Reaction time to peripheral visual stimuli during exercise under normoxia and hyperoxia

The effect of acute normobaric hyperoxia on cognition: a systematic review, meta-analysis and meta-regression

This systematic review, meta-analysis and meta-regression examined the effect of acute normobaric hyperoxia breathing on cognition in healthy humans. 23 studies were included providing 76 effect estimates (EE). Hyperoxic breathing improved memory accuracy (22 EEs; g = 0.34) and speed (9 EEs; g = 0.59), attention accuracy (7 EEs; g = 0.59) and speed (7 EEs; g = 0.51), reaction speed (8 EEs; g = 0.82), crystallised intelligence (7 EEs; g = 0.73), executive function (6 EEs; g = 0.88) and information processing (10 EEs; g = 0.62). However, the overall quality of evidence was low (average Rosendal score of 47%) and there was a large range of study heterogeneity, with prediction intervals often crossing 0; therefore, reducing the reliability of the magnitude of these favourable effects. Oxygen percentage, 100% compared with 22-99% oxygen, temporal position of administration to task performance, and study quality did not influence the overall weighted mean effects for most cognitive domains. Altogether, despite beneficial results, further high quality research is required prior to recommending hyperoxic breathing to enhance cognition.

Effects of Acute Aerobic Exercise on Cognition and Constructs of Decision-Making in Adults With and Without Hypertension

Hypertension accelerates brain aging, resulting in cognitive dysfunction with advancing age. Exercise is widely recommended for adults with hypertension to attenuate cognitive dysfunction. Whether acute exercise benefits cognitive function in this at-risk population is unknown. The purpose of this study was to compare the effects of acute aerobic exercise on cognitive function in 30 middle-aged hypertensive (HTN) and 30 age, sex, and body mass index (BMI)-matched non-HTN adults (56 ± 6 years, BMI 28.2 ± 2.9 kg/m²; 32 men). Subjects underwent cognitive testing pre/post 30-min cycling (≈55% peak oxygen consumption). Cognition was assessed using standard metrics of accuracy and reaction time (RT) across memory recognition, 2-back, and Flanker tasks. Behavioral data was further analyzed using drift-diffusion modeling to examine underlying components of decision-making (strength of evidence, caution, bias) and RT (non-decision time). Exercise elicited similar changes in cognitive function in both HTN and non-HTN groups (p > 0.05). Accuracy was unaltered for Flanker and 2-back tasks, while hits and false alarms increased for memory recognition post-exercise (p < 0.05). Modeling results indicated changes in memory hits/false alarms were due to significant changes in stimulus bias post-exercise. RT decreased for Flanker and memory recognition tasks and was driven by reductions in post-exercise non-decision time (p < 0.05). Our data indicate acute exercise resulted in similar, beneficial cognitive responses in both middle-age HTN and non-HTN adults, marked by unaltered task accuracy, and accelerated RT post-exercise. Additionally, drift-diffusion modeling revealed that beneficial acceleration of cognitive processing post-exercise (RT) is driven by changes in non-decision components (encoding/motor response) rather than the decision-making process itself.

The Impact of Hyperoxia on Human Performance and Recovery

Hyperoxia results from the inhalation of mixtures of gas containing higher partial pressures of oxygen (O₂) than normal air at sea level. Exercise in hyperoxia affects the cardiorespiratory, neural and hormonal systems, as well as energy metabolism in humans. In contrast to short-term exposure to hypoxia (i.e. a reduced partial pressure of oxygen), acute hyperoxia may enhance endurance and sprint interval performance by accelerating recovery processes. This narrative literature review, covering 89 studies published between 1975 and 2016, identifies the acute ergogenic effects and health concerns associated with hyperoxia during exercise; however, long-term adaptation to hyperoxia and exercise remain inconclusive. The complexity of the biological responses to hyperoxia, as well as the variations in (1) experimental designs (e.g. exercise intensity and modality, level of oxygen, number of participants), (2) muscles involved (arms and legs) and (3) training status of the participants may account for the discrepancies.

