I had an eye on it for some time. Now they launched.
Sweat rate and sodium loss sounds interesting to measure, but not sure I really need it. Also live data streaming to a head unit hasn‘t been developed yet (they say it‘s coming). Also looks like a first product and small company.
Do you think the sensor is worth it?
I’m intrigued by it, I’ll say that. Whether it’s worth it… is a question.
I’ve been using an HDrop and it’s been so so. doesn’t have some switches I’d like to see. For example I don’t care about potassium intake during a ride/race, as well as the drink prompt field via Garmin IQ hasn’t worked, so I’ve just been using Saturday AM and Garmin Smart drink to get things dialed in.
Sounds interesting, and I have the same question as others about its value over time.
While researching my sweat rate and required sodium intake, I found an interview with Matteo Jorgenson, who previously had issues with high sweat rates and/or high sodium loss. From what I recall, this was something that he had tested through the Movistar team doctors, and they adjusted his sodium intake accordingly. He made it sound like it was not something that required constant monitoring and adjusting but something one can test for and know going forward. Within a range of training and racing conditions, I imagine.
Didn‘t know about that one. It is cheaper and looks more developed!
I’ve always been interested in my sodium loss and also have researched it but couldn’t come up with anything solid I could use. As I remember it, it seems the saltiness and amount of perspiration varies quite a bit between individuals so without testing there was no easy way to know. I do know I’m heavy sweater and have always craved salt but try to limit my intake to a reachable amount so I always end up guessing.
Save your money. Patches are not the way to go, as 1) sweat rate and composition varies on different points on the body, and 2) patches alter the local response.
Here are my unscientific results from doing 4 tests.
Workout: Threshhold
Time: 2 hours
Temperature: 52-55(F)
Fluid intake: 1420 ml total
Same bike, same garage, same rider, different TR workouts but all the same type.
Test method:
Test Results (average loss /hour):
Based upon 4 tests (where I could get all the tech to work at the same time {specifically issues with the Nix sensor}) the Garmin calculated sweat rate loss was the closest to actual loss with the weight scale. Nix and H-Drop were way over and would be too much fluid for me to intake while riding. Other issues is that while the Nix app does have a Garmin data field it rarely (if ever) works for me. H-Drop same thing, have the data field but no information. Nix App and sensor connection is finicky and i’ve wasted a lot of patches due to connection issues. My process now (with 90% success rate) is:
Again this is just my results from 4 tests where I could get all the tech to actually work and recorded. All said and done do a weight scale test and compare it to your Garmin head unit calculation to get you closer to the pin than what is calculated by H-drop or Nix.
I think knowing your Sodium Loss / L is extremely valuable, regardless of how you get there, but it also doesn’t need to be exact. I used an HDrop in Hot / Representative conditions, and took an average. Then, Did a whole heck of a lot of rides where I hydrate at that sodium concentration per L of fluid. Haven’t had an issue that I could pin on sodium yet. I’m going to re-verify when it gets warm out again using the Gatorade patches.
I don’t use or trust them for Sweat Rate / Sweat Volume though. Much more reliable to use a scale and take notes for different temps and humidity. (Start stark naked, weigh yourself holding your bottles. Go bike for an hour or more. Come back and weigh yourself stark naked with your bottles and whatever’s left in them for fluid. No peeing or weight doesn’t count)
Then, sodium intake is always per L (not per hour) and liters of fluid per hour is based on bodyweight testing under different conditions.
From the Flowbios website:
“90% accurate in lab based conditions…83% for sodium, 73% for fluid loss in the field.”
I missed this thread earlier. Just read a review. This is interesting to me because it provides actionable feedback.
Has anyone actually used the S1 sensor by now and can share some impressions / buying advice?
Just picked up all three sweat trackers, Nix, hDrop, and Flowbio. Gonna put them through some real-world tests and share how they stack up in the next few days. I’m lucky to know someone nearby who runs precision hydration testing, so I’ll try to throw that into the mix too. This summer I’m going all in on dialing in my hydration.
