Poor training protocols will typically give an athlete durability through the volume they are doing but lack the improvement in speed potential that their efforts may suggest. This results in the ability to extend their speed potential curve to longer race distances but leaves them with the same speed potential curve from year to year. Durability (ability to meet speed potential curve at long distances) is developed simply by “getting the volume in” however, improvements in aerobic pace and pace at TH, take a more detailed approach to optimize. Obviously, if someone’s training protocol is poor, injury is more likely to occur which will derail the volume and dig into durability. However, for those who don’t get injured and put in huge volume under a poor training protocol, you typically see good race performances at the longer distances and sub par performances at the shorter distances relative to what their training volume may suggest. This concept can be see by older folks doing really well at the longer distances due to years of volume and resulting durability. So, even as their speed potential erodes as they age, they can still perform relatively well at the longer distances (because most folks at IM don’t meet critical volume and therefore lack durability). A solid training protocol results in improvements to speed potential curves in all three sports. Durability to extend those speed potentials to longer distances comes with volume over the long haul. If you find your shorter race distance performances staying stagnate, chances are that your training protocol can use some work.