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, thermoregulation 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 during swimming and daily water turnover in swimmers are not as high as for terrestrial activities, losses of ~0.5 L/hr can be expected (Cox et al., 2002a; Energy and Nutrient Leiper et al., 2004; Lemon et al., 1989). These losses Recommendations for Training increase with training intensity and water temperature (Cade et al., 1991, 2002a). Therefore, open-water swim- Because the training undertaken by open-water swimmers mers should consider proactive fluid replacement during entails consistently large volumes of work completed prolonged sessions. It is more difficult to undertake field mostly at high aerobic intensities (<75% of training; assessments of sweat rates/losses on the basis of body VanHeest et al., 2004), the energy demands of training mass changes in aquatic athletes, as is commonly done are substantial. High energy requirements (23 MJ/day) during land-based sports (Cox et al., 2002a). Indeed, have been demonstrated in female swimmers undertaking errors in fluid balance calculations occur because of the large training volumes (17.5 km/day; Trappe et al., 1997). failure to account for water swallowed from the pool, Extrapolating energy expenditure data to male swimmers water collected in clothes and swimsuits, and urine undertaking similar training would suggest similar energy losses. Nevertheless, swimmers are encouraged to hydrate requirements (~4–29 MJ/day; Costill et al., 1988a). Nutrition for Open-Water Swimming 375

appropriately, minimizing significant losses and avoiding ance events longer than 2 hr (Hawley et al., 1997). As the overdrinking during sweat-incurring workouts, especially duration of an event increases (25 km and greater), the when this provides an opportunity to practice race-day benefits of carbohydrate loading may be less evident, or tactics. Fluids may also contain a source of carbohydrate at least need to be extended with a supply of exogenous toward fueling goals. Swimmers may also need to track carbohydrate sources during the race. daily hydration status to adjust fluid intake between The prerace meal offers a final opportunity for sessions. Strategies for rehydration after exercise are swimmers to start the event with optimal carbohydrate discussed in more detail by Burke et al. (2014). availability. General recommendations for a prerace meal involve the consumption of well-tolerated foods providing a carbohydrate target of 1–4 g/kg BM 1–4 hr Competition Nutrition before race start (Burke et al., 2011) and sufficient fluid During the competition phase, nutrition needs for open- to ensure that euhydration is achieved. Because of the water swimmers deviate significantly from those of pool early start time (before noon) of the majority of open- swimmers. The specific considerations for each event will water events, the prerace meal is most likely to be in be determined by race duration, environmental condi- breakfast form. Because the race location may be distant tions, and the opportunity to consume nutrients during the from competition accommodation and require travel, race. A well-planned and well-practiced nutrition strategy the last opportunity for a formal meal may be up to 4 hr of intake before, during, and after open-water events will before race time. In such scenarios, the swimmer should ensure that open-water swimmers can perform optimally continue to consume carbohydrate-containing fluids or and compete in events across a multiday program such foods (whole foods or formulated sport foods) as snack as the World Championships. Table 1 summarizes key options until race marshalling begins. considerations for the main types of races. Precooling With Cold Beverages Prerace Nutrition and Ice Slurries Open-water events longer than 5 km may be considered Swimmers competing in hot environmental conditions glycogen depleting. Costill and colleagues (1988b) (water temperatures >30 °C) may benefit from strategies reported that as little as 5,500 m of high-intensity swim- that can support thermoregulation throughout the race ming significantly depletes muscle glycogen of type I and (Ross et al., 2013). One intervention that has been sug- II muscle fibers (Costill et al., 1988b), which functionally gested to support thermal stress has been the ingestion of reduces distance per stroke (Costill et al., 1988a) and cold beverages (<4 °C) and/or ice slurries before exercise. therefore stroke efficiency. Because stroke efficiency