Steroid hormones in the saliva of adolescents after different exercise intensities and their influence on working memory in a school setting

Little is known, about the influence of different exercise intensities on cognition, the concentration of steroid hormones (SHs), and their interaction in adolescents. Sixty high school students from the 9th grade were randomly assigned to two experimental (EG 1, EG 2) and a control group (CG). Saliva collection took place after a normal school lesson (t1) and after a 12-min resting control or exercise (t2) in a defined heart rate (HR) interval (EG 1: 50–65% HR max, n=18; EG 2: 70–85% HR max, n=20; CG: no intervention, n=21). Saliva was analyzed for T and C. Cognitive performance was assessed using a working memory task (Letter Digit Span; LDS), which took place after t1 and t2. Repeated measure ANOVAs revealed a significant group by test interaction, indicating an increase of C and T level only for EG 2. Results for LDS showed a significant improvement due to exercise when groups were split into low and high performer at pre-test with a higher improvement of the low performers. In addition, post-test T levels negatively correlated with changes in LDS performance in EG 2. The results indicate that the concentrations of C and T are intensity dependent, and that exercise improves working memory in low performing adolescents. Only increased T, however, seems to be related to pre-to-post-test changes in working memory by having a detrimental effect on performance.