How much blood volume is lost after 2 days no training? And does this loss include red blood cells, or does the total number of red blood cells increase due to the rest?
I think something is missing here so let’s start with some first principles. Blood has both a cellular (RBC) and a non-cellular basis. The non-cellular basis consists of serum or plasma. You don’t say what or how you are training but let’s say that consists of an hour or two of aerobic exercise for discussion purposes. Not exercising at the rate of 1-2 hours/day for 2 days has no appreciable effect on much of anything except caloric balance (in- and used numbers).
Blood volume changes with big metabolic events like pregnancy (it goes up), hemorrhagic (it goes down) and extended illness. Despite endurance athlete’s belief that there are big changes going on, homeostasis governs our ability to survive along timelines of decades and there is surprisingly little change with days of changing activities. Immobilization (as in confined to bed) is another matter, particularly if it involves serious illness.
Perhaps there is more to what you are asking than what I read here.
None? Unless your lack of exercise includes covering yourself with leeches or blood letting.
Red blood cells live for 100-120 days.
What exactly are you asking?
I’m askin how much blood volume is lost if you don’t train for 2 days.
That is what Imthought about the red blood cells but I’m told blood volume is lost and this affects performance.
I’m asking how it affects performance if you don’t lose red blood cells.
Good question Trev (see - you can do it 
). I have heard it said blood plasma drops after a period of inactivity and this has been held up as a reason for performance drop off in some people. There might also be a slight maintenance in existing rbcs that would OTHERWISE be killed off if one was exercising through hemolysis and particularly through running as more pronounced.
I think we need some physiologists or cardiologists to chime in (Andy Coggan)?
Weigh yourself and if your weight changes a good bit, then it will be from plasma volume.
Otherwise it will be pretty difficult to know without bleeding yourself dry twice!
You won’t lose RBCs, or very few and it’s only 2 days, that’s just a rest. Your bone density probably won’t change too much if you don’t run today either!
Trev,
I start “pissing away” blood volume by the end of the first day of no training. I’ll need to get up at 3am and urinate when that’s never a need when training. It happens even if I intentionally drink vastly less on non training days as well so I doubt it’s due to hydration status. My veins become visibly less prominent as well. As others have said it’s most certainly plasma loss going on. On the flip side I’ve read the initial boost in VO2 max seen nearly immediately with the commencement of training from an untrained state is due to quick increase in blood volume.
YMMV,
Hugh
Trev,
I start “pissing away” blood volume by the end of the first day of no training. I’ll need to get up at 3am and urinate when that’s never a need when training. It happens even if I intentionally drink vastly less on non training days as well so I doubt it’s due to hydration status. My veins become visibly less prominent as well. As others have said it’s most certainly plasma loss going on. On the flip side I’ve read the initial boost in VO2 max seen nearly immediately with the commencement of training from an untrained state is due to quick increase in blood volume.
YMMV,
Hugh
Does this loss of plasma result in loss of performance for you?
Trev,
I start “pissing away” blood volume by the end of the first day of no training. I’ll need to get up at 3am and urinate when that’s never a need when training. It happens even if I intentionally drink vastly less on non training days as well so I doubt it’s due to hydration status. My veins become visibly less prominent as well. As others have said it’s most certainly plasma loss going on. On the flip side I’ve read the initial boost in VO2 max seen nearly immediately with the commencement of training from an untrained state is due to quick increase in blood volume.
YMMV,
Hugh
Does this loss of plasma result in loss of performance for you?
It seems to. I always feel flat with two days completely off and never seem to get the “bump” a taper might expect to give. It only takes an extremely small amount of intensity to prevent this. I have seen some pretty stellar days the day after some really significant intensity. Jack Daniels has written about grouping two days of intensity in a row because so many of his athletes experience this same effect.
Hugh
I think we need some physiologists or cardiologists to chime in (Andy Coggan)?
I would, but that would just be feeding the troll.
Yep ^^^^
.
I often do two very hard days in a row. But I always really suffer on the third day.
I always go well after two days off or two very easy days. But most say they don’t respond to two rest days or even one.
Sometimes one rest day doesn’t do anything for me but 2 days always does.
I think we need some physiologists or cardiologists to chime in (Andy Coggan)?
I would, but that would just be feeding the troll.
Volunteer No 14.
The blood volume sounds like a complete red herring to me. Ask yourself where would it go and what component would you be loosing? I do seem to remember that when the Garmin team started back in 2008, they published their hematocrit scores during the Tour and those went down over 21 days of intense racing. So about the only thing a 2 day rest period would do would be to increase your RBC (a TINY amount), assuming you were way over trained.
I might feel a bit stiff and sluggish after 2-3 days of very little activity, but if it comes after a hard block of training I know that the rest will be beneficial. I also expect to see a bump in my power numbers later in the week following a rest block. If you ask me, one of the biggest values of a coach is getting athletes to rest for the correct time and duration.
I think something is missing here so let’s start with some first principles. Blood has both a cellular (RBC) and a non-cellular basis. The non-cellular basis consists of serum or plasma. You don’t say what or how you are training but let’s say that consists of an hour or two of aerobic exercise for discussion purposes. Not exercising at the rate of 1-2 hours/day for 2 days has no appreciable effect on much of anything except caloric balance (in- and used numbers).
