Thresholds and Domains Flashcards
Mastery
What does lactate formation consume
what does ATP hydrolysis produce
what does glucose and glycogen breakdown make
what does OXIDATIVE PHOSPHORYLATION produce
what does ANAEROBIC glycolysis produce
at high intensities what happens and how does the body compensate
it actually consumes protons, reducing acidosis
ATP hydrolysis produces protons
glucose and glycogen breakdown produces protons
OXIDATIVE PHOSPHORYLATION consumes protons
ANAEROBIC glycolysis produces protons
At high exercise intensities, H+ begin to accumulate
* The bicarbonate buffering system reduces [H+]. important for maintaining blood pH
GET and RCP related to…
Gas exchange
how is the first ventilatory threshold shown\
how is the second
LT1 to GET and LT2 to RCP
The first ventilatory threshold (gas exchange
threshold, GET) is identified as the first deviation
from the linear VE-VO2 relationship.
The second ventilatory threshold (respiratory
compensation point, RCP) triggers an even faster
increase in VE.
Lactate threshold
First ventilatory threshold
Gas exchange threshold
Anaerobic threshold
Respiratory compensation point
second ventilatory threshold
maximal lactate steady state
Maximal metabolic steady state
Critical intensity(Critical power or velocity)
- Lactate threshold: The intensity at which blood lactate begins to rise above resting levels during exercise.
- First ventilatory threshold: The point where ventilation starts to increase faster than oxygen uptake, indicating a shift in breathing response.
- Gas exchange threshold: Another term for the first ventilatory threshold, where CO₂ output begins to rise relative to oxygen uptake.
- Anaerobic threshold: The exercise intensity at which lactate accumulates rapidly, marking the transition to anaerobic energy systems.
- Respiratory compensation point: The point at which ventilation increases sharply due to rising CO₂ levels, often at high intensities.
- Second ventilatory threshold: The intensity where ventilation shows a rapid increase to compensate for lactate accumulation.
- Maximal lactate steady state: The highest intensity at which lactate production and clearance are balanced, allowing for a steady state.
- Maximal metabolic steady state: The maximum sustainable intensity where metabolic responses remain stable over time.
8.Critical intensity (critical power or velocity): The highest intensity at which exercise can be sustained without fatigue over an extended period.
During the moderate domain
excercise intensity
how much O2 muscles use
CO2 production and ventilation
lactate levels
fatigue
In moderate-intensity exercise, muscles use more oxygen, so less oxygen is left in exhaled air. CO₂ production and ventilation increase steadily, but blood lactate levels stay low, meaning the exercise is manageable without excessive fatigue.
During the heavy domain
lactate levels
how does the body buffer this
oxygen uptake
CO2 production and ventilation
if the steady state is reached
In the heavy domain, exercise intensity is high enough that some muscles produce more lactate than they can clear, causing blood lactate levels to rise slightly.
The body buffers this with bicarbonate, which increases CO₂ and ventilation.
Oxygen uptake still increases steadily, and, if steady-state is reached, lactate levels balance out without further accumulation.
The higher intensity leads to more lactate production, which generates more CO₂ as the body buffers the rising hydrogen ions. As a result, you breathe faster (higher ventilation) to get rid of the extra CO₂ produced during this process
during the severe domain
lactate production
what happens to minute ventilation
what happens to ventilation with O2 and CO2
[CO2] in exhaled breaths
RCP and expelling
the muscles produce more lactate than the body can clear, causing a rapid rise in blood lactate levels.
This results in a sharp increase in hydrogen ions (H⁺), which makes the body more acidic.
To compensate for this, the body increases breathing (ventilation) significantly.
At this point, ventilation increases faster than oxygen consumption and carbon dioxide production, leading to higher ratios of ventilation to oxygen consumption and ventilation to carbon dioxide production.
At the same time, the concentration of carbon dioxide in the exhaled air drops.
The respiratory compensation point helps the body by increasing breathing to expel excess carbon dioxide, which helps buffer the rising acidity and maintain a stable pH.
Maximum Lactate steady state
MLSS is the hardest intensity you can exercise at for a long time without lactate building up uncontrollably.
Power duration curve
Critical power
W’
T-lim
The Power-Duration Curve shows how much power you can maintain for different durations of exercise. It has a hyperbolic shape, meaning that as power increases, the time you can sustain it decreases.
