Concept
Single-session load
The stress created by one workout's duration, intensity, terrain, and unfamiliar demands.
Why one session matters
A sudden large increase inside one workout can expose tissues to far more repeated loading than they have practiced, even when weekly totals still look modest.
What creates a spike
Unexpected extra distance, hills, speed, or a much longer continuous running block can all create a large single-session jump.
How to manage it
Set the intended maximum before starting, keep easy days controlled, and change one major demand at a time.
How to use it
Finish the planned session even on a very good day, then use the recovery response to decide whether a later session should progress.
Common misconception
Feeling aerobically fresh does not prove that tendons, bones, and muscles are ready for a much larger session.