KIN 3515 EXAM 3 LSU GUILLAUME SPIELMANN

Other Names for The Lactate Threshold

Aerobic threshold, Lactate breakpoint, onset of blood lactate accumulation (OBLA), maximal steady rate

What is the lactate threshold?

-an index of the contribution of aerobic and anaerobic energy systems to energy expenditure

-Most athletes train at or slightly above the lactate threshold (varies markedly by sport)

-The best physiological indicator of aerobic athletic performance

Why is the blood lactate threshold important?

What causes the blood lactate threshold?

Is the blood lactate threshold related to the "ventilatory threshold?"

Blood lactate threshold is the aerobic threshold and the ventilatory threshold is the anaerobic threshold, the ventilatory threshold occurs about the same time BL begins to accumulate

Other Name for Oxygen Debt

Elevated Post Exercise O2 consumption (EPOC)

What is the oxygen debt?

the amount of extra oxygen required by muscle tissue during recovery from vigorous exercise, the difference between the amount of oxygen required after strong muscular activity and the amount required in a resting state

What causes the oxygen debt?

Oxygen debt occurs when the body reaches a state of anaerobic respiration during intense exercise. When a person engages in high levels of physical activity, the body cannot distribute oxygen to the cells at a sufficiently rapid pace to keep up with the oxygen demand

What does the oxygen debt have to do with the restoration of muscle CrP, ATP and glycogen?

muscle glycogen must also be restored

Measurement of energy expenditure

direct calorimetry and indirect calorimetry

What is the daily energy expenditure?

basal metabolic rate + physical activity+ diet induced thermogenesis

What is diet-induced thermogenesis?

after the ingestion of food, our metabolic rate increases because energy is required to digest, absorb, distribute, and store nutrients

What causes fatigue?

What does the wingate test measure?

peak anaerobic power, anaerobic fatigue and total anaerobic capacity

What is the Wingate test?

All out pedaling for 30 seconds at various resistance (between 45g/kg for adults to 90g/kg for athletes (pre-draft)

When was the Wingate test developed?

70s

Anaerobic capacity tests besides Wingate test:

Sprint test, FIFA interval tests, beep tests

What is a VO2 max?

A maximum rate at which an individual can consume O2 during maximal exertion

How is VO2 max expressed?

Expressed as the maximum volume of oxygen consumed/min

Absolute measurement of VO2 max

litres per min (L/min)

Relative measurement of VO2 max

milliliters per kilogram per minute (ml/kg/min)

What is 1 MET? What is the measurement?

metabolic equivalent = A unit used to estimate the metabolic cost oxygen consumption) of physical activity = 3.6 ml O2/kg/min

How is VO2 Consumption assessed?

By collecting expired air

Two tangible ways to assess VO2 consumption

Douglass bags and metabolic cart

What does a higher VO2 max generally mean?

increased aerobic performance

What does VO2 increase in response so?

exercise stress and training

Defect of VO2 max

Not the best indicator of athletic performance potential

What is a Douglas bag?

an inflatable bag used to collect expired air for the determination of oxygen consumption and basal metabolic rate

What do you do during the Bruce test?

3 minutes interval with increases in speed and incline

What is the Bruce test?

Used to monitor cardiac function in exercising patients (also called "Stress test")

Why is the Bruce test used?

Used by coaches and exercise physiologist to determine V02max in runners

How is VO2max measured?

often measured by indirect calorimetry as a global index of aerobic fitness

Blood lactate concentration

an index of anaerobic metabolism, not anaerobic power

Lactic acid formed in...due to....

resting skeletal muscle due to breakdown of blood glucose

Evenly Aerobic

Lactic acid removal matches its production

Unevenly Aerobic

Lactic acid production exceeds its removal capacities

Lactate dehydrogenase (LDH) function

reduces pyruvate to lactate within the cytosol

Lactic Acid metabolism formula

Pyruvate + NADH + H+ {LDH} Lactate + NAD+

What does an acidic environment result in?

Fatigue

Does lactic acid cause fatigue?

No

What causes fatigue?

•Lactic acid does not cause fatigue! Fatigue occurs due to the acidosis that accompanies lactate production!

Benefits of lactic acid

1) Benefits muscle metabolism during high-intensity exercise and 2) Lactate becomes an energy source

How does lactic acid benefit muscle metabolism during high-intensity exercise?

Allows the cytosolic redox potential to be maintained thus allowing glycolysis to continue

How does lactic acid become an energy source?

~20% of lactate produced during exercise is taken up by the liver and converted into glucose (Cori Cycle) and The "Lactate Shuttle" concept

•Onset of Blood Lactate Accumulation (OBLA):

-The VO2 observed during incremental exercise associated with a BL concentration of 4mM

-Also called: Anaerobic Threshold

•Maximal Steady State (MSS):

-highest VO2 maintained over time without continual increase in BL accumulation (MSS)

-Also called: Individual Anaerobic Threshold (IAT)

The VO2 is a predictor of...

the ability to performance endurance exercise, but not a great one

Ventilatory breakpoint

disproportionate rise in ventilation relative to the increase in O2 consumption

The Lactate Threshold is the best predictor of

the ability to performance endurance exercise

People with McArdle's disease have NO

muscle phosphorylase

6 Determinants of the lactate threshold

Muscle fiber composition, number of capillaries, type of LDH enzyme, amount of mitochondrial enzymes, size of mitochondria, sympatho-adrenal activity

What is fatigue?