Blood volume changes with big metabolic events like pregnancy (it goes up), hemorrhagic (it goes down) and extended illness. Despite endurance athlete’s belief that there are big changes going on, homeostasis governs our ability to survive along timelines of decades and there is surprisingly little change with days of changing activities. Immobilization (as in confined to bed) is another matter, particularly if it involves serious illness.
Perhaps there is more to what you are asking than what I read here.
Yes there is more to the question. There seems to be some sort of belief among cyclists and other endurance athletes that days off are bad for you. I have seen posts on forums from coaches who say that one reason why days off are bad is because of plasma loss. But there is no loss of red blood cells so how can a tiny loss of plasma if any impact on oerformance?
I have read that a few days bed rest does induce a small percentage of plasma loss and also that a few weeks of no training does result in plasma loss. But we are not talking about being in bed all day or not training for a few weeks, we are looking at a day or two with no training but still being reasonably active.
Cyclists and endurance athletes tend to have some sort of illogical fear of rest days or days off.
So I’m asking why does this plasma loss myth persist?
Or, if it isn’t a myth, how much plasma is lost after 2 days of not training but being reasonably active? And how does this plasma loss cause fitness to be lost? Is there any evidence to prove that fitness is lost after 2 rest days or 2 very easy days?
I find after 2 days rest, performance has improved and my power to heart rate ratio has also improved. Where is the fitness loss? If there is plasma loss it certainly isn’t causing any loss of performance.
The blood volume sounds like a complete red herring to me. Ask yourself where would it go and what component would you be loosing? I do seem to remember that when the Garmin team started back in 2008, they published their hematocrit scores during the Tour and those went down over 21 days of intense racing. So about the only thing a 2 day rest period would do would be to increase your RBC (a TINY amount), assuming you were way over trained.
I might feel a bit stiff and sluggish after 2-3 days of very little activity, but if it comes after a hard block of training I know that the rest will be beneficial. I also expect to see a bump in my power numbers later in the week following a rest block. If you ask me, one of the biggest values of a coach is getting athletes to rest for the correct time and duration.
It does seem many endurance athletes have a pathalogical fear of rest days.
Trev,
I start “pissing away” blood volume by the end of the first day of no training. I’ll need to get up at 3am and urinate when that’s never a need when training. It happens even if I intentionally drink vastly less on non training days as well so I doubt it’s due to hydration status. My veins become visibly less prominent as well. As others have said it’s most certainly plasma loss going on. On the flip side I’ve read the initial boost in VO2 max seen nearly immediately with the commencement of training from an untrained state is due to quick increase in blood volume.
YMMV,
Hugh
Does this loss of plasma result in loss of performance for you?
It seems to. I always feel flat with two days completely off and never seem to get the “bump” a taper might expect to give. It only takes an extremely small amount of intensity to prevent this. I have seen some pretty stellar days the day after some really significant intensity. Jack Daniels has written about grouping two days of intensity in a row because so many of his athletes experience this same effect.
Hugh
I experience nearly the same thing. During a taper, if I take 2 days complete day off I’ll feel flat the next day. A 30 minute easy run on the days before a race really helps me a lot.
jaretj
Thanks for the clarification. A few things come to mind - 1) medical research is challenging to fund and doesn’t concern itself generally with minor adjustments that might be performance-relevant but have nothing to do with preserving life; 2) the 2-day no training describes virtually every pro endurance athlete that isn’t local to the race itself so it isn’t impossible to answer the question your are asking using subjects as their own control(s); 3) plasma volume isn’t measured directly but actually approximated by backing out concentrations knowing the amount of a tracer that is added; 4) I’m really surprised at the emphasis on plasma as opposed to the RBC fraction which is much more performance-relevant. I can’t count the number of times over 45 years that I’ve driven all night (or flown) to make a race so I’m not sure how available opportunities would be for someone to train right up to race day.
Anyway, thanks for asking the question, Trev. Tom.
A few things here.
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where is this plasma loss being discussed? I’ve never heard it mentioned in discussions of tapering or rest. Where are you seeing it and do you have links to give us some context?
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you need to be clear with terms like fitness. You seem to be talking about performance gains after 2 days of rest. That is different than fitness gains or losses. You are likely less fatigued and can perform better, but your fitness is dropping after 2 days.
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a rest day means you aren’t improving fitness. Too many rest days and you lose too many days that you could’ve gained fitness. Too few rest days/easy days and you get too fatigued to continue training at a high level.
A few things here.
-
where is this plasma loss being discussed? I’ve never heard it mentioned in discussions of tapering or rest. Where are you seeing it and do you have links to give us some context?
-
you need to be clear with terms like fitness. You seem to be talking about performance gains after 2 days of rest. That is different than fitness gains or losses. You are likely less fatigued and can perform better, but your fitness is dropping after 2 days.
-
a rest day means you aren’t improving fitness. Too many rest days and you lose too many days that you could’ve gained fitness. Too few rest days/easy days and you get too fatigued to continue training at a high level.
Also in the context of age groupers, I think rest days is a tricky one. One guy might end up spending 4 hours putting down tiles in his kitchen or landscaping and count it as a rest day in his log. Another guy might do a 60 min spin at 50% FTP, spend the rest of the day on the couch watching football and count it as a “work day” but guess which one is the real rest day.