A question for all you experienced Triathletes:I’m really struggling with the idea that I don’t know how much fluid and electrolytes I need to replace during training and racing. I currently aim to drink 500ml of water per hour during a typical session. I don’t know if this is enough/adequate, but, I also don’t know how to find out what I need to drink…How do I know what I need to drink to ensure adequate hydration during training and racing to ensure I’m not getting dehydrated? And, where are you finding this information as I’m struggling to find any information surrounding how to hydrate correctly?Thanks for any advice in advance 
How long are your typical training rides?
Usually somewhere between 60min and 2hours… I’m racing an Ironman at the end of this year though so will be looking to increase this over the coming months though.
Hydration should match sweat loss, if possible. As should sodium, if possible. The reason for “if possible” = gut constraints often won’t let you. Read: upset GI tract is not fun!
If not sweating much 500mL/hr might be great.
If sweating heavily, it’s far short of optimal.
Other reason for increasing fluid intake is to accommodate optimal carbohydrate fueling strategies. Targeting 60g carbs per hour on 500mL fluid will work fine for a couple hours.
If targeting 90-130g carbs per hour as is more optimal for most folks’ longest ride efforts, 500mL is going to leave that solution very concentrated and result in GI distress.
You are not going to get the correct answer from anyone here. It is a “It depends” type of answer. Everyone is not the same, and our hydration and nutrition needs are not the same. A lot is learned through trial and error. Your gut is also trainable, and over time you can ‘tolerate’ quite a lot. Go out for a ride of xx distance and measure your hydration and nutrition. Next time, take in a bit more and see what your reaction is - can you tolerate it? Was it too much? Some of the answers can be answered by going to a lab and doing controlled tests, but it can also be done in the field by finding out what your body can adjust to. Sorry to not provide a specific answer, but like many things, it depends.
Hi Maia-long,
Apologies in advanced for the amount of links below, but hopefully you find all the resources below useful.
**Sodium Loss/Replacement: **Without doing actual testing with your sweat, it’s a bit of an experiment. However, at Precision Fuel & Hydration we have taken a lot of real world data we’ve gathered and put it into an online “Hydration Planner”. You can use that tool here:
https://sweattest.precisionhydration.com/pages/why-personalise-your-hydration-strategy
**Fluid Loss/Replacement: **When it comes to the amount of fluid you are losing and needing to replace, we’ve made that a bit easier with an excel sheet and some at home (indoor) or outdoor training you can do to get a better understanding of your fluid loss in different conditions and activity types. https://www.precisionhydration.com/...ure-your-sweat-rate/
**Fueling/Eating: **We’ve recently created a “Quick Carb Calculator” which you can find here, and it will give you a rough estimate of what you’ll need given your activity type and duration: https://www.precisionhydration.com/...l/#thecarbcalculator
While you can’t just copy what other people do, this page can be filtered to show results from long distance triathlons and you can see what kind of ranges fluid/sodium and carbs people take in and the results they get:
https://www.precisionhydration.com/athletes/case-studies/
Most of the athletes used in the case studies follow the “3 levers approach” which we go into a bit more with this blog: https://www.precisionhydration.com/...durance-performance/
Here are the top blogs for hydration and fueling if you’re wanting to dive in deeper:
Hydration:
Why sodium is crucial to athletes performing at their bestHow to estimate how much sodium you lose in your sweatHow to measure your sweat rate to improve your hydration strategyHow to START hydrated and why that’s so importantWhy do athletes suffer from cramp?
Fueling
How much carbohydrate do athletes need per hour?Which energy products are right for you?Does the type of carb in your energy products really matter?How to carb load before your next raceWhat should you eat during the hours before training and races?
Lastly, if you ever want to hop on a call and discuss your hydration/fueling needs, our hydration and fueling experts are always happy to assist. You can book in a call here: https://www.precisionhydration.com/…-video-consultation/
DISCLAIMER: I work for Precision Fuel & Hydration
So it seems it’s a case of just trial and error currently with mostly guesswork surrounding what to take?
But how do I know how much I’m loosing in each ride as surly this varied massively depending on different types of sessions and conditions…? I think I’m a heavy sweater and sometimes get salt lines but that’s all I have to go off currently
Did not know this about carbohydrates though so thank you for the advice!!
So it seems it’s a case of just trial and error currently with mostly guesswork surrounding what to take?
No. There are very well-defined constraints that work for virtually everyone, and operating within them is wise.
It pains me to my soul that every hydration and nutrition thread digresses into “find what works for you through trial and error.”
I’ve posted this list of threads before, so am hesitant to spam it again, but I think it contains a lot of useful info for you. Standing by for questions.
