Original scientific article Received: 2018-04-19 ANNALES KINESIOLOGIAE • 9 • 2018 • 1 UDC: 797.21.034.6:613.2 NUTRITIONAL STRATEGIES OF SLOVENIAN NATIONAL JUNIOR SWIMMING TEAM Vesna SIMIC1, Nina MOHORKO1 'University of Primorska, Faculty of Health Sciences, Slovenia Corresponding Author: Nina MOHORKO University of Primorska, Faculty of Health Sciences, Polje 42, 6310 Izola, Slovenia. Phone: +386 5 66 35 801 e-mail: nina.mohorko@fvz.upr.si ABSTRACT Purpose: The purpose of our study was to assess the nutritional strategies of Slovenian national junior swimming team and compare them with recommendations of clinical sports nutrition. Competitive young swimmers, namely, have increased energy and nutrient needs compared to general adolescents due to frequent and intense training. Despite some physiological differences if compared with adults, adult sports nutrition recommendations for macronutrients apply to them. Further, literature reports iron, calcium, and vitamin D intake as frequently inadequate. Methods: Nutritional strategies of 19 members of Slovenian national junior swimming team were assessed retrospectively through 3-day food and activity diaries, questionnaires, anthropometric data including bioimpedance analysis. Energy availability (EA), macronutrient intake and timing, iron, calcium and vitamin D intakes, hydration, consumption of sports food and dietary supplement use were evaluated. Results: EA in some of male swimmers and in the majority offemale swimmers was lower than recommended. Carbohydrate intake was adequate in male swimmers and two thirds of female swimmers. Although average protein intake exceeded the upper recommended limit, some female swimmers did not meet the lower recommended intake limit. Total fat intake was lower than recommended, with saturated fat intake on the upper recommended level. Calcium and iron intake in male swimmers exceeded recommended values, while female swimmers had lower calcium intake than recommended and some had lower iron intake, too. Vitamin D intake was low in all swimmers. Meal timing was adequate in the majority of swimmers, who often reached for dietary supplements, mostly omega 3 fatty acids, multivitamins and magnesium. Conclusions: Low EA in young competitive swimmers is of concern. More successful, personalised nutrition strategies for young competitive swimmers, focusing on hi- 15 ANNALES KINESIOLOGIAE • 9 • 2018 • 1 Vesna SIMIC, Nina MOHORKO: NUTRITIONAL STRATEGIES OF SLOVENIAN NATIONAL JUNIOR SWIMMING TEAM, 15-34 gher energy intake and healthy food choices, would contribute to the preservation of their health and further development into top performers. Keywords: nutrition, young athletes, sport nutrition recommendation, health, performance. PREHRANSKE STRATEGIJE PLAVALCEV SLOVENSKE KADETSKE IN MLADINSKE REPREZENTANCE IZVLEČEK Namen: Namen naše raziskave je bil ugotoviti ustreznost uporabljenih prehranskih strategij plavalcev slovenske kadetske in mladinske reprezentance v primerjavi z veljavnimi priporočili klinične športne prehrane. Mladi plavalci, ki tekmujejo, imajo v primerjavi z ostalimi najstniki zaradi pogostih in intenzivnih treningov povečane energijske in prehranske potrebe. Kljub očitnim fiziološkim razlikam, ki jih ločijo od odraslih, veljajo zanje priporočila za vnos makrohranil za odrasle športnike. Med mikrohranili literatura navaja, da so vnosi železa, kalcija in vitamina D pogosto nezadostni. Metode: Prehranske strategije 19 plavalcev slovenske kadetske in mladinske reprezentance smo retrospektivno ocenili na osnovi 3-dnevnih prehranskih in aktivno-stnih dnevnikov, vprašalnika ter podatkov antropometričnih meritev, vključno z bioimpedančno analizo. Ugotavljali smo energijsko razpoložljivost (ER), vnos in časovno razporejanje makrohranil, vnose železa, kalcija in vitamina D, hidracijo, uporabo športne prehrane in prehranskih dopolnil. Rezultati: ER je bila pri nekaterih moških plavalcih in pri večini plavalk prenizka. Vnosi ogljikovih hidratov so bili primerni pri plavalcih in dveh tretjinah plavalk. Kljub temu, da je ugotovljeni povprečni vnos beljakovin presegal zgornjo priporočeno mejo, nekatere plavalke niso dosegale spodnje priporočene meje. Celokupni