Bioenergetics and energy metabolism Flashcards
Metabolism
Chemical Reactions, pathways that result in synthesis or breakdown of molecules
Bioenergetics
Metabolic processes involved in converting food sources into biologically usable energy.
EE rises by around what from rest to exercise
15-25 x
VO2
ability to deliver and use oxygen
Physiological factors influencing VO2
- Delivery of oxygen to working muscles: Cardiorespiratory system
- Utilization of oxygen by working muscles: Metabolic system (Aerobic)
Two types of factors that influence O2 consumption
Central and Peripheral
Central Factors
Cardiac output which is:
Heart Rate
Stroke Volume (Training improves this)
Cardiac output = Heart Rate x Stroke Volume
Peripheral Factors
Extraction by tissues (a-vO2)
Oxygen carrying storage capacity & ability for cells to take O2 Training increases (3) -Capillary density -Mitochondria number -Hb, Mb
When exercising systemic changes happen because
Muscle demand increases force/speed of muscle contraction
- Rate of cross-bridge cycling
- Recruitment of motor units
- Recruitment of different fiber types
Increased in rate of energy system pathways are supported by: (3)
- Respiratory Changes: increase in ventilation
- Cardiovascular changes: increase in q (HR x SV)
Vasodilation in working muscle - Muscle Changes: increase Ca release/uptake by SR
Increase myoglobin shuttling
Order of Energy Systems starting up
Creatine phosphate (alactic)
Lactic (glycolysis)
lastly aerobic
When our cells have a choice of the three energy systems for ATP synthesis what is our go to system? Why?
Go to system always aerobic
Anaerobic lactic system
Involves glycolysis only
Takes place in cytoplasm- close to contractile unit of muscle
Safety valve for the aerobic energy system for when O2 isnt available or ATP is being demanded at a greater rate than the aerobic system can supply itself
CP-ATP system (Anaerobic Alactic)
CP in cell is 4-6X greater than ATP
CP is a high energy phosphate reservoir (last 8-12 seconds in an untrained individual, highly trained 15)
Crucial during transition from low to high energy demand.
Process of CP system
CP-> C+Pi+ Energy (Creatine Kinase enzyme)
ADP + Pi + Energy -> ATP (ATPase enzyme)
What is the power and capacity of each system
- Alactic: Highest power, lowest capacity (run out of creatine phosphate) need to resynthesize or cannot use energy system again
- In the middle
- Aerobic: lowest power, highest capacity
Power
Rate at which an energy system can produce ATP
Capacity
Total amount of ATP than an energy system can produce
O2 Deficit
Difference between oxygen uptake in the first few minutes of exercise and an equal time period after steady state has been obtained.
Factors contributing to excess post exercise oxygen consumption (6)
- Resynthesis of PC in muscle
- Lactate conversion to glucose
- Restoration of muscle and blood oxygen stores
- Elevated body temperature
- Post-exercise elevation of HR and Breathing
- Elevated Hormones
How we get CrP stores back
ATP -> ADP + Pi + Energy
——–>
C + Pi + Energy –> CP
Resynthesis of CP stores
15s - 68.7 %
60s - 81.0 %
180s - 92.0 %
For every second worked about 10-12 seconds of recovery is needed.
Control Systems during exercise
Demands for energy vs Supply of Energy
Energy Demand
How much energy is needed
What intensity is the muscle working
How long has the muscle been working at intensity (duration)
Energy Supply
What fuels are available
Can metabolic process supply ATP at a high enough rate
Short term high intensity =
Greater contribution of anaerobic energy systems
Long term, low to moderate intensity
Majority ATP produced aerobically
Energy Requirements at Rest
Almost 100% of ATP produced by aerobic metabolism Blood lactate levels are low Resting O2 consumption 0.25 L/min 3.5 ml/kg/min
Rest to Exercise Transitions
ATP production increases immediately
Oxygen uptake increases rapidly (Reaches steady state within 1-4 minutes)
Initial ATP production anaerobic
Oxygen deficit
Steady State reached means
ATP requirement is met through aerobic ATP production.
Trained subject have lower Oxygen Deficit why?
Better developed aerobic bioenergetic capacity
CVD and muscular adaptations
= Results in less production of lactate and H+
Recovery from Exercise
Oxygen uptake remains elevated above rest during recovery from exercise Oxygen debt (repayment for O2 deficit at onset of exercise) EPOC - terminology reflects only 20% elevated o2 consumption used to repay O2 deficit.
Rapid portion of O2 debt
- Resynthesizes stored PC
2. Replenshes muscle and blood O2 stores
Slow Portion of O2 debt
- Elevated heart rate and breathing= increases energy need
- Elevated body temperature= Increases in metabolic rate
- Elevated epinephrine and norepinephrine= Increase in metabolic rate
- Conversion of lactic acid to glucose (gluconeogenesis)
Why EPOC greater following high intensity exercise
- Higher body temperature
- Greater depletion of PC (additional 02 required for resynthesis)
- Greater blood concentrations of lactic acid (additional o2 required for greater level of gluconeogenesis)
- Higher levels of blood epinephrine and norepinephrine.
Removal of Lactic Acid following exercise
70% of lactic is oxidized by cells (Used as a substrate by heart and skeletal muscle)
20% converted to glucose
10% converted to amino acids
Lactic Acid removed more rapidly from blood if
Light exercise performed during recovery.
Optimal intensity is 30-40% VO2 max.
Metabolic Responses to Short Term High Intensity Exercise
First 1-5 Seconds of exercise: ATP produced via ATP-PC system
Intense exercise longer than 5s: Shift ATP production via glycolysis
Events lasting longer than 45 seconds: All three systems
60s: 70% anaerobic, 30% aerobic
120s: 50% anaerobic, 50% aerobic
Metabolic responses to prolonged exercise (>10 minutes)
ATP production primarily aerobic
Steady state O2 uptake maintained during submax exercise
Hot Humid environment or High intensity: Upward drift in O2 uptake over time from increase in body temp and increases blood levels of epinephrine and norepinephirne.
Lactate Threshold
Point at which blood lactic acid rises systematically during incremental exercise
Appears 50-60% VO2 max in untrained individuals
65-80% in trained subjects
Also called:
Anaerobic threshold
OBLA (When blood lactate levels reach 4 mmol/L)
Reasons for Lactate Threshold (4)
- Low muscle oxygen (hypoxia)
- Accelerated glycolysis: -NADH produced faster than it is shuttled into mitochondria
- Excess NADH in cytoplasm converts pyruvic acid to lactic acid. - Recruitment of fast twitch muscle fibers: LDH isozyme in fast fibers promotes lactic acid formation
- Reduced rate of lactate removal from the blood: Liver removes lactate from blood.
Practical Uses of Lactate Threshold
Prediction of Performance (Combined with exercise economy)
Planning training programs (marker of training intensity, choose a training HR based on LT)
