Training and testing physical capacities for elite soccer players JAN HOFF Department of Circulation and Medical Imaging, Faculty of Medicine, Norwegian University of Science and Technology, Trondheim, Norway (Accepted 24 July 2004) Abstract Elite soccer players spend a substantial amount of time trying to improve physical capacities, including aerobic endurance and strength and the strength derivatives of speed and power. The average oxygen uptake for international soccer teams ranges from 55 to 68 ml �� kg71 �� min71 and the half-squat maximal strength from 120 to 180 kg. These values are similar to those found in other team sports. Recently, it has been shown that the heart���s stroke volume is the element in the oxygen chain that mainly limits aerobic endurance for athletes. These findings have given rise to more intensive training interventions to secure high stroke volumes, which, in turn, have proved positive in changing both maximal oxygen consumption and soccer performance in terms of distance covered, contacts with the ball and number of sprints in a game. The training employed has consisted of 4 6 4-min ������intervals������ running uphill at 90��� 95% of maximal heart rate interspersed with 3 min jogging at 70% of maximal heart rate to facilitate removal of lactate. Research has revealed that a soccer-specific training routine with the ball might be as effective as plain running. Strength training to produce neural adaptations has been effective in changing not only strength in terms of ������one-repetition maximum������, but also sprinting velocity and jumping height, in elite soccer players without any change in body mass. The same training has also improved running economy and thus aerobic endurance performance. The training regimen used for a European Champions League team was 4 6 4 repetitions of half-squats with the emphasis on maximal mobilization of force in the concentric action. Keywords: Endurance, lactate threshold, maximal oxygen uptake, neural adaptations, one-repetition maximum, rate of force development, running economy, strength Introduction Football (soccer) players require technical, tactical and physical skills to succeed. In part, professional soccer emphasizes selection between players as well as development of the players��� performance. This review concentrates on the development of players��� performance and primarily their physical resources. The current review focuses on the approaches used by our research group, as extensive reviews exist with a broader perspective (Shephard, 1999). Individual technique, tactics and physical resources are all important when evaluating performance differences in soccer. It is difficult to discriminate between the relative importance of each of these elements when evaluating performance differences. Muscular strength and power share importance with endur- ance within the physical resources. Endurance training The average exercise intensity for a player in a 90- min soccer match is close to that of the lactate threshold, or 80 ��� 90% of maximal heart rate (Bangsbo, 1994 Reilly, 1990). It would be physio- logically impossible to maintain a higher average intensity over a longer period of time due to the resultant accumulation of blood lactate. Expressing intensity as an average over 90 min could result in substantial loss of specific information. In soccer matches, the high-intensity periods usually constitute the most interesting parts of the game, where accumulation of lactate takes place. It is necessary for the players to experience intervening periods of low-intensity exercise to remove lactate from the working muscles and from the blood. There is a significant correlation between maximal oxygen uptake ( _ V O2max) and distance covered Correspondence: J. Hoff, NTNU, DMF, NO-7489 Trondheim, Norway. E-mail: jan.hoff@medisin.ntnu.no Journal of Sports Sciences, June 2005 23(6): 573 ��� 582 ISSN 0264-0414 print/ISSN 1466-447X online �� 2005 Taylor & Francis Group Ltd DOI: 10.1080/02640410400021252

during a match (Bangsbo, 1994 Smaros, 1980). Distance covered during a match was shown to differ a lot in studies carried out in the early 1970s, partly because of flawed methods. Measurements have become more reliable (Reilly, 1990) and differences between top teams are now considered to be quite small. For example, it has been reported that male players cover 10,245 m (Van Gool, Van Gerven, & Boutmans, 1988), 9845 m (Ohashi, Togari, Isoka- wa, & Suzuki, 1988), 10,800 m (Danish elite players: Bangsbo, 1992), 11,527 m (Australian elite players: Withers, Maricic, Wasilewski, & Kelly, 1982) and 10,335 m (elite junior players: Helgerud, Engen, Wisl��ff, & Hoff, 2001). These values are considered reliable, objective and valid. Apor (1988) reported that the ranking of four teams in the Hungarian top