Longterm Cardiovascular Adaptation

[DavidM]

In athletes who compete in aerobic endurance events over many years of training and racing, at which site does the most gradual and permanent adaptation occur, is it heart, or is it skeletal muscle ?

I have a good understanding of the basics of aerobic training methods and physiological adaptations to such training, the principles of overload, specificity, neuromuscular efficiency and economy. I understand the concepts of VO2max, and Lactate Threshold, and also the nature of the adaptations which occur at the heart with increase in stroke volume, and at skeletal muscle with chemical changes and capillarisation.

This question arises as I have long term performance goals, and wish to primarily maximise my VO2max, and to devise a training program to achieve this. My current understanding is that interval work performed very near to VO2max will provide the greatest stimulus for VO2max improvement. And that this is mediated by an increase in stroke volume, and is an adaptation which is very gradual, probably a year by year process. This seems to fit with the observation that endurance athletes' resting HR seems at its lowest after many years of training.

I also thought that skeletal muscle adaptations were more quickly achieved and maximised over only a number of weeks, and were the site of adaptation associated with the anaerobic threshold. Some coaches seem to advocate 'tempo' level (i.e. significantly submaximal) work to raise the threshold.

I find now conflicting advice on the internet about where the more fundamental, longterm adaptation is occurring, some suggesting it is at skeletal muscle, and not at the heart. I would favour the heart, as this surely is the limiting factor in VO2max, i.e. maximum cardiac output, depending principally on stroke volume (maximum rate being unresponsive to training).
The 'alternative' view being that VO2max, and cardiac adpatations are quickly maximised, and that training should gear towards raising your threshold, and skeletal muscle adaptations.

I understand training to raise threshold is performed at a lower level than that to raise VO2max. Which should I be working on hardest if my goals are longterm and I wish to improve year on year ?

This post was suggested by Ric Stern, who very kindly responded to the same question, and felt this forum might have more to say on the matter.

To summarise - which adapts most fundamentally and least-reversibly in endurance aerobic athletes, is it Heart or is it Skeletal Muscle ?

 

[Roadie_scum]

That is a great question David M, and sums up something I've been wondering about for a while in a far more articulate way than I ever have been able to put it. Would there be any chance we could view Ric's response?

 

[ric_stern/RST]

Originally posted by Roadie_scum
That is a great question David M, and sums up something I've been wondering about for a while in a far more articulate way than I ever have been able to put it. Would there be any chance we could view Ric's response?

i wouldn't overly bother it was a horribly rushed response which i don't feel clearly articulates what i was wanting to say.

i wanted to respond to David, as it was such a great question, but wasn't of a great standard.

unfortunately (for this response), i'm really very busy at present and don't have the time needed to respond in a clear and articulate manner. i'm hoping that later on, i will, or that someone such as andy coggan or 2Lap may have the time to respond (although i know that both are busy).

ric

 

[drewjc]

I dont have a huge deal of knowledge in this field but am always open to new learning. From my current understanding i am of the opinion that the heart and its stroke volume has less effect on the VO2 max than the adaptations of the skeletal muscle does. It appears to me from my limited knowledge that VO2 max is a measure of the bodies ability to extract O2 from the blood (a partial pressure issue between the capilaries and the muscle), thus the limiting factor is not the amount of O2 being delivered to the body (stroke volume) but the rate at which it can use it (a skeletal muscle adaptation).

From this it would be my thinking that skeletal muscle adaptation and increasing the threshold would be more beneficial than any specific cardiac training methods, although to get the most out of your training these would still be necessary to some degree.

I hope what i have posted is clear and concise enough to recieve an answer/comment/mark from one of the more qualified of our posters here on the forum (Ric???).

Thanks.

 

[rkohler]

Originally posted by DavidM
In athletes who compete in aerobic endurance events over many years of training and racing, at which site does the most gradual and permanent adaptation occur, is it heart, or is it skeletal muscle ?

I have a good understanding of the basics of aerobic training methods and physiological adaptations to such training, the principles of overload, specificity, neuromuscular efficiency and economy. I understand the concepts of VO2max, and Lactate Threshold, and also the nature of the adaptations which occur at the heart with increase in stroke volume, and at skeletal muscle with chemical changes and capillarisation.

This question arises as I have long term performance goals, and wish to primarily maximise my VO2max, and to devise a training program to achieve this. My current understanding is that interval work performed very near to VO2max will provide the greatest stimulus for VO2max improvement. And that this is mediated by an increase in stroke volume, and is an adaptation which is very gradual, probably a year by year process. This seems to fit with the observation that endurance athletes' resting HR seems at its lowest after many years of training.

