Aerobic and anaerobic capacities in determining adolescent futsal players’ performance levels

Futsal is characterized as a high-intensity sport. Thus, aerobic and anaerobic capacities are essential factors for supporting athletes' performance when competing. Data related to adolescent futsal players in Indonesia still lacked. Therefore, this research objective was to determine how much aerobic and anaerobic abilities became the predictors of futsal athletes’ performance levels. The research method was observational research with a quantitative approach. The research subjects consisted of 15 Regional Training Center (PELATDA) athletes and 15 non-PELATDA athletes from West Java with an average of (age= 18.23 ± 1.13 years old, height= 170.23 ± 3.82 cm, body weight 59.57 ± 5.28 kg, BMI 20.56 ± 1.82 kg/m, and FAT 10.05 ± 1.29%). The results showed that body mass, body composition, VO2max, peak power, vertical jump, and fatigue index of PELATDA athletes were better than non-PELATDA athletes. Thus, this research could provide an overview for coaches regarding the aerobic and anaerobic capacities standards of adolescent futsal players and could be used as a reference in making an exercise program to improve athletes’ aerobic and anaerobic capacities.


INTRODUCTION
Futsal is an intermittent high-intensity sport that requires players to perform a series of intense activities repeatedly (e.g., sprinting, change of direction, accelerated kicks, decelerations) (Spyrou et al., 2020). It can be seen from previous research, which reported that during a match, futsal players could cover a distance of 3000-4500 m Barbero-Alvarez et al., 2008). Furthermore, 26% of the total distance traveled was done with high-intensity levels ranging from 86% to 90% of maximum heart rate (Caetano et al., 2015;Doğramacı & Watsford, 2006).
The rapid changes in the futsal game required athletes to maintain the Jurnal SPORTIF: Jurnal Penelitian Pembelajaran,7 (3)  best possible intensity when playing (Junior et al., 2017). These actions were punctuated by short recovery periods, with low-intensity actions or pauses. 75% of game action lasted approximately from one to 18 seconds.
This result suggested that anaerobic strength might be necessary for success in futsal (Álvarez et al., 2009).
Research conducted by Juniarsyah et al. (2019) revealed that the average aerobic endurance (VO2max) of professional futsal players from Indonesia was in the range of 45-52 ml/kg/minute. Meanwhile, professional futsal players from Latin America had VO2max values ranging from 60-70 ml/kg/minute Sekulic et al., 2020;Stubbs-Gutierrez & Medina-Porqueres, 2020). The difference in VO2max value was very far compared to professional athletes from Indonesia.
Thus, this difference could be used as a standard for coaches to improve their athletes' condition. It was vital because good aerobic endurance could support the accuracy of passing, acceleration, sprinting, and kicking (Astagna, 2010). Thus, the physiological characteristics of athletes, such as the aerobic and anaerobic capacities of futsal players, must be considered to maintain good playing performance and support a team to achieve success in competing (Astagna, 2010).
Besides aerobic and anaerobic capacities, anthropometric characteristics such as height, body mass, and body composition are other essential components that futsal athletes must possess. An example is athletes who have excessive body fat can interfere with performance in team sports (Nikolaïdis, 2012). In contrast, a more significant percentage of skeletal muscle mass tends to improve sports performance as it contributes to energy production during high-intensity activities and increases the strength-producing capabilities of athletes (Nikolaïdis, 2012;Sekulic et al., 2020;Vila Suárez et al., 2008).
The very dynamic development of futsal in Indonesia encouraged further research on futsal, especially for adolescent futsal players.
Research on aerobic and anaerobic capacities as predictors in determining the adolescent futsal players' performance has not been done much. The latest research only discussed anthropometric profiles and body composition in young football athletes (Bernal-Orozco et al., 2020).
Meanwhile, no one has researched aerobic and anaerobic capacities yet.
Therefore, it was necessary to prepare young players to have almost the same abilities as professional players to find out to what extent the differences between young futsal players could help the team and coaches develop training strategies. In addition, this research was expected to provide a more objective understanding of the talent scouting program and the young futsal players' performance. Thus, this research objective was to determine how much aerobic and anaerobic capacities became predictors of adolescent futsal players' performance levels.

