Lactate - friend or foe Flashcards
What role does lactic acid play in muscle fatigue?
traditional views
Traditionally viewed as a cause of muscle fatigue and exercise performance limitation.
How is lactic acid traditionally classified in metabolism?
Considered a waste product of anaerobic metabolism.
What effects is lactic acid believed to have during intense exercise?
Causes “burn,” metabolic acidosis, decreased muscle contractility, and exercise cessation.
What was lactic acidosis believed to impair in muscles?
Muscle contractility leading to fatigue and exhaustion.
What was lactic acid believed to cause in muscles?
Uncomfortable feelings and delayed-onset muscle soreness.
<p>What is the likely source of proton (H+) release in glycolysis?</p>
Non-mitochondrial hydrolysis of adenosine triphosphate (ATP).
<p>T/F lactic acid is produced in muscle</p>
<p>False</p>
What triggers the conversion of pyruvate to lactate during exercise?
<p>Increasing concentrations of pyruvate due to the mitochondria being unable to oxidize all the pyruvate<br></br></p>
Which enzyme converts pyruvate to lactate?
Lactate dehydrogenase.
What do Robergs et al argue is the source of H+?
Non-mitochondrial ATP turnover is the source of H+.
What do Lindinger et al propose about strong acid anions during glycolysis?
They necessitate an increase in net positive charge to maintain electroneutrality.
How is the positive charge primarily provided during increased glycolytic activity?
By the dissociation of water.
What are some beneficial effects of acidosis?
Greater oxygen release, ventilatory stimulation, enhanced blood flow, increased cardiovascular drive.
What misconception is related to lactate and muscular fatigue?
Acidosis is a primary cause of muscular fatigue and exercise cessation.
What have recent studies shown about acidosis and muscle contraction?
Limited effects on skeletal muscle contraction from induced acidosis.
What is lactate’s role in metabolism?
Lactate is a fuel and signaling molecule, not just a waste product.
What facilitates lactate transport in cells?
Monocarboxylate transport proteins (MCTs).
Lactate can be shuttled out of the cell via what?
An MCT, possibly with extracellular H+ transport.
What effect do elevated blood lactate levels have on energy substrate utilization?
They downregulate the use of glucose and free fatty acids as energy substrates.
What happens to blood lactate levels at the start of exercise?
Blood lactate levels increase slightly.
What triggers glycolysis during exercise?
An increase in ATP demand by working muscles.
Why is there an initial rise in blood lactate during exercise?
Inadequate heart rate and capillary dilatation delay oxygen delivery.
What factors contribute to increased blood lactate levels?
<ul><li><p>Oxygen delivery</p></li><li><p>mitochondrial capacity</p></li><li><p>lactate clearance/utilization by body cells.</p></li></ul>
What is the first difficulty in using lactate threshold as a training aid?
Confusion in terminology regarding lactate threshold and related terms.
List terms often used interchangeably with “lactate threshold.”
<ul><li><p>Anaerobic threshold</p></li><li><p>aerobic threshold</p></li><li><p>lactate turn point</p></li><li><p>OBLA</p></li><li><p>MLSS</p></li></ul>
What is the “onset of blood lactate accumulation” (OBLA)?
Point where blood lactate begins to increase above resting values during exercise.
What does “maximal lactate steady state” (MLSS) refer to?
Maximal exercise intensity where continuous blood lactate increase is unavoidable.
What is a potential limiting factor in lactate threshold testing and training?
Accuracy of measurement.
What type of exercise increases lactate threshold in sedentary subjects?
Any training stimulus, including very light exercise.
What is necessary to increase lactate threshold in well-conditioned athletes?
Very intense exercise.
How trainable is VO2max according to the meta-analysis?
VO2max is minimally trainable.
What is as effective as lab-measured blood lactate levels for determining training zones in runners?
Rate of perceived exertion
What is critical velocity closely correlated with?
Power and velocity at MLSS and OBLA.
What training plans have cyclists and runners transitioned to?
Plans based on critical pace or functional threshold power.
What does “critical pace” or “critical power” describe?
Maximal workload over a given time or distance.
What role does the lactate dehydrogenase reaction play in glycolysis?
It maintains cytosolic redox potential and buffers against acidosis.
<p>How does the lactate dehydrogenase reaction help buffer against acidosis?</p>
It consumes a proton, effectively buffering against acidosis.
Lactate transport into mitochondria serves what purpose?
To be oxidized.
What is coupled with lactate transport into peroxisomes?
Reoxidation of NADH, required for B-oxidation.
What is lactate uptake dependent on?
Lactate uptake is dependent on concentration gradients.
<p>Which 2 factors make lactate a preferential energy source in some situations?</p>
<ul><li><p>uptake is dependent on concentration gradients and is not limited by transport</p></li><li><p>lactate to pyruvate oxidation is fast and therefore not limiting</p></li></ul>
What did Zuniga et al [17] demonstrate about analyzing blood lactate curves?
They demonstrated that testing protocols affect OBLA and MLSS estimates more than analysis methods.
Glycogen status affects what aspect of lactate testing?
Blood lactate curve interpretation.
The absolute value of blood lactate at MLSS predicts performance on endurance tasks.
False, it does not predict performance on endurance tasks.
What strongly predicts performance at MLSS?
The workload at MLSS.
Is workload at MLSS correlated with absolute blood lactate levels?
No, it is not correlated.
<p>what is the main advantage a profession has over an amateur even if they have similar VO2max?</p>
<p>the ability to maintain high workloads without high lactate concentrations in their blood</p>
