athletes' health. Therefore, monitoring the stress-recovery balance represents a prominent factor for athletes' health and deserves more attention [52,85].
The RESTQ-Sport questionnaire has become widely used in research to monitor the stress-recovery balance. This self-report measure indicates the extent to which an athlete is physically or mentally stressed, as well as whether and what forms of recovery the athlete may use. The questionnaire covers physical and psychosocial aspects of both stress and recovery. For example, it includes physical stress or fitness measures that are useful in identifying possible mismatches between stress and recovery due to training or competition [46]. Versions of the RESTQ-Sport have been administered during intensive training and during preparation and competition periods. However, questionnaires need to be administered repeatedly to be effective, and the shorter RESTQ-Sport version is preferred for practical reasons. [164]
1.3 Scientific basis for physical training for Futsal athletes
1.3.1 Anthropometric characteristics of Futsal athletes
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Futsal is considered a high-intensity sport, so the psychophysiological demands are the main factors that coaches are concerned about. Furthermore, teams with good morphological characteristics show better ability to apply trained tactical actions than teams with low physical characteristics. Endurance and speed are two main characteristics of Futsal players. Both 11-a-side football and Futsal players do not have significant differences in their anthropometric and physiological characteristics [114]. However, the individual profiles of Futsal players are very diverse and have some characteristics that are not related to their performance, such as increased muscle mass and weight balance [49]. Futsal players have an average standing height of 177 cm, weigh 70-77 kg, and have a body fat percentage of 10-12% [180]. Studies have found that high body fat percentages negatively affect the players' ability to dribble. In addition, the athlete's leg strength when jumping high is about 40-50 cm and jumping far is 220-240 cm [73,99]
In terms of playing position, goalkeepers have a higher standing height, body fat percentage and muscle mass while wingers (Ala) have the lowest standing height [33]. Goalkeepers have an average standing height of about 182.4 cm, weight of 81.1 kg, BMI of 24.3 kg/m2,
73.4 kg muscle mass and 9.2% body fat; Defender (Fixo) has an average standing height of 175.9 cm, weight of 68.8 kg, BMI of 23.7 kg/m2, 62.5 kg lean mass and 9.1% body fat; Winger (Ala) has an average standing height of 170.5 cm, weight of 76.3 kg, BMI of 24.6 kg/m2, 69 kg lean mass and 9.9% body fat; Forward (Pivot) has an average height of 178.6 cm, weight of 77.7 kg, BMI of 24.4 kg/m2, 70 kg lean mass and 9.9% body fat. Regarding the age of development, studies show that the differences between athletes in anthropometric and physiological characteristics are stable at 16-19 years old. In addition, athletes around 20 years old are not significantly different from adults, they can participate in professional Futsal teams. The statistics of the anthropometric profile of Futsal athletes is a very important factor for coaches to organize and evaluate training, adjusting to suit the ability of each athlete. The influence of age will have a relatively large impact and is a problem observed in young people when participating in Futsal competitions often meet better in terms of anthropometric and physiological needs than other ages.
1.3.2 Physiological characteristics of Futsal athletes
Many researchers have assessed the physiological demands of a Futsal match by assessing factors such as heart rate, blood lactic acid concentration, and kinematic characteristics [49]. The high-intensity actions of Futsal determine the physiological demands and the limited distance traveled, so the speed of transition is an important factor affecting the outcome of the match. Furthermore, the unlimited substitutions in the Futsal Laws help maintain the high intensity of the match [116]
The distance covered by athletes has been shown to increase to 5,000 m for professional Futsal players and 4,500 m for amateur players. Athletes have increased their distance covered from 108 m/min (Molina, 1992) [117] and 113 m/min (Oliveira, 1999) [138] to 117 m/min (Barbero-Alvarez 2008) [49]. This study also found that Futsal speeds are higher than 11-a-side football (Bangsbo, 1991) [47] and other sports [31]. However, Futsal players cover different distances depending on their playing position.
Therefore, VO2max varies between athletes in different playing positions. Although Futsal athletes have a higher VO2max of 70-75% [59], goalkeepers 60-70% VO2max, the Ala position is 81-100% and Fixo is 71-90% [39]. Similarly, the energy expenditure of Ala is about 350 calories, Fixo 250 calories and goalkeeper 110 calories [39]. This may also be the basis for the fact that key players are often the first to be replaced in high-intensity matches. Some other studies by Barbero-Alvarez, Castagna [49, 59] concluded that Futsal athletes have a maximum heart rate of more than 85%, an average heart rate of about 90% and the average intensity of a Futsal match is about 84% of maximum heart rate and 75% of VO2max. However, research has shown that indicators such as average heart rate, maximum heart rate and distance covered during high-intensity activities are reduced, the study has differentiated the physical demands of a Futsal match: Athletes spend 0.3% of their time in low-intensity activities (below 65% of maximum heart rate), 16% in moderate-intensity activities (65-85% of maximum heart rate) and 83% in high-intensity actions (more than 85% of maximum heart rate).