Good morning folks! I have started testing this week with Hdrop, Flowbio, Nix, and Precision Hydration tests against sweat losses (lab grade scale) and sweat sodium concentration (Precision Hydration Sweat test). These were my preliminary results (more to come next week until I ran out of Nix patches - i got 12), some numbers are sightly rounded:
| Trial | Device | Pre-weight (kg) | Post-weight (kg) | Device sweat-loss (kg) | Weight accuracy (%) | Measured [Na⁺] (mg /L) | Na⁺ accuracy (%) | Status |
|---|---|---|---|---|---|---|---|---|
| 1 | HDrop | 75.0 | 74.4 | 0.56 | 94 | 998 | 95 |  |
| FlowBio | 75.0 | 74.4 | 0.73 | 78 | 840 | 80 | |
|
| Nix | 75.0 | 74.4 | 0.76 | 72 | 735 | 70 | |
|
| Precision Hydration (Lab) | – | – | – | – | 1 050 | 100 | Reference | |
| 2 | HDrop | 74.8 | 74.3 | 0.54 | 92 | 1 070 | 93 | |
| FlowBio | 74.8 | 74.3 | 0.400 | 80 | 1 220 | 78 | |
|
| Nix | 74.8 | 74.3 | – | – | – | – |  (patch lost) |
|
| Precision Hydration (Lab) | – | – | – | – | 1 000 | 100 | Reference | |
| 3 | HDrop | 75.1 | 74.6 | 0.45 | 90 | 986 | 88 | |
| FlowBio | 75.1 | 74.6 | 0.59 | 82 | 920 | 82 | |
|
| Nix | 75.1 | 74.6 | 0.39 | 78 | 1 360 | 78 | |
|
| Precision Hydration (Lab) | – | – | – | – | 1 120 | 100 | Reference |
I cleaned the data and compare it with the precision hydration tests that I did (looking like a cyborg LOL), and a friend of mine helped me convert values measured on ventral forearm for whole body sweat sodium concentration. Highly impressed with the Hdrop so far. The nix one failed once, maybe due to the length of my activities. I will try longer activities next week. Flowbio does not provide live data and I have the feeling that the hole will eventually get clogged, potentially causing innacurate data, given how off it is right now, we will see over the next few weeks. Something to take into account to is the precision of the scale, I haven’t had too much time to crunch more data yet, but will try including some of my thoughts later on about scales.
This whol testing takes a lot of time…(had to rescue a Garmin watch because flowbio does not work standalone, I also had to use an ipad bc flowbio does not have an android app, weighting, not drinking to keep numbers straight…) and will likely slowdown over the next weeks due to work, but I am having fun with it and learning quite a bunch. Overall, these sensors seem to be on the right track for being useful, and I will start adjusting fluid and sodium intake soon. A couple of you reached out to me for the real-time tracking and some additional features these gadgets have, so I will also try to report on it later on.
As for aggregate numbers, the best sweat sensor for hydration tracking so far seems to be hdrop:
| Device | Weight-accuracy (%) | Na⁺-accuracy (%) | Trials included |
|---|---|---|---|
| HDrop | 92 | 92 | 3 |
| FlowBio | 80 | 80 | 3 |
| Nix Biosensor | 75 | 74 | 2 |
But I will keep testing! I will also try different intensities next week, I am also interested on the regular precision hydration test (the one where you do not exercise) and compare it with the real exercise sweat samples, I get the sense that the sodium losses increase/decrease depending on the intensity of the activity, weather conditions…so I am not sure how a single pilocarpine test can be good enough. Will report findings on that side too, but again, this will take some time.
Thanks for reading my TedTalk LOL 
hDrop just did an update where you can add calibration info by doing a 30-60 minute test. Weigh before, input into hDrop, workout, weigh after, input into hDrop to calibrate sweat rate.
I have not done this yet, but will see about fitting it in next week.
Interesting! I guess I missed this during the onboarding or something. Seems like a good way to calibrate it against weight in and weight out for sweat rate. It says it should be used if your data is off…Mine seems to be pretty good so far, if I see a decrease in performance, I will test that too!
Also, anyone having problems with the Nix patches? Any tips on making those not to fail? Quite frustrating…I will try longer activities next week.
Thanks for the testing, @jack14i2!
hdrop indeed looks quite promising - for aggregating the results, might be interesting to also show if some sensors are consistently reading higher or lower. For example, FlowBio being 20% seems pretty bad, but even more so when you realize it’s 2 are 20% below reference, the other is 20% above reference.
@trailhead Indeed! Once I finish with all the tests, I will try to provide the reliability metrics (I think this is what you are referring to) for each device.