How The Cardiovascular, Respiratory, Neuromuscular, Energy And Skeletal Systems Adapt To Chronic Exercise

Chronic exercise

Long-term exercise is also known as chronic exercise.  Chronic exercise programme is one which the exercise period is not less than eight weeks. This chronic exercise will affect the body in many different ways allowing it to cope with greater stresses. These adaptations will allow you to exercise at higher intensities for longer. Responses to long term exercise include changes to the heart, lungs and muscles, although the extent of the changed depends on the type and intensity of exercise undertaken.

Cardiovascular endurance

The main adaptations that occur to the cardiovascular system through endurance training are concerned with increasing the delivery of oxygen to the working muscles.

Cardiac hypertrophy                                                                                                                                                                                        The cardiac muscle surrounding the heart hypertrophies, resulting in thicker, stronger walls and therefore increases in heart volumes. The more blood pumped around the body per minute, the faster Oxygen is delivered to the working muscles. Regular aerobic exercise stimulates the increase in both the thickness of the muscle fibres and the number of contractile elements contained in the fibres. An increase in heart size indicates the adjustments of a healthy heart to exercise training. It is the left ventricle that adapts the greatest extent as well as the chamber size increasing. These changes are reversible when you discontinue aerobic training.

Stroke volume

Stroke volume is measured in milliliters per beat. During physical activity, stroke volume can increase anywhere from 60 to 110 milliliters, depending on intensity. the stroke volume of the trained person will be higher than that of the non-trained person. This increase in stroke volume also leads to a higher cardiac output than the non-trained exerciser. This increase in cardiac output during your exercise can help your body meet its demands for oxygen to your exercising muscles. Long term exercise increases the size of the heart. This increase in size increases the athlete’s stroke volume. As a result of increased stroke volume and cardiac hypertrophy the resting heart rate decreases   

Cardiac output

The heart rate decreases after long term exercise because of an increased stroke volume and cardiac hypertrophy. The heart becomes bigger and can pump more blood per beat it and doesn’t have to beat as often when the body is at rest. But cardiac output decreases only slightly following long term exercise. During maximal exercise on the other hand, cardiac output increases significantly. This is a result of an increase in maximal stoke volume as maximal heart rate remains unchanged with training.

Heart rate

The resting heart rate decreases in trained individuals due to the more efficient circulatory system. The heart rate decreases after long term exercise because of a increased stroke volume and cardiac hypertrophy. Getting fitter causes a decrease in resting pulse rate. Some top athletes resting pulse rate between 30 and 40 beats per minute. As the heart becomes bigger it takes less effort to pump blood around the body and resting heart rate is reduced. Resting heart rate can decrease significantly following training in a previously sedentary individual. During a 10 week exercise program, an individual with an initial resting heart rate of 80 beats per minute can reasonably expect to see a reduction of about 10 beats per minute in their resting heart rate.

Blood volume, Vessels and Pressure                                                                                                                                                                   The long term effect of aerobic exercise is an approximately 20 percent increase in blood volume. An increase in blood volume means your body can deliver more oxygen to your working muscles. Your body will also be able to better regulate your body temperature during exercise. Blood volume is the amount of blood circulating in the body. Blood volume increases because of capillarisation during long term exercise. When the blood volume increases there is more blood to circulate which allows greater supply of oxygen to skeletal muscles. Arterial walls become more elastic which allows greater tolerance of changes in blood pressure. Blood plasma is also increased which changes the ratio of red blood cell volume to total blood volume this will lower blood viscosity making the blood flow more easily and reduce blood pressure. The number of red blood cells increases, improving the body’s ability to transport Oxygen to the muscles for aerobic energy production. Arterial walls become more elastic which allows greater tolerance of changes in blood pressure. Long-term aerobic exercise improves the elasticity of your blood vessels, or the ability of your vessels to expand and contract. The improved elasticity delivers more oxygen and glucose to your muscles at a faster rate. A long-term adaptation to aerobic exercise is a decrease in both your systolic and diastolic blood pressures during rest and during sub-maximal exercise

Capillarisation                                                                                                                                                                                               Long term exercise can lead to the development of a capillary network to a part of the body. The amount of capillaries and the capillary density increase which improves the cardiac and skeletal muscle cappillarisation because of aerobic training. The density of the capillary beds in the muscles and surrounding the heart and lungs increases as more branches develop. This allows more efficient gaseous exchange of Oxygen and Carbon Dioxide. An increase in the number and diameter of capillaries surrounding the alveoli leads to an increase in the efficiency of gaseous exchange.

