Restrictions in working memory capacity during parachuting: a possible cause of ‘no pull’ fatalities

'I actually thought that I was going to die': Lessons on the rip current hazard from survivor experiences

BACKGROUND

Rip currents are strong, narrow, fast-flowing currents of water that occur on many beaches and in Australia contributing to 26 drowning deaths and several thousand lifeguard/lifesaver rescues each year. Educating the public about the rip current hazard is a primary focus of beach safety practitioners, but there has been a lack of qualitative research exploring the firsthand experiences of being caught in a rip current to assist in this regard. The aim of this study was to analyse interviews of rip current survivors to understand more about how people react when unintentionally caught in a rip current in order to help guide future public education to mitigate rip current drowning.

METHODS

Semi-structured interviews were conducted with 56 individuals (primarily Australian-born) about their experience of being caught in a rip current. Interviewees were recruited via an online survey and varied in age and self-reported swimming ability.

RESULTS

Thematic analysis revealed three key temporal elements to the rip current experience: Before the Rip in which lack of awareness and knowledge, complacency, over-confidence, and attitude were prevalent themes; During the Rip which identified panic and temporary inhibition of decision-making, physical response, prior experience, and relationships with other beach users as themes; and After the Rip where post-rip effects and rip safety messaging and education were key themes. The importance of experiential immersion was a prevalent thread throughout all phases of the thematic analysis.

DISCUSSION

Our research shows that being caught in a rip current can be an intense and traumatic experience and that lessons learned from survivors have significant implications for improving existing and future rip current education efforts. In this regard, we provide several recommendations based on evidence-based insights gained from our interviews including the development of immersive rip current experience using virtual reality.

SO WHAT

Despite the prevalence of rip currents causing drowning deaths and rescues, there has been a lack of qualitative research on firsthand experiences to aid in public education. These interviews emphasise the intense and traumatic nature of being caught in a rip current, underscoring the need for improved rip current education to aid in prevention of this, often harrowing, experience.

Analysis of the Objective Internal Load in Portuguese Skydivers in the First Jump of the Day

The general objective of this study was to identify the variation in heart rate (HR) of Portuguese skydivers during 6 moments in their first jump of the day, bearing in mind the variable level of experience. Thirty-one Portuguese skydivers, 28 men and 3 women, aged between 19 and 62, participated in the study, 12 had A and B licenses (less experienced) and 19 had C and D licences (more experienced). The instrument used to record the heart rate of the skydivers at the different moments of their first jump of the day was the WIMU PRO. A repeated measures analysis of variance was used to analyse HR at different moments in the jump and its relation with the variables level of experience. Bonferroni multiple comparisons were performed to study the importance of the differences observed in HR at the different moments. The effect size was evaluated with partial eta squared. The results showed that average HR in this group of skydivers was 130 bpm, in the different moments of the jump. HR increases from the value recorded at rest until the moment of jumping from the plane and opening the parachute, reaching the highest average at that moment, then decreasing until contact with the ground. Comparing the variable, we found that the less experienced had higher HR than the more experienced at all moments during the jump. Statistically significant differences were found at the different moments of the jump, regarding HR (Max: p < 0.001, ƞ2p = 0.820; Min: p < 0.001, ƞ2p = 0.821; AVG: p < 0.001, ƞ2p = 0.834) Level of experience with jumping moment interaction, we only verified differences related to HR Min (p = 0.007, ƞ2p = 0.056),. With regard to experience, the identified differences were not statistically significant. Skydiving triggers an acute adaptive cardiovascular response which is reflected in the increase in the HR, between the moment of boarding the plane and the moment at which the parachute opens, thereafter decreasing until contact with the ground. The most experienced parachutists recorded the highest HR at the moment of landing and the least experienced at the moment of free fall.

A Concise Psychometric Tool to Measure Personal Characteristics for Surviving Natural Disasters: Development of a 16-Item Power to Live Questionnaire

