dive profile more or less conservative. While not a direct integration, a diver can use the in- ▪ sights gained from their fitness monitoring – such as fatigue or poor recovery – to manually choose a more conservative setting for their dive. Integrating Physiological Metrics Could Be Risky: The algorithms are separate because integrating physiolog- ical metrics like heart rate directly into a decompression al- gorithm is not currently an accepted practice and would create significant safety risks. Decompression algorithms rely on established physical models of gas diffusion, not an in- dividual's real-time physical performance. Therefore, de- compression calculations remain a separate process from the dynamic biometric data collected by fitness trackers. Land-Based vs. Water-Based Activities: It’s important to remember that fitness algorithms are designed for land- based activities, which may not fully account for the unique physiological changes that occur during diving. For example, when underwater, breathing slows, heart rate drops, and blood flow is redirected to vital organs. Water pressure and temperature also impact how your body func- tions and exchanges gases. A 2018 study found that as divers go deeper, their heart rates consistently decrease and parasympathetic activity increases. Using underwater EKGs, researchers compared heart rates at the surface and at depths of 33 and 66 feet, confirming these physiological changes (Source: Front Physiol. 2018; 9: 110). Actual tracking underwater is limited, and understanding your device’s limitations is crucial. Fitness trackers use gyroscopes or accelerometers using ▪ vibrations of the body to estimate movement and cor- relate it to tracking steps and calculating calories. While there is some work being done in this area, particularly by Apple related to swimming, whether dry land move- ment is meaningful to fin-kicking underwater is still to be determined, especially considering that fins often RETAILING continued
compensate for around 40% of the effort. Bluetooth technol- ▪ ogy is only some- what reliable underwater for short distances. Many wearables esti- ▪ mate maximum heart rate using age
or resting heart rate, and some require a fitness test for more accurate results. Most of this baseline informa- tion, including body weight, is entered by the user. Devices may use electrical signals (ECG) or optical ▪ sensors (PPG) to measure heart rate or pulse, and some can estimate blood oxygen levels. The positioning of the sensors and the underwater environment, especially cold temperatures, might compromise accuracy of the information. Wearables that measure body temperature usually track ▪ skin temperature or estimate it based on heart rate, am- bient temperature, or both. For example, some devices monitor skin temperature at night to establish a base- line, then look for changes during the day. Recent Studies on Most Wearables and Apps: While manufacturers highlight differences between products, most wearables use similar exercise physiology algorithms. Apps help translate raw data into user-friendly feedback. However, studies show that only a small percentage of consumer wearables meet their marketing claims. For instance, research at Northwestern University found that fitness trackers often
miscalculate calorie burn for people with obesity due to differences in body shape and movement. Contact me with any questions about your fit- ness wearables or getting started with a dive fit- ness program at your store or resort!
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