Anaerobic Capacity (Peak Power)
Anaerobic endurance data was collected using the RAST (Running-Based Anaerobic Sprint Test) method. Athletes had to sprint 35 m as much as six times with an interval of 10 seconds between sprints.
The purpose of this RAST was to see the peak power of each athlete.
The timing was recorded for each sprint using a stopwatch (Casio HS-80TW, Shibuya, Tokyo, Japan). Power in Watts (W) for each sprint was calculated based on body mass (BMI) in kilograms (kg) and distance (35 m) to the power of two. After that, this result was divided by the time of each sprint, in seconds (s), to the power of three. As an example; Peak Power = body mass (kg) × distance (m)²/time (s)³. The highest power value produced in a sprint was considered peak power. Meanwhile, assessment of the fatigue index (FI) was done by subtracting the maximum power minus the minimum power then dividing the total time from six sprints, for example, was (maximum power -minimum power)/ total time of six sprints.

Vertical jump
Jump height measurements were assessed using Vertec (SPRI Furthermore, researchers used a vertec tool in the vertical jump test to see the highest hand reach when making a jump.

Data Analysis
The presentation of the data was displayed in the form of the mean value and standard deviation. This research used a one-way analysis or one-way Anova test, which compared PELATDA and Non-PELATDA futsal

RESULTS
The results showed that the mean (±SD) of Age and Body Weight between the two groups did not show a significant difference, but the weight of PELATDA athletes was lower than the weight of non-PELATDA athletes. Furthermore, significant differences were seen in the means of the height, FAT, and BMI of the two groups. The Pelatda athletes had a higher height but lower FAT and BMI rather than the non-PELATDA athletes (see Table 1). The results in Table 2 showed that the aerobic ability marked by VO2max between the two groups showed a significant difference (p=0.002), where the PELATDA athletes had a higher VO2max value compared to non-PELATDA athletes. The next significant difference was an anaerobic capacity, characterized by peak power, vertical jump, and fatigue index.
The three variables showed that PELATDA athletes were superior to non- The research results conducted by Milioni et al. (2016) revealed that being overweight was associated with a person's level of physical fitness. Athletes with a higher BMI and FAT showed decreased physical fitness compared to those with a higher BMI and low FAT. Although PELATDA and non-PELATDA athletes showed normal BMI and FAT, significant differences between the two groups affected the athletes' physical fitness. It can be seen from the VO2max value of the two groups, where the PELATDA athletes had a higher VO2max value when compared to the VO2max value in the non-PELATDA group (see Table 2).
Furthermore, the average height in both groups was within the normal population in Indonesia (Riskesdas, 2018). Although PELATDA athletes' height was higher than non-PELATDA athletes', this research results differed from the results of research conducted in Brazil and Spain, which showed that the average height of semi-professional athletes from these two countries was on average 174 cm (Campos et al., 2021;Romero et al., 2020;Sekulic et al., 2020). However, in futsal, no research concluded the correlation between height and performance in the field.
It was different from football, swimming, volleyball, and basketball, which positively correlated height and player performance on the field. Thus, based on these research results, the researchers had not been able to explain the phenomena yet (Bernal-Orozco et al., 2020).
The difference in aerobic capacity was due to the different frequency and duration of exercise between the two groups. PELATDA athletes practiced eight sessions a week, with the duration of each training session lasting 90 -120 minutes. In comparison, non-PELATDA athletes only exercised five sessions a week with a duration of 90 minutes. The research results supported previous research conducted by Álvarez et al. (2009), which suggested that athletes who did nine training sessions with 90 minutes a week could increase their aerobic capacity.
Furthermore, regarding anaerobic capacity when viewed from a physiological point of view, it was reasonable to hypothesize that the vertical jump test had a strong relationship with the athlete's peak power.
It was due to the primary energy metabolism pathway required during the action of the two tests, namely by using ATP-PC (Adenosine Triphosphate-Phosphocreatine), the higher the vertical jump, and the higher the peak power or leg muscle Power (Fukutani et al., 2021).
In addition, the 35-meter sprint speed was tested using RAST could be increased by training that required a high level of strength development, such as jump training. Thus, it showed that the height of the vertical jump was related to the athlete's peak power (Sales et al., 2018).
The level of athletes' fatigue, marked by the fatigue index (FI), represented how the strength or power level would decrease in the athletes' performance (Álvarez et al., 2009). The lower the FI-value, the better the participants' ability to maintain their performance, and vice versa. Athletes with high FI-values might need to increase their anaerobic capacity to maintain fatigue levels (Queiroga et al., 2013). However, the FI variable in both groups in this research was still at the threshold value (<10%) so that both groups were considered still able to maintain their level of fatigue (Queiroga et al., 2013).
Aerobic and anaerobic capacities to perform repetitive high-intensity activities were necessary components for physiological fitness in adolescent futsal players. Thus, with an excellent level of