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Psychological stress has been shown to increase intestinal permeability and is associated with the development of gastrointestinal disorders. This study aimed to investigate skydiving as an alternative model to analyse the effect of acute psychological stress on intestinal barrier function. Twenty healthy subjects participated in a tandem skydive followed by a negative control visit, of which 19 (9 females and 10 males, 25.9 ± 3.7 years) were included in the study. Intestinal permeability was assessed by a multi-sugar urinary recovery test. Sucrose recovery and lactulose/rhamnose ratio in 0-5h urine indicated gastroduodenal and small intestinal permeability, respectively, and sucralose/erythritol ratio in 5-24h urine indicated colonic permeability. Blood samples were taken to assess markers associated with barrier function. This study has been registered at ClinicalTrials.gov (NCT03644979) on August 23, 2018. Skydiving resulted in a significant increase in salivary cortisol levels directly after skydiving compared to the control visit. Cortisol levels were still increased two hours after landing, while cortisol levels before skydiving were not significantly different from the baseline at the control visit. Skydiving did not induce a significant increase in gastroduodenal, small intestinal or colonic permeability. There was also no significant increase in plasma intestinal and liver fatty acid-binding proteins, suggesting no damage to the enterocytes. These results show that the acute intense psychological stress induced by skydiving does not affect intestinal permeability in healthy subjects. Future models aiming to investigate the effect of stress on human intestinal barrier function should consider a more sustained exposure to the psychological stressor.

Psychological stress has been shown to increase intestinal permeability and is associated with the development of gastrointestinal disorders. This study aimed to investigate skydiving as an alternative model to analyse the effect of acute psychological stress on intestinal barrier function. Twenty healthy subjects participated in a tandem skydive followed by a negative control visit, of which 19 (9 females and 10 males, 25.9 ± 3.7 years) were included in the study. Intestinal permeability was assessed by a multi-sugar urinary recovery test. Sucrose recovery and lactulose/rhamnose ratio in 0-5h urine indicated gastroduodenal and small intestinal permeability, respectively, and sucralose/erythritol ratio in 5-24h urine indicated colonic permeability. Blood samples were taken to assess markers associated with barrier function. This study has been registered at ClinicalTrials.gov (NCT03644979) on August 23, 2018. Skydiving resulted in a significant increase in salivary cortisol levels directly after skydiving compared to the control visit. Cortisol levels were still increased two hours after landing, while cortisol levels before skydiving were not significantly different from the baseline at the control visit. Skydiving did not induce a significant increase in gastroduodenal, small intestinal or colonic permeability. There was also no significant increase in plasma intestinal and liver fatty acid-binding proteins, suggesting no damage to the enterocytes. These results show that the acute intense psychological stress induced by skydiving does not affect intestinal permeability in healthy subjects. Future models aiming to investigate the effect of stress on human intestinal barrier function should consider a more sustained exposure to the psychological stressor.

To analyse the data on skydiving deaths and injuries collected prospectively by the French Parachuting Federation (FFP) between 2010 and 2019. Prospective cohort study. Data on number of skydiving deaths and injuries were collected prospectively between January 2010 and December 2019, among all skydivers licensed to the FFP, via a standardised report form that included the skydiver’s sex and level of experience (classified as tandem, student, or experienced), deaths, injuries, and injury location. The number of licensees, jumps, skydiving deaths and injuries were analysed descriptively and expressed as rates per 100,000 jumps and per 1000 skydivers with 95% confidence intervals (95%CI). Among the almost 6.2 million jumps performed by 519,620 skydivers over 10 years between 2010 and 2019, 35 deaths and 3015 injuries were reported, corresponding to 0.57 deaths (95%CI 0.38 to 0.75) and 49 injuries (95%CI 47.0 to 50.1) per 100,000 jumps. Male skydivers had a five times higher deaths rate than women (RR=4.8, 95%CI 1.5 to 15.6). There was no death in tandem skydivers. Student skydivers had a six times higher risk of injuries than experienced skydivers (RR=6.1, 95%CI 5.7 to 6.6) and tandem skydivers had a significant lower risk of injuries than experienced skydivers (RR=0.07, 95%CI 0.06 to 0.08). 83.3% of the injuries occurred during the landing phase and 64.3% concerned the lower limb. This large survey shows that the highest risk of death concerned experienced and male skydivers, and the highest risk of injuries concerned student skydivers. It also shows the safety of tandem skydiving. These results can be of help to develop skydiving-related deaths and injuries risk reduction strategies, and thus improve the global skydiving safety and the skydivers’ health.

Springtails (Collembola) have been traditionally portrayed as explosive jumpers with incipient directional takeoff and uncontrolled landing. However, for these collembolans that live near the water, such skills are crucial for evading a host of voracious aquatic and terrestrial predators.We discover that semiaquatic springtails, Isotomurus retardatus, can perform directional jumps, rapid aerial righting, and near-perfect landing on the water surface. They achieve these locomotive controls by adjusting their body attitude and impulse during takeoff, deforming their body in midair, and exploiting the hydrophilicity of their ventral tube, known as the collophore. Experiments and mathematical modeling indicate that directional-impulse control during takeoff is driven by the collophore’s adhesion force, the body angle, and the stroke duration produced by their jumping organ, the furcula. In midair, springtails curve their bodies to form a U-shape pose, which leverages aerodynamic forces to right themselves in less than ∼20 ms, the fastest ever measured in animals. A stable equilibrium is facilitated by the water adhered to the collophore. Aerial righting was confirmed by placing springtails in a vertical wind tunnel and through physical models. Due to these aerial responses, springtails land on their ventral side ∼85% of the time while anchoring via the collophore on the water surface to avoid bouncing. We validated the springtail biophysical principles in a bioinspired jumping robot that reduces in-flight rotation and lands upright ∼75% of the time. Thus, contrary to common belief, these wingless hexapods can jump, skydive, and land with outstanding control that can be fundamental for survival.