vnosi maščob so bili nižji od priporočenih, vnosi nasičenih maščob pa na zgornji meji. Vnos kalcija in železa je pri plavalcih presegal priporočene vrednosti, pri plavalkah pa je bil vnos kalcija in pri nekaterih tudi vnos železa pod priporočeno mejo. Ritem obrokov je bil pri večini ustrezen. Plavalci in plavalke so pogosto uživali prehranska dopolnila, najpogosteje maščobne kisline omega-3, multivitamine in magnezij. Zaključek: Nizka ER pri mladih plavalcih, ki tekmujejo, je zaskrbljujoča. Bolj uspešne individualne prehranske strategije za mlade plavalce, ki bi se osredotočale na višji energijski vnos in zdravo prehrano, bi prispevale k varovanju njihovega zdravja in razvoju v vrhunske športnike. Ključne besede: prehrana, mladi športnik, priporočila, zdravje, zmogljivost 16 ANNALES KINESIOLOGIAE • 9 • 2018 • 1 Vesna SIMIC, Nina MOHORKO: NUTRITIONAL STRATEGIES OF SLOVENIAN NATIONAL JUNIOR SWIMMING TEAM, 15-34 INTRODUCTION Young athletes who participate in high intensity sports programs have higher nutritional and energy needs than the general WHO recommendations stated for children and adolescents (Desbrow & Leveritt, 2015). Competitive young swimmers belong to a group of athletes with increased energy and nutrient needs due to frequent and intense training (Petrie, Stover, & Horswill, 2004). At the metabolic level, all three energy systems (the high energy phosphagen system, anaerobic glycolysis and aerobic metabolism) are involved in all swimming competition disciplines, ranging by duration between 20 seconds (50 m) and 14.5 minutes (1,500 m) in junior elite swimmers (Federation Internationale de Natation, 2018). Although adolescents have specific nutritional needs because they differ from adults in energy consumption, substrate consumption during exercise, thermoregulation, sweat mechanism and maintenance of fluid balance as well as other physiological components (Desbrow & Leveritt, 2015), the sports nutrition principles are similar to those for adults. For long-term health protection of athletes, adequate energy availability (EA), 45 kcal/kg of fat-free mas (FFM) or more, must be provided (Desbrow & Leveritt, 2015). Sufficient energy and nutrient intake in adolescence is critical for normal growth and development, maintaining health and injury prevention. An adequate nutrition intake also enables optimization of the training process and successful recovery. Adolescence is a crucial period, comprised of intense growth and development, involving the alteration of body composition, metabolic and hormonal fluctuations, maturation of organ systems and formation of nutrient storage, all of which has a potential impact on the individual's health in the future (Sawyer et al., 2012). Long-term suboptimal EA, in the range between 30 and 45 kcal/kg FFM, or too low EA, under 30 kcal/kg FFM, leads to relative energy deficiency in sport (RED-S) (Mountjoy et al., 2014). The latter leads to disrupted physiological functions caused by the relative lack of energy, which include lowered metabolic rate, disrupted menstrual function, and compromised bone health, immunity, protein synthesis and cardiovascular health. Despite the fact that there are potential differences in the ability to store carbohydrates (CHO) and to use substrates during physical activity between adults and children, literature reports that the CHO needs of young athletes do not differ greatly from the needs of adults (Desbrow et al., 2014). In moderate to high-intensity endurance training, which lasts from 1 to 3 hours per day, CHO intake of 6 to 10 g/kg of body weight (BW) is recommended and in moderate to high intensity exercise, which lasts 4 to 5 hours per day, 8 to 12 g CHO/kg BW/ day is recommended (Burke, Hawley, Wong, & Jeukendrup, 2011). The recommendations must be individual, dynamic and in accordance with the requirements and goals (Thomas, Erdman, & Burke, 2016). Due to the lack of specific research into the protein requirements of adolescent athletes, it is suggested to follow the recommendations for adult athletes (1.3 - 1.8 g protein/kg BW). Some athletes have increased protein requirements during adolescence compared to the recommended quantities for their age