PS Smoking can also lead to this sensation....you can pick next time: Marlboro Light or Fran. Might be a close call....

You may have Exercise-Induced Eustachian Tube Dysfunction…

Exercise increases blood supply to all parts of the body. Along with this increased proliferation of blood, comes tissue engorgement...this is why your skin becomes red or flushed. When the tissue engorgement is around your eustachian tubes -- those tiny ventilation tubes that run from your middle ear space (the area on the other side of your eardrum) to the back of your throat -- it may cause the tubes to malfunction. Cigarette smoking can also cause eustachian tube dysfunction.

If the eustachian tubes clog, your ears may feel full / stuffy, and your hearing could be a bit muffled, like they need to "pop". If the e-tubes lock in the "open" position (they are normally closed and only open briefly when we swallow), you may hear your own voice or an echo.

As long as this exercise-induced eustachian tube dysfunction resolves after you cool down, there is no need to be concerned. Unfortunately, there may be little that you can do to prevent this from occurring, other than reducing the intensity of your exercise. Some ENTs will try nasal corticosteroid sprays or recommend ibuprofen, so these approaches may be worth a try.