Chronic Adaptations to Aerobic Training

Vocabulary flashcards defining key cardiovascular, respiratory, and muscular adaptations resulting from chronic aerobic training.

Tidal volume

• Tidal volume: the amount of air breathed in or out with each breath.

• Aerobic training increases tidal volume by strengthening the respiratory muscles.

• This allows more air and oxygen to enter the lungs and be diffused into the blood.

More oxygen can then be delivered to working muscles, improving aerobic performance.

Decreased resting and submaximal respiratory rate (RR)

• Breathing rate: the number of breaths taken per minute.

• Aerobic training reduces breathing rate at rest and during submaximal exercise.

• Improved lung function allows more oxygen to be extracted with each breath.

Stronger respiratory muscles make breathing more efficient.

Pulmonary diffusion

 Pulmonary diffusion: aerobic training increases the surface area of the alveoli.  This allows more oxygen to enter the blood and more carbon dioxide to leave the blood.  This improves the efficiency of gas exchange between the alveoli and capillaries.

Increased left ventricle size and volume

•       The heart increases in size – Cardiac hypertrophy.

•       The left ventricle size is increased, leading to an increased blood volume in the left ventricle.

•       This increases oxygenated blood pumped out of the left ventricle

•       Stroke volume

Increased capillarization of heart muscle

Increased heart capillarization is the growth of more tiny blood vessels within the heart muscle wall. This happens because repeated cardio exercise demands high blood flow, which triggers the body to build these new pathways. As a result, the heart receives a better supply of oxygen and fuel, allowing it to pump strongly for long periods without fatiguing.

Increased stroke volume

•       The amount of blood ejected by the left ventricle per beat

•       Aerobic training increases stroke volume at rest, during sub-maximal exercise and during maximal exercise

•       As the left ventricle increases in size it provides a more powerful ejection of blood.

•       With greater stroke volume, the more oxygen can be delivered to the working muscles, which improves their ability to resynthesize ATP aerobically.

Decreased resting and submaximal HR and faster recovery HR

•       Aerobic training lowers heart rate at both rest and sub-maximal exercise

•       This means that the heart is more efficient

•       Steady state will therefore be achieved at a lower heart rate

•       It also means that it takes less time for the body to return to resting levels following exercise

Increased cardiac output during maximal exercise

Increased cardiac output during maximal exercise is a significant rise in the maximum volume of blood the heart pumps per minute. This change happens because long-term training enlarges the left ventricle and strengthens contractions, which drastically boosts maximum stroke volume. Consequently, substantially more oxygen reaches working muscles, allowing an athlete to sustain a higher exercise intensity and achieve a superior VO2 max.

Decreased blood pressure

•       Aerobic training lowers blood pressure at rest and during sub-maximal exercise, but does not affect BP during maximal exercise.

•       Improved blood vessel elasticity and function and reduced peripheral resistance contribute to a more efficient blood flow, which lowers blood pressure.

•       This helps to reduce resistance to blood flow and reduces strain on the heart, thereby decreasing the risk of heart attack and other cardiovascular conditions.

Increased capillarization of skeletal muscle

•       Aerobic training results in an increase in capillarisation of skeletal muscle.

•       Most evident in the slow twitch muscle fibres.

•       This can increase a persons VO2 max as the diffusion of oxygen from the capillaries into the mitochondria (cell structures that convert oxygen into ATP) is a major factory in maximizing the rate of oxygen consumption of the muscles.

•       An increase in mitochondria results in more aerobic production of ATP. This will decrease the reliance of the athlete on the anaerobic energy systems and reduce the production of lactate.

Increased blood volume

Increased blood volume is a rise in the total amount of fluid circulating throughout the cardiovascular system, driven by an expansion of both blood plasma and red blood cells. This adaptation occurs because regular aerobic training triggers hormonal signals that make the kidneys retain water and stimulates bone marrow to produce more red blood cells. Consequently, this expansion optimizes the body's sweat-based cooling capacity and maximizes oxygen delivery to the muscles, which significantly enhances long-term endurance.