soccer division reflected the ranking between the average _ V O2max of the teams. This finding indicates that a relationship exists between _ V O2max and team performance. The results of Wisl��ff, Helgerud and Hoff (1998) supported this assumption by also demonstrating a clear difference in _ V O2max between the top team and a team placed lower in the Norwegian elite division. The average _ V O2max for international level male soccer players has been reported to range between 55 and 68 ml �� kg71 �� min71, with individual values of more than 70 ml �� kg71 �� min71 having been re- corded (Davis, Brewer, & Atkin, 1992 Reilly, 1994 Wisl��ff et al., 1998). These values are similar to those reported for other team sports, but substantially lower than those for elite performers in endurance sports, where values near to 90 ml �� kg71 �� min71 have commonly been record- ed. Maximal oxygen uptake expressed in ml �� kg71 �� min71 implies linearity between oxygen cost and body mass, which is not the case (Bergh, Sj��din, Forsberg, & Svedenhag, 1991). When expressing _ V O2max in ml �� kg71 �� min71, work capa- city is overestimated in light individuals (e.g. endurance sport athletes) and underestimated in heavy individuals. The opposite is true when evaluating the oxygen cost of running at submaximal workloads. Consequently, several studies (Bergh et al., 1991 Helgerud, Ingjer, & Str��mme, 1990 Hoff & Helgerud, 2004 Wisl��ff et al., 1998) have concluded that comparisons between individuals of different body mass of oxygen uptake determined when running should be expressed in ml �� kg70.75 �� min71. Allometric scaling is described in greater detail elswhere (Astrand �� & Rodahl, 1986 Bergh et al., 1991 Helgerud et al., 1990 Hoff & Helgerud, 2004 Wisl��ff et al., 1998). The highest reliable average _ V O2max for a profes- sional soccer team was reported by Wisl��ff et al. (1998) to be 67.6 ml �� kg71 �� min71 or 200.2 ml �� kg70.75 �� min71 for the Norwegian team Rosenborg. The difference in terms of work capacity to an average team with a mean _ V O2max about 6 ml �� kg71 �� min71 lower is, in terms of distance covered and thus in playable positions, suggested to be similar to having one extra player on the field (Wisl��ff et al., 1998). Soccer players should ideally be able to maintain a high exercise intensity throughout a game. Studies, however, have shown a reduction in distance covered, more low-intensity than high-intensity work, a reduced heart rate, reduced blood glucose concentrations and reduced lactate concentrations in the second compared with the first half of games. This observation indicates a reduced level of activity (Ekblom, 1986 Tumilty, 1993). Players who have a high _ V O2max have high glycogen stores necessary for the release of energy, which is required to perform the high-intensity sprints and physical challenges throughout a competitive match. They also have an elevated rate of recovery (Bangsbo & Mizuno, 1988 Ekblom, 1986). Players with a higher _ V O2max also perform the highest number of sprints and take part more often in decisive plays during a match than those with lower values (Smaros, 1980). As glycogen stores are reduced during a match, an increasing amount of energy has to be delivered from fat. Players with a higher _ V O2max are better able to mobilize and utilize fat at the same relative workload and are thus able to ������save������ glycogen for use in the most intensive and decisive plays during a match (Reilly & Thomas, 1979). Players with a higher _ V O2max are also able to run further and at a higher intensity before a reduction in glycogen stores and accumulation of lactate force them to reduce their intensity. This fatigue will affect the quality of technical and tactical elements in a match (Ekblom, 1986 Tumilty, 1993). That a high level of lactate accumulation reduces technical ability was demon- strated in a study in which players were able to perform an average of 64 juggles with the ball ��� that is, keeping it off the ground ��� before a block of hard training leading to lactate accumulation. After the training session, the average number of juggles was only three (Ekblom, 1986). When assessing aerobic performance, _ V O2max is considered the most important determinant. Other important factors include the lactate threshold and running economy (Helgerud et al., 1990 Hoff, Gran, & Helgerud, 2002a Hoff, Helgerud, & Wisl��ff, 2002b Pate & Kriska, 1984). In some sports, the lactate threshold might be a better indicator of aerobic endurance performance than _ V O2max (Ja- cobs, 1986). The lactate threshold determines the highest workload, oxygen consumption or heart rate in dynamic work using large muscle groups, where production and elimination of lactate are balanced (Helgerud et al., 1990). The lactate threshold might 574 J. Hoff