Head-Down Tilt Bed Rest Improves Executive Function Amongst Younger Adults: A Pilot Project

Purpose 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. Methods 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. Results 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 msec to 950±158 msec, p<0.01). Conclusion Our results suggest that an acute bout of simulated microgravity can enhance executive functioning.

Cerebrovascular Response to an Acute Bout of Low-Volume High Intensity Interval Exercise and Recovery in Young Healthy Adults

Introduction: High intensity interval exercise (HIIT) is performed widely. However, there is a gap in knowledge regarding the acute cerebrovascular response to low-volume HIIT. Our objective was to characterize the middle cerebral artery blood velocity (MCAv) response during an acute bout of low-volume HIIT in young healthy adults. We hypothesized MCAv would decrease below baseline (BL) 1) during HIIT, 2) immediately following HIIT, 3) and 30-minutes after HIIT. As a secondary objective, we investigated sex differences in the MCAv response during HIIT. Methods: Twenty-four young healthy adults completed HIIT (12 male, age 25 (SD 2)). HIIT included 10-minutes of 1-minute high intensity (~70% estimated maximal watts) and active recovery (10% estimated maximal watts) intervals on a recumbent stepper. MCAv, mean arterial pressure (MAP), heart rate (HR), and end tidal carbon dioxide (PETCO2), were recorded at BL, during HIIT, immediately following HIIT, and 30-minutes after HIIT. Results: Contrary to our hypothesis, MCAv remained above BL during HIIT. MCAv peaked at minute 3 then decreased concomitantly with PETCO2. MCAv was lower than BL immediately following HIIT (p < 0.001). Thirty-minutes after HIIT, MCAv returned to BL (p = 0.47). Compared to men, women had a higher MCAv at BL (p = 0.001), during HIIT (p = 0.009), immediately following HIIT (p = 0.004) and 30-minutes after HIIT (p = 0.001). Conclusions: MCAv did not decrease below BL during low-volume HIIT. However, MCAv decreased below BL immediately following HIIT and returned to resting values 30-minutes after HIIT. MCAv also differed between sex.

Effects of menstrual cycle on appetite-regulating hormones and energy intake in response to cycling exercise in physically active women

Although ample evidence supports the notion that an acute bout of endurance exercise performed at or greater than 70% of maximum oxygen uptake suppresses appetite partly through changes in appetite-regulating hormones, no study has directly compared the influence between the phases of the menstrual cycle in women. The present study compared the effects of an acute bout of exercise on orexigenic hormone (acylated ghrelin) and anorexigenic hormones (peptide YY and cholecystokinin) between the early follicular phase (FP) and the mid luteal phase (LP) of the menstrual cycle in physically active women. Ten healthy women (age, 20.6 ± 0.7 years) completed two 3.5-h trials in each menstrual phase. In both trials, participants performed cycling exercises at 70% of heart rate reserve (at a corresponding intensity to 70% of maximum oxygen uptake) for 60 min followed by 90 min of rest. Following 90 min of rest, participants were provided with an ad libitum meal for a fixed duration of 30 min. Blood samples and subjective appetite were collected and assessed before, during, immediately post-, 45 min post-, and 90 min post-exercise. The exercise increased estradiol (327 %) and progesterone (681 %) in the LP more than the FP respectively (P < 0.001, f = 1.33; P < 0.001, f = 1.20). There were no between-trial differences in appetite-regulating hormones, subjective appetite, or energy intake of ad libitum meal. These findings indicate that exercise-induced increases in ovarian hormones in the LP may not influence appetite-regulating hormones in physically active women.

The Effects of 16 Weeks of Exercise Training on Neutrophil Functions in Breast Cancer Survivors

Following therapy, breast cancer survivors (BCS) have an increased risk of infections because of age and cancer dysregulation of inflammation and neutrophil functions. Neutrophil functions may be improved by exercise training, although limited data exist on exercise and neutrophil functions in BCS.Sixteen BCS [mean age: 56 (SD 11) years old] completed 16 weeks of community-based exercise training and a 45-minute acute bout of cycling before (Base) and after (Final) the exercise training program. Exercise training consisted of 3 x 40 – 60 minute mixed mode aerobic exercises, comprising 10 – 30 minutes aerobic and 30 minutes resistance training. At Base and Final, we took BCS blood samples before (PRE), immediately after (POST), and 1 hour after (1Hr) acute exercise to determine neutrophil counts, phenotype, bacterial killing, IL-6, and IL-8 levels. Eleven healthy, age- and physical activity levels-matched women (Control) completed the acute bout of exercise once as a healthy response reference. Resting Responses. BCS and Controls had similar Base PRE absolute neutrophil counts [mean (SD): 3.3 (1.9) v 3.1 (1.2) x 109/L, p=0.801], but BCS had lower bacterial phagocytosis [3991 (1233) v 4881 (417) MFI, p=0.035] and higher oxidative killing [6254 (1434) v 4709 (1220) MFI, p=0.005], lower CD16 [4159 (1785) v 7018 (1240) MFI, p&lt;0.001], lower CXCR2 [4878 (1796) v 6330 (1299) MFI, p=0.032] and higher TLR2 [98 (32) v 72 (17) MFI, p=0.022] expression, while IL-6 [7.4 (5.4) v 4.0 (2.7) pg/mL, p=0.079] levels were marginally higher and IL-8 [6.0 (4.7) v 7.9 (5.0) pg/mL, p=0.316] levels similar. After 16 weeks of training, compared to Controls, BCS Final PRE phagocytosis [4510 (738) v 4881 (417) MFI, p=0.146] and TLR2 expression [114 (92) v 72 (17) MFI, p=0.148] were no longer different. Acute Exercise Responses. As compared to Controls, at Base, BCS phagocytic Pre-Post response was lower [mean difference, % (SD): 12% (26%), p=0.042], CD16 Pre-Post response was lower [12% (21%), p=0.016] while CD16 Pre-1Hr response was higher [13% (25%), p=0.022], TLR2 Pre-Post response was higher [15% (4%) p=0.002], while IL-8 Pre-Post response was higher [99% (48%), p=0.049]. As compared to Controls, following 16 weeks of training BCS phagocytic Pre-Post response [5% (5%), p=0.418], CD16 Pre-1Hr response [7% (7%), p=0.294], TLR2 Pre-Post response [6% (4%), p=0.092], and IL-8 Pre-Post response [1% (9%), p=0.087] were no longer different. Following cancer therapy, BCS may have impaired neutrophil functions in response to an acute bout of exercise that are partially restored by 16 weeks of exercise training. The improved phagocytosis of bacteria in BCS may represent an exercise-induced intrinsic improvement in neutrophil functions consistent with a reduced risk of infectious disease.Clinical Trial RegistrationClinicalTrials.gov, identifier NCT03760536.

