The impact of a short-period head-down tilt on executive function in younger adults.

Microgravity has been shown to be a significant stressor on the cardiovascular system and the brain due to the redistribution of fluids that occurs in the absence of gravitational force, but there is scarce literature surrounding the effects of microgravity on cerebral hemodynamics and cognition. Understanding the early effects that simulated gravity has on cognitive function is essential for developing proper physical and cognitive countermeasures to assure safe and effective cognitive/decisions making while astronauts prepare for the initial launch or when they arrive in a microgravity environment. Therefore, this study aims to determine how an acute simulation of microgravity would alter cerebral oxygenation and executive functions. Sixty-five young healthy participants (22 ± 6 years, 21 females) completed a thirty (30) minute horizontal (00 tilt) followed by a 90-min - 6° head-down-tilt (HDT) protocol. Cerebral oxygenation in the prefrontal cortex was monitored throughout the testing session using near-infrared spectroscopy. Cognition was also measured using a computerized Stroop Task. Our results demonstrate that cerebral oxygenation was higher during HDT compared to the horizontal supine position (9.11 ± 1.3 vs. 7.51 ± 1.8, p = 0.02). For the cognitive results, the non-executive performance of the Stroop task remained stable during HDT (652.46 ± 19.3 vs. 632.49 ± 14.5, p = 0.09). However, reaction time during the executive task performance was improved after the HDT (1058 ± 195-950 ± 158 ms, p < 0.01). Our results suggest that an acute bout of simulated microgravity can enhance executive functioning.

High-Intensity Interval Training Improves Cognitive Flexibility in Older Adults.

Introduction: Regular aerobic exercise is associated with better executive function in older adults. It is unclear if high-intensity-interval-training (HIIT) elicits moderate-intensity continuous training (MICT) or resistance training (RT). We hypothesized that HIIT would augment executive function more than MICT and RT. Methods: Sixty-nine older adults (age: 68 ± 7 years) performed six weeks (three days/week) of HIIT (2 × 20 min bouts alternating between 15 s intervals at 100% of peak power output (PPO) and passive recovery (0% PPO); n = 24), MICT (34 min at 60% PPO; n = 19), or whole-body RT (eight exercise superior improvements in executive function of older adults than moderate-intensity-continuous-training, 2 × 10 repetitions; n = 26). Cardiorespiratory fitness (i.e., V˙O2max) and executive function were assessed before and after each intervention via a progressive maximal cycle ergometer protocol and the Stroop Task, respectively. Results: The V˙O2max findings revealed a significant group by time interaction (p = 0.001) in which all groups improved following training, but HIIT and MICT improved more than RT. From pre- to post-training, no interaction in the naming condition of the Stroop Task was observed (p > 0.10). However, interaction from pre- to post-training by group was observed, and only the HIIT group exhibited a faster reaction time (from 1250 ± 50 to 1100 ± 50 ms; p < 0.001) in switching (cognitive flexibility). Conclusion: Despite similar improvements in cardiorespiratory fitness, HIIT, but not MICT nor RT, enhanced cognitive flexibility in older adults. Exercise programs should consider using HIIT protocols in an effort to combat cognitive decline in older adults.