JOURNAL OF SPORTS SCIENCE & MEDICINE |
Research article |
ENERGY EXPENDITURE AND INTENSITY OF PHYSICAL ACTIVITY IN SOCCER REFEREES DURING MATCH-PLAY | |||||||||
Alberto Inácio da Silva1, Luiz Cláudio Fernandes2 and Ricardo Fernandez2 | |||||||||
1Physical Education Department, State University of Ponta Grossa, UEPG, Paraná, Brasil. 2Physiology Department, Biological Science Building, Federal University of Paraná (UFPR), Paraná, Brasil | |||||||||
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© Journal of Sports Science and Medicine (2008) 7, 327 - 334 Search Google Scholar for Citing Articles | |||||||||
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ABSTRACT | |||||||||||||
The aim of this study was to determine the caloric expenditure and the intensity of physical activities performed by official soccer referees during a match expressed in Metabolic Equivalent (METs). The physical activity of referees accredited by CBF (Brazilian Confederation of Soccer) was video-recorded during twenty-nine official games of Paraná Championship (Brasil), Series A and B of the 2005/2006. Computerized video analysis was used to determine the time spent in 6 locomotor activities (standing still, walking, jogging, backwards running, running and sprint). The frequency and duration of each activity were recorded and these data were utilized to calculate the distance covered by the referee. Energy expenditure values were estimated, utilizing specific equations, from the time players spent in each motor activity. The referees observed in this study had a mean age of 38.9 ± 3.8 years, body mass of 86.1 ± 7.1 kg, stature of 1.80 ± 0.07 m and a body mass index of 26.5 ± 0.6 kg·m-2. During match-play, referees covered an average distance of 9155.4 ± 70.3 meters (8411 - 9765), with a mean energy expenditure of 734.7 ± 65 kcal. This energy expenditure was significantly reduced in the second half: 359.9 ± 6.3 vs 374.7 ± 6.6 kcal (p = 0.006), and averaged to be moderate energy intensity (5 METs) with predominant utilization of the aerobic energy system. In total, during 67% of match-play the intensity was equal or lower than 3.8 METs and in 33% it was higher than 9.8 METs. The pattern of movement observed in the present study confirms that soccer refereeing may be considered as a highly intermittent exercise mode. The high to low-intensity activity ratio may be defined as 1:7.1. In conclusion, referees officiating in professional soccer matches in Brazil should perform a physical conditioning regime that provides the stamina required at this level and consume appropriate and adequate nutrition to meet the energetic demands for match-play. Key words: Motion-analysis, referee, football, METs, oxygen consumption. |
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INTRODUCTION | |||||||||||||
The energy needs for an individual varies according to their age, sex and the physical activities that perform during the day. Healthy male individuals present an average energy demand of 2900kcal·day-1 (National Research Council, 1996); however, a professional soccer player's energy demand oscillates from 3500 to 4300 kcal/day (Clark, 1994; Bangsbo et al., 2006; Ebine et al., 2002; Rico-Sanz, 1998a). It should be acknowledged that these values for soccer players vary from week to week, and energy expenditure depends on the frequency and intensity of training sessions, exercises and matches. In soccer, players and referees require a diet with a high percentage of carbohydrates (Rico-Sanz et al., 1998). In order to elaborate a diet that sufficiently restores the athlete's energy expenditure during training and/or competition, the first step would be to measure energy expenditure during activity. One way is to determine the demand in terms of VO2 during competition (Rico-Sanz et al., 1998). There have been numerous studies that have investigated the soccer players' maximum oxygen consumption (Bangsbo et al., 1991; Bangsbo and Lindovist, 1992; Ekblom, 1993; Tumilty, 1993). Determination of VO2 demand during the competition allows the calculation of athlete's energy expenditure with reasonable precision (Coast and Welch, 1985; Daniels, 1985; Daniels and Daniels, 1992). Since, on average, 5 kcal is produced for each liter of consumed oxygen, it is possible to express calorific expenditure during the match in kcal. The intensity of soccer referee's physical activities during official matches has been estimated by the recording