Training Load is a balance between a runner's recent training distance (captured in the last 7 days) and their typical training distance over the course of the last 28 days. Training Load can be used to keep the progression of running distance of an individual to a reasonable level, by guiding them to the correct balance between increasing fitness (without falling into over-training mode) and staying in the optimal training zone.
The graph below shows a period of sensible progression, followed by a period of under-training and then a 'spike' of over-training, where distance has increased too quickly. Prolonged weeks of intense training might soon lead to over-training, which will contribute to an increased risk of overuse injuries and fatigue. Under-training, on the other hand, will result in a loss of fitness and a significant decrease in athletic performance.
Training Load is also important because it has been found to have a strong relationship with running-related injury risk, where 'spikes' in the Training Load increase the likelihood of sustaining a soft tissue injury in the subsequent days/weeks.
Runners can optimize their Training Load through modifications to their future training routine and planned running exposure. This will ensure a safe increase in distance whilst staying in the safe Training Load zone. However, it's important to highlight the need for runners to listen to their own body and not run through pain/injury. The relationship between Training Load and injury risk is specific to each individual engaged in running activity. To find out more about the Training Load go to Optimising Training Load.