Title

The effects of exercise intensity and cognitive load on acute changes in attention and vigilance in healthy young adults

Author Identifiers

Benjamin Kan
ORCID: 0000-0002-2435-4829

Date of Award

2018

Degree Type

Thesis

Degree Name

Doctor of Philosophy

School

School of Medical and Health Sciences

First Advisor

Professor Kazunori Nosaka

Second Advisor

Professor Craig Speelman

Field of Research Code

1 1 0 6 0 2, 9 2 0 1 1 2

Abstract

Many studies have reported acute effects of exercise on cognition, and that exercise intensity is a key factor affecting post-exercise cognition. It appears that the cognitive load associated with exercise may also influence post-exercise cognition, but this has not been quantified. Little attention has been given to the cognitive aspect of attention and vigilance, and no previous study has investigated the effects of either exercise intensity or cognitive load, on post-exercise attention and vigilance. Therefore, this research project examined the effects of different cycling exercise intensities on post-exercise attention and vigilance (Study 1), assessed cognitive load associated with cycling exercise and investigated its effects on postexercise attention and vigilance changes (Study 2), and compared between eccentric and concentric cycling for cognitive load during exercise and its effects on post-exercise attention and vigilance changes (Study 3).

In Study 1, 26 healthy young adults (10 women) performed 20-min of either low- (30% peak power), moderate- (50%) and high-intensity (70%) cycling, or sat for 20-min (control) on a stationary ergometer, separated by week in a randomised order. To assess attention and vigilance, a 3-min sustained attention to response test (SART) was performed before and immediately, 15, 30, 45 and 60-min after each session. Although exercise intensity was significantly different between exercise sessions (p<0.01), no significant differences (p=0.372) were observed for changes in reaction time before and for 60-min among the four sessions. No significant interaction effect was evident between sessions for correct detection (p=0.723) and false alarm (p=0.354) scores. These results suggest that attention and vigilance were not influenced by exercise intensity.

In Study 2, the cognitive load associated with participant-controlled (PC) and computer-controlled (CC) cycling exercise, and its effects on attention and vigilance were investigated. The same participants as those in Study 1 performed the low-, moderate- and high-intensity cycling exercise for both PC and CC conditions. Cognitive load associated with exercise was assessed by the average of power errors from the target over ~1200 revolutions, a choice reaction time test (CRT) and the NASA-task load index (NASA-TLX). The SART was used to assess changes in attention and vigilance before and immediately after, and 15, 30, 45 and 60-min after each exercise session. Intensity of exercise was not different between PC and CC cycling conditions for low- (p=0.500), moderate- (p=0.959) and high-intensity (p=0.470). Although CRT was slower (p<0.05), and mental demand in NASA-TLX was greater (p<0.01) in PC than in CC for all three exercise intensities, CRT accuracy was found to be similar in both conditions. No significant difference in post-exercise attention and vigilance changes were found between PC and CC conditions. These findings suggest that PC and CC were similar in cognitive demand, resulting in no difference in their effects on changes in post-exercise attention and vigilance.

Study 3 compared the cognitive load between concentric (CONC) and two sessions of eccentric cycling (ECC1, ECC2) that is deemed to require a higher cognitive demand to perform, and its effects on post-exercise attention and vigilance. Thirty-one healthy young adults (9 women) performed a bout of 20-min CONC followed by two bouts of 20-min ECC (ECC1, ECC2) at the same workload (227.5 ± 51.5 W, 60-rpm) separated by a week. Cognitive load during both ECC and CONC was assessed by the same parameters as those in Study 2. ECC1 and ECC2 were less physically demanding than CONC (p<0.05), without a significant difference between ECC1 and ECC2. CRT was slower and less accurate for ECC1 and ECC2 than CONC, with no difference between ECC1 and ECC2. Torque error was also greater (p<0.05) for ECC1 and ECC2 than CONC, with more error (p<0.05) for ECC1 than ECC2. Attention and vigilance decreased 2-8% after 20-min sitting, but improved 2-10% immediately after ECC2, and did not decline from the baseline for 30 min after ECC1 or 60 min after CONC and ECC2 (P<0.05). These findings suggest that cognitive load was greater during ECC than CONC, and post-exercise attention and vigilance were maintained after all exercise sessions with a transient improvement only after ECC2.

In conclusion, this research project showed that cognitive load rather than exercise intensity in 20-min cycling exercise affected post-exercise attention and vigilance in healthy young adults. Future studies should investigate the effects of prolonged exposure to cognitively demanding exercise such as eccentric cycling on cognitive function.

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