is a The ingestion of substantial volumes (6.5–7.5 g/kg BM) key determinant of energy expenditure in OWS (Zamparo of ice slurries in the 30 min before exercise has been et al., 2005), the protection of endogenous carbohydrate shown to improve endurance capacity and performance stores is important to performance. The combination of during terrestrial exercise (Ihsan et al., 2010; Siegel et high rates of carbohydrate use and limited opportunities al., 2010, 2011; Burdon et al., 2013). An investigation to consume exogenous carbohydrate sources through- undertaken in a group of elite open-water swimmers out shorter races (5–10 km) means that swimmers are demonstrated that ingestion of cold water significantly encouraged to optimize muscle glycogen stores before reduced core temperature and thermal sensation, particu- the commencement of competition. larly during an evening training session, in a warm pool Carbohydrate loading refers to the strategy of (29 °C; Hue et al., 2013). The physiological mechanisms manipulating carbohydrate intake and exercise taper to of such strategies are explained elsewhere (Stellingwerff produce a supercompensation of muscle glycogen stores, et al., 2014). Such strategies may be considered for open- thereby enhancing endurance capacity and performance water events in which water temperatures are expected to of events longer than 90 min (Hawley et al., 1997). Tra- exceed 30 °C and last longer than 2 hr. However, more ditional carbohydrate loading regimens involve lengthy scientific evidence is needed in aquatic environments, (7 days) preparations, combining a phase of carbohydrate and swimmers are encouraged to test the use of any cold depletion before high-carbohydrate refueling (Ahlborg and or ice beverage intervention before using them in a et al., 1967). More contemporary research suggests car- race situation. bohydrate intakes of 10–12 g/kg BM/day for the 36–48 hr before exercise combined with normal training is sufficient to achieve a supercompensation in muscle gly- Energy Provision During Racing cogen stores (Bussau et al., 2002). Female swimmers are encouraged to increase their energy intake in conjunction Carbohydrate for Open-Water with carbohydrate intakes to ensure that suitable “load- Performance ing” occurs (Tarnopolsky et al., 2001). Such strategies Analysis of the performance progression of the 10-km help to offset fatigue through the maintenance of a high marathon swim event over the past 4 years has identified average pace, particularly in the closing stages of endur- that swimmers reach speeds of up to 1.75 m/s or close to Table 1 Nutrition Focus for Open-Water Swimming Events Physiological Event Duration Challenges Nutritional Focus Feeding Strategy 5 km ~0 min–1 hr Thermoregulation Optimal glycogen storage Minimal Optimize hydration status prerace in hot conditions Precooling strategies with hot conditions Caffeine Supplementation to enhance buffering capacity 5 km teams ~0 min–1 hr Thermoregulation Optimal glycogen storage Minimal Optimize hydration status prerace in hot conditions Precooling strategies with hot conditions Caffeine Supplementation to enhance buffering capacity 10 km ~1 hr 40 min Thermoregulation Optimal glycogen storage Pontoon and on body –2 hr 10 min Glycogen depletion Optimize hydration status prerace in hot conditions; precooling strategies with hot conditions Feed opportunities Maximize carbohydrate oxidation rates Caffeine Supplementation to enhance buffering capacity 25 km ~4–5 hr Thermoregulation Optimal glycogen storage Pontoon mainly Glycogen depletion Optimize hydration status prerace in hot conditions; precooling strategies with hot conditions Feed opportunities Maximize carbohydrate oxidation GI issues Warm food and fluids may be beneficial for cold conditions Caffeine Sodium considerations for hot environments > 25 km > 5 hr Thermoregulation Optimal glycogen storage Pontoon, support boats Glycogen depletion Optimize hydration status prerace in hot (available every 2.5 conditions; precooling strategies with hot km) conditions Feed opportunities Maximize carbohydrate oxidation GI issues Caffeine Warm food and fluids may be beneficial for cold conditions Moderate food and fluid composition for GI comfort Sodium considerations for hot environments Multiple events 1–3 days Glycogen Aggressive nutrition recovery between in single meet replacement races High carbohydrate intake (8–10 g/kg BM/day) Moderate protein intake Rehydration with fluid and sodium containing meals. Note. GI = gastrointestinal. BM = body mass.