group, especially if they have well-developed muscle mass or if they participate in high intensity exercise programs 17 ANNALES KINESIOLOGIAE • 9 • 2018 • 1 Vesna SIMIC, Nina MOHORKO: NUTRITIONAL STRATEGIES OF SLOVENIAN NATIONAL JUNIOR SWIMMING TEAM, 15-34 (Boisseau, Vermorel, & Rance, 2007; Aerenhouts, Deriemaeker, Hebbelinck, & Clarys, 2011; Aerenhouts, Van Cauwenberg, Poortmans, Hauspie, & Clarys, 2013). Dietary fat intake of adolescent athletes should follow general recommendations (Desbrow et al., 2014). According to the National Institute for Public Health (2016) this means that in the 10- to 14-year old age group, fat should represent between 30 and 35% of total energy intake (EI), while in the 15- to 18-year old age group, fat intake should contribute up to 30% EI, with the note that in physically active individuals this share could be increased to up to 35% EI. Saturated fat should not exceed 10% EI (National Institute for Public Health, 2016). Micronutrient deficiencies have negative impact on health and performance because micronutrients participate in a number of functions in the body. In young athletes, special attention must be paid to iron, calcium and vitamin D intakes (Desbrow & Leveritt, 2015). Recommendations for iron intake in young athletes do not differ from recommendations for the general population, despite the fact that exercise can cause additional iron loss through sweating or bleeding into the gastrointestinal system or also due to the decomposition of erythrocytes during a long run (Peeling et al., 2009; Koe-hler et al., 2012). Slovenian adolescent males aged 13 to 18 should therefore consume 12 mg of iron per day and females 15 mg per day (National Institute for Public Health, 2016). The only exception are vegetarian athletes who require higher intakes due to the reduced bioavailability of non-heme iron (Desbrow & Leveritt, 2015). Calcium and vitamin D are key nutrients for the development and maintenance of bone mass. Due to intense bone growth during adolescence, calcium needs are increased in both males and females. For 13- to 18-year olds, the recommended daily intake of calcium is 1200 mg (National Institute for Public Health, 2016), which applies to adolescent athletes, too, until there is more research available (Desbrow & Leveritt, 2015). Vitamin D plays an important role in calcium and phosphate metabolism and calcium integration into bones and teeth, and in the operation of the immune and muscle systems (Desbrow & Leveritt, 2015). Approximately 90% of our daily vitamin D requirements are covered by internal synthesis in the skin after exposure to ultraviolet rays; dietary intake contributing only 10% of the requirements (Koundourakis, Avgo-ustinaki, Malliaraki, & Margioris, 2016). In Slovenia, typical nutritional vitamin D intakes (2-4 ^g daily) in adolescents in the absence of internal synthesis do not suffice to achieve recommended serum concentrations. The difference between the intake and the recommended value of 20 ^g must be reached through frequent exposure to the sun and/or taking a vitamin D formulation (National Institute for Public Health, 2016). In latitudes above 35° north, which applies to Slovenia, the sun rays angle in winter are too oblique for efficient skin vitamin D synthesis (Holick, 2008), apart from that, competitive young swimmers spend long hours practicing indoor also in autumn and spring, which poses them at risk for vitamin D deficiency. Geiker et al. (2017) reported that 45% of the 29 swimmers (16-24 years old) residing at latitude 55-56° north had 25-hydroxycholecalciferol below 50 nmol/L in March and April. It is known that adolescent athletes have a higher height to body mass ratio (Petrie et al., 2004) and a lower sweating rate (Shibasaki, Inoue, Kondo & Iwata, 1997) than 18 ANNALES KINESIOLOGIAE • 9 • 2018 • 1 Vesna SIMIC, Nina MOHORKO: NUTRITIONAL STRATEGIES OF SLOVENIAN NATIONAL JUNIOR SWIMMING TEAM, 15-34 adults. A decreased sweating rate is an advantage in maintaining hydration status and at the same time decreases the success of thermoregulation. Sawka et al. (2007) propose fluid replacement during exercise to such a degree that hypohydration exceeding 2% is