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Does CrossFit Impair Attentive Processes?

I recently caught up on the published literature pertaining to CrossFit training and decided to highlight this particular study (Perciavalle et al., 2016) as it possesses significant problems in both experimental design and results interpretation. This study sought to determine if CrossFit training results in negative effects on attention-related activities by virtue of high blood lactate levels. The underlying rationale is that high lactate levels were previously associated with negative effects on cognition (attention, memory) and CrossFit is known to raise lactate levels. Therefore, high levels of lactate may correlate with impaired cognitive ability.

The Takehome: This study presents us with many problems, the first of which is the premise. Asking whether CrossFit training will lead to attention deficits isn’t very novel. It’s known that exertion/fatigue impair cognitive function (memory, reaction time, etc.) So, the study hangs specifically on whether blood lactate levels can be correlated with poor attentional performance. However, the design does not use a correlation (regression) analysis – it compares means. In addition, the statistics applied to the comparison of the means (ANOVA) is inappropriate since the groups are simply different time points measured on the same individuals. An ANOVA requires that the groups be independent. Finally, the pool of participants had higher than normal baseline (before testing) lactate levels and were all on creatine supplementation, thereby adding additional variables the study did not explain or control for. Fortunately, the result of this study, that CrossFit training temporarily (until 15 minutes after training) impairs attentional performances, is not really novel or surprising. Therefore, the design and interpretation issues that cast doubt on the validity of this result won’t affect the broader field of study much at all.

STUDY DETAILS
Experimental Design:

  • 15 male CrossFitters were recruited for this study.
  • All participants were consuming Creatine daily (mean: 3.80+/-0.62g).
  • The CrossFit WOD 15.1 was used as the training stimulus. It consisted of 27-21-15-9 reps of Rowing (calories) and Thrusters (43kg barbell).
  • Measurements were taken at three time points: 5 min before the WOD, when the WOD ended, and 15 minutes after the WOD ended.
  • Physiological measurements included blood lactate and glucose levels.
  • Cognitive measurements included 1) Attention and Concentration Tasks (ACT) which is a series of tasks performed on a computer, 2) a Reaction Time (RT) test based on how quickly the participant can indicate when a symbol appears on a computer monitor, and 3) a selectivity of attention test was used which assessed audio and visual recognition while attention was split across two tasks.
  • A 1-way ANOVA was used to compare differences among groups (time points).

Results:

  • Levels of blood lactate before the training were significantly higher than levels that normally occur at rest.
  • Blood lactate levels increased significantly by the end of the training workout and returned to baseline by 15 minutes after.
  • Blood glucose did not change significantly as a result of training.
  • Reaction time, execution time, number of omissions, and number of errors were significantly increased at the end of training compared to before training. These values all returned to levels similar to baseline by 15 minutes after training.

Limitations:

  • No women were examined in this study (only men) and the age of the participants was not listed.
  • All participants were taking Creatine as a supplement, so any conclusions drawn can only be of the effect of CrossFit training AND Creatine supplementation. We cannot say the effect of CrossFit alone.
  • Use of a 1-Way ANOVA for statistical analysis assumes that the groups being compared are independent. If the same individuals are compared/present in all groups (as they were here), this violates the rules for use of an ANOVA. So, this approach is inappropriate. A repeated measures approach should have been used.
  • The question (hypothesis) being asked isn’t tested properly. To test for correlations between lactate levels and attention deficits, a regression analysis should have been conducted, not a comparison of means.
  • The conclusion of the study (athletes with high blood lactate before training who partake of CrossFit will have their attentional performances limited), does not match the question (hypothesis) of the study. It is a re-purposing of the work after the fact.
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