The ability of individuals to manage and rebuild their lives after a disaster depends on environmental factors, as well as their own psychological characteristics. A psychometric questionnaire to measure personality traits relevant to disaster survival was proposed based on a large-scale investigation of survivors of the 2011 Great East Japan Earthquake (Sugiura et al. 2015). This tool, the Power to Live with Disasters questionnaire, measures eight personality characteristics that are beneficial for coping with disasters. However, this instrument has not been optimised for practical use; it is long and lacks benchmark scores for the general population. Thus, we developed a concise, 16-item version of the Power to Live with Disasters questionnaire through reanalysis of the 2011 Great East Japan Earthquake survivor data and an additional Web-based survey to obtain normative data from 1200 respondents drawn from the general population of Japan. The scores obtained from the short-form version of the questionnaire successfully replicated the results of the long-form version; eight distinct personality characteristics correlated well with several items associated with “successful survival” of the 2011 earthquake and tsunami. The normative data of the full- and short-version questionnaires were also highly correlated. We propose use of the shortened questionnaire to determine the personality traits critical for survival in the face of unexpected, life-threatening situations caused by natural disasters. Our questionnaire could be useful in schools and other public settings to enhance disaster-mitigation efforts and resilience to disasters in the general population.

Jump and free fall! Memory, attention, and decision-making processes in an extreme sport

In the present study, we explored the effects of high arousal on cognitive performance when facing a situation of risk. We also investigated how these effects are moderated by either positive or negative emotional states (valence). An ecological methodology was employed, and a field study was carried out in a real-life situation with 39 volunteer participants performing a bungee jumping activity and a control group of 39 participants. Arousal and valence were assessed with the Self-Assessment Manikin (SAM). Working memory capacity (reverse digit span), selective attention (Go/No-Go task) and decision-making (Iowa Gambling Task) were assessed at 3 time points: 30 min before the jump, immediately after the jump, and approximately 8 min after the onset of the previous phase. The results indicate that high arousal accompanied by high positive valence scores after jumping either improved performance or led to a lack of impairment in certain cognitive tasks. The Processing-Efficiency and the Broaden-and-Build theories are put forward to explain emotional moderation of cognitive performance in potentially life-threatening situations.

Coping related variables, cardiac vagal activity and working memory performance under pressure

The aim of this study was to assess the predictive role of coping related variables (trait emotional intelligence and reinvestment, challenge and threat appraisals and cardiac vagal activity) on cardiac vagal activity and working memory under low pressure (LP) and high pressure (HP) conditions. Participants (n = 49) completed trait questionnaires, the Decision Specific Reinvestment Scale, the Movement Specific Reinvestment Scale and Trait Emotional Intelligence Questionnaire. They realized the automated span task, which tests working memory, under counterbalanced LP and HP conditions. Cardiac vagal activity measurements were taken at rest, task and post task for 5 min, along with self-reported ratings of stress. Upon completion of the task, self-report measures of motivation, stress appraisal, attention and perceived pressure were completed. Current findings suggest cardiac vagal activity at rest can predict cardiac vagal activity under pressure, decision reinvestment influences cardiac vagal activity in cognitive tasks under LP and working memory performance is predicted by task cardiac vagal activity in HP only. These results show the importance of combining both subjective and objective psychophysiological variables in performance prediction and strengthen the need for this approach to be adopted across samples.

The Physiology of Paragliding Flight at Moderate and Extreme Altitudes

Wilkes, Matt, Martin J. MacInnis, Lucy A. Hawkes, Heather Massey, Clare Eglin, and Michael J. Tipton. The physiology of paragliding flight at moderate and extreme altitudes. High Alt Med Biol 19:42-51, 2018.-Paragliding is a form of free flight, with extreme-altitude paragliding being an emerging discipline. We aimed to describe the physiological demands and the impact of environmental stressors of paragliding at moderate and extreme altitudes. We recorded oxygen consumption (VO₂), heart rate (HR), respiratory frequency (fR), tidal volume (V_T), oxygen saturation, accelerometry (G), and altitude in 9.3 hours of flight at moderate altitudes (to 3073 m, n = 4), 19.3 hours at extreme altitude (to 7458 m, n = 2), and during high-G maneuvers (n = 2). We also analyzed HR data from an additional 17 pilots (138 hours) using the Flymaster Live database to corroborate our findings. All pilots were male. Overall energy expenditure at moderate altitude was low [1.7 (0.6) metabolic equivalents], but physiological parameters were notably higher during takeoff (p < 0.05). Pilots transiently reached ∼7 G during maneuvers. Mean HR at extreme altitude [112 (14) bpm] was elevated compared to moderate altitude [98 (15) bpm, p = 0.048]. Differences in pilots' V_T and fR at moderate and extreme altitudes were not statistically significant (p = 0.96 and p = 0.058, respectively). Thus, we conclude that physical exertion in paragliding is low, suggesting that any subjective fatigue felt by pilots is likely to be cognitive or environmental. Future research should focus on reducing mental workload, enhancing cognitive function, and improving environmental protection.

