Fueling guide
Sweat rate and hydration: what the research says
Sweat rates differ a lot between athletes and conditions. Position stands use a loss of more than 2% of body weight as the line above which endurance performance tends to fall.
They also warn against drinking more than you sweat. A sweat test, two weigh ins around a session, shows your own rate.
Your AI can store the test and turn it into a fluid plan for each session.
What position stands say
The NATA and ACSM statements on fluid replacement describe drinking to limit body mass loss, using 2% as the line. Without a measured sweat rate, the research falls back on drinking to thirst.
A consensus statement on exercise associated hyponatremia warns that drinking more than the body loses can dilute blood sodium.
- Under 2% body weight lost over a session is the line used.
- Never more fluid than you sweat.
- Sodium from about 300 to 1,000 mg an hour in long events, higher in heat or for salty sweaters, as a range used in the reviews.
Why your own number beats an average
A review of sweating rate and sweat sodium shows large differences between people and from day to day. Heat, humidity and effort all change it.
So the research favors testing in the conditions you race in.
How a sweat test works
Weigh yourself before and after, without clothes. Add the fluid you drank, subtract urine, and divide by hours. One kilogram lost counts as about one liter of sweat.
Run it a few times and in different weather. The Sweat Rate Calculator does the arithmetic.
In your AI
The AI you already use, with your data in Memory.fit.
- ChatGPTChatGPT plans your week, fuels your long sessions and writes it all back to Memory.fit.Set up ChatGPT
- ClaudeClaude writes your plans back to Memory.fit, and asks you before it replaces or removes something you have.Set up Claude
Grok BotGrok Bot plans and reviews from your real training, and can re-plan a week after a bad night's sleep.Set up Grok Bot
MuseMuse plans sessions from your real training and writes them into Memory.fit's Plan.Set up Muse
DotsOpenAI says a dot's background research uses your connected apps read only, so plans are written when you ask in the chat.Set up Dots- GeminiType @ in a Gemini chat and pick Memory.fit to ask about your training. Gemini asks you to allow each session it plans, and planning a whole week is not reliable yet.Set up Gemini
- GrokGrok reads your training, sleep and fuel, and can plan around them.Set up Grok
- Perplexity ComputerPerplexity Computer reads your training in Memory.fit. Whether it writes a plan back isn't checked yet.Set up Perplexity Computer
- Claude CodeClaude Code reads your training and writes the sessions it plans back to Memory.fit, asking before each change unless you allowed it.Set up Claude Code
CueYour Cue agents plan your week and write your fuel plans from your real training, sleep and recovery.Set up Cue
What to send
Copy one, send it to your AI.
“Here is my sweat test: 75.0 kg before, 74.2 kg after, one hour, 500 ml drunk. Log it in Memory.fit.”
Tools:
log_sweat_test“I drank two bottles on my long ride today. Log both in Memory.fit with the sodium in my drink mix.”
Tools:
log_drink“Use my sweat tests in Memory.fit to write the fluid and sodium part of my fuel plan for the hot long run on Sunday.”
Tools:
get_fluidset_session_fuel_plan“Set my fluid target for race day in Memory.fit from my sweat rate and the weather forecast.”
Tools:
get_weather_forecastset_day_targets
Questions
In short.
Reviews report a wide spread between athletes, so an average is a weak guide. A test gives your own number.
The NATA and ACSM statements use it as the line above which endurance performance tends to drop.
Yes. The hyponatremia consensus statement links drinking more than you lose to low blood sodium.
Reviews say sweat rate shifts with heat and effort, so a test in race like conditions is the useful one.
Yes, a review shows large differences between people in sweat sodium concentration.
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