7.Energy Pathways

CATEGORY:

•Energy Pathways

DEFINITION:

•Three systems that are utilised in conjunction to provide energy to skeletal muscle

FUNCTION:

•ATP (Adenosine Triphosphate) & PC (Phosphocreatine) combine with or without Oxygen as the primary source of energy

ACTION:

•Anaerobic Alactic...employed where the energy need is short and intense...10-15secs (ATP 5-7secs + PC 5-8secs)

•Anaerobic Lactic...responds to demands of 10-90secs

•Aerobic...primary source of ATP at rest and endurance...90+secs

FACTS:

•All 3 pathways active at the same time, but dominance depends on intensity and duration 

MANIPULATION:

•Only Carbs can be metabolised in both Anaerobic and Aerobic Pathways

•Carbs & Fat and eventually Protein (sourced from muscles) utilised in Aerobic Pathway

•Four sources of energy...

-Body fats (Adipose)

-Fats within muscle tissue (Triglycerides)

-Glucose from liver Glycogen

-Glucose from muscle Glycogen

DIETING:

•At rest Fat contributes 70% of energy needs...Carbs 30% - shift occurs as intensity increases

•Burning ratio during exercise or aerobic activity is 20% Fat to 80% Glucose

•During Fasting metabolism (sleep), reversed to 20% Glucose and 80% Fats

•Carbohydrates, Proteins, and Fats are digested in the intestine and broken down into their basic units...

-Carbohydrates into Sugars

-Proteins into Amino Acids

-Fats into Fatty Acids and Glycerol (converted to Glucose or Glycogen)

—Body uses these basic units to build substances needed for growth, maintenance, and activity

RELATED TO:

•Glucose

•Glycogen

•Macro Nutrients

ANAEROBIC ALACTIC:-

•Without Oxygen and does not produce Lactic Acid

•Used in first few seconds of exercise regardless of intensity

•Energy metabolism occurs in sarcoplasm of muscle cell

•Phosphocreatine used to re-form ATP (ATP-PC Cycle) by combining with ADP (spent form of ATP)

•ATP-PC Cycle requires 2mins rest to replenish stores of ATP & PC

•Train the system by having adequate rest....power training (if rest is reduced it becomes endurance training)

-Ratio of 1:10/12...every second of intense exercise (up to 15secs) requires 10/12secs recovery

-Training session ends when power and precision of movements declines

•If activity continues at a high intensity, stores only partially replenish as not enough energy available for Creatine and Pi to reform PC...rate of ATP breakdown through other energy systems will impede the replenishment of ATP stores in the muscle

•Fuel sources...

-Protein 1.2-1.8g/kg body weight for athletes...

—Amino Acids used to create enzymes for splitting Phosphocreatine in to Phosphate and Creatine for ATP re-synthesis

-Carbs 1.5g/kg body weight for athletes

ANAEROBIC LACTIC:-

•Without Oxygen and produces Lactic Acid

•Aka Anaerobic Glycolitic/Fast Glycolysis

•Energy metabolism occurs in sarcoplasm of muscle cell

AEROBIC:-

•With Oxygen

•Aka Oxidative/Slow Glycolysis/Krebs/Citric Acid

•Energy metabolism occurs in mitochondria 

•Phosphocreatine stores replenished as not used during Aerobic activity and Homeostasis

•Carbs and Fat are primary sources of energy converted to ATP...Protein only used after 90mins exercise and during starvation - leading to muscle catabolism

-Fat becomes primary source after 3mins, dependent on amount of Oxygen in blood

•If Oxygen present Pryuvate (end product of Glycolysis) is shuttled to mitochondria to initiate Aerobic Pathway...ADP converted to ATP yielding 38 ATP molecules from 1 Glucose mol

-Stored Fat from Free Fatty Acids also used to produce ATP

Training:-

•All exercise begins with Anaerobic Pathways

•After 3mins Oxygen Deficit occurs...heavy breathing initiated to replenish Oxygen - if OD is too high then Anaerobic Pathways continue to be utilised leading to fatigue

•High duration low intensity builds up Aerobic/Oxidative capacity and VO2 Max

•HIIT trains recovery by ability to decrease Lactate levels in blood and greater capacity for Oxygen replenishment and ATP-PC Cycle

Ketones:-

•Useable form of Fat for energy...Medium Chain Triglycerides e.g Coconut Oil...half of Fats are MTC

•Shuttled to Liver and converted to Ketones to be immediately used by cells

•Depletion of muscle Glycogen is spared

•Ketones can be utilised by the Brain for energy in the absence of other sources

Pyruvate:-

•Key intermediate in Metabolic Pathways supplying energy during Aerobic exercise

•Made from Glucose via Glycolysis, converts to Carbs (Glucose) via Gluconeogenesis, or to Fatty Acids

•If Oxygen not present it is converted to Lactate

•Used to construct the Amino Acid Alanine to be converted to Lactic Acid

Lactate:-

•Interchangeable term with Lactic Acid - they are different things but heavily linked

•Produced from Pyruvate during normal metabolism and exercise 

•Does not increase in concentration until production exceeds removal...governed by Oxidative capacity of tissues

•Can be...

-Oxidated back to Pyruvate by well-oxygenated muscles, heart and brain...Pyruvate then used in Aerobic exercise 

-Converted to Glucose via Gluconeogenesis in Liver and released into circulation...if Blood Glucose concentrations high, the Glucose is used to build up Liver Glycogen stores

NOTES:

•Glycogen converted back to Glucose for use during exercise...why ingesting Hi-GI Carbs supplies body with immediate supply of useable Glucose, bypassing Glycogen Stores