Hydration status and water turnover of dogsled drivers during an endurance sled dog even in the Arctic

Abstract

Objectives. To determine changes in common urinary markers of hydration maintained by the drivers (mushers) during a wilderness endurance event in the arctic and to determine water turnover in this select group of individuals. Study Design. During this descriptive study, data was systematically collected on hydration, water turnover, changes in resting and exercise heart rate, fatigue and rating of perceived exertion during an arduous dogsled race in the arctic. Methods. Sixteen mushers were recruited for the study, 13 of whom completed the entire race. At five different checkpoints along the 1049-mile trail (symbolic distance), urine was collected. Urine osmolality (U osm ) was determined using freezing point depression. Urine specific gravity (U sg ) was determined using a hand-held refractometer. Water turnover was measured in 5 mushers from rates of deuterium ( 2 H 2 O) elimination (rH 2 O). Prior to the start of the race, and at five checkpoints along the trail, a resting heart rate, fatigue rating scale and a rating of perceived exertion (RPE), were collected. Results. Out of the 13 subjects that completed the event, four of the mushers had a U sg ≥ 1.030 (mean 1.023 ± 0.007) at some point during the event. Ten had a urine osmolality ≥ 900 mOsm L -1 at some point during the event, with an average U osm of 868 ± 277 mOsm L -1 over the duration of the event. Water turnover demonstrated that rH 2 O averaged 2.85 ± 1.18 ml kg -1 day -1 (range 2.03 -4.60) over the duration of the event. Resting heart rate increased significantly over the course of the race. The RPE was related to the overall fatigue rating scale.Conclusions. These data demonstrate that the majority of mushers studied showed signs of dehydration based on common urinary markers during the long-distance dogsled race. The dehydration appears to have had an influence on the resting heart rate, overall fatigue and the rating of perceived exertion during the race. (Int J Circumpolar Health 2006;65(1):45-54.)

Health challenges in long-distance dog sled racing: A systematic review of literature

“…The energy expenditure increased during the last leg of the race, likely due to fatigued dogs. Food records indicate an adequate intake of protein, but an insufficient intake of carbohydrate.Cox et al [15]5.6716 mushers (9 M and 7 F, Age: 36±11 years) participating in the Iditarod a Descriptive field study with baseline assessments and repeated measurementsPsychophysical workloadSleep & alertnessEnergy intake and hydrationRPE, Fatigue scale, resting HR and HR response to a bench step exercise testCOWASampling or urine, analysed for specific gravity, osmolality and isotopic analysisBody-weight assessment (digital scale)Resting HR (but no HR response), RPE and fatigue increased throughout the course of the race and some associations were observed between these parameters and the mushers’ hydration status. Most mushers were dehydrated at some point of the race.…”

“…The energy expenditure of the mushers especially increased during the last leg of the race, likely due to fatigued dogs and/or a reduction of the dogs pack, which put more strain on the mushers [14]. However, findings on perceived exertion show that the subjective experience of fatigue can vary among the participants, and indicate that such subjective experience of exertion/fatigue might be associated with physiological parameters such as the participants’ hydration status [15,17]. …”

“…For example, Cox et al . [15] found that, while on average their sample of mushers maintained optimal levels of hydration, most of them (77%) showed some sign of dehydration at some point during the race. Weydahl and Calogiuri [17] also observed that two female mushers assumed adequate amounts of liquids throughout the race, but one of them was in a state of dehydration from before the beginning of the race.…”

“…Cox et al . [15] and Weydahl and Calogiuri [17] also speculate that less experienced mushers are more exposed to the risks of dehydration, as they haven’t established good routines for taking on adequate amounts of liquids before and during the race.…”

“…[15] hypothesised that such a tight schedule would have a negative impact on the mushers cognitive functions, which could, in turn, lead to a reduced ability to engage in safety procedures, such as assuming adequate amounts of liquids and nutrients. In their study, they administered a cognitive test (the Controlled oral word association) to a sample of mushers at different check-points throughout the race, but failed, however, in finding evidence for such relationship [15]. On the other hand, Calogiuri and Weydahl have shown that the sleep loss accumulated during the race has long-distance effects on the participants’ alertness and sleep-wake patterns [10,11,19].…”