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Journal of Sports Sciences Publication details, including instructions for authors and subscription information: http://www.tandfonline.com/loi/rjsp20
Recording soccer players’ heart rates during matches a
Araz Ali & Martin Farrally
a
a
Department of Physical Education, University of St Andrews, Fife, KY16 9DY, UK Published online: 14 Nov 2007.
To cite this article: Araz Ali & Martin Farrally (1991) Recording soccer players’ heart rates during matches, Journal of Sports Sciences, 9:2, 183-189, DOI: 10.1080/02640419108729879 To link to this article: http://dx.doi.org/10.1080/02640419108729879
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, sublicensing, 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, 1991, 9, 183-189
Recording soccer players' heart rates during matches ARAZ ALI and MARTIN FARRALLY Department of Physical Education, University of St Andrews, Fife KY16 9DY, UK
Downloaded by [Moskow State Univ Bibliote] at 09:09 25 July 2013
Accepted 9 April 1990
Abstract
The aim of this study was to examine the possibility of obtaining information about the heart rate and physiological load imposed on soccer players during a game. The study was conducted on 27 soccer players, 9 each from semi-professional, university and recreational soccer teams. Players from all positions (attack, midfield and defence) were selected for the study. Each subject's heart rate was monitored during a match using a short-range radio telemetry (Sport TesterTM PE 3000 ), and was sampled at 5-s intervals. The results indicate that it is possible to monitor successfully the heart rate of players with such equipment. The mean heart rate and standard deviation for each player during match play were: semiprofessional players (172 ± 12, 176 ± 9 and 166 ± 15 for forwards, midfielders and defenders, respectively); university players (171 ± 13, 173 ± 10 and 156 ± 13 for forwards, midfielders and defenders, respectively); and recreational players (173 ± 13, 170 ± 12 and 162 ± 13 for forwards, midfielders and defenders, respectively). Analysis by playing position revealed that midfield and forward players has a greater mean heart rate during a game than defensive players. To examine the suitability and accuracy of the two methods of obtaining objective data on heart rate, comparisons were made between the SportTesterTMPE 3000 and a standard electrocardiograph (ECG) telemetry technique. The results show that both techniques produce similar results; the former was the more convenient. In the light of the experiences gained in this study, the researchers would recommend the use of shortrange radio telemetry (SportTesterTMPE 3000 system) to accumulate heart rate data in match situations. Further studies should be conducted, involving a larger number of subjects of all standards of the game, including juvenile players, to give a better indication of the physiological demands of the game at all levels. Keywords: Radio telemetry, players' heart rates, soccer.
Introduction In earlier studies, it was only possible to record heart rate before and after a game. It has been stated by several researchers that heart rate measured immediately after a game does not reflect the mean heart rate during a game (McArdle et al., 1969; Ramsey et al., 1970). Several researchers have used telemetered heart rate recording for their investigations, mostly for individual sports: badminton (Agnevik, 1970a), tennis (Lundin, 1973; Kozar and Hunsicker, 1963) and gymnastic routines (Faria and Phillips, 1970; Noble, 1975). 0264-0414/91 $03.00 + .12 © 1991 E. & F.N. Spon Ltd.
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Heart rate has also been recorded in team sports. It should be mentioned that these results were based on observations of only one player during a single game: basketball (McArdle et al., 1971; Ramsey et al., 1970), handball (Kozar and Hunsicker, 1963), American football (Gleim et al., 1981), ice hockey (Green et ai, 1976), baseball (Hanson, 1967) and soccer (Reilly and Thomas, 1979; Reilly, 1986; Kohno et al., 1988; Rohde and Espersen, 1988; Hollmann and Hettinger, 1976; Nowacki et al., 1988; Deroanne et al., 1972; Agnevik, 1970b; Van Gool et al., 1983). Most of the research mentioned above has provided data on the heart rates of the athletes during training or during friendly matches. In the case of soccer players, they were monitored for a short period of time using a telemetry system in each half of a game and the results extrapolated to the entire game. Doubt must be raised over the practicality of using telemetry equipment during soccer matches, as it has several disadvantages for recording the heart rates of soccer players: 1. Malfunction of the apparatus caused by jumping or tackling, or by touching the electrodes. 2. Until recently, transmitters were large and heavy, causing problems during sprinting, cruising, jumping and tackling. 3. Electrodes have to be attached to the surface of the player but often fall off when the subject starts to sweat. The main aim of this research was to examine the possibilities of obtaining information about the heart rates and physiological loads imposed on soccer players during a match situation using short-range radio telemetry (Sport Tester® PE 3 0 0 0 ). The main questions that the study addressed were as follows: 1. Can the Sport Tester® P E 3 0 0 0 measure the heart rate of a soccer player during a match situation and, if so, what frequency of sampling is suitable for obtaining valuable information about the heart rate of the player? 2. Can the Sport Tester® P E 3 0 0 0 measure the heart rate of more than one soccer player during a game? 3. Can the receiver be installed safely and practically for recording heart rate accurately during a match situation? 4. Can the Sport Tester® PE 3 0 0 0 measure the heart rate of association football players as accurately as taking beat-by-beat measurements? The physiological demands on soccer players have been the subject of much speculation but little investigation. The use of the Sport Tester® PE 3 0 0 0 system, if successful, could provide a valuable means of acquiring data from live matches.
