Football is an intermittent, high-intensity sport that requires a high level of aerobic fitness as well as optimal anaerobic capabilities. During a football game, the typical distance covered by a high-level player varies on average from 10 to 13 km, most of which can be covered at low intensity. In addition to a purely basic aerobic activity, there are also high-intensity actions, characterized by accelerations, sprints, changes of direction, jumps, lateral steps, plating and specific technical movements.
Field fitness tests improve the specificity of the test, but provide less accurate measurements than laboratory tests.
These actions, besides being the most interesting moments in a football match, are sometimes also the most decisive.
Physical tests to determine player profiles
Obviously, each player has his or her own player profile determined by their individual physiological profile, genetics, skills and the specific requirements of the role played. Therefore, it is important that athletic trainers and coaches have access to objective data on the physical state of the athlete during the season; this, in addition to talent selection and training purposes, can also be used as feedback and motivating factor for the players. In this respect, physical evaluation tests are indispensable to obtain detailed information before and during the competitive period.
Due to the complex nature of football and the difficulty in isolating specific performance indicators, there is no single test capable of measuring all the determinants of physical performance in football at the same time, but at most one or two components. Laboratory tests are certainly the most reliable but have often been questioned for their high cost and for questions of specificity of the movement.
In addition, there are field tests that in recent years have come to measure certain characteristics with very high accuracy; for example, tests to assess aerobic capacity have reported accuracy errors of about 10-15%. A recent review of the literature conducted by Jemni and colleagues, published in Sport Medicine, has highlighted what are the methods of measurement and evaluation specific to football, focusing particularly on cardiorespiratory tests; in the following paragraphs we will consider some of the salient aspects.
Laboratory Test: Evaluation of VO2max
VO2max (maximum oxygen consumption) is the maximum amount of oxygen that the body can use during exercise by breathing air at sea level. VO2max is one of the most widely used aerobic resistance indicators. It evaluates metabolic power using a metabolimenter in laboratory settings, and is considered as the gold standard. Data in the literature show that VO2max in footballers can vary from 50 to 75 ml kg min, which supports the concept that football.
In this respect, Bangsbo highlighted how about 90% of the total energy during a football match comes from the oxidative system. Measuring V02max in athletes using the metabolimeter is certainly the most reliable method, but it is recommended to replicate as much as possible the conditions of the race and then perform the test on treadmill rather than on a cycloergometer.
In addition, VO2max values differ significantly between game positions. In fact, midfielders have significantly higher VO2max values than defenders and sometimes attackers when expressed relative to body weight (ml kg min-1). Finally, some studies have observed that VO2max improves significantly during pre-season as a result of targeted aerobic conditioning programs.
The anaerobic threshold
While VO2max measures the maximum oxygen consumption capacity during exercise, the level at which intense exercise can be maintained for a long time has been referred to as the anaerobic threshold. The assessment of the anaerobic threshold is often performed by measuring lactate in the blood and is usually around 4 mmol./L, also known as OBLA (beginning of lactate accumulation in the blood). The anaerobic threshold in the adult footballer ranges between 76.6 and 90.3% of the maximum heart rate value.
Lactate threshold
The lactate threshold refers to VO2 above which the lactate in the blood exceeds resting values and its production exceeds its removal capacity during incremental exercise. This point may indicate the transition from predominantly aerobic to anaerobic metabolism. This suggests that players with a higher lactate threshold are able to cover greater distances at greater intensities without an accumulation of lactate in the blood.
Helgerud and collaborators reported that the improvement of the lactate threshold from 47.8 to 55.4 ml kg-1 min-1 after 8 weeks of interval training in elite under-18 players. Instead, Edwards and colleagues investigated the changes in VO2max during the competitive season. While the lactate threshold was significantly improved from the first to the second test (81 vs 86% of VO2max, respectively), VO2max showed no difference between the two tests.
Also the lactate threshold is sensitive to the variation of the game position. In fact, Bangsbo and colleagues [6, 7] showed that the lactate thresholds of elite external midfielders are higher than those of central midfielders, defenders and goalkeepers. The protocol used to determine the lactate threshold is very important, as the initial intensity of an exercise must be chosen carefully so as not to cause an immediate increase in lactate in the blood and thus generate artifacts in the test.
Field test
Performing a test in the laboratory is certainly the most accurate method of evaluating a given physical characteristic. However, the high costs associated with these accurate techniques have prompted technicians and researchers to design field tests as practical evaluation alternatives. Field fitness tests improve the specificity of the test, but provide less accurate measurements than laboratory tests.
In the Loughborough Intermittent Shuttle Test (LIST), you run between two lines at a distance of 20m at various speeds dictated by audio signals. Test measurements include sprint time, total distance covered, blood lactate, heart rate and perceived effort. Although the LIST simulates the physiology of football, in terms of distance travelled, it does not include many specific aspects such as backward running, jumps and ball conduction, so it does not appear to be a specific test for football.
Léger's test, developed by Léger together with Lambert, requires a run back and forth test between two separate 20 m lines, with speed increases adjusted by acoustic signals. The participant must reach the bottom line in the shuttle respecting the acoustic signal, and if he fails to reach it in time for 2 times the test is considered finished. The VO2 max is estimated based on the step reached at the end of the test using a regression equation [VO2 max = (5,857 × speed in the last stage) - 19,458].
In the second part of the extract, the proposed field tests to assess aerobic resistance in football will continue to be examined.
- Bangsbo J, Mohr M, Krustrup P. Physical and metabolic demands of training and match-play in the elite football player. J Sports Sci. 2006;24:665–74.
- Ekblom B. Applied physiology of soccer. Sports Med. 1986;3(1):50–60.
- Reilly T, Thomas V. A motion analysis of work-rate in different positional roles in professional football match-play. J Hum Mov Stud. 1976;2:87–9.
- Astrand PO, Rodahl K. Textbook of work physiology: physiological bases of exercise. 3rd ed. New York: McGraw Hill; 1986.
- Monèm Jemni, Mohammad Shoaib Prince and Julien S. Baker. Assessing Cardiorespiratory Fitness of Soccer Players: Is Test Specificity the Issue?–A Review. Sports Medicine - Open (2018) 4:28
- Bangsbo J. The physiology of soccer with special reference to intense intermittent exercise. Acta Physiologica Scandinavia. 1994;151(619):1–156.
- Bangsbo J. Energy demands in competitive soccer. J Sports Sci. 1994;12:S5–S12.
- Helgerud J, Engen LC, Wisloff U, Hoff J. Aerobic endurance training improves soccer performance. Med Sci Sports Exerc. 2001;33:1925–31.
- Edwards AM, Clark N, Macfayden AM. Lactate and ventilatory threshold reflect the training status of professional soccer players where maximum aerobic power is unchanged. Journal of Sports Science and Medicine. 2003;2(1):23–9.
