2d • General Discussion
Developing skills under fatigue, is it actually a thing?
One of the biggest discussions with coaches I have had during my coaching years had regularly been about how to maximise learning we can not have athletes who are fatigued.
The main conversation was always around work-to-rest periods when trying to teach drills or new movement patterns to athletes, or around the problem with always trying to do skill based sessions when athletes are fatigued.
For example, it used to be quite commonplace at GB Taekwondo that, following a morning session, athletes would do an individual with their coach to try and focus on their own individual development.
The challenge with this is that most coaches agree that fatigue makes performance worse in the moment, but does it actually affect learning?
Also, is there any argument to this idea of developing skills when fatigued?
Well I believe that a paper by Branscheidt et al. (2019) really sheds some light in this area.
The Study:
Branscheidt M, Kassavetis P, Anaya M, et al. (2019)
Title: Fatigue induces long-lasting detrimental changes in motor-skill learning
The Aim
The researchers wanted to answer one question:
Does fatigue simply reduce performance while you're tired, or does it actually reduce long-term motor learning?
These are two very different things.
In motor learning we distinguish between:
- Performance = How well you perform today.
- Learning = A relatively permanent improvement that remains after recovery.
Participants
The main experiment included:
- 38 healthy adults
- 20 participants in the fatigue group
- 18 participants in the control group
All participants learned the same novel motor skill.
The Task
Rather than using a sporting movement, participants completed a highly controlled laboratory task.
Using a force sensor held between the thumb and index finger, they had to:
- produce a precise amount of force,
- move a cursor through a sequence of targets,
- while being both fast and accurate.
The researchers combined speed and accuracy into a single skill score, allowing them to measure genuine improvements in motor skill rather than simply moving faster or making fewer errors.
How Was Fatigue Induced?
Before practising the skill, the fatigue group repeatedly performed maximal pinch contractions until their maximal force had fallen by approximately 60%.
Importantly, fatigue wasn't simply assumed.
The researchers confirmed it objectively using:
- maximal voluntary contraction (MVC),
- and surface EMG.
The control group performed the same movements at only ~5% MVC, so they completed the same protocol without becoming fatigued.
The Design
Both groups completed four practice blocks on Day 1.
They then returned on Day 2.
Here's the critical point:
Nobody was fatigued on Day 2.
If fatigue only affected performance then both groups should perform similarly once recovered.
If fatigue affected learning, the fatigue group should still perform worse.
The Results
Day 1
Exactly as expected.
The fatigued group performed worse.
No surprise there.
Fatigue reduced movement quality during practice.
Day 2
This is where things became interesting.
Even though everyone had fully recovered.
The fatigue group still demonstrated poorer skill acquisition.
Their learning rate remained lower than the control group despite no longer being fatigued.
The researchers concluded that fatigue had impaired motor learning, not simply temporary task performance.
Additional Experiments
The authors didn't stop there though.
They performed three additional experiments to understand why this happened.
Experiment 2
Participants learnt the task with one fatigued hand, but learning was assessed in the opposite, unfatigued hand.
Learning was still impaired.
This suggested the problem wasn't simply within the fatigued muscles it was occurring within the central nervous system.
Practical takeaways for us as coaches:
This study does not suggest that athletes should never perform technical work while fatigued.
Instead, it encourages us to separate two different coaching objectives.
Skill Acquisition
If you're introducing:
- a new exercise to develop strength,
- working with a coach to try and make an athlete better at a sport specific skill,
- a new footwork pattern,
- or refining movement quality,
the evidence suggests these sessions are likely best performed when athletes are relatively fresh, allowing higher-quality repetitions and better long-term learning.
Skill Robustness
Once a movement has become well established, fatigue becomes an important constraint.
Competition doesn't occur in a rested state.
Athletes still need to:
- maintain technique in later rounds,
- make decisions under fatigue,
- execute skills while physiologically stressed,
- and remain tactically effective when exhausted.
These sessions are about expressing an already learned skill under realistic conditions not acquiring it for the first time.
My Coaching Takeaway
One of the biggest mistakes we can make is treating skill acquisition and skill expression as the same thing.
This paper suggests they're not.
For me, the practical message is simple:
Teach new skills when athletes are fresh.
Challenge established skills when athletes are fatigued.
That distinction allows us to develop both better movement quality and better competition robustness, rather than sacrificing one for the other.
But we really start to begin challenging this concept of learning new skills when fatigued. It's only when an athlete has really established truly high levels of skill competency, or the ability to perform a task at a very, very high level with minimal input from a coach, that it could then begin to be developed under fatigue. They can learn to express that skill when tired. Trying to do so beforehand is going to lead to a detrimental learning effect of that skill.
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Developing skills under fatigue, is it actually a thing?
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