Investigating the Inverted-U Relationship Between Cognitive Performance and Plasma Epinephrine

Investigating the Inverted-U Relationship Between Cognitive Performance and Plasma Epinephrine: A Registered Report of a Four-arm Crossover Randomized Controlled Trial

Abstract Although acute resistance exercise has been suggested to enhance inhibitory control, a critical component of executive function, the mechanism by which acute exercise influences inhibitory control is unclear and there are methodological limitations in previous empirical studies. According to the locus coeruleus-norepinephrine (LC-NE) theory, the activity of the LC, the major releaser of NE in the brain, regulates inhibitory control. Because there is reciprocal communication between circulating epinephrine and the LC. Plasma epinephrine is chosen as the index of LC-NE activity. However, only one study in acute exercise-inhibitory control measured the plasma epinephrine. Therefore, this registered report aims to extend its findings by a four-arm crossover randomized controlled design with three different intensities, using free-weight, multiple-joint, and structural resistance exercises. Moreover, most studies showed some methodological limitations such as failing to report the process of randomization, implementing a familiarization of resistance exercise before the maximal strength test, and publishing the protocol. Without a transparent report on how the participants were allocated, the results were at risk of bias. Without a familiarization of resistance exercise, the maximal muscle strength was likely to be underestimated. Without publishing the protocol before data collection, these findings were threatened by undetected researchers' degrees of freedom such as HARKing (hypothesizing after the results are known), cherry picking, and p-hacking. This registered report will address the limitations of previous studies by incorporating cognitive and resistance exercise familiarization, transparently reporting the randomization process, and submitting it as a registered report.

Inclusion Criteria:

1. healthy young male aged 18-40 years;
2. recreational resistance-trained (≥ 1 time/week for the previous 6 months);
3. free from cardiovascular, cerebrovascular, and neurological disorders and other chronic diseases;
4. free from any medical condition listed on the 2014 update of the Physical Activity Readiness Questionnaire (PAR-Q+);
5. non-smoker; and
6. normal or corrected-to-normal vision.

Exclusion Criteria:

1. athlete trained in a competitive sports team or engaging in exercise for more than 20 hours/week;
2. unable to perform any of the intervention exercises (barbell squat, press, and deadlift); or
3. color blind