The difference between internal and external load
· Training Feel
It is the most useful distinction in athlete monitoring and also the most confused. They are not two ways of measuring the same thing at different precision: they are two different things, and you need both.
External load: what the athlete did
The work measurable from outside, regardless of who did it: distance covered, high-speed metres, accelerations, kilos lifted, minutes played. Measured with GPS, accelerometers or simply by counting.
It has a big advantage: it is objective and does not depend on anyone answering anything. And an equally big limitation: ten kilometres are ten kilometres for the player who slept well and for the one carrying three hard weeks.
Internal load: what it cost
The organism’s response to that work. It can be estimated from heart rate or, in the most widespread way, by asking: perceived exertion multiplied by duration.
It depends on the athlete and their state, which is exactly the point. The same session produces different internal loads in two players, and in the same player at two points of the season.
Why you need both
Together they answer a question neither answers alone: how much is it costing this athlete to do what they always do. If external load holds steady and internal load rises, something changed — and that does not show up on GPS.
In practice the external one is what you plan and the internal one is what you verify. A session is designed in metres and minutes; it is checked in how the twenty who did it experienced it.
If you have to pick one to start with, internal is cheaper: it needs no device. And it is usually the one missing, because external is already covered by the vests many clubs own.
Training Feel records each athlete’s internal load and lets you add GPS data where it exists, so both series can be read together.
See how it works