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Journal of Sports Sciences Publication details, including instructions for authors and subscription information: http://www.tandfonline.com/loi/rjsp20
Relationship between physiological parameters and performance during a half-ironman triathlon in the heat a
a
ab
a
Juan Del Coso , Cristina González , Javier Abian-Vicen , Juan José Salinero Martín , a
a
a
a
a
Lidon Soriano , Francisco Areces , Diana Ruiz , Cesar Gallo , Beatriz Lara & Julio CallejaGonzález
c
a
Sport Sciences Institute, Camilo José Cela University, Madrid, Spain
b
Faculty of Sports Sciences, University of Castilla-La Mancha, Toledo, Spain
c
Laboratory of Analysis of Sport Performance, Sport and Physical Education Department, University of the Basque Country, Vitoria, Spain Published online: 13 May 2014.
To cite this article: Juan Del Coso, Cristina González, Javier Abian-Vicen, Juan José Salinero Martín, Lidon Soriano, Francisco Areces, Diana Ruiz, Cesar Gallo, Beatriz Lara & Julio Calleja-González (2014) Relationship between physiological parameters and performance during a half-ironman triathlon in the heat, Journal of Sports Sciences, 32:18, 1680-1687, DOI: 10.1080/02640414.2014.915425 To link to this article: http://dx.doi.org/10.1080/02640414.2014.915425
PLEASE SCROLL DOWN FOR ARTICLE Taylor & Francis makes every effort to ensure the accuracy of all the information (the “Content”) contained in the publications on our platform. However, Taylor & Francis, our agents, and our licensors make no representations or warranties whatsoever as to the accuracy, completeness, or suitability for any purpose of the Content. Any opinions and views expressed in this publication are the opinions and views of the authors, and are not the views of or endorsed by Taylor & Francis. The accuracy of the Content should not be relied upon and should be independently verified with primary sources of information. Taylor and Francis shall not be liable for any losses, actions, claims, proceedings, demands, costs, expenses, damages, and other liabilities whatsoever or howsoever caused arising directly or indirectly in connection with, in relation to or arising out of the use of the Content. This article may be used for research, teaching, and private study purposes. Any substantial or systematic reproduction, redistribution, reselling, loan, sub-licensing, systematic supply, or distribution in any form to anyone is expressly forbidden. Terms & Conditions of access and use can be found at http:// www.tandfonline.com/page/terms-and-conditions
Journal of Sports Sciences, 2014 Vol. 32, No. 18, 1680–1687, http://dx.doi.org/10.1080/02640414.2014.915425
Relationship between physiological parameters and performance during a half-ironman triathlon in the heat
JUAN DEL COSO1, CRISTINA GONZÁLEZ1, JAVIER ABIAN-VICEN1,2, JUAN JOSÉ SALINERO MARTÍN1, LIDON SORIANO1, FRANCISCO ARECES1, DIANA RUIZ1, CESAR GALLO1, BEATRIZ LARA1 & JULIO CALLEJA-GONZÁLEZ3
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1
Sport Sciences Institute, Camilo José Cela University, Madrid, Spain, 2Faculty of Sports Sciences, University of Castilla-La Mancha, Toledo, Spain and 3Laboratory of Analysis of Sport Performance, Sport and Physical Education Department, University of the Basque Country, Vitoria, Spain (Accepted 10 April 2014)
Abstract Triathlon is a popular outdoor endurance sport performed under a variety of environmental conditions. The aim of this study was to assess physiological variables before and after a half-ironman triathlon in the heat and to analyse their relationship with performance. Thirty-four well-trained triathletes completed a half-ironman triathlon in a mean dry temperature of 29 ± 3ºC. Before and within 1 min after the end of the race, body mass, core temperature, maximal jump height and venous blood samples were obtained. Mean race time was 315 ± 40 min, with swimming (11 ± 1%), cycling (49 ± 2%) and running (40 ± 3%) representing different amounts of the total race time. At the end of the competition, body mass changed by −3.8 ± 1.6% and the change in body mass correlated positively with race time (r = 0.64; P < 0.001). Core temperature increased from 37.5 ± 0.6ºC to 38.8 ± 0.7ºC (P < 0.001) and post-race core temperature correlated negatively with race time (r = −0.47; P = 0.007). Race time correlated positively with the decrease in jump height (r = 0.38; P = 0.043), post-race serum creatine kinase (r = 0.55; P = 0.001) and myoglobin concentrations (r = 0.39; P = 0.022). In a half-ironman triathlon in the heat, greater reductions in body mass and higher post-competition core temperatures were present in faster triathletes. In contrast, slower triathletes presented higher levels of muscle damage and decreased muscle performance. Keywords: muscle damage, performance, endurance athlete, myoglobin, dehydration
Introduction Triathlon is an outdoor endurance sport that has gained popularity in the last few decades (Jeukendrup, 2011). A triathlon race involves swimming, cycling and running in immediate sequence over various distances. During triathlon events, participants compete for fastest overall race time, including timed transitions between the swim, bike and run legs. Race time during a triathlon competition depends on numerous physiological characteristics, anthropometry, pre-race training, nutrition and environmental conditions during the race (Knechtle, Knechtle, & Rosemann, 2011). From all the factors that take place during the day of the event, preventing excessive dehydration by drinking during the race has been suggested as one of the main strategies for maintaining physical performance during triathlons (Jeukendrup, Jentjens, & Moseley, 2005). This recommendation is based on the
