Replying to this thread, about pulse-ox oxygen saturation measurement during an activity, which was closed
Oxygen (O2) saturation is not supposed to drop much when working out. Before O2 drops, your carbon dioxide (CO2) levels rise and your body normally responds by increasing your breathing well before any major changes in your O2. So, when all goes well, your body steers on CO2 concentrations.
But... All is not always well. For example for people with post-covid. I myself had this. I saw oxygen levels drop below 90% when i started physiotherapy. Fortunately, this recovered, bit it still makes me want to track my oxygen saturation every now and then, now that I'm training for a quarter marathon.