chronic adaptations

Chronic adaptations:

• Physiological changes of the respiratory, cardiovascular and muscular systems as a result of long-term training

• Acute responses are responses of the body to exercise in the short term

• Chronic training adaptations can be split into aerobic-based training and anaerobic-based training

• Aerobic based (continuous, long interval, HIIT, fartlek) --> improved Vo2 max and LIP

  • Respiratory

  • Cardiovascular

  • Muscular (slow twitch)

• Anaerobic based training (short and intermediate - interval, resistance, circuit, plyometric and flexibility) --> improved lactate tolerance and speed + force of muscle contraction

  • Muscular (fast twitch)

  • Neuromuscular (fast twitch)

Four link explanation:

• Training stimulus --> chronic adaptation --> physiological reason --> performance impact

  

• Aerobic-based training seeks to improve the amount of ATP the aerobic energy system can produce and how efficiently it does

• Respiratory adaptations occur at the lungs and aim to increase oxygen uptake to increase ATP available for working muscles

Respiratory adaptations to take in more O2 to the blood via the lungs:

• Increased myoglobin

• Increased mitochondria

• Increased TV

• Increased maximal ventilation

• Increased pulmonary diffusion

• Decreased resting and submaximal respiratory rates

Increased tidal volume:

• Tidal volume: the amount of air inhaled and exhaled during a single, regular breath (L/breath)

• Respiratory muscles (diaphragm + intercostal muscles) contract more forcefully --> ribcage expands outwards --> more oxygen available; improved efficiency of respiratory muscles

• More oxygen available to diffuse into capillaries surrounding alveoli

• TV will stop increasing when it reaches finite capacity; chest cavity cannot be expanded any further --> TV plateaus

Increased maximal ventilation:

• Ventilation: the amount of air inspired and expired per minute (L/min)

  • V = TV x RR

• Since TV plateaus, further increases in V are due to RR

  • At maximal workloads, RR is at its peak

Increased pulmonary alveolar diffusion:

• Aerobic based training increases the size and number of alveoli in the lungs

  • Increased surface area allows for greater gaseous exchange (O2 and CO2 can be diffused from areas of high conc. to low conc.)

  • Systemic circuit: blood vessels transporting oxygenated blood from left side of heart to tissues of body

Decreased resting and submaximal respiratory rates:

• Increased efficiency in lungs --> can intake greater amount of O2 for less energy input --> decrease in resting and submaximal RR

• Body can supply sufficient oxygen with fewer breaths per minute up to submaximal workloads

  • Performer can work at higher aerobic workloads with less oxygen and fuel usage --> decreased rate of fatigue

• Cardiovascular adaptations aim to increase delivery/supply of oxygen and fuels to working muscles + improve removal of wastes and metabolic by products due to increased muscle contraction

• Occurs in/to the heart, blood vessels and blood

Cardiovascular adaptations to increase oxygen delivery of oxygenated blood to working muscles:

Cardio (heart):

• Increased stroke volume

• Increased maximal cardiac output

• Decreased resting and submaximal heart rates

Vascular (blood vessels):

• Increased heart capillarisation

• Increased muscle capillarisation

• Increased blood (plasma and haemoglobin) volume

• Reduced systolic and diastolic blood pressure

Increased stroke volume:

• SV: amount of blood ejected from the left ventricle of the heart with each contraction

• Aerobic based activities lead to hypertrophy of heart muscle

  • Hypertrophy: enlargement of organ/tissue due to increase in size of its cells

  • The left and right atria and ventricles will increase in size and will take in + squeeze out more blood --> better transportation of oxygen to working muscles

• Heart wall will also increase in size and contract more forcefully --> increased SV

• Higher SV also lets performer reach steady state faster

Increased maximal cardiac output:

• Cardiac output: amount of blood ejected from the left ventricle per min

  • Q = SV x HR

• Increased blood volumes --> higher red blood concentration (carry oxygen) and plasma volumes

  • Plasma reduces viscosity of blood --> blood can travel faster to working muscles

  • Plasma helps to remove waste products through transport to organs/skin --> aids in thermoregulation

Decreased resting and submaximal heart rates:

• Cardiac hypertrophy --> pumps more blood per contraction --> does not need to pump as frequency to supply muscles with sufficient o2 to meet demands

• Endurance-trained: has less rapid increase in SV, and quicker ability to plateau at submaximal intensities

Increased heart capillarisation:

• Aerobic training increases cross sectional area of the coronary arteries and associated capillaries that supply to the heart --> more oxygen feeding the myocardium (muscular tissue of the heart)

Increased muscle capillarisation:

• Capillaries supplying blood/oxygen to working muscles increase in size and number (particularly ST fibres)

• Larger surface area for muscle to blood exchange, shorter oxygen diffusion distance and higher average red blood cell transit time --> energy supplied quicker and muscles can work at higher intensities aerobically for longer periods without accumulation of fatiguing by products

• Waste product removal is faster --> repair and recovery is faster --> shorter time between training sessions

Reduced diastolic and systolic blood pressure

• If higher blood volume due to plasma --> less viscous blood and more easy to be pumped by the heart

• Reduces pressure on heart during contractions, lowering blood pressure during work and rest

AEROBIC

• Aerobic training will allow for muscular adaptations via slow-twitch fibres --> improvement in muscular endurance

• Some fast-twitch fibres can adopt ST characteristics

Aerobic muscular adaptations:

• Increased mitochondrial density

• Increased myoglobin

• Increased arteriovenous oxygen difference

• Increased oxidative enzymes

• Increased glycogen stores

• Increased fat oxidation

Increased mitochondrial density

• Mitochondrion is responsible for the conversion of fats and carbohydrates into ATP at the muscles via aerobic or cellular respiration

• Greater demands on ST fibres --> greater size and number of mitochondria to meet demands --> greater use of oxygen to produce more ATP and energy

• Also increase in mitochondrial enzymes which are responsible for producing aerobic ATP at a faster rate

Increased myoglobin

• Aids to transport oxygen across cell membranes to reach the mitochondria. More myoglobin = faster transfer

Increased arteriovenous oxygen difference

• AV-o2 diff: difference between oxygen concentration in arterial blood and venous blood to measure the amount of oxygen taken up from blood by tissues

• More myoglobin and mitochondria work to increase a-vo2 diff

Increased oxidative enzymes

• Work to convert ADP and phosphate to ATP in the mitochondria

Increased glycogen stores

• Aerobic training increases stores of muscle and liver glycogen, especially in ST muscle fibres

Increased fat oxidation

• Increased intramuscular triglycerides and free fatty acids fuel oxidative enzymes, resulting in increased ability to oxidise fat

  • Fat is a major fuel source during low intensity efforts

• Is advantageous as athletes can conserve glycogen stores and use fat instead in steady state; glycogen sparing

  • Leads to extended carbohydrate availability and use

  • Increased ability to use carbohydrate when working above LIP

ANAEROBIC

Muscle hypertrophy

• Anaerobic training increases the cross sectional area of fast twitch fibres (both type II fibres)

  • Does by increasing cross-sectional area of myofibrils

  • And increased actin and myosin filaments (protein based filaments in muscles responsible for muscle contractions and movement)

  • Increased size and strength of tendons (connective tissues)

• Larger myofibrils store greater amounts of anaerobic fuels (ATP, CP and glycogen) and the enzymes that help convert fuel to energy rapidly

Increased anaerobic enzymes

• Enzymes increase the rate at which reactions occur in the body

• ATPase and creatine kinase are important enzymes which help rapidly break ATP and CP down --> rapid production of energy

• Glycolytic enzymes produce AT from ADP by using glucose as the food fuel

  • Aerobic glycolysis produces 20-39x more than anaerobic glycolysis which is 2-3 molecules of ATP per molecule of glucose

Increased fuel stores

• Fast twitch fibres develop larger myofibrils for greater storage of CP, ATP and CHO (glucose) to produce ATP anaerobically

Improved anaerobic capacity

• Ability to produce energy via the ATP-CP and anaerobic glycolysis system

• Increased CP and glycogen stores + anaerobic enzyme increase the rate and duration of anaerobic energy

Neuromuscular adaptations: anaerobic-based training

• Resistance and plyometric training programs increase muscular strength and power without increasing muscle fibre size/cross sectional area

• Initial change in force production is due to neural adaptations

Increased motor unit recruitment

• Anaerobic based training (plyometrics, short interval, resistance) targets FT fibres and enhances body's ability to recruit motor units --> greater generation of force

Improved synchronisation of motor units

• According to size principle, motor units are recruited from smallest to largest, so ST--> FT

• During heavy loads (weight, speed) FT fibres will take over

• Anaerobic based training activates high-threshold motor units which improves ability to synchronise the activation of more motor units at the same time

• This allows neuromuscular coordination to become more automatic and creates more rapid and powerful muscle contractions

Increased motor unit firing frequency

• Resistance and plyometric training increase firing rate/rate coding of neural impulses

• Greater the frequency, increased summation of impulses

  • Successive signals sent to muscle fibre before it has a chance to relax from the previous one