Capillaries surround small air sacs, called alveoli, inside your lungs that capture the oxygen you breathe in. Your lungs adapt to regular exercise by activating more alveoli. More alveoli can supply more oxygen to working muscles and tissues throughout your body. Pneumonia occurs when fluids in your lung prevent alveoli from exchanging gases. Pneumonia is an inflammation of the lung tissue affecting one or both sides of the chest that often occurs as a result of an infection. Having more alveoli can suppress the effects of pneumonia by reducing the proportion of alveoli that are affected by this disease. Emphysema occurs when alveolar walls break down and gradually reduce the exchange of oxygen and carbon dioxide in your lungs. Regular exercises may help slow the progression of emphysema by increasing the number gas-exchanging alveoli.

Respiratory adaptations

Minute ventilation

Minute ventilation depends on breathing rate and tidal volume. In regular adults they can generally achieve 100 litres per minute however in a trained athlete minute ventilation can increase over time by 50 per cent to 150 litres per minute.

Respiratory muscles

Your diaphragm is a broad band of muscle that sits under your lungs and forms the base of a region known as the thoracic cavity by attaching to the lower parts of your ribs, sternum and spine. The intercostals form the muscle tissue in between individual ribs. The long-term effect of exercise is to build the endurance of these respiratory muscles, allowing deeper, fuller and more efficient breaths.Long term exercise can make the external intercostal muscles get stronger which make a greater degree of contraction so while the internal intercostals muscles relax during inspiration it means more airs forced into the lungs. During expiration the greater degree of contraction of the internal intercostals and the relaxation of external intercostals allows you to breath out a greater volume of air. This results in larger respiratory volumes, which allows more Oxygen to be diffused into the blood flow which is V02 max.

Resting lung volumes

Long term exercise will increase the surface area of the lungs which will allow a greater volume of deoxygenated blood to access to the sites of gaseous exchange within the lungs. The increased ability of the blood to take on more oxygen due to the increased surface area of alveoli, aids trained athletes a lot.  Vital capacity slightly increases along with tidal volume during maximal exercise the increased strength of the respiratory muscles are responsible for this change

Exercise exposes your lungs to stronger rushes of airflow. Aerobic exercise in particular exposes your lungs to strong and constant rushes of air. This activity helps clear mucus in your lungs. Mucus build up can diminish your lung capacity and lead to bacterial infections. “According to a 1997 "European Respiratory Journal" article by the University of Ulsan's Wong Don Kim, excessive mucus in your lungs is associated with higher mortality, may obstruct airflow and increases your risk of infections. Regular exercise can help offset these conditions by preventing mucus from building up in your lungs” This shows exercising regularly for a long time can help prevent risk of infections because exercise prevents mucus from building up in the lungs. 

Oxygen diffusion rate                                                                                                                                                                                                An increase in the number and diameter of capillaries surrounding the alveoli leads to an increase in the efficiency of gaseous exchange. An increase in diffusion rates in tissues favours oxygen movement from the capillaries to the tissues and carbon dioxide from the cells to the blood. Long term exercise causes these rates to increase allowing both oxygen and carbon dioxide to diffuse more quickly Capillaries are the smallest blood vessels in your body. Oxygen seeps out of thin capillary walls as carbon dioxide seeps in during respiration. Exercise stimulates vasodilation, which increases the diameter of blood vessels in your body, including the capillaries. Your body adapts to long-term exercise by increasing the size and number of capillaries, including alveolar capillaries. This adaptation makes the exchange of carbon dioxide and oxygen more efficient.

Neuromuscular adaptations

Hypertrophy

Long term exercise increases the cross sectional size of existing muscle tissue this is because of the increase in the number of myofibrils and connective tissue. High intensity training results in hypertrophy of fast twitch muscle fibres. This results in more ATP and PC stored in them and increased capacity to generate them due to more enzymes in the bigger muscles.

Tendon strength

Long term exercise increases tendon strength. Tendons have to adapt to meet increased demands of the skeletal muscles. Tendons connect muscle to bone and come under forces during exercise forcing them to adapt to become stronger to better deal with the forces applied, it also becomes of greater important to adapt and maintain a balance as the muscles they are attached to grow in size, results in a greater force and pull upon the bone, or improve in their ability to move in faster and more repeated bouts.

