Lecture 14 - Exercise Thresholds

Question 1

what is lactate concentration?

Answer 1

• when an increase in lactate in the body has an acidifying effect
• increase in H/decrease in pH

Question 2

what are buffering protons?

Answer 2

• bicarbonate (HCO3-) combines with H to form water and carbon dioxide
• prevents an increase in H concentration, aka maintains normal pH
• a reversible reaction

Question 3

what is CO2 production and breathing?

Answer 3

• ventilation keeps CO2 from accumulating
• drives the carbonic anhydrase reaction
• produces CO2 and consumes H
• aka we breath out acid

Question 4

what are the 2 metabolic boundaries?

Answer 4

• Lactate threshold (LT)
• critical intensity (CI)

Question 5

what is lactate threshold?

Answer 5

• the highest metabolic rate (or VO2) at which blood lactate can be maintained at resting levels
• separates moderate from heavy intensity exercise domains

Question 6

what is critical intensity (or max metabolic steady-state)?

Answer 6

• the highest VO2 at which a heightened lactate production in muscle may be stabilized in blood
• separates heavy from severe intensity exercise domains

Question 7

what is moderate-intensity exercise?

Answer 7

• anything below the lactate threshold
• only occurs if oxygen is present
• in hypernea
• blood lactate remains the same as during rest

Question 8

what is heavy-intensity exercise?

Answer 8

• above the lactate threshold, but below the critical intensity
• higher ATP demand
• higher rate of reaction
• more substrates
• includes pyruvate and bicarbonate reactions
• more CO2 lost than O2 uptaken
• prioritize dealing with CO2 > getting more O2 (aka increase breathing to lose CO2, despite slower breathing being better for O2 uptake)
• blood lactate level increases (but can be dealt with using other systems)
• lactate production is still equal to lactate disappearance
• still in hypernea

Question 9

what is severe-intensity exercise?

Answer 9

• above the critical intensity
• more substrates, more ATP, etc.
• buffering is no longer sufficient (causing lactate build-up)
• use stored PCr
• hyperventilate to get rid of additional CO2
• contains RCP ( respiratory compensation point)
• become acidotic
• lactate appearance is greater than lactate disappearance
• an overflow of lactate causing cramping etc.
• past hyperpnea (into hyperventilation)

Question 10

what are the 2 metabolic thresholds?

Answer 10

• GET/VT1
• RCP/VT2

Question 11

what is GET/VT1?

Answer 11

• the VO2 at the onset of bicarbonate buffering where CO2 and Ve begin to increase at a greater rate than VO2
• approximately equal to LT
• separates moderate and heavy intensity exercise domains

Question 12

what is RCP/VT2?

Answer 12

• the VO2 at which bicarbonate buffering cannot prevent acidosis and hyperventilation ensues to compensate
• approximately equal to CI
• separates heavy and severe intensity exercise domains

Question 13

how does LT and CI vary by sex?

Answer 13

• females LT and CI are generally at a higher VO2 max % than males
• therefore this means females are closer to their VO2 max at each metabolic threshold
• this is likely because females bodies tend to be smaller, therefore they cannot undergo the processes as efficiently as males