The development of sport and exercise research has provided scientific and practical support for the total evolution in this field. The constant overcoming of limits and records gives the competitive sports scene a need for in-depth knowledge in order to increase the understanding and possibilities of planning of all aspects involved in the sport. The exercise physiology, through the techniques of anthropometric, physiological, cardiovascular, and neuromuscular evaluation, constitutes a singular and important basis in corroboration of this reasoning.
McArdle (2003), emphasizes the importance of measuring the human energetic capacities for sports, saying that the principles of performance and the principles of training must respect the specificity of the sport. For him, speed, power and endurance must be applied accurately within the context of specific patterns of movement and metabolic demands and activity. The planning of the routines of evaluations referring to specificity of each sport is an optimized model for sports success, and with soccer it is no different. Silva et. al (2002) emphasizes the importance of establishing a plan of evaluation routines in controlled environments, such as in a laboratory of exercise physiology, to rule out possibilities of interference of external factors harmful to soccer performance. For the author, it is important to perform functional tests in controlled environments, constituting a safe, precision and secure means of control for the scientific development of training. Within this context, the characterization of the parameters relevant to the physical requirements of the sport becomes essential for the success of the sports field. Garret Jr. (2003) briefly describes the physiological aspects and general principles relevant to soccer and points out as important the following characteristics: aerobic power, anaerobic power, body composition, strength, flexibility, agility and speed.
According to Silva et. al (2002), it becomes essential for professional soccer team to periodically systematize on the athletes’ schedule. This author further stresses the importance of conducting tests in controlled environments in order to avoid that intervening factors impact the reliability of the evaluations. Stolen et. al (2005) states that soccer is not a science, but that science, through assessments and training control, can help an optimized performance in this sport. Therefore, the purpose of this literature review is to demonstrate the anthropometric, physiological, cardiovascular and neuromuscular factors that impact professional soccer players.
General Physiological Characteristics of High Athletes Yield
The application of assessments of the performance capacities of an athlete is one of the main characteristics in the development of sports training science, both in research and in its practice. For Silva et. al (2002), evaluations should occur before the athletic season begins, as well as during the competitive phase, and must obey a consistent planning and in accordance with modern techniques, used and proven internationally through experience and technical scientific support. McArdle (2003) argues that appropriate physiological measurements and performance tests assess the ability of each energy system, according to the specificity of each sport. In this sense, the specificity of the sport is not only a fundamental principle of training, but equally important in the evaluative aspects of the sport. The author further states that the concept of specificity has been recognized in attempts to adapt the assessment task to the specific characteristics of the different sports modalities.
According to Garret Jr. (2003), one of the major challenges facing researchers in the field of sports medicine and physiology of exercise is to understand the factors that contribute to a successful performance in the sport. In this perspective, the author emphasizes that it is extremely important to be able to measure these capabilities and incorporating the data into training, planning, and performance analysis for athletes and coaches. According to the author, the use of tests implies evaluating the athletes’ current capacity and comparing with established standards, as well as monitoring physiological changes as a result of training, providing guidance on the sporting event to be selected, and serving as an instrument of motivation. Based on these considerations, Stolen et. al (2005) identifies the relevant physiological characteristics employed in high-performance soccer. In his study, the author reviewed 843 scientific articles on the physiology of soccer, and described, among the physiological characteristics of soccer, the main evaluations that permeate modern professional soccer. Among the most important aspects are, the laboratorial evaluations of maximum oxygen intake, anaerobic threshold, body composition, muscle strength and power, speed and agility field assessments. Adopting an evaluative approach, Alves et al. (2015) states that analyzing the level of urea and creatine kinase concentration in the blood, a few hours after training, helps to determine if the volume of the load was adequate.
In the same evaluation perspective, Schneider et al. (2018), with reference to studies on soccer training and game monitoring, suggests the use of the heart rate monitor as a general training load detector. In this regard, it is expressed the importance of knowing one’s heart rate during games and or training, with how the game load influences the physical state of the soccer players. The author also considers the individualized evaluations of the maximal oxygen consumption and maximal heart rate as an important factor for the organization of a team. In the same line of reasoning, Silva et. al (2002) emphasizes the importance of establishing a periodic planning of soccer specific evaluation routines, as well as in any sport. In order to achieve success in the sports field, these three aspects need to be present: assessments necessary for the specific modality, exploring the specificity of this sport and establishing an organized evaluation routine that accompanies the periodization and schedule of the athletes. In soccer, according to the above authors mentioned, some anthropometric and body composition characteristics: functional and metabolic, cardiovascular, biochemical and neuromuscular, constitute an optimized and satisfactory test battery that can and should be applied in professional soccer teams, seeking the evolution in all directions.