Myoglobin stores

The amount of myoglobin within skeletal muscle increases, which allows more Oxygen to be stored within the muscle, and transported to the mitochondria. Long term training makes muscles increase their oxidative capacity which is achieved by an increase supply of ATP also the ability of the muscles to store myoglobin. Oxygen delivery to muscles increased by increased myoglobin and capillarisation

Number of mitochondria                                                                                                                                                                                               With training muscles tend to increase their oxidative capacity. This is achieved by an increase in the number of mitochondria in the muscle cells. Increased numbers of mitochondria means an increase in the rate of energy production. Muscles consume more oxygen due to increased size and number of mitochondria therefore glycogen and fats are utilized more effectively. Increased numbers of mitochondria means an increase in the rate of energy production. Long term training increases the quantity of mitochondria for metabolism to take place, this in combination with a greater potential storage capacity for glycogen, fat and Myoglobin results in an increase in the output of ATP, particularly via the Aerobic pathway.

Storage of glycogen and triglycerides

Long term training makes muscles increase their oxidative capacity which is achieved by an increase supply of ATP also the ability of the muscles to store larger amounts of glycogen and the ability to use triglycerides as an energy source can also be stored. Endurance training causes an increase of muscle glycogen. Slow twitch fibres can grow by 22% therefore increasing the amount of glycogen stores so exercise can be prolonged

Neural pathways

Long term exercise makes the neural pathways change these changes are cellular adaptations, modifications of neurotransmitters, alterations in reflex and chemical and biochemical responses. Long term exercise also creates new neural pathways. Exercise gets blood to your brain bringing it glucose for energy and oxygen to soak up the toxic electrons and it stimulates the protein that keeps the neurons connecting. 

Energy system adaptations

Increased anaerobic and aerobic enzymes

Long term exercise makes muscle tissue generate ATP. The increase of the size of mitochondria is usually accompanied by an increase in the level of aerobic system enzymes. These changes account for why athletes can sustain prolonged periods of aerobic exercise as a result of long term exercise.

The anaerobic system increases in enzymes that control the anaerobic phase of glucose breakdown. Aerobic training will increase the number on mitochondria in slow twitch fibres, this allows greater production of energy by producing more ATP through the aerobic energy system.

Fats as an energy source

During exercise fat combustion powers almost all exercise. Fat oxidation increases if exercise extends over an hour. Towards the end of an exercise session fat accounts for 75 per cent of the total energy required. Long term exercise will make athletes burn fat as a fuel than non trained adults. Training will increase the amount of enzymes in our body needed to break down body fats and store it in our muscle tissue so it can be used as an energy source

Tolerance to lactic acid.

As a result of working anaerobically and enduring levels of lactic acid the muscles adapt in order to withstand greater levels of lactic acid in the future, this is coupled with the bodies increasingly improved ability to clear lactic acid and regulate current levels, as a result of a combination of the enhancements and adaptations of the other bodily systems to long term exercise and the body experience at clearing previous bouts of lactic acid. Long term exercise will saturate the muscles in lactic acid which educates your body in dealing with it more effectively. Anaerobic training will help our bodies tolerate lower PH levels. This means more energy can be produced by the lactic acid energy system

Skeletal adaptations

Increased calcium stores

Long term exercise slows the rate of skeletal aging. Athletes who maintain physically active lifestyles have greater bone mass compared to those who take part less. Weight bearing or resistance training will result in us becoming stronger and able to withstand impact better this happens because exercise means mineral content is increased making bones harder.

Tendon strength

Tendons attach muscles to bones or to muscles. Long term exercise increases tendon strength. Tendons have to adapt to meet increased demands of the skeletal. Strength training increases the strength of muscle tendons which makes them less prone to injury

Stretch of ligaments and stronger ligaments

Long term exercise will make ligaments increase their stretch so that they can cope with the body’s gain of muscle. The ligaments adaption occurs when fibroblast secretions increase the production of collagen fibres relative to the training undertaken. Ligaments become slightly stretchier which will help reduce injuries such as joint strains. Our bones are held together by ligaments. When exposed to regular exercise, ligaments will become stronger and more resistant to injury. Because ligaments have no or a very poor blood supply, any adaptations are very slow to develop.

Exercise increases the production of synovial fluid which keeps our joints lubricated and makes them supple. Synovial fluid production increases the range of movement available at your joints in the short term. Exercise increases the range of movement available at our joints as more lubricating synovial fluid is released into them. Mobility exercises such as arm circles and knee bends keep our joints supple by ensuring a steady supply of synovial fluid. Exercise also helps increase the thickness of cartilage in joints and increases the production of synovial fluid this will strengthen joints and make them less prone to injury.

Weight-bearing exercise such as strength training and running put stress through your bones. In response to this stress our bodies produce cells called osteoblasts which build new bone and make our bones stronger and denser. Increased bone density can prevent a condition called osteoporosis which is the weakening of bone and an increased likelihood of suffering fractures.