Soccer is considered a complex sport because performance depends on a high level of technique, tactical ability, and physical conditioning. Physical conditioning can be considered to include the anatomical, functional, biomechanical, and physiological adaptations to training (22). Despite the importance of technique and tactics, physiological adaptations are often emphasized by trainers because these adaptations have been associated with improved soccer performance (21). However, to better design fitness training programs, it is important to understand which physiological qualities best correlate with soccer-related performance.
Recent studies have highlighted aerobic power (maximal oxygen uptake: o2max and the minimum velocity needed to reach o2max: vo2max), the velocity at the onset of blood-lactate accumulation (vOBLA) and repeated-sprint ability (RSA) as important physical fitness components for soccer players (21,22,30). The importance of these variables to soccer performance has been confirmed by Rampinini et al. (29) who reported significant correlations between both peak velocity in a test of aerobic fitness (Montreal University Track Test adapted) (24) and RSA, and the distance performed at a high intensity (>19.8 km·h−1) by soccer players during a match. Moreover, Helgerud et al. (21) reported improved soccer performance, assessed by the number of sprints and the number of involvements with the ball, after the implementation of an 8-week aerobic power-training program.
The contribution of RSA and aerobic fitness to soccer performance is well described in the literature (21,22,30). However, there are conflicting findings regarding the relationship between aerobic fitness and RSA. Tomlin and Wenger (34), in their review on RSA and aerobic fitness, reported that there is an association between these variables; however, they also stated that this relationship may not be cause and effect. Aziz et al. (2) reported a moderate correlation (r = −0.346, p < 0.05) between o2max and RSA (8 × 40-m sprints with 30 seconds of recovery between sprints). However, using a different RSA test (6 × 20-m, 20 seconds of recovery between sprints), Aziz et al. (3) found no relationship between o2max and performance in their previously used RSA test. It is important to emphasize that the age and the level of the players in these 2 studies were different, factors that can influence the results comparison. However, Cooke et al. (11) also found no association between o2max and the ability of skeletal muscle to recover after anaerobic exercise.
The relationship between aerobic fitness and RSA therefore varies depending upon the study. Nevertheless, most studies have only used o2max as the major indicator of aerobic fitness. This may not be the most appropriate index because o2max is believed to be determined mainly by central factors (6), whereas RSA has been more strongly associated with peripheral factors (30). Consequently, it may be hypothesized that an index of aerobic capacity more strongly associated with peripheral factors, such as the velocity at the vOBLA, may have a greater association with RSA than o2max. If so, this would have important implications for the design of training programs to improve RSA, because different types of training have been suggested to best improve the vOBLA or the o2max (8).
The aim of this study, therefore, was to investigate the association between physiological variables related to the aerobic fitness (o2max, vo2max, and vOBLA) and RSA in elite soccer players. Because a limitation of previous studies is the use of athletes who have low aerobic fitness (3), and the indirect measurement of o2max (26,28), we investigated these associations in a higher number of elite young athletes, and using direct measures (o2max and vOBLA) in a laboratory environment. Such information has important implications for the design of training programs to improve RSA in soccer players.
Experimental Approach to the Problem
Players performed 2 maximal exercise tests at the beginning of the training season: an incremental test to determine o2max and the vOBLA, and a test to determine RSA. Based on previous studies that did not find a relationship between aerobic fitness (assessed by o2max) and RSA (3,34), we hypothesized that an aerobic index (vOBLA) that better reflects the peripheral aerobic training adaptations (9,33) may be more strongly associated with RSA than o2max. To assess this hypothesis, the relationship between aerobic and repeated-sprint variables was determined by Pearson linear correlations and multiple regressions.
Twenty-nine, well-trained, Brazilian soccer players (17.9 ± 1.0 years; 178.7 ± 5.2 cm; 73.6 ± 6.7 kg; and 11.1 ± 1.3% fat) from 2 national level teams (A, B) took part in the study. The team A (n = 15) was the champion of its category (junior league) 2 months before the study (i.e., January), whereas the B team (n = 14) was also among the best junior teams in the country. Written informed consent was received from all participants after a brief but detailed explanation about the aims, benefits, and risks involved with this investigation. Participants were told they were free to withdraw from the study at any time without penalty. All procedures were approved by the ethics committee of the Federal University of Santa Catarina (number-384/07).