376 Nutrition for Open-Water Swimming 377 their maximal efforts after long periods of submaximal (e.g., fructose transported via GLUT5) can increase the work (Vogt et al., 2013). Training strategies that adapt rate of exogenous carbohydrate available to working the muscle to maximize the contribution of fat to energy muscle for oxidation and enhancing endurance perfor- production during such swimming are encouraged (see mance (Currell & Jeukendrup, 2008). This has led to Mujika et al., 2014). Nevertheless, in longer races, the introduction of specialized sports foods containing muscle carbohydrate stores may become limiting, and an “multitransportable carbohydrates” to the market. Swim- exogenous supply of this fuel source is needed to sustain mers looking to use such products should be aware that swimming speed. Carbohydrate consumed before and fructose and similar sugars are known to cause significant during may support muscle fuel needs for longer races; gastrointestinal (GI) discomfort in certain individuals in addition, it may enhance performance via its effect (Gibson & Shepherd, 2010). Swimmers should also be on brain function even in events that are not glycogen aware that increasing the carbohydrate composition of depleting. their training diet (both overall and within training) may increase their ability to optimally absorb and oxidize Carbohydrate For Events Lasting Less these additional carbohydrate sources (Cox et al., 2010). Than 1 hr Therefore, swimmers are encouraged to practice consuming carbohydrates at high rates (up to 90 g/hr) in training Races lasting less than 1 hr may still benefit from car- before competition to minimize GI discomfort. bohydrate ingestion during competition, even when glycogen levels are optimized before race start. Events of this duration are not limited by the depletion of muscle Practicality of Feeding glycogen, and there may be little muscle oxidation of During Open-Water Races carbohydrate consumed during such a race (McConell et al., 2000). Nevertheless, there is consistent evidence that Currently, both shorter (5-km, 10-km) and longer (25- the performance of sustained high-intensity exercise of km) open-water events at the World Championships 45–75 min is enhanced when carbohydrates are ingested are completed on a loop course. Floating or stationary during exercise of this nature, with the benefits isolated feeding stations are situated at regular intervals on the to situations in which it is consumed orally at frequent course; for example, during FINA Open-Water Swim- intervals and absent when it is delivered by intravenous ming Grand Prix events, stations are placed at least every means (Carter et al., 2004a, 2004b). Several studies that 2.5 km along the course (FINA Open Water Grand Prix have used a protocol of rinsing the mouth with a carbo- Rule 4.5). Accredited handlers are positioned at these hydrate solution have demonstrated that the performance stations passing food and fluids to swimmers on long benefit is achieved via the frequent exposure of the oral poles with a cup or delivery vessel attached to one end. cavity to small amounts of carbohydrate (Jeukendrup Unlike events such as the marathon and an Olympic dis- & Chambers, 2010). The suggested mechanism for this tance triathlon, where feeding can occur while athletes phenomena is the presence of carbohydrate-sensing maintain a relatively normal velocity, open-water swim- receptors in the mouth that provide positive feedback to mers must stop or substantially reduce velocity to feed the reward centers of the brain (Chambers et al., 2009). or drink. On entering the feed area, swimmers use one of It should be noted, however, that the studies that show two techniques to consume their foods or drinks: They this effect have all involved terrestrial exercise, and evi- either come to a complete stop, find their handler, and dence is lacking in aquatic sports, particularly in real-life feed, or they maintain a constant speed while rolling onto performance settings. their backs, feeding, then rolling back over and continu- ing to swim. These techniques are time consuming and Carbohydrate Intake for Glycogen- could potentially affect swimming rhythm, particularly in shorter duration races. Feeding strategies that require Depleting Events minimal interruption to swimming speed may provide Muscle glycogen stores are influenced by gender, training a tactical advantage to swimmers especially when the status, and dietary intake and typically become depleted feed zones are positioned at significant distances off the during sporting events of lasting longer than 90 min race line. As race durations increase (>2 hr), swimmers (Hawley et al., 1997). This outcome could be expected and coaches are encouraged to use feeding pontoons to occur during races of 10 km or longer, challenging a frequently to meet high carbohydrate and fluid demands. swimmer’s ability to maintain high swimming velocities. Additional carbohydrate sources should be supplied via the ingestion of carbohydrate-rich foods and fluids during Event-Specific Strategies the race as is commonly practiced in many land-based 5 km and 5 km Teams endurance sports (Burke et al., 2011). Jentjens and colleagues (2004) demonstrated that the intestinal absorp- Because of the duration and nature of 5-km individual tion of glucose via the SGLT1 transporters is limited. and team races, the requirement for nutrition support However, combining glucose with carbohydrates that are during racing is minimal. Although feeding opportuni- absorbed through different gastrointestinal transporters ties in the majority of OWS races governed by FINA 378 Shaw et al. are ample (~every 1.25 km), swimmers may not benefit of glucose and fructose); such tactics have been shown to from using these stations in races such as the individual improve ultraendurance