Quick summary:
https://www.trainerroad.com/forum/t/how-are-people-getting-100g-carbs-in-a-bottle/30328/198?u=dr_alex_harrison
1:1 Glucose:Fructose Ratio Works better than 2:1.
https://www.trainerroad.com/forum/t/how-are-people-getting-100g-carbs-in-a-bottle/30328/200
90-150 grams of carbs per hour during exercise may be beneficial. 90 is not the limit.
https://www.trainerroad.com/forum/t/i-carbs-and-so-should-you/33210/583
Sucrose works as well as maltodextrin:fructose, and glucose:fructose 1:1 mixtures. >>90g/hr is optimal
https://www.trainerroad.com/forum/t/how-are-people-getting-100g-carbs-in-a-bottle/30328/204
Isotonicity is not as important as meeting carb and hydration needs. Both can be met with hypertonic solutions, greater than 90g/hr.
https://www.trainerroad.com/forum/t/make-sis-beta-fuel-your-self-just-a-few-pence-per-bottle/16117/282
Detailed how-to guide for intra-workout fueling: (scroll to near bottom)
https://forum.slowtwitch.com/forum/?post=last-7444621#first
Running intra-workout fueling, sweetness discussion
https://forum.slowtwitch.com/forum/?post=last-7417228#first
Really spelling it out: HOW TO:
https://forum.slowtwitch.com/forum/Slowtwitch_Forums_C1/Triathlon_Forum_F1/At-Home_Hydration/Nutrition_for_an_idiot_P7452851/#p7452851
Even more how-to, with savings calculations:
https://renaissanceperiodization.com/expert-advice/saving-money-as-an-endurance-athlete-with-home-made-intra-workout-drinks
You are not going to get the correct answer from anyone here.
Ouch.
This is a good listen and backed by the science:
https://play.acast.com/s/realscienceofsport/thesimpletruthaboutexerciseandhydration
I tend to agree with them. If you are exercising in a reasonably normal environment (i.e. not somewhere really hot, and some access to water/aid stations) you probably don’t need to overthink it. If you are thirsty drink, if not don’t, if you want validation just look at urine colour.
While the idea that 1% dehydration causes catastrophic performance loss (a lot of this idea was developed by drinks manufacturers), there is plenty of research and examples suggesting dehydration is not so bad for performance, and may even improve performance due to weight loss. For example ehydration to the point of around 8% loss in bodyweight is normal in elite marathon runners. (Obviously that rate is not sustainable in triathlon where races are much longer, it’s just to emphasise the point that if you become a little hydrated performance doesn’t nosedive.) The opposite issue of hyponatremia should probably be more of a concern than some dehydration - which can cause death as opposed to just poor performance or a dnf.
Don’t take this to mean that you shouldn’t drink some fluids, or that electrolytes are useless. They certainly aren’t and I would consider using them for longer sessions. But if your training seems to be going ok and your urine is a healthy colour (you can see charts on the internet for what correlates with correct hydration), it might be a case that you don’t need to overthink it. Things like carb intake have a much bigger effect on performance.
But how do I know how much I’m loosing in each ride as surly this varied massively depending on different types of sessions and conditions…? I think I’m a heavy sweater and sometimes get salt lines but that’s all I have to go off currently
Did not know this about carbohydrates though so thank you for the advice!!
Sweat rate varies with thermal stress and effort. More heat & more effort = more sweat.
Salt concentration of sweat varies with effort and sweat rate. More effort & greater sweat rate = higher sodium concentration.
I wouldn’t sweat test. It changes too much with varying conditions, your fitness level, and your hydration level.
How to know how much sweat you’re losing in training: weigh self naked pre- and post-training. Measure how much weight of fluid & solids (if any) were consumed during training. Assume all weight loss came from sweat.
Example:
2 hour session, 200 pounds at start of training, 197 pounds at end of training, having consumed 1 L of water during training = sweat loss of roughly 5 pounds. (1L = 2.2 pounds) 5 pounds in 2 hours = sweat rate of 2.5 pounds of fluid per hour. Or roughly 1.2-1.3 L per hour.
My recommendation would be to use tools and guidance from folks who are not trying to sell you endurance supplements. Those folks may be right and very smart in many cases, but they are less likely to have interests in mind exclusively because they’ve painted themselves into a corner with the specifics of their supplement designs/formulas.
Wow!! Thanks so much, this is incredibly helpful
It all seems quite ‘test and then hope for the best’ at the moment though… Is there a way I can manage hydration during during an event which may be completely different conditions to which I have experienced before? Is it just a case of drinking to thirst?
So it seems it’s a case of just trial and error currently with mostly guesswork surrounding what to take?
No. There are very well-defined constraints that work for virtually everyone, and operating within them is wise.
