Nutrition Considerations for Open-Water Swimming
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International Journal of Sport Nutrition and Exercise Metabolism, 2014, 24, 373 -381 http://dx.doi.org/10.1123/ijsnem.2014-0018 © 2014 Human Kinetics, Inc. www.IJSNEM-Journal.com CONSENSUS STATEMENT Nutrition Considerations for Open-Water Swimming Gregory Shaw, Anu Koivisto, David Gerrard, and Louise M. Burke Open-water swimming (OWS) is a rapidly developing discipline. Events of 5–25 km are featured at FINA World Championships, and the international circuit includes races of 5–88 km. The Olympic OWS event, introduced in 2008, is contested over 10 km. Differing venues present changing environmental conditions, including water and ambient temperatures, humidity, solar radiation, and unpredictable tides. Furthermore, the duration of most OWS events (1–6 hr) creates unique physiological challenges to thermoregulation, hydration status, and muscle fuel stores. Current nutrition recommendations for open-water training and competition are either an extension of recommendations from pool swimming or are extrapolated from other athletic populations with similar physiological requirements. Competition nutrition should focus on optimizing prerace hydration and glycogen stores. Although swimmers should rely on self-supplied fuel and fluid sources for shorter events, for races of 10 km or greater, fluid and fuel replacement can occur from feeding pontoons when tactically appropriate. Over the longer races, feeding pontoons should be used to achieve desirable targets of up to 90 g/ hr of carbohydrates from multitransportable sources. Exposure to variable water and ambient temperatures will play a significant role in determining race nutrition strategies. For example, in extreme environments, thermo- regulation may be assisted by manipulating the temperature of the ingested fluids. Swimmers are encouraged to work with nutrition experts to develop effective and efficient strategies that enhance performance through appropriate in-competition nutrition. Keywords: carbohydrate intake, race practices, hydration, open-water swimming Interest in OWS has increased since the introduction Changing environmental factors, including variable water of the first events to the 1991 FINA World Aquatic Cham- and ambient temperatures, humidity, solar radiation, pionships program in Perth, Australia (25-km marathon), and unpredictable tidal influences, are unique to OWS. and the 2008 Beijing Olympic Games (10 km). The most Furthermore, the duration of some events involves physi- recent 2013 FINA World Aquatic Championships in Bar- ological issues not typically seen in other events within celona featured a multievent schedule (5, 10, and 25 km), aquatic sports: thermoregulatory challenges, significant including a mixed 5-km team race. Additional opportuni- fluid losses, and muscle fuel depletion during a single ties for international competition include the FINA 10-km competition. Emerging scientific evidence around these World cup series and Grand prix circuit (seven races of challenges informs the FINA rules for athlete safety but 15–88 km), each offering an annual program with prize has also led to the introduction of feeding pontoons, now money available (US $2,500–$3,100 for first place in integral to the layout of all standard open-water courses, FINA events). Therefore, OWS has evolved from a fringe that facilitate fluid and carbohydrate intake during the discipline to a sport with considerable international rec- race. The aim of this review is to describe the nutritional ognition and potential financial rewards. There is now an demands of OWS, with specific focus on the competition established subset of “specialist” open-water swimmers, requirements unique to this aquatic discipline. although some overlap occurs between those who may also compete in the 800-m/1500-m pool events. Because OWS venues include lakes, rivers, inland Training Requirements waterways and the open sea, with standard events rang- Open-water swimmers complete the majority of their ing from 5 to 25 km, OWS represents the most diverse training in a controlled pool environment supplemented and physiologically challenging of all FINA disciplines. with the occasional open-water session. Training volumes are consistently at the higher end of the range typically completed by pool swimmers and is combined with Shaw and Burke are with Sports Nutrition, Australian Institute camps that focus on training in an open-water environ- of Sport, Canberra, Australia. Koivisto is with The Norwegian ment to acclimatize swimmers to race conditions. Elite Olympic Sports Center (Olympiatoppen), Oslo, Norway. Ger- open-water swimmers have been reported to complete rard is with the Department of Medicine, University of Otago, weekly training