  • Directly increases the force and duration of muscle contraction

Decreased neural inhibition

• A muscle strain (injury to a muscle or tendon) occur due to excessive tension in the muscles or overstretching of the tendons --> partial or complete tear of these tissues

• Tendons have built in protective mechanism were receptors detect excessive tension and create a 'reflex inhibition' on the neurons supplying the muscles, causing an instantaneous drop in force output

• Regular resistance training decreases inhibitory signals which allows for more powerful contraction

  

VO2 max = Qmax x a-vO2 difference

Absolute Vo2 max: the maximum amount of oxygen that can be inspired, transported and utilised in 1 minute (L/min)

Relative Vo2 max: the maximum amount of oxygen that a person inspires, transports and utilises in 1 min, but is measured relative to their weight (mL/min/kg)

• LIP: the final point where lactate production and lactate removal are equal

  • Represents the final exercise intensity or oxygen uptake value at which blood lactate concentration is relatively low

  • Represents the maximal intensity at which blood lactate is said to be in steady state

Essentially, you LIP is the maximum intensity where the aerobic system is producing enough ATP to not have to rely on much Anaerobic contribution. Beyond LIP, the anaerobic glycolysis systems will start to increase ATP production to address the shortfall in ATP from the aerobic system at that intensity.

• Lactate tolerance: the ability to buffer accumulating lactic acid so it does not interfere with muscle contractions and cause decreased force and frequency

Aerobic training and LIP

• Aerobic training often improves LIP without a corresponding increase in VO2 max, LIP is the best indicator of aerobic power

• Untrained athletes can start training below LIP to see improvement

  • 55-70% VO2 max/ 70-80% HRmax

• Endurance trained athletes should train at a higher level/just below the LIP to see improvement

  • 75-90% VO2 max/ 85-95% HRmax

• Alternation between continuous and HIIT training methods are most effective to improve LIP

• Aerobic training increases LIP by increasing lactate clearance from muscles through:

  • Greater mitochondrial density --> higher aerobic ATP production and oxidisation of lactate back to pyruvate

  • Increased transport of lactate from muscle cells to bloodstream

  • Greater conversion of lactate back to glucose to produce more ATP

• PPT SAYS: Aerobic training increases LIP through

  • Greater mitochondrial density

  • Increased capability to oxidise fat and carbohydrates through oxidative enzymes

Consider TAUK-TQ for graphs

Title - Blood lactate across running speed

Axes: Percentage of VO2 max/ running speed/ blood lactate concentration

Units: %/ km/h / mmol/L

Key: Untrained, Moderately trained, Highly trained

Question:

Trend: Rightward shift/increased LIP as training status increases

Answering questions for LIP:
1. Data: state the rightward shift using speed/power/intensity values

2. Adaptation: connection to the adaptations that lead to an improvement in LIP, localised to the specific muscle cells used in chronic exercise

3. Mechanism: Explain how the adaptation increases LIP

• Individuals with a greater proportion of ST fibres relative to FT fibres have a greater ability to oxidise fatty acids in mitochondria, and in return have a higher LIP

4. Performance: ability to work at a higher intensity aerobically  +  delayed metabolic by product contribution at a higher intensity

 Improving lactate tolerance:

• Anaerobic training (short interval) improves lactate tolerance; focuses on anaerobic glycolysis system and places high stress within fast-twitch fibres

• When AG system activated and trained over time, number and function of 'muscle buffers' located within muscles increases

• When LIP has been surpassed, steady state has been surpassed and lactic acid accumulates

• Neuromuscular doesn't function well under these conditions --> decreased muscle contraction force

Adaptation 1: Increased fuel (CP and glycogen) stores

• Greater generation of ATP via explosive ATP-CP system

• Greater ability to utilise the anaerobic glycolysis system to produce energy

• Greater rate of anaerobic ATP supply (performance)

Adaptation 2: Increased glycolytic capacity

• Increased glycolytic enzymes leads to faster ATP resynthesis through AG during high intensity work --> increased activity/capacity

• Increased glycogen (fuel) stores make energy more readily available

• Greater rate/capacity of anaerobic ATP supply --> higher blood lactate (performance impact)

Adaptation 3: Increased muscle buffering capacity

• Muscle buffering: ability of muscles to neutralise accumulating lactic acid during high intensity exercise, thus delaying the onset of fatigue

• Muscle buffering reduces accumulating H+ ions and helps stabilise pH of the muscles --> contractile function is maintained for longer

• Less performance decline/ greater high intensity work (performance impact)

• Improved buffering and removal capacities of muscles --> higher concentration of muscle and blood lactate after exercise