I also thought that skeletal muscle adaptations were more quickly achieved and maximised over only a number of weeks, and were the site of adaptation associated with the anaerobic threshold. Some coaches seem to advocate 'tempo' level (i.e. significantly submaximal) work to raise the threshold.

I find now conflicting advice on the internet about where the more fundamental, longterm adaptation is occurring, some suggesting it is at skeletal muscle, and not at the heart. I would favour the heart, as this surely is the limiting factor in VO2max, i.e. maximum cardiac output, depending principally on stroke volume (maximum rate being unresponsive to training).
The 'alternative' view being that VO2max, and cardiac adpatations are quickly maximised, and that training should gear towards raising your threshold, and skeletal muscle adaptations.

I understand training to raise threshold is performed at a lower level than that to raise VO2max. Which should I be working on hardest if my goals are longterm and I wish to improve year on year ?

This post was suggested by Ric Stern, who very kindly responded to the same question, and felt this forum might have more to say on the matter.

To summarise - which adapts most fundamentally and least-reversibly in endurance aerobic athletes, is it Heart or is it Skeletal Muscle ?

My two cents. I think it depends what you're talking about. If you're asking about limitations of VO2 max, then the answer is multi-factorial. There really isn't any clear answer to that question yet. Some studies have found that there can be pulmonary limitations to VO2 max, while others found that it is cardiac output that can be affected, and others say that it could be the muscle (extraction -> aV-O2 difference).

To take a stab at your second to last question, I think that you should work on a little bit of everything if you want to improve your VO2 max. You should have a certain part of the year where you work the aerobic system (such as a base/preparation period) and then another time of the year where you focus on the high intensity work (increasing your LT and/or eventually VO2 max). Then of course you can transition into another phase, and so on. Since your goals are longterm, there isn't any need for a rush and for you to hit the VO2 max training hard and long right now. You can take your time and build throughout the year where you give yourself a certain amount of weeks to train that system specifically, but also train other systems equally so you have a well-balanced program.

As for the last question, which adapts most fundamentally and least reversibly, it seems to be that your body adapts pretty similarly. As for least reversibly, some literature has found that stroke volume will decrease/reverse first, followed by aV-O2 difference. There are a few other things that can happen. Muscle enzyme changes can occur and can account for any alterations in exercise capacity, performance, and/or VO2 max. These enzyme changes can happen quickly - within hours. Stroke volume can change next, in a couple of days up to about 1 week or so (3-8 days). And finally, it looks like the capilarization (related to aV-O2 difference) will change months down the road with decreased activity levels.

Hope this helps a little bit.

 

[biker-linz]

Hi David.

I'm sure Ric and others would have more to say on this than me, but my understanding is that VO2max is becoming less of a predictor of endurance performance than perhaps it once was.
Of more importance is the power you are able to produce for extended periods of time, which is a function of VO2max, but also efficiency and lactate clearance / tolerance.
It is my understanding that the cardio-pulmonary aspect of aerobic power is a fairly short-term adaptation, but I could be mistaken. I believe I am right in saying, however, that research has shown that the higher power seen in elite athletes is often the result of a higher numbers of ST and FTa fibres, which has been linked with year on year adaptaions to hard training. My guess is that it is the adaptations in skeletal muscle which occur over the long term and are probably the last to reverse.

Any more takers??

Lindsay.

 

[acoggan]

VO2max = HRmax x SVmax x arteriovenous (a-v) O2 extraction @ max

When an untrained person takes up moderate intensity training for a short period of time (e.g., a few months), increases in SVmax and a-vO2 difference contribute about equally to the increase in VO2max. (HRmax, OTOH, tends to go down, which tends to limit the increase in maximal cardiac output and hence VO2max.) However, a-vO2 difference is already nearly as high as it can be even in an untrained person, because almost all of the O2 is already being extracted from the blood. Thus, any increase (or difference) in VO2max greater than ~10% *must* be due to a difference in SV, and in fact it is this parameter that differs most dramatically when e.g., comparing highly trained endurance athletes against untrained individuals. Generally speaking, the lungs are considered "overbuilt" for exercise, although O2 transport into arterial blood may become limiting when VO2max is very high.

As for the time-course of adaptations, the working hypothesis in the field of exercise physiology is that SV and therefore VO2max tend to reach a plateau fairly early in an athlete's career (assuming, of course, that the training load is sufficiently high), with further improvements in performance being due to adaptations within skeletal muscle that influence LT and efficiency.