Anthropometric measures included body mass (kg), height (cm), and 4 skinfold measures (suprailliac, abdomen, triceps, subscapular) to estimate percent of body fat using the equation of Faulkner (15).
Before this test, each athlete performed a period of 20 minutes of stretching and warm-up, after a 5-minute rest (1). The RSA test involved 7 maximal sprints of 34.2 m. Each sprint was performed with a change of direction, and a between-sprint recovery period of 25 seconds while the athlete positioned themselves for a new start (5). Each sprint was timed using a photocell system (CEFISE®-Speed Test 6.0). The same equipment automatically controlled the interval between sprints, with a beep. The RSA test has shown good reproducibility (CV = 1.8%, 95% IC-1.45-2.43) (36).
Blood samples (25 μL) were collected from the earlobe to measure the posttest peak blood-lactate concentration 1, 3, 5, 7, 9, and 12 minutes into the recovery. The lactate was measured on an electrochemical analyzer (YSI 2700 STAT, Yellow Springs, OH, USA), which was calibrated as recommended by the manufacturer.
The following variables were derived from the RSA test: (a) Fastest time (FT): The best time of each athlete for the 7 sprints; (b) Mean time (MT): Average time of the 7 sprints; and (c) Sprint decrement (Sdec) (16): Sdec = Σ7sprints × −1 × 100FT × 7.
Maximal Oxygen Uptake and Velocity at the Onset of Blood Lactate Accumulation
Maximal oxygen uptake (o2max) was determined on a motorized treadmill (Imbramed Millenium Super ATL, 10.200, Porto Alegre, Brazil) using an incremental protocol. The initial speed was 9.0 km·h−1 (1% grade) with increments of 1.2 km·h−1 every 3 minutes until voluntary exhaustion. During the incremental test, each subject was verbally encouraged to undertake a maximum effort. The vOBLA was determined as the intensity at a fixed concentration of 3.5 mmol·L−1 (20) and is related (r = 0.80, p < 0.05) to the maximal lactate steady state, which considered the gold standard for the assessment of the aerobic capacity (12).
Oxygen consumption (O2) was measured breath by breath using a gas analyzer, which was calibrated according to manufacturer's recommendation before each test (K4b2, Cosmed, Rome, Italy). Data were reduced to 15-second mean values, and O2max was considered the highest value obtained in a 15-second interval. o2max was defined using the criteria proposed by Taylor et al. (32) and Lacour et al. (23).
The Statistical Package for Social Sciences (SPSS 13.5 for Windows) was used to perform all statistical analyses. Descriptive analyses (mean and SD) were used. Data normality was evaluated by the Shapiro-Wilk test (n < 50). Pearson linear correlation was used to determine the relationships between the aerobic (o2max, vOBLA, vo2max) and the repeated-sprint test variables (FT, MT, Sdec, [La] Peak). Analysis of variance, followed by Tukey post hoc tests, was used to compare the 7 sprints of the RSA test. Multiple regression (Stepwise) was used to verify the influence of the aerobic (o2max, vOBLA, vo2max) and anaerobic variables (FT) on the MT. The level of significance was set at p ≤ 0.05.
The physiological characteristics of the 29 soccer players evaluated in this study are summarized in Table 1. The changes in mean sprint time during the RSA test are presented in Figure 1.
The relationships between the aerobic variables (o2max, vo2max, vOBLA) and the RSA test variables (MT, FT, Sdec) are summarized in Table 2. There was a significant relationship between vOBLA and both MT (r = −0.49, p < 0.01; Figure 2) and Sdec (r = −0.54, p < 0.01; Figure 3). In addition, the vo2max showed a moderate correlation with the MT (r = −0.38, p < 0.01; Figure 4). Table 3 reports the correlation coefficients among variables of the RSA test. According to the results obtained by the multiple regression analysis, the FT was the index that, alone, explained most of the performance variance of MT (78%). The aerobic capacity indicator, vOBLA, was the second variable selected by the model, which increased the coefficient of explanation of the MT from 78 to 89% (Table 4).
The main purpose of this study was to investigate the relationship between indices of aerobic fitness and RSA in elite, male soccer players. The major finding was that both the vOBLA and the vo2max were moderately associated with parameters derived from the RSA test (MT, Sdec). The o2max, however, had only a weak association with the Sdec. No aerobic variable was associated with the FT during the RSA test.