No Long-Term Effect of Physical Activity Intervention on Working Memory or Arithmetic in Preadolescents

We investigate if increased physical activity (PA) leads to enhanced working memory capacity and arithmetic performance, in a 2-year school-based intervention in preadolescent children (age 6–13). The active school (n = 228) increased PA (aimed at increasing cardiovascular fitness) from 2 to 5 days a week while the control school (n = 242) remained at 2 days. Twice a year, participants performed tests of arithmetic as well as verbal and spatial working memory. They also rated stress with a questionnaire at the start and at the end of the intervention. There was no beneficial development of working memory or arithmetic for the active school as compared to the control school. Furthermore, subgroup analyses revealed no favorable intervention effect for high/low baseline fitness, cognition or grit. Unexpectedly, a significant increase in self-rated stress was detected for the active school and this effect was driven by girls rather than boys and by the younger rather than older children. These results indicate that longtime high intensity PA does not lead to a beneficial development of working memory or arithmetic in preadolescent children.

Can false memories prime alternative solutions to ambiguous problems?

Research has demonstrated that false memories are capable of priming and facilitating insight-based problem-solving tasks by increasing solution rates and decreasing solution times. The present research extended this finding by investigating whether false memories could be used to bias ambiguous insight-based problem-solving tasks in a similar manner. Compound remote associate task (CRAT) problems with two possible correct answers, a dominant and a non-dominant solution, were created and normed (Experiment 1). In Experiment 2, participants were asked to solve these CRAT problems after they were given Deese/Roediger-McDermott lists whose critical lures were also the non-dominant solution to half of the corresponding CRATs. As predicted, when false memories served as primes, solution rates were higher and solution times were faster for non-dominant than dominant CRAT solutions. This biasing effect was only found when participants falsely recalled the critical lure, and was not found when participants did not falsely recall the critical lure, or when they were not primed. Results are discussed with regard to spreading activation models of solution competition in problem-solving tasks and current theories of false memory priming effects.

Heart rate variability and critical flicker fusion frequency changes during and after parachute jumping in experienced skydivers

PURPOSE

The purpose of this study was (1) to further explore the heart rate dynamics and assess a potential cardiovascular risk in response to 4000 m jumps in experienced skydivers; (2) to assess whether there is an impact of such jumps on skydivers' cortical arousal or not, which may impact their decision making processes.

METHOD

18 experienced skydivers performed successive jumps from a plane at 4000 m of height. Heart rate dynamics and cortical arousal were assessed by the use of heart rate variability and Critical Flicker Fusion Frequency (CFFF), respectively.

RESULTS

CFFF did not differ between the three measurement time points (p > 0.05). Mean heart rate increased during the jump (p < 0.001) and came back to pre-jump values after the jump (p < 0.001). Percentage of the differences of successive NN intervals greater than 50 ms (pNN50) decreased during the jump (p < 0.001) and kept lower values after the jump compared to pre-jump (p < 0.05). High-frequency power (HF) did not differ during the jump (p > 0.05) but decreased after the jump compared to both pre-jump (p < 0.01) and jump (p < 0.05). Sample entropy decreased during the jump (p < 0.001) and came back to pre-jump values after the jump (p > 0.05).

CONCLUSION

These results confirm a vagal input reduction associated with a rise of the sympathetic tone during the jump and suggests that the experienced skydiver is not exposed to a high cardiovascular risk. This study also shows that environmental stresses induced by free fall could not hamper the perceptual vigilance of experienced skydivers.

Anxiety mediates the effect of acute stress on working memory performance when cortisol levels are high: a moderated mediation analysis

BACKGROUND

Anxiety is an aversive emotional state characterized by perceived uncontrollability and hypervigilance to threat that can frequently cause disruptions in higher-order cognitive processes like working memory. The attentional control theory (ACT) predicts that anxiety negatively affects the working memory system.

DESIGN

This study tested the association between anxiety and working memory after the addition of stress and measured the glucocorticoid, cortisol. To better understand this relationship, we utilized a moderated mediation model.

METHODS

Undergraduate students from a public university (N = 103) self-reported their anxiety levels. Participants first completed a short-term memory test. During and after a forehead cold pressor task (stress vs. control procedure) participants completed a working memory test. Salivary cortisol was taken at baseline and after the last working memory test.

