Bioenergetics

  • bioenergetics- flow of energy is a biological system

  • catabolism- breakdown of large molecules to small molecules

  • anabolism-synthesis of larger molecules from smaller

  • exergonic reaction-energy releasing action→ generally catabolic

  • endergonic-include all anabolic processes and contraction of muscles

    • converting macronutrients→ usable forms of energy

  • metabolism-total of all reactions

  • ATP adenosine triphosphate-allows transfer from catabolic to anabolic reaction

3 Basic energy systems

  • occur within our muscle cells

  • responsible for replenishing ATP

  • first two take place in the sarcoplasm

  • phosphagen system (anaerobic and anabolic)-short term, high intensity activities

    • active at the start of ALL exercise

    • type II fibers contain higher concentration of CP compared to type I (able to replenish ATP faster)

    • occurs in sarcoplasm

    • relies on the hydrolysis of ATP and the breakdown of creatine phosphate

    • stored ATP is not enough for exercise → rapidly replenished by phosphagen system

    • control of system based on law of masked action→ the products of the reactions are what drive these reactions to occur

  • glycolysis (anaerobic and anabolic)

    • the breakdown of CHO (carbohydrates) in order to synthesize ATP

    • glycogen stored by the muscle and by glucose stored in the

    • occurs in the sarcoplasm blood

    • requires multiple enzymatically catalyzed reactions

    • pyruvate can either be converted to lactate (fast glycolysis) or taken through the Kreb cycle through the liver

    • can be shuttled through the mitochondria (slow glycolysis) only if there’s enough oxygen in the mitochondria→ converted to Acetyl-CoA and enters the Kreb’s cycle

    • more likely to go through fast than slow glycolysis

  • oxidative system (catabolic and aerobic)- takes place in the mitochondria

    • pull primary source of ATP from different places

    • happens at rest and at low intensity

    • at rest-substrates (70% fats, 30% carbohydrates)

    • preference begins to shift as exercise occurs, increases carbohydrate dependence during exercise

    • gradual shift to fat during submax and steady state exercise

    • 90 min of exercise and long-term starvation-increased use of proteins

    • can occur with glucose/glycogen, fat and protein

    • glycolysis→pyruvate→mitochondria→AcetylCoA→ kreb cycle

    • free fatty acids→ mitochondria→beta oxidation→AcetylCoA→ kreb cycle

      • FFA come from triglycerides stored in fat cells and stored in muscle cells

  • protein oxidation

    • not a significant source of energy

    • protein broken down into amino acids

    • then converted to glucose, pyruvate or various kreb cycle intermediates to eventually yield ATP

  • lactate threshold- abrupt increase above baseline concentration

    • increased reliance on anaerobic mechanisms

    • begins around 50-60% VO2 max for untrained individuals and 70-80% VO2 max in trained individuals (allows athlete to exercise at higher intensity without the accumulation of lactate)

  • onset of blood lactate accumulation- second increase int he rate of lactate accumulation, occurs when 4 millimoles of lactate has accumulated

  • there is an inverse relationship between an energy system’s

    • max rate of ATP production

    • total ATP able to be produced overtime (capacity)

  • extent to which an energy system contributes to ATP production depends on

    • primarily- intensity of activity

    • secondary-the duration of the activity

Substrate Depletion and Repletion

  • depletion-intramuscular ATP largely sustained during exercise

    • we rely on creatine phosphate, which means we have depletion of CP 50-70% within 5 sec of high intensity exercise

    • almost eliminate CP with very high intensity exercise

  • post-exercise repletion

    • complete re-synthesis of ATP and CP within 8 minutes

  • glycogen

    • depletion related to exercise intensity

    • low intensity- liver glycogen

    • moderate and high- become more dependent on muscle glycogen; greater than 60% of VO2 max

    • post-exercise repletion related to CHO ingestion

    • 0.7-3g of CHO per kg body weight every two hours post exercise

  • O2 uptake (consumption)-measure of a person’s ability to uptake oxygen via the respiratory system

    • deliver O2 to working tissue via CV system

    • the ability of working tissue to use O2

    • increases the first few minutes until SS uptake occurs

    • slow to respond to increase in energy demand

    • O2 deficit-anaerobic system has to supply some energy

    • EPOC-makes of for oxygen deficit at beginning of exercise, indicated elevated metabolism post-exercise

      • post-exercise oxygen uptake

      • oxygen debt

      • intensity has the greatest influence on EPOC

      • combined high intensity and long duration gives greatest result; greater than 50-60 VO2 max; greater than 40 minutes

      • VO2 max- 207-0.7*age

      • heart rate reserve- %(age predicted HR max-HR rest)+ heart rate rest

      • resistance-heavy resistance training

    • factors responsible- O2 replenishment, ATP/CP resynthesis, increased body temp circulation and ventilation, increased rate of triglyceride fatty acid cycling, increase protein turnover, and change i energy efficiency during recovery

    • allows for selection of specific energy systems

    • more efficient and productive training programs for specific athletic events

Metabolic Specificity of Training

  • interval training

    • pre-determined intervals and rest periods

    • more training can be accomplished at higher intensities

    • high intensity interval training-brief, repeated bouts of high intensity exercise with intermittent recovery periods; causes cardiopulmonary, metabolic, and neuromotor adaptations; cumulative duration and intensity of portions-equals several minutes >90% VO2 max; most important factors-intensity and duration of active and recovery periods

  • combination training- adding aerobic endurance training to training of anaerobic athletes to enhance recovery

    • can be counterproductive for strength and power sports

    • could reduce maximum strength, gain in girth, anaerobic performing capacity, speed and power related performance