Increased fibre size and capillary density

Increased fibre size and capillary density is the enlargement of slow-twitch muscle fibres paired with a higher concentration of surrounding capillaries. This muscular adaptation occurs because sustained aerobic training repeatedly challenges skeletal muscles, prompting the slow-twitch fibres to grow and triggering the body to build new blood vessel networks. Consequently, this maximizes blood flow and increases the surface area for gas exchange, allowing more oxygen to reach working muscles to significantly boost long-term endurance.

Fibre type

Fibre type adaptations refer to changes within skeletal muscle cells, specifically a shift toward a higher percentage or enhanced capacity of aerobic, slow-twitch (Type I) fibres. This muscular change occurs because regular endurance training causes fast-twitch fibres (specifically Type IIx) to take on characteristics of fatigue-resistant Type IIa or Type I fibres over time. Consequently, this structural shift increases the muscle's overall efficiency at utilizing oxygen, which vastly improves prolonged endurance performance.

Myoglobin

Increased myoglobin stores is a rise in the amount of oxygen-binding iron proteins found directly inside your skeletal muscle cells. This adaptation occurs because regular aerobic training repeatedly challenges the muscle's oxygen uptake system, signaling the cells to manufacture and store more myoglobin. Consequently, it accelerates the extraction and transport of oxygen from the cell membrane straight to the mitochondria, which maximizes aerobic energy production during prolonged exercise.

Increased Mitochondria

Increased mitochondrial size and density refers to a significant growth in both the physical size and total number of the "powerhouse" structures within skeletal muscle cells. This adaptation occurs because sustained aerobic training puts a continuous demand on the body's energy production system, signaling the muscle cells to replicate and enlarge these structures to handle the workload. Consequently, it drastically scales up the muscle's capacity to synthesize ATP aerobically, allowing an athlete to maintain a higher intensity for much longer periods.

Fuel Stores

Increased fuel stores refers to a significant rise in the storage capacities of intramuscular glycogen and triglycerides within the skeletal muscle cells. This adaptation occurs because regular endurance training repeatedly depletes energy reserves, signaling the body to upregulate storage enzymes so it can stockpile more fuel during recovery. Consequently, having larger local energy reserves prevents premature "bonking" or hitting the wall, allowing athletes to sustain prolonged physical activity before fatiguing.

Increased oxidative enzymes

Increased oxidative enzymes refers to a significant rise in the quantity and activity of specialized proteins within the mitochondria of slow-twitch muscle fibres. This adaptation occurs because chronic aerobic training places repeated metabolic demands on the muscle cells, stimulating them to produce more enzymes like succinate dehydrogenase (SDH) and citrate synthase during recovery. Consequently, this accelerates the breakdown of glycogen and fats, which increases the rate of aerobic ATP production and allows an athlete to maintain a higher intensity before hitting their LIP (Lactate Inflection Point).

Oxidation of glycogen and fat

Increased oxidation of glycogen and fat refers to an enhanced ability of skeletal muscles to break down carbohydrates and lipids using oxygen within the mitochondria. This metabolic adaptation occurs because chronic aerobic training elevates mitochondrial density and oxidative enzyme activity, allowing the muscle cells to metabolise these fuels far more efficiently. Consequently, it promotes glycogen sparing at submaximal intensities by utilizing fats more readily, which delays glycogen depletion and allows the athlete to sustain a higher performance intensity before reaching their LIP (Lactate Inflection Point).

AVO2 Difference

Increased a-vO2 difference refers to a greater difference in oxygen concentration between arterial blood entering the muscle and venous blood leaving it during maximal exercise. This adaptation occurs because chronic aerobic training increases muscle capillary density, myoglobin stores, and mitochondrial size and number, which slows blood transit time and enhances oxygen extraction. Consequently, it allows the working muscles to extract and utilize a higher percentage of the delivered oxygen, directly boosting the athlete's VO2 max and overall aerobic capacity.