According to the National Wildlife Federation, the brown bear, also regarded as a grizzly bear, has the quickest forelegs, reaching speeds of up to 35 mph. The grizzly bear is just marginally faster than the American black bear- the nation's most prevalent bear species.
Of course, a bear could only accomplish such a feat when it's at the height of its athleticism. Not when it has just come from hibernation, having lost 15% to 30% of its body weight. Besides, it needs smooth, flat surfaces into which their long claws could sink.
In any case, despite their big muscular appearances, bears are surprisingly fast.
Check out this video!