Feelings of Energy And Fatigue: Two Different Moods

Until recently, most researchers had thought of energy feeling and feeling of fatigue as the opposite ends of the same continuum (e.g. if someone feels fatigued, they are not energetic, and vice versa). However, recent evidence suggests that feeling of energy and feeling of fatigue are two different, and perhaps overlapping moods (e.g. someone can feel fatigued and energetic simultaneously). This recent evidence has provided supporting data from studies that have examined genetic polymorphism in the DRD4 genes, mitochondrial function and its association with feelings of energy, blood serotonin, histamines, inflammatory cytokines, and sedentary behavior and its association with fatigue, and the role of sleep quality in influencing both feelings of energy and feelings of fatigue. This evidence has been presented in movement sciences as well, with Loy and colleagues (2013) reporting that feelings of fatigue improve with an acute bout of exercise when there is a moderate to large change in feelings of energy. Additionally, Boolani and colleagues (2019) reported that 6-minutes of self-paced physical activity increased feelings of physical energy and decreased feelings of mental fatigue only, but had no changes on mental energy and physical fatigue. While these are just some of the studies that have examined energy and fatigue as two distinct moods, further work is needed to better understand, whether energy and fatigue are distinct or overlapping moods, or opposite ends of the same continuum.

Recently, Loy and colleagues (2018) provided evidence that feeling of energy and feeling of fatigue are separate moods. Since then, researchers have found feeling of energy and feeling of fatigue to be associated with different biological and psychological variables. Additionally, several intervention studies have noted that certain interventions influence feelings of energy only or feelings of fatigue only. Therefore, this special issue calls for work that helps identify biomechanical, physiological, psychological, epigenetic, and immunological markers associated with feelings of energy only/feelings of fatigue only/both moods. Researchers can explore different interventions (i.e. sleep, nutrition, exercise, drug) and measure energy and fatigue as two separate moods to help identify factors that influence one or both moods. Additionally, besides a correlation study, there is limited literature available on the differences in the mental and physical aspect of energy and fatigue.

We would like to invite researchers to help identify biomechanical, physiological, immunological, psychological, and epigenetic factors associated with the feelings of energy or fatigue only, or both moods simultaneously. Additionally, we would like to invite researchers who examine interventions that influence feelings of energy or fatigue – only or both. We invite original research, case reports, reviews, systematic reviews and meta-analyses to this special edition.