Fixating at far distance shortens reaction time to peripheral visual stimuli at specific locations

The purpose of the present study was to examine whether the fixation distance in real three-dimensional space affects manual reaction time to peripheral visual stimuli. Light-emitting diodes were used for presenting a fixation point and four peripheral visual stimuli. The visual stimuli were located at a distance of 45cm and at 25° in the left, right, upper, and lower directions from the sagittal axis including the fixation point. Near (30cm), Middle (45cm), Far (90cm), and Very Far (300cm) fixation distance conditions were used. When one of the four visual stimuli was randomly illuminated, the participants released a button as quickly as possible. Results showed that overall peripheral reaction time decreased as the fixation distance increased. The significant interaction between fixation distance and stimulus location indicated that the effect of fixation distance on reaction time was observed at the left, right, and upper locations but not at the lower location. These results suggest that fixating at far distance would contribute to faster reaction and that the effect is specific to locations in the peripheral visual field. The present findings are discussed in terms of viewer-centered representation, the focus of attention in depth, and visual field asymmetry related to neurological and psychological aspects.

Slowed response to peripheral visual stimuli during strenuous exercise

Recently, we proposed that strenuous exercise impairs peripheral visual perception because visual responses to peripheral visual stimuli were slowed during strenuous exercise. However, this proposal was challenged because strenuous exercise is also likely to affect the brain network underlying motor responses. The purpose of the current study was to resolve this issue. Fourteen participants performed a visual reaction-time (RT) task at rest and while exercising at 50% (moderate) and 75% (strenuous) peak oxygen uptake. Visual stimuli were randomly presented at different distances from fixation in two task conditions: the Central condition (2° or 5° from fixation) and the Peripheral condition (30° or 50° from fixation). We defined premotor time as the time between stimulus onset and the motor response, as determined using electromyographic recordings. In the Central condition, premotor time did not change during moderate (167±19ms) and strenuous (168±24ms) exercise from that at rest (164±17ms). In the Peripheral condition, premotor time significantly increased during moderate (181±18ms, P<0.05) and strenuous exercise (189±23ms, P<0.001) from that at rest (173±17ms). These results suggest that increases in Premotor Time to the peripheral visual stimuli did not result from an impaired motor-response network, but rather from impaired peripheral visual perception. We conclude that slowed response to peripheral visual stimuli during strenuous exercise primarily results from impaired visual perception of the periphery.

Pelvic instability and trunk and hip muscle recruitment patterns in patients with total hip arthroplasty

Hip and lumbar spine disorders often coexist in patients with total hip arthroplasty (THA). The current study aimed to reveal pelvic motion pathology and altered trunk and hip muscle recruitment patterns relating to pelvic motion in patients with THA. Twenty-one women who underwent THA and 12 age-matched healthy women were recruited. Pelvic kinematics and muscle recruitment patterns (i.e., amplitude, activity balance, and onset timing) of the gluteus maximus, semitendinosus, multifidus, and erector spinae were collected during prone hip extension. Compared with healthy subjects, the patients showed increased pelvic motion, especially ventral rotation, decreased multifidus muscle activity relative to the hip extensors, and delayed onset of multifidus activity, despite reaction times and speeds of leg motion not being significantly different between the groups. Furthermore, while contributing factors associated with ventral pelvic rotation were not found, delayed onset of multifidus activity was detected as a factor related to the increased anterior tilt of the pelvis (r = 0.47, p < 0.05) in patients with THA. These results suggest that patients with THA have dysfunction of the stabilizer muscles of the lumbopelvic region along with increased pelvic motion.