prevented. Desbrow et al. (2014) and Smith, Holmes & McAllister (2015), who deal with adolescent athletes, recommend the same. Water or milk should not be replaced by sports drinks that contain electrolytes and CHO because sodium losses through sweating are smaller than in adults (Meyer, Volterman, Timmons, & Boguslaw, 2012). Sports drinks are recommended only in long-term intense physical activity. Drinking caffeinated energy drinks is advised against in young athletes (Desbrow & Leveritt, 2015). The use of sports food (sports drinks, sports bars, sports confectionery, sports gels, liquid meal supplements, ...) is justified in adolescents in cases of long and intensive training (Desbrow et al., 2014). Replacing nutrients with dietary supplements, such as calcium, iron and vitamin D, is also justified when a deficiency is confirmed (International Olympic Committee (IOC), 2011). The use of ergogenics is advised against because it is inappropriate and unnecessary, and in addition their safe use in all age groups has not been confirmed (International Olympic Committee (IOC), 2011). To fulfil their increased energy requirements, young athletes are recommended three main meals and two snacks (Desbrow & Leveritt, 2015). A meal rich in CHO (1-4 g CHO/kg BW) is recommended 1-4 hours before activity. During exercise lasting 1-2.5 hours, 30-60 g CHO/h should be consumed. The post exercise meal should contain 1.0-1.2 g CHO/kg BW and 20 g of protein (Smith et al., 2015). Such a meal, consumed directly or as soon as possible after exercise, enables the refilling of glyco-gen stores, muscle repair and replaces lost fluid. This is especially important in athletes who compete several days in a row (e.g. in a tournaments) or train more than once per day (Desbrow & Leveritt, 2015). The aim of our study was to assess the nutritional strategies of Slovenian national junior swimming team and compare them with recommendations. METHODS Data Collection All members of Slovenian national junior swimming team were invited to participate in the study. The eligibility criteria for the national team are determined by the Slovenian swimming federation, which also provided us with the list of swimmers (27 competitive young swimmers). Out of 21 swimmers for whom written consents for personal data processing were obtained, 2 were excluded from analysis due to inadequate food diaries, confining the final sample to 19 competitive young swimmers (Figure 1, Table 1). The data was collected from October to December 2016 and analysed in February 2017. 19 ANNALES KINESIOLOGIAE • 9 • 2018 • 1 Vesna SIMIC, Nina MOHORKO: NUTRITIONAL STRATEGIES OF SLOVENIAN NATIONAL JUNIOR SWIMMING TEAM, 15-34 Invited: All members of Slovenian junior national swimming team (N = 27). Excluded (N = 8): Injured (N = 2), Refused to participate (N = 4), Inadequate food diaries (N = 2). 1 Final sample (N = 19). Figure 1: Swimmers flow diagram. Anthropometric Measurements We collected weight and height data from anthropometric measurements regularly performed during preparation training cycles. Swimmers were weighed to the nearest 10 g (M 304641-01, AED) and height was measured to the nearest 0.5 cm (Stadiometer, M 304641-01 (ADE). Whole body BIA (BIA 101 Anniversary AKERN, Florence, Italy, medically approved: EN ISO 13485 - ISO 9001) was performed using an alternating sinusoidal electric current of 400 ^A at an operating frequency of 50 kHz according to recommendations (Kyle et al., 2004) for FFM assessment, that was needed for EA calculation. Dietary Assessment and Energy Consumption Evaluation Data were collected from food and activity diaries. Swimmers were asked to keep 3-day weighted food and activity diaries for three consecutive days (including one weekend day). Swimmers were fully briefed on how to complete the diary and asked to continue their normal diet and physical activity. They were asked to include food labels and recipes for mixed dishes in their record. For each day, they had to record the kind, duration and intensity of the physical activity. The dietary intake was assessed using Open Platform for Clinical Nutrition (OPEN), that is an online, freely accessible, dietary assessment and