exercise protocols (for review, and team 5-km event for a variety of reasons. First, the see Jeukendrup (2011). It is generally recommended positioning of the pontoons requires swimmers to devi- that feeding commence early in the race to allow high ate from the line of least distance between buoys, adding targets for carbohydrate intake to be met, as well as to unnecessary time and effort to complete the race. Second, take advantage of the central nervous system benefits of well-practiced open-water swimmers regularly use tactics oral carbohydrate sensing (Jeukendrup, 2011). However, such as drafting (i.e., streamlining behind another com- more research is required to identify optimal amounts petitor) to reduce the energy cost of swimming (Chatard and patterns of intake of carbohydrate for OWS proto- & Wilson, 2003), hence sparing valuable glycogen and cols. Until such time, swimmers should experiment to reducing the need for endogenous sources. Indeed, swim- determine whether higher rates of carbohydrate intake ming between 0 and 50 cm behind the feet of a fellow from multitransportable carbohydrate are possible and competitor can reduce the oxygen cost of swimming by beneficial. approximately 12% (Chatard & Wilson, 2003). Third it High rates of fluid loss have been reported (1.2–1.6 is unlikely that the consumption of exogenous nutrients, L/hr) in high intensity swimming (Cade et al., 1991). despite their perceived central benefits via mouth sensing, Macaluso and colleagues (2011) reported increasing would offset the time penalties and other disadvantages levels of hypohydration and core temperature when of pontoon feeding (Colombani et al., 2013). Although swimmers completed a 5-km time trial in three differ- the intake of carbohydrates for central benefit may be ent water temperatures (23, 27, and 28 °C). Although achieved through the use of sports gels, the time taken to moderate levels (2%) of dehydration were reported when consume the gel would offset the benefits of feeding in swimmers completed the time trial in 32 °C water, rises races of such durations. Therefore, swimmers competing in core temperature were mild (36.9 ± 0.4 to 38.0 ± 0.4 in these events are encouraged to focus on prerace nutri- °C; Macaluso et al., 2011). Similar levels of weight loss tion strategies to optimize carbohydrate availability and have been seen in swimmers completing 2 hr of flume hydration status using feed stations and on body nutrition swimming at similar water temperatures (personal obser- support only when tactically advantageous. vations, David Gerrard, Otago University). As greater levels of dehydration would be expected in 10-km events, 10 km swimmers may benefit from starting a race with an optimized hydration status. Recent studies have shown that Swimmers competing in 10-km races should optimize prerace intake of a sodium-containing beverage (10 ml/ prerace glycogen and hydration status. Because the kg BM, or ~64 mmol/L Na+) can reduce thermal strain duration and intensity of a 10-km open-water event and enhance endurance capacity in terrestrial exercise corresponds with the theoretical limits of glycogen stor- activities (Sims et al., 2007a, 2007b). Swimmers may age, swimmers are encouraged to identify opportunities find advantages in combining the use of sodium and cold throughout a race where nutrient ingestion is possible. beverages to optimize prerace hydration status and enable Feeding pontoons are available at regular opportunities a reduction in core temperature before competition. throughout the race, as for the 5-km event. In recent years, however, we have observed that swimmers have tended 25 km and Longer Events to rely less on the feeding pontoons for nutritional support, carrying their own gels and small flasks tucked into Pre-race interventions used to enhance performance in their swimsuits. This arrangement allows the swimmer shorter duration events may continue to be advantageous to feed at opportunities that are tactically advantageous, in preparation for longer duration events. The duration of while maximizing their opportunities to use the energy- the 25-km event is 5 hr or more, so swimmers are encour- saving advantages of drafting behind the feet of another aged to increase their reliance on central feeding zones competitor. General guidelines for endurance exercise of and pontoons to access nutritional support. Carbohydrate 2-hr duration suggest carbohydrate intakes of 30–60 g/hr intakes should be targeted to ~90 g/hr from multiple (Burke et al., 2011). However, the unique environmental transportable carbohydrate sources (Jeukendrup, 2011), and physiological influences of OWS events may require and with the greater likelihood of extreme temperature high exogenous oxidation rates to optimize performance. variations in these events (16–31 °C), swimmers may It has been suggested that arm muscle, compared with benefit from matching beverage temperatures to specific leg muscle, has lower glycogen stores but uses carbohy- environmental conditions. Cold beverages (4 °C) may drate at a higher rate (Ahlborg & Jensen-Urstad, 1991; enhance endurance exercise performance by reducing Tremblay et al., 2009). This assertion may explain the thermal strain (Ross et al., 2013). Conversely, warm significant glycogen depletion seen in the deltoid muscle beverages or food sources, such as warmed sports drinks of swimmers completing relatively short distances (5.5 or soup, are used by open-water swimmers in cold-water km; Costill et al., 1988b). High utilization rates of exog- events, but there is currently no research suggesting that enous carbohydrate sources by the leg can be achieved these practices can attenuate core temperature reductions by consuming 60–90 g/hr of carbohydrates from sources seen in these events. In these events, just as in other using different intestinal