Behavior Influencing Acute Hydration Status of Recreational Hikers in Hot and Moderate Weather Conditions

Annually, more than 200 hikers are rescued in the greater Phoenix area. This study examined behavior influencing acute hydration status in hot (HOT) and moderate (MOD) climates, by examining fluid planning and decision making in combination with an educational video. A total of n=115 hikers completed self-paced hikes, n=56 hikers completed the hike in a HOT condition (wet bulb globe temperature [WBGT]=24.84°C) and n=59 hikers completed the hike in a MOD condition (WBGT=8.28°C). Real food and fluid behavior allowed participants to freely select the amount of food and fluid brought on the hike and intake was ad libitum. The following heat stress indicators were all significantly higher in the HOT condition compared to MOD condition (HOT median, MOD median; p-value): hike duration (1.48, 1.20; p<0.01), energy expenditure (561, 408, p<0.01), sweat rate (776, 465, p<0.01), and session rating of perceived exertion (RPE) scores (1177, 732, p<0.01). After watching a 3-minute hydration education video, and the opportunity to stock up on extra fluid, 54% of participants carried sufficient fluid in the HOT condition to meet their needs compared to 81% of participants in the MOD condition. However, only 23% of participants in the HOT condition consumed sufficient fluid to make up for fluid lost through sweating compared to 33% in the MOD condition. More than half of participants in the HOT condition (59%) and the MOD condition (76%) did not stock up on extra fluid after education. These results demonstrate that hikers did not consume sufficient fluids to meet their needs while hiking, especially in a hot climate. They also show heat stress negatively affected hikers’ performance measures. More research is required to assess the feasibility and efficacy of hydration related education videos at trailheads.