Abstract
tritional strategy during an ultra-endurance triathlon (UET) is one of the main concerns of athletes competing in such events. The purpose of this study is to provide a proper characterization of the energy and fluid intake during real competition in male triathletes during a complete UET and to estimate the energy expenditure (EE) and the fluid balance through the race. Methods: Eleven triathletes performed a UET. All food and drinks ingested during the race were weighed and recorded in order to assess the energy intake (EI) during the race. The EE was estimated from heart rate (HR) recordings during the race, using the individual HR-oxygen uptake (Vo 2) regressions developed from three incremental tests on the 50- m swimming pool, cycle ergometer, and running treadmill. Additionally, body mass (BM), total body water (TBW) and intracellular (ICW) and extracellular water (ECW) were assessed before and after the race using a multifrequency bioimpedance device (BIA). Results: Mean competition time and HR was 755 ± 69 min and 137 ± 6 beats /min, respectively. Mean EI was 3643 ± 1219 kcal and the estimated EE was 11,009 ± 664 kcal. Consequently, athletes showed an energy deficit of 7365 ± 1286 kcal (66.9% ± 11.7%). BM decreased significantly after the race and significant losses of TBW were found. Such losses were more related to a reduction of extracellular fluids than
± 6 beats /min, respectively. Mean EI was 3643 ± 1219 kcal and the estimated EE was 11,009 ± 664 kcal. Consequently, athletes showed an energy deficit of 7365 ± 1286 kcal (66.9% ± 11.7%). BM decreased significantly after the race and significant losses of TBW were found. Such losses were more related to a reduction of extracellular fluids than intracellular fluids. Conclusions: Our results confirm the high energy demands of UET races, which are not compensated by nutrient and fluid intake, resulting in a large energy deficit. OPEN ACCESS
Nutrients 2015, 7 210 Keywords: energy balance; triathlon; energy expenditure; energy intake; macronutrient consumption; endurance; body water 1. Introduction The popularity of ultra-endurance triathlon (UET) races (3.8- km swim, 180- km cycle, 42.2- km run) has greatly increased since the first Ironman was held in 1978 [1]. Given the long duration of these sport events, one of the main goals for athletes is to manage the consumption of food and drinks throughout the race [2] so as to enhance performance while maintaining body homeostasis. It has been estimated that the energy expenditure (EE) for a UET may range from 8500–11,500 Kcal [2 –4]. However, to the best of our knowledge, only two previous studies have investigated this issue under field conditions. Kimber et al., [3] assessed the energy balance of a UET using HR-oxygen uptake (Vo 2) regression equations during cycling and running as well as a multiple regression equation during the swimming section. They estimated an EE of 10,036 kcal and 8550 kcal in 10 males and 8 females, respectively. However, the energy intake (EI) was only 3940 kcal and 3115 kcal in both groups showing an energy deficit above 60% through the race. In a case study, Cuddy et al. , [5] combined two different approaches to assess the EE; indirect calorimetry and doubly labeled water. The data from both assessments were similar indicating that the EE of the athlete was ~9000 kcal. Nevertheless, this study did not assess the dietary consumption and fluid ingestion of the athlete during the event and, consequently, the EI and the energy deficit were not shown. Therefore, given this limitation of data, it seems important to address new research investigating the energy demands and the nutritional pattern of triathletes during real events. Another key point for exercise performance in UET is fluid ingestion, which is not only important for performance, but also necessary to maintain a proper fluid homeostasis and to guarantee athlete’s health during ultra-endurance events [6]. Previous studies by Speedy et al. [7–10] have shown that triathletes performing a UET may suffer from exercise- associated hyponatremia even despite modest fluid
Another key point for exercise performance in UET is fluid ingestion, which is not only important for performance, but also necessary to maintain a proper fluid homeostasis and to guarantee athlete’s health during ultra-endurance events [6]. Previous studies by Speedy et al. [7–10] have shown that triathletes performing a UET may suffer from exercise- associated hyponatremia even despite modest fluid intakes. This fact can be linked to renal function disturbances [11,12] which may induce an overload of extracellular water (ECW). However, changes in body mass (BM) during longer events are not only related with fluid balance. The reduction of the body stores of energy can also explain changes in the BM of athletes after ultra-endurance events. For instance, there is evidence indicating a significant decrease in muscle density (glycogen loss) and fat mass of athletes after a UET [13 –16]. In addition, Laursen et al. [17] reported that a body mass loss of up to 3% was not linked with thermoregulatory failure in 10 triathletes performing a UET suggesting that part of the BM reduction occurred due to losses of glycogen and fat. Accordingly, the main aim of this study was to provide a proper characterization of the energy and fluid intake of a group of male triathletes during a whole UET. A second aim was to estimate the EE and the fluid balance (intra and extracellular stores) of triathletes throughout the race using three different locomotion- specific individualized equations. We hypothesized that triathletes performing a UET would incur a substantial energy deficit of >70% due to the high energy demands of these types of events and