transporters (e.g., combinations ultraendurance events, there have been observations of Nutrition for Open-Water Swimming 379 fluid mismatches in which intake greatly exceeds sweat races (for review of refueling strategies, see Burke et al., rates. Indeed, 17% of competitors (8% of men and 36% 2014). Carbohydrate sources should focus on low-fiber, of women) competing in a 26.4-km marathon swim in high-glycemic-index foods and fluids to minimize GI Lake Zurich were reported to have exercise-associated discomfort and enable the large amounts of carbohy- hyponatremia (Wagner et al., 2012). Appropriate hydra- drates required for glycogen replacement. Swimmers tion plans in hot environmental conditions may require may benefit from consuming small (~20 g) well-planned attention to drink sufficient fluid; however, in cooler (3–4 per day) servings of high biological value protein environmental conditions, swimmers may need to find sources with carbohydrate to optimize muscle tissue more concentrated sources of carbohydrate (e.g., gels recovery (Areta et al., 2013) but also support glycogen and confectionery items) so that fuel-intake targets can replacement (Betts & Williams, 2010). be met without overhydration. Such race plans need to be well practiced in training but include sufficient flexibility so that they can be adapted to unexpected conditions on Conclusion race day. Because of the emerging nature of OWS, very little research is available to inform nutrition practices. Current Ergogenic Aids nutrition recommendations for open-water training and Ergogenic aids that may enhance swimming performance competition are either an extension of pool recommenda- have been reviewed elsewhere by Derave and Tipton tions or are extrapolated from other athletic populations (2014). Of specific interest to open-water swimmers are with similar physiological requirements. Competition products that can enhance central drive and help buffer nutrition should focus on optimizing prerace hydration acidic environments; this is especially important in the and glycogen stores. Throughout the race, swimmers last few kilometers of any championship race. Current should rely on self-supplied fuel and fluid sources, using tactics in the completion of 5- and 10-km races involve an feeding zones only when tactically appropriate for races incremental increase in speed throughout the event, such of 10 km or less. As race durations extend toward and that the final kilometers are completed at near maximal beyond 5 hr, feeding zones become more significant to intensities. Caffeine has been shown to be beneficial to reduce stresses associated with prolonged environmen- swimmers competing in longer duration pool events (i.e., tal exposure. These strategies therefore assume a more 1,500 m; MacIntosh & Wright, 1995) with moderate significant role in race nutrition. The manipulation of the doses (~mg/kg) able to improve performance in other temperature of ingested fluids may assist with thermo- sporting events lasting longer than 90 min (Cox et al., regulation during long events in extreme environments. 2002b). Caffeine supplementation protocols include Swimmers are encouraged to work with trained profes- intakes of up to 3 mg/kg in the hour before short open- sionals to develop effective and efficient race nutrition water events or smaller doses consumed in conjunction strategies that enhance competition performance. with carbohydrate throughout longer duration races. Supplementation with b-alanine, the rate-limiting compo- References nent in the formation of the muscle dipeptide carnosine, has been shown to enhance peak power and mean power Ahlborg, B., Bergstrom, J., Brohult, J., Ekelund, L., Hultman, during the final sprint in a simulated cycling road race E., & Maschio, G. (1967). Human muscle glycogen content (Van Thienen et al., 2009), a protocol similar to sustained and capacity for prolonged exercise after different diets. near-maximal efforts seen at the end of open-water races. Forsvarsmedicin, 3, 85–89. Specific studies should investigate whether enhanced Ahlborg, G., & Jensen-Urstad, M. (1991). Metabolism in exer- intracellular buffering capacity results in enhanced open- cising arm vs. leg muscle. Clinical Physiology, 11, 459– water race performance; currently there is a distinct lack 468. PubMed doi:10.1111/j.1475-097X.1991.tb00818.x of such research in the literature. Areta, J.L., Burke, L.M., Ross, M.L., Camera, D.M., West, D.W., Broad, E.M., . . . Coffey, V.G. (2013). Timing and Multiple-Event Programs distribution of protein ingestion during prolonged recovery from resistance exercise alters myofibrillar protein synthe- Swimmers competing in multiple events at a FINA World sis. The Journal of Physiology, 591, 2319–2331. PubMed Championship have considerable nutritional challenges. Betts, J.A., & Williams, C. (2010). Short-term recovery from Short turnaround (1–2 days) between glycogen-depleting prolonged exercise: exploring the potential for protein events can place significant strain on swimmers aiming ingestion to accentuate the benefits of carbohydrate to start each race with optimal fuel stores. Outstanding supplements. Sports Medicine, 40, 941–959. PubMed swimmers may compete in 5-km (individual and team), doi:10.2165/11536900-000000000-00000 10-km, and potentially 25-km events, all within the space Burdon, C.A., Hoon, M.W., Johnson, N.A., Chapman, P.G., of 5 days. Aggressive attention to the amount (>10 g/ & O’Connor, H.T. (2013). The effect of ice slushy inges- kg BM) and timing (starting soon after each race) of tion and mouthwash on thermoregulation and endurance carbohydrate intakes between races is required to ensure performance in the heat. International Journal of Sport that adequate glycogen replacement is achieved between Nutrition and Exercise Metabolism, 23, 458–469. 380 Shaw et al.