During repeated-sprint exercise, performance can be defined as the ability to repeat maximum power output after previous exercise (27). In this study, there was a significant decrease in performance (p < 0.05) from the fourth sprint; however, no significant differences were observed among sprints 4, 5, 6, and 7. The Sdec values (4.0 ± 1.9%) are similar to others studies (4-6%) that have evaluated RSA using similar sprint distances and similar recoveries between sprints (28,31). The inability to maintain repeated-sprint performance has been attributed mainly to metabolites accumulation, such as increase in [La] (33), the accumulation of H+ (19), and the depletion of muscle phosphocreatine (17). However, factors such as changes in the neuromuscular coordination of muscle contraction have also been linked to fatigue during repeated-sprint exercise (27). The large contribution of anaerobic glycolysis during the RSA test is supported by the high values of [La] (15.4 mmol·L−1) after the RSA test (Table 1).
In the present study, 3 main indices related to aerobic fitness were determined (o2max, vo2max, and vOBLA). The o2max represents the maximum aerobic power and seems to be mainly limited by central factors, whereas the blood-lactate response to the exercise is an indicator of aerobic capacity especially related to peripheral factors (6,18). The o2max values of our young soccer players (63.2 ± 4.9 ml·kg−1·min−1) are consistent with those typically described in the literature (55-68 ml·kg−1·min−1) (2,21,28).
This is the first study to report the vo2max for elite soccer players. The vo2max is considered the index that better describes the association between maximum aerobic power and movement economy, because individuals with similar o2max values can present different vo2max values, that is, different aerobic performances (7), because of differences in movement economy. However, it is difficult to compare our value with those reported in previous studies, mostly using endurance athletes, because of the various protocols that have been used. Nonetheless, using well-trained endurance runners and a similar protocol to our study, Billat et al. (8) and Denadai et al. (13) reported vo2max values of 20.5 ± 0.8 and 18.7 km·h−1, respectively. Moreover, Esfarjani and Laursen (14) found values of 15.6 ± 0.7 km·h−1 in moderately trained runners. These higher vo2max values in trained endurance athletes probably reflect the greater amount of training devoted to training aerobic power.
The vOBLA values of our athletes (13.5 ± 1.2 km·h−1) are similar to those found by Mcmillan et al. (25) (13.6 ± 0.3 km·h−1) for Scottish soccer players (n = 9). It is important to note, however, that these authors used a fixed concentration of 4.0 mmol L−1, instead of 3.5 mmol L−1 as in our study. As expected, both of these values are lower than those reported by Billat et al. (8) (17.6 ± 1.0 km·h−1) and Denadai et al. (13) (17.3 ± 1.1 km·h−1) for endurance-trained runners. This is the first study to report vOBLA values for elite soccer players, a common index used for the prescription and control of training in elite, junior soccer players in Brazil.
Consistent with our results, previous studies have also reported that o2max is a poor indicator of RSA (r = 0.09-0.03) (3,35). Although this contrasts with the results of some studies (r = −0.20-0.60) (2,10,28) it appears that this may be explained by differences in the type of protocol used for the RSA test. In particular, the length of the sprints may influence this relationship between these 2 variables by altering the contribution of the aerobic system (4). With very few exceptions (2,10), o2max has not been reported to be related to RSA when sprints of less than 40 m (or 6 seconds) have been used.
We observed, however, that vOBLA was more strongly correlated with RSA indices than o2max. vOBLA is a variable that better reflects the peripheral aerobic training adaptations and has been associated with an increased capillary density, and an increased capacity to transport lactate and H+ ions (9,33). It is therefore not surprising that vOBLA is more strongly correlated with RSA than o2max, because RSA has been proposed to be largely determined by biochemical changes in muscle fibers (30). Furthermore, Thomas et al. (33) reported strong correlations between RSA and both muscle oxidative capacity and the lactate removal capacity. However, our results contrast with a previous study by Bishop et al. (10) who reported similar correlation between both o2max and lactate threshold, and RSA. This may be related to the lower aerobic fitness levels of their sport-science students compared to the elite, junior athletes that we recruited.