Methods Subjects The subjects in this study consisted of 27 soccer players. Nine were semi-professional soccer players, nine players came from a university first team and the other nine were from a recreational team (Table 1). All positions (attack, midfield and defence) were selected for the study.
Soccer players' heart rates
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Table 1. Mean ( + S.D.) of physical characteristics for semi-professional, university and recreational players (n = 27) studied for an entire game (n = 9 for each group) Age (years) Height (cm) Weight (kg)
Semi-professional
University
Recreational
25.0 + 3.0 179.5 + 3.8 72.1 + 3.6
21.0 + 2.8 179.1 + 3.7 72.1+2.5
27.0±4.0 177.8 + 3.5 75.4+4.2
Apparatus
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The Sport Tester® PE 3 0 0 0 heart rate meter measures and records heart rates, and thereby whole body exertion. Being truly wireless, light and portable, it is easy to use even under difficult conditions (Rohde and Espersen, 1988). It consists of a transmitter worn on a chest belt containing electrodes, and a receiver. The receiver unit is equipped with a memory that can be used for recording both heart rate and time information provided it is located within about 1 m of the transmitter. The heart rate of a subject can be picked up and stored in the memory every 5, 15 or 60 s. With a 5-s interval, the maximum recording time is about 80 min. Using the 15-s interval, the maximum recording period is about 4 h. Heart rate monitoring
In order to determine which sampling frequency is most suitable for obtaining reliable information about the heart rates of players, a subject was randomly selected before a game started and asked to wear the Sport Tester® PE 3 0 0 0 equipment with three receivers. The receivers were installed and set up for recording the pulse rate at 5-, 15- and 60-s intervals. After the game, data obtained from the receivers were scrutinized and it was discovered that there were dissimilarities between all of them, although the data from the 5and 15-s sampling frequencies were, as expected, more alike. The sampling frequency of the 5-s data gave clearer and more detailed information of the heart rate compared with the other two sets of data. The advantages of using the 5-s sampling frequency are: 1. Movement patterns change frequently every 5 s or less in a game of football. There is certainly no movement, on average, that lasts for 15 s or more (Reilly and Thomas, 1976; Withers et al, 1982). 2. More data can be collected with a sampling frequency of 5 s than with other frequencies. 3. The reflection of the rapid changes in pace of movements can be seen on the heart rate. If the heart rate is recorded at 5-s intervals, it will be possible to detect from the heart rate almost every change in movement. 4. With a sampling frequency of 15 s, one may only get traces of the heart rate corresponding to every third or fourth movement.