deleterious effects of progressive dehydration on endurance performance established under controlled laboratory conditions (Sawka et al., 2007). However, it seems that dehydration does not directly affect performance during real triathlon competitions such as ironman (Laursen et al., 2006; Sharwood, Collins, Goedecke, Wilson, & Noakes, 2002, 2004) and half-ironman triathlons (Coso et al., 2012a). Besides, the level body mass loss is unrelated to a higher prevalence of medical problems in triathletes (Sharwood et al., 2004). Other in situ factors affecting race time in endurance events might be serum electrolyte balance (mainly sodium) and muscle fibre damage. Hyponatremia (a reduction in plasma sodium concentration to below 135 mmol · L−1) has been previously reported in triathletes (Speedy et al., 2001, 2000). Hyponatremia is considered a serious medical problem during ultra-distance events (Jeukendrup
Correspondence: JUAN DEL COSO, Sport Sciences Institute, Camilo José Cela University, C/ Castillo de Alarcon, 49. Villafranca del Castillo, Exercise Physiology Laboratory, Villanueva de la Cañanda 28692, Spain. E-mail: [email protected] © 2014 Taylor & Francis
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Race time during a triathlon in the heat et al., 2005) and it has been associated with overconsumption of fluids during exercise (Noakes, 2011). However, serum electrolyte imbalances have also been related to a decrease of isometric muscle strength after cycling (Coso, Estevez, Baquero, & Mora-Rodriguez, 2008), although there is no investigation that relates electrolyte imbalance and race time during a half-ironman. Running (Coso, Fernández et al., 2013; Coso, Salinero et al., 2013) and cycling endurance activities (Bessa et al., 2008) may cause damage to the structure of the muscle fibre, ultimately affecting muscle performance during a triathlon. In a marathon, muscle damage has been positively correlated with a reduced capacity to generate muscle power (Coso, Salinero et al., 2013) and with a decreased running pace during the race (Coso, Fernández et al., 2013). In the half-ironman triathlon, pre-topost race jump height during a countermovement jump was reduced by 23%, while handgrip maximal force was unaffected by the race (Coso et al., 2012). Although muscle fibre damage is typically associated with the local component of muscle fatigue in endurance exercise activities, overall triathlon performance and the apparition of muscle fatigue can be also influenced by the sensory feedback from the muscle to the brain, based on the central governor model (Noakes, 2012). The aim of this study was to assess physiological variables before and after a half-ironman triathlon and to analyse their relationship with performance. We hypothesised that a decrease in body mass, hypoglycaemia, electrolyte imbalance and muscle damage would be positively related to reduced performance during a half-ironman triathlon.
Methods Participants Thirty-eight trained and experienced triathletes were recruited by email or through internet announcements to participate in this study. All participants had previous triathlon experience of at least 4 years, had trained for ~2 h · day-1 for 4–5 days/ week and had finished at least two half-ironman races during the three previous years. Four of these participants failed to complete the triathlon race and their data were excluded from the study. Thus, the data for 34 well-trained triathletes (30 males and 4 females) were included in the present investigation. Their mean ± s age, body mass and body height were 36 ± 6 years, 73.6 ± 6.4 kg and 178 ± 7 cm, respectively. All participants were free from any history of muscle, cardiac or kidney disorders, and were not taking any medication during the two weeks prior to competing. Participants were fully informed of any
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risks and discomforts associated with the experiments before giving their informed written consent to participate. The study was approved by the Camilo Jose Cela Ethics Committee in accordance with the latest version of the Declaration of Helsinki. Experimental protocol Three hours before the race, participants arrived at a zone close to the start line with no instructions about pre-exercise drinking or feeding. However, all of them indicated that they had eaten breakfast at least 1 h before arrival at the start line. On arrival, each participant was provided with an ingestible telemetry pill for the measurement of intestinal temperature (HT150002, HQ Inc, US). The pill was immediately ingested with 50 mL of tap water. Participants then rested for 5 min in a chair and a 22-G catheter was inserted into an antecubital vein. A 7-mL venous blood sample was drawn and 2 mL of the blood sample was inserted into an EDTA tube while the remaining blood was allowed to clot. Participants then completed a 10-min warm-up consisting of dynamic leg and arm exercises and practice jumps. After that, participants performed two countermovement vertical jumps (CMJs) for maximal height on a force platform (Quattrojump, Kistler, Switzerland) to assess pre-race leg power output. For this measurement, participants began stationary in an upright position with their weight evenly distributed over both feet. Each participant placed their hands on their waist in order to remove the influence of the arms on the jump. On command, the participant flexed their knees and jumped as high as possible while keeping the hands on the waist and landed with both feet. During the jumps, two experienced experimenters checked the correct execution of each jump (neither arm nor trunk movements during the impulse and landing phases) while jumps executed incorrectly were repeated. Handgrip maximal strength production in both hands was also measured using a handgrip dynamometer (Grip-D, Takei, Japan). Fifteen minutes before the race, participants were weighed in their competition clothes (± 50 g scale; Radwag, Poland; without wetsuit) and intestinal temperature was measured using a wireless data recorder (HT150001, HQ Inc, US). After that, participants headed to the start line without instructions about pace, rehydration or feeding, in an attempt to avoid any influence of this investigation on their habitual routines during the race. The race consisted of 1.9 km of swimming, 75 km of cycling (1100 m net increase in altitude) and 21.1 km of running. The triathlon was held in May 2012 in the surrounding area of a city located at 975 m altitude. Mean ± s (range) dry temperature during the event was 29 ± 3ºC (24–30ºC)
