The Bühlmann ZHL-16C is a standalone decompression algorithm utilized in dive computers for calculating inert gas loading during and after dives and does not directly integrate with fitness monitoring algorithms. It divides the body into 16 theoretical "tissue" compartments, each with a different gas absorption rate. Specifically, the algorithm uses variables like current depth, dive time, and breathing gas to calculate tissue loading and makes recommendations for safe ascent and decompression. However, modern "smart" dive computers use data from the dive algorithm alongside fitness data from biometric sen- sors to provide more personal performance information for divers. Smart Dive Computers Use Both Data Sets: Fitness data is not used to alter the core ZHL-16C dive calculations, but it can be used to provide the diver with additional in- sights and to allow for more personalized conservatism set- tings. High-end dive computers from manufacturers like Garmin and Suunto collect both types of data and display both. RETAILING continued
Wear Diving Fitness Monitors Under Your Wetsuits: Both optical heart rate dive computers (wristwatches) and electromagnetic heart rate dive computers (chest straps) need to be worn against the skin, not over a wetsuit. A few things to note about these devices: Key parameters, such as age and weight, which are used ▪ for body fat percentage estimates, are set by the user.
Some dive com- puters allow divers to set heart rate ranges and fitness levels themselves. These computers adjust the decom- pression algorithm to account for workload on the surface before or after the dive.
They can record a diver's heart rate while underwater ▪ to help them stay within safe exertion levels. Most have an optional warning to help detect early signs of stress. They track this information by the fitness monitor, and ▪ it can be viewed alongside dive logs after the activity. The heart rate is displayed on the screen for most mod- ▪ els. Garmin and SCUBAPRO have an optional heart rate display. The Apple Watch may turn off the heart rate in depth ▪ mode. Of note is that with the Apple Watch, the dive is complete 10 minutes after getting out of the water and staying out. While not directly tied to decompression, a device can ▪ measure overall body stress and recovery levels before and after a dive using metrics like heart rate variability (HRV). Oceanic emphasizes tracking recovery time. Though the device will not change the ZHL-16C pro- ▪ file, it can help a diver decide whether their body is suf- ficiently rested for the next dive. A smartwatch that functions as a dive computer, such ▪ as the Suunto Ocean or Garmin Descent series, stores both dive-specific data from the ZHL-16C algorithm and fitness data in the same logbook, enabling divers to see their underwater path, tank pressure, heart rate, and training load in one place. Many implementations of the ZHL-16C algorithm ▪ allow the diver to adjust "gradient factors" to make the
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