Hiking Time Trial Performance in the Heat with Real-Time Observation of Heat Strain, Hydration Status and Fluid Intake Behavior

Energy expenditure and physiological markers during a city mountain hike in the heat: A case study

Background: Energy expenditure may be difficult to assess when hiking difficult trails. Case presentation: We measured physical activity exercise energy expenditure (PAEE) directly from oxygen uptake using a mobile device (cardiopulmonary exercise testing, CPET), and by using a formula based on heart rate (HR), or metabolic equivalent values from the Compendium of Physical Activity, and other physiological outcomes. Outcomes and implications: Total PAEE (1342 kcal) using CPET showed a two-fold difference between ascending and descending (887 vs. 455 kcal) during a 124-min hike. For HR, PAEE was 1893kcal (+551 kcal overreporting), while compendium-based scenarios ranged from 1179 to 1446 kcal, which was in closer range (-163 to +104 kcal/min) compared to the CPET data. Fluid consumption was 1300 mL/hour, with 1.1% bodyweight loss, peak skin temperature of 35.2°C and core body temperature of 39.2°C. Recommendations: Tables reasonably predict energy expenditure while not precisely reflecting the actual situation.

Wilderness First Responder Medical Clearance - A Scoping Review with Recommendations

BACKGROUND AND PURPOSE

Due to environmental extremes, as well as the nature of the work itself, wilderness first responders are at risk of incurring medical events in the line of duty. There currently do not exist standardized and scientifically supported methods to screen for a wilderness first responder's risk of incurring a medical event.

METHODS

We performed multiple scoping reviews using PubMed and CINAHL. The reviews covered six medical screening criteria based on previous recommendations from the National Fire Protection Association (NFPA) and the US Forest Service, and we grouped our reviews into two categories: articles that addressed objective screening criteria, and articles that addressed subjective findings with the first responder.

RESULTS

Of the objective criteria, our reviews identified 21 articles addressing the ability to screen for risk of incurring a medical event by evaluation of a first responder's heart rate, 12 by blood pressure assessment, and 56 by assessment of body temperature. Of the subjective criteria we identified 19 articles focused on self-assessment, 34 articles on the use of standardized tools to assess for fatigue and sleepiness, and two articles on assessment of a first responder's urine to determine level of dehydration. We also identified seven additional articles through a hand search. Overall, there were 151 articles identified in our scoping reviews. These articles were largely of low quality, consisting mostly of case series without comparison groups.

CONCLUSION

There is a dearth of high-quality research into the medical assessment of first responders. We recommend that this paper, and measures discussed within it, be used as a starting point in the development of an evidence-based assessment protocol for wilderness first responders. We also recommend the development of a national database of medical events incurred by wilderness first responders to facilitate higher-quality research of screening protocols in this community.

Short hydration education video and hiker fluid selection and consumption at trails, a non-randomized quasi-experimental field study

Background: Education may improve hiker safety on trails. Aim: To investigate the impact of an educational video on hiker fluid selection and fluid consumption in a hot environment. Methods: Quasi-experimental field study at hiking trails in which the intervention group (INT) viewed a three-minute hydration education video, whereas the control group (CON) did not. Before the hike, all hikers were asked if they wanted to select extra fluid, which was provided by the research team. Results: A total of n = 97 hikers participated in the study, with n = 56 in INT (32 male) and n = 41 in CON (25 male). Despite absolute differences in environmental conditions, the differences fell within the same WBGT category. The total amount of fluid brought to the trails by participants was different between INT: 904 (503-1758) mL and CON: 1509 (880-2176) mL (P = 0.006), but participants in the INT group selected extra fluid (41%; n = 23) significantly more often when compared with participants in the CON group (7%; n = 3; P < 0.001). As a result, there was no difference in the amount of fluid brought on the trail between INT: 1047 (611-1936) mL and CON: 1509 (932-2176) mL (P = 0.069), nor for fluid consumption between INT: 433 (289-615) mL/h and CON: 489 (374-719) mL/h (P = 0.18). Conclusions and Implications: A 3-min educational video may encourage hikers to select additional fluid before the start of their hike but does not appear to increase fluid intake.