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with a relative humidity of 73 ± 8% (65–85%) and a dew point of 22 ± 3ºC (17–26ºC). The swim section was performed in a natural lake with water temperature at 19 ± 1ºC. All participants wore a neoprene wetsuit during the swim section. During the cycling section, all participants used bicycles with a carbon or aluminium frame. Within 1 min of the end of the race, participants went to a finish area and body mass and intestinal temperature were immediately measured using the same apparatus and methodology employed pre-race. Participants were instructed to avoid drinking from the finish line until the post-race weighing and an experimenter assured compliance. The body mass change attained during the race was calculated as a per cent reduction in body weight (pre-to post-race). Although the post-race body mass measurement included the sweat trapped in the clothing, this represents an error lower than 10% for the calculation of true hydration status (Cheuvront, Haymes, & Sawka, 2002). After that, participants performed two CMJs and the handgrip strength test, as previously described. Participants then rested for 5 min and a venous blood sample was obtained. The rate of perceived exertion over the course of the race was measured immediately postrace using a standard 6- to 20-point scale (Neely, Ljunggren, Sylvén, & Borg, 1992), and lower-leg muscle soreness was self-rated within 3 min of the end of the race using a 0- to 10-point scale (Ali, Caine, & Snow, 2007). After that, participants were provided with fluid (water and sports drinks) and finished their participation in the study. Blood samples A portion of each whole blood sample was introduced into a blood glucose analyser (Accu-chek, Spain) and glucose concentration was determined. The remaining blood was allowed to clot in serumseparating tubes (BD Vacutainer® Rapid Serum Tube, Spain) and then serum was separated by centrifugation (10 min at 5000 g) and frozen at −80ºC within the following 10 min. Forty-eight hours after the end of the race, the serum portion was analysed for sodium, potassium and chloride concentrations (Nova 16, NovaBiomedical, Spain). In addition, myoglobin, creatine kinase (CK) and lactate dehydrogenase (LDH) concentrations were measured as blood markers of muscle damage (AU5400, Beckman Coulter, US). Statistical analysis Data are presented as mean ± s and the significance level was set at P < 0.05. Normality was tested with the Shapiro–Wilk test with all the variables presenting a normal distribution. Changes in the variables from
pre- to post-race were analysed with Student’s t-tests for paired samples. For each pre- to post-race difference found in this study, we have calculated the effect size (ES) proposed by Cohen and 95% confidence interval. We used Pearson’s correlation to assess the association between two variables. In addition, we established two groups of participants according to their time in the competition, in order to compare the physiological responses of different performance groups. One group included 15 triathletes with a race time of less than 300 min (faster triathletes) and the other group included 15 triathletes with a race time of over 315 min (slower triathletes). Four participants (with race times between 300 and 315 min) were not included in the analysis per groups. Comparisons between these groups were performed with Student’s t-tests for unpaired samples while the ES and 95% confidence interval were calculated for the significant differences between groups. This statistical analysis was performed using the SPSS v.20 software package (SPSS Inc., Chicago, IL, USA). Results Triathlon race time and leg times The mean time taken to complete the half-ironman triathlon was 315 ± 40 min, with a range between 256 and 455 min. The time recorded for the swimming leg was 35 ± 4 min and represented only 11 ± 1% of the total time taken during the race. The cycling leg was completed in 153 ± 20 min and represented 49 ± 2% of the triathlon time, while the running leg (119 ± 20 min) represented 40 ± 3% of the race time. The triathlon race time was significantly related to cycling speed (r = −0.94; P < 0.001), running speed (r = −0.91; P < 0.001) and swimming speed (r = −0.53; P = 0.001), as shown in Figure 1. Body mass change and core temperature After the race, body mass decreased from 73.6 ± 6.4 to 70.9 ± 6.4 kg (95% CI = 2.18/3.03; ES, 0.35; P < 0.001) representing a mean body mass change of −3.8 ± 1.6%. Fifty per cent of the triathletes reduced their body mass by less than 4%, while the highest reduction in body mass was 6.2%. Only one triathlete of our study sample increased his pre-race body mass (from 73.5 to 74.0 kg) although this increase represented only 0.7%. The body mass change attained during the race was positively related to race time (r = 0.64; P < 0.001; Figure 2). In addition, body mass change was negatively related to cycling (r = −0.71; P < 0.001) and running velocities (r = −0.51; P = 0.003). Core temperature before the race was 37.5 ± 0.6ºC, and it increased to
Race time during a triathlon in the heat
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P = 0.019) and running speeds (r = 0.40; P = 0.023). Post-race core temperature was also negatively correlated with body mass change (r = −0.43; P = 0.015).