It should be noted that the only problem with sampling at 5-s intervals is the limitation of the receiver's memory which, as mentioned earlier, can record for a maximum of 80 min, whereas a game of soccer lasts for 90 min. This can be overcome by changing the receiver at half time. To examine whether it is possible to study the heart rate of more than one player during a match using this equipment, three players wore the equipment during a match and the
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receivers were set up at a sampling frequency of 5-s intervals. The subjects were not aware of the purpose of the experiment because it was important to let them behave as they would in an ordinary match. After the match, the data were examined and it was found that the heart rate readings when the test players were close together were contaminated. Therefore, it is not possible to monitor the heart rate of more than one player at a time with such equipment. To determine the most suitable and practical way of installing the equipment, a subject was randomly selected and wore two receivers, one receiver being fixed around his wrist and another kept inside the small pocket of his shorts. The receivers' data were obtained and it was found that both sets of data were identical. To test whether there are any differences between monitoring heart rate using the Sport Tester® PE 3000 and a standard electrocardiograph (ECG) telemetry technique, a protocol was designed whereby both monitoring systems were operating during simulated movements that are often employed by soccer players during a game. These movements were walking, jogging, cruising, sprinting and standing still, and their durations were based on an analysis of video-recordings of soccer players during competitive matches. One soccer player acted as a subject. Surface electrodes were mounted on his chest along with a transmitter to send electrocardiograph signals from the subject to a telemetry receiver and recorder (Hewlett Packard). The subject also wore the Sport Tester® PE 3000 equipment. The protocol consisted of walking for 9 s, 4 s of cruising, 5 s ofjogging, 3 s of sprinting and 6 s of standing still; it was repeated continuously 12 times. For the purpose of the analysis, successive 5-s heart rates were printed out by the interface unit of the Sport Tester® PE 3000 and compared to the corresponding instantaneous 5-s heart beats determined from the telemetered cardiograph. A sample is shown in Table 2. Table 2. Heart rates recorded simultaneously by the Sport Tester® PE 3000 and a standard electrocardiograph (ECG) telemetry technique Sport Tester® 106 125 131 139 133 121 135 125 143 154 146 129 139 142 156 159 133 139 144
ECG
Sport Tester®
ECG
106 125 131 139 133 122 135 125 144 155 148 131 139 143 157 160 133 139 146
136 145 168 174 162 147 139 133 158 177 166 137 139 149 169 182 173 168 159
136 145 168 175 163 147 138 133 159 178 166 138 139 150 169 183 173 168 158
Soccer players' heart rates
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Table 2 shows that there are few differences between recordings of heart rate using ECG and the Sport Tester® P E 3 0 0 0 . It should be noted that the differences were never greater than 2 beats min ~ 1 . The Sport Tester® PE 3 0 0 0 was more practical than the ECG for recording the heart rate of soccer players. The ECG had several disadvantages, some of which have been mentioned previously. It should be noted that no statistical analysis was carried out on the results of the heart rates obtained for two reasons. First, the main aim of this research was to examine the possibilities of obtaining objective information about the heart rate of soccer players. Secondly, the number of subjects participating was too small to conduct a proper statistical analysis (i.e. nine each from semi-professional, university and recreational soccer teams).
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Results and discussion The results indicated that it is possible to monitor successfully the heart rate of a player with such equipment. The mean heart rate and standard deviation for each semi-professional, university and recreational player during play are shown in Tables 3 and 4. Table 3. Mean heart rate (±S.D.) for semi-professional, university and recreational players for an entire game (n = 3 in each group) Forward Midfield Defender
Semi-professional
University
Recreational
173 + 12 176 + 9 166±15
171 ±13 173 + 10 156+13
173 ±13 170+12 162+13
Table 4. Mean heart rate (±S.D.) for semi-professional, university and recreational players during the first and second halves of a game (n = 3 for each group) Semi-professional
Forward Midfield Defender
University
Recreational
1st half
2nd half
1st half
2nd half
1st half
2nd half
174+13 178±9 170+15
172+12 174 + 9 162±12
172+13 175±10 160+14
170+12 171 + 10 152 + 11
174 ±13 172+13 163 ±14
172+13 169+12 159+13
The greatest amount of data regarding physiological attributes of athletes appears to be on endurance runners; there is only a small amount available for soccer players. This might stem from the strong focus of exercise physiologists on cardiovascular and metabolic functions, for which the monitoring of soccer players is more difficult. From the results shown in Table 3, the following observations can be made: 1. There are no differences between the forward players of all three standards. 2. Defensive players are under the least physiological stress. 3. There are differences between the semi-professional defence and midfield players
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compared with the corresponding university and recreational players. This indicates clearly that at a higher standard of game, defensive and midfield players are under greater physiological stress, perhaps indicating that they contribute more to the game than defensive and midfield players at a lower standard. 4. The mean heart rate obtained for all three standards of player was about 170 beats min" 1 during the match. This indicates how rigorously the game is played even at a recreational standard.
