Exercise

• Figure 09.F02: Structure of Muscle. Muscle cells or fibers are wrapped in connective tissue and bundled together. The muscle attaches to the bone via the tendons.

Muscle Contraction

• Calcium-binding to troponin. Tropomyosin moves and exposes myosin-binding cite. You get the ATP from moving and bring it back to its place.
• Muscle Type 
• The difference in the rate of tension development is attributable to the expression of myosin ATPase isozymes
• Type I

• Red muscle
  • High in mitochondria
  • High capillary density
  • High in myoglobin
• Oxidative phosphorylate
  • FA
  • Pyruvate = enter mitochondria
• Endurance
• Type II(a)
  • Training effects
    • Endurance         type I
    • Strength & sprinting               type II(b)
• Type II(b)
  • White muscle
    • Low in mitochondria (low in oxygen)
    • Low in capillary density
    • Low in myoglobin
  • Very high glycolytic activity
  • Anaerobic
    • Power
    • Short-term - sprinting
    • Glycolysis

Muscle adaptation to Strength Training

• Muscle fiber hypertrophy from strength training
  • Increase in both type I and type II (increase more) muscle fibers
  • Augmentation of the number of myofibrils and supportive structural components
  • Increase in muscle protein synthesis
  • The decrease in muscle protein breakdown
• Gains in force
  • Muscle hypertrophy
  • Improved efficiency regarding muscle energy and physical systems
• Faster isoforms

• Muscle Adaptation to Endurance Exercise
• Metabolic adaptations increase the ability to oxidize fatty acids and conserve carbohydrates
  • Mitochondrial protein increases - in endurance training
  • Adaptation in  storage, transport, mobilization, and endogenous production of energy
• Cardiovascular adaptations
  • Increase in vascular density
  • Increase in muscle blood flow (high-intensity training)
  • Redistribution of blood flow within the active muscle

Respiratory Quotient

• RQ = CO₂/O₂
• CHO = 1
• Fat ~ 0.7
• Protein ~ 0.82
• The metabolic pathway used for en for work
  • Availability of fuel and O₂
  • Duration of activity
  • Conditioning or training

VO₂max

• Work intensity increases O₂uptake  
  • Intensity increases = increases oxygen. Breathing more.
  • The point at which an increase in the intensity of the exercise no longer results in an increase in the volume of O₂ taken up.
• Mitochondrial content increase (greater) > at higher training intensities. Muscle increases.
• Need longer time at lower VO₂ max to have the same increase in mitochondria
• Figure 9.10.0: Contribution to ATP During Early Exercise
•  Primary Energy Systems in Muscle and Their Involvement in Energy Expenditure Based on Time and Intensity

Hormonal Adaptation to Acute and Chronic Exercise

• Endocrine factors
  • Catecholamines:
    • Epinephrine - more potent than NE in muscle

Glycogen breakdown – stimulates

Muscle

Liver

Lipolysis – stimulates

Muscle

Adipose tissue

• Norepinephrine

Higher blood glucose decreases adrenal gland secretion

Lipolysis – Adipose tissues

• Insulin
  • Circulating levels decrease in high-intensity exercise
  • Exercise (high intensity) enhances insulin sensitivity
• Glucagon
  • Blood glucose driver of levels
  • Blood glucose drops = glucagon increases

Hormonal Adaptation to Acute and Chronic Exercise

• Increase during exercise
  • Cortisol
  • Growth hormone
  • Endorphins – increases for a better mood.

Energy Sources during Exercise

• Fuel sources during exercise
  • Muscle glycogen - energy
  • Plasma glucose – taken up
  • Plasma fatty acids – taken  up and coming from glycolysis
  • Intramuscular triacylglycerol

Energy Sources during Exercise

• Exercise intensity & duration
  • Low intensity
    • Plasma fatty acids
  • Moderate intensity
    • Increased fatty acid oxidation (due to muscle TG) (not used a lot) (hydrolysis of the muscle)
  • High intensity
    • CHO oxidation increases
    • Lactate production increases
• Level of exercise training
  • Training increases muscle glycogen & TG stores

• < 50% VO₂ max favor FA
  • insufficient blood flow to deliver FA from AT   to maintain FA oxidation
  • FA oxidation requires more O₂
  • FA transfer into mitochondria is slow due to carnitine

• 85 % VO₂ favor CHO

Endurance training

• Increases aerobic ability
  • Increase in size & # of mitochondria
  • Increase in cardiovascular capacity
  • Increase in lung capacity
  • Hypertrophy of Type I muscle
  • Increase in oxidative enzymes
  • Increased utilization of fat for en in sub-max ex
    • Spares glucose utilization in exercise
  • Increase capacity for muscle glycogen storage
• Hormone Response to Endurance Exercise

Carbohydrate Supplementation (Supercompensation)

• Classical regimen
  • 2 sessions of intense exercise, 2 days of the low-CHO diet, 3 days of high-CHO diet + rest
• Modified regimen
  • Exercise tapered over 5 days, 1 day of rest
  • 3 days of the 50%-CHO diet, then 3 days of the 70%-CHO diet

Protein

• Protein Recommendations
  • Resistance exercise
    • Eat soon after completion of the exercise

> 20 g protein

> 6 g essential amino acids

Augments muscle protein synthesis.

Carbohydrate increases insulin levels which decreases muscle protein breakdown.

• Prolonged endurance exercise
• AA supply 5- 10 % of energy
• BCAA N important
• for transamination of pyruvate
• carbon skeletons provide fuel
• The 0.8 g per kilogram body mass (RDA) represents a liberal requirement believed to be adequate for all people.
• A protein intake of between 1.4 and 2 g per kg of body mass or 15- 20 en %, should adequately meet the possibility for added protein needs during strenuous training.
• Individuals>50 years of age need more.
• Amino Acids
• Muscle
• BCAA
• Increased capacity to metabolize BCAA
• Increased branched-chain a-keto acid dehydrogenase (breakdown chained amino acid)
• Increased synthesis of glutamine
• Release glutamine and alanine during prolonged exercise
• Leucine
• Stimulates protein synthesis
• Milk just or more effective than BCAA formula