 

[biker-linz]

FYI, Exercise and Sport Sciences Reviews is currently free online.

Funnily enough, there is a very interesting article: 'Adaptations of Skeletal Muscle Mitochondria to Endurance Exercise: A Personal Perspective'
Holloszy, John O.

Help yourselves at

http://www.acsm-essr.com/pt/re/essr/

and go to 'Current Issue'

He mentions some guy called Andy Coggan in there, too!

Lindsay.

 

[dot]

Good article on adaptations:

http://home.hia.no/~stephens/timecors.htm

 

[edd]

Your question

Originally posted by DavidM
In athletes who compete in aerobic endurance events over many years of training and racing, at which site does the most gradual and permanent adaptation occur, is it heart, or is it skeletal muscle ?

is flawed somewhat because “permanent adaptation” is not what happens to the human body, we are all in a state of flux. But not to split hairs, I get your drift.

I don’t know the answer but I suspect it would be the heart that would be least likely to detrain because it is in constant use. This also poses the question about training stimuli, recovery and adaptation. The heart is a muscle and would be effected by varying stresses similarly to (but not the same as) the skeletal muscles.

The heart is unique I suspect it would probably take longer to train.
There are reasons for the suspicion the most obvious one being the bio-synchronous nature of the hearts function.

Originally posted by DavidM
neuromuscular efficiency and economy

Can be an evolving stimuli and take years to develop

Originally posted by DavidM
I also thought that skeletal muscle adaptations were more quickly achieved and maximized over only a number of weeks

I thought years ?

There are a few missing elements here, ie blood hemoglobin, liver glycogen stores, hormonal response to stress, role of the lipidolytic delivery under increased stress.

I think LA is a good case study.. He would have suffered substantial muscle wastage, evident in his upper body. Yet he not only came back from a near terminal disease. He got back to the top in a reasonably short period of time.

His genes aside, This seems to imply that adaptation runs deeper then the obvious and is more permanent then we might ( I might ) expect.

 

[Roadie_scum]

Originally posted by edd
Your question is flawed somewhat because “permanent adaptation” is not what happens to the human body, we are all in a state of flux. But not to split hairs, I get your drift.

I think if you are going to split hairs you should split them correctly. The question asked which was the 'most permanent', not which was permanent. There would be other ways of framing this question (eg which training adaption takes the longest to detrain, how long does the training adaption last when the training stimulus is removed, do effects of training continue after cessation of activity and for how long), but they all mean close to the same thing. There is nothing wrong in logic or fact with asking which adaption is most permanent.

 

[DavidM]

Thanks everyone for your thoughts. As I suspected there is no absolute answer. But these replies are great. Thanks !

 

[dhk]

Originally posted by biker-linz
FYI, Exercise and Sport Sciences Reviews is currently free online.

Funnily enough, there is a very interesting article: 'Adaptations of Skeletal Muscle Mitochondria to Endurance Exercise: A Personal Perspective'
Holloszy, John O.

Help yourselves at

http://www.acsm-essr.com/pt/re/essr/

and go to 'Current Issue'

He mentions some guy called Andy Coggan in there, too!

Lindsay.

Very interesting article, although some of it was well beyond my level. Thanks for the link.

 

[edd]

Originally posted by Roadie_scum
I think if you are going to split hairs you should split them correctly. The question asked which was the 'most permanent', not which was permanent. There would be other ways of framing this question (eg which training adaption takes the longest to detrain, how long does the training adaption last when the training stimulus is removed, do effects of training continue after cessation of activity and for how long), but they all mean close to the same thing. There is nothing wrong in logic or fact with asking which adaption is most permanent.

Rule of thumb: 10% loss of endurance performance after 10 days of no activity. Which is why I split the hair. We are in more of a state of flux then we imagine (I imagine). Thing is we seem to retain the ability to regain our fitness in a short period of time if we have a training history.

 

[Michuel]

Originally posted by edd
Rule of thumb: 10% loss of endurance performance after 10 days of no activity.

Are you sure that's right - I'd have thought about 5%+ ?

A 10% loss would imply a 6minute slowdown to 66mins for 25 miles from 60mins. This week in CW Malcolm Elliott claims he had no riding for a week yet finished 2nd in Shay Elliott memorial to O'Loughlin. In lead up to some long endurance event I do only very light riding over last 5+ days- none of which would qualify as 'training' to this forum.

