Many people struggle to run a mile; others can knock out a 10K on a whim. A few brave souls take on "ultramarathons" — races longer than 26.2 miles (42.2 kilometers). But how far can a human run ...

To answer that question, first we have to define what it actually means to "stop." Dean Karnazes holds the unofficial record for the longest run without sleeping, at 350 miles (563 km), which he ...

Is it possible to be as fit in your forties and onwards as you were in your thirties? Perhaps even fitter? Yes it is, say fitness experts: there are plenty of people in their forties and even fifties ...