I don't understand Lactate Threshold

I like metabolism wrote:

I've typically seen anaerobic threshold and lactate threshold as synonymous terms in scientific literature. Some textbooks prefer the term OBLA (onset of blood lactate accumulation) as it is the most accurate descriptor. I've seen the anerobic threshold somewhat inaccurately described as the point at which our bodies shift from aerobic to anaerobic metabolism, but that's not quite right, as we don't just flip a switch, with aerobic turning off and anaerobic turning on. It's more like a dimmer switch... And we don't really every turn off either system. At rest, we have a measurable blood lactate level. And at VO2 max, we are optimizing both systems (a lactate level above 8 mmol and a high RER are both indicative of anaerobic contributions to energy production, and these are criteria used to determine if it is a true VO2 max effort).

Regarding lactate vs lactic acid, they are often used interchangably because we produce lactic acid, but it immediately dissociates into lactate and a hydrogen ion. The lactate isn't the issue, as it is simply a substrate that can be converted back to pyruvate for fuel at rest or low intensity... it is the hydrogen ion that results in pain and fatigue

I like metabolism wrote:

I've typically seen anaerobic threshold and lactate threshold as synonymous terms in scientific literature. Some textbooks prefer the term OBLA (onset of blood lactate accumulation) as it is the most accurate descriptor. I've seen the anerobic threshold somewhat inaccurately described as the point at which our bodies shift from aerobic to anaerobic metabolism, but that's not quite right, as we don't just flip a switch, with aerobic turning off and anaerobic turning on. It's more like a dimmer switch... And we don't really every turn off either system. At rest, we have a measurable blood lactate level. And at VO2 max, we are optimizing both systems (a lactate level above 8 mmol and a high RER are both indicative of anaerobic contributions to energy production, and these are criteria used to determine if it is a true VO2 max effort).

Regarding lactate vs lactic acid, they are often used interchangably because we produce lactic acid, but it immediately dissociates into lactate and a hydrogen ion. The lactate isn't the issue, as it is simply a substrate that can be converted back to pyruvate for fuel at rest or low intensity... it is the hydrogen ion that results in pain and fatigue

malmo wrote:

I like metabolism wrote:

I've typically seen anaerobic threshold and lactate threshold as synonymous terms in scientific literature. Some textbooks prefer the term OBLA (onset of blood lactate accumulation) as it is the most accurate descriptor. I've seen the anerobic threshold somewhat inaccurately described as the point at which our bodies shift from aerobic to anaerobic metabolism, but that's not quite right, as we don't just flip a switch, with aerobic turning off and anaerobic turning on. It's more like a dimmer switch... And we don't really every turn off either system. At rest, we have a measurable blood lactate level. And at VO2 max, we are optimizing both systems (a lactate level above 8 mmol and a high RER are both indicative of anaerobic contributions to energy production, and these are criteria used to determine if it is a true VO2 max effort).

Regarding lactate vs lactic acid, they are often used interchangably because we produce lactic acid, but it immediately dissociates into lactate and a hydrogen ion. The lactate isn't the issue, as it is simply a substrate that can be converted back to pyruvate for fuel at rest or low intensity... it is the hydrogen ion that results in pain and fatigue

Well done.

otter wrote:

I like metabolism wrote:

I've typically seen anaerobic threshold and lactate threshold as synonymous terms in scientific literature. Some textbooks prefer the term OBLA (onset of blood lactate accumulation) as it is the most accurate descriptor. I've seen the anerobic threshold somewhat inaccurately described as the point at which our bodies shift from aerobic to anaerobic metabolism, but that's not quite right, as we don't just flip a switch, with aerobic turning off and anaerobic turning on. It's more like a dimmer switch... And we don't really every turn off either system. At rest, we have a measurable blood lactate level. And at VO2 max, we are optimizing both systems (a lactate level above 8 mmol and a high RER are both indicative of anaerobic contributions to energy production, and these are criteria used to determine if it is a true VO2 max effort).

Regarding lactate vs lactic acid, they are often used interchangably because we produce lactic acid, but it immediately dissociates into lactate and a hydrogen ion. The lactate isn't the issue, as it is simply a substrate that can be converted back to pyruvate for fuel at rest or low intensity... it is the hydrogen ion that results in pain and fatigue

True, but to add to this:

- lactate is defined because it is large enough to be measured in a test and is linear to the amount of H+ produced and cleared.

- A slight correction is that lactate levels are individualized in terms of when they reach that tipping point and have a lot to do with fiber type and to some degree fitness. Someone else’s LT might be 8 mmmol while mine might be 6.5 for example. I have seen 4 as a typical LT threshold level example which it could be but also might not be again based on the individual.

I like metabolism wrote:

otter wrote:

True, but to add to this:

- lactate is defined because it is large enough to be measured in a test and is linear to the amount of H+ produced and cleared.

- A slight correction is that lactate levels are individualized in terms of when they reach that tipping point and have a lot to do with fiber type and to some degree fitness. Someone else’s LT might be 8 mmmol while mine might be 6.5 for example. I have seen 4 as a typical LT threshold level example which it could be but also might not be again based on the individual.

Oh, I wasn't indicating that 8mmol was related to lactate threshold... It is simply a standardized value that is used as a "validation criteria" for VO2 max testing... so it should be above the lactate threshold for most people. It was just making the point that the idea that when we "go anaerobic" it means we're not using aerobic metabolism. Quite the opposite, when endurance athletes are at very high intensities, we're maximizing both energy systems.

Very true though about the clinical relevance of lactate. The blood concentration of lactate is indicative of hydrogen production and is therefore meaningful still, even if the lactate itself is not problematic

I like metabolism wrote:

I've typically seen anaerobic threshold and lactate threshold as synonymous terms in scientific literature. Some textbooks prefer the term OBLA (onset of blood lactate accumulation) as it is the most accurate descriptor. I've seen the anerobic threshold somewhat inaccurately described as the point at which our bodies shift from aerobic to anaerobic metabolism, but that's not quite right, as we don't just flip a switch, with aerobic turning off and anaerobic turning on. It's more like a dimmer switch... And we don't really every turn off either system. At rest, we have a measurable blood lactate level. And at VO2 max, we are optimizing both systems (a lactate level above 8 mmol and a high RER are both indicative of anaerobic contributions to energy production, and these are criteria used to determine if it is a true VO2 max effort).

Regarding lactate vs lactic acid, they are often used interchangably because we produce lactic acid, but it immediately dissociates into lactate and a hydrogen ion. The lactate isn't the issue, as it is simply a substrate that can be converted back to pyruvate for fuel at rest or low intensity... it is the hydrogen ion that results in pain and fatigue

I like metabolism more wrote:

Curbside Pickup wrote:

Here is what I have in my "notes"

Anaerobic Threshold / Lactate Threshold

Anaerobic Threshold: The line separating mild lactate production and a spike in lactate production. The graph switches from mild positive slope to extreme positive slope.

Lactate Threshold: The pace that causes 4mmol/L of blood lactate as tested in a lab.

From my understanding, both terms are trying to get at the same idea. The difference is that LT is specifically defined a 4mmol/L, while Anaerobic Threshold is more of a theoretical idea and the actual measurement could be different for each person.

Happy to be corrected if I am off-base.

There is no spike in lactate when you cross this so called threshold. If there was then there would be a big metabolic difference between half marathon pace and 10k pace, when of course it is only a small difference.