The effects of a mid-morning bout of exercise on adolescents' cognitive function

The aim of the present study was to examine the effects of a mid-morning bout of exercise on adolescents’ cognitive function in a randomised crossover design where each participant completed two experimental trials. Forty-five adolescents (13.3±0.3 years old), undertook a bout of exercise (ten repeats of level one of the multi-stage fitness test, 30s rest between repeats; exercise trial) or continued to rest (resting trial). A battery of cognitive function tests assessing visuo-motor speed, executive function and working memory (visual search test, Stroop test and Sternberg paradigm, respectively) was completed 30 min before and 45 min following the exercise. Average heart rate during exercise was 172±17 beats/min. On the visual search test, there was a greater improvement in response times across the morning on the exercise trial (t=2.6, p=0.009). However, this improvement in response times was combined with a greater decrease in accuracy on the exercise trial (z=2.0, p=0.044). On the Sternberg paradigm there was a greater improvement in response times across the morning following exercise when compared to resting (t=2.6, p=0.010). The mid-morning bout of exercise did not affect Stroop test performance. These improvements in response times are most likely the result of a general speeding up of responses across several cognitive domains, because response times were improved similarly across two different domains and across all test complexity levels, rather than being restricted to the specific high cognitive load levels. Accordingly, exercise in school settings may help to improve cognitive function in adolescents during the school morning

Breakfast glycaemic index and cognitive function in adolescent school children

It has been suggested that a low-glycaemic index (GI) breakfast may be beneficial for some elements of cognitive function (e.g. memory and attention), but the effects are not clear, especially in adolescents. Thus, the aim of the present study was to examine the effects of a low-GI breakfast, a high-GI breakfast and breakfast omission on cognitive function in adolescents. A total of fifty-two adolescents aged 12–14 years were recruited to participate in the study. Participants consumed a low-GI breakfast, a high-GI breakfast or omitted breakfast. A battery of cognitive function tests was completed 30 and 120 min following breakfast consumption and capillary blood samples were taken during the 120 min postprandial period. The findings show that there was a greater improvement in response times following a low-GI breakfast, compared with breakfast omission on the Stroop (P=0·009) and Flanker (P=0·041) tasks, and compared with a high-GI breakfast on the Sternberg paradigm (P=0·013). Furthermore, accuracy on all three tests was better maintained on the low-GI trial compared with the high-GI (Stroop: P=0·039; Sternberg: P=0·018; Flanker: P=0·014) and breakfast omission (Stroop: P<0·001; Sternberg: P=0·050; Flanker: P=0·014) trials. Following the low-GI breakfast, participants displayed a lower glycaemic response (P<0·001) than following the high-GI breakfast, but there was no difference in the insulinaemic response (P=0·063) between the high- and low-GI breakfasts. Therefore, we conclude that a low-GI breakfast is most beneficial for adolescents' cognitive function, compared with a high-GI breakfast or breakfast omission

Sex differences in adolescents' glycaemic and insulinaemic responses to high and low glycaemic index breakfasts: a randomised control trial

During puberty young people undergo significant hormonal changes which affect metabolism and, subsequently, health. Evidence suggests there is a period of transient pubertal insulin resistance, with this effect greater in girls than boys. However, the response to everyday high and low glycaemic index (GI) meals remains unknown. Following ethical approval, forty adolescents consumed a high GI or low GI breakfast, in a randomised cross-over design. Capillary blood samples were taken during a 2-h postprandial period, examining the glycaemic and insulinaemic responses. Maturity offset and homoeostatic model assessment (HOMA) were also calculated. The glycaemic response to the breakfasts was similar between boys and girls, as shown by similar peak blood glucose concentrations and incremental AUC (IAUC) following both high and low GI breakfasts (all P> 0·05). Girls exhibited a higher peak plasma insulin concentration 30 min post-breakfast following both high GI (P=0·043, g=0·69) and low GI (P =0·010, g =0·84) breakfasts, as well as a greater IAUC following high GI (P=0·041, g =0·66) and low GI (P =0·041, g =0·66) breakfasts. HOMA was positively correlated with the insulinaemic responses (all P<0·0005) and maturity offset (P =0·037). The findings of the present study suggest that pubertal insulin resistance affects the postprandial insulinaemic responses to both high and low GI meals. Specifically, girls exhibit a greater insulinaemic response than boys to both meals, despite similar glycaemic responses. This study is the first to report the glycaemic and insulinaemic responses to everyday meals in boys and girls, supporting the recommendation for young people to base their diet on low GI carbohydrates