Chronic adaptations to aerobic training - muscular

Increased size and number of mitochondria

• More and larger mitochondria increase aerobic ATP production by oxidising glycogen and triglycerides, enhancing energy supply for prolonged exercise.

  

Increased myoglobin stores

• Aerobic training raises myoglobin content in muscles, improving oxygen extraction and delivery to mitochondria for energy production. Myoglobin shuttles oxygen to mitochondria for aerobic ATP resynthesis.

  

Increased muscular fuel stores and oxidative enzymes

• Aerobic training increases glycogen and triglyceride storage in slow-twitch fibers and boosts oxidative enzymes, enhancing aerobic ATP production and reducing reliance on anaerobic glycolysis until higher intensities.

Increased oxidation of glucose and triglycerides

• Aerobic training enhances muscle fiber capacity to oxidise glucose and triglycerides. Greater fat oxidation spares glycogen, allowing athletes to sustain higher intensities for longer, improving aerobic performance.

Increased arteriovenous oxygen difference (A-VO₂ diff)

• Trained athletes extract more oxygen into muscles due to higher myoglobin and mitochondrial content.

• Venous oxygen concentration decreases, increasing A-VO₂ diff during submaximal and maximal exercise, allowing greater oxygen uptake and aerobic energy production.

Muscle fibre adaptation from aerobic training

• Fast-twitch type A fibres can adopt characteristics of slow-twitch fibres through endurance training, allowing more ATP to be generated aerobically.

  

Table of characteristics of fast and slow twitch muscle fibres

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Mitochondria size and number adaptation

• Increase

Myoglobin content/stores adaptation

• Increase

Muscular fuel stores adaptation

• Glycogen stores: Increase

• Triglyceride stores: Increase

Oxidative enzymes adaptation

• Increase

Slow-twitch muscle fibre size adaptation

• Increase

Muscle fibre type adaptation

• No change; however, fast-twitch oxidative (type 2A) fibres may take on characteristics of slow-twitch fibres

A-VO₂ difference adaptation

• Increase

Oxidation of fat adaptation

• Increase at submaximal and maximal exercise

Oxidation of glycogen adaptation

• Increase at submaximal exercise, decrease at maximal exercise (glycogen sparing)

Increased size and number of mitochondria

• More and larger mitochondria enhance aerobic ATP resynthesis by oxidising glycogen and triglycerides, improving energy production for muscle contraction.

Increased myoglobin stores

• More myoglobin extracts oxygen from red blood cells and delivers it to mitochondria, increasing oxygen availability for aerobic ATP production.

Increased muscular fuel storage and oxidative enzymes

• Aerobic training increases glycogen and triglyceride stores in slow-twitch fibres and boosts oxidative enzymes, reducing reliance on anaerobic glycolysis and allowing higher intensity work for longer.

Increased arteriovenous oxygen difference (A-VO₂ diff)

• Enhanced oxygen extraction by muscles lowers venous oxygen concentration, increasing A-VO₂ diff and improving aerobic energy production.

Muscle fibre adaptation

• Fast-twitch type 2A fibres can adopt slow-twitch characteristics, allowing greater aerobic ATP production and reducing fatigue during prolonged exercise.