Aerobic and Endurance Training

• Endurance/aerobic exercise includes long distance events such as marathons, open water swimming, and stage racing/tour events.
• Shorter efforts lasting 10-60 minutes, like 5000m or 10,000m runs, 1500m swims, or 40km cycling also count.
• Middle distance events lasting 2-10 minutes still rely on aerobic input.

Aerobic Training

• Typically involves long distance training at a relatively low intensity to complete the distance.
• Longer interval sets, known as tempo work, are considered hard.
• Shorter pace work and strength training are also important.

Determinants and Goals

• High VO2MAX, high lactate threshold, and high efficiency determine endurance exercise performance.
• Endurance training aims to increase VO2MAX, improve lactate threshold, and improve efficiency.
• The overall goal is to maximize workload for a set distance or time.

Aerobic Fitness/Capacity

• Aerobic fitness/capacity can also be referred to as physical capacity, maximal oxygen consumption/uptake, and maximal aerobic power.
• VO2MAX is the maximal rate of oxygen uptake.

Aerobic Fitness Defined

• VO2MAX determines aerobic capacity/fitness.
• It's the maximal amount of O2 lungs, heart, and vasculature can move to working muscles, as well as the maximal amount of O2 muscles can utilize.
• VO2MAX is measured in absolute (L·min-1) or relative (ml·kg-1·min-1) terms.

Importance of VO2MAX

• VO2MAX is a key determinant of endurance exercise potential.
• A higher VO2MAX generally means a greater capacity to perform aerobic exercise and better performance compared to someone with a lower VO2MAX.
• Genetics play a significant role, accounting for ~30-50% of VO2MAX.

Relative vs Absolute VO2MAX

• High relative VO2MAX is important for weight-unsupported sports like distance running and uphill cycling.
• High absolute VO2MAX is more important for weight-supported sports like rowing, swimming, and flat cycling.
• Correlation does not imply causation

Lactate Threshold (LT2)

• A person’s LT2 is functionally very important for endurance performance.
• It represents a "functional threshold" of power output/speed that can be maintained for a length of time.
• VO2MAX indicates the capacity to do endurance exercise, while LT2 is a major element of functional capacity. Both are crucial for overall performance.

Importance of LT2

• Runners A and B both have a VO2MAX of 4.5 L·min-1. Runner A's LT occurs at 70% VO2MAX, so they are consuming 3.2 L·min-1 at LT2. Runner B's LT occurs at 80% VO2MAX, so they are consuming 3.6 L·min-1 at LT2.
• Runner B can consume 0.4 L·min-1 more than runner A before lactate seriously accumulates, meaning runner B performs better.

Efficiency/Economy

• Mechanical efficiency is the ratio of work done to energy expended.
• Exercise efficiency is the ratio of oxygen consumed (VO2) to the speed/power output.
• Efficiency varies by 20-40% between individuals.
• It relies on technique and matching energy supply to demand.
• It is often related to longer distance athletes and those that have trained a long time.

Determinants of Endurance Exercise Performance Summary

• High VO2MAX, high lactate threshold and high efficiency determine endurance exercise performance, and serve as the goals of training.

Central and Peripherial Changes

• Cardiovascular and pulmonary changes occur in the central aspect after adaptions to training
• Cardiac hypertrophy, changes in blood volume, heart rate, stroke volume (SV) and cardiac output (Q) occur in the cardiovasucular system following aerobic training

Cardiac Hypertrophy

• Long-term aerobic training can cause the heart to hypertrophy, similar to other muscles.
• Increased size of the left ventricular cavity (eccentric hypertrophy) is typically seen.
• Slight thickening of left ventricle walls (concentric hypertrophy) is more common in resistance training, including changes in cardiac blood supply.
• This adaptation is temporary and varies with genetics and training.
• Sedentary males have a heart volume around ~800 g total, while endurance-trained hearts are ~25% larger.
• Increased left ventricle cavity volume leads to increased end diastolic volume (EDV); increasing "preload" and contractility via the Frank-Starling mechanism.

Changes in Blood Volume (BV)

• Initial changes in blood volume occur rapidly and continue for weeks.
• Most of the increase comes from an increase in plasma volume (PV) of 10-20%, which can occur within several training sessions.
• After 2-3 weeks, haematocrit (RBC - mostly Hb) volumes also expand by ~10%.
• Overall blood viscosity is slightly less due to the increase not being as great as PV, smoothing blood flow and causing the appearance of being anaemic.
• Overall, blood volume increases by ~8-10%.

