Cognitive Effects of Overtraining

Impulsive Decision Making

Overtraining can result in more impulsive decision-making. In one case, a group of triathletes in France participated in an intense cycling session (45 minutes long) before engaging in a cognitive behavior task. After they completed the task, the athletes had to make 3 different choices between delayed and monetary rewards within 5 seconds (such as choosing to earn €80 now, or earning €100 after 2 weeks).

The athletes who participated in the intense cycling session were more likely to select the immediate monetary rewards than a control group (Blain et al. 3291-3292). The researchers found that activity in the left MFG* was lowered in the triathletes’ brain scans, which reduced the brain’s ability to resist temptation (Blain et al. 3293)

*Left middle front gyrus (MFG) - Brain area responsible for choice-related activities

Slower Psychomotor Speed

Researchers have also found that overtraining can lead to impairments in psychomotor speed (the brain’s ability to maintain information and allocate attention). In one study, 7 athletes increased their training load by 15% for 2 weeks before engaging in a cognitive speed test. In the test, the athletes had to press computer keys after being presented with a stimulus. The athletes performed the test in simpler (such as pressing the keys with two fingers on the same hand) and complex conditions (such as pressing the keys with different fingers on different hands).

Compared to a control group, the athletes had similar results in the simpler conditions. However, the overtrained athletes performed worse in the more complex conditions than the control group (Rietjens et al. 24). Similar to the findings from another study, the researchers thus concluded that overtraining leads to fatigue in the motor cortex, which worsens the brain’s ability to handle complex cognitive motor tasks. (Rietjens et al. 24).

Decreased Memory

Another problem with overtraining is that it can lead to impairments in memory. Researchers in Indonesia divided adult male mice into 3 different exercise groups: a control group that performed no exercise, an aerobic group that performed mild exercise, and an overtraining group that performed excess amounts of exercise. The mice in the aerobic and overtraining groups first did an 11-week training session on a treadmill. After every week, mice in all groups did a memory test that required them to find a target in a Water T-Maze*.

In each week, the mice in the overtraining group not only took the longest amount of time to find the target, but they also made the most errors in finding it than the other groups. This means that the mice in the overtraining group were experiencing disturbances in their spatial memory capabilities (Parwata 27). The researchers found that overtraining lowered the BDNF* levels in the mice, which reduced their brains’ memory capacity (Parwata 27).

*Water T-Maze - T-shaped apparatus filled with 30 centimeters of water. Mice start at the base and swim to one of the ends containing a target. Used in experiments testing spatial memory.

*Brain-derived neurotropic factor (BDNF) - Brain protein that aids in long-term memory, spatial memory, and generation of new neurons

References

Blain, B., Schmit, C., Aubry, A., Hausswirth, C., Le Meur, Y., & Pessiglione, M. (2019a). Neuro-computational Impact of Physical Training Overload on Economic Decision-Making. Current Biology, 29(19), 3289-3297.e4. 10.1016/j.cub.2019.08.054

Parwata, N. M. R. (2020). Overtraining of aerobic physical exercise reduce rats (Rattus norvegicus) memory. Jurnal Profesi Medika, 14(1)10.33533/jpm.v14i1.1591

Rietjens, G. J., Kuipers, H., Adam, J., Saris, W. H. M., Breda, E. v., Hamont, D. v., & Keizer, H. A. (2005). Physiological, biochemical and psychological markers of strenuous training-induced fatigue. International Journal of Sports Medicine, 26(1), 16-26. 10.1055/s-2004-817914