Some runners assume they're getting a great workout if they challenge themselves by running their entire run on a steep incline. But that much straight hill running is never a good idea and could lead to injuries. Think about it: Would you ever find a 3-mile hill at a 5 or 6% incline?
You should avoid running at a steep incline for more than 5 or so minutes. You'll get a much better, safer workout if you alternate between running a few minutes with an incline and running a few minutes without an incline.
Also, you should also avoid going above a 7% incline because it places too much strain on your back, hips and ankles.
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