Jacob Puzey cringes when he hears references to the ‘dreadmill’ or talk about boredom. The US ultrarunner and coach doesn’t understand the hate for the mechanical marvel that is the modern treadmill.

Claire asks: Currently, I am using a treadmill for all of my running. I am thinking of signing up for my first half marathon in the fall, so can I continue to train using only the treadmill? It is ...