The Relationship Between Performance Level and Training Stress


One graph, many principles

Eighty percent of what you need to know about endurance training can be illustrated by a simple graph. At the heart of the graph is a very simple idea that is often misunderstood. What many believe, is that there is a straight-line relationship between training and performance/fitness. In other words, the harder you train, the stronger you get.


That’s not the case.


The relationship is actually curvilinear (see Fig. 1). Initially, it takes very little training stress to see big gains in performance, such as at the start of the season or after returning from an injury. But, as your performance level improves, the line starts to level off and it takes increasingly more training stress to see even small gains:


Fig. 1: The relationship between training stress and performance level is curvilinear.


Put another way, if you increase your weekly training volume from 150 miles to 300 miles, your fitness is unfortunately not going to double. The improvements will be significantly less.


Eventually, any athlete will reach a plateau—no matter how hard they train, they won’t see any further improvements. But that’s not the only issue with training too much. There is another line—the likelihood of overtraining or injury. Initially, the likelihood is very low with low training stress. But as training stress increases, the likelihood increases (see Fig. 2).


Fig. 2: As training stress increases, so too does the likelihood of overtraining and/or injury.


Eventually, with too much training, your performance will not improve and your chance of overtraining gets high. This is not a place you want to be.


Charting your season on the graph

The graph gives a simple visual of why experienced endurance athletes train the way they do in the base season and in the race season (see Fig. 3).

Fig. 3: Building a base and building race fitness.


Building a base

If you take a proper rest between your race seasons, your l