Furthermore, Futsal players performed one high-speed run every 79 seconds while they changed their activity every 3.3 seconds throughout the match [59,79,80]. Research shows that professional Futsal players increased low-intensity actions and decreased high-intensity actions in the second half, which may be influenced by the tactics and experience of players who save energy for the end of the match [79].
Due to the nature of frequent changes in activities and directions, flexibility is a very important ability of Futsal athletes, which can affect their performance in Futsal. Moreover, experience is an important parameter that affects the level of athletes. Therefore, in Futsal training, it is necessary to improve flexibility and speed. In terms of technique, studies show that young athletes starting from Futsal are placed in positions requiring high technique when moving to 11-a-side football, specifically: 46.3% of Futsal athletes become midfielders, 19.4% wingers, 19.4% strikers and 14.9% defenders when they move to 11-a-side football [79].
Nogueira's (2017) [133] study showed that pre-season planning has a significant impact on physical fitness, recovery-stress status, signs of muscle damage and hormones in high-level Futsal athletes. Main results
In the study, pre-season Futsal performance improved in the YYIR2 and SJ (Squat Jump) tests. The improvement in the physical fitness tests was accompanied by increases in testosterone, CK, T/Cr and in most REST.Q scales. In addition, cortisol and stress recovery rate as measured by REST.Q scale decreased during the Futsal pre-season. Monitoring of LV in the Futsal pre-season increased in the first three weeks and decreased in the fourth week. The enhancement of LV after a period of decline has been reported in team sports.
Futsal statistics show that anaerobic metabolism often exceeds the lactic threshold during a match and blood lactic acid concentrations are 5.3–5.5 mmol/L [49]. It is clear that professional futsal athletes cover longer distances during high-intensity activities, so there is a real need to implement training programs to improve aerobic and anaerobic functions. Anaerobic function is what distinguishes futsal athletes (who have a higher anaerobic threshold) from 11-a-side football athletes.
Neuromuscular response: High-intensity efforts such as speed running, jumping and sudden changes of direction play an important role in Futsal. Several studies have shown that across different sports, stronger and more powerful athletes (i.e. with better neuromuscular development) tend to accelerate faster, jump higher and change direction faster [95]. In professional Futsal competition, sport-specific activities such as kicking or tackling are also influenced by the ability of a semi-professional athlete to generate higher levels of force and power. In addition to the increase in speed running time in training and competition, significant changes in neuromuscular function have been identified after a Futsal match. In particular, decreases in fitness and voluntary activation (i.e., signs of fatigue) have been observed after the match and are significantly associated with decreases in movement activities (high-intensity repetitive speed running and running). Therefore, coaches need to closely monitor training and competition, and promote recovery measures to minimize the risk of injury and be able to maintain peak neuromuscular performance of athletes throughout training and competition.
Biochemical responses: To better understand the demands of Futsal training and competition in practice and to take a more comprehensive approach to the stress caused by competition, several studies have found different biochemical markers after training and matches. The biomarker associated with the response to training is salivary immunoglobulin A (SlgA), whose decreased concentration can be a good indicator of overtraining [128]. In addition, the collection of unstimulated saliva samples to study the SIgA response in professional Futsal athletes showed a decrease in concentration, secretion rate and salivary flow after a Futsal match, leading to a risk of respiratory infections. The results of biochemical and metabolic tests as well as muscle damage caused by Futsal competition determined increased CK levels and decreased T/C ratio after the match from blood samples taken from the forearm vein.
In Futsal, different positions have different demands and characteristics, different levels of stress occur in the biochemical and immune systems, lactate dehydrogenase and IL-6 concentrations are significantly higher when compared to the above athletes after the match [50]; however, there is no difference in CK between positions. In practical terms, the results of the study showed that Futsal training and competition promote a decrease in plasma SlgA, increased muscle soreness, decreased CK levels after training and after 24 hours, causing different stress responses. These results should be considered and suggested to coaches, fitness experts and nutritionists in training to maximize performance for athletes.
1.3.3 Psychological characteristics of Futsal athletes
Sports psychology examines the psychological characteristics of Futsal athletes by applying the findings to their performances on the field. Psychological skills are trained to improve the performance of athletes. In general, sports not only improve performance but also other psychological parameters such as happiness, independence, interpersonal relationships and positive feelings. Although studies have examined psychological parameters such as motivation, anxiety, personality, team, leadership and injury recovery in soccer, there is still a significant lack of research in Futsal. Specifically, Futsal athletes must cooperate with the common goal of achieving team goals, assessing issues related to factors affecting performance.
Mokhtari et al. examined the relationship between Futsal coaching and team cohesion. Several studies concluded that coaching improves team cohesion through motivation (preparing the mind and improving self-confidence), tactical guidance (making important decisions and maximizing player performance), technical guidance (teaching skills and identifying technical errors), and character building (encouraging fairness).