Changes in Heart Rate

• Endurance training increases vagal dominance of HR control.
• Parasympathetic activity increases, while sympathetic activity decreases, lowering the intrinsic firing rate of the SA node.
• This results in lower resting and submaximal HR (bradycardia), while HRMAX is similar but slightly lower.
• It allows more time for the heart to fill between beats.
• Lowering in HR shows adaptation.

Changes in Stroke Volume

• Stroke Volume increases at rest and during exercise due to hypertrophy of the left ventricle, cardiac and arterial stiffness, increased diastolic filling time, and increased contractility of cardiac tissue.
• Age and gender do not impact the the effectiveness

Change in Cardiac Output

• Cardiac output is the most important adaption, which is due to the increase in stroke volume.
• Stroke volume increases with training, and cardiac output has a generally linear relation with VO2.
• Elite athletes are distinguished by their high cardiac output, along with having considerably less variation in HR and a-vO2 difference.

Pulmonary Change Summary

• There are no particular changes in the structure of the lung
• The lungs have a large reserve capacity – especially compared to CV and metabolic systems
• Metabolic adaptations in respiratory muscles
• Increased strength and endurance in the respiratory muscles

Pulmonary Changes

• Although there is no structural change in the lung, there are some functional changes.
• One will puff less for an equivalent submaximal workload after training, largely due to peripheral changes that affect respiration

Peripheral Changes

• Peripheral changes occur through:
  • Capillarisation
  • Metabolic changes
  • Muscular changes
  • A-VO2 difference

Capillarisation

• Training increases the number of capillaries that surround and perfuse our muscles.
• Increases surface area for exchange of gases and metabolites, and decrease transfer distance between muscle and blood (in and out)
• Greater capillary supply is related to increased VO2MAX.

Metabolic Changes

• Two very important adaptations related to our energy supply occur following aerobic training: Changes to the size and volume of mitochondria and changes to fuel usage patterns

Mitochondria

• Mitochondria increase in size and number -á50 – 100% within 6 weeks.
• Adaptation occurs in response to contraction in working muscles.
• The electron transport chain
• The Krebs/citric acid cycle
• Glycolysis

Enzymes

• Increased mitochondrial capacity means that there are more OXIDATIVE ENZYMES!
• Citrate synthase (CS), Malate dehydrogenase (MDH) and Succinate dehydrogenase (SDH) are examples

Fuel Usage Patterns

• Triglycerides increase fatty acid oxidation at rest and during submaximal exercise occuring within about 2 weeks of training.
• There is increased utilization of intramuscular triglycerides.
• There is increased utilization of intramuscular triglycerides Caused by increased capillarisation and transport into muscle and mitochondria and an increase in fat mobilising and metabolising enzymes.
• Overall increased mitochondria enhances aerobic respitory capactiy and allows for sympathetic influence.

Glucose and Glycogen

• Increased use of aerobic pathways and fatty acids for fuel results in glycogen being broken down to glucose which spares glycogen.
• This defers fatigue due to low glycogen and slows the rate of glycogen use because aerobic pathways now have more of capacity to metabolise glycogen due to aerobic glycolysis.

Reviews of Fibre Types

• Long-term aerobic training change the fibre type, or more likely the characteristics of fibre types.
• Type I can become Type IIA and then Type IIX.
• It shift to use slow myosin ATPase, which result sin better efficency with less energy use
• Type I fibres may hypertrophy.

Myoglobin

• Transports O2 from cell membrane to the mitochondria
• Type I fibres contain more than type II
• There is some proof in animal models but not many in humans

Definition av-o2 differences

• Aerobic training increases the amount of O2 removed from the blood during exercise. In turn imporving the av-o2 differences.
• This is due to a variety of factors, but is primarily is due to capillarization and an improved mitochondrial function.

Definition of Blood Lactate

• Speaking more generally speaking, endurance training improves blood threshold.
• Via mechanism helps use the aerobic pathways and removal of lactate

Summary of Aerobic ADaptation Training

• Increase rate of Lactate removal, the body use the pathways involved of lactate
• With improvemnts of various systems, better the ETC and other incoming nutrients will be improved.

Rate of Lactate Removal

• More energy means a lower rate of Lactate production
• CV systems, which increased the capcaity to move H2 and and other materials out of the body
• Body can now work higher before fatuiuge

Summary of Changes

• Ventricle changes, submax heart rate and other volume changes and other factors of the body

Factors of Change

• Mitochondrial changes with improved capillarisation

Goal Settings of VO2Max

• Depends on start level, but one highly trained, there is a plateau
• Peripheral and central changes