Nutrition Lecture 5
What is sometimes required for these enzymes?
Co-factors sometimes required (e.g. vitamins, minerals) ! modifiers might include: ATP, ADP, Ca, product of a reaction, etc
What is the crossover concept?
Describes the shift from fat to CHO metabolism as exercise intensity increases
primary fuel is what at Low-intensity exercise (<30% VO2max)
Fats are primary fuel
What are the different fuels that can be used for aerobic metabolism?
fat, cho, aa
what energy system is used for High-intensity, short-term exercise ~up to 15 s
most through ATP-CP system
what energy system is used for Intense exercise ~15-90 seconds
most via anaerobic glycolysis \ Aerobic gaining contribution
FATIGUE- Limits to Performance short term
! Short-term, max effort of ~15-120 s ! Energy supplied primarily by anaerobic glycolysis with some from ATP-PC system ! **H+ will accumulate and inhibit glycolysis plus ability of troponin to bind to calcium ! Phosphate & ADP build up ! CP depletion (especially if repeated) ! ?Change SR function
FATIGUE- Limits to Performance moderate, max effort ~3-60 mins
! 60-90% ATP from aerobic system ! limited by CV system ! Type IIa fiber distribution ! H+ accumulation (lactate) with shorter events
Longer Exercise Duration and Fuel Selection
! Almost all ATP from aerobic system ! During prolonged exercise there is a shift from CHO metabolism toward fat metabolism
What does endurance training do to fuel utilization?
! INTENSITY: Increased use of fat at most exercise intensities ! DURATION: Switch to fat more rapidly when keeping exercise intensity constant
Phosphagen (ATP-PC system)
! Immediate source of ATP PC + ADP ATP + C Creatine kinase Quick but low capacity
Anaerobic systems use what 2 energy systems?
- ATP-CP (Phosphagen): ATP,CP -Anaerobic glycolysis: blood glucose, glycogen
What are sources of carbohydrate during exercise?
- Blood glucose - Muscle glycogen
What is electron transport system?
- Electrons removed from NADH and FADH are passed along a series of carriers to produce ATP (Oxidative phosphorylation) -H+ from NADH and FADH are accepted by O2 to form water
How can nutrition influence any of this? Potential goals:
! Increase amount of fuel stored at start ! Provide exogenous fuel during exercise ! Push use of one fuel over another and thus reduce rate of depletion ! Reduce build up of fatigue-inducing factors ! Prevent deterioration in physiology and increased body temperature that goes along with dehydration ! Maintain immune function and prevent excessive inflammation ! Enhance recovery of fuel stores and (maybe) reduce damage after exercise
Energy (calorie) & fuel use for an exercise bout can be predicted from:
! Intensity/pace ! Body weight (unless BW supported) ! Duration ! Frequency ! Training status of the athlete
What could be limiting factor for exercise performance?
-Depletion/substantial reduction stored fuels -Reduction in blood glucose -CNS fatigue -Muscle structural damage -SR dysfunction -Inadequate oxygen provision -Build up of something that reduces ATP production rate...i.e. enzyme impairment -Hyperthermia -Dehydration
What are sources of fat during exercise?
-Plasma FFA (from adipose tissue lipolysis) - Intramuscular triglycerides
how do produce ATP as efficiently as possible?
-That means when possible will break down fat with aerobic metabolism -But not always possible as rate of ATP production is slowest with aerobic metabolism so when need rapid ATP generation must use one or both of anaerobic systems.... that means carbohydrate use
RER for Fat (Palmitate)
0.70
RER for Carbohydrate (Glucose)
1.00
muscle contraction depends on what?
ATP availability
FATIGUE- Limits to Performance, ! Long-term, max effort ~1-4 hours
Almost all aerobic so high VO2max, economy, and Type I fibers important ! Ability of maintain blood glucose ! Initial muscle/liver glycogen ! Liver ability to supply glucose to muscle (break down glycogen and gluconeogenesis) ! Carbohydrate ingestion ! Dehydration
primary fuel at High-intensity exercise (>70% VO2max)
CHO are primary fuel
With aerobic metabolism, pyruvate converted to AcCoA which enters what?
Enter Kreb's cycle (TCA cycle) -Produces NADH & FADH2 (for later conversion to ATP) -Produces some ATP directly
Avoid beginning dehydrated or depleted of glycogen.
Exogenous carbohydrate & fluids maybe ergogenic in some circumstances, especially if very high intensity efforts interspersed
How does production of lactic acid occur?
In anaerobic metabolism, H+ and electrons from NADH are accepted by pyruvic acid to form lactic acid
Fatigue & Exercise metabolism review
In order to understand fuel intake needs (i.e. nutrition), need to understand what is being used for various activities/sports
what two things should we be matching for energy demands?
Need to match (as close as possible) ATP need with ATP production ! Want to produce ATP as efficiently as possible and with fuel have in abundance
What are sources of protein during exercise?
Only a small contribution to total energy production (only ~2%) ! May increase to 5-15% late in prolonged exercise
FATIGUE- Limits to Performance
Single effort < 10 seconds (e.g. shot put, high jump, 50-100 m sprints) ! Type II motor units are recruited (so performance is limited by person's fiber distribution) ! Reduction in CP & rate of ATP generation ! Accumulation of ADP, P
[ATP] will fuel about 2 s of maximal effort
So, need tremendous ability to regenerate ATP If ATP drops, cannot generate same work rate (fatigue)
what is RER, respiratory exchange ratio?
VCO2/VO2
how can nutrition help with fatigue?
Very little you can do nutritionally to influence very brief, very intense exercise unless good nutrition adds to training adaptations to help boost muscle size & power gain over time
why is lactic acid not produced in aerobic metabolism?
With aerobic metabolism, O2 is available in the mitochondria to accept H+ (and electrons) from NADH produced in glycolysis
Glycolysis has to phases which are
energy investment energy generation
what exercise is most likely to be influenced by nutrition?
exercise 1-4 h
Aerobic systems uses what fuels?
glycogen, glucose, and fats
fatigue
inability to maintain performance
What are 3 systems to generate ATP
phosphagen system ( ATP-PC system) anaerobic glycolysis aerobic system
energy for Exercise longer than ~2-3 minutes
primarily from aerobic metabolism ! Some contribution from anaerobic depending on how long
how are these processes controlled?
rate limiting enzymes
what do rate limiting enzymes do?
regulate (stimulate or inhibit) the rate of a metabolic reaction
How do we measure fuel use?
• Measures expired air volume and content of oxygen & CO2 • Calculate VO2 & VCO2, RER • Can calculate kcal and fat/carbohydrate used