RESULTS

Overall, acute stress had no effect on working memory. However, we found that anxiety levels mediated the influence of condition (stressed vs. control) on working memory, but only among those individuals who had high cortisol levels after exposure to acute stress, supporting a moderated mediation model.

CONCLUSIONS

These results imply that activation of the hypothalamic-pituitary-adrenal axis was necessary for working memory impairment in anxious individuals. These results provide support for the ACT.

The relationship between working memory, reinvestment, and heart rate variability

There is growing evidence illustrating the negative aspects of reinvestment on everyday life, however its underlying mechanisms remain unclear. The main aim of this study was to empirically clarify the relationship between reinvestment and working memory (WM). A secondary aim was to investigate the contribution of high-frequency heart rate variability (HF-HRV) to WM. Sixty-two participants took part in a within-subject design in which we measured their WM capacity in a low-pressure and a high-pressure condition while their HF-HRV was measured. In addition, they had to fill out scales assessing their dispositional reinvestment. Results showed that the correlation between reinvestment and WM is negative, exists only in the high-pressure condition, and is specific to the decision component of reinvestment and not the movement component. Moreover, a hierarchical regression analysis revealed that under high pressure resting HF-HRV predicted WM performance above DSRS, whereas DSRS did not predict WM performance above resting HF-HRV.

Glucose changes and working memory in individuals with type 1 diabetes during air pressure changes simulating skydiving

BACKGROUND

Several countries restrict individuals with type 1 diabetes mellitus (T1DM) from skydiving because of concerns over possible alterations in consciousness. To our knowledge, glucose levels and working memory in individuals with T1DM during skydiving have not been assessed earlier. The objective of this study was to investigate changes in glucose levels and working memory in selected subjects with T1DM compared with control subjects without diabetes mellitus (DM) during ambient air pressure changes as those anticipated during standard skydiving.

SUBJECTS AND METHODS

Six subjects with T1DM and six controls were included. Using a hypobaric chamber, the ambient air pressure was changed to simulate a standard skydive from 4,000 m (13,000 feet) above mean sea level. The procedure was repeated six times to mimic a day of skydiving activity with a median of 8.7 h/day (5(th), 95(th) percentile: 8.1, 9.8 h). All subjects carried a continuous glucose monitor (CGM). Capillary glucose tests were taken in order to calibrate the CGM. Hemoglobin oxygen saturation, heart rate, and working memory, evaluated through digit span, were monitored regularly.

RESULTS

No subject experienced documented symptomatic hypoglycemia with impaired working memory during the simulations. One asymptomatic hypoglycemia episode with a plasma glucose level of <3.9 mmol/L was recorded in a subject with T1DM, with a corresponding CGM trend indicating declining glucose levels. Interstitial glucose levels of <3.9 mmol/L were recorded by CGM in three of the controls during the simulations. There were no significant differences in hemoglobin oxygen saturation, heart rate, or working memory between the T1DM patients and the controls.

CONCLUSIONS

This study of interstitial glucose levels and working memory could not show the activity-specific risk factor (i.e., repetitive rapid-onset hypobaric hypoxia exposures) to be a greater safety concern for selected subjects with T1DM compared with subjects without DM during a simulated day of skydiving. Further studies are needed to clarify the suitability of subjects with T1DM to participate in this air sport.

State anxiety and cortisol reactivity to skydiving in novice versus experienced skydivers

Previous studies have suggested that skydiving, a naturalistic stressor, is associated with increases in self-reported stress, anxiety and cortisol levels. However, it has not been established whether this stress reactivity is altered as a function of repeated exposure to skydiving. This is of interest due to previous observations that cortisol reactivity becomes habituated with repeated exposure to laboratory stressors, however, few studies have investigated such habituation to naturalistic stressors. State anxiety and cortisol reactivity to skydiving were measured in 11 first-time skydivers and 13 experienced skydivers (≥30 jumps, mean jumps=397.6), who were to complete a solo skydive. The novice skydivers reported significantly greater levels of state anxiety prior to the jump; however, there were no differences in pre-jump levels of salivary cortisol. Both groups exhibited significantly elevated salivary cortisol levels immediately post-jump, relative to i) pre-jump and ii) recovery. However, the two groups were indistinguishable with regard to their cortisol reactivity to the skydive. These findings support previous research demonstrating that skydiving elicits acute cortisol activation. Further, they suggest that i) cortisol reactivity does not habituate in experienced jumpers, and ii) that there is lack of concordance between self-reported levels of anxiety and biological stress reactivity in experienced skydivers.