Burke, L.M., & Mujika, I. (2014). Nutrition for recovery in level water polo players and swimmers. Journal of Science aquatic sports. International Journal of Sport Nutrition and Medicine in Sport, 5, 183–193. PubMed doi:10.1016/ and Exercise Metabolism, 24, 425-436. S1440-2440(02)80003-2 Burke, L.M., Hawley, J.A., Wong, S.H., & Jeukendrup, A.E. Cox, G.R., Desbrow, B., Montgomery, P.G., Anderson, M.E., (2011). Carbohydrates for training and competition. Jour- Bruce, C.R., Macrides, T.A., . . . Burke, L.M. (2002b). nal of Sports Sciences, 29(Suppl. 1), S17–S27. PubMed Effect of different protocols of caffeine intake on metabo- doi:10.1080/02640414.2011.585473 lism and endurance performance. Journal of Applied Bussau, V.A., Fairchild, T.J., Rao, A., Steele, P., & Fournier, Physiology, 93, 990–999. PubMed P.A. (2002). Carbohydrate loading in human muscle: an Cox, G.R., Clark, S.A., Cox, A.J., Halson, S.L., Hargreaves, M., improved 1 day protocol. European Journal of Applied Hawley, J.A., . . . Burke, L.M. (2010). Daily training with Physiology, 87, 290–295. PubMed doi:10.1007/s00421- high carbohydrate availability increases exogenous carbo- 002-0621-5 hydrate oxidation during endurance cycling. Journal of Cade, J.R., Reese, R.H., Privette, R.M., Hommen, N.M., Applied Physiology, 109, 126–134. PubMed doi:10.1152/ Rogers, J.L., & Fregly, M.J. (1991). Dietary intervention japplphysiol.00950.2009 and training in swimmers. European Journal of Applied Currell, K., & Jeukendrup, A.E. (2008). Superior endurance Physiology and Occupational Physiology, 63, 210–215. performance with ingestion of multiple transportable car- PubMed doi:10.1007/BF00233850 bohydrates. Medicine & Science in Sports & Exercise, 40, Capelli, C., Pendergast, D.R., & Termin, B. (1998). Energetics 275–281. PubMed doi:10.1249/mss.0b013e31815adf19 of swimming at maximal speeds in humans. European Derave, W., & Tipton, K.D. (2014). Dietary supplements for Journal of Applied Physiology and Occupational Physiol- aquatic sports. International Journal of Sport Nutrition ogy, 78, 385–393. PubMed doi:10.1007/s004210050435 and Exercise Metabolism, 24, 437–449. Carter, J.E.L., & Ackland, T.R. (Eds.). (1994). Kinanthropom- Gibson, P.R., & Shepherd, S.J. (2010). Evidence-based dietary etry in aquatic sports: A study of world class athletes. management of functional gastrointestinal symptoms: The Champaign, IL: Human Kinetics. FODMAP approach. Journal of Gastroenterology and Carter, J.M., Jeukendrup, A.E., & Jones, D.A. (2004a). The Hepatology, 25, 252–258. PubMed doi:10.1111/j.1440- effect of carbohydrate mouth rinse on 1-h cycle time 1746.2009.06149.x trial performance. Medicine & Science in Sports & Hawley, J.A., Schabort, E.J., Noakes, T.D., & Dennis, S.C. Exercise, 36, 2107–2111. PubMed doi:10.1249/01. (1997). Carbohydrate-loading and exercise perfor- MSS.0000147585.65709.6F mance. An update. Sports Medicine, 24, 73–81. PubMed Carter, J.M., Jeukendrup, A.E., Mann, C.H., & Jones, D.A. doi:10.2165/00007256-199724020-00001 (2004b). The effect of glucose infusion on glucose kinet- Hue, O., Monjo, R., Lazzaro, M., Baillot, M., Hellard, P., ics during a 1-h time trial. Medicine & Science in Sports Marlin, L., & Jean-Etienne, A. (2013). The effect of time & Exercise, 36, 1543–1550. PubMed doi:10.1249/01. of day on cold water ingestion by high-level swimmers in MSS.0000139892.69410.D8 a tropical climate. International Journal of Sports Physiol- Chambers, E.S., Bridge, M.W., & Jones, D.A. (2009). Carbohy- ogy and Performance, 8, 