How to Monitor Mental Fatigue
Mental fatigue quietly chips away at performance.
It slows reaction time, clouds decision-making, and affects coordination and endurance, even when physical performance still looks solid. Athletes might appear focused, but mentally, they could already be running on empty.
That’s why you can’t just rely on what you see or how someone says they feel. You need objective tools that show what’s really going on.
Soma helps you do exactly that with three core tools:
PVT / PVT-B: Measures attention, reaction time, and lapses
PFTT: Detects the point where cognitive performance starts to drop during physical effort
RMF Scale: Captures how mentally fatigued the athlete feels after a task
Start Simple: Focus on Lapses
If you only track one thing, track lapse count.
Lapses are delayed reactions caused by mental fatigue. They increase with mental fatigue, even when reaction time or accuracy still looks fine.
In PVT: a lapse = response slower than 500ms
In PVT-B: a lapse = response slower than 355ms
Lapse count rises before performance fully drops. That makes it the clearest early sign of cognitive fatigue.
PVT vs PVT-B: What’s the Difference?
Both tests measure sustained attention and response speed, but they’re structured differently.
Feature | PVT | PVT-B |
Duration | 5 to 10 minutes | 3 minutes |
Lapse Threshold | Slower than 500ms | Slower than 355ms |
What Is Cognitive Load?
Cognitive load is the mental effort needed to complete a task. Just like physical load, it needs to be managed.
Too little = no challenge, no growth
Too much = performance drops, fatigue builds
The goal is not to avoid mental fatigue. The goal is to track it so you know when to push and when to recover.
Why Tracking Matters
If you’re not tracking mental fatigue, you’re flying blind.
You might be:
Underloading athletes and missing opportunities for adaptation
Overloading them without realizing it until performance suffers
The sooner you see the data, the sooner you can make smarter decisions.
How to Adjust by Season
Mental fatigue load should match the phase of training.
In-season: Keep it lighter to avoid overload
Off-season and pre-season: Push harder, but track recovery closely
How to Use PVT-B
Run a PVT-B test:
Before a session to check cognitive readiness
After a session to see how the brain responded
What to watch:
Lapses: The easiest and most reliable signal. If they go up, the athlete is fatigued.
Reaction Time: Slower responses mean reduced alertness.
Accuracy: If it drops, mental control is slipping.
Variation: More fluctuation = more cognitive strain.
Example:
| Start of Session | End of Session |
RT | 356ms | 372ms |
Accuracy | 100% | 100% |
Variation | 13% | 20% |
Lapses | 1 | 4 |
Even though accuracy stayed perfect, the higher lapse count and variation show the session pushed cognitive capacity.
Track PVT-B results over 3 to 4 weeks to establish an athlete’s personal baseline.
How to Use the PFTT
The PFTT (Psychomotor Fatigue Threshold Test) shows when cognitive performance starts to decline during physical exercise.
What you’ll see:
Initial phase: Cognitive performance improves with physical intensity
Peak zone: Fastest, sharpest decision-making
Threshold point: Reaction time starts to slow, accuracy begins to drop
Post-threshold: The brain is overloaded even though the body might still perform
Example:
| Start | Peak | Threshold Crossed |
RT | 331ms | 310ms | 348ms |
Accuracy | 96% | 96% | 84% |
HRV | 100.7 | 104.6 | 67.7 |
This helps you design training that either holds athletes in their sweet spot or intentionally pushes them past it to build resilience.
How to Use the RMF Scale
The RMF (Rating of Mental Fatigue) is a quick post-task check-in.
After a cognitive task, the athlete rates how mentally fatigued they feel. It’s useful for:
Comparing subjective experience with objective performance
Spotting when perception and data don’t match
Adding another layer of insight when making training decisions
It’s built into Soma and automatically links to the training data.
Bringing It All Together: Start Simple, Track What Matters
Mental fatigue often hides in plain sight, but tracking it doesn’t have to be complicated. The best place to start is with lapse count on the PVT-B. It’s fast to collect, easy to interpret, and gives you the clearest signal that the brain is starting to slow down.
From there, you can build a fuller picture. Use the PFTT to identify when cognitive performance begins to decline during physical training. Add the RMF scale to capture how the athlete feels after each task. Together, these tools help you track mental fatigue with precision.
When you monitor cognitive fatigue the same way you track physical output, you stop guessing. You start making better training decisions based on the whole athlete.
FAQs
Can I Use PFTT to Monitor Mental Fatigue?
Yes, absolutely. While the PFTT was originally developed to detect the point where an athlete crosses the psychomotor fatigue threshold, it is also sensitive enough to track general mental fatigue.
This makes it a great option when:
Athletes are disengaged or bored with PVT-B
Lapse counts are too high (over 10 lapses)
You need a shorter, more engaging task
The PFTT only takes 90 seconds and can be used both before and after a training session. It gives you fast, objective insight into how the brain is responding, especially when longer tasks like the PVT-B aren’t ideal.
If compliance is low or the data from PVT-B isn’t usable, the PFTT gives you a practical and effective alternative. The goal is not to force one tool, but to get the clearest picture of mental fatigue so you can adjust training in real time.
How many lapses are too many?
It depends on the athlete’s baseline, but generally:
PVT-B: More than 5 lapses = start watching closely
Over 10 lapses = clear sign of mental fatigue
Compare to previous sessions to track change. A sudden spike often means recovery wasn’t complete.
Can I use these tests with youth athletes?
Yes, but keep it short and engaging. PVT-B and PFTT are safe, scalable, and non-invasive. Use variation and lapse count as your key metrics. The younger the athlete, the more mental fatigue tends to affect attention and consistency rather than raw speed.