The headline is truncated and thereby misleading. The full headline is: "Brief aerobic exercise immediately enhances visual attentional control and perceptual

The headline is truncated and thereby misleading. The full headline is: "Brief aerobic exercise immediately enhances visual attentional control and perceptual speed. Testing the mediating role of feelings of energy" In other words, this study took some amount of cognitive enhancement across the subjects as a given and was designed to test for a correlation between that effect and reports of feeling energized by exercise, which the authors did report finding. If the numbers and methodology back that up, it suggests a couple of obvious (and not mutually exclusive) possibilities: 1) There is a primarily psychological mechanism, with the belief that a practice is energizing being a key factor. Note that the control group practiced relaxation techniques, which is arguably the opposite of an energizing practice. 2) Both the experience of feeling energized and the increase in cognitive performance are mediated by some physiological difference in exercise response. For example, it may be that some portion of the population has subclinical exercise intolerance (which is mostly studied in relation to cardiovascular disease, but has also been linked to mitochondrial dysfunction, neurological conditions, and sleep apnea).