Critical Power (CP) is the point that separates the heavy and severe exercise domains. It’s the highest power output you can sustain for a long period without fatigue increasing rapidly.
W’ represents the total amount of work (in joules) you can do above the critical power. This is the “extra” work you can perform before exhausting your energy reserves.
Tlim is the time limit you can sustain exercise above the critical power, calculated as W’ / (Power - CP). This formula tells you how long you can keep exercising at a power higher than your critical power, based on your available work capacity (W’).
Functional Threshold Power (FTP)
how can it be estimated
what is it similar to
Functional Threshold Power (FTP) is the highest power a cyclist can maintain for 60 minutes without tiring too quickly.
It’s often estimated as 95% of the average power from a 20-minute time trial.
Or, it can be 75% of the peak power in a ramp test where the intensity increases gradually.
FTP is similar to Maximal Lactate Steady State (MLSS), meaning it’s the highest power you can sustain without lactate building up too much.
Talk test
when can you talk
when can you not
Studies in a variety of populations, including healthy individuals, cardiac patients, and athletes, have demonstrated that the Talk Test is a good marker
of VT1.
- At an intensity level above VT1, but below VT2, an exerciser will still be able to speak, but not comfortably.
- At and above VT2 speaking becomes very labored and the exerciser can only utter a word or two at a time.
Below the critical threshold
Above the critical threshold
Below the critical threshold: All lactate produced will be used up by the body, and there’s no net anaerobic energy being used. Once the body reaches a steady state, it can keep going without too much fatigue.
Above the critical threshold: The body starts using more anaerobic energy, leading to the buildup of metabolites like lactate, inorganic phosphate (Pi), and hydrogen ions (H+). This causes fatigue and makes it harder to continue exercising.
In simple terms: Below the critical threshold, the body can handle lactate without it building up. Above the critical threshold, lactate and other substances accumulate, causing fatigue and limiting performance.
during severe exercise, why does fatigue happen
during heavy why does fatigue happen
during moderate, why does fatigue happen
what are the central factors
Severe intensity exercise:
Fatigue mainly happens because of disruptions in metabolism, like increased levels of inorganic phosphate (Pi), hydrogen ions (H+), and magnesium (Mg2+), and a decrease in ATP (the body’s energy source).
Heavy intensity exercise: Fatigue is caused by a mix of metabolic disruptions (like the ones above) and glycogen depletion (low energy stores in muscles).
Moderate intensity exercise: Fatigue is mostly due to glycogen depletion.
Central factors: The brain and nervous system can also contribute to fatigue at all intensity levels.
In short: Fatigue at severe intensities is mostly metabolic, at heavy intensities it’s a mix of metabolic problems and energy depletion, and at moderate intensities, it’s mostly due to running out of glycogen.
what are incremental tests performed for
what can they help inform
what does measuring blood lactate levels do
when does Threshold 1 and 2 usually occur
Incremental exercise tests are often performed:
1. To determine maximal aerobic capacity (V̇O2max)
2. To identify cardiorespiratory response thresholds
Both (1) and (2) are informative for exercise
prescription and to predict performance. As a % of HR max or % of VO2 max
Measuring blood lactate concentration helps gauge the metabolic stress of exercise.
Typically, LT1 is the point where lactate starts to rise above resting levels, marking the first noticeable shift. LT2 is where lactate levels begin to increase more rapidly, indicating a higher level of intensity.
what is threshold
depending on the intensity of the exercise what happens
what do thresholds separate( what 3 things)
A “threshold” is the point where a certain level of intensity must be reached to trigger a specific reaction or change in the body.
When ventilation or lactate levels change with increasing intensity. Responses like VO₂ or lactate can either stabilize or keep rising, depending on the intensity. This concept is used to identify key points like ventilatory and lactate thresholds.
thresholds separate different intensity zones called domains
Moderate, Heavy, Severe
during exercise what does the body adjust to
what drives breathing during rest
what drives breathing during excercise
During exercise, the body adjusts breathing to match its increased oxygen needs and CO₂ removal.
At rest, blood CO₂ levels (which affect blood pH) are the main driver for breathing
during exercise, multiple signals work together. These include not only changes in blood gases but also signals from the brain and feedback from muscles and joints, all helping to increase ventilation as exercise intensity rises.
