[ SWEAT ]■
Know what you lose.
How much you sweat and how much sodium you lose doing it. We weigh you, patch you, and send you out onto the LA River trail for a real run in real conditions. Then we build your hydration plan from what came out. Treadmill or bike are also options. $199, or part of the Baseline for $349.
What you get
Your sweat rate in liters per hour.
Your sweat sodium concentration and total sodium lost per hour.
Where you fall: low, moderate or high sweater, and salty or not.
A hydration plan: how much to drink and how much sodium to take per hour, for training and race day.
Product picks that match your numbers, so you’re not guessing at the aid station.
Why it matters
Sweat is personal. Athletes sweat anywhere from about 0.5 to 2 liters an hour, sometimes over 3, and sweat sodium ranges from about 10 to 90 mmol/L between people (Baker, 2017). One generic plan can’t cover that range.
Too little fluid costs you. The ACSM recommends drinking enough to avoid losing more than 2% of your body weight, with plans built for the individual (Sawka et al., 2007).
Too much is dangerous. At the 2002 Boston Marathon, 13% of finishers tested had low blood sodium, some critically. The biggest risk factors were gaining weight during the race and finishing over 4 hours (Almond et al., 2005). The fix is knowing your numbers, not drinking at every mile.
Who it’s for
Marathoners, ultrarunners, triathletes and cyclists. Anyone who cramps, fades late, finishes caked in salt, or feels sloshy on long efforts. Anyone racing in heat.
How to prep
Eat and drink like a normal training day. Wear what you race in. Plan for a steady 45 to 60 minute run.
FAQ
Does it change over time? Yes. Heat, fitness and acclimation all shift it. Recheck before a big race with the Race Week Dial-In ($79).
Can I do it with the Active Metabolic Test? Yes. That’s the Baseline: both in one visit for $349.
The research
Almond CSD, et al. Hyponatremia among Runners in the Boston Marathon. NEJM, 2005.