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