Another important finding of this study was that the aerobic (vOBLA) and anaerobic (FT) components together explained approximately 89% of the variance of MT. This suggests that although aerobic fitness is important, RSA is largely determined by anaerobic components for energy supply (30). In particular, there was a very strong correlation between FT and MT (r = 0.88, p < 0.01) in the present study. These data corroborate with the findings of Pyne et al. (28), who reported an association (r = 0.66) between 20-m sprint performance and RSA (6 × 30-m sprints. Wadley and Rossignol (35) also reported an association (r = 0.83) between the 20-m sprint performance and RSA (12 × 20-m sprints).
In conclusion, the results of the present study suggest that, in elite soccer players, RSA is more strongly correlated with vOBLA and vo2max than the more commonly measured o2max. However, although various indices of aerobic fitness were related to RSA, the strongest predictor of RSA was the anaerobic power (i.e., the fastest individual sprint time). Taken together, these results suggest that to improve RSA, it is important to implement specific training targeting both aerobic and anaerobic components.
The strongest predictor of RSA was the anaerobic power (i.e., the fastest individual sprint time). This suggests that to improve RSA, it is important to include sprint training and training to improve strength and power. However, the results of the present study also demonstrate that aerobic fitness (vOBLA) showed a higher correlation with the RSA than the o2max, and can contribute to the multiple regression equation predicting RSA. This suggests that it is also important for team-sport athletes to do specific training to improve the vOBLA.
1. Abrantes, C, Maçãs, V, and Sampaio, J. Variation in football players' sprint test performance across different ages and levels of competition. J Sports Sci Med
3: 44-49, 2004.
2. Aziz, AR, Chia, M, and Teh, KC. The relationship between maximal oxygen uptake and repeated sprint performance indices in field-hockey and soccer players. J Sports Med Phys Fitness
40: 195-200, 2000.
3. Aziz, AR, Mukherjee, S, Chia, M, and Teh, KC. Relationship between measured maximal oxygen uptake and aerobic endurance performance with running repeated sprint ability in young elite soccer players. J Sports Med Phys Fitness
7: 401-407, 2007.
4. Balsom, P, Seger, J, Sjodin, B, and Ekblom, B. Maximal-intensity intermittent exercise: effect of recovery duration. Int J Sports Med
13: 528-533, 1992.
5. Bangsbo, J. Fitness Training for Football: A scientific Approach
. HO+Storm, Bagsvaerd, 1994.
6. Basset, DR and Howley, ET. Limiting factors for maximum oxygen uptake and determinants of endurance performance. Med Sci Sports Exerc
32: 70-84, 2000.
7. Billlat, V, Pinoteau, J, Petit, B, Renoux, JC, and Koralsztein, P. Time to exhaustion at 100% of velocity at o2
max and modeling of the relation time-limit/velocity in elite long distance runners. Eur J Appl Physiol
69: 271-273, 1994.
8. Billat, VL, Flechet B, Petit, B, Muriaux G, and Koralsztein, JP. Interval training at O2
max: effects on aerobic performance and overtraining markers. Med Sci Sport Exerc
31: 156-163, 1999.
9. Billat, VL, Sirvent, P, Py, G, Koralsztein, JP, and Mercier, J. The concept of maximal lactate steady state. Sport Med
33: 406-426, 2003.
10. Bishop, D, Edge, J, and Goodman, C. Muscle buffer capacity and aerobic fitness are associated with repeated-sprint ability in women. Eur J Appl Physiol
92: 540-547, 2004.
11. Cooke, SR, Petersen, SR, and Quinney, HA. The influence of maximal aerobic power
on recovery of skeletal muscle following anaerobic exercise. Eur J Appl Physiol
75: 512-519, 1997.
12. Denadai, BS, Gomide, EBG, and Greco, CC. The relationship between onset of blood lactate accumulation, critical velocity, and maximal lactate steady state in soccer players. J Strength Cond Res
19: 364-368, 2005.
13. Denadai, BS, Ortiz, MJ, and Mello, MT. Physiological indexes associated with aerobic performance in endurance runners: Effects of race duration. Rev Bras Med Esporte
10: 405-407, 2004.
14. Esfarjani, F and Laursen, PB. Manipulating high-intensity interval training: Effects on o2
max, the lactate threshold and 3000 m running performance in moderately trained males. J Sci Med Sport
10: 27-35, 2007.
15. Faulkner, JA. Physiology of swimming and diving. In: Exercise Physiology
, Falls, M, ed. Baltimore, MD: Academic Press, 1968.
