It’s been a while, and I owe you the results. 
| Trial | Device | Pre-weight (kg) | Post-weight (kg) | Device sweat-loss reported (kg) | Weight accuracy (%) | Measured [Na⁺] (mg/L) | Na⁺ accuracy (%) |
|---|---|---|---|---|---|---|---|
| 1 | HDrop | 75.0 | 74.4 | 0.56 | 94 | 998 | 95 |
| 1 | FlowBio | 75.0 | 74.4 | 0.73 | 78 | 840 | 80 |
| 1 | Nix | 75.0 | 74.4 | 0.76 | 72 | 735 | 70 |
| 1 | Precision Hydration (Lab) | - | - | - | - | 1050 | 100 |
| 2 | HDrop | 74.8 | 74.3 | 0.54 | 92 | 1070 | 93 |
| 2 | FlowBio | 74.8 | 74.3 | 0.40 | 80 | 1220 | 78 |
| 2 | Nix | 74.8 | 74.3 | - | - | - | - |
| 2 | Precision Hydration (Lab) | - | - | - | - | 1000 | 100 |
| 3 | HDrop | 75.1 | 74.6 | 0.45 | 90 | 986 | 88 |
| 3 | FlowBio | 75.1 | 74.6 | 0.59 | 82 | 920 | 82 |
| 3 | Nix | 75.1 | 74.6 | 0.39 | 78 | 1360 | 78 |
| 3 | Precision Hydration (Lab) | - | - | - | - | 1120 | 100 |
| 4 | HDrop | 75.2 | 74.5 | 0.66 | 94 | 905 | 92 |
| 4 | FlowBio | 75.2 | 74.5 | 0.85 | 79 | 1250 | 72 |
| 4 | Nix | 75.2 | 74.5 | 0.40 | 57 | 1010 | 97 |
| 4 | Precision Hydration (Lab) | - | - | - | - | 980 | 100 |
| 5 | HDrop | 74.9 | 74.2 | 0.64 | 91 | 940 | 92 |
| 5 | FlowBio | 74.9 | 74.2 | 0.55 | 79 | 1380 | 65 |
| 5 | Nix | 74.9 | 74.2 | 0.95 | 64 | 760 | 75 |
| 5 | Precision Hydration (Lab) | - | - | - | - | 1020 | 100 |
| 6 | HDrop | 75.3 | 74.6 | 0.62 | 89 | 1045 | 95 |
| 6 | FlowBio | 75.3 | 74.6 | 0.90 | 71 | 1550 | 59 |
| 6 | Nix | 75.3 | 74.6 | - | - | - | - |
| 6 | Precision Hydration (Lab) | - | - | - | - | 1100 | 100 |
| 7 | HDrop | 75.0 | 74.1 | 0.78 | 87 | 1085 | 94 |
| 7 | FlowBio | 75.0 | 74.1 | 0.60 | 67 | 1700 | 52 |
| 7 | Nix | 75.0 | 74.1 | 0.50 | 56 | 1420 | 77 |
| 7 | Precision Hydration (Lab) | - | - | - | - | 1150 | 100 |
| 8 | HDrop | 74.7 | 74.2 | 0.48 | 96 | 890 | 92 |
| 8 | FlowBio | 74.7 | 74.2 | 0.72 | 56 | 1750 | 20 |
| 8 | Nix | 74.7 | 74.2 | 0.30 | 60 | 930 | 96 |
| 8 | Precision Hydration (Lab) | - | - | - | - | 970 | 100 |
| 9 | HDrop | 75.4 | 74.8 | 0.55 | 92 | 1130 | 94 |
| 9 | FlowBio | 75.4 | 74.8 | 0.95 | 42 | 1950 | 38 |
| 9 | Nix | 75.4 | 74.8 | 0.55 | 92 | 1650 | 62 |
| 9 | Precision Hydration (Lab) | - | - | - | - | 1200 | 100 |
| 10 | HDrop | 75.1 | 74.3 | 0.74 | 92 | 980 | 93 |
| 10 | FlowBio | 75.1 | 74.3 | 0.40 | 50 | 2100 | 0 |
| 10 | Nix | 75.1 | 74.3 | 0.60 | 75 | 520 | 50 |
| 10 | Precision Hydration (Lab) | - | - | - | - | 1050 | 100 |
Alright, these are the final results so far. Sorry it took a while and it takes so long to run these.
Overall results:
| Device | Trials with sweat-loss data | Avg sweat-loss accuracy (%) | Trials with Na⁺ data | Avg Na⁺ accuracy (%) |
|---|---|---|---|---|
| HDrop | 10 | 91.7 | 10 | 92.8 |
| FlowBio | 10 | 68.4 | 10 | 54.6 |
| Nix | 8 | 69.3 | 8 | 75.6 |
Some of my thoughts:
Surprised about the consistency of the HDrop and the data it provided (plus it is reusable).
Nix is mid due to the patches, we got them working better and more consistently, but not a fan.
FlowBio has been the worst, the sodium concentration seems to increase overtime, even though I tried cleaning the hole where your sweat flows, I think it has salt built up inside and it just gets readings that are increasing over time. I would not trust it. It may have been good at the beginning, but over time it’s accuracy went down. I find it bold for FlowBio to be claiming to be the most accurate sweat sensor…
Conclusions:
After doing a lot of testing, I will likely stick with the H-drop for now, using it every two weeks or so for checks. I have adjusted my hydration plan, and I am planning on testing different weather conditions (all the tests were done indoors) and different activities/intensities. I have worn the Hdrop on some of my outdoor rides and it seems to show different readings depending on the intensity I put it, so that would be a cool unofficial testing. I think these sensors are decent to get a better idea of fluctuations and seasonality and to adjust my drinking and sodium intake behaviors accordingly.
And with that, closing the loop! Been a fun study and I am now moving to a new house, so my testing will likely stop for a long time (reconstructing too!). Time to set my new pain cave 