Hydration deficit. What's my next move?

Tl;dr If I know I’m getting dehydrated and I know I’m drinking at my bodies ability to absorb and I know I’m pacing within/under my bodies theoretical ability for the targeted duration… how do I further improve or limit the negative impacts resulting from a hydration related imbalance when I’m deep into my targeted event, but still have a long ways to go?


I’m fairly certain that after looking at all the possible elements that make up a “good day on the bike” that my biggest performance gap/opportunity for improvement is staying hydrated/hydration related.

I’ve done several sweat rate assessments and have identified that I can sweat anywhere from 40-70 oz per hour, depending on intensity and temp, and between 50-60 oz per hour around 65-70% of FTP at 70°f.

My ability to consume/absorb is around 35oz/hr and seemingly diminishes over time, so I almost always run at a modest hourly deficit and depending on duration this can cause significant and sometimes insurmountable challenges.

My target event is going to take me ~17 hours to finish, which even at a very modest intensity, puts me in the hurt pretty deep for perhaps as many as 7 hours based on my current conditioning, even while keeping a lid on intensity.

Fueling: I take in all my carbs in liquid form. Almost always tailwind (after trying several products), feeding via slurry out of a single bottle. The rest of my bottles are always plain water. I can consume up to 200-300 cal/hr or between 50-75g carb/hr without distress. I’ve mixed across all bottles before but struggled w/ being able to quench a thirst/dehydration since my sweat rate can vary so significantly (cramps, failure have always resulted) .

Effort: My ftp floats anywhere from 275-305 and puts my theoretical “all-day power” between 165w and 200w. Below is a recent example (fairly worse than average, but a good example none-the-less) however I can typically make it up to 9.5-10hrs (@~180w, ~130bpm) before coming completely, spectacularly unglued. What I’m attempting to illustrate here is the uncoupling of hr from effort, nothing more.

90°f, 160 miles, 11.2hrs 20° temp swing over ride duration.
Average power/hr: 126w & 129bpm.
Hour 6 started to come a bit undone, rested briefly.
Hour 9 effort became completely uncoupled from hr.
I’m almost 100% certain that (the collapse) is hydration related, despite fluid consumption at the highest rate my current ability to consume allows.
Rest. Periods**

30 min splits:

  • 109w / 113bpm -4
  • 118w / 116bpm +2
  • 142w / 121bpm +21
  • 130w / 121bpm +11
  • 157w / 130bpm +27
  • 129w / 127bpm +2
  • 154w / 121bpm +33
  • 155w / 134bpm +21
  • 135w / 135bpm 0**
  • 140w / 135bpm +5
  • 142w / 137bpm +5
  • 101w / 125bpm -24**
  • 109w / 124bpm -15
  • 152w / 126bpm +26
  • 119w / 134bpm -15
  • 131w / 135bpm -4
  • 167w / 151bpm +16
  • 115w / 143bpm -28**
  • 131w / 144bpm -13
  • 62w / 120bpm -58
  • 76w / 118bpm -42
  • 89w / 127bpm -38
  • 51w / 116bpm -65

So what do you think/recommendations? What’s my next move?

I will tell you that once hr uncoupling occurs, the odds of me quitting are pretty high. Whole body cramping is usually imminent, and my resolve pretty much evaporates. Mental picture: pre-decoupling eta = 2hrs, post-decoupling eta, 4-6 hrs, once I figure that I have 2-3x my time to destination, likelihood of giving up is very high. I realize that I need to work on my “mental strength/endurance mindset” but at the same time I’ve also accepted that willpower alone is sometimes not enough.

Try putting electrolytes (no carbs) into your plain water bottles.

Or move to a colder, wetter place.

Electrolites are your friends…

you will need more salt to keep the water down on hot long rides…
Nuun is a good alternative…
has 0 calories…is basically salt…
you can also go with salt tabs…

you can also go with more endurance drinks like gu roctane and things like that…
the rule of thumb…is one bottle per hour… on races…
on easier things…depending on heat you may drink less… but be aware that you might need to drink more often that you feel…

Race cyclocross…don’t even need bottle cages :+1:


I am an Audax rider, I used to find at 250km into an event… i was blowing up. I did the same as you most of my carbs was water based. I started adding electrolytes and saw an improvement. I Then started solid foods at the start of my events it does mean carrying some rolls and cheese and jam all wrapped in clingfilm. I recently watched the Precision Hydration Blog on TR and purchased the product. Not raced with yet but is okay. You can salt load the Night before and on the morning of your event, seems like something to give a try. I am going to do so for the 12hour + events.