Feeling unusually energized or mentally sharp may seem like a sign that you can keep going. New research suggests your brain may have a different message.
A productive afternoon may not tell the whole story
Picture this: It is midafternoon, but instead of feeling sluggish, you are unusually focused. Your work is moving quickly, your concentration feels strong and the tasks you have been putting off suddenly seem easy.
It can be tempting to take that burst of energy as permission to keep working.
But a new study suggests that unusually strong mental performance may not always mean you have an unlimited supply of energy left.
Researchers examined how changes in fatigue and mental performance throughout the day were connected with a person’s ability to continue performing when tired. Their findings suggest that both feeling more fatigued than usual and performing better than usual could be followed by a reduced ability to push through fatigue later.
In other words, your best-feeling moments may not always be the best indication of how much energy remains in reserve.
What researchers found
The study, published in Communications Psychology, combined information from six separate studies involving 1,088 people.
The participants included both healthy individuals and people living with ongoing health conditions. Rather than relying exclusively on controlled laboratory sessions, researchers collected information from participants repeatedly during their normal daily routines.
At different points, participants reported how tired they felt. They also completed brief tests designed to measure processing speed, or how quickly they could respond to a simple mental task.
Because the researchers had multiple measurements from the same individuals, they could compare each person’s results with their typical pattern.
That distinction was important. Instead of simply asking whether people who were generally more tired performed differently from people who were generally more energetic, researchers looked at what happened when an individual was having an unusually tired or unusually sharp moment.
Fatigue was only part of the picture
The results showed that people who felt more tired than their usual level had a harder time maintaining performance despite fatigue in the hours that followed.
But the researchers also found a similar pattern after periods of unusually fast processing speed.
That means the signal was not simply, “I feel tired, so I should stop.”
Someone could feel unusually alert, focused and productive and still have less capacity to maintain that level of effort later.
The researchers described this ability to continue functioning despite fatigue as fatigue override. It is something people rely on regularly, whether they are finishing an important project, concentrating through a long meeting or completing a demanding task when their energy is running low.
The study also found that participants with ongoing health conditions had a lower overall ability to continue performing despite fatigue compared with healthy participants.
Why your energy can be difficult to judge
It is natural to use productivity as a quick measure of how much energy you have available.
If you are accomplishing more than usual, you may assume your body and brain are operating at full capacity. If you are struggling to concentrate, you may interpret that as an obvious signal to slow down.
The research suggests the picture can be more complicated.
A temporary boost in mental performance does not necessarily mean your capacity will remain high for the rest of the day. Likewise, an unusually difficult period may be useful information about how your energy is changing.
The key may be paying attention to changes from your normal pattern rather than judging your energy solely by how productive you feel at a particular moment.
How to pace yourself during demanding days
The findings do not mean you should stop working whenever you experience a productive streak. Instead, they offer another reason to be thoughtful about how you use periods of high focus.
If you feel more tired than usual, consider taking a short break rather than automatically trying to power through. Walking around, stepping away from your screen or simply changing activities can provide a brief pause between demanding tasks.
If you suddenly feel exceptionally focused, enjoy the momentum without assuming it will last indefinitely. Setting a natural stopping point can help prevent you from using every bit of available energy simply because you happen to be having a strong afternoon.
It may also help to schedule breaks before you feel like you need them, particularly on days filled with mentally demanding work.
The goal is not to eliminate fatigue or avoid productive periods. It is to recognize that how you feel right now may not perfectly predict how much capacity you will have later.
The bottom line
Your brain’s warning signs are not always obvious.
Feeling depleted can be a signal to ease your pace, but an unexpected burst of mental sharpness may also be worth noticing. New research suggests that both extremes can be followed by a reduced ability to keep going despite fatigue.
So the next time you find yourself flying through your workload at 3 p.m., you do not necessarily need to stop. But you may want to resist the assumption that feeling great means you have an endless supply of energy.
Sometimes, pacing yourself while you are still feeling good may be the smarter move.
