Popular wearable maker WHOOP has patented a new pressure-sensitive strap for its wearable device that can help optically detect oxygenation level and hemoglobin concentration within muscle and tissue.
This will make it possible for the wearable to detect if a muscle is utilizing aerobic or aerobic processes.
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Pressure sensors may be included in the strap and may be used, for example, to: examine the heterogeneity of a pressure distribution of the strap, allowing a user to manage pressure consistency throughout measurements using the optical device; determine if pressure affects measurements taken by the optical device; and/or manage levels of blood flow restriction, allowing a user to perform exercises with lower levels of oxygen delivery, such as hypoxic training.
Oxygen is required for cells to produce energy in a process called oxidative phosphorylation. Hemoglobin is the protein in red blood cells that binds oxygen molecules for transport from the lungs to all tissues and exists in two states, oxygenated and deoxygenated.
Oxygen saturation (SO.sub.2) denotes the percentage of oxygenated hemoglobin out of the total present hemoglobin. Muscle oxygenation (SmO.sub.2) is used here to indicate the oxygen saturation in the muscle.
Muscles at any time, and especially when exercised, require oxygen for energy production, and therefore muscle oxygenation is a parameter that encapsulates the metabolic state of the muscle.
Specifically, it describes how much oxygen is present in the muscle and when oxygen consumption exceeds the supply.
The lactic acid build-up in the blood is an indirect measurement of oxygen deficits after a muscle was in an anaerobic state, as anaerobic glycolysis results in the excretion of lactate into the bloodstream.
Monitoring muscle oxygenation during physical activity may provide valuable insight into physical performance, particularly for those engaged in high endurance activities such as long-distance running, biking, and swimming.
Muscle oxygenation may indicate whether the muscle is aerobic, close to an anaerobic threshold, or anaerobic, and thus may be relevant to whether an athlete is performing optimally.
By contrast, conventional techniques for assessing physical performance, including heart rate monitoring, provide different information and are inadequate to assess muscle performance.
The pressure-sensitive band can be positioned on a user’s leg or arm. This will allow for a wearable fitness sensor that can assess the user’s muscle oxygenation and/or hemoglobin concentrations and, therefore, indicate the user’s physical state and performance. 
The optical sensor on the band will be able to collect signals for oxygenated hemoglobin concentration (HbO.sub.2), deoxygenated hemoglobin concentration (Hb), or total hemoglobin concentration (HbT).
WHOOP will not only be able to incorporate these signals into additional refinements for its “Strain” and “Recovery” scores but use the new signals for providing appropriate guidance during workouts.
