Rhodri S. Lloyd is a Reader in Paediatric Strength and Conditioning and Chair of the Youth Physical Development Centre at Cardiff Metropolitan University, UK. His research interests surround the impact of growth and maturation on long-term athletic development and the neuromuscular mechanisms underpinning training adaptations in youth. He is a senior associate editor for the Journal of Strength and Conditioning Research and an associate editor for the Strength and Conditioning Journal. In 2016, he received the Strength and Conditioning Coach of the Year award for Research and Education from the UK Strength and Conditioning Association and in 2017 was awarded the Terry J. Housh Outstanding Young Investigator of the Year award from the National Strength and Conditioning Association. Jon L. Oliver is a Professor of Applied Paediatric Exercise Science at Cardiff Metropolitan University, UK, and co-founder of the Youth Physical Development Centre. He is also an Adjunct Professor at the Sports Performance Research Institute New Zealand, and Strength and Conditioning Research Lead for the Welsh Institute of Performance Science. He has been at the forefront of challenging old and developing new models of youth athlete development, as well as contributing to contemporary national and international position and expert statements on training youth. This has been supported by experimental research examining how growth and maturation interact with the development of physical fitness, responsiveness to training, injury risk, overtraining, and the health and wellbeing of young athletes.