Terry McMorris

Acute, intermediate intensity exercise, and speed and accuracy in working memory tasks: A meta-analytical comparison of effects

The purpose of this study was to compare, using meta-analytic techniques, the effect of acute, intermediate intensity exercise on the speed and accuracy of performance of working memory tasks. It was hypothesized that acute, intermediate intensity exercise would have a significant beneficial effect on response time and that effect sizes for response time and accuracy data would differ significantly. Random-effects meta-analysis showed a significant, beneficial effect size for response time, g=-1.41 (p<0.001) but a significant detrimental effect size, g=0.40 (p<0.01), for accuracy. There was a significant difference between effect sizes (Z(diff)=3.85, p<0.001). It was concluded that acute, intermediate intensity exercise has a strong beneficial effect on speed of response in working memory tasks but a low to moderate, detrimental one on accuracy. There was no support for a speed-accuracy trade-off. It was argued that exercise-induced increases in brain concentrations of catecholamines result in faster processing but increases in neural noise may negatively affect accuracy.

Differential effects of differing intensities of acute exercise on speed and accuracy of cognition: A meta-analytical investigation

The primary purpose of this study was to examine, using meta-analytical techniques, the differential effects of differing intensities of acute exercise on speed and accuracy of cognition. Overall, exercise demonstrated a small, significant mean effect size (g=0.14, p<0.01) on cognition. Examination of the comparison between speed and accuracy dependent variables showed that speed accounted for most of the effect. For speed, moderate intensity exercise demonstrated a significantly larger mean effect size than those for low and high intensities. For speed of processing during moderate intensity exercise, central executive tasks showed a larger effect size than recall and alertness/attention tasks; and mean effect size for counterbalanced or randomized studies was significantly greater than for studies in which a pre-exercise followed by during or post-exercise protocol was used. There was no significant difference between mean effect sizes when testing took place post-exercise compared to during exercise for speed but accuracy studies demonstrated a significantly larger mean effect size post-exercise. It was concluded that increased arousal during moderate intensity exercise resulted in faster speed of processing. The very limited effect on accuracy may be due to the failure to choose tests which are complex enough to measure exercise-induced changes in accuracy of performance.

The effect of exercise on cognitive performance in soccer-specific tests

Two experiments were carried out to examine the effect of moderate and maximal exercise on the cognitive performance of experienced soccer players. Experiment 1 examined the speed and visual search in familiar (game) and unfamiliar (non-game) contexts. Participants had to detect, as quickly as possible, the presence or absence of a ball in tachistoscopically presented slides. Participants were tested at rest and while exercising at 70 and 100% maximum power output. A main effect of exercise intensity was demonstrated and Tukey post-hoc tests showed that performance during maximal exercise was significantly better than in the other two conditions. We concluded that exercise significantly improves speed of visual search. Experiment 2 examined the effects of exercise on speed of search, speed of decision following ball detection, overall speed of decision and accuracy of decision at rest and while exercising at 70 and 100% maximum power output. A repeated-measures multivariate analysis of variance and Tukey post-hoc tests showed that performance during exercise was significantly better than at rest. Observation of the separate univariate analyses of variance demonstrated that most of the variance could be accounted for by overall speed of decision and speed of decision after ball detection. We concluded that exercise induces not only an improvement in a simple task, like speed of visual search, but also an overall increase in speed of information processing. Theories concerning the effect of emotionally induced arousal on cognitive performance do not accurately predict the effect of physically induced arousal on cognitive tasks.

A test of the catecholamines hypothesis for an acute exercise–cognition interaction

The purpose of the study was to examine the usage of norepinephrine (NE) and dopamine (DA) in the brain when exercising while simultaneously undertaking cognitive tests. Plasma concentrations of the NE metabolite 3-methoxy 4-hydroxyphenylglycol (MHPG) and the DA metabolite homovanillic acid (HVA) showed a linear increase from rest to exercising at 40% and 80% maximum power output (W.max) while simultaneously undertaking cognitive tasks (random number generation (RNG) and response time). Delta plasma concentrations of MHPG and HVA at each exercise intensity while undertaking cognitive tasks and while exercising without cognitive tasks did not differ. Taking blood samples at 0, 1, 3, and 5 min following cessation of exercise did not affect results. Regression correlations showed that delta MHPG and HVA plasma concentrations at the 1 and 3 min sampling times were strong predictors of delta RNG, response time and movement time. Reaction time at 80% W.max significantly increased, while movement time at 80% W.max significantly decreased. It was concluded that these results provide no support for a direct effect of increased catecholamines concentrations on cognitive performance during exercise. The regression data suggest that there is some relationship between exercise, catecholamines concentrations and cognition.

Specific effects of acute moderate exercise on cognitive control

The main issue of this study was to determine whether cognitive control is affected by acute moderate exercise. Twelve participants [4 females (VO(2 max)=42 ml/kg/min) and 8 males (VO(2 max) = 48 ml/kg/min)] performed a Simon task while cycling at a carefully controlled workload intensity corresponding to their individual ventilatory threshold. The distribution-analytical technique and the delta plot analysis [Ridderinkhof, K. R. (2002). Activation and suppression in conflict tasks: Empirical clarification through distributional analyses. In W. Prinz & B. Hommel (Eds.), Common mechanisms in perception and action. Attention and performance (Vol. 19, pp. 494-519). Oxford: Oxford University Press.] were used to assess the role of selective response inhibition in resolving response conflict. Results showed that cognitive processes appeared to be differently affected by acute moderate exercise. Reaction time results confirmed that performance is better (faster without change in accuracy) when the cognitive task is performed simultaneously with exercise. Between-trial adjustments (post-conflict and post-error) highlighted that cognitive control adjustments are also fully efficient during exercise. However, the effect of congruency (Simon effect) appeared to be more pronounced during exercise compared to rest which suggests that the response inhibition is deteriorated during exercise. The present findings suggest that acute moderate exercise differently affects some specific aspects of cognitive functions.