442–451. PubMed drate sensing in the human mouth: effects on exercise per- Ihsan, M., Landers, G., Brearley, M., & Peeling, P. (2010). formance and brain activity. Journal of Physiology, 587, Beneficial effects of ice ingestion as a precooling strat- 1779–1794. PubMed doi:10.1113/jphysiol.2008.164285 egy on 40-km cycling time-trial performance. Interna- Chatard, J.C., & Wilson, B. (2003). Drafting distance tional Journal of Sports Physiology and Performance, 5, in swimming. Medicine & Science in Sports & 140–151. PubMed Exercise, 35, 1176–1181. PubMed doi:10.1249/01. Jentjens, R.L., Moseley, L., Waring, R.H., Harding, L.K., & MSS.0000074564.06106.1F Jeukendrup, A.E. (2004). Oxidation of combined inges- Colombani, P.C., Mannhart, C., & Mettler, S. (2013). Carbohy- tion of glucose and fructose during exercise. Journal of drates and exercise performance in non-fasted athletes: A Applied Physiology, 96, 1277–1284. PubMed doi:10.1152/ systematic review of studies mimicking real-life. Nutrition japplphysiol.00974.2003 Journal, 12, 16. PubMed doi:10.1186/1475-2891-12-16 Jeukendrup, A.E., & Chambers, E.S. (2010). Oral carbohydrate Costill, D.L., Flynn, M.G., Kirwan, J.P., Houmard, J.A., Mitch- sensing and exercise performance. Current Opinion in ell, J.B., Thomas, R., & Park, S.H. (1988a). Effects of Clinical Nutrition and Metabolic Care, 13, 447–451. repeated days of intensified training on muscle glycogen PubMed doi:10.1097/MCO.0b013e328339de83 and swimming performance. Medicine & Science in Sports Jeukendrup, A.E. (2011). Nutrition for endurance sports: & Exercise, 20, 249–254. PubMed doi:10.1249/00005768- marathon, triathlon, and road cycling. Journal of Sports 198806000-00006 Sciences, 29(Suppl. 1), S91–S99. PubMed doi:10.1080/0 Costill, D.L., Hinrichs, D., Fink, W.J., & Hoopes, D. (1988b). 2640414.2011.610348 Muscle glycogen depletion during swimming interval Leiper, J.B., & Maughan, R.J. (2004). Comparison of water turn- training. Journal of Swimming Research, 4, 15–18. over rates in young swimmers in training and age-matched Cox, G.R., Broad, E.M., Riley, M.D., & Burke, L.M. (2002a). non-training individuals. International Journal of Sport Body mass changes and voluntary fluid intakes of elite Nutrition and Exercise Metabolism, 14, 347–357. PubMed Nutrition for Open-Water Swimming 381

Lemon, P.W., Deutsch, D.T., & Payne, W.R. (1989). Sims, S.T., van Vliet, L., Cotter, J.D., & Rehrer, N.J. (2007b). Urea production during prolonged swimming. Sodium loading aids fluid balance and reduces physiologi- Journal of Sports Sciences, 7, 241–246. PubMed cal strain of trained men exercising in the heat. Medicine doi:10.1080/02640418908729844 & Science in Sports & Exercise, 39, 123–130. PubMed Macaluso, F., Di Felice, V., Boscaino, G., Bonsignore, G., doi:10.1249/01.mss.0000241639.97972.4a Stampone, T., Farina, F., & Morici, G. (2011). Effects Stellingwerff, T., Pyne, D.B., & Burke, L.M. (2014). Nutrition of three different water temperatures on dehydration in considerations in special environments for aquatic sports. competitive swimmers. Science & Sports, 26, 265–271. International Journal of Sport Nutrition and Exercise doi:10.1016/j.scispo.2010.10.004 Metabolism, 24, 470-479. MacIntosh, B.R., & Wright, B.M. (1995). Caffeine inges- Tarnopolsky, M.A., Zawada, C., Richmond, L.B., Carter, S., tion and performance of a 1,500-metre swim. Canadian Shearer, J., Graham, T., & Phillips, S.M. (2001). Gender Journal of Applied Physiology, 20, 168–177. PubMed differences in carbohydrate loading are