distances of ~6 km (VanHeest et al., Dunedin, New Zealand. Address author correspondence to Greg 2004), compared with the average distances of 40–70 Shaw at [email protected]. km per week undertaken by pool swimmers. Although 373 374 Shaw et al. this volume of training represents a considerable energy Similar training volumes are also likely to consis- and fuel cost, it is interesting to note that “distance” tently challenge muscle glycogen stores, highlighting swimmers in pool events (e.g., 1500 m) may exceed the need for nutrition strategies focused on glycogen 70 km per week (or 45 times the length of their race), replacement for prolonged or higher-intensity sessions, whereas open-water swimmers, particularly swimmers particularly during high-volume phases. The failure to who specialize in races longer than 25 km, clearly train sufficiently replenish glycogen stores between training at a much lower volume in proportion to the demands of sessions may impair the open-water swimmer’s ability their event. Training for open-water swimmers focuses on to complete the high intensities and volumes of training high-intensity, aerobic-dependent speeds; indeed, at one required for sustained success (see review by Shaw et training camp undertaken by elite competitors, more than al., 2014). Open-water swimmers are therefore encour- 85% of training was undertaken at these intensities, with aged to aim for carbohydrate intakes at the higher end less than 2% devoted to anaerobic training or training at of sports nutrition guidelines (~6–10 g/kg body mass, or speeds “near max” (VanHeest et al., 2004). This distribu- BM, per day), especially during heavy training weeks, tion of work suggests that the nutrition requirements for and use specific strategies for glycogen replacement training of open-water swimmers are consistent with the between key training sessions as described in the review recommendations for distance swimmers in pool events by Burke et al. (2014) during their highest volume training. Further discussion Carbohydrate intake during a workout can contribute on elements of training nutrition is provided in a separate to total daily carbohydrate needs, provide additional fuel review by the current authors (Shaw et al., 2014). to support performance in a particular session (see Shaw et al., 2014), and allow practice of the feeding tactics that will be used in races. Special mention should also Body Composition and be made of supporting immune function in swimmers Physiological Characteristics who are undertaking large training volumes. Immune system responses are impaired when exposed to the Anthropometric data collected on open-water swimmers stress hormone environment associated with high inten- have shown them to be shorter and lighter, with a lower sity/high volume training, particularly when sessions percentage of lean muscle mass than pool swimmers are completed with low carbohydrate availability (Pyne (Carter & Ackland, 1994; VanHeest et al., 2004; Zam- et al., 2014). To reduce the risk of illness, open-water paro et al., 2005). This may be because less absolute swimmers are encouraged to enhance carbohydrate power is required to successfully complete open-water availability by starting training sessions with adequate events compared with sprint events (50 and 100 m) or, glycogen stores and consuming carbohydrate-containing traditionally, less competent swimmers have competed food or fluid during high intensity training to attenuate the in such events. However with the increased participation impairments in immune function seen after high intensity of longer-distance pool swimmers in open-water events, training. Training with low carbohydrate availability given enhanced competition, commercial opportunity, may be undertaken but should be by design rather than and the possibility of Olympic success, a morphological by accident and should follow a careful consideration optimization has been observed with the body shape and of a cost-benefit analysis and appropriate periodization physique of these two groups appearing to be similar. (Mujika et al., 2014). These observations are purely anecdotal, however, and Because of the extended nature of OWS, prolonged closer scientific scrutiny is warranted. Maximal oxygen workouts are often undertaken in hot conditions where uptake of open-water swimmers (80 and 66 ml/min/kg hydration requirements need to be considered. The for male and female swimmers, respectively) have been thermoregulatory impact of swimming in varying water reported to be higher (VanHeest et al., 2004) than those temperatures is discussed elsewhere (Stellingwerff et al., seen in swimmers of shorter distances (Capelli et al., 2014). Although reported values for non–urine-related 1998) but similar to other land-based endurance athletes. water loss