Is there an acute exercise-induced physiological/biochemical threshold which triggers increased speed of cognitive functioning? A meta-analytic investigation

PurposeThe purpose of this study was to examine, using meta-analytic measures, the evidence regarding the optimal exercise intensity at which improvements in speed of cognitive function are triggered. Specifically, it was hypothesized that the catecholamine, lactate, and ventilatory thresholds is the point at which significant improvements in speed of cognitive function are observed.MethodsWe compared mean effect sizes for threshold studies and for those studies where exercise intensity was classed as moderate (40%–79% VO2max or equivalent) but in which the thresholds were not measured.ResultsRandom effects meta-analysis showed significant, moderate, mean effect sizes for studies at the threshold (g = 0.58, Z = 2.98, p < 0.003) and for those during moderate intensity exercise but in which the threshold was not measured (g = 0.54, Z = 5.01, p < 0.001). There was no significant difference between mean effect sizes, which suggests that the thresholds are unlikely to represent a trigger point.ConclusionModerate intensity exercise, even below the thresholds, can induce improved speed of cognition, possibly due to a combination of increased peripheral catecholamine concentrations inducing vagal/nucleus tractus solitarii pathway activation and central increases due to perceptions of stress.