Nutrients 2015, 7 211 the limited food intake of athletes through the race. We also hypothesized that sweat losses during UET under hot environmental conditions would not be compensated by fluid ingestion. 2. Experimental Section 2.1. Subjects We placed an advertisement on the triathlon race webpage to recruit non- professional male triathletes. The inclusion criteria were to train at least 10 h per week and the participation in a minimum of one UET during the past 3 years. Eleven triathletes volunteered to participate in the study (mean ± SD: age 36.8 ± 5.1 years, BM 75.5 ± 6.4 kg, height 1.74 ± 0.06 m, BMI 24.8 ± 1.7 kg/m 2 , maximal oxygen uptake (Vo 2max) 5.03 ± 0.4 L/min, 66.9 ± 4.1 mL/kg·min). Triathletes had an average of 10 ± 3 years of experience in UET and ultra-endurance events, and they had been training regularly for approximately 15–18 h per week for at least the three previous years. Before participating in the study, all subjects undertook a medical examination which included a physical examination (body composition), a medical questionnaire, and an electrocardiogram within the same year to ensure that each participant was in good health and gave their informed written consent, which was in accordance with legal requirements and the Declaration of Helsinki, and approved by the University of Barcelona’s Ethics Committee. 2.2. The Ultra- Endurance Triathlon The triathlon was the Extreme Man Salou-Costa Daurada triathlon, an official race within the Catalan Triathlon Federation calendar composed of three stages consisting of a 3.8 km swim, 180 km cycle with a positive elevation over 2600 m and a 42.2 km marathon run. The average (range) ambient temperature was 26 °C (13–30 °C), the water temperature was 21 °C (20.8–21.2 °C) and the relative humidity was 77% (64%–94%). The mean wind speed was 1.3 m/s (range 0.3–5 m/s). HR was monitored during the entire race using waterproof Polar RCX5 (Polar Electro, Kempele, Finland) portable monitors and averaged at 5 s intervals. 2.3. Preliminary Testing Two weeks before the race, all subjects reported three times to the physiology laboratory (or to a
and the relative humidity was 77% (64%–94%). The mean wind speed was 1.3 m/s (range 0.3–5 m/s). HR was monitored during the entire race using waterproof Polar RCX5 (Polar Electro, Kempele, Finland) portable monitors and averaged at 5 s intervals. 2.3. Preliminary Testing Two weeks before the race, all subjects reported three times to the physiology laboratory (or to a swimming pool) to perform three incremental tests to volitional exhaustion in each discipline under randomised conditions separated by at least 48 h. The tests consisted of a graded swimming test in a 50-m pool, a graded cycling ergometry test and a graded treadmill running test [18] . Running and cycling tests were executed under controlled conditions (22 ± 1 °C, 40%–60% relative humidity, Pb 1013–1027 hPa) . All the tests were performed at the same time of day to minimize the effects of circadian rhythms. Athletes were asked to refrain from caffeine, alcohol and heavy exercise on the day before the tests, and to report to the laboratory well hydrated after having eaten more than three hours before.
Nutrients 2015, 7 212 2.4. Nutritional Data After the tests, triathletes were encouraged to follow their own diet scheduled usually in this sort of competition the days before and during the competition. During the race, 25 trained researchers were divided among the refreshment points collecting all the wraps and bottles of each triathlete. Additionally, upon completion the UET, triathletes were asked to confirm the data collected during the event by researchers. Then, software was used to assess macronutrient intake (Centre d’Ensenyament Superior de Nutrició i Dietètica, University of Barcelona, Santa Coloma de Gramenet, Spain). 2.5. Body Mass and Bioimpedance Bioelectricity Variables BM was measured using a Seca 710 ® (Seca GmbH, Hamburg, Germany) weighing scale and TBW, ICW and ECW were measured using a multifrequency bioimpedance analyzer (Z-Metrix ® , BioparHom ® , La Motte Servolex, France) before and 30 min after the race (to avoid skin temperature effect on BIA). 2.6. Load of Exercise and Energy Expenditure To estimate the total work load of exercise performed by each triathlete, we used the training impulse (TRIMP) method as previously described by Bescós et al. [19]. The individually derived linear relationship between HR and V o 2 was used to estimate the oxygen cost during the work efforts for each segment. Three different individualized equations were established. These were three linear regression equations derived from data during each incremental exercise test. To estimate energy expenditure during the race, we used an energy equivalent of oxygen based on the mean intensity during racing time, as described in a previous study [20] . 2.7. Statistical Analysis Descriptive data is presented as mean ± standard deviation unless otherwise indicated. A one-way analysis of variance (ANOVA) was used to show differences between disciplines (swimming, cycling and running) during competition in the mean HR and percentage of time spent in each intensity zone as well as between macronutrient, fluid and sodium intake in each stage (cycling and running). Furthermore, another ANOVA test was performed to analyze differences between BIA data (TBW, ECW and ICW) before and after the race. Post-hoc analyses were performed using Tukey HSD.
