(Final Exam) Pt. 2 Physiological Responses to Aerobic and Anaerobic Training

Principle of training

• […]

  • Training effect occurs when a physiological system is exercised at a level beyond which it is normally accustomed

    • Variables that constitute the overload: i) Frequency, ii) intensity, and iii) duration of exercise

• […]

  • Adaptation we experience is specific to what type of exercise we do.

  • Training effect is specific to:

    • Muscle fibers recruited during exercise

    • Energy system involved (aerobic vs. anaerobic)

    • Velocity of contraction

    • Type of contraction (eccentric, concentric, isometric)

• […]

  • Gains are lost when training ceases

  • If we stop exercising after 4 weeks our Vo2 max will not be the same

• Overload

• Specificity

• Reversibility

Endurance training and VO2 max

• Training to increase VO2 max

  •   Large muscle groups, [..] activity

  • 20–60 min, ≥3 times/week for ~8-12 weeks, ≥50% VO2max

  • Moderate-intensity continuous training (MICT)

    • 30 -40 min per session

  •   High-intensity interval training (HIIT)

•   Increases in VO2 max with […] training

  •   Average = 15 to 20% increase

  •   Varies from one person to another

  • This is largely because of […].

  • Nonresponders are people who exhibit 2%-3% improvement.

•  Smaller increases in individuals with high initial VO2 max

  • Individuals with high may require higher exercise training intensities (>70% VO2max) to obtain improvements

• dynamic

• endurance

• genetics

Absolute versus Relative VO2max

• […]: volume of oxygen consumed (L/min)

• […]: volume of oxygen consumed relative to body weight (mL/kg/min)

• Take account their body weight

• The female relative Vo2 max is 57.7 mL/kg/min

• The male was 56.6 mL/kg/ min

• […] VO2 value by body weight.

• Absolute

• Relative

• Divide

VO2 max values measured in healthy and clinical populations

Impact of genetics on VO2max and exercise training response

•   […] (genetics)

  •    Determines approximately 50% of VO2 max in sedentary adults

  • Genetics also plays key role in determining the […] response

•   Average improvement in VO2 max is 15 to 20%

• […] responders improve VO2 max by 2 to 3%

•  High responders can improve VO2 max by approximately 50% with rigorous training

• Heritability

• training

• Low

Why does endurance training improve VO2max?

• VO2 max is defined by the Fick equation

  •  VO2 max = maximal cardiac output x (a-vO2 diff)

•     Differences in VO2 max between individuals

  •  Primarily due to differences in […] max

•   […] improvements in VO2 max

  •     […]duration training (approximately 4 months); Increase in stroke volume is dominant factor in increasing VO2 max

  •  […] duration training (approximately 32 months); Both stroke volume and a-vO2 increase to improve VO2 max

• SV

•   Exercise-induced

• Short

• Longer

  

What causes SV to increase as a result of endurance training?

• ↑ […]

  •    ↑ Plasma volume

  •   ↑ Venous return

  •     ↑ Ventricular volume

•  ↑ […]

  •   Greater the stretch greater the contractability.

• ↓ […]

• EDV

• Cardiac contractility

• Afterload

Training-induced increases in arteriovenous O2 difference

• Improved ability of muscle fibers to extract and utilize O2 from the blood

  • ↑ […] density

    •  Slower blood flow velocity through muscle

    •   Allows more oxygen to diffuse

  •   ↑ […] number

  •   There is a plasma volume increase and that increase is due to hormonal changes

  •    Also an increase in […] volume so an increase in size of the left ventricle; then more blood enters the chamber; more blood in chamber is stronger the contraction

• Capillary

• Mitochondrial

• ventricular

Summary of factors that contribute to endurance training induced increases in VO2max

-          An enlarge capillary […] the rate of blood flow and that allows more muscle to diffuse to the muscle fibers

-          Muscle able to extract […] oxygen because of an increasing capillary density, which slow rate blood flow down.