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From the results shown in Table 4, it is clear that for all three standards of the game the heart rate of the players decreased during the second half. Two reasons for this may be: 1. Fatigue. Soccer players may contribute much more effort to the game in the first half, and the longer the game goes on the more fatigued they become and the less contribution they make. 2. Results of the game. For example, on the one hand, when a team is winning by 3 or 4 goals, the players may be less enthusiastic about the match and contribute less to the game. On the other hand, when a team is losing by 3 or 4 goals, the players may be less interested because they think that they cannot win. Doubt must be raised over the practicality of using the telemetry equipment during soccer matches, as there are obvious weak points. For example, Franks (1983) conducted a study on the heart rates of the Canadian Olympic soccer team in laboratory and match situations. He reported that several problems were encountered while studying the players' heart rates during a match situation that were not encountered during laboratory tests. The electrodes moved extensively during competition and the connection between the electrodes and the recording device worked loose. The machine itself is rather large and bulky and is not easy to wear during a game. These problems have now been resolved and a more compact device is being developed to measure and record the heart rates of soccer players during a game. It should be noted that more studies concerned with the heart rates of soccer players have been reported. The results have not been discussed because the playing time was not for a complete game of 90 min (Smodlaka, 1979) or because it was not an 11-a-side game (Kohno et al, 1988; Rohde and Espersen, 1988). In summary, it is common to use heart rate as a measure of physical workload. Technically, the equipment used by previous researchers was found to be impractical, and inconvenient for the subject. In close contact sports such as soccer, it is important that the equipment is small, light and not liable to cause any danger to the subject. From the results of this study, it is clear that short-range radio telemetry (such as use of the Sport Tester® PE 3000 , or similar equipment) permits realistic measurement of the physiological load on soccer players in live matches. It is recommended that studies should be conducted, involving a larger number of subjects of all standards of the game, including juvenile players, to give a better indication of the physiological demands of the game at all levels.
References Agnevik, G. (1970a) Badminton. Idrottsfysiologi, Report no. 8. Stockholm: Trygg-Hansa. Agnevik, G. (1970b) Fotboll. Idrottsfysiologi, Report no. 7. Stockholm: Trygg-Hansa. Deroanne, R., Pirnay, F., Servais, J.C. and Petit, J.P. (1972) Telemetry and ergometry associated to the
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measure of oxygen consumption during sports events. In Biotelemetry (edited by H.P. Kimmich and J.A. Vos), pp. 101-110. Leiden: Meander. Faria, I.E. and Phillips, A. (1970) A study of telemetered cardiac response of young boys and girls during gymnastic participation. Journal of Sports Medicine and Physical Fitness 10, 145-50. Franks, I.M. (1983) Training centre report to the Canadian soccer association. Centre for Sports Analysis, University of British Columbia, Vancouver. Gleim, G.W., Witman, P.A. and Nicholas, J.A. (1981) Indirect assessment of cardiovascular "demands" using telemetry on professional football players. American Journal of Sports Medicine 9, 178-83. Green, H., Bishop, P., Houston, M., McKillop, R., Norman, R. and Stothart, P. (1976) Time-motion and physiological assessments of ice hockey performance. Journal of Applied Physiology 40, 159. Hanson, D.L. (1967) Cardiac response to participation in Little League baseball competition as determined by telemetry. Research Quarterly 38, 384-8. Hollmann, W. and Hettinger, T. (1976) Sportmedizin-, Arbeits-, und Trainings-grundlagen. Stuttgart: Schattauer. Kohno, T., O'Hata, N., Monta, H., Shirahata, T., Onodera, S. and Sato, M. (1988) Can senior citizens play soccer safely? In Science and Football (edited by T. Reilly, A. Lees, K. Davids and W.J. Murphy), pp. 230-36. London: E. and F.N. Spon. Kozar, A.J. and Hunsicker, P. (1963) A study of telemetered heart rate during sports participation of young adult men. Journal of Sports Medicine and Physical Fitness 3, 1-5. Lundin, A. (1973) Bordtennis. Idrottsfysiologi, Report no. 12. Stockholm: Trygg-Hansa. McArdle, W.D., Zwiren, L. and Magel, J.R. (1969) Validity of the postexercise heart rate as a means of estimating heart rate during work of varying intensities. Research Quarterly 40, 523-8. McArdle, W.D., Magel, J.R. and