• How Does the Brain Fatigue During Resistance Training?
    Three-dimensional mapping show the effect of strength and power training on the brain. From the Journal of Strength and Conditioning Research.
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  • Brain fatigueSynopsis

    Exercise recovery is growing in popularity almost as fast as the exercises themselves. What to eat? When to eat it? How long to rest? What exercises to avoid? 

    These are all common questions posed after intense training sessions, usually with the priority of curbing or reducing fatigue. Exercise is typically associated with muscular fatigue, and the potential for cortical (brain) fatigue is often neglected. A recent study in the Journal of Strength and Conditioning Research compared cortical fatigue for four different squat exercise protocols: 

    6 x 3 squat jumps at 30% 1RM (Power [PWR]) 
    6 x 3 squats at 95% 1RM (Force [FOR])
    6 x 10 squats at 80% 1RM (Volume [VOL])
    6 sets of unracking an empty bar (Control [CTRL]) 

    The seven subjects recruited for this study were all considered well-trained athletes with an average of six years of resistance training experience. Cortical fatigue was tested using an electroencephalogram (EEG), after a 24-hr recovery period from the exercise bout, while performing a maximal isometric squat. 

    Highlighted Results 

    Researchers hypothesized that different exercise protocols would result in different EEG activity before the study. Three-dimensional mapping of brain activity suggested that during recovery (while performing the maximal isometric squat), different exercise protocols (PWR, FOR, VOL, and CTRL) elicited varying levels of activity in different parts of the brain. However, when these brain activities were arranged together (referred to as global field power), no significant differences were recorded between exercise protocols. 

     Furthermore, no differences in force output during the maximal isometric squat were detected between groups. Despite the varying levels of activity in different brain regions, there was no evidence to suggest that a specific exercise protocol caused more cortical fatigue than another. The small sample size (n = 7) was a limitation of this study, but it still provided a chance for the researchers to look at the differences between types of athletes. 

    Three of the athletes participated in heavy load strength training preceding the inclusion in this study. This group showed increased cortical activity when performing the isometric squat 24 hr after the PWR and FOR days, as compared to CTRL days. The lighter load athletes did not display this effect. It is difficult to ascertain that heavy lifters are more susceptible to cortical fatigue, but the sample group in this study showed heightened levels of cortical activity when performing an isometric squat exercise which is usually considered less intense than a high-load squat. 

     Bottom line, cortical fatigue does not appear to deter performance 24 hr after an intense training session. Other fatigue causing factors such as lactate, cortisol, and muscle soreness may be more worthy of attention with respect to strength training.

  • Brain fatigue

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    1. Dunn-Lewis, C, Flanagan, S, Comstock, B, Maresh, C, Volek, J, Denegar, C, Kupchak, B, and Kraemer, W. Recovery patterns in electroencephalographic global field power during maximal isometric force production. J Strength Cond Res 25(10): 2818-2827, 2011.  

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