A bstract We study families of semidefinite programs (SDPs) that depend nonlinearly on a small number of “external” parameters. Such families appear universally in numerical bootstrap computations. The traditional method for finding an optimal point in parameter space works by first solving an SDP with fixed external parameters, then moving to a new point in parameter space and repeating the process. Instead, we unify solving the SDP and moving in parameter space in a single algorithm that we call “skydiving”. We test skydiving on some representative problems in the conformal bootstrap, finding significant speedups compared to traditional methods.

Anhedonia (loss of pleasure) is characterized by low responsiveness to rewards and, by virtue of being one of the two core symptoms of depression, by altered responses to stress. We investigated the effect of an acute stress experience (i.e., a tandem skydive) that was expected to elicit both intense fear and intense euphoria in a sample of anhedonic young adults. (1) To examine individual differences in alpha-amylase reactivity to and recovery from a tandem skydive in anhedonic young adults; (2) to investigate whether trait depressive and anxiety problems, trait positive affect (PA), i.e., level of pleasure and reward responsiveness, and state anxiety, PA and self-esteem prior to the skydive were associated with alpha-amylase reactivity and recovery patterns; (3) to investigate whether alpha-amylase reactivity and recovery patterns were associated with pre- to post-jump changes in state anxiety, PA, and self-esteem. Alpha-amylase reactivity and recovery patterns were highly similar across individuals, although mean levels varied greatly. No associations were found between any of the trait and state measures and reactivity and recovery. Only state self-esteem was affected by the reactivity and recovery patterns, in that individuals who showed high reactivity and low recovery experienced decreases in self-esteem after the skydive. Alpha-amylase patterns following a tandem skydive in anhedonic individuals are highly similar to patterns previously found in healthy individuals. Although replication is warranted, our findings tentatively suggest that a strong stress response that cannot be downregulated well predicts a decrease in self-esteem.

Anhedonia (loss of pleasure) is characterized by low responsiveness to rewards and, by virtue of being one of the two core symptoms of depression, by altered responses to stress. We investigated the effect of an acute stress experience (i.e., a tandem skydive) that was expected to elicit both intense fear and intense euphoria in a sample of anhedonic young adults. (1) To examine individual differences in alpha-amylase reactivity to and recovery from a tandem skydive in anhedonic young adults; (2) to investigate whether trait depressive and anxiety problems, trait positive affect (PA), i.e., level of pleasure and reward responsiveness, and state anxiety, PA and self-esteem prior to the skydive were associated with alpha-amylase reactivity and recovery patterns; (3) to investigate whether alpha-amylase reactivity and recovery patterns were associated with pre- to post-jump changes in state anxiety, PA, and self-esteem. Alpha-amylase reactivity and recovery patterns were highly similar across individuals, although mean levels varied greatly. No associations were found between any of the trait and state measures and reactivity and recovery. Only state self-esteem was affected by the reactivity and recovery patterns, in that individuals who showed high reactivity and low recovery experienced decreases in self-esteem after the skydive. Alpha-amylase patterns following a tandem skydive in anhedonic individuals are highly similar to patterns previously found in healthy individuals. Although replication is warranted, our findings tentatively suggest that a strong stress response that cannot be downregulated well predicts a decrease in self-esteem.

Psychological stress has been shown to increase intestinal permeability and is associated with the development of gastrointestinal disorders. This study aimed to investigate skydiving as an alternative model to analyse the effect of acute psychological stress on intestinal barrier function. Twenty healthy subjects participated in a tandem skydive followed by a negative control visit, of which 19 (9 females and 10 males, 25.9 ± 3.7 years) were included in the study. Intestinal permeability was assessed by a multi-sugar urinary recovery test. Sucrose recovery and lactulose/rhamnose ratio in 0-5h urine indicated gastroduodenal and small intestinal permeability, respectively, and sucralose/erythritol ratio in 5-24h urine indicated colonic permeability. Blood samples were taken to assess markers associated with barrier function. This study has been registered at ClinicalTrials.gov (NCT03644979) on August 23, 2018. Skydiving resulted in a significant increase in salivary cortisol levels directly after skydiving compared to the control visit. Cortisol levels were still increased two hours after landing, while cortisol levels before skydiving were not significantly different from the baseline at the control visit. Skydiving did not induce a significant increase in gastroduodenal, small intestinal or colonic permeability. There was also no significant increase in plasma intestinal and liver fatty acid-binding proteins, suggesting no damage to the enterocytes. These results show that the acute intense psychological stress induced by skydiving does not affect intestinal permeability in healthy subjects. Future models aiming to investigate the effect of stress on human intestinal barrier function should consider a more sustained exposure to the psychological stressor.

From frogs remaining airborne using their webbed feet to lizards and snakes gliding by expanding their ribcages, biologists might have thought they had seen every unusual aerial strategy — but now they report flying salamanders. Salamanders can descend through air in a controlled manner.