 

[edd]

Originally posted by Michuel
Are you sure that's right - I'd have thought about 5%+ ?

A 10% loss would imply a 6minute slowdown to 66mins for 25 miles from 60mins. This week in CW Malcolm Elliott claims he had no riding for a week yet finished 2nd in Shay Elliott memorial to O'Loughlin. In lead up to some long endurance event I do only very light riding over last 5+ days- none of which would qualify as 'training' to this forum.

Please note" no activity" any activity at all be it active rest and the detraining effect is reduced. I read something on this about 15 years ago, not able to put my hands on it now. This is obviously different for different individuals, ie:
older people require longer recovery periods (adaptation periods) then younger folk and there detraining period is also longer. I know of a 42 year old runner who took three weeks off and came back to post a PB in a half marathon.

The fitter you are the harder it is to maintain a performance peak.

And the flip side is a week off has negligible detraining effect.

Three days off can be beneficial to performance

I personally like to tapper training two weeks before a pet event and put in a long very easy ride ( or what ever the sport is ) a week out and a couple of very hard very very short sharpening sessions in the week leading up to the event with at least two days rest before the event.

As I said "rule of thumb."

 

[Aeri]

I just posted a query regarding fitness losses and recovering them in the health .... recovery..etc section hope you guys can help out

 

[DavidM]

Hi guys, me again. Still thinking about limitations to VO2Max. I've re-read the replies, and think I've picked up some useful ideas.

I'd like to throw in a further point, regarding EPO use. I understand the main advantage this gives is to increase the oxygen carrying capacity of blood. It seems that a nice dose of EPO will always (?) 'supercharge' an athlete's performance, even if he/she is already at his/her natural maximal trained state. Observe how 'average' performers can become world-beaters when 'helped' by EPO. (Too many names to mention...).

How does this inform ideas about limiting factors to VO2max ? i.e. which part of the CV system is 'over-engineered' regarding aerobic performance ? I think it's accepted that the lungs are not the limiting factor. I think its predominantly cardiac output which is the limiting factor, and it's proven by the EPO phenomenon - i.e. skeletal muscle, and its O2 supply system (capillarisation) can ALWAYS utilise more oxygen, and perform harder, whether this O2 is delivered by greater cardiac output, or by greater blood oxygen load (secondary to EPO use). If O2 diffusion/utilisation in the muscle were the limiting factor, then surely an increase in blood oxygen would not produce such a spectacular improvement in performance.

Feel free to shoot me down if you think my logic is false, but I think this adds weight to my thinking that its the heart that is the primary limitation to VO2Max.

I'd love to hear your comments.

 

[edd]

Hi guys, me again. Still thinking about limitations to VO2Max. I've re-read the replies, and think I've picked up some useful ideas.

I'd like to throw in a further point, regarding EPO use. I understand the main advantage this gives is to increase the oxygen carrying capacity of blood. It seems that a nice dose of EPO will always (?) 'supercharge' an athlete's performance, even if he/she is already at his/her natural maximal trained state. Observe how 'average' performers can become world-beaters when 'helped' by EPO. (Too many names to mention...).

How does this inform ideas about limiting factors to VO2max ? i.e. which part of the CV system is 'over-engineered' regarding aerobic performance ? I think it's accepted that the lungs are not the limiting factor. I think its predominantly cardiac output which is the limiting factor, and it's proven by the EPO phenomenon - i.e. skeletal muscle, and its O2 supply system (capillarisation) can ALWAYS utilise more oxygen, and perform harder, whether this O2 is delivered by greater cardiac output, or by greater blood oxygen load (secondary to EPO use). If O2 diffusion/utilisation in the muscle were the limiting factor, then surely an increase in blood oxygen would not produce such a spectacular improvement in performance.

Feel free to shoot me down if you think my logic is false, but I think this adds weight to my thinking that its the heart that is the primary limitation to VO2Max.

I'd love to hear your comments.

at the end of the day it is your VO2 max potential x your sustainable power output that will determine your performance.. but it is a mistake to over think this. Your potential is your potential train hard, train smart, see what eventuates. In training it is usually the muscles that lose/gain conditioning, your body dismantles mitochondria as readily as it builds it, then there's them metabolic pathways, the body's search for efficiency.

Human logic is flawed. 300 years ago we thought the world was flat. 300 hundred years from now we'll think....."

Seek improvement, measure it, gather evidence, learn what works for you.

 

[edd]

I just posted a query regarding fitness losses and recovering them in the health .... recovery..etc section hope you guys can help out

stick a link on this post.