Concurrent Performance of Executive Function during Acute Bouts of Exercise in Adults: A Systematic Review

The purpose of the study was to systematically review the evidence on the effects of an acute bout of exercise on concurrent performance of core executive function (EF) during exercise in adults. Four electronic databases (i.e., PubMed, Web of Science, PsycINFO, and SportDiscus) were searched from inception dates to 30 December 2020. The literature searches were conducted using the combinations of two groups of relevant items related to exercise and executive function. Articles were limited to human studies in adults. The search process, study selection, data extraction, and study quality assessments were carried out independently by two researchers. A total of 4899 studies were identified. Twenty-two studies met our inclusion criteria. Of the 42 reported outcomes in the 22 studies, 13 (31%) of the 42 outcomes showed that core EF performance was enhanced during exercise and 14 (33%) found that core EF performance did not differ from control conditions. Fifteen (36%) found that core EF performance was impaired. Notably, improved EF performances tend to be observed during moderate-intensity exercise, whereas impaired EF performances were more likely to be observed at vigorous-high intensity. The review suggests mixed findings regarding the effects of an acute bout of exercise on concurrent performance of core EF. Exercise intensity seems to influence the effects. The underlying neural mechanisms remain to be elucidated.

A Comparison of the Effects of Foam Rolling and Stretching on Physical Performance. A Systematic Review and Meta-Analysis

Foam rolling and stretching with its various techniques are frequently used as a warm-up routine to increase the range of motion of a joint. While the magnitude of the changes in range of motion between foam rolling and stretching (static and dynamic techniques) is similar, it is not clear if this also holds true for performance parameters (e.g., strength, jump height). The purpose of this meta-analysis was to compare the effects of an acute bout of foam rolling (with and without vibration) with an acute bout of stretching (with all techniques included) on performance parameters in healthy participants. We assessed the results from 13 studies and 35 effect sizes by applying a random-effect meta-analysis. Moreover, by applying a mixed-effect model, we performed subgroup analyses with the stretching technique, type of foam rolling, tested muscle, treatment duration, and type of task. We found no significant overall effect, and the analysis revealed only a trend of the performance parameters in favor of foam rolling when compared to stretching (when considering all techniques). Significantly favorable effects of foam rolling on performance were detected with subgroup analyses when compared to static stretching, when applied to some muscles (e.g., quadriceps) or some tasks (e.g., strength), when applied for longer than 60 s, or when the foam rolling included vibration. When foam rolling was compared to dynamic stretching or applied in the non-vibration mode, the same magnitude of effect was observed. While the present meta-analysis revealed no significantly different effect between foam rolling and stretching (including all techniques) prior to exercise, differences could be observed under specific conditions.

EXPRESS: Evaluation of the Transient Hypofrontality Theory in the Context of Exercise: A Systematic Review with Meta-Analysis

Accumulating research suggests that, as a result of reduced neural activity in the prefrontal cortex (PFC), higher-order cognitive function may be compromised while engaging in high-intensity acute exercise, with this phenomenon referred to as the transient hypofrontality effect. However, findings in this field remain unclear and lack a thorough synthesis of the evidence. Therefore, the purpose of this meta-analysis was to evaluate the effects of in-task acute exercise on cognitive function, and further, to examine whether this effect is moderated by the specific type of cognition (i.e., PFC-dependent vs. non-PFC-dependent). Studies were identified by electronic databases in accordance with the PRISMA guidelines. In total, twenty-two studies met our inclusion criteria and intercept only meta-regression models with robust variance estimation were used to calculate the weighted average effect sizes across studies. Acute exercise at all intensities did not influence cognitive function (β = -0.16, 95% CI = [-0.58, 0.27], p = .45) when exercise occurred during the cognitive task, and no significant moderation effects emerged. However, there was evidence that cognitive task type (PFC-dependent vs. non-PFC-dependent) moderated the effect of high-intensity acute exercise on a concomitant cognitive performance (β = -0.81, 95% CI = [-1.60, -0.02], p = .04). Specifically, our findings suggest that PFC-dependent cognition is impaired while engaging in an acute bout of high-intensity exercise, providing support for the transient hypofrontality theory. We discuss these findings in the context of a cognitive-energetic perspective.