Is exercising at 200 heart rate for 25 minutes dangerous for the heart?

I've been exercising for a few months and my exercise heart rate still hasn't gone down. Whenever I do moderate exercise my heart goes up to 200 bpm and I donr really feel tired at all. I'm not lightheaded or even short of breath but my heart rate is 200. Can I exercise at 200 bpm for 25 minutes or will... show more I've been exercising for a few months and my exercise heart rate still hasn't gone down. Whenever I do moderate exercise my heart goes up to 200 bpm and I donr really feel tired at all. I'm not lightheaded or even short of breath but my heart rate is 200. Can I exercise at 200 bpm for 25 minutes or will this burn heart muscle and stress my heart?
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