and running) during competition in the mean HR and percentage of time spent in each intensity zone as well as between macronutrient, fluid and sodium intake in each stage (cycling and running). Furthermore, another ANOVA test was performed to analyze differences between BIA data (TBW, ECW and ICW) before and after the race. Post-hoc analyses were performed using Tukey HSD. Pearson’s rank correlation analysis was used to assess the relationship between the individual physiological variables measured and performance in each stage of the triathlon, as well as the overall race time. A backward stepwise multiple linear regression analysis was used to determine the best predictors of final racing time after checking the correlation matrix for collinearity. Significance was set at p < 0.05 and all analyses were performed using PASW Statistics v 18 for Windows.
Nutrients 2015, 7 213 3. Results 3.1. Performance during the Ultra-Endurance Triathlon All subjects successfully finished the race. Table 1 summarizes the main outcomes in each stage of the competition. As expected, time performed within zone I was significantly higher (69%) than in zone II (22%) and zone III (9%) (p < 0.001). 3.2. Macronutrient Intake Food and fluids consumed during the UET were mainly those provided at the aid stations by the triathlon organizers. Table 2 summarizes the percent contribution from food and fluids consumed by athletes during the event. Table 3 summarizes the consumption of macronutrients during the race. Subjects consumed 927 ± 178 g (6.2 ± 1.3 g/kg; 84 ± 18 g/h; 89.9% ± 3.5%) of carbohydrates (CHO), which provided the main source of energy consumed during the race (p < 0.001). The consumption of solid CHO (697 ± 147 g) was higher than the consumption of fluid CHO (229 ± 67 g; p < 0.001). Macronutrient intake was significantly greater in the cycling stage compared with the running stage (p < 0.001). However, regarding CHO, there were no statistical differences between both stages (cycling: 1.4 ± 0.5; running: 1.3 ± 0.3 g/min). 3.3. Fluid and Sodium Intake Table 4 summarizes the fluid balance and the sodium intake during the UET. In absolute values, fluid and sodium intakes were significantly higher during the cycling stage than in the running stage (p < 0.001). However, when comparing relative values (fluid intake/time of exercise), fluid intake was significantly greater during the running period compared to the cycling stage ((395 ± 183) and (362 ± 172) mL/h, respectively; p < 0.001). 3.4. Energy Balance Figure 1 shows the box- and-whisker plot of the estimated EI and EE during each stage of the competition and in overall terms. EE (11,009 ± 664 kcal; 46.1 ± 2.8 MJ) was significantly higher than EI (3643 ± 1219 kcal; 15.3 ± 5.1 MJ; p < 0.001) meaning that an energy deficit of 7365 ± 1286 kcal (30.8 ± 5.4 MJ; 66.9% ± 11.7%) occurred. Solid food significantly provided more energy than fluids (2812 ±
of the competition and in overall terms. EE (11,009 ± 664 kcal; 46.1 ± 2.8 MJ) was significantly higher than EI (3643 ± 1219 kcal; 15.3 ± 5.1 MJ; p < 0.001) meaning that an energy deficit of 7365 ± 1286 kcal (30.8 ± 5.4 MJ; 66.9% ± 11.7%) occurred. Solid food significantly provided more energy than fluids (2812 ± 1150 kcal; 11.8 ± 4.8 MJ) (831 ± 668 kcal; 3.5 ± 2.8 MJ; p < 0.001). Absolute EI was higher during the cycling stage (2391 ± 82.9 kcal; 10.0 ± 0.4 MJ; 65.63%) compared to the running stage (1252 ± 43.1 kcal; 5.24 ± 0.18 MJ; 34.4%; p < 0.001). Mean ratios between EI and EE during the cycling, running and swimming stages (i.e., including the swimming stage and transitions times) were 0.37 ± 0.14, 0.34 ± 0.13 and 0.33 ± 0.11, respectively.
