As a coach who has kept one foot in the world of sports science research and the other in hands on training, I understand the importance of textbook quantifiable means and methods for creating an overload to spur continued adaptation. That said, I also recognize the benefits of having flexibility to manipulate training variables and having alternative methods of applying and monitoring overload. This helps with adjusting to varying real-world issues and logistical concerns.
It isn’t always a question of “what’s next?” but often a question of “what is happening right now?” Strength and conditioning coaches and athletes monitor training loads and intensity to show what training has been completed, and how subsequent training can be changed to affect performance. Similarly, some coaches use products like Heart Rate Variability to measure training ‘readiness’ and fatigue. Although these methods provide information an athlete can use between sessions, they do nothing in terms of providing feedback during training.