I heard on the the Podcast some research about the sodium intact for an average Athlete. Does anyone recall the mg per hour?
An average value is ~300-600 mg of sodium per pound of sweat. However, that average is resultant from individual values of ~230 mg - 1,300+ mg. Sodium loss is HIGHLY variable between individual athletes, and while the 600 mg value can be a good starting point, operating with any specificity in your nutritional/fueling approach without more accurate quantification may not result in optimal hydration strategies.
Precision hydration have a useful online tool to get a starting point for sodium, water and carbohydrate needs during exercise. They’re ultimately trying to sell product so might be biased to the upside but I found it very helpful in preparation for my upcoming Ironman. As someone who rarely if ever replaced electrolytes during rides in the past (and a heavy/salty sweater) I found that by consuming around 1300mg per hour as per their recommendation I was able to much more easily hold power and delay the onset of fatigue during long tempo or z2 rides.
The tool is available here for free: https://www.precisionhydration.com/planner/
1 Like
There has been a number of developments that have occurred in terms of sodium intake during endurance sports. First was the recognition of the importance of sodium and including it in what athletes are drinking during activities. Another was the acknowledgement that different athletes have different sweat rates and sodium content in their sweat. Third, is that the sweat rate and sodium content of an individual athlete can also be quite variable, so just because someone tested at a certain level of sodium at one point, doesn’t mean that that won’t change in the future.
The other major piece of the puzzle is what your gut can handle in terms of sodium intake. Hypotonic fluid is going to be the easiest to absorb in the gut. As you raise both the sodium and the carbohydrate content, the tonicity is going to increase and it starts to become harder to absorb the fluid. Increase it further and the fluid may begin to preferentially stay in the gut as it becomes hypertonic. The can lead to that bloated sloshy feeling.
Skratch Sports Hydration mix is hypotonic and has 380mg of sodium (as sodium citrate which tends to be easier on the gut compared to sodium chloride) per scoop which is intended for about 500mL of fluid. That’s a pretty good starting point. If you are a salty sweater you can try to add additional sodium but if you start to feel bloated/sloshy, then you may need to back off.
Duration of events is also a key consideration. What you can tolerate for 1 - 2 hours may be very different than what you can for 6 - 8 hours.
This is going to be an interesting space to watch as more research is done. I think we are going to learn that simply blindly trying to replace sodium 1:1 to sweat rate is likely not going to be ideal for a lot of people, although it may work for some.
1 Like
Thank you. I have been drinking LMT in the am and during rides. I live in TX and the heat has been oppressive so finishing before 11am has been key. Thank you all.
2 Likes
Are you saying that water with a higher concentration of salt can lead to bloating as it’s harder for the body to absorb?
I’ve anecdotally heard the opposite - namely that without consuming sodium it can be difficult to continue to digest carbs via gels during long efforts. I don’t have a view myself but trying to understand the dynamics a bit better. I’m doing an IM on Sunday hence the particular interest in order to minimise the risk of stomach issues 
To add to that, the only way to really accurately quantify sweat electrolyte concentrations and hence loss is the whole body wash down method. Sweat rate and electrolyte concentrations vary at different points on the body, and patches alter the local response.
1 Like
Check out the “Saturday” app from @Dr_Alex_Harrison. It has a pretty good guideline that can help you prep for your rides. Not sure where you are in TX, but since Houston is abnormally humid, I found that I had to bump up the sweat rate a notch in the tool to get accurate predictions.
Every individual is different, but for me, as a basic guideline, in summer I tend to use a single SIS tab per 45-60 minutes indoors (350mg per tab), a Precision Hydration 1000 tab (500mg) per hour outdoors if riding really early (say 5-8am) and a PH1500 tab (750mg) per hour if I’ll be out after the feels like hits 90+. If I’m doing something extremely difficult indoors, I’ll bump up to a PH1000.
In winter, I’ll only use the SIS and PH1000.
1 Like
So you definitely need some sodium, both to replace losses but also to help with co-transport of glucose in the gut (sodium-dependent glucose co-transporters).
What I was eluding to above was move related to the concentration of the solutes in the solutions you are drinking, basically how concentrated are the salts and sugars in the solution. As you add more salt and sugar to the solution, the tonicity will go up. It’s generally easiest for you body to absorb hypotonic fluid in the gut as it follows the concentration gradient. Skratch, which still has 380mg of sodium per bottle but is lower in carbs, is hypotonic. Isotonic can be ok too but tend not to absorb as quickly. Regular Gatorade would fall into the isotonic category. If you start to load a lot of salt in the water, plus add a lot of carbs to the solution, then things can get hypertonic, which is not going to be absorbed as well. You all need to consider if you are eating other things at the same time you are drinking, because it all mixes together and impacts things.
My own experience is in really long events, like Unbound or Leadville, its really important to have this dialed. What you can get away with over 3 - 4 hours might be very different than what you can handle over 8 - 9 hours.
1 Like
thanks for the explanation
IMO, Per Hour is not the right way to look at it. Better to look at it as sodium per Liter of fluid, because your per hour varies greatly based on conditions, but it shouldn’t vary much per liter you sweat out and take in.
I’ve heard 600-2000+ per liter, and based on the limited sweat testing I’ve done I’m around 1200.
One article here
We’ve tested athletes who lose less than 200mg of sodium per litre (32oz) of sweat and we’ve also seen [athletes losing well over 2,300mg per litre. Our data suggests the average athlete loses around 950mg/l and this tallies with other large scale studies.
1 Like
The higher your sweating rate, the lower the sodium concentration, as there is less time for reabsorption in the sweat duct.
1 Like
Didn’t know that, but not surprising. But at the same time, the variability is MUCH higher when you’re talking about fluid loss. If someone takes in 1000 mg an hour and they’re not sweating at all because it’s in the high 30’s and cloudy at the beginning of a race that could mess you up… My practical per hour needs are basically zero, to 1500 mg or more.
If you test and try your sodium intake (per liter) at different temperatures, then you just set it and vary the fluid amount. For example, I’ve done everything from that high 30’s to 90’s and humid on the same sodium concentration per liter, and just vary the amount I drink.