Nutrients 2015, 7 214 Table 1. Swim, cycle, run and overall variables during the ultra-endurance triathlon race. Stages Racing Time (min) TRIMP (a.u.) Average HR (bpm) Time Spent in Zone I (min) Time Spent in Zone II (min) Time Spent in Zone III (min) Average Speed (km/h) Swimming 63.1 (8.6) 186.0 (33.9) 149.0 (9.1) 4.0 (10.9) 0.01 (0.03) 60.7 (13.7) 3.7 (0.5) Cycling 417.2 (38.4) 553.7 (109.7) 137.7 (5.4) 302.6 (84.2) 114.1 (76.8) 7.6 (20.5) 26.1 (2.3) Running 257.3 (36.3) 313.9 (86.0) 133.9 (10.8) 209.2 (90.9) 51.7 (79.9) 0.4 (0.9) 10.0 (1.3) Total 754.6 (68.8) 1053.6 (173.9) 136.7 (6.3) 515.8 (137.2) * 165.8 (138.0) 68.7 (22.4) Data are presented as mean (SD). TRIMP: training impulse (a.u., arbitrary units); HR: heart rate; Vo 2: oxygen uptake; Time spent in zone I: below to the first ventilatory threshold; zone II: between the first ventilatory threshold and the second ventilatory threshold; zone III: above to the second ventilatory threshold. * The time spent in zone I is significantly longer than the time value in zone II and zone III (p < 0.001). Table 2. Percentage of energy contribution from food and fluids during the ultra-endurance triathlon race. Food and Fluids Energy Contribution (%) Cycling Running Total Sport gels 20.2 62.6 35.3 Sport bars 34.4 6.2 24.4 Sport drinks 20.3 13.5 17.9 Sandwich (parma jam and cheese) 13.9 2.0 9.7 Dried fruits (almonds and nuts) 4.2 3.6 4.0 Caffeinated drinks 1.9 6.0 3.3 Fruits (banana, apple and orange) 1.1 6.1 2.9 Cereals 3.1 - 2.0 Others (protein supplement) 0.8 - 0.5
Nutrients 2015, 7 215 Table 3. Macronutrient intake during the ultra-endurance triathlon race. Cycling Running Total Carbohydrates Solids (g) 405.7 (147.8) 291.5 (60.8) 697.2 (147.2) † Fluids (g) 177.8 (67.0) 51.6 (24.3) 229.4 (67.0) Total (g) 583.5 (176.3) § 349.0 (73.3) 926.6 (177.5) * g/kg a 7.8 (2.3) 4.7 (1.2) 6.2 (1.3) g/h b 84 (30) 78 (18) 84 (18) % c 83.2 (5.6) 96.6 (3.8) 89.9 (3.5) Proteins Total (g) 40.7 (11.5) § 4.6 (3.4) 45.4 (12.0) g/kg 0.6 (0.2) 0.1 (0.0) 0.3 (0.1) % 6.4 (2.9) 1.3 (1.0) 3.8 (1.6) Lipids Total (g) 69.1 (18.0) § 7.7 (10.5) 76.8 (20.4) g/kg 0.9 (0.3) 0.1 (0.1) 0.5 (0.1) % 10.5 (3.6) 2.2 (3.0) 6.3 (2.4) Data are presented as mean (SD). a Ratio between total macronutrient intake (g) and body mass (kg); b Ratio between total carbohydrate intake (g) and total racing time (min); c Macronutrient percentage of the total energy intake in each segment and in total; * The amount of carbohydrates was significantly higher than the amount of protein and lipids (p < 0.001); † The consumption of solid CHO was higher than that of fluid CHO (p < 0.001); § The intake amount was significantly higher in the cycling stage than in the running stage (p < 0.001). Table 4. Fluid and sodium intake during the ultra-endurance triathlon. Cycling Running Total a Fluid intake (mL) 2530.9 (1255.9) * 1657.3 (717.4) 4188.2 (1836.9) Fluid intake rate (mL/h) 361.6 (171.8) † 394.5 (183.2) 366.6 (146.9) Sodium (mg) From fluids 485.2 (307.5) * 232.0 (208.5) 2152.2 (1124.2) From food 1135.9 (953.9) * 299.1 (369.3) Data are presented as mean (SD). a Includes time of swim and race transitions; * Values are significantly higher during cycling stage than in the running stage (p < 0.001); † Values are significantly lower during running stage than in the cycling stage (p < 0.001). 3.5. Body Mass and Bioimpedance Bioelectricity Variables BM decreased significantly after the race (−4.3 ± 1.4 kg; −5.7% ± 1.9%, p < 0.001). Table 5 summarizes the differences in the TBW, ECW and ICW before competition and after competition.
Description
This study characterizes energy and fluid intake during an ultra-endurance triathlon.