How to Monitor Mental Fatigue in Soma Analytics

Mental fatigue does not show up like sore muscles or a slow sprint.
It creeps in quietly, slowing reaction time, clouding decisions, and breaking coordination long before physical performance drops. You cannot rely on what you see or what an athlete says they feel. You need objective data that shows when the brain is starting to fade.

Soma gives you three core tools to measure mental fatigue with precision.

Cognitive load is the mental effort required to complete a task. It behaves like physical load.

The goal is not to avoid fatigue, but to track it, manage it, and use it to guide recovery and adaptation. Without tracking, you are guessing. You might underload athletes and miss adaptation, or overload them until performance drops. Objective data gives you clarity on when to push, when to pull back, and when to recover.

The PVT-B (Psychomotor Vigilance Test – Brief) measures sustained attention, reaction time, and lapses. It is the simplest way to monitor whether your training load is high enough to drive adaptation. Running a PVT-B test before and after a session gives you a clear picture of load and recovery.

When analyzing PVT-B data, don’t focus only on reaction time. Reaction time may slow slightly, but it often changes very little when fatigue appears. The real indicators are variation and lapse count, where you’ll see the most noticeable shifts.

A lapse is any response slower than 355 milliseconds in the PVT-B.
​Even small increases in lapses or variation show that the brain is tiring.

Even with perfect accuracy, the higher variation and lapse count show clear cognitive fatigue.

​This confirms that the session created the right amount of challenge.

If you applied the right cognitive load, you will see it in the post-session data.

Healthy post-session indicators:

This shows the brain was challenged enough to trigger adaptation.

As long as pre-session lapses return to between 0 and 3 before the next session, recovery is on track.

If lapse count exceeds 5 before or after a session, the load was too heavy.
If pre-session lapses stay above 3, recovery has not fully occurred. Reduce task duration, intensity, or session frequency before continuing to progress.

When reaction time, variation, and lapses all stabilize for several sessions, the athlete has adapted to the current cognitive load. At that point, the session is no longer stressful enough to create change. Increase the challenge by extending duration, raising task intensity, or applying a mode such as time pressure, dual task, or distraction.

After four weeks of testing, you will have a baseline for each athlete.
Once you know their normal range, it becomes easy to spot when they are under- or over-loaded.

If lapses stay at zero, the athlete is not mentally fatigued. That is fine during in-season periods when the goal is freshness. But if you are trying to push limits, you should see mild fatigue with small rises in reaction time, variation, or lapses.

The Psychomotor Fatigue Threshold Test (PFTT) identifies the point where cognitive performance begins to decline during exercise. It is the most effective tool for measuring cognitive endurance and detecting when the brain starts to break down under physical stress.

When reaction time starts to slow, the threshold has been crossed. Over time, the goal is to push that point further out. If the threshold appears later in the session, it means the athlete’s mental endurance has improved.

You can use the PFTT in several ways depending on your training setup:

Option 1 : Track breaking points:

Option 2 : Between exercise sets:

Perform a PFTT after each physical block to monitor cognitive decline as fatigue builds.

Option 3: Intermixed cognitive load:

Combine PFTT with cognitive tasks during training.

Example: Physical training → Cognitive task → PFTT → Repeat until the end of the session.

Monitor PFTT reaction time, accuracy, and variation over time. The goal is to see the athlete maintain sharp reaction times, stable accuracy, and low variation for longer durations before the decline begins. This indicates improving cognitive endurance and fatigue resistance.

The graph below shows an example of a PFTT performed pre-session, mid-session, and post-session to visualize how performance trends change with fatigue.

The Rating of Mental Fatigue (RMF) scale captures how mentally tired the athlete feels after each task. It connects subjective feedback with objective data, showing whether perception and actual performance match. The RMF scale is built into Soma and links automatically to each task. It is best used to confirm how mental fatigue feels compared to what the data shows.

Start simple by tracking lapse count first.
Then add PFTT to identify the fatigue threshold and RMF to capture perceived tiredness. When cognitive data sits alongside physical data, you can see the full picture. You can tell whether the athlete is adapting, fatigued, or ready for more load. Mental fatigue is not a problem. It is feedback. Measure it, understand it, and use it to guide progression.

With Soma, you can see exactly when to push harder, when to recover, and when the brain is ready to adapt.

A simple step-by-step guide to interpret cognitive fatigue and adjust training load in Soma Analytics.

1. Run a Pre-Session PVT-B
→ Check readiness and baseline state.
​If lapses = 0–3 → athlete is ready.
​If lapses >3 → recovery incomplete, consider lowering load.

↓

2. Run the Training Session
→ Apply normal cognitive and physical load.
→ Optionally pair with heart rate tracking or PFTT to measure fatigue during exercise.

↓

3. Run a Post-Session PVT-B
→ Check immediate cognitive response.
​If RT slightly slower, variation up, 1–5 lapses → healthy strain.
​If >5 lapses or large RT spike → load too high.

↓

4. Add RMF Scale Feedback
→ Compare how fatigued the athlete feels with the actual data.
If perceived fatigue matches data → recovery is on track.
If perceived fatigue is low but lapses are high → hidden fatigue, adjust plan.

↓

5. Adjust the Plan
→ If underloaded: increase duration, intensity, or add a mode (time pressure, dual task, distraction).
→ If overloaded: reduce task time or skip a day to recover.
→ If adapted: progress load after 3–4 weeks.

↓

6. Track Long-Term Trends
→ Over several weeks, use PVT-B, PFTT, and RMF to build a cognitive load profile.
→ Look for patterns: rising variation, stable recovery, and expanding threshold times all confirm adaptation.

Mental fatigue is not failure. It is a signal that the brain is adapting to training load.
Measure it, monitor it, and use it to drive smarter performance programming.

A simple step-by-step guide to measure the Psychomotor Fatigue Threshold (PFTT) and adjust training load in Soma Analytics.

1. Run a Pre-Session PFTT

→ Measure baseline cognitive readiness before physical or combined training.

↓

2. Run a Mid-Session PFTT (Optional)

→ Perform during training or between exercise sets to identify the breaking point.

If reaction time (RT) and variation remain stable → the athlete’s capacity is holding strong.

If RT slows and variation increases → the athlete has reached their fatigue threshold.

↓

3. Run a Post-Session PFTT

→ Measure the athlete’s immediate cognitive response after training.

If RT is slightly slower, accuracy remains stable, and variation rises slightly → this indicates a healthy level of strain.

If RT slows significantly, accuracy drops, or variation spikes → the training load was too high.

↓

4. Adjust the Plan

→ If underloaded: increase duration, intensity, or add a training mode.

→ If overloaded: reduce task time, allow extra recovery, or continue observing to see if adaptation occurs the following week.

→ If no change in PFTT data: increase both physical and cognitive load.

↓

5. Track Long-Term Trends

→ Compare pre-, mid-, and post-session PFTT results over time.

→ Look for patterns:

When reaction time is fastest, the athlete is in their optimal performance zone, showing peak focus and efficiency. Once reaction time begins to slow, the athlete has crossed the threshold, meaning cognitive fatigue has set in. The goal is to extend how long the athlete can maintain sharp reaction times, stable accuracy, and low variationbefore the decline begins. This confirms improved cognitive endurance and greater resistance to fatigue over time.