of heart rate (Krustrup and Bangsbo, 2001; Weston and Brewer, 2002). The average match heart rate found in these studies attains 85% of referee's maximal heart rate. D`Ottavio and Castagna (2002) directly measured VO2 responses using a portable light-weight gas analyzer in elite-level soccer referees officiating during a friendly match. They found that over the observed match period (first half) the referees attained 68% of the individual VO2max, a value lower than that reported in those studies when VO2 was estimated through heart rate. Another means of estimating energy expenditure during physical activity involves the reporting in terms of Metabolic Equivalent (METs). A MET represents the resting VO2 and is defined as the energy expenditure (VO2) informed as ml·kg-1·min-1 or L·min-1 in rest conditions (Ainsworth et al., 1993). Therefore, the energy expenditure of a physical activity can be expressed in multiples of rest VO2, which simplifies the measuring of energy needs during the exercise. According to Wilmore and Costill, 2005, all physical activities can be classified by the intensity according to their needs of oxygen. Therefore, through METs estimations, it is possible to classify the intensity of different physical activities (Ainsworth et al., 1993). Recent studies have demonstrated that refereeing is an exercise model mainly related to the aerobic pathway (Catterall et al., 1993; Johnston and McNaughton, 1994; Da Silva and Rodriguez-Añez, 2001; D'Ottavio and Castagna, 2001; Krustrup and Bangsbo, 2001). However, it is also useful to convert this into a calorific expenditure and the intensity of referee's physical activities performed during a match expressed in METs to assist with conditioning and nutritional programmes. Therefore, the main objective of this study was to evaluate these parameters in professional soccer referees in Brazil in order to provide advice for nutritional strategies and interventions to restore the referee's energy during a match. |
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METHODS | |||||||||||||
Subjects Statistical analysis |
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RESULTS | |||||||||||||
The referees observed in this study had a mean age of 38.9 ± 3.8years, body mass of 86.1 ± 7.1kg, a stature of 1.80 ± 7 m and a body mass index of 26.5 ± 0.6 kg·m-2. These characteristics were similar to other groups of official soccer referees observed in previous studies (Castagna et al., 2004; Krustrup and Bangsbo, 2001; Rebelo et al., 2002). The environmental conditions during the matches were considered to be warm with an average temperature of 23.1 ± 0.54 oC and humidity of 67.3 ± 3.5%. |
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DISCUSSION | |||||||||||||
In the present study, it was observed that during officials matches soccer referees perform physical aerobic activities of low and moderate intensity, and present a significant decline in energy expenditure between the first and second half. Other studies involving soccer referees have also confirmed that the physical activity of referees during match-play predominantly involves the utilization of energy originating from aerobic metabolism (Asami et al., 1988; Castagna et al., 2004; Catterall et al., 1993; Da Silva and Rodriguez-Añez, 1999; Johnston and McNaughton, 1994; Krustrup and Bangsbo, 2001). |
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ACKNOWLEDGMENTS | |
Luiz C. Fernandes was supported by a grant of the Conselho Nacional de Pesquisas (CNPq), Brazil. |
AUTHORS BIOGRAPHY | |
Alberto Inácio DA SILVA Employment: Asistant professor. Physical Education Department, State University of Ponta Grossa - UEPG, Paraná, Brasil. Degree: PhD. Research interests: Physical performance and training of soccer referees. E-mail: albertoinacio@bol.com.br | |
Luiz Cláudio FERNANDES Employment: Associated Professor. Physiology Department, Biological Science Building, Federal University of Paraná (UFPR), Paraná, Brasil. Degree: PhD. Research interests: Effect of fish oil supplementation and physical activity on metabolism of normal and cachectic subjects. E-mail: lcfer@ufpr.br | |
Ricardo Fernandez PEREZ Employment: Associated Professor. Physiology Department, Biological Science Building, Federal University of Paraná (UFPR), Paraná, Brasil. Degree: PhD, MD. Research interests: Regulation of renal proton transport. Physical performance of soccer referees. E-mail: ricfer@ufpr.br | |