Just curious, now that the heat is beginning to tick up down here in the south, does the increase in heat equal a slight increase in average daily weight (like a pound or two).
I have been tracking calories/weight pretty closely and I think that I have a pretty good target on what deficits do what to my weight and to my training, I am just curious if I am going to see a “unexplained” change of a pound or two in my average statistics over the warmer months.
Training in the heat does increase TOTAL body water. For example, going to Hawaii from a cold climate might increase TBW 1 liter (about 2.2 lbs) after a few days. Most of that added volume is in muscles, maybe 25% in plasma.
Training in the heat does increase TOTAL body water. For example, going to Hawaii from a cold climate might increase TBW 1 liter (about 2.2 lbs) after a few days. Most of that added volume is in muscles, maybe 25% in plasma.
That is kind of what I was thinking. So you are thinking on the order of a couple pounds then?
Yes, in my experience a couple of pounds (as reference, I’m around 160lbs). DO NOT interpret this as bad, it is good. Obviously the more body water you have to start with the more you can lose during the course of a long race. Plasma volume expansion is a good thing despite the slight weight gain.
In early acclimatization, it could be more than 1 liter. But then the kidneys regulate the volume so as to not overload the heart. I’ve seen some guys gain up to 5 lbs training in Hawaii the week before the Honolulu Marathon. Triathletes tend not to gain as much because of swimming, which increases urine output (as you know).
DO NOT interpret this as bad, it is good.
Understood, just wanted to make sure I knew what was happening if I maintain a slight caloric deficit and manage still to gain a couple pounds.
DO NOT interpret this as bad, it is good.
Understood, just wanted to make sure I knew what was happening if I maintain a slight caloric deficit and manage still to gain a couple pounds.
Also note that carbs stored in the body will need water, so, if one is in a taper and the body is holding more carbs it will also add weight (water weight). It can be depressing for those who focus too much on the scale. (like me sometimes 
)
Just curious, now that the heat is beginning to tick up down here in the south, does the increase in heat equal a slight increase in average daily weight (like a pound or two).
I have been tracking calories/weight pretty closely and I think that I have a pretty good target on what deficits do what to my weight and to my training, I am just curious if I am going to see a “unexplained” change of a pound or two in my average statistics over the warmer months.
I don’t know but Just Today I started tracking calories as I can’t seem to lose weight eating (what I thought was) normally. But we’ve had heat here since February so not sure. I have, however, moved my runs recently to early am or late pm as it sure feels hotter the last few weeks or so. Prolly is. I’d be interested to see what you come up with.
Also note that carbs stored in the body will need water, so, if one is in a taper and the body is holding more carbs it will also add weight (water weight).
Got a whole education on that topic reading Noakes’ books. Luckily, I run a light but consistent deficit and I weighh myself first thing in the AM, so this effect isn’t to pronounced for me. Though I have seen it when I was running big deficits and then had a race coming and chose to go ahead and make sure I was glycogen fueled. I put on something like 4 or 5 lbs (water weight) in a couple days by only eating the balanced number of calories.
it’s a good thing. tho any increase in VO2 from the additional cardiac output will likely be negated by increases in internal heat stress
Studies have shown no change in VO2max with increased body water (including plasma volume) during heat acclimation. Hemodilution of Hgband decreased AVO2D offset the increased SV.
it’s a good thing. tho any increase in VO2 from the additional cardiac output will likely be negated by increases in internal heat stress
I’ve made the extension via the assumption that plasma volume increases are like saline IV drips, which have been proven to increase VO2.
IV fluid might improve endurance performance in the heat, but it has no effect on VO2max.
I’ve made the extension via the assumption that plasma volume increases are like saline IV drips, which have been proven to increase VO2.
yes it does. Increase in plasma volume does increase VO2 max.
(i checked my sources)
OK, agree to disagree? Maybe start another thread?
yes it does. Increase in plasma volume does increase VO2 max.
(i checked my sources)
My sources wouldn’t agree with you 
And they are pretty smart guys
Another thread would work. I like it when the “science” threads on here really get rolling.
Well, from my point of view your sources are not smart enough
Perhaps we have a misunderstanding here about cause and effect? I say there’s no evidence that simply increasing plasma volume (for example, with physiological saline) increases VO2max. The miscommunication between you and your sources could be that they are saying increases in plasma volume, stroke volume, and VO2max with aerobic endurance training are inter-correlated.
Sure, start another thread on plasma volume. Among the boneheads, there are a lot of smart guys on this forum.
My sources wouldn’t agree with you And they are pretty smart guys
Another thread would work. I like it when the “science” threads on here really get rolling.
Ouch. Not sure Phil and Andy are gonna like that 
Increasing plasma volume artificially via saline bags won’t do anything for performance VO2 wise. You may get better performance because being hyper hydrated gives you more to lose, thus extending time to fatigue. However, increasing plasma volume through natural heat acclimatization will result in a boost of the good stuff too (rbc count, hemoglobin but not hematocrit) which will boost performance due to increased carrying capacity and the reasons stated above.