Kyvallos, L.C. (1971) Aerobic capacity, heart rate and estimated energy cost during women's competitive basketball. Research Quarterly 42, 178-86. Noble, L. (1975) Heart rate and predicted VO2 during women's competitive gymnastic routines. Journal of Sports Medicine and Physical Fitness 15, 151-7. Nowacki, P.E., Cai, D.Y., Buhl. C. and Krümmelbein, U. (1988) Biological performance of German soccer players (professionals and juniors) tested by special ergometry and treadmill methods. In Science and Football (edited by T. Reilly, A. Lees, K. Davids and W.J. Murphy), pp. 145-57. London: E. and F.N. Spon. Ramsey, J.D., Ayoub, M.M., Dudek, R.A. and Edgar, H.S. (1970) Heart recovery during a college basketball game. Research Quarterly 41, 527-35. Reilly, T. (1986) Fundamental studies in soccer. In Beiträge zur Sportspielforschung: Sportwissenschaft und sportpracis (edited by R. Andresen), pp. 114-20. Hamburg: Verlag Ingrid Czwalina. Reilly, T. and Thomas, V. (1976) A motion analysis of work-rate in different positional roles in professional football match play. Journal of Human Movement Studies 2, 87-97. Reilly, T. and Thomas, V. (1979) Estimated daily energy expenditures of professional association footballers. Ergonomics 22, 541-8. Rohde, H.C. and Espersen, T. (1988) The work intensity during soccer training and match play. In Science and Football (edited by T. Reilly, A. Lees, K. Davids and W.J. Murphy), pp. 68-75. London: E. and F.N. Spon. Smodlaka, V.N. (1979) Cardiovascular aspects of soccer. Physician and Sportsmedicine 6, 148-53. Van Gool, D., Van Gerven, D. and Boutmans, J. (1983) Heart rate recorded during a soccer game: A new methodology. Journal of Sports Sciences 1, 154-5. Withers, R. T., Maricic, Z., Wasilewski, S. and Kelly, L. (1982) Match analysis of Australian professional soccer players. Journal of Human Movement Studies 4, 159-76.
Journal of Sports Sciences Publication details, including instructions for authors and subscription information: http://www.tandfonline.com/loi/rjsp20
Recording soccer players’ heart rates during matches a
Araz Ali & Martin Farrally
a
a
Department of Physical Education, University of St Andrews, Fife, KY16 9DY, UK Published online: 14 Nov 2007.
To cite this article: Araz Ali & Martin Farrally (1991) Recording soccer players’ heart rates during matches, Journal of Sports Sciences, 9:2, 183-189, DOI: 10.1080/02640419108729879 To link to this article: http://dx.doi.org/10.1080/02640419108729879
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, sublicensing, 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, 1991, 9, 183-189
Recording soccer players' heart rates during matches ARAZ ALI and MARTIN FARRALLY Department of Physical Education, University of St Andrews, Fife KY16 9DY, UK
Downloaded by [Moskow State Univ Bibliote] at 09:09 25 July 2013
Accepted 9 April 1990
Abstract
The aim of this study was to examine the possibility of obtaining information about the heart rate and physiological load imposed on soccer players during a game. The study was conducted on 27 soccer players, 9 each from semi-professional, university and recreational soccer teams. Players from all positions (attack, midfield and defence) were selected for the study. Each subject's heart rate was monitored during a match using a short-range radio telemetry (Sport TesterTM PE 3000 ), and was sampled at 5-s intervals. The results indicate that it is possible to monitor successfully the heart rate of players with such equipment. The mean heart rate and standard deviation for each player during match play were: semiprofessional players (172 ± 12, 176 ± 9 and 166 ± 15 for forwards, midfielders and defenders, respectively); university players (171 ± 13, 173 ± 10 and 156 ± 13 for forwards, midfielders and defenders, respectively); and recreational players (173 ± 13, 170 ± 12 and 162 ± 13 for forwards, midfielders and defenders, respectively). Analysis by playing position revealed that midfield and forward players has a greater mean heart rate during a game than defensive players. To examine the suitability and accuracy of the two methods of obtaining objective data on heart rate, comparisons were made between the SportTesterTMPE 3000 and a standard electrocardiograph (ECG) telemetry technique. The results show that both techniques produce similar results; the former was the more convenient. In the light of the experiences gained in this study, the researchers would recommend the use of shortrange radio telemetry (SportTesterTMPE 3000 system) to accumulate heart rate data in match situations. Further studies should be conducted, involving a larger number of subjects of all standards of the game, including juvenile players, to give a better indication of the physiological demands of the game at all levels. Keywords: Radio telemetry, players' heart rates, soccer.
