It’s an all-too familiar feeling: putting off working out or going to the gym because we’re mentally exhausted from the day and just can’t muster up the energy. But you might have to call time on that excuse. A new study published in the European Journal of Sport Science has shown that, even if mentally fatigued, subjects were still able to reach the same speeds in strength training and perform at the same RPE (rate of perceived exertion, or subjective intensity level), in an emerging area of research on the effects of cognitive exhaustion on resistance training.
How was the study conducted?
24 participants (14 females, 10 males) were asked to undertake several longer-length cognitive tasks to tire their minds out, including the Stroop test where, when presented with a coloured word, they had to say the word’s colour rather than read the word aloud.
The individuals were between 20 and 28 years old and had at least two years of recreational resistance-training experience, doing between two and four sessions per week and regularly performing back squats. None of them were competitive weightlifters.
Five sessions were held during the experiment, including one to determine participants’ one-rep back-squat max, and two sessions where they estimated the speed of a barbell repetition (perception of velocity): one where they were mentally tired and one where they weren’t, as a control session.
The test was conducted over two separate days: one day in a rested condition and one day in a mentally-fatigued state. Participants had to do two reps of a back squat at three different weights – light, medium and heavy – and the speed of the barbell was recorded. At the end of the sets, they had to identify the fastest rep of the two, estimate the speed of each rep, and report the effort level (RPE).
What were the results?
Mental fatigue did not damage participants’ ability to guess the fastest repetition. In fact, at rest, they correctly noted the fastest rep at 77.8% of the time, and after the mentally tiring exercise, 80.6% of the time.
The speed of the rep also remained constant for all three weights in both conditions, and the RPEs were very similar both while in the rested state and in the mentally fatigued state. For example, on a scale of 1-10, participants reported working at an effort level of 1.00 when lifting the light weight at a rested state, versus an effort level of 1.50 when doing the rep after the mentally fatiguing exercise.
Overall, despite a significant increase in mental exhaustion, both resistance-training performance and perception of barbell speed was not affected. However, it’s worth noting that the study is limited in its small sample size, meaning that the results may not be generalisable.
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