A new analysis of 9 studies involving 205 healthy participants looked at how mental fatigue affects resistance training. The researchers compared people who did a mentally demanding task before lifting weights with those who did a low-demand or passive activity.
The results showed that mental fatigue had a small to moderate negative effect on overall resistance exercise volume. The effect was stronger for multijoint exercises like squats and bench presses, and for moderate to high training volumes. For single-joint exercises, the effect was smaller and not statistically significant.
The evidence was rated as low quality, so the findings should be interpreted with caution. No safety concerns were reported in the included studies.
What does this mean for you? If you have a mentally tough day, your workout might suffer. But this doesn't mean you should skip training. Being aware of the potential impact can help you adjust your expectations or routine.