• slows

• more

Effects of endurance training on performance and homeostasis

• Endurance exercise training results in numerous adaptations in muscle fibers that assist in maintaining homeostasis

  • […] in muscle fiber type (fast-to-slow) and increased number of capillaries

  •  […] mitochondrial volume

  • Training-induced changes in […] utilization

  • Increased […] capacity

  • Improved […] regulation

 

• Shift

• Increased

• fuel

• antioxidant

• acid-base

Endurance training promotes a fast-to-slow shift in muscle fiber type and increases capillarization

•     Fast-to-slow shift in muscle fiber type

  •   Reduction in fast fibers and increase in number of slow fibers

  •   Magnitude of fiber type change determined by […] of training, type of training, and genetics

  •   There is a reduction in […] chain but increase in myosin form

  • Shift in muscle fiber type during [..] training.

  • In long term the proportion of type 2 fiber shifts and exceeds the characteristics of type of fiber.

  • Because we have a reduction in the amount of fast myosin heavy chain and increase in slow myosin isophor

• Increased number of […] surround muscle fibers

  • Enhanced diffusion of oxygen

  •  Improved removal of waste

  • Muscle able to extract more oxygen.

• duration

• myosin

• endurance

• capillaries

  

Endurance training increases mitochondrial volume and turnover in skeletal muscle

•   Prioritizes fat as a substrate to ATP

•   Mitochondrial get damaged

•     Endurance training increases the volume of both subsarcolemmal and intermyofibrillar mitochondria in muscle fibers

  • Results in improved oxidative capacity and ability to utilize fat as fuel

  •    Training also increases mitochondrial turnover (i.e., breakdown of damaged mitochondria and replacement with healthy mitochondria)

    • Breakdown of damaged mitochondria is termed “mitophagy”

    •   Some electrons will escape in the matrix and then they react with oxygen and form free radicals and causes problems.

    • All damaged organelles need to be recycled

      •      Called mitophagy

    • If damaged skeletal muscle will be inflamed because of mitophagy

      • Cause more of an acidic environment

Endurance training-induced changes in fuel utilization

•   Increased utilization of fat and sparing of plasma glucose and muscle glycogen

•  Increased transport of FFA into the muscle

  •   Increased fatty acid binding protein and fatty acid translocase (FAT)

•     Transport of FFA from the cytoplasm into the mitochondria

  •    Higher levels of carnitine palmitoyl transferase and FAT

    • Can take fatty acids from the side of salt and bring it into mitochondria and that fatty acid can be converted to acetyl-CoA

      • That how it enters the Krebs cycle.

•     Mitochondrial oxidation of FFA

  •    Increased enzymes of β-oxidation

    •   Increased rate of acetyl-CoA formation§  High citrate (first molecule in the Krebs cycle) level inhibits PFK and glycolysis

    • High citrate (first molecule in the Krebs cycle) level inhibits PFK and glycolysis

•   Endurance training promotes an increase in certain proteins that are able o transport fatty acids into muscle

• These proteins can bring fatty acids into muscle and once fatty acids enter the muscles it is in the cytosol.

Endurance training improves the antioxidant capacity of muscle

• Contracting skeletal muscles produce free radicals o

  •   Radicals promote oxidative damage and muscle fatigue •

•  Training increases endogenous antioxidant enzymes

  •   Improves the ability of muscle fibers to remove radicals

  • Protects against exercise-induced oxidative damage and muscle fatigue

Endurance exercise training improves acid-base balance during exercise

• Lactate dehydrogenase converts pyruvate to lactic

• Isoform is a slightly different version of an original protein.

• Lactate production during exercise

• Endurance exercise promotes the expression of

  

  •   H4 is actually inhibited when pyruvic levels are high

    •   It means some lactate will be produced but not as much. 

    • Isoform promotes the conversion of lactates to pyruvate.

•     Training adaptations

  • Reduced production of H+

  • Increased mitochondrial number

  •  Increased NADH shuttles

Training adaptation-big picture

• Endurance and resistance training promote protein synthesis in muscle fibers

  •    Exercise “stress” activates gene transcription

  •    Activated certain chemical pathways

  •    Pathways promote gene transcription

  •    Genes transcription is process by which genes are activated and expressed.

•    Process of training-induced muscle adaptation

  •    Muscle contraction activates primary and secondary messengers

  •   Results in expression of genes and synthesis of new proteins

    • mRNA levels typically peak in 4–8 hours, back to baseline within 24 hours

    • Daily exercise required for training-induced adaptation

Illustration of the rise and fall of mRNA in muscle following exercise

• Prolonged exercise training increases levels of specific muscle protein.