planning tool for the analysis of food diary (http://www.opkp.si/en_GB/cms/vstopna-stran). OPEN food composition data was taken from the Slovenian food composition database (Golob et al., 2006); or if not available there, from the Souci, Fachmann & Kraut Food composition and nutrition tables (2008) and/or from the USDA National Nutrient Database for Standard Referen- 20 ANNALES KINESIOLOGIAE • 9 • 2018 • 1 Vesna SIMIC, Nina MOHORKO: NUTRITIONAL STRATEGIES OF SLOVENIAN NATIONAL JUNIOR SWIMMING TEAM, 15-34 ce (lUtp://\v\v\v.ars.usda.gov/Senices/docs.lUm?docid=8%4). Food composition data applied by the OPEN meet the European standard for food data CEN/TC 387, available at http://www.cen.eu/. EI, macronutrient intake and calcium, iron and vitamin D intakes were evaluated. To examine the suitability of energy consumption, EA was calculated. EA represents the energy that is available for body function, growth and development taking in consideration exercise energy expenditure (EEE) during planned physical activity (Desbrow et al., 2014). Metabolic equivalent of task (MET) was used for EEE evaluation, as suggested by OPEN. Questionnaire Data from a questionnaire that was developed by nutrition expert in charge of nutrition support of national swimming team, were analysed. Swimmers were asked to answer the questionnaire on health parameters (number of infections, menstrual cycle, growth), nutritional habits, timing of meal intake, use of dietary supplements and sports food, as well as type, intensity and the duration of exercise. Statistical Analysis Answers from the questionnaire that refer to sports nutrition recommendations and dietary intake compared to recommended values were processed in Microsoft Excel (IBM Corp. Released 2011), while anthropometric data and dietary intakes were processed with SPSS 20.0 (IBM SPSS Statistics for Windows, Version 20.0. Armonk, NY: IBM Corp.). The descriptive statistics was used to determine averages, standard deviations and minimum and maximum values. The Shapiro-Wilk test was used for assessing the normality in the distribution of variables, one sample T-test and independent samples T-test were used to evaluate the difference from recommended values and difference between genders. Statistical significance was set at P < 0,05. Spearman and Eta correlations were performed to detect different associations between dietary intakes and frequency of infection as well as regularity of menstrual cycle. 21 Table 1: Characteristics of swimmers divided by gender Average (± SD) t* p (2-tailed)* All (N= 19) Male swimmers (N= 6) Female swimmers (N=13) Age (years) 14,95 ± 1,22 16,17 ±0,75 14,38 ±0,96 3,99 0,001 Body height (cm) 173,97 ±7,70 181,92 ±4,32 170,31 ±5,91 4,28 0,001 Body weight (kg) 62,35 ± 10,07 73,33 ±4,88 57,28 ± 7,35 4,84 0,000 BMR (kcal/day) (kJ/day) 1608,50 ± 180,30 (6729,96 ± 745,38 1827,88 ±91,55 (7647,85 ± 383,04) 1507,25 ± 100,50 (6306,33 ± 420,49) 6,63 0,000 FFM (kg) 51,58 ±9,39 62,97 ±3,80 46,33 ± 5,62 6,54 0,000 Fat mass (%) 17,44 ±3,77 14,08 ± 1,75 18,99 ±3,43 3,28 0,004 Training load (h/week) 20,78 ±2,59 21,42 ±3,52 20,48 ±2,15 0,72 0,480 Energy availability (kcal/kg FFM) (kJ/kg FFM) 37,01 ± 12,99 (155,23 ±54,35) 43,48 ±9,16 (181,92 ±38,32) 34,02 ± 13,69 (143,09 ±57,28) 1,53 0,144 BMR - basal metabolic rate, FFM -fat free mass *Difference between male and female swimmers Table 2: Nutritional intakes of swimmers divided by gender Average (± SD) t* p (2-tailed)* All (N= 19) Male swimmers (N= 6) Female swimmers (N=13) CHO intake/kg BW (g/kg) 7,24 ± 1,92 8,08 ± 1,32 6,85 ±2,07 1,33 0,201 Protein intake/kg BW (g/kg) 2.03 ±0.76 2,70 ± 0,90 1,72 ±0,44 3,21 0,005 Fat (% EI) 25,06 ±25,98 23,07 ±4,54 25,98 ± 7,10 -0,916 0,373 Saturated fat (% EI) 8,67 ± 9,00 8,67 ± 2,94 9,00 ± 2,48 -0,257 0,800 Iron itake (mg) 19,47 ±7,18 25,75 ±6,89 16,57 ±5,35 3,180 0,005 Calcium intake (mg) 1156,99 ± 516,64 1715,57 ± 352,75 899,19 ±347,17 4,742 0,000 Vitamin D intake (jig) 4,84 ± 4,76 9,20 ±6,31 2,83 ± 1,88 2,424 0,056 EI - energy intake, CHO -carbohydrate, BW - body weight *Difference between male and female swimmers ft o o p ft v1 5 I ri p S- g, 5 g i. 6 I ft 02 8 G. 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