Chronic adaptations in response to aerobic training

Chronic cardiovascular adaptations in response to aerobic training

Chronic cardiovascular adaptions all work to increase the amount of blood and in turn oxygen getting to the working muscles. With more oxygen getting to the working muscles athletes have reduced reliance on anaerobic pathways for ATP production which means a reduction in the amount of fatigue inducing by-products of these systems being produced. This allows the athlete to work at a higher intensity for longer before experiencing fatigue.It is important to remember that unlike actute response chronic adaptations are long lasting and occur as a result of training. 

Decreased resting heart rate

There is a decrease in resting heart rate as due to training there is an increase in stroke volume meaning there is an increase in the amount of blood volume the heart pumps with each contraction.Therefore while at rest an individual with a higher stoke volume can meet the oxygen demands with a lower heart rate as more blood is being pumped during each contraction.

Increased Stroke volume

  • Increased stroke volume is caused by an increase in the size of the heart muscle, it allows for the heart to fill with a greater amount of blood meaning a greater volume of blood is pumped out per contraction. More blood being pumped around the body and ejected from the heart means the muscles are supplied with more oxygen and can produce ATP aerobically with greater efficiency. Thus being able to work at a higher intensity aerobically for longer and reducing the reliance on anaerobic energy systems.
  • The average stroke volume at rest for an untrained male is about 70-80 millilitres per beat and during exercise it may increase to around 110 mL per beat.
    Whereas a trained male endurance athlete may have stroke volume of 100 millilitres per beat and during exercise may be as high as 130mL per beat.
  • Women tend to have smaller stroke volumes due to smaller heart size.

Increases size of heart muscle (Cardiac hypertrophy)

An increase in the heart muscle facilitates the increase in stroke volume, blood pressure and cardiac output as an increase in the size of the heart muscle allows it to fill with more blood. A greater volume of blood in the heart causes blood to be more forcefully ejected from the heart. This increased contraction force and blood volume provides more oxygen to the athlete allowing them to more efficiently produce ATP aerobically.

Increased Cardiac Output

Cardiac output is calculated by (stroke volume X heart rate). Therefore as stroke volume is increased in response to training there is an increase in cardiac output. However at rest cardiac output remains unchanged, as while at rest heart rate decreases to facilitate for the increase in stroke volume.
Untrained males may have a cardiac output of 20-22L per min.Whilst a trained athlete may have a cardiac output of 30L per minute.

Decreased blood pressure

Blood pressure decreases for both the systolic(contraction phase) and diastolic(relaxation phase) phases of the heart during rest and exercise. This reduces the resistance to blood flow allowing it to be pumped around the body more efficiently.

Increased capillerisation of the skeletal muscle

There is an increase in the number and density of capillaries within skeletal muscle meaning that muscle cells have a greater blood and oxygen supply.

Increases blood volume and haemoglobin levels

The amount of blood plasma increases and so to do the amount of red blood cells that contain the oxygen carrying protein haemoglobin, an increase in red blood cells increases the body’s oxygen carrying capacity allowing it to deliver more oxygen to the working muscles increasing performance.

Decreased blood cholesterol,triglycerides and low density lipids (LDLs)

Regular aerobic training results in a decrease in blood cholesterol, triglycerides and low density lipids, these substances are linked to causing heart disease. The actual mechanisms are not needed to know at this level only that they decrease.

Increased high density lipids

High density lipids(HDL’s ) are increased these are good lipids for the body. The actual mechanisms for this are not part of this course.

Increased capillerisation of the heart

There is an increase in the number and density of capillaries supplying the heart with blood this allows the cardiac muscle of the heart to have greater access to oxygen and can work at higher intensities for longer.

Chronic Respiratory adaptations in response to aerobic training

The chronic respiratory adaptations as a result of aerobic training work to improve the amount of oxygen getting into the body and transported in the blood, similar to the cardiovascular adaptations these changes work to improve the efficiency in the use of oxygen to produce ATP by the body. Increased efficiency in the use of oxygen by the body reduces the reliance on anaerobic pathways to provide ATP which in turn reduces the amount of fatigue inducing by-products.

Respiratory rate decreases

Respiratory rate decreases at rest and exercise due to the increase in tidal volume which is the amount of oxygen inhaled and exhaled per breath.

Increased tidal volume

The amount of oxygen that is inhaled per breath is increased. Allowing more oxygen to get into the body and being transported to the working muscles.