Anthropometric and Body Composition Characteristics of Soccer Players
The techniques of body composition evaluation are of great importance for the individualized control of athletes’ training. Heyward (2000) argues that the anthropometric method is a cheap and effective field method (in terms of validity and reliability), which has been used in all population, sex and age groups. The author points out that athletes’ body composition has been of considerable interest on the part of exercise scientists, since the athletic population generally has considerably lower fat indexes than sedentary populations. In addition to formulating a guideline for weight determination ideal for an athlete to determine a minimum plateau or floor for maximum fat loss in an individualized athletic program, provides absolute and percentage data on athletes lean mass, as well as provides data on athletes’ dietary performance, among other relevant characteristics . The wide variety of body composition and size characteristics among elite athletes demonstrates the importance of the physicist’s potential for high-level performance in various sports (Garret, 2003).
In this regard, McArdle (2003) points out that the evaluation of body composition quantifies in absolute terms and percentages the main components of the body. The current assessment of body composition separates body mass into two main components – body fat and fat free mass. The author also states that it is of great importance to evaluate body composition, since athletes in general have unique somatotype characteristics for their specific sport, and since the specific requirement of each sport largely determines the anthropometric profile of the athlete. Garret (2003) reiterates this assertion by postulating that high-level performance seems to be improved by specific physical characteristics in terms of size, composition and body structures, as seen in the profiles of athletes of various sports. Based on the above arguments, it is clear the importance of establishing a routine program for assessments of body composition in athletes in general. In soccer, available literature indicates that the soccer athlete tends to be tall, strong and thin, with an average height of 180cm, average weight of 75 kg, and fat percentage usually ranging between 8 and 12% (Garret, 2003).
Functional and Metabolic Characteristics of Soccer Athletes
In exercise physiology, the maximum oxygen consumption (VO2 maximum) is a variable considered extremely important for most sports. For McArdle (2003) conception, maximal VO2 is a fundamental measure of physiological functional capacity for exercise, since it represents a high integration of pulmonary, cardiovascular and neuromuscular functions. According to Garret (2003), the maximum VO2 is physiologically defined as the highest rate of transport and oxygen utilization that can be reached at the peak of physical exercise. According to the author, the high capacity to consume oxygen is a prerequisite for success in endurance sports. Likewise, Weineck (2000) explains that a well-developed aerobic resistance causes the soccer player to have an increase in the physical performance, a good capacity of recovery, decrease of injuries and contusions, increase of psychic tolerance, prevention of tactical failures in fatigue function, reduction of technical errors, maintenance of high-speed action and reaction, and maintenance of health. The author concludes that the maximum VO2 represents a fundamental prerequisite for the performance of soccer players. Corroborating this idea, Godik (1996) affirms that the fundamental role of aerobic capacities in soccer is undeniable. According to McArdle (2003), a considerable research effort was able to develop and standardize tests capable of determining maximum aerobic power and to provide normative standards related to age, gender, training status and body size. Therefore, it is necessary to carry out periodic evaluations of the maximum VO2 in professional players. Silva et. al (2002), justifies the importance of these assessments by reiterating the above statements and adding that knowledge of these data is necessary for the evolution of athletes.
For Weineck (2000), corroborating the above statements, the soccer player is required a satisfactorily developed aerobic resistance. However, in no way should this resistance be comparable to that of a long-distance runner. For the purposes of practical applicability, the development of aerobic power (VO2 maximum) does not represent the valence of greater interest in professional trainings, since according to Weineck (2000), for soccer players, the goal will never be the maximum development of resistance aerobic training; the training of this capacity should be directed, as a priority, to meet the specific requirements of the modality. Thus, aerobic resistance must be optimally developed, but not maximally, so as not to overwhelm the volume of aerobic training, as this culminates in decreased hormone testosterone, responsible recovery and anabolic metabolism of proteins. In this perspective, the knowledge of the anaerobic threshold, as well as of the speed played in this level of intensity, receives great attention on the part of the coaches, physical trainers and scientists of the sport. According to McArdle (2003), the anaerobic threshold corresponds to the maximum intensity of exercise that can be sustained by aerobic metabolism, without excessive production of the metabolite lactic acid, due to the degradation of the glucose molecule. Garret (2003) expresses the anaerobic threshold as a probable indicator of the highest intensity of exercise performed at the expense of oxidative phosphorylation without extensive use of the anaerobic mechanism for obtaining energy. The author also explains that the importance of knowing the level of load reached at the anaerobic threshold, as well as its absolute value, lies in knowing the level of intensity that will determine fatigue.
