John Hellemans’ interest in altitude training began with an unexpected boost in his performance after skiing in the Austrian mountains. This curiosity grew during his time coaching triathlete Erin Baker, who saw exceptional results after training at altitude in Boulder, Colorado. John’s subsequent positive personal experience led to a lifelong exploration of the topic as he endeavored to prepare himself and his athletes for elite competition. Mike Hamlin, a sport and exercise scientist, met John Hellemans shortly after moving to Christchurch, New Zealand, in 1999 and the pair started working together to unravel the intricacies of altitude and hypoxic training. Mike’s role in the book is to bring a scientific perspective that complements John’s practical, coaching-based knowledge.