Coach Dan John changed the way the world trained with kettlebells. He gives Harry Bullmore a rundown of everything you need to know to start using this training tool and revolutionise your fitness E xercise has become an expensive pursuit. I recently heard about a man who spent more than £1,000 while training for a marathon – a mountain of shoes, clothes, gels and physio funds responsible for clobbering his bank balance. The kettlebell is the antithesis to this . You pay a one-off fee for a