16. Fitzsimons, M, Dawson, B, and Ward, D. Cycling and running test of repeated sprinting ability. Aust J Sci Med and Sport
25: 82-87, 1993.
17. Gaitanos, GC, Williams, C, Boobis, LH, and Brooks, S. Human musclemetabolism during intermittent maximal exercise. J Appl Physiol
75: 712-719, 1993.
18. Gladen, LB. Lactate metabolism: A new paradigm for the third millennium. J Physiol
558: 5-30, 2004.
19. Glaister, M. Multiple sprint work: Physiological responses, mechanisms of fatigue and the influence of aerobic fitness. Sports Med
35: 757-777, 2005.
20. Heck, H, Mader, A, Hess, G, Mucke, S, Muller, R, and Holmann, W. Justification of the 4mmol/l lactate threshold. Int J Sport Sci
6: 117-130, 1985.
21. Helgerud, J, Engen, LC, Wisloff, U, and Hoff, J. Aerobic endurance training improves soccer performance. Med Sci Sport Exerc
33: 1925-1931, 2001.
22. Impellizzeri, FM, Rampinini, E, and Marcora, SM. Physiological assessment of aerobic training in soccer. J Sports Sci
23: 583-592, 2005.
23. Lacour, JR, Padilla-magunacelaya, S, Chatard, JC, Arsac, L, and Bathélémy, JC. Assessment of running velocity at maximal oxygen uptake. Eur J Appl Physiol
62: 77-82, 1991.
24. Leger, L and Boucher, R. An indirect continuous running multistage field test: The Universite de Montreal track test. Can J Appl Sport Sci
5: 77-84, 1980.
25. Mcmillan, K, Helgerud, J, Grant, SJ, Newell, J, Wilson, J, Macdonald, R, and Hoff, J. Lactate threshold responses to a season of Professional British youth soccer. Br J Sports Med
39: 432-436, 2005.
26. Meckel Y, Machnai O, and Eliakim, A. Relationship among repeated sprint tests, aerobic fitness, and anaerobic fitness in elite adolescent soccer players. J Strength Cond Res
23: 163-169, 2009.
27. Mendez-Villanueva, A, Hamer, P, and Bishop, D. Fatigue responses during repeated sprints matched for initial mechanical output. Med Sci Sport Exerc
39: 2219-2225, 2007.
28. Pyne, B, Saunders, PU, Montgomery, PG, Hewitt, AJ, and Sheehan, K. Relationships between repeated sprint testing, speed, and endurance. J Strength Cond Res
22: 1633-1637, 2008.
29. Rampinini, E, Bishop, D, Marcora, SM, Ferrari bravo, D, Sassi, R, and Impellizzeri, FM. Validity of simple field tests as indicators of match-related physical performance in top-level professional soccer players. Int J Sport Med
28: 228-235, 2007.
30. Spencer, M, Bishop, D, Dawson, B, and Goodman, C. Physiological and metabolic responses of repeated-sprint activities, Sport Med
35: 1025-1044, 2005.
31. Spencer, M, Fitzsimons, M, Dawson, B, Bishop, D, and Goodman, C. Reliability of a repeated-sprint test field-hockey. J Sci Med Sport
9: 181-184, 2006.
32. Taylor, HL, Buskirk, E, and Hensciiel, A. Maximal oxygen intake as an objective measure of cardio-respiratory performance. J Appl Physiol
8: 73-80, 1955.
33. Thomas, C, Sirvent, P, Perrey, S, Raynaud, E, and Mercier, J. Relationships between maximal muscle oxidative capacity and blood lactate removal after supramaximal exercise and fatigue indexes in humans. J Appl Physiol
97: 2132-2138, 2004.
34. Tomlin, DL and Wenger, HA. The relationship between aerobic fitness and recovery from high intensity intermittent exercise Sports Med
31: 1-11, 2001.
35. Wadley, G and Rossignol, P. The relationship between repeated sprint ability and the aerobic and anaerobic energy systems J Sci Med Sport
1: 100-110, 1998.
36. Wragg, CB, Maxwell, NS, and Doust, JH. Evaluation of the reliability and validity of a soccer-specific field test of repeated sprint ability. Eur J Appl Physiol
83: 77-83, 2000.