If sustaining comfortable breathing through light exercise is the specific concern, worth understanding which mechanism actually addresses that.
Look specifically for an oxygen-utilisation mechanism, distinct from airway-clearing or antioxidant ingredients, since stamina during activity is tied to how efficiently the body uses oxygen, not just how open the airways feel.
This site names Cordyceps militaris specifically for this role — worth reading Michael T.'s featured account of better airflow during light activity as one relevant data point for this specific use case.
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