Introduction In earlier studies, it was only possible to record heart rate before and after a game. It has been stated by several researchers that heart rate measured immediately after a game does not reflect the mean heart rate during a game (McArdle et al., 1969; Ramsey et al., 1970). Several researchers have used telemetered heart rate recording for their investigations, mostly for individual sports: badminton (Agnevik, 1970a), tennis (Lundin, 1973; Kozar and Hunsicker, 1963) and gymnastic routines (Faria and Phillips, 1970; Noble, 1975). 0264-0414/91 $03.00 + .12 © 1991 E. & F.N. Spon Ltd.
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Heart rate has also been recorded in team sports. It should be mentioned that these results were based on observations of only one player during a single game: basketball (McArdle et al., 1971; Ramsey et al., 1970), handball (Kozar and Hunsicker, 1963), American football (Gleim et al., 1981), ice hockey (Green et ai, 1976), baseball (Hanson, 1967) and soccer (Reilly and Thomas, 1979; Reilly, 1986; Kohno et al., 1988; Rohde and Espersen, 1988; Hollmann and Hettinger, 1976; Nowacki et al., 1988; Deroanne et al., 1972; Agnevik, 1970b; Van Gool et al., 1983). Most of the research mentioned above has provided data on the heart rates of the athletes during training or during friendly matches. In the case of soccer players, they were monitored for a short period of time using a telemetry system in each half of a game and the results extrapolated to the entire game. Doubt must be raised over the practicality of using telemetry equipment during soccer matches, as it has several disadvantages for recording the heart rates of soccer players: 1. Malfunction of the apparatus caused by jumping or tackling, or by touching the electrodes. 2. Until recently, transmitters were large and heavy, causing problems during sprinting, cruising, jumping and tackling. 3. Electrodes have to be attached to the surface of the player but often fall off when the subject starts to sweat. The main aim of this research was to examine the possibilities of obtaining information about the heart rates and physiological loads imposed on soccer players during a match situation using short-range radio telemetry (Sport Tester® PE 3 0 0 0 ). The main questions that the study addressed were as follows: 1. Can the Sport Tester® P E 3 0 0 0 measure the heart rate of a soccer player during a match situation and, if so, what frequency of sampling is suitable for obtaining valuable information about the heart rate of the player? 2. Can the Sport Tester® P E 3 0 0 0 measure the heart rate of more than one soccer player during a game? 3. Can the receiver be installed safely and practically for recording heart rate accurately during a match situation? 4. Can the Sport Tester® PE 3 0 0 0 measure the heart rate of association football players as accurately as taking beat-by-beat measurements? The physiological demands on soccer players have been the subject of much speculation but little investigation. The use of the Sport Tester® PE 3 0 0 0 system, if successful, could provide a valuable means of acquiring data from live matches.
Methods Subjects The subjects in this study consisted of 27 soccer players. Nine were semi-professional soccer players, nine players came from a university first team and the other nine were from a recreational team (Table 1). All positions (attack, midfield and defence) were selected for the study.
