Acute psychosocial stress and working memory performance: the potential of physical activity to modulate cognitive functions in children.

BACKGROUND: Research suggests that physical activity (PA) enhances cognitive performance and prevents stress-related impairments of higher order cognitive functions like working memory (WM) performance. The aim of the current study was to investigate the effect of PA on WM performance after acute stress exposure in preadolescent children. METHODS: Regular PA was assessed for seven consecutive days during a typical school week using accelerometers in a sample of 44 preadolescent children (14 girls, Mage = 11.29 years, SDage = 0.67). Following this period, participants performed an automated operational span (OSPAN) task immediately after being exposed to the Trier Social Stress Test for Children (TSST-C). RESULTS: Children exhibited prototypical response slopes in salivary cortisol and salivary α-amylase as markers of the endocrine and autonomic stress response immediately after psychosocial stress induction. A subsequent two-way ANOVA comparing high- and low-stress responders revealed a significant interaction between group affiliation and PA level on WM performance for both stress markers. Interestingly, best WM performance was demonstrated in children showing both high PA levels and high cortisol (or low α-amylase, respectively) stress responses. CONCLUSIONS: Though patterns differed for salivary cortisol and salivary α-amylase, overall findings suggest that PA buffers the negative effects of stress on cognitive performance in children.

Habitual and acute exercise effects on salivary biomarkers in response to psychosocial stress.

OBJECTIVE: Previous research suggests beneficial effects of physical exercise on stress reactivity due to cross-stressor adaptions of physiological stress response systems. However, results remain inconclusive and it is unclear whether only regular engagement in exercise modulates these physiological adaptations or if acute bouts of exercise can elicit similar adaptations. Thus, the aim of the current study was to investigate and compare the effects of habitual and acute exercise on physiological stress responses. METHODS: 84 male participants between 18 and 30 years (half of them were screened to be habitually high active or low active) were randomized into one of two groups: either an acute exercise intervention group (n = 42 with 50% being habitually high active) which engaged in 30 min of moderate-to-high intensity ergometer bicycling, or a control (placebo exercise) group which engaged in 30 min of light stretching (n = 42 with 50% being habitually high active). Following the intervention period, participants took part in a well validated psychosocial stress paradigm. Saliva samples were taken repeatedly to derive alpha-amylase and cortisol as stress-specific parameters. A multilevel growth curve approach was applied to analyse changes in the stress parameters over time. RESULTS: Both, acute and habitual exercise have shown to be positively related to stress reactivity. In particular, a reduction in stress activation was found for both types of exercise, but only habitual engagement in exercise exhibited a beneficial effect on peak cortisol levels. CONCLUSIONS: Taken together, people can profit from regular exercise (i.e. reduced activity of stress-response systems). However, even acute bouts of exercise preceding stress exposure showed beneficial effects on stress reactivity. This finding is particularly important as it may provide a (self-)regulatory mechanism for people facing conceivable acute stress situations.

The effect of physical activity on sleep quality, well-being, and affect in academic stress periods.

The stress-buffering hypothesis postulates that physical activity and exercise can buffer the negative effects of (academic) stress on health. It still remains an open question whether students, who regularly engage in physical activity and exercise within their academic examination period, can successfully diminish these negative effects. Sixty-four subjects participated in this study and completed a total of five surveys, with T1 at the end of the semester break (baseline) and T2-T5 being presented every Friday in the last 4 weeks of the semester (examination period). They were asked to answer questions about their activity level, sleep quality, well-being and affect. Hierarchical linear models showed significant dependencies on time for all dependent measures. The expansion of the model for exercise also showed significant main effects of this predictor on well-being and positive affect (PA) and negative affect. Moreover, significant interactions with time for sleep quality and PA were found. Results suggest that physical activity and exercise in the academic examination period may be able to buffer the negative effects of stress on health-related outcomes. Therefore, activity levels should be maintained in times of high stress to prevent negative effects on sleep, well-being and affect in students.

How smart do you think you are? A meta-analysis on the validity of self-estimates of cognitive ability.

Individuals' perceptions of their own level of cognitive ability are expressed through self-estimates. They play an important role in a person's self-concept because they facilitate an understanding of how one's own abilities relate to those of others. People evaluate their own and other persons' abilities all the time, but self-estimates are also used in formal settings, such as, for instance, career counseling. We examine the relationship between self-estimated and psychometrically measured cognitive ability by conducting a random-effects, multilevel meta-analysis including a total of 154 effect sizes reported in 41 published studies. Moderator variables are specified in a mixed-effects model both at the level of the individual effect size and at the study level. The overall relationship is estimated at r = .33. There is significant heterogeneity at both levels (i.e., the true effect sizes vary within and between studies), and the results of the moderator analysis show that the validity of self-estimates is especially enhanced when relative scales with clearly specified comparison groups are used and when numerical ability is assessed rather than general cognitive ability. The assessment of less frequently considered dimensions of cognitive ability (e.g., reasoning speed) significantly decreases the magnitude of the relationship. From a theoretical perspective, Festinger's (1954) theory of social comparison and Lecky's (1945) theory of self-consistency receive empirical support. For practitioners, the assessment of self-estimates appears to provide diagnostic information about a person's self-concept that goes beyond a simple "test-and-tell" approach. This information is potentially relevant for career counselors, personnel recruiters, and teachers.