Primary and secondary signaling pathways interact to promote exercise-induced adaptations

•   Primary and secondary signals lead to muscle adaptations

  •  Increased protein synthesis

• Specific muscle adaptive responses depends on exercise stimulus

  •    Resistance vs. endurance training

  •    Intensity and duration of training

Primary signals leading to exercise-induced skeletal muscle adaptation

•   Primary signals responsible for exercise-induced adaptation

  •    Mechanical stretch (resistance training)

•   Calcium (endurance training)

  • Increase in ctyosolid calcium within a few seconds

  •   Calcium can trigger and activate other signaling pathways.

•    AMP/ATP (endurance training)

  •   Low at rest because of the abundance of ATP

  • During exercise the number increases 

• Free radicals (endurance training)

  •   Highly reactive molecules that cause DNA and protein damage.

Secondary messengers in skeletal muscle

•        AMP kinase (AMPK)

  • Important signaling molecules activated during endurance exercise; promotes glucose uptake and fatty acid oxidation.

  •     AMPK inhibits components of the mTOR signaling pathway

  • mTOR is main signaling pathway responsible for protein synthesis during resistance exercise.

  •    Induces PGC -1a;

  •    Promotes glucose and fatty acid oxidation.

•     Mitogen-activated kinase (p38)

  •    Important signaling for mitochondrial biogenesis.

•        PGC-1α

  • Master regulator of mitochondrial biogenesis; promotes angiogenesis (that is increased capillarization) and synthesis of antioxidant enzymes

  •    Activated by p38 and calmodulin-dependent kinases

Secondary messengers in skeletal muscle

• Calmodulin-dependent kinases (CaMK)

  • Activated by increases in cytosolic calcium-promotes activation of PGC-1α •

• Calcineurin (phosphatase: removes a phosphate group from molecules) •

  • Participates in numerous adaptive responses of muscle including fiber regeneration and a fast-to-slow shift in fiber type

  • Involved in shift of type 2 fibers to type 1 during endurance training

• Nuclear factor kappa B (NFκB)

  •   Activated by radicals-promotes synthesis of antioxidant enzymes

  • Promotes inflammation

•   mTOR

  •  Protein kinase-major regulator of protein synthesis and muscle size

Intracellular signaling in response to endurance exercise training

•     Why does NFkB lead to sytehesis of antioxidant enzymes?

  • Once you express NFkB you will start synthesizing anti-oxidants.

    •   Coping mechanism

Retraining and VO2max

-          Muscle mitochondria adapt […] to training

o    […] within 5 weeks of training

-          Mitochondrial adaptations lost quickly with detraining

o    Loss of 50% of training gain within 1 week of detraining 

o   Majority of adaptation lost in […] weeks

-           Requires 3–4 weeks of retraining to regain mitochondrial adaptations

• quickly

• Double

• two

Muscle adaptations to anaerobic training

•   […] exercise

  •  Refers to short-duration, very heavy or severe intensity exercise bouts

  •    Although standard definitions do not exist, two general types of high intensity exercise training are common

    • Sprint interval training (SIT)-severe exercise lasting 10-30s (>100% VO2 max)

    •   High-intensity interval training (HIIT)-very heavy exercise lasting 60- 240s (80 to 100% VO2 max)

•  […] training

  •   Mostly rely on ATP-PC system

  •  Energy to perform SIT primarily supplied by ATP-PC system and glycolysis

  • All out effort

•  […] training

  • Indicating for clinical population

  • Energy required to perform 60s of HIIT would be largely (approximately 70%) anaerobic sources (ATP-PC system/glycolysis) whereas remainder of energy would come from aerobic sources

  •   80-95% of HR max.

• […] training increases performance

  •   Sprint training improves muscle buffering capacity by increasing both intracellular buffers and hydrogen ion transporters

  • Sprint training also results in hypertrophy of type II muscle fibers and elevates enzymes involved in both the ATP-PC system and glycolysis

  •   High intensity interval training >60 seconds (at near or above VO2max) promotes mitochondrial biogenesis

  •   Mainly see hypertrophy in type 2 fibers.

• Anaerobic

• SIT

• HIIT

• Anaerobic