Yes, it's normal. You're seeing the effects of MPEG digital video compression, which is most noticeable during live sports broadcasts. That's because sports broadcasts have lots of fast motion and must be encoded in real time, unlike movies or TV shows that can be encoded more precisely. But note that your HDTV might have settings like "Motion Blur Reduction", or "Refresh Rate", or other settings that can help or hurt this sort of problem.
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