Aerobic Training Adaptations

Adaptations to Aerobic Training

• Aerobic training improves cardiorespiratory endurance, the ability to sustain prolonged dynamic exercise.
• Adaptations involve multiple systems: cardiovascular, respiratory, muscle, and metabolic.
• Endurance training increases maximal endurance capacity (VO2max) and submaximal endurance capacity.
• Submaximal endurance results in a lower heart rate at the same submaximal exercise intensity, improving performance in endurance events.
• The Fick equation plays a key role in studying aerobic capacity.

Aerobic Adaptations

• Increased VO2max occurs due to increased oxygen-carrying capacity (hemoglobin & myoglobin), plasma volume, capillarization, mitochondrial number and size, and mitochondrial enzymes.
• Fiber diameter decreases (important for endurance).
• Heart function (stroke volume and cardiac output) improves.
• Shift towards more oxidative muscle fibers (Type IIa).

Overload Example

• Arteries and veins form intricate networks in muscle tissue.
• Overload stimulus (increased blood flow from exercise) promotes capillary development, especially during intense aerobic training.
• Trained muscle has an increased capillary-to-muscle fiber ratio.
• Enhanced microcirculation improves heat and metabolic byproducts removal from active tissues, facilitating oxygen, nutrient, and hormone delivery.

Muscular Adaptations

• Myoplasticity, the ability of muscle fibers to adjust genetic machinery for protein quantity or quality, is determined by the demands on the muscle.
• Transcription involves expressing target genes in DNA to create mRNA.
• Translation by ribosomes results in amino acids attaching to create proteins.

Cardiovascular Adaptations

• Oxygen transport system and Fick equation are crucial for understanding cardiovascular performance.
• VO2max increases due to the combination of stroke volume, heart rate, and (a-v)O2 difference.
• Cardiovascular hypertrophy (heart mass and left ventricular volume) increases with training.
• Plasma volume, left ventricular volume, and end-diastolic volume increase.
• This leads to greater stroke volume and cardiac output.
• Volume loading effect (Frank-Starling Law) explains the relationship between end-diastolic volume and stroke volume.
• Resting heart rate decreases markedly over time through training (parasympathetic activity increase and sympathetic activity decrease).
• Submaximal heart rate for the same absolute intensity decreases with training.
• Maximal heart rate remains essentially unchanged. Recovery heart rate is faster.
• These adaptations are used to predict VO2 max.

Mitochondrial Adaptations

• Enhanced endurance exercise training leads to higher mitochondrial density, thereby improving (a-v)O2 difference.
• Training increases mitochondrial biogenesis and reduces degradation.
• PGC-1a plays a key regulatory role in these processes
• Mitochondrial function can be measured using markers such as succinate dehydrogenase (SDH).

Lactate Threshold

• Lactate threshold increases in response to aerobic training.
• This results in the ability to sustain higher workloads without accumulating lactate.
• Enhanced aerobic system efficiency and increased ATP production capacity during exercise are key contributors.

Bioenergetic Adaptations

• Aerobic adaptations impact various bioenergetic factors, including aerobic enzymes, oxidative potential of fast-twitch (FT) fibers, glycogen levels, capillaries, and cross-sectional area of slow-twitch (ST) fibers.
• These adaptations translate to prolonged exercise endurance.

Typical Metabolic Values

• Endurance training correlates with significant improvement in multiple metabolic and physiological parameters.
• Table 21.2 provides a wide variety of measurable metrics affected by training.

Explore the key adaptations that occur due to aerobic training, focusing on improvements in cardiovascular, respiratory, muscular, and metabolic systems. Understand how these adaptations enhance performance, including increases in VO2max and shifts in muscle fiber types. Gain insights into the physiological changes that occur when engaging in endurance training.