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Countermovement jump height and handgrip strength Before the race, mean CMJ height was 30.1 ± 4.4 cm and mean power output during the concentric phase of the jump was 1828 ± 360 W. After the race, CMJ height (27.5 ± 5.6 cm; 95% CI = 0.54/5.65; ES, 0.43; P < 0.001) and jump power output (1662 ± 395 W; 95% CI = 64.6/267; ES, 0.42; P < 0.001) were significantly reduced. The time recorded for the race correlated positively with the decrease in jump height (r = 0.38; P = 0.043) and the decrease in jump power output (r = 0.38; P = 0.045). Handgrip maximal strength production in the dominant hand was not different from pre-race (432 ± 79 N) to post-race (428 ± 81 N; 95% CI = −1.45/2.14; ES, 0.04; P = 0.70), and in the non-dominant hand it was reduced from pre-race (424 ± 66 N) to post-race (405 ± 80 N; 95% CI = 0.51/3.45; ES, 0.25; P = 0.01). The changes in handgrip strength were not correlated with race time.
Figure 1. Relationship between the total race time in a halfironman triathlon and the velocities during swimming (1.9 km), cycling (75 km) and running (21 km) legs. Each data point represents a participant in this investigation.
Blood responses Pre and post-race values for the blood and serum variables are shown in Table I. Blood osmolality and blood glucose concentration were significantly increased from pre-to-post-race (P < 0.001). Race time was negatively correlated to post-exercise blood serum osmolality (r = −0.37; P = 0.031), but race time was not correlated to blood glucose concentration. Serum sodium and calcium concentrations were significantly higher after the race (Table I; P < 0.001), but potassium and chloride concentrations remained unchanged after the race. Post-race serum sodium and chloride concentrations were negatively correlated with race time (r = −0.66; P < 0.001 and r = −0.35; P = 0.049) and body mass change (r = −0.66; P < 0.001 and r = −0.46; P = 0.009; Figure 3). Finally, the concentrations of
Figure 2. Relationship between the total race time in a half-ironman triathlon and body mass change and core temperature attained at the end of the race. Each data point represents a participant in this investigation.
38.8 ± 0.7ºC at the end of the race (95% CI = −1.44/−0.85; ES, 1.66; P < 0.001). The core temperature increase (1.3 ± 0.7ºC) was variable with changes of between 0.5ºC to 3.4ºC. Post-race core temperature was negatively correlated with total race time (r = −0.47; P = 0.007; Figure 2) and it was positively correlated with cycling (r = 0.41;
Table I. Blood responses before (pre) and after (post) a half-ironman triathlon race. Data are mean ± s for 34 triathletes. Variable (units) Blood osmolality (mOsm · kg−1) Glucose (mg · dL−1) Sodium (mmol · L−1) Potassium (mmol · L−1) Chloride (mmol · L1) Calcium (mmol · L−1) Myoglobin (µg · L−1) Creatine kinase (U · L−1) Lactate dehydrogenase (U · L−1)
Pre 291.1 114.2 140.6 4.6 102.5 9.5 32.9 169.3 318.5
± ± ± ± ± ± ± ± ±
Post 4.7 11.4 1.5 0.4 1.6 0.5 13.9 86.2 56.2
301.8 128.5 143.0 4.6 103.2 10.3 654.8 564.5 479.0
± ± ± ± ± ± ± ± ±
6.0 22.6 2.1 0.3 2.1 0.5 451.4 428.9 78.6
Δ (%)
Effect size
95% CI
P-value
3.5 10.8 1.7 0.5 0.7 8.7 2020 244 51.3
1.88 0.63 1.14 0.01 0.23 1.77 1.38 0.89 2.04
−12.4/−7.6 −24.0/−5.2 −3.33/−1.44 −8.74/4.57 −1.77/0.36 −23.8/−2.22 −778.8/−465.1 −536.2/−254.2 −175.5/−145.6
Journal of Sports Sciences Publication details, including instructions for authors and subscription information: http://www.tandfonline.com/loi/rjsp20
Relationship between physiological parameters and performance during a half-ironman triathlon in the heat a
a
ab
a
Juan Del Coso , Cristina González , Javier Abian-Vicen , Juan José Salinero Martín , a
a
a
a
a
Lidon Soriano , Francisco Areces , Diana Ruiz , Cesar Gallo , Beatriz Lara & Julio CallejaGonzález
c
a
Sport Sciences Institute, Camilo José Cela University, Madrid, Spain
b
Faculty of Sports Sciences, University of Castilla-La Mancha, Toledo, Spain
c
Laboratory of Analysis of Sport Performance, Sport and Physical Education Department, University of the Basque Country, Vitoria, Spain Published online: 13 May 2014.