Balance of hip and trunk muscle activity is associated with increased anterior pelvic tilt during prone hip extension

Prone hip extension has been used as a self-perturbation task to test the stability of the lumbopelvic region. However, the relationship between recruitment patterns in the hip and trunk muscles and lumbopelvic kinematics remains unknown. The present study aimed to examine if the balance of hip and trunk muscle activities are related to pelvic motion and low back muscle activity during prone hip extension. Sixteen healthy participants performed prone hip extension from 30° of hip flexion to 10° of hip extension. Surface electromyography (of the gluteus maximus, semitendinosus, rectus femoris, tensor fasciae latae, multifidus, and erector spinae) and pelvic kinematic measurements were collected. Results showed that increased activity of the hip flexor (tensor fasciae latae) relative to that of hip extensors (gluteus maximus and semitendinosus) was significantly associated with increased anterior pelvic tilt during hip extension (r=0.52). Increased anterior pelvic tilt was also significantly related to the delayed onset timing of the contralateral and ipsilateral multifidus (r=0.57, r=0.53) and contralateral erector spinae (r=0.63). Additionally, the decrease of the gluteus maximus activity relative to the semitendinosus was significantly related to increased muscle activity of the ipsilateral erector spinae (r=-0.57). These results indicate that imbalance between the agonist and antagonist hip muscles and delayed trunk muscle onset would increase motion in the lumbopelvic region.

Does cerebral oxygenation affect cognitive function during exercise?

This study tested whether cerebral oxygenation affects cognitive function during exercise. We measured reaction times (RT) of 12 participants while they performed a modified version of the Eriksen flanker task, at rest and while cycling. In the exercise condition, participants performed the cognitive task at rest and while cycling at three workloads [40, 60, and 80% of peak oxygen uptake ([Formula: see text])]. In the control condition, the workload was fixed at 20 W. RT was divided into premotor and motor components based on surface electromyographic recordings. The premotor component of RT (premotor time) was used to evaluate the effects of acute exercise on cognitive function. Cerebral oxygenation was monitored during the cognitive task over the right frontal cortex using near-infrared spectroscopy. In the exercise condition, we found that premotor time significantly decreased during exercise at 60% peak [Formula: see text] relative to rest. However, this improvement was not observed during exercise at 80% peak [Formula: see text]. In the control condition, premotor time did not change during exercise. Cerebral oxygenation during exercise at 60% peak [Formula: see text] was not significantly different from that at rest, while cerebral oxygenation substantially decreased during exercise at 80% peak [Formula: see text]. The present results suggest that an improvement in cognitive function occurs during moderate exercise, independent of cerebral oxygenation.

Reaction time to peripheral visual stimuli during exercise under hypoxia

The purpose of this study was to test the hypothesis that decrease in cerebral oxygenation compromises an individual's ability to respond to peripheral visual stimuli during exercise. We measured the simple reaction time (RT) to peripheral visual stimuli at rest and during and after cycling at three different workloads [40%, 60%, and 80% peak oxygen uptake (VO2)] under either normoxia [inspired fraction of oxygen (FIO2)=0.21] or normobaric hypoxia (FIO2=0.16). Peripheral visual stimuli were presented at 10 degrees to either the right or the left of the midpoint of the eyes. Cerebral oxygenation was monitored during the RT measurement over the right frontal cortex with near-infrared spectroscopy. We used the premotor component of RT (premotor time) to assess effects of exercise on the central process. The premotor time was significantly longer during exercise at 80% peak VO2 (normoxia: 214.2+/-33.0 ms, hypoxia: 221.5+/-30.1 ms) relative to that at rest (normoxia: 201.0+/-27.2 ms, hypoxia: 202.9+/-29.7 ms) (P<0.01). Under normoxia, cerebral oxygenation gradually increased up to 60% peak VO2 and then decreased to the resting level at 80% peak VO2. Under hypoxia, cerebral oxygenation progressively decreased as exercise workload increased. We found a strong correlation between increase in premotor time and decrease in cerebral oxygenation (r2=0.89, P<0.01), suggesting that increase in premotor time during exercise is associated with decrease in cerebral oxygenation. Accordingly, exercise at high altitude may compromise visual perceptual performance.