system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: How come making your heart work extra hard during cardio exercise is considered healthy, but making your heart work extra hard by consuming large amounts of caffeine is considered dangerous and bad for you?

I'll preface this by saying I don't *actually* think this would be a good idea, and exercise obviously has other benefits besides keeping just got heart healthy, but let's ignore those other benefits for a moment.

Aerobic exercise like running, swimming, cycling, etc is considered good for your cardiovascular health because it "works out" your heart, increasing both heart rate and blood pressure.

However, if I increase my blood pressure and heart rate by chugging down a pack of Red Bull, I'm no longer "working out" my heart, I'm "excessively straining" my heart and its considered both dangerous and unhealthy.

So what gives? How come I cant decrease my risk of heart disease by drinking a pot or two of black coffee every morning instead of running on the treadmill for an hour every day?
gpt
During normal exercise the heart beats faster and builds it's vascular infrastructure to deal with the increased metabolic demand of exercise induced hypoxia. The more you exercise over time the more the heart develops its infrastructure to adapt to the demand.

Coffee causes the heart to beat faster due to caffeine's effect as a neurological stimulant. It doesn't receive the normal stimuli to adapt a more robust atheletic vascular infrastructure and cardiac cells are put under abnormal stress because of the lack of said adaptations.