To cite this article: Juan Del Coso, Cristina González, Javier Abian-Vicen, Juan José Salinero Martín, Lidon Soriano, Francisco Areces, Diana Ruiz, Cesar Gallo, Beatriz Lara & Julio Calleja-González (2014) Relationship between physiological parameters and performance during a half-ironman triathlon in the heat, Journal of Sports Sciences, 32:18, 1680-1687, DOI: 10.1080/02640414.2014.915425 To link to this article: http://dx.doi.org/10.1080/02640414.2014.915425
PLEASE SCROLL DOWN FOR ARTICLE Taylor & Francis makes every effort to ensure the accuracy of all the information (the “Content”) contained in the publications on our platform. However, Taylor & Francis, our agents, and our licensors make no representations or warranties whatsoever as to the accuracy, completeness, or suitability for any purpose of the Content. Any opinions and views expressed in this publication are the opinions and views of the authors, and are not the views of or endorsed by Taylor & Francis. The accuracy of the Content should not be relied upon and should be independently verified with primary sources of information. Taylor and Francis shall not be liable for any losses, actions, claims, proceedings, demands, costs, expenses, damages, and other liabilities whatsoever or howsoever caused arising directly or indirectly in connection with, in relation to or arising out of the use of the Content. This article may be used for research, teaching, and private study purposes. Any substantial or systematic reproduction, redistribution, reselling, loan, sub-licensing, systematic supply, or distribution in any form to anyone is expressly forbidden. Terms & Conditions of access and use can be found at http:// www.tandfonline.com/page/terms-and-conditions
Journal of Sports Sciences, 2014 Vol. 32, No. 18, 1680–1687, http://dx.doi.org/10.1080/02640414.2014.915425
Relationship between physiological parameters and performance during a half-ironman triathlon in the heat
JUAN DEL COSO1, CRISTINA GONZÁLEZ1, JAVIER ABIAN-VICEN1,2, JUAN JOSÉ SALINERO MARTÍN1, LIDON SORIANO1, FRANCISCO ARECES1, DIANA RUIZ1, CESAR GALLO1, BEATRIZ LARA1 & JULIO CALLEJA-GONZÁLEZ3
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1
Sport Sciences Institute, Camilo José Cela University, Madrid, Spain, 2Faculty of Sports Sciences, University of Castilla-La Mancha, Toledo, Spain and 3Laboratory of Analysis of Sport Performance, Sport and Physical Education Department, University of the Basque Country, Vitoria, Spain (Accepted 10 April 2014)
Abstract Triathlon is a popular outdoor endurance sport performed under a variety of environmental conditions. The aim of this study was to assess physiological variables before and after a half-ironman triathlon in the heat and to analyse their relationship with performance. Thirty-four well-trained triathletes completed a half-ironman triathlon in a mean dry temperature of 29 ± 3ºC. Before and within 1 min after the end of the race, body mass, core temperature, maximal jump height and venous blood samples were obtained. Mean race time was 315 ± 40 min, with swimming (11 ± 1%), cycling (49 ± 2%) and running (40 ± 3%) representing different amounts of the total race time. At the end of the competition, body mass changed by −3.8 ± 1.6% and the change in body mass correlated positively with race time (r = 0.64; P < 0.001). Core temperature increased from 37.5 ± 0.6ºC to 38.8 ± 0.7ºC (P < 0.001) and post-race core temperature correlated negatively with race time (r = −0.47; P = 0.007). Race time correlated positively with the decrease in jump height (r = 0.38; P = 0.043), post-race serum creatine kinase (r = 0.55; P = 0.001) and myoglobin concentrations (r = 0.39; P = 0.022). In a half-ironman triathlon in the heat, greater reductions in body mass and higher post-competition core temperatures were present in faster triathletes. In contrast, slower triathletes presented higher levels of muscle damage and decreased muscle performance. Keywords: muscle damage, performance, endurance athlete, myoglobin, dehydration
Introduction Triathlon is an outdoor endurance sport that has gained popularity in the last few decades (Jeukendrup, 2011). A triathlon race involves swimming, cycling and running in immediate sequence over various distances. During triathlon events, participants compete for fastest overall race time, including timed transitions between the swim, bike and run legs. Race time during a triathlon competition depends on numerous physiological characteristics, anthropometry, pre-race training, nutrition and environmental conditions during the race (Knechtle, Knechtle, & Rosemann, 2011). From all the factors that take place during the day of the event, preventing excessive dehydration by drinking during the race has been suggested as one of the main strategies for maintaining physical performance during triathlons (Jeukendrup, Jentjens, & Moseley, 2005). This recommendation is based on the
deleterious effects of progressive dehydration on endurance performance established under controlled laboratory conditions (Sawka et al., 2007). However, it seems that dehydration does not directly affect performance during real triathlon competitions such as ironman (Laursen et al., 2006; Sharwood, Collins, Goedecke, Wilson, & Noakes, 2002, 2004) and half-ironman triathlons (Coso et al., 2012a). Besides, the level body mass loss is unrelated to a higher prevalence of medical problems in triathletes (Sharwood et al., 2004). Other in situ factors affecting race time in endurance events might be serum electrolyte balance (mainly sodium) and muscle fibre damage. Hyponatremia (a reduction in plasma sodium concentration to below 135 mmol · L−1) has been previously reported in triathletes (Speedy et al., 2001, 2000). Hyponatremia is considered a serious medical problem during ultra-distance events (Jeukendrup
