Water and sodium intake habits and status of ultra-endurance runners during a multi-stage ultra-marathon conducted in a hot ambient environment: an observational field based study

Abstract

BackgroundAnecdotal evidence suggests ultra-runners may not be consuming sufficient water through foods and fluids to maintenance euhydration, and present sub-optimal sodium intakes, throughout multi-stage ultra-marathon (MSUM) competitions in the heat. Subsequently, the aims were primarily to assess water and sodium intake habits of recreational ultra-runners during a five stage 225 km semi self-sufficient MSUM conducted in a hot ambient environment (Tmax range: 32°C to 40°C); simultaneously to monitor serum sodium concentration, and hydration status using multiple hydration assessment techniques.MethodsTotal daily, pre-stage, during running, and post-stage water and sodium ingestion of ultra-endurance runners (UER, n = 74) and control (CON, n = 12) through foods and fluids were recorded on Stages 1 to 4 by trained dietetic researchers using dietary recall interview technique, and analysed through dietary analysis software. Body mass (BM), hydration status, and serum sodium concentration were determined pre- and post-Stages 1 to 5.ResultsWater (overall mean (SD): total daily 7.7 (1.5) L/day, during running 732 (183) ml/h) and sodium (total daily 3.9 (1.3) g/day, during running 270 (151) mg/L) ingestion did not differ between stages in UER (p < 0.001 vs. CON). Exercise-induced BM loss was 2.4 (1.2)% (p < 0.001). Pre- to post-stage BM gains were observed in 26% of UER along competition. Pre- and post-stage plasma osmolality remained within normal clinical reference range (280 to 303 mOsmol/kg) in the majority of UER (p > 0.05 vs. CON pre-stage). Asymptomatic hyponatraemia (<135 mmol/L) was evident pre- and post-stage in n = 8 UER, corresponding to 42% of sampled participants. Pre- and post-stage urine colour, urine osmolality and urine/plasma osmolality ratio increased (p < 0.001) as competition progressed in UER, with no change in CON. Plasma volume and extra-cellular water increased (p < 0.001) 22.8% and 9.2%, respectively, from pre-Stage 1 to 5 in UER, with no change in CON.ConclusionWater intake habits of ultra-runners during MSUM conducted in hot ambient conditions appear to be sufficient to maintain baseline euhydration levels. However, fluid over-consumption behaviours were evident along competition, irrespective of running speed and gender. Normonatraemia was observed in the majority of ultra-runners throughout MSUM, despite sodium ingestion under benchmark recommendations.

Gut-training: the impact of two weeks repetitive gut-challenge during exercise on gastrointestinal status, glucose availability, fuel kinetics, and running performance

“…Dietary intake and exercise training were monitored for three days before GC1 and throughout the gut-training protocol. Energy and nutritional intake was assessed and analysed as previously reported (Costa et al 2013;. Additionally, to check and confirm compliance, participants were asked to complete a gut-training adherence and completion log throughout the gut-training period.…”

“…Despite carbohydrate intake rates of 78 g·h -1 (1:1:1 glucose-fructose-maltodextrin) during 2 h of steady state exercise being reported to be generally well tolerated in response to a 20 km cycling time trial and in a cycling focused population (Smith et al 2013), field-based studies report average ad libitum carbohydrate intakes during a marathon of 35 g·h -1 , and ultra-marathon events ranging from 24 to 37 g·h -1 , irrespective of ultra-marathon runners carrying multiple-transportable carbohydrate rich foods and fluids equating to >60 gCHO·h -1 in the latter (Costa et al 2013;Pfeiffer et al 2012). …”

Ultramarathon Running: Medical Issues

“…In a 5-stage 225 km multi-stage ultra-marathon where athletes competed at temperatures of up to 40 °C, the prevalence of exercise-associated hyponatremia amounted to 42% [11]. In the 2008 'Rio Del Lago 100-Mile Endurance Run' in Granite Bay, California, the prevalence of exercise-associated hyponatremia was at 51.2% [64].…”

“…Exercise-associated hyponatremia is a rather frequently found electrolyte disorder in ultramarathoners [11,[61][62][63] where high ambient temperatures might be of high importance [11,64]. In a 5-stage 225 km multi-stage ultra-marathon where athletes competed at temperatures of up to 40 °C, the prevalence of exercise-associated hyponatremia amounted to 42% [11].…”

“…A very recent study showed that athletes would benefit from heat acclimation. Exposure to at least 2 h of exercise-heat stress on at least two occasions in the days may help preventing exertional heat illnesses and optimising performance outcomes in ultra-endurance runners in multi-stage ultra-marathon competition in the heat [11].…”