To prescribe an optimal training programme we need to quantify the load it imposes accurately. However, the concept of Training Load is confusing, and most of its associated metrics have not been validated appropriately. Recent research has indicated that this lack of validity is critical and that many popular Training Load metrics do not reflect their related training dose. This talk will review some of the issues related to Training Load and its metrics, discuss recent research findings, and explore future directions for quantifying and optimising training.