Abstract
Multiple studies suggest that genetic polymorphisms influence the neurocognitive effects of caffeine. Using data collected from a double-blinded, within-participants, randomized, cross-over design, this study examined the effects of trait (long-standing pre-disposition) mental and physical energy and fatigue to changes in moods (Profile of Mood Survey-Short Form (POMS-SF), state mental and physical energy and fatigue survey), cognitive (serial subtractions of 3 (SS3) and 7 (SS7)), and fine-motor task (nine-hole peg test) performance after consuming a caffeinated beverage and a non-caffeinated placebo. Results indicate that trait mental and physical fatigue and mental energy modified the effects of caffeine on vigor, tension-anxiety, physical, and mental fatigue. Additionally, we report that those who were high trait physical and mental fatigue and low-trait mental energy reported the greatest benefit of caffeine on the SS3 and SS7, while those who were high trait mental and physical fatigue reported the greatest benefit of consuming caffeine on fine-motor task performance. The results of our study suggest that trait mental and physical fatigue and mental energy modify the acute effects of caffeine among a group of healthy, young adults and should be measured and controlled for by researchers who choose to study the effects of caffeine on acute moods and cognitive and fine-motor task performance.
Highlights
Fatigue is a common, costly, and poorly understood problem, which affects approximately 45% of the United States (US) population [1]
We found that low trait mental fatigue and caffeine increased feelings of depression (β = −0.339, 95% CI: −0.632, Low trait mental energy and caffeine together decreased state physical fatigue (β = 5.40, 95% CI: −0.23, 6.35) and mental fatigue (β = 5.20, 95% CI: −0.27, 6.27), while alone neither had any statistically significant independent effect
Our results found that overall, those who were high trait physical and mental fatigue or low trait mental energy enjoyed the benefits of caffeine consumption on the serial subtraction 3 task, while caffeine only had an effect on participants who were high trait mental fatigue on the serial subtraction 7 task
Summary
Poorly understood problem, which affects approximately 45% of the United States (US) population [1]. Despite the high financial and social costs of fatigue, it is a poorly understood problem. Until recently, most researchers viewed energy and fatigue on a bipolar continuum (e.g., if an individual is not energetic, they are fatigued). Loy and colleagues [9] recently provided evidence that energy and fatigue are two distinct moods (e.g., an individual can be energetic and fatigued simultaneously), with multiple studies since showing that feelings of energy and fatigue are distinct yet overlapping constructs [10,11,12], with their own mental and physical components [13,14]. Additional research is needed to better understand the inter- and intra-individual differences in the efficacy of these interventions
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