Correspondence: JUAN DEL COSO, Sport Sciences Institute, Camilo José Cela University, C/ Castillo de Alarcon, 49. Villafranca del Castillo, Exercise Physiology Laboratory, Villanueva de la Cañanda 28692, Spain. E-mail: [email protected] © 2014 Taylor & Francis
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Race time during a triathlon in the heat et al., 2005) and it has been associated with overconsumption of fluids during exercise (Noakes, 2011). However, serum electrolyte imbalances have also been related to a decrease of isometric muscle strength after cycling (Coso, Estevez, Baquero, & Mora-Rodriguez, 2008), although there is no investigation that relates electrolyte imbalance and race time during a half-ironman. Running (Coso, Fernández et al., 2013; Coso, Salinero et al., 2013) and cycling endurance activities (Bessa et al., 2008) may cause damage to the structure of the muscle fibre, ultimately affecting muscle performance during a triathlon. In a marathon, muscle damage has been positively correlated with a reduced capacity to generate muscle power (Coso, Salinero et al., 2013) and with a decreased running pace during the race (Coso, Fernández et al., 2013). In the half-ironman triathlon, pre-topost race jump height during a countermovement jump was reduced by 23%, while handgrip maximal force was unaffected by the race (Coso et al., 2012). Although muscle fibre damage is typically associated with the local component of muscle fatigue in endurance exercise activities, overall triathlon performance and the apparition of muscle fatigue can be also influenced by the sensory feedback from the muscle to the brain, based on the central governor model (Noakes, 2012). The aim of this study was to assess physiological variables before and after a half-ironman triathlon and to analyse their relationship with performance. We hypothesised that a decrease in body mass, hypoglycaemia, electrolyte imbalance and muscle damage would be positively related to reduced performance during a half-ironman triathlon.
Methods Participants Thirty-eight trained and experienced triathletes were recruited by email or through internet announcements to participate in this study. All participants had previous triathlon experience of at least 4 years, had trained for ~2 h · day-1 for 4–5 days/ week and had finished at least two half-ironman races during the three previous years. Four of these participants failed to complete the triathlon race and their data were excluded from the study. Thus, the data for 34 well-trained triathletes (30 males and 4 females) were included in the present investigation. Their mean ± s age, body mass and body height were 36 ± 6 years, 73.6 ± 6.4 kg and 178 ± 7 cm, respectively. All participants were free from any history of muscle, cardiac or kidney disorders, and were not taking any medication during the two weeks prior to competing. Participants were fully informed of any
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risks and discomforts associated with the experiments before giving their informed written consent to participate. The study was approved by the Camilo Jose Cela Ethics Committee in accordance with the latest version of the Declaration of Helsinki. Experimental protocol Three hours before the race, participants arrived at a zone close to the start line with no instructions about pre-exercise drinking or feeding. However, all of them indicated that they had eaten breakfast at least 1 h before arrival at the start line. On arrival, each participant was provided with an ingestible telemetry pill for the measurement of intestinal temperature (HT150002, HQ Inc, US). The pill was immediately ingested with 50 mL of tap water. Participants then rested for 5 min in a chair and a 22-G catheter was inserted into an antecubital vein. A 7-mL venous blood sample was drawn and 2 mL of the blood sample was inserted into an EDTA tube while the remaining blood was allowed to clot. Participants then completed a 10-min warm-up consisting of dynamic leg and arm exercises and practice jumps. After that, participants performed two countermovement vertical jumps (CMJs) for maximal height on a force platform (Quattrojump, Kistler, Switzerland) to assess pre-race leg power output. For this measurement, participants began stationary in an upright position with their weight evenly distributed over both feet. Each participant placed their hands on their waist in order to remove the influence of the arms on the jump. On command, the participant flexed their knees and jumped as high as possible while keeping the hands on the waist and landed with both feet. During the jumps, two experienced experimenters checked the correct execution of each jump (neither arm nor trunk movements during the impulse and landing phases) while jumps executed incorrectly were repeated. Handgrip maximal strength production in both hands was also measured using a handgrip dynamometer (Grip-D, Takei, Japan). Fifteen minutes before the race, participants were weighed in their competition clothes (± 50 g scale; Radwag, Poland; without wetsuit) and intestinal temperature was measured using a wireless data recorder (HT150001, HQ Inc, US). After that, participants headed to the start line without instructions about pace, rehydration or feeding, in an attempt to avoid any influence of this investigation on their habitual routines during the race. The race consisted of 1.9 km of swimming, 75 km of cycling (1100 m net increase in altitude) and 21.1 km of running. The triathlon was held in May 2012 in the surrounding area of a city located at 975 m altitude. Mean ± s (range) dry temperature during the event was 29 ± 3ºC (24–30ºC)