EFFECT OF EXERCISE ON SIMPLE REACTION TIMES OF RECREATIONAL ATHLETES

To examine the effect of moderate and fatiguing exercise on the simple reaction times of recreational athletes, 12 subjects took a simple reaction-time test while at test and while cycling on a Monark cycle ergometer at 70% and 100% of maximum workload. To estimate 70% and 100% of maximum workload the subjects underwent a standard incremental test until exhaustion, defined as subjects being unable to maintain the required pedal rate of 70 rpm. Simple reaction time during maximal exercise was significantly slower than in the other two conditions which did not differ significantly from one another. Heart rate and rate of perceived exertion differed significantly for all three conditions.

Dehydration affects brain structure and function in healthy adolescents

It was recently observed that dehydration causes shrinkage of brain tissue and an associated increase in ventricular volume. Negative effects of dehydration on cognitive performance have been shown in some but not all studies, and it has also been reported that an increased perceived effort may be required following dehydration. However, the effects of dehydration on brain function are unknown. We investigated this question using functional magnetic resonance imaging (fMRI) in 10 healthy adolescents (mean age = 16.8, five females). Each subject completed a thermal exercise protocol and nonthermal exercise control condition in a cross‐over repeated measures design. Subjects lost more weight via perspiration in the thermal exercise versus the control condition (P < 0.0001), and lateral ventricle enlargement correlated with the reduction in body mass (r = 0.77, P = 0.01). Dehydration following the thermal exercise protocol led to a significantly stronger increase in fronto‐parietal blood‐oxygen‐level‐dependent (BOLD) response during an executive function task (Tower of London) than the control condition, whereas cerebral perfusion during rest was not affected. The increase in BOLD response after dehydration was not paralleled by a change in cognitive performance, suggesting an inefficient use of brain metabolic activity following dehydration. This pattern indicates that participants exerted a higher level of neuronal activity in order to achieve the same performance level. Given the limited availability of brain metabolic resources, these findings suggest that prolonged states of reduced water intake may adversely impact executive functions such as planning and visuo‐spatial processing. Hum Brain Mapp, 2010.

Acute incremental exercise, performance of a central executive task and sympathoadrenal system and hypothalamic-pituitary adrenal axis activity

The purposes of this study were to examine the effect of acute incremental exercise on the performance of a central executive task; the responses of the sympathoadrenal system (SAS) and hypothalamic-pituitary-adrenal axis (HPAA) during exercise, while simultaneously carrying out the central executive task; and the ability of Delta plasma concentrations of epinephrine, norepinephrine, adrenocorticotropin hormone (ACTH) and cortisol to predict Delta performance on the central executive task. Subjects undertook a flanker task at rest and during exercise at 50% and 80% maximum aerobic power (MAP). SAS and HPAA activity were measured pre- and post-treatment by plasma concentrations of catecholamines, and cortisol and ACTH, respectively. Reaction time (RT) and number of errors for congruent and incongruent trials on the flanker task showed significant main effects with performance at 80% MAP higher than in the other conditions. RT post-correct responses were significantly faster than RT post-error at rest and 50% MAP but not at 80%. Pre- and post-treatment catecholamines showed a main effect of exercise with a linear increase. Post-treatment ACTH concentrations at 80% MAP were significantly greater than in the other conditions. Delta epinephrine and ACTH combined were significant predictors of Delta RT and Delta norepinephrine was a significant predictor of Delta number of errors. It was concluded that exercise must be at a high intensity to affect performance on the flanker task. Both the SAS and HPAA appear to play a role in the exercise-cognition interaction.

Effects of Acute Dehydration on Brain Morphology in Healthy Humans

Dehydration can affect brain structure which has important implications for human health. In this study, we measured regional changes in brain structure following acute dehydration. Healthy volunteers received a structural MRI scan before and after an intensive 90‐min thermal‐exercise dehydration protocol. We used two techniques to determine changes in brain structure: a manual point counting technique using MEASURE, and a fully automated voxelwise analysis using SIENA. After the exercise regime, participants lost (2.2% ± 0.5%) of their body mass. Using SIENA, we detected expansion of the ventricular system with the largest change occurring in the left lateral ventricle (P = 0.001 corrected for multiple comparisons) but no change in total brain volume (P = 0.13). Using manual point counting, we could not detect any change in ventricular or brain volume, but there was a significant correlation between loss in body mass and third ventricular volume increase (r = 0.79, P = 0.03). These results show ventricular expansion occurs following acute dehydration, and suggest that automated longitudinal voxelwise analysis methods such as SIENA are more sensitive to regional changes in brain volume over time compared with a manual point counting technique. Hum Brain Mapp 2009.

Anticipation of Professional Soccer Goalkeepers When Facing Right-and Left-Footed Penalty Kicks:

The purpose of this study was to examine the anticipation of professional soccer goalkeepers when facing right- and left-footed penalty kicks. Subjects were shown a videotape of 10 right-footed and 10 left-footed penalty kicks. A standard temporal occlusion paradigm was used, with each penalty being presented at 3 occlusion points, 2 frames before foot-ball contact, at the moment of foot-ball contact, and 2 frames after foot-ball contact. A 2-way (foot X occlusion point) analysis of variance (with repeated measures) indicated that anticipation to right-footed kicks was significantly better than that to left-footed kicks. There were no other significant results. Post hoc interviews indicated that the subjects claimed to use angle of approach to the ball, foot position at contact, and hip position at the time of foot-ball contact as the main cues to aid anticipation.