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Acumen Hydra-Alert Sports Watch with Fluid Check (Outdoor Retailer Summer Market 2005)

A watch that reminds you when and how much to drink


by Alan Dixon | 2005-08-12 03:00:00-06

Acumen Hydra-Alert Sports Watch with Fluid Check (Outdoor Retailer Summer Market 2005)

Note: while this article discusses water loss calculations, Hydra-Alert is considering adding calorie loss calculations to the watch in the future. More about this possible feature at the very end of this article.

The Hydra-Alert™ (HA) is a sport watch that adds a new feature to training aids, it estimates your fluid loss and tells you when and how much to drink. The Hydra-Alert™ sports watch monitors air temperature, ambient humidity, and your heart rate to estimate fluid loss during physical activity. No, it doesn’t directly monitor water loss, it estimates it. The HA does this by plugging monitored values (air temp and humidity) and exertion level (heart rate vs. resting heart rate) into internal formulas for fluid loss. There is a one-time programming of the unit for the user’s weight, sex, age, resting heart rate and maximum MET (VO2 MAX) The unit will run a simple self administered test to calculate resting heart rate and maximum MET if you don’t know them.

The HA has been in development with the Military to keep soldiers hydrated in difficult environmental conditions, like the Iraq war. For instance it helps soldiers on guard duty (they wear hydration bladders) to hydrate at proper levels.

One big advantage I can see to the HA is to conserve water. With an accurate estimation of you water loss, you drink only what you need. This allows you to carry only the water you need and minimizes drinking stops to those that are needed. No more conservatively guessing at water you need, carrying and drinking large amounts, and peeing it out in short order. I can also see applications for the HA in ultra-endeavors. I wished I had the HA for long hot dry days canyoneering in Southern Utah.

The Hydra-Alert™ can tell you, at user determined intervals, how much water you need to drink (fluid lost during the interval). For example, you could set the unit to beep every 20 minutes with the amount of water you need to drink. If you can’t drink then (like you’re in the middle of a climbing pitch) the unit will keep track of you water loss and give you an updated amount 20 minutes later that includes the water you didn’t drink. The HA keeps track of the total amount of water lost during the entire exercise period. This is very useful information for predicting water consumption for future trips or training sessions.

Obviously the HA designers had the medial risks from dehydration in mind, not conserving water! Maintaining proper hydration is essential for healthy cardiovascular and metabolic function. Possible consequences from dehydration include:

  • Reduced endurance
  • Diminished physical performance
  • Diminished cardiac output
  • Increased body temperature
  • Elevated heart rate
  • Inaccurate perceived exertion
  • Loss of muscle strength
  • Inefficient oxygen consumption
  • Eventual Heatstroke and Heat Exhaustion

The Hydra-Alert™ also calculates a four zone Heat Index based on temperature and humidity: Caution, Extreme Caution, Danger, and Extreme Danger. These give the user an indication of risk of dehydration before they start to exercise. Oh, and the Hydra-Alert is accurate even when you’re not exercising.

Features Included in Hydra-Alert watches:

  • Fluid Check™ for Safeguarding Against Dehydration.
  • Build-in sensor for detecting Temperature and Humidity
  • Display Heat Index
  • MAX MET (VO2 MAX) Calibration
  • Fitness Index
  • Heart Rate Monitoring
  • Three separate EZ-Set Target Zone with Visual and Audible alarms
  • Records and Displays Time Below/Above/Within TZ
  • In-Zone-Goal Count Down Timer (0-60 min)
  • Heart Rate Sampling: 5, 15, 30, 60 sec or 5 min
  • 50 Lap Memory over 1 Exercise Session
  • Interval Timer
  • Easy to Read Stopwatch
  • Dual Display for Analog and Digital Time
  • Weekly and Annual Event Reminder
  • Date and Day Display
  • Daily Alarm
  • Nite Lite with Smart Lite Function
  • Scratch Resistant Crystal Lens
  • Water Resistant to 30 Meters
  • Rechargeable Battery
  • MSRP: $150 to $350 depending features (four models)
  • Weight unavailable

Now about calorie loss: How cool would it be if you not only knew water loss but also how many calories you were burning? Using the same information of monitored heart rate the HA could (in a future version) figure out how many calories you burn. So at the reminder intervals it would not only tell you how much water to drink but also how many calories to eat. Not only that, the unit, knowing your exertion level, would figure out the amount of fat and carbohydrate your body burns. It could even tell you when you start to enter critical glycogen depletion and start metabolizing body muscle into energy (not good).

If you took some good training hikes with the HA monitoring calorie consumption you’d get a good idea of how much energy you expend hiking or running. With this information you could better calculate the food you need on a trip – that is, you could figure out the minimum amount of food for a trip saving a lot of weight. Also, with the HA you could hike in your most efficient “fat burning” zone.

Again, I stress that the calorie monitoring function is not in any current Hydra-Alert units and not even announced for future units. It is simply based on discussions with HA’s physiologist about possible future enhancements using their technology.


"Acumen Hydra-Alert Sports Watch with Fluid Check (Outdoor Retailer Summer Market 2005)," by Alan Dixon. (ISSN 1537-0364)., 2005-08-12 03:00:00-06.