"How fast can a human run and would we be faster as quadrapeds?" This question flew in via Twitter from historian Greg Jenner.

Is there a limit to human sprinting performance? In this episode we investigate the biomechanics of running, statistical trends in human performance and which kind of monkey runs the fastest.

But first, an experiment. Due to some spurious and possibly fictional injuries, neither Hannah nor Adam are fit enough to take part in a sprint trial at the University of Bath. So long-suffering Producer Michelle steps up to the challenge and into the starting blocks. Not known for her love of athletics, or exercise of any sort, how will she fair in the ultimate speed test?

Biomechanist Peter Weyand from Texas discusses the role of different muscle types in speed versus endurance. Sports scientist Polly McGuigan reveals why Usain Lightning Bolt is still the fastest man in the world. And Prof of Sports Engineering Steve Haake reveals how fast a man can run like a monkey.

Presenters: Hannah Fry, Adam Rutherford