A Wearable System for Real-Time Continuous Monitoring of Physical Activity

Figure 1

(a) Example of a PPG reflective probe. The couple emitter-detector is placed in direct contact with the tissue surface to reduce the optical noise. The amount of light absorbed by the tissue (red dots marked with a) depends on blood volume changes in the microvascular bed of the tissue; it is lower for small volumes (systolic phase) and higher for significant volumes (diastolic phase). (b) Typical PPG signal.

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