How Far Can I Run in 24-Hours? Episode 5: Sweat Testing for Runners and Sodium Concentration!

[@nifty404]

Very insightful! I feel this is the last missing puzzle piece I’m trying to sort out for racing. Doing it trial and error just takes so long, and it sucks! Hopefully similar services are also available in other states (and countries)!

[@svenja5596]

Super interesting! Hope this will help you avoid GI distress in the future!

[@Valaran1]

I just got a sweat salinity test from Dina last week, after seeing your short. Thought I was a salty sweater, turns out I'm actually low at ~550 which is ideal for longer distances. I love data, and I appreciate you sharing all this with us for free. Dina was wonderful and I would recommend this to anyone.

[@Vo2maxProductions]

So awesome! Thanks for sharing!

[@WilsonJoey]

Nice work. I'm excited to see how this info helps you in your upcoming 24 hour! Good luck brother!

[@Vo2maxProductions]

thanks! The logistics of the 1-mile loop course (and not having to carry all this fluid and gels in a pack as I run) makes it totally different in mindset and strategy compared to a mountain-trail-ultra!

[@Davidvanderwaal]

Love the channel Sage. Sweat testing is something that interests me a lot ! On the topic of testing (Not sure if this is the right channel to propose a Training Talk Tuesday topic so I apologise in advance if inappropriate!) I’m a 40yo recreational runner who’s run consistently since high school with a ½ mara PR (1:22) mara (2:59). My HRmax recorded this year is 184bpm taken over a 10km TT (avg HR 180bpm), I also ran my ½ mara at 178bpm (avg 97% HRmax) and marathon at 168bpm (avg 91%) which are well above HR zone ranges you have published on your Intensity Spectrum Chart. To add context, these HR intensities are consistent with what I’ve run in previous years. Last year, I had my blood lactate measured where my LT1 was measured at 155-160bpm and LT2 175-180, again they are higher than your intensity spectrum indicates they should be and consistent with the HR averages I typically post across all distances (Mara-5km max efforts). In terms of RPE, 155-160bpm is comfortable & conversational to me, is it possible to be training in an “easy/aerobic base building” when my heart rate is this high (84-87% HRmax)? My avg HR/blood lactate levels and RPE suggest the intensity is correct, but I’m not convinced - one explanation could be that my HRmax is higher than I’m aware of but I’m wondering whether there could be an underlying issue with my physiology? Do you think I should change my approach and ease off on my HR zones regardless of the physiological responses I’ve recorded?

[@Vo2maxProductions]

Hey thanks. I'm going to keep this short: I don't think your 100% max HR is 184 (it's really hard to get a 100% reading during a 10km regardless). It's likely a much higher value. It's also basically impossible to race an entire half marathon at "97% of max HR"....essentially only pros (running a half in 60-min for faster) can hold maybe up to 94% of max for a half marathon....but only because it's a 60-min effort. So all your HR numbers seem off (except the lactate ones make sense..probably because they are using lactate values. LT2 should be closer to 85-90% of max HR...so if it's reading 175-180 that's likely under 90% of your max.). I'd guess then your true Max HR is actually closer to 200. I'd get a real Vo2max test (should be less than 10-12min) in a lab and try to pull out a higher HR value reading....(it's very, very hard to do!).

[@Davidvanderwaal]

@@Vo2maxProductions Thanks Sage I appreciate you getting back to me. I was planning to sweat test in the new year, I will get that V02max test done too. I actually have seen readings higher than 184 bpm in the past but they are so few and far between I've always put them down as outliers/inaccurate readings. If I re-map my zones based on 200bpm maxHR it all makes a lot more sense.

[@joemoya9743]

The only issue I found with sweat testing is that if you consume more salt, it registers you having higher salt in your sweat and vice versa. Same for fluids, if I drink more water it will show lower salt in the sweat even though you consumed the same salt in the same environment. So, the point I am making is that doing the test once may or may not be showing accurate results but in all likelihood it will be good enough. However, where sweating testing does become more valuable is in extreme dry heat or humid conditions. Testing specifically in those environments have helped me the most in determining my salt and fluid intake amounts. (BTW, I own my own sweat testing device so I was able to do many tests to verify the different results in different environments over a period of time).

[@Vo2maxProductions]

yeah leading into the test you weren't supposed to do any crazy long runs or running workouts (to help keep the results consistent). I also didn't change my usual diet (i.e. no Taco Bell 50km right before!) or hydration patterns (i.e. didn't drink more or less than usual). So it was to help ensure there is a a consistent baseline (as she said it's 85% genetic and doesn't really change too much over the years). In my blood panels I also do the same thing (i.e. taper off an iron supplement before getting an iron test for ferritin). For sure someone chugging a gallon of plain water can cause them to go hypornatremic pretty quickly. What kind of personal sweat testing device do you have? v

[@joemoya9743]

@@Vo2maxProductions I have used two. Liipoo AbsolutSweat Hydration Biosensor and hDrop Hydration Monitor. I like the hDrop better. It doesn't use patches and it is more portable but both are good. However, I am not certain how durable and accurate the hDrop will be over time since your are using the same sensor for each reading (no patches).

[@markuscg1]

I went to Dina several years ago to get some sweat testing done. Provided some interesting insights.

[@Vo2maxProductions]

great to hear!

[@michaelaustria208]

💙🌱💙

[@Deadbuck73]

Good Morning!

[@gpfraser1]

Is it a good thing to be a heavy sweater? I sweat basically a minimum of 40 oph, and it can get as high as 100 oph in the summer.

[@Vo2maxProductions]

I'm assuming oph is "ounces per hour"? I think it depends on the sodium concentration as well. Also, what % of total body weight the fluid represents.For me, losing 9-10lbs for a 9 hour effort at the Tarawera 100km it was one 6% of my total body weight it seemed to be very bad for my performance (I was walking and super weak and my stomach was horrible the last 20-miles). But for certain ultra races it can also be harder to carry that much (extra weight of fluid) as even 1L or 34oz of water weighs over 2lbs....it could (I suppose) change strategy where you also focus on "chugging more fluid and drinks" at an aid station stop (as well as refilling bottles/bladder).

[@ivanmanzur1197]

I got same test last year here in Florida because I was suffering with cramps in my marathon races but from that test I never had more. I have same rate; 980 mg sodium by Lt. water lost

[@Vo2maxProductions]

great to hear. For the record I think a lot of cramps aren't usually linked to hydration (they can be of course) but I call it "sheer muscle fatigue" and it's usually when your leg muscles suddenly protest to a work load they are not prepared for. It seems like 800-900mg sodium per L is actually a pretty common concentration (i.e. not low salt, but not "super salty"). I always thought I was "super salty" and didn't sweat that much volume!

[@ivanmanzur1197]

In my case in Florida I sweat a lot but for example I ran NYC this year (remember me, I saw you with my wife near to Central Park when you was running that Saturday) with 500ml water with 400mg sodium by hour; and yes, a think that the first cramp cause is muscle fatigue too but in my case I lost 1.4 Lt. by hour hehehe. Glad to see you there and your pace strategy was perfect for your runner coaching to get his 2:50. Regards!!