Decreased performance and sensation of tiredness

Fatigue from exercise lasting <15 seconds:

-phosphagens supply the majority of energy

-may be an inability to make ATP fast enough to keep up with the increased breakdown by the myosin cross bridges

Fatigue from Exercise lasting from 15 secs to several minutes

•major sources of energy are the phosphagen, lactic acid systems

•substrate availability is not a problem

•acid base balance disturbances (i.e., H+) most likely cause of fatigue

•electrolyte disturbances (K+ loss)

Fatigue from exercise lasting several hours

•hypoglycemia

•depletion of muscle glycogen

•hyperthermia/dehydration

Why does glycogen depletion coincide with fatigue when there is plenty of FFA?

We don't know. "Fat burns in a Carbohydrate Fire"

The maintenance of Kreb's Cycle intermediates necessary to break- down FFA requires glycogen.

What leaves the muscle during contractions?

Potassium (K+)

Determinants of Sprint performance

phosphagen power, glycolytic power, buffer capacity, technique

Determinants of endurance performance

lactate threshold, VO2 max, efficiency

When does a VO2 max plateau during training?

6-8 weeks, but the subject will continue to increase his ability to exercise at a higher percentage

Training for 6-12 months will cause:

-a rightward shift of the LT

-Race pace is normally close to the LT

-Thus, a trained individual can perform at a faster pace

_______________ concentration __________ at a given submaximal workload after training

Blood lactate, decreases

Main buffers of lactic acid:

- blood = bicarbonate

- muscle = phosphates

Muscle buffering capacity increases up to _________ after ________ weeks of anaerobic training

50%, 8

An increase in buffering delays fatigue because it attenuates the release of ____________

H+ ions

Why is there so much confusion surrounding ventilatory, lactate, and anaerobic threshold?

-There are various terminologies used to describe a similar phenomena and lots of debate surrounding these terms

-Which blood lactate concentration is taken as being equivalent to Lactate threshold differs amongst researchers

-Important to understand how a researcher has identified the lactate/anaerobic/ventilatory threshold before interpreting the data

-The usefulness of the concept in practice (regardless of which ever term is used) is not disputed

During short term cycling, muscle Creatine Phosphate...

drops rapidly during the first two minutes, and then declines more slowly.

Complete restoration of CP contents occurs

within 3 minutes

Phosphagen Resynthesis After Exercise Requires

O2

The rapid (3-5 min) recovery of ATP and CrP is prevented when

blood flow to the exercised muscle is prevented

In contrast to the rapid recovery of the _________________, the return of muscle pH back to resting levels is much slower, requiring

phosphagen system, 30 minutes

How much recovery time is required to remove one-half of the blood & muscle lactate?

25 minutes

How much blood & muscle lactate is removed after 75 minutes of recovery time?

95%

To remove lactate from the blood, the optimal recovery intensity is____________

30-45% of VO2max

Oxygen deficit

Beginning of Exercise, Exercise Transitions

Lactate Production

High intensity exercise

Excess post-exercise Oxygen consumption (EPOC)

End of Exercise

How long does it take for the VO2 to reach a new steady state at the beginning of exercise? What is this apart of?

3-5 mins, O2 deficit

What does the O2 deficit accumulate and why?

ADP to stimulate cellular respiration

What is Excess Post Exercise Oxygen Consumption (EPOC)?

This is the excess oxygen consumed following exercise which is needed to replace ATP which has been used up and to remove lactic acid created during the previous exercise.

Other Possible Explanations for EPOC

•Reform ATP, PC, and replace tissue O2 stores.

•Removal of Lactic Acid [to liver (Cori Cycle) or Oxidation]

•Replenish Glycogen Stores

•Removal of excess CO2

•Increase Body Temp and Catecholamines

The rapid (3-5 min) recovery of ATP and CrP is prevented when

blood flow to the exercised muscle is prevented.

The rapid (3-5 min) recovery of ATP and CrP is related to

to the amount of extra O2 consumed

There is a correlation between the amount of lactate removed during exercise and

the slow phase of the EPOC

This it is not a particularly strong relationship

Is the Slow Component of the EPOCRelated to Removal of Lactate?

Traditional View:

•20% Oxidized

•80% to Cori Cycle or to Glycogen

Most lactate (~65%) made during exercise is

oxidized

Smaller amount of lactate (~20%) made during exercise is is converted to

Cori Cycle and glycogen

What do the smallest amounts of lactate made during exercise go to?

Protein (8%) and as Lactate + Glucose (3%).

McArdle's patients make no

No Lactate, But Have a Slow EPOC

Causes of the slow "Lactacid" component of EPOC

Elevated HR and breathing, Elevated FFA, Elevated hormones EPI, NOREPI thyroid, lactate removal, elevated body temperature ions redistributed in muscle

What is happening during EPOC?

the body is restoring to its pre-exercise state, consuming O2 at an elevated rate

Specific functions of EPOC:

•Replenishment of Energy supplies (Phosphagen System) + Lactate oxidation

•Re-oxygenation of Blood and restoration of Circulatory Hormones

•Decrease in Body Temperature

•Return to Normal Ventilation and Heart Rate

What is basal metabolic rate (BMR)?

Minimal level of energy needed to sustain bodily functions

Factors affecting BMR:

•Body mass

•Regular exercise

•Diet-induced thermogenesis

•Environment

Complete resynthesis requires:

1) high intake of CHO, and

2) at least 2 days.

The main purpose of post-exercise CHO consumption is

•to replenish depleted stores of muscle and liver glycogen

•Rate of glycogen synthesis depends on:

-Activity of enzymes such as glycogen synthase

-The transport of glucose into the cell (Influenced by muscle glycogen concentration and insulin)

•Two phases distinguished in the process of glycogen synthesis after exercise

-1. Initial insulin independent (Rapid Phase)

-2. Insulin dependent (Slow Phase)

Depletion can be minimized by

consuming a greater amount of carbohydrate in the diet

Significant amounts of liver glycogen are used during exercise which may result in

hypoglycemia