Aquatic exercise allows the application of the physical stress theory for individuals who cannot tolerate the stresses of land-based exercises. The buoyancy of the water allows a deconditioned individual or an individual with significant joint pathology to exercise by decreasing the forces needed to move and decreasing the forces on the joint. Measurements of aquatic exercise are similar to land-based exercise. Target heart rate can be determined using the same formulas as for land-based exercise. However, because heart rate is lower in the pool, an “aquatic heart rate reduction” should be included in the formula. The heart rate reduction model was determined by Fernado Martins Kruel and is sometimes referred to as the Kruel protocol.83 An aquatic heart rate reduction is determined by subtracting a 1-minute in-pool heart rate from a 1-minute land-based heart rate. The difference is referred to as the aquatic reduction. Subjective perceived exertion scales can also be used to determine the intensity of an aquatic exercise program. Land-based functional assessments are used to determine the benefits of an aquatic exercise program.Attention deficit/hyperactivity disorder (ADHD), a prevalent neurodevelopmental disorder, has been associated with various structural and functional CNS abnormalities but findings about neurobiological mechanisms linking genes to brain phenotypes are just beginning to emerge. Despite the high heritability of the disorder and its main symptom dimensions, common individual genetic variants are likely to account for a small proportion of the phenotype's variance. Recent findings have drawn attention to the involvement of rare genetic variants in the pathophysiology of ADHD, some being shared with other neurodevelopmental disorders. Traditionally, neurobiological research on ADHD has focused on catecholaminergic pathways, the main target of pharmacological treatments. However, more distal and basic neuronal processes in relation with cell architecture and function might also play a role, possibly accounting for the coexistence of both diffuse and specific alterations of brain structure and activation patterns. This article aims to provide an overview of recent findings in the rapidly evolving field of ADHD neurobiology with a focus on novel strategies regarding pathophysiological analyses.