It pains me to my soul that every hydration and nutrition thread digresses into “find what works for you through trial and error.”
I’ve posted this list of threads before, so am hesitant to spam it again, but I think it contains a lot of useful info for you. Standing by for questions.
Quick summary:
https://www.trainerroad.com/...8?u=dr_alex_harrison
1:1 Glucose:Fructose Ratio Works better than 2:1.
https://www.trainerroad.com/...n-a-bottle/30328/200
90-150 grams of carbs per hour during exercise may be beneficial. 90 is not the limit.
https://www.trainerroad.com/...should-you/33210/583
Sucrose works as well as maltodextrin:fructose, and glucose:fructose 1:1 mixtures. >>90g/hr is optimal
https://www.trainerroad.com/...n-a-bottle/30328/204
Isotonicity is not as important as meeting carb and hydration needs. Both can be met with hypertonic solutions, greater than 90g/hr.
https://www.trainerroad.com/...per-bottle/16117/282
Detailed how-to guide for intra-workout fueling: (scroll to near bottom)
https://forum.slowtwitch.com/...t=last-7444621#first
Running intra-workout fueling, sweetness discussion
https://forum.slowtwitch.com/...t=last-7417228#first
Really spelling it out: HOW TO:
https://forum.slowtwitch.com/...t_P7452851/#p7452851
Even more how-to, with savings calculations:
https://renaissanceperiodization.com/...intra-workout-drinks
Thanks Alex!! Your carbohydrate information is so useful - do I not need to worry about electrolytes though…? One of my biggest fears is cramping on race day and it spoiling the day. Can I just take a single electrolyte tablet in every bottle and I should be okay?
Standing by for questions.
Dr. Harrison!
Thank you for your breakdowns.
One question I had was regarding the fructose+maltodextrin vs sucrose:
I get the osm of the sucrose mix is going to be lower. But is there information on whether we are limited in sucrose breakdown (i.e., vmax of sucrase)? Is optimal somewhat of a mix of sucrose, fructose, malto? Or is sucrose broken down so quickly that this is a non-issue?
Thanks
Standing by for questions.
Dr. Harrison!
Thank you for your breakdowns.
One question I had was regarding the fructose+maltodextrin vs sucrose:
I get the osm of the sucrose mix is going to be lower. But is there information on whether we are limited in sucrose breakdown (i.e., vmax of sucrase)? Is optimal somewhat of a mix of sucrose, fructose, malto? Or is sucrose broken down so quickly that this is a non-issue?
Thanks
I don’t have that specifically re: sucrase, but there is data from Jeukendrup in early 2000’s I believe, (don’t have it handy) have data showing very high rates of exogenous carb utilization with sucrose ingested at 120g/hr. Same as if dextrose+fruc or malto+fruc.
Thanks Alex!! Your carbohydrate information is so useful - do I not need to worry about electrolytes though…? One of my biggest fears is cramping on race day and it spoiling the day. Can I just take a single electrolyte tablet in every bottle and I should be okay?
500mg/L is a good starting place. Lots of folks target 1000-1500 if they’re sweating heavily. Some even higher.
Sodium Citrate is useful. (no affiliation)
Repost of canned text from another thread: Using sodium citrate in place of table salt allows your gut to tolerate more sodium consumption during training. Sodium citrate has 3 sodium molecules for every 1 citrate molecule. Sodium chloride has 1 sodium molecule for every 1 chloride molecule. That means that for the same amount of sodium consumption, there will be a greater number of molecules ingested, if using table salt, rather than sodium citrate. Osmolarity is the number of molecules per unit volume of solution. Our gastrointestinal tracts are sensitive to very high osmolarity solutions. During normal daily living, consumption of very high osmolar solutions (lots of molecules per liter) causes a laxative effect 20-60 minutes after consumption. During exercise, it causes gut cramping, THEN a laxative effect. My personal experience with this can be described as “not fun!”
If you weigh before and after, you will know how much water is lost over the workout despite your drinking. Pints a pound. You can only absorb so much, so drink early when it’s hot, for a long, long race you need to get some salts back or risk hyper hydration. I ended up in a coma from that in a long bike race in the tropics. You feel like you have heat stroke and drinking more seems like the best bet, avoid the whole post race coma if possible
For older athletes the “thirst response” can be inadequate.
Something most people (including me) forget when we talk about “drink when you are thirsty”
You are not going to get the correct answer from anyone here.
Ouch.
Guess that does sound a bit harsh. What I was implying is there is no ‘one size fits all’ approach. There is no one answer. There are guidelines, as have been provided as starting points, so you aren’t completely guessing. I hope the OP is able to find what works optimally for them.