Physiology behind high HR when cycling AFTER weight training?



SolarEnergy

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biker-linz said:
I think he means plasma volume. Reduced plasma volume (sweating etc.) = reduced pre-load = reduced stroke volume = increased HR.
In your opinion, do we loose more plasma while riding for an hour, or weight lifting for an hour?

biker-linz said:
If what you mean is that the extra work the heart is doing will make it more econmical then I doubt it.
L.:)
What I meant rather is that if that extra workload placed on the heart actually help making it better adapted (bigger etc), can this be considered as a positive outcome? Bigger heart= increased stroke volume?
 

biker-linz

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SolarEnergy said:
In your opinion, do we loose more plasma while riding for an hour, or weight lifting for an hour?
I guess that would depend on a whole load of things: ambient conditions, type, intensity and duration of exercise etc. etc.

SolarEnergy said:
What I meant rather is that if that extra workload placed on the heart actually help making it better adapted (bigger etc), can this be considered as a positive outcome? Bigger heart= increased stroke volume?
No, that's kind of what I figured you meant and I don't think so. Besides, the heart isn't exactly working *harder*, it's just beating faster.

L.
 

Doctor Morbius

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biker-linz said:
Hey DM, I'm only speculatin'!! TBH I hadn't read all the preceding posts terribly carefully. All the same, I think it's a fair guess.:)

L.
Guess?! :confused: Well, so much for the scientific approach then. ;)
 

rippitupp

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biker-linz said:
Acidosis and reduction of pH are one and the same thing (pH is the negative logarithm of proton concentration). My understanding of the literature is:

a. that metabolic acidosis is not the result of protons dissociating from so-called 'lactic acid',
b. the lactate dehydrogenase reaction consumes a proton thus retarding acidosis,
c. that acidosis may not actually be responsible for 'muscular contraction slow down' as you call it (i would call it fatigue :)) and
d. that the exact mechanisms of fatigue are still unclear, although phosphate ion accumulation is one of the candidates.

L.
i find this very interesting. i tried looking up the references you mentioned. you wouldn't happen to have a copy of the full studies would you? i would very much like to read them.
could you explain a little more about point a? are you talking about the cellular pH or the blood pH.
metabolic acidosis can be caused by many things and there are many cellular waste products that are acids or proton donor's. i thought the phosphate molecule was a weak acid which would require a large amount to cause such a dramatic change in pH? a metabolic acidosis is the drop in blood pH with the associated drop in bicarbonate concentration, while maintaining a normal CO2 concentration. the first metabolic marker we look for is the lactate concentration.
 

rippitupp

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biker-linz said:
I guess that would depend on a whole load of things: ambient conditions, type, intensity and duration of exercise etc. etc.

No, that's kind of what I figured you meant and I don't think so. Besides, the heart isn't exactly working *harder*, it's just beating faster.

L.
i think trying to narrow it down to one thing as the cause of HR increase is futile...the body is complex, and every response is driven by neural-hormonal changes. the SNS is your stress response system.

the heart is extremely sensitive to the chemical changes in the body. for instance acidosis cause a decrease in the contractility of the heart.(the strength and effectivness of contraction). inorder to maintain cardiac output the HR increases, the vascular resistance increases, and the body shunts blood from other non essential areas. The heart doesn't get bigger. the muscle will hypertrophy to an extent, but interms of overall space occupying size there is very little change.
 

SolarEnergy

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rippitupp said:
i think trying to narrow it down to one thing as the cause of HR increase is futile...the body is complex, and every response is driven by neural-hormonal changes. the SNS is your stress response system.

the heart is extremely sensitive to the chemical changes in the body. for instance acidosis cause a decrease in the contractility of the heart.(the strength and effectivness of contraction). inorder to maintain cardiac output the HR increases, the vascular resistance increases, and the body shunts blood from other non essential areas. The heart doesn't get bigger. the muscle will hypertrophy to an extent, but interms of overall space occupying size there is very little change.
I agree. That's why it is such an interesting post :)

biker-linz said:
.....For what's it's worth DM I think that your HR is probably elevated due to a change in the balance of the sympathetic and parasympathetic nervous systems, residual to the stress of weight training. Increased levels of circulating adrenaline (that's epinephrine for our US readers!;)) would cause the symptoms you describe.
L.
BL, do you think the cause(s) for higher HR when cycling after weight lifting, could also triggered higher HR DURING the weight lifting session?
 

biker-linz

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SolarEnergy said:
I agree. That's why it is such an interesting post :)

BL, do you think the cause(s) for higher HR when cycling after weight lifting, could also triggered higher HR DURING the weight lifting session?
TBH, in the situation described by the OP I think Andy was probably dead right; that an acute redcution in plasma volume caused the inrease in HR. As far as the balance between PNS and SNS, this is the explanation often used to explain changes in resting HR due to fatigue (as well as changes in HR at the same intensity when fatigued), although the unreliability of it has caused many researchers to move on to HR variability. I wouldn't worry about it *too* much though, it's just worth bearing in mind when using a HRM.

L.
 

rippitupp

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An acute plasma reduction can cause an increase in heart rate, but in a healthy individual you would have to lose close to half a liter of fluid to trigger a compensatory increase in HR to maintain cardiac output



biker-linz said:
TBH, in the situation described by the OP I think Andy was probably dead right; that an acute redcution in plasma volume caused the inrease in HR. As far as the balance between PNS and SNS, this is the explanation often used to explain changes in resting HR due to fatigue (as well as changes in HR at the same intensity when fatigued), although the unreliability of it has caused many researchers to move on to HR variability. I wouldn't worry about it *too* much though, it's just worth bearing in mind when using a HRM.

L.
 

SolarEnergy

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rippitupp said:
An acute plasma reduction can cause an increase in heart rate, but in a healthy individual you would have to lose close to half a liter of fluid to trigger a compensatory increase in HR to maintain cardiac output
Hi, you have waken up one of my favorite discussion:)

Do you think that the reason(s) that explains the higher HR when cylcing after w-lifting are the same reason(s) that explains the higher HR while weight lifting?