related to energy doi:10.1139/h95-012 intake. Journal of Applied Physiology, 91, 225–230. McConell, G.K., Canny, B.J., Daddo, M.C., Nance, M.J, Snow PubMed R.J. (2000). Effect of carbohydrate ingestion on glucose Trappe, T.A., Gastaldelli, A., Jozsi, A.C., Troup, J.P., & Wolfe, kinetics and muscle metabolism during intense endurance R.R. (1997). Energy expenditure of swimmers during exercise. Journal of Applied Physiology, 89, 1690–1698. high volume training. Medicine & Science in Sports & Mujika, I., Stellingwerff, T., & Tipton, K. (2014). Nutrition Exercise, 29, 950–954. PubMed doi:10.1097/00005768- and training adaptations in aquatic sports. International 199707000-00015 Journal of Sport Nutrition and Exercise Metabolism, 24, Tremblay, J.H., Peronnet, F., Lavoie, C., & Massicotte, D. 414-424. (2009). Fuel selection during prolonged arm and leg exer- Pyne, D.B., Verhagen, E.A., & Mountjoy, M. (2014). Nutrition, cise with 13C-glucose ingestion. Medicine & Science in illness, and injury in aquatic sports. International Journal Sports & Exercise, 41, 2151–2157. PubMed doi:10.1249/ of Sport Nutrition and Exercise Metabolism, 24, 460-469. MSS.0b013e3181ab2579 Ross, M., Abbiss, C., Laursen, P., Martin, D., & Burke, L. Van Thienen, R., Van Proeyen, K., Vanden Eynde, B., Puype, (2013). Precooling methods and their effects on athletic J., Lefere, T., & Hespel, P. (2009). Beta-alanine improves performance: a systematic review and practical applica- sprint performance in endurance cycling. Medicine & tions. Sports Medicine, 43, 207–225. PubMed doi:10.1007/ Science in Sports & Exercise, 41, 898–903. PubMed s40279-012-0014-9 doi:10.1249/MSS.0b013e31818db708 Shaw, G., Boyd, K.T., Burke, L.M., & Koivisto, A. (2014). VanHeest, J.L., Mahoney, C.E., & Herr, L. (2004). Character- Nutrition for swimming. International Journal of Sport istics of elite open-water swimmers. Journal of Strength Nutrition and Exercise Metabolism, 24, 360-372. and Conditioning Research, 18, 302–305. PubMed Siegel, R., Mate, J., Brearley, M.B., Watson, G., Nosaka, K., Vogt, P., Rüst, C.A., Rosemann, T., Lepers, R. & Knechtle, B. & Laursen, P.B. (2010). Ice slurry ingestion increases (2013). Analysis of 10 km swimming performance of elite core temperature capacity and running time in the heat. male and female open-water swimmers. SpringerPlus, Medicine & Science in Sports & Exercise, 42, 717–725. 2, 603. PubMed doi:10.1249/MSS.0b013e3181bf257a Wagner, S., Knechtle, B., Knechtle, P., Rust, C.A., & Rose- Siegel, R., Mate, J., Watson, G., Nosaka, K., & Laursen, P.B. mann, T. (2012). Higher prevalence of exercise-associated (2011). The influence of ice slurry ingestion on maximal hyponatremia in female than in male open-water ultra- voluntary contraction following exercise-induced hyper- endurance swimmers: the ‘Marathon-Swim’ in Lake thermia. European Journal of Applied Physiology, 111, Zurich. European Journal of Applied Physiology, 112, 2517–2524. PubMed doi:10.1007/s00421-011-1876-5 1095–1106. PubMed doi:10.1007/s00421-011-2070-5 Sims, S.T., Rehrer, N.J., Bell, M.L., & Cotter, J.D. (2007a). Zamparo, P., Bonifazi, M., Faina, M., Milan, A., Sardella, F., Preexercise sodium loading aids fluid balance and endur- Schena, F., & Capelli, C. (2005). Energy cost of swim- ance for women exercising in the heat. Journal of Applied ming of elite long-distance swimmers. European Journal Physiology, 103, 534–541. PubMed doi:10.1152/jap- of Applied Physiology, 94, 697–704. PubMed doi:10.1007/ plphysiol.01203.2006 s00421-005-1337-0