temporary increase in systolic and a decrease in diastolic blood pressure. These numbers represent the pressure in your arteries while your heart is contracting and between heart beats, individually. Long-term steady-state aerobic exercise can reduce overall blood pressure over time. Resting blood pressure generally is reduced by endurance training. You can measure your pulse rate at home by yourself. All you need is a stop watch and a quiet environment where you can relax. After at least 10 minutes (to confirm you find a resting pulse) you can count your pulse by gently placing two fingers on the inside of your other wrist, and count the beats for 30 seconds. You then double this figure to get your resting pulse which should usually be between 60 and 100 beats per minute.
Respiratory System Responses
Involving of a series of body parts including the lungs, diaphragm and nasal cavity, the respiratory system is in charge for the transporting of oxygen and carbon dioxide to and from muscles and tissues. During exercise, the respiratory system increases to meet the demands of the working muscles. The respiratory system also uses the cardiovascular system (heart, blood and blood vessels)to transport oxygen and carbon dioxide.
Before exercise begins there is a little rise in a persons breathing rate, this is known as the anticipatory rise. When exercise begins there is an almost instant increase in breathing rate. This comes as a consequence of receptors working in both the muscles and joints sensing by-products and harmful substances. The amount of air we breathe in and out per minute is called pulmonary ventilation. When exercising the body needs the production of ATP to be constant, to produce ATP oxygen and nutrients are needed to create this ATP, however as a result of producing ATP one of the by-products is carbon dioxide and the body needs to remove this as soon as possible. Chemoreceptors (in the aortic arch and carotid bodies) and mechanoreceptors (in the joints, tendons and muscles) detect these by-products such as lactic acid and carbon dioxide and the receptors that detect these harmful substances send signals to the brain. The brain then sends signals to the respiratory muscles and the lungs to tell them to increase the breathing rate faster to get rid of these substances quickly. As well as breathing more rapidly to get rid of the harmful substances, we also need to breathe more rapidly to get a quicker supply of oxygen to meet the muscles demand for more oxygen after the changes in exercise intensify and gradually get harder.
Tidal volume is the amount of air held in the lungs. The amount of air breathed out in and out in each breath is approximately 500cm3, however only about 2/3 of the oxygen you breathe in reaches the alveoli where the gas exchange in the body happens and the rest of the oxygen is just breathed out. During exercise tidal volumes increases to allow more oxygen to reach muscles that need the oxygen, to have a supply of oxygen in the blood to be used. The intercostal muscles which help with the expansion of the thoracic cavity, workharder to increase the expansion during inhalation to be able to take in more air. If the concentration of the exercise continues to rise, the amounts of oxygen you are able to take in will eventually reach its maximal point and the person will reach their co2 max, this means that they have reached their maximal level for oxygen consumption.
The neuromuscular response to exercise
Skeletal muscles are voluntary muscles that when signalled by nerves make movement. Together, muscles and their corresponding nerves make up the neuromuscular system. When the neuromuscular system is healthy and efficient, it can endure an active lifestyle free of pain and injury.The Sliding-Filament Theory explains how skeletal muscles contract and relax as a result of thick and thin filaments sliding forward and backward. This action is controlled by the nervous system made up of nerves called neurons. A motor neuron triggers the sliding action of filaments that lead to muscle contraction. For this process to take place, oxygen binds to blood haemoglobin and is then transported inside muscle cells called mitochondria. Mitochondrion uses oxygen to produce ATP for working muscles. Exercise increases oxygen demand and the process of the Sliding-Filament Theory. During steady-state exercise muscles are driven by metabolic pathways that need oxygen, also known as aerobic exercise. These aerobic pathways are very efficient in achieving a balance between the energy vital by active muscles and the delivery of oxygen needed to create that energy. During aerobic exercise, rhythmic muscle contractions pump blood throughout the muscular system, delivering oxygen to mitochondria for ATP production. An example of aerobic activities is jogging and yoga classes. If a jogger gradually increases distance, the response is an increase in muscle efficiency. If mileage is increased rapidly, a destructive response happens. During persistent steady-state exercise without periods of rest, repetitive muscle contractions can lead to fatigue. If the neuromuscular system is forced to continue working in a fatigued state, it becomes susceptible to overuse injuries such as inflammatory response and stress fractures. However, when given frequent recovery breaks, the neuromuscular system will heal. When performing exercises that includesuitable recovery stretches, like yoga, the neuromuscular system endures significant evolutionary changes. A reorganization response causes the neuromuscular system to grow and. This improves the overall function of the neuromuscular system by enhancing nerve-muscle signalling, promoting muscle efficiency. Other factors contributing to a growth response are good posture and repetition and period of exercise. Gradual progression and sufficient recovery stretches will support a healthy neuromuscular response, keeping a person active and injury free.
The energy system response to exercise
When doing anaerobic exercise the body needs to meet the rapid higher energy demand. Stored ATP is the first energy source which is used. This lasts for approximately 2 seconds. When the stored ATP is broken down into ADP + P, the rising ADP level encourages Creatine Kinase to start the breakdown of Phosphocreatine. The ATP-PC system can only last 8-10 seconds before PC stores are exhausted and can no longer be used. The lactic acid system (Anaerobic glycolysis) must then take over as the dominant source of energy production. High intensity exercise can last between 3 and 5 minutes using this system. If the exercise continues at a high intensity, and Oxygen is not quickly available at a fast enough speed to allow aerobic metabolism to take over, the creation of lactic acid will reach the point where it thenaffects with the muscular function. This is called the Lactate threshold. Muscles begin to fatigue when ATP resynthesizes supplies can no longer meet the demand.
When doing aerobics exercise the need of Oxygen to be present for aerobic metabolism is low to moderate intensity exercise, which is powered by anaerobic metabolism. Sustained low to reasonable intensity exercise is then powered by carbohydrate and fat stores using aerobic metabolism. The intensity and duration of exercise controls which fuel source is used. Fat metabolism is a slow process so therefore can only be used as fuel for exercise at less than 60% VO2 max. Carbohydrate is a much quicker fuel source and so can be used for exercise up to 80% (in trained athletic individuals). Carbohydrate supplies within the muscle and liver can fuel exercise for up to 80 minutes. As carbohydrate stores get lower, the body has to depend more on the fat stores. The intensity of exercise which can be sustained drops as fat cannot supply the essential amount of energy.
There is a limited supply of ATP in the muscles for maximal exercise. ATP is broken down into ADP + P + energy to allow muscles to contract. The CP system resynthesizes ATP and PC is broken down into Creatine and Phosphate and energy, this energy resynthesizes ATP from ADP and phosphate. There are only enough stores of PC for 10 seconds of exercise. This is only used in high concentration, short bursts of exercises, for example the 100 meter sprint. Fatigue happens when PC runs out. PC can be re made very swiftly which allows athletes to do repeatsessions of shortspurts of activity without becoming exhausted quickly.