Soccer players' heart rates
185
Table 1. Mean ( + S.D.) of physical characteristics for semi-professional, university and recreational players (n = 27) studied for an entire game (n = 9 for each group) Age (years) Height (cm) Weight (kg)
Semi-professional
University
Recreational
25.0 + 3.0 179.5 + 3.8 72.1 + 3.6
21.0 + 2.8 179.1 + 3.7 72.1+2.5
27.0±4.0 177.8 + 3.5 75.4+4.2
Apparatus
Downloaded by [Moskow State Univ Bibliote] at 09:09 25 July 2013
The Sport Tester® PE 3 0 0 0 heart rate meter measures and records heart rates, and thereby whole body exertion. Being truly wireless, light and portable, it is easy to use even under difficult conditions (Rohde and Espersen, 1988). It consists of a transmitter worn on a chest belt containing electrodes, and a receiver. The receiver unit is equipped with a memory that can be used for recording both heart rate and time information provided it is located within about 1 m of the transmitter. The heart rate of a subject can be picked up and stored in the memory every 5, 15 or 60 s. With a 5-s interval, the maximum recording time is about 80 min. Using the 15-s interval, the maximum recording period is about 4 h. Heart rate monitoring
In order to determine which sampling frequency is most suitable for obtaining reliable information about the heart rates of players, a subject was randomly selected before a game started and asked to wear the Sport Tester® PE 3 0 0 0 equipment with three receivers. The receivers were installed and set up for recording the pulse rate at 5-, 15- and 60-s intervals. After the game, data obtained from the receivers were scrutinized and it was discovered that there were dissimilarities between all of them, although the data from the 5and 15-s sampling frequencies were, as expected, more alike. The sampling frequency of the 5-s data gave clearer and more detailed information of the heart rate compared with the other two sets of data. The advantages of using the 5-s sampling frequency are: 1. Movement patterns change frequently every 5 s or less in a game of football. There is certainly no movement, on average, that lasts for 15 s or more (Reilly and Thomas, 1976; Withers et al, 1982). 2. More data can be collected with a sampling frequency of 5 s than with other frequencies. 3. The reflection of the rapid changes in pace of movements can be seen on the heart rate. If the heart rate is recorded at 5-s intervals, it will be possible to detect from the heart rate almost every change in movement. 4. With a sampling frequency of 15 s, one may only get traces of the heart rate corresponding to every third or fourth movement.
It should be noted that the only problem with sampling at 5-s intervals is the limitation of the receiver's memory which, as mentioned earlier, can record for a maximum of 80 min, whereas a game of soccer lasts for 90 min. This can be overcome by changing the receiver at half time. To examine whether it is possible to study the heart rate of more than one player during a match using this equipment, three players wore the equipment during a match and the
Downloaded by [Moskow State Univ Bibliote] at 09:09 25 July 2013
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receivers were set up at a sampling frequency of 5-s intervals. The subjects were not aware of the purpose of the experiment because it was important to let them behave as they would in an ordinary match. After the match, the data were examined and it was found that the heart rate readings when the test players were close together were contaminated. Therefore, it is not possible to monitor the heart rate of more than one player at a time with such equipment. To determine the most suitable and practical way of installing the equipment, a subject was randomly selected and wore two receivers, one receiver being fixed around his wrist and another kept inside the small pocket of his shorts. The receivers' data were obtained and it was found that both sets of data were identical. To test whether there are any differences between monitoring heart rate using the Sport Tester® PE 3000 and a standard electrocardiograph (ECG) telemetry technique, a protocol was designed whereby both monitoring systems were operating during simulated movements that are often employed by soccer players during a game. These movements were walking, jogging, cruising, sprinting and standing still, and their durations were based on an analysis of video-recordings of soccer players during competitive matches. One soccer player acted as a subject. Surface electrodes were mounted on his chest along with a transmitter to send electrocardiograph signals from the subject to a telemetry receiver and recorder (Hewlett Packard). The subject also wore the Sport Tester® PE 3000 equipment. The protocol consisted of walking for 9 s, 4 s of cruising, 5 s ofjogging, 3 s of sprinting and 6 s of standing still; it was repeated continuously 12 times. For the purpose of the analysis, successive 5-s heart rates were printed out by the interface unit of the Sport Tester® PE 3000 and compared to the corresponding instantaneous 5-s heart beats determined from the telemetered cardiograph. A sample is shown in Table 2. Table 2. Heart rates recorded simultaneously by the Sport Tester® PE 3000 and a standard electrocardiograph (ECG) telemetry technique Sport Tester® 106 125 131 139 133 121 135 125 143 154 146 129 139 142 156 159 133 139 144
ECG
Sport Tester®
ECG
106 125 131 139 133 122 135 125 144 155 148 131 139 143 157 160 133 139 146
136 145 168 174 162 147 139 133 158 177 166 137 139 149 169 182 173 168 159
136 145 168 175 163 147 138 133 159 178 166 138 139 150 169 183 173 168 158
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Table 2 shows that there are few differences between recordings of heart rate using ECG and the Sport Tester® P E 3 0 0 0 . It should be noted that the differences were never greater than 2 beats min ~ 1 . The Sport Tester® PE 3 0 0 0 was more practical than the ECG for recording the heart rate of soccer players. The ECG had several disadvantages, some of which have been mentioned previously. It should be noted that no statistical analysis was carried out on the results of the heart rates obtained for two reasons. First, the main aim of this research was to examine the possibilities of obtaining objective information about the heart rate of soccer players. Secondly, the number of subjects participating was too small to conduct a proper statistical analysis (i.e. nine each from semi-professional, university and recreational soccer teams).