An important factor affecting performance is anxiety which is often increased by the importance of Futsal and the difference between individual skills and the skills required for Futsal [173,24] suggesting that there are two types of anxiety, state and trait anxiety. State anxiety refers to a transient emotional state characterized by subjectively perceived feelings of tension and apprehension and increased autonomic nervous system activity, with competitive athletes experiencing higher cognitive anxiety than reserve athletes. Furthermore, athletes’ anxiety changes throughout the season as they show higher levels of cognitive anxiety in the first match and higher levels of Somatic anxiety in the final match. Anxiety is also associated with psychological distress in Futsal athletes, which often leads to them taking time off from the sport. However, coaches can reduce athlete anxiety by organizing training in realistic conditions and high-frequency matches. Furthermore, positive coaching responses and motivational environments that develop creativity by eliminating the fear of failure reduce anxiety and the risk of burnout. An interesting finding regarding the anxiety of Futsal athletes was that the study showed that Canadian Futsal athletes felt more anxious before a match while Japanese athletes felt higher anxiety after a loss. Furthermore, Canadians felt higher satisfaction after a win and lower satisfaction after a loss while Japanese athletes felt lower satisfaction after a win and higher satisfaction after a loss. These findings suggest that culture influences athletes' perceptions of anxiety [177].
1.3.4 Futsal Training:
The results showed that professional Futsal athletes had higher aerobic capacity, VO2max and aerobic threshold than 11-a-side football athletes. Specifically, the VO2max limit of athletes playing for a professional team was about 50-55 ml/kg/min [59]. Therefore, coaches must focus on training goals to increase aerobic capacity for their athletes.
Although many training programs do not use the ball to improve aerobic and anaerobic capacity, the results of an 8-week high-intensity training program with the ball improved both. Specifically, VO2max, anaerobic capacity, and fatigue improved by 9.6%, 10.7%, and 22.1%, respectively. This training program is recommended for the final stage of the preparation phase. However, today coaches prefer to use competition-like training that is beneficial for the overall development of Futsal athletes. Coaches can modify the field size, number of players, and rules of Futsal to improve aerobic or anaerobic capacity [45]
According to some studies, the distribution of LVĐ according to different training orientations depends on the training tools used in the preparation period. The results show a tendency to reduce non-specialized exercises (general training) by 95% in the initial stage, 74.1% in the basic development stage, 68.6% in the professional preparation stage and only 45.2% in the pre-competition cycles in the preparation period. At the same time, specialized exercises (professional preparation, supplementary, competition) increase and reach 5.0% in the initial stage, 25.9% in the basic development stage, 31.4% in the professional preparation stage and 54.8% in the pre-competition stage. Thus, in the preparation period of the professional Futsal athlete training process, aerobic glycolysis accounts for 54.9%, mixed 36.9%, alactic 5.2% and anaerobic glycolysis 3.0%.
The study by Freitas et al. (2011) [90] showed the effect of a training phase at the beginning of the competitive season to develop lower limb strength and its effect on physical performance of Futsal athletes. The results of a lower training volume and the application of lower limb strength training increased performance in power tests (vertical jump and velocity), maintaining performance in tests with high aerobic demands. The results of the study by Ricardo Augusto Barbieri 2016 showed that before and after a 12-week training phase affected the physical performance (aerobic and anaerobic) of professional Futsal athletes. Body composition decreased significantly: fat percentage (7.5%), improved flexibility (3.9%), aerobic (7%) and anaerobic (25%), after 4 weeks of additional speed endurance training, twice
one week, providing a simple and effective training regimen for Futsal athletes, which may have positive effects on cardiac autonomic regulation during the pre-season period without impairing psychophysiological stress.
Coaches should use competition-like exercises to improve technical, tactical and physiological characteristics under real-world conditions. When coaches increase the range of activity (increasing the size of the field) and reduce the number of players, they also increase the physiological demands of the players, which confirms that changes in the range of activity (increasing the size of the field), playing time and number of players affect the physiological demands of Futsal coaching. Several studies have compared the heart rate and playing skills of Futsal players after 10 minutes of play (4vs4, 3vs3 and 2vs2 in halves with a 4-minute rest between repetitions), with players showing the lowest heart rate in 4vs4 Futsal. Therefore, when coaches want to increase the intensity of training, they can reduce the number of players. A lower number of players also increases the technical demands of Futsal. On the other hand, duration does not affect the maximum heart rate of the players. Other studies have concluded that a 4vs4 game has similar physiological demands to a 3vs3 game with a shorter pitch (Balsom 1999) [45] and have also found that coach encouragement increases match intensity, heart rate and lactic acid concentration. This finding may be useful for Futsal games because there is a short coaching distance between the coach and the players on the pitch.
1.4 Basis for selecting content and timing of physical training supervision
1.4.1 Characteristics of physical activity in modern Futsal competition:
Futsal is a very popular sport with its own rules and differs greatly from football in terms of the rules of the game and tactics. However, no studies have investigated the relationship between the two sports, which is surprising given that Futsal is used in some countries as a football development tool, to develop the technical and tactical movements of young players. However, some studies have examined the relationship between Futsal and football players in terms of morphological characteristics, physical fitness and parameters, but there is a discrepancy between studies. Significant differences have been found between the morphological characteristics (mainly body) of football players