Increased pulmonary diffusion

Is the amount of oxygen diffusing from the lungs into the blood as there is a greater amount of oxygen breathed in per breath meaning there is more oxygen available to diffuse into the blood stream.

Increased oxygen uptake (VO2 max)

This means there is an increase in the amount of oxygen taken in, transported around and utilised by the body. A high level of VO2 max for an adult male is considered to be around 60mL/kg/min

Increased lung ventilation

Lung ventilation is calculated by (respiration rate X tidal volume). Due to the fact that aerobic training results in increased tidal volume lung ventilation is also increased. Although there is a decrease in respiratory rate this is not enough to off set the increase in tidal volume.

Increased lactate inflection point (LIP)

Lactate inflection point is increased meaning the body is able to get in and transport enough oxygen so that there is sufficient oxygen to remove lactic acid from the blood delaying the onset of fatigue.

Chronic Muscular adaptations in response to aerobic training

Chronic muscular adaptations predominantly occur in the red slow twitch type 1 muscle fibres. These are the muscle fibres used predominantly for aerobic events as they contain a high number of mitochondria. These adaptations work to improve the speed at which fuel is broken down in the presence of oxygen and to increase the efficiency in the use and extraction of oxygen obtained from the blood.

Adaptation of muscle fibres

Through appropriate training some of the fast twitch type 2A muscle fibres may take on characteristics usually associated with slow twitch type 1 muscle fibres. This means there are more muscle fibres to carry out aerobic ATP production, increasing the amount of ATP the body can produce aerobically at any give time.

Increased number and size of mitochondria within muscle fibres

Mitochondria are the sites within cells that carry out aerobic ATP production, an increase in the number of these sites increases the body’s ability to produce ATP aerobically. The increase in mitochondrial size and number is a major factor in increasing an individuals lactate inflection point.

Increased myoglobin within muscles

Myoglobin is a protein located within the muscles that binds to oxygen, it is responsible for taking oxygen from the blood into the muscle. An increase in the levels of myoglobin increases the muscles ability to extract oxygen from the blood.

Increase in muscular fuel stores

With training the muscle stores a greater amount of fuel stores such as glucose so that it can be readily broken down to produce energy.

Increase oxidation of fats and glycogen

Other muscular adaptations that lead to an increase in the body’s ability to produce ATP aerobically also facilitates an increase in the use of fats in ATP production allowing the body to spare glycogen and delay fatigue brought about by depletion of glycogen stores.

Decreased lactic acid production

As there is an increase in the body’s ability to produce ATP aerobically to meet energy demands of exercise there is a decrease in the reliance on anaerobic pathways to provide the required energy.

Increased Oxidative enzymes

Increases the speed and capacity of the muscle to produce ATP aerobically. In this case enzymes speed up the chemical breakdown of fuel for energy production.

Increased AVO2 difference

Due to increased myoglobin in the muscle and a greater difference in oxygen concentration between the musclesa and the blood, the muscle is able to extract a greater amount of oxygen from the blood. This leads to an increase in AVO2 difference as if more oxygen is extracted from the blood there is a larger difference in oxygen levels of the arteries compared to oxygen levels within the veins.

Increased muscle size (Hypertrophy)

Muscle size increases to accommodate for the increase in muscular fuel stores and muscle fibres.

Glossary

Adaptation: a long-term physiological change in response to training loads that allows the body to meet new demands.
Capillerisation: Is the increase in density or amount of capillaries which are the small single-celled blood vessels that allow exchange of oxygen into the cells within the muscle.
Cardiac output: Is the amount of blood pumped around the body per heart beat. It can be calculated by (stroke volume X heart rate)
Stroke volume: Is the amount or volume of blood ejected from the heart per beat.
Diffusion: Movement of substances across cell membrane, in this case it usually refers to the movement of oxygen and carbon dioxide from muscle cells and alveoli in the lung to the blood.
Oxygen Uptake:The maximum amount of oxygen a person can get in,transport and utilise to produce ATP.
Tidal Volume: The amount of oxygen breathed in and out in one breath.
Lactate Inflection Point(LIP): Is the lactate inflection point which is the point where lactic acid production is equal to lactic acid removal.
AVO2 difference: The difference in oxygen concentration of the arteries compared to the veins. It therefore is a measure of the amount of oxygen taken up by the muscle.