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with a relative humidity of 73 ± 8% (65–85%) and a dew point of 22 ± 3ºC (17–26ºC). The swim section was performed in a natural lake with water temperature at 19 ± 1ºC. All participants wore a neoprene wetsuit during the swim section. During the cycling section, all participants used bicycles with a carbon or aluminium frame. Within 1 min of the end of the race, participants went to a finish area and body mass and intestinal temperature were immediately measured using the same apparatus and methodology employed pre-race. Participants were instructed to avoid drinking from the finish line until the post-race weighing and an experimenter assured compliance. The body mass change attained during the race was calculated as a per cent reduction in body weight (pre-to post-race). Although the post-race body mass measurement included the sweat trapped in the clothing, this represents an error lower than 10% for the calculation of true hydration status (Cheuvront, Haymes, & Sawka, 2002). After that, participants performed two CMJs and the handgrip strength test, as previously described. Participants then rested for 5 min and a venous blood sample was obtained. The rate of perceived exertion over the course of the race was measured immediately postrace using a standard 6- to 20-point scale (Neely, Ljunggren, Sylvén, & Borg, 1992), and lower-leg muscle soreness was self-rated within 3 min of the end of the race using a 0- to 10-point scale (Ali, Caine, & Snow, 2007). After that, participants were provided with fluid (water and sports drinks) and finished their participation in the study. Blood samples A portion of each whole blood sample was introduced into a blood glucose analyser (Accu-chek, Spain) and glucose concentration was determined. The remaining blood was allowed to clot in serumseparating tubes (BD Vacutainer® Rapid Serum Tube, Spain) and then serum was separated by centrifugation (10 min at 5000 g) and frozen at −80ºC within the following 10 min. Forty-eight hours after the end of the race, the serum portion was analysed for sodium, potassium and chloride concentrations (Nova 16, NovaBiomedical, Spain). In addition, myoglobin, creatine kinase (CK) and lactate dehydrogenase (LDH) concentrations were measured as blood markers of muscle damage (AU5400, Beckman Coulter, US). Statistical analysis Data are presented as mean ± s and the significance level was set at P < 0.05. Normality was tested with the Shapiro–Wilk test with all the variables presenting a normal distribution. Changes in the variables from
pre- to post-race were analysed with Student’s t-tests for paired samples. For each pre- to post-race difference found in this study, we have calculated the effect size (ES) proposed by Cohen and 95% confidence interval. We used Pearson’s correlation to assess the association between two variables. In addition, we established two groups of participants according to their time in the competition, in order to compare the physiological responses of different performance groups. One group included 15 triathletes with a race time of less than 300 min (faster triathletes) and the other group included 15 triathletes with a race time of over 315 min (slower triathletes). Four participants (with race times between 300 and 315 min) were not included in the analysis per groups. Comparisons between these groups were performed with Student’s t-tests for unpaired samples while the ES and 95% confidence interval were calculated for the significant differences between groups. This statistical analysis was performed using the SPSS v.20 software package (SPSS Inc., Chicago, IL, USA). Results Triathlon race time and leg times The mean time taken to complete the half-ironman triathlon was 315 ± 40 min, with a range between 256 and 455 min. The time recorded for the swimming leg was 35 ± 4 min and represented only 11 ± 1% of the total time taken during the race. The cycling leg was completed in 153 ± 20 min and represented 49 ± 2% of the triathlon time, while the running leg (119 ± 20 min) represented 40 ± 3% of the race time. The triathlon race time was significantly related to cycling speed (r = −0.94; P < 0.001), running speed (r = −0.91; P < 0.001) and swimming speed (r = −0.53; P = 0.001), as shown in Figure 1. Body mass change and core temperature After the race, body mass decreased from 73.6 ± 6.4 to 70.9 ± 6.4 kg (95% CI = 2.18/3.03; ES, 0.35; P < 0.001) representing a mean body mass change of −3.8 ± 1.6%. Fifty per cent of the triathletes reduced their body mass by less than 4%, while the highest reduction in body mass was 6.2%. Only one triathlete of our study sample increased his pre-race body mass (from 73.5 to 74.0 kg) although this increase represented only 0.7%. The body mass change attained during the race was positively related to race time (r = 0.64; P < 0.001; Figure 2). In addition, body mass change was negatively related to cycling (r = −0.71; P < 0.001) and running velocities (r = −0.51; P = 0.003). Core temperature before the race was 37.5 ± 0.6ºC, and it increased to
Race time during a triathlon in the heat
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P = 0.019) and running speeds (r = 0.40; P = 0.023). Post-race core temperature was also negatively correlated with body mass change (r = −0.43; P = 0.015).
