Whether you're working out in a gym or riding your bike outside, that dreaded moment of fatigue, when you just can't seem to get through it, feels the same. It turns out that a part of that fatigue may be in your head. And knowing exactly where it occurs in the brain could prompt performance-enhancing therapies in the future, according to a recent study in Nature Communications.
The researchers enlisted 20 study participants and asked them to repeatedly grasp and squeeze a sensor, varying their level of effort from minimal to maximal force. Using data from MRIs and computer models, they found that feelings of fatigue seem to arise from the motor cortex, the area of the brain responsible for controlling movement, according to study co-author Vikram Chib.
As an additional measure to determine how this affects brain function, the researchers offered the participants two options to proceed. One was considered more "risky," setting the amount of effort based on a coin toss offering the chance of no effort or a predetermined level of effort. The "safe" option was just the default level.
By introducing uncertainty, the researchers were able to see how much each participant valued their effort. That offered insight into whether people would choose to keep going, even when fatigued.
How does fatigue influence our decisions?
Unsurprisingly, the researchers found that people tend to be more risk averse to avoid exertion. All but one of the participants chose the safe option, and the scans indicated that for all, the motor cortex was turned off during the decision-making process.
This is consistent with previous studies indicating that when people become fatigued, motor cortex activity decreases, which can lead to sending fewer signals to muscles, leading to a reduction in power during a hard sprint, for example.
Will these findings lead to hack the motor cortex so that knocking becomes a thing of the past? Not yet, but it's not impossible either.
Scientists believe we could use non-invasive brain stimulation to align motor cortex activity with an individual's performance expectations. Another thing we could do is introduce cognitive strategies that could make people change the way they perceive effort, and this could influence motor cortical activity and make efforts feel less tiring.