Cardiovascular Characteristics of Soccer Athletes
The knowledge of cardiovascular aspects in the soccer athlete is also an important parameter within the optimized control of specific evaluations and exercise prescription to look for the evolution in the sport. According to McArdle (2003), the cardiovascular system acts as an integrating agent of the body, as a unit providing the active muscles with a continuous stream of nutrients and oxygen in order to maintain a high level of energy transference. Weineck (2000) argues that for a successful aerobic performance in soccer, there is a need for an effective transport system by the cardiovascular system, so that the performance of the musculature is not limited. The author further states that the heart representativeness works as the engine of this system, pumping blood through the vessels into the muscle cell. The physiological adaptations induced by the training depend mainly on the intensity of the overload, and the heart rate (HR) is an effective way to express the intensity of exercise (McArdle, 2003). For Godik (1996), it is necessary to know how the game load influences the physical state of the athletes in soccer, and the heart rate composes an evaluation index of the physiological stress represented by this load. In this regard, it is accepted that evaluations of the cardiovascular components related to physical fitness are of great relevance in order to achieve evolution and success in the sports environment in general. In soccer, the evaluation of maximum heart rate and subsequent monitoring of maximum heart rate percentages during training and games have been shown to be an effective characterizer of exercise intensity (Hoff et al., 2002). McArdle (2003) postulated that endurance training places the sinus node of the heart under a greater influence of acetylcholine, the parasympathetic hormone that slows the heart rate, with the concomitant decreased sympathetic activity. The author uses this explanation to justify the lower values of resting heart rate found in endurance athletes, or of mixed modalities that share the continuous aerobic requirement, as in the case of soccer.
To emphasize the relevance of evaluation routines, it is recommended to perform periodic ergospirometric tests in the athletes, in order to verify the individual cardiovascular and physiological alterations by the progressive increase of workloads, as well as the determination of resting heart rate and maximal heart rate values. For McArdle (2003), the knowledge of the resting heart rate and maximum heart rate values allow the establishment of the exercise intensities in percentage terms – percentage of the maximum heart rate and percentage of the frequency (Karvonen method) – with wide use for training control. According to Weineck (2000), the monitoring of the heart rate during the games and trainings reflects the magnitude of the work performance physiological (in estimation) and cardiovascular stress in athletes. Based on these considerations, it is concluded that the evaluation of the cardiovascular profile of athletes is of paramount importance to professional soccer, as well as in most sports, and according to Silva et. al (2002), one should incorporate a routine of evaluations in the preparation of the periodization of the athlete’s soccer players.
Neuromuscular Characteristics of Soccer Athletes
As with all categories of assessments described so far, neuromuscular assessments are also of great importance for any sport. A widely used test for high-level soccer players, according to Krustrup et al. (2006), is the Yo-Yo Recovery. The author reports that this test has shown to have great reproducibility and to be sensitive to the adaptations of training, within the soccer scope. According to the author, the Yo-Yo Recovery test is an option for the 20-meter alternating-run test and was designed to reflect as closely as possible, the intermittent state of activity in sports such as soccer, as it interweaves moments of exercise with recovery periods. Bangsbo (1996) classifies the test as an important tool in determining the individual’s level of conditioning.
Each sport modality has a specificity of corporal requirement, in order to trace a characteristic profile in all possible biological aspects that can be modified through training stimuli, such as body composition and maximal oxygen consumption. Just as for all sports, for soccer there is the making of a physical profile considered standard among athletes, which can be slightly altered according to the specific position and function of each athlete. Besides, the specificity of the sport is not only a fundamental principle of training, but equally important in the evaluative aspects of the sport. In order to achieve success in the soccer field, it is necessary assessments for the specific modality, exploring the specificity of the sport and then establishing and organized evaluation routine.
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