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Countermovement jump height and handgrip strength Before the race, mean CMJ height was 30.1 ± 4.4 cm and mean power output during the concentric phase of the jump was 1828 ± 360 W. After the race, CMJ height (27.5 ± 5.6 cm; 95% CI = 0.54/5.65; ES, 0.43; P < 0.001) and jump power output (1662 ± 395 W; 95% CI = 64.6/267; ES, 0.42; P < 0.001) were significantly reduced. The time recorded for the race correlated positively with the decrease in jump height (r = 0.38; P = 0.043) and the decrease in jump power output (r = 0.38; P = 0.045). Handgrip maximal strength production in the dominant hand was not different from pre-race (432 ± 79 N) to post-race (428 ± 81 N; 95% CI = −1.45/2.14; ES, 0.04; P = 0.70), and in the non-dominant hand it was reduced from pre-race (424 ± 66 N) to post-race (405 ± 80 N; 95% CI = 0.51/3.45; ES, 0.25; P = 0.01). The changes in handgrip strength were not correlated with race time.
Figure 1. Relationship between the total race time in a halfironman triathlon and the velocities during swimming (1.9 km), cycling (75 km) and running (21 km) legs. Each data point represents a participant in this investigation.
Blood responses Pre and post-race values for the blood and serum variables are shown in Table I. Blood osmolality and blood glucose concentration were significantly increased from pre-to-post-race (P < 0.001). Race time was negatively correlated to post-exercise blood serum osmolality (r = −0.37; P = 0.031), but race time was not correlated to blood glucose concentration. Serum sodium and calcium concentrations were significantly higher after the race (Table I; P < 0.001), but potassium and chloride concentrations remained unchanged after the race. Post-race serum sodium and chloride concentrations were negatively correlated with race time (r = −0.66; P < 0.001 and r = −0.35; P = 0.049) and body mass change (r = −0.66; P < 0.001 and r = −0.46; P = 0.009; Figure 3). Finally, the concentrations of
Figure 2. Relationship between the total race time in a half-ironman triathlon and body mass change and core temperature attained at the end of the race. Each data point represents a participant in this investigation.
38.8 ± 0.7ºC at the end of the race (95% CI = −1.44/−0.85; ES, 1.66; P < 0.001). The core temperature increase (1.3 ± 0.7ºC) was variable with changes of between 0.5ºC to 3.4ºC. Post-race core temperature was negatively correlated with total race time (r = −0.47; P = 0.007; Figure 2) and it was positively correlated with cycling (r = 0.41;
Table I. Blood responses before (pre) and after (post) a half-ironman triathlon race. Data are mean ± s for 34 triathletes. Variable (units) Blood osmolality (mOsm · kg−1) Glucose (mg · dL−1) Sodium (mmol · L−1) Potassium (mmol · L−1) Chloride (mmol · L1) Calcium (mmol · L−1) Myoglobin (µg · L−1) Creatine kinase (U · L−1) Lactate dehydrogenase (U · L−1)
Pre 291.1 114.2 140.6 4.6 102.5 9.5 32.9 169.3 318.5
± ± ± ± ± ± ± ± ±
Post 4.7 11.4 1.5 0.4 1.6 0.5 13.9 86.2 56.2
301.8 128.5 143.0 4.6 103.2 10.3 654.8 564.5 479.0
± ± ± ± ± ± ± ± ±
6.0 22.6 2.1 0.3 2.1 0.5 451.4 428.9 78.6
Δ (%)
Effect size
95% CI
P-value
3.5 10.8 1.7 0.5 0.7 8.7 2020 244 51.3
1.88 0.63 1.14 0.01 0.23 1.77 1.38 0.89 2.04
−12.4/−7.6 −24.0/−5.2 −3.33/−1.44 −8.74/4.57 −1.77/0.36 −23.8/−2.22 −778.8/−465.1 −536.2/−254.2 −175.5/−145.6
