F
On Jul 31, 11:02 am, Michael Press <[email protected]> wrote:
> In article
> <[email protected]>
> ,
>
>
>
> [email protected] wrote:
> > On Jun 7, 11:57 am, Andy Coggan <[email protected]> wrote:
> > > On Jun 5, 11:04 pm, "Phil Holman" <piholmanc@yourservice> wrote:
>
> > > > <[email protected]> wrote in message
> > > > > In recent times, steam RR locomotives, although not rated in Horse
> > > > > Power (but rather "tractive effort", the pull at which the wheels
> > > > > would spin) had a conversion chart to HP based on grate area in the
> > > > > fire box which governs how much heat can be transferred to steam in
> > > > > the boiler. Grate area is closely similar to lung displacement for
> > > > > physically fit racers. That is what limits climbing or TT ability,
> > > > > not ankling, pedaling style or other external means.
>
> > > > You continue to repeat this misconception. Lung displacement or lung
> > > > capacity is not the limiting factor in climbing or TTing or cycling in
> > > > general. If you understood the cause and effect elements you would
> > > > understand that extreme "out of breath" is caused by excess CO2 in the
> > > > blood stream as a result of lactic buffering.
>
> > > Great! Now we have one engineer feeding misconceptions about how
> > > physiology functions to another engineer...
>
> > No, now we have an exercise physiologist trying to correct someone
> > with a correct understanding of the limiter. I am truly amazed that
> > you haven't figured out what is going on here yet.
>
> > > Fact: CO2 plays only a very limited role in regulating ventilation
> > > during exercise.
>
> > Fact: There are two main drivers for ventilation. CO2 and O2. The main
> > one is CO2. The body adjusts ventilation to maintain the arterial
> > partial pressure of CO2 at 40torr. CO2 is the prime determiner of
> > ventilatory function at all times except during extreme hypoxia, which
> > never occurs during normal exercise.
>
> > > > That is, the limits of
> > > > aerobic capacity were reached upstream (cardiac output, blood muscle
> > > > interface limitations etc) and no further limitations are imposed by the
> > > > lungs. It wouldn't matter if you doubled lung capacity, blood lactate
> > > > concentrations wouldn't change and this is the culminating event in
> > > > limiting aerobic performance. Heavy breathing is an effect not a cause.
>
> > > In fact, mild-to-moderate arterial desaturation tends to occur during
> > > maximal exercise in a significant portion of the population (at least
> > > discounting young, healthy, untrained men!), indicating that, at least
> > > to some extent, aerobic capacity (i.e., VO2max) is limited, in part,
> > > by pulmonary function.
>
> > Phoeey. A small arterial desaturation is most likely explained by
> > increased left to right shunting and ventilation perfusion mismatch at
> > the extremes and is probably has no effect on performance because of
> > the oxyhemoglobin saturation curve. There could be other explanations
> > also such as a shift in the curve due to changes in pH. Small levels
> > of desaturation have almost no effect on oxygen carrying capacity to
> > the tissues.
>
> I am incompetent to assess these matters. I have read
> very little, but got the impression that the limiting
> factor in aerobic work capacity is the mitochondria
> themselves.
>
> --
> Michael Press
In my opinion, the limiter is the ability to deliver oxygen to the
mitochondria so the mitochonria compensate by using another mechanism
with lactic acid as an end point. Once there are enough mitochondria
in this situation the amount of lactic acid being produced overwhelms
the bodies ability to compensate for this and the "failure cascade"
starts.
> In article
> <[email protected]>
> ,
>
>
>
> [email protected] wrote:
> > On Jun 7, 11:57 am, Andy Coggan <[email protected]> wrote:
> > > On Jun 5, 11:04 pm, "Phil Holman" <piholmanc@yourservice> wrote:
>
> > > > <[email protected]> wrote in message
> > > > > In recent times, steam RR locomotives, although not rated in Horse
> > > > > Power (but rather "tractive effort", the pull at which the wheels
> > > > > would spin) had a conversion chart to HP based on grate area in the
> > > > > fire box which governs how much heat can be transferred to steam in
> > > > > the boiler. Grate area is closely similar to lung displacement for
> > > > > physically fit racers. That is what limits climbing or TT ability,
> > > > > not ankling, pedaling style or other external means.
>
> > > > You continue to repeat this misconception. Lung displacement or lung
> > > > capacity is not the limiting factor in climbing or TTing or cycling in
> > > > general. If you understood the cause and effect elements you would
> > > > understand that extreme "out of breath" is caused by excess CO2 in the
> > > > blood stream as a result of lactic buffering.
>
> > > Great! Now we have one engineer feeding misconceptions about how
> > > physiology functions to another engineer...
>
> > No, now we have an exercise physiologist trying to correct someone
> > with a correct understanding of the limiter. I am truly amazed that
> > you haven't figured out what is going on here yet.
>
> > > Fact: CO2 plays only a very limited role in regulating ventilation
> > > during exercise.
>
> > Fact: There are two main drivers for ventilation. CO2 and O2. The main
> > one is CO2. The body adjusts ventilation to maintain the arterial
> > partial pressure of CO2 at 40torr. CO2 is the prime determiner of
> > ventilatory function at all times except during extreme hypoxia, which
> > never occurs during normal exercise.
>
> > > > That is, the limits of
> > > > aerobic capacity were reached upstream (cardiac output, blood muscle
> > > > interface limitations etc) and no further limitations are imposed by the
> > > > lungs. It wouldn't matter if you doubled lung capacity, blood lactate
> > > > concentrations wouldn't change and this is the culminating event in
> > > > limiting aerobic performance. Heavy breathing is an effect not a cause.
>
> > > In fact, mild-to-moderate arterial desaturation tends to occur during
> > > maximal exercise in a significant portion of the population (at least
> > > discounting young, healthy, untrained men!), indicating that, at least
> > > to some extent, aerobic capacity (i.e., VO2max) is limited, in part,
> > > by pulmonary function.
>
> > Phoeey. A small arterial desaturation is most likely explained by
> > increased left to right shunting and ventilation perfusion mismatch at
> > the extremes and is probably has no effect on performance because of
> > the oxyhemoglobin saturation curve. There could be other explanations
> > also such as a shift in the curve due to changes in pH. Small levels
> > of desaturation have almost no effect on oxygen carrying capacity to
> > the tissues.
>
> I am incompetent to assess these matters. I have read
> very little, but got the impression that the limiting
> factor in aerobic work capacity is the mitochondria
> themselves.
>
> --
> Michael Press
In my opinion, the limiter is the ability to deliver oxygen to the
mitochondria so the mitochonria compensate by using another mechanism
with lactic acid as an end point. Once there are enough mitochondria
in this situation the amount of lactic acid being produced overwhelms
the bodies ability to compensate for this and the "failure cascade"
starts.