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Results and discussion The results indicated that it is possible to monitor successfully the heart rate of a player with such equipment. The mean heart rate and standard deviation for each semi-professional, university and recreational player during play are shown in Tables 3 and 4. Table 3. Mean heart rate (±S.D.) for semi-professional, university and recreational players for an entire game (n = 3 in each group) Forward Midfield Defender
Semi-professional
University
Recreational
173 + 12 176 + 9 166±15
171 ±13 173 + 10 156+13
173 ±13 170+12 162+13
Table 4. Mean heart rate (±S.D.) for semi-professional, university and recreational players during the first and second halves of a game (n = 3 for each group) Semi-professional
Forward Midfield Defender
University
Recreational
1st half
2nd half
1st half
2nd half
1st half
2nd half
174+13 178±9 170+15
172+12 174 + 9 162±12
172+13 175±10 160+14
170+12 171 + 10 152 + 11
174 ±13 172+13 163 ±14
172+13 169+12 159+13
The greatest amount of data regarding physiological attributes of athletes appears to be on endurance runners; there is only a small amount available for soccer players. This might stem from the strong focus of exercise physiologists on cardiovascular and metabolic functions, for which the monitoring of soccer players is more difficult. From the results shown in Table 3, the following observations can be made: 1. There are no differences between the forward players of all three standards. 2. Defensive players are under the least physiological stress. 3. There are differences between the semi-professional defence and midfield players
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compared with the corresponding university and recreational players. This indicates clearly that at a higher standard of game, defensive and midfield players are under greater physiological stress, perhaps indicating that they contribute more to the game than defensive and midfield players at a lower standard. 4. The mean heart rate obtained for all three standards of player was about 170 beats min" 1 during the match. This indicates how rigorously the game is played even at a recreational standard.
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From the results shown in Table 4, it is clear that for all three standards of the game the heart rate of the players decreased during the second half. Two reasons for this may be: 1. Fatigue. Soccer players may contribute much more effort to the game in the first half, and the longer the game goes on the more fatigued they become and the less contribution they make. 2. Results of the game. For example, on the one hand, when a team is winning by 3 or 4 goals, the players may be less enthusiastic about the match and contribute less to the game. On the other hand, when a team is losing by 3 or 4 goals, the players may be less interested because they think that they cannot win. Doubt must be raised over the practicality of using the telemetry equipment during soccer matches, as there are obvious weak points. For example, Franks (1983) conducted a study on the heart rates of the Canadian Olympic soccer team in laboratory and match situations. He reported that several problems were encountered while studying the players' heart rates during a match situation that were not encountered during laboratory tests. The electrodes moved extensively during competition and the connection between the electrodes and the recording device worked loose. The machine itself is rather large and bulky and is not easy to wear during a game. These problems have now been resolved and a more compact device is being developed to measure and record the heart rates of soccer players during a game. It should be noted that more studies concerned with the heart rates of soccer players have been reported. The results have not been discussed because the playing time was not for a complete game of 90 min (Smodlaka, 1979) or because it was not an 11-a-side game (Kohno et al, 1988; Rohde and Espersen, 1988). In summary, it is common to use heart rate as a measure of physical workload. Technically, the equipment used by previous researchers was found to be impractical, and inconvenient for the subject. In close contact sports such as soccer, it is important that the equipment is small, light and not liable to cause any danger to the subject. From the results of this study, it is clear that short-range radio telemetry (such as use of the Sport Tester® PE 3000 , or similar equipment) permits realistic measurement of the physiological load on soccer players in live matches. It is recommended that studies should be conducted, involving a larger number of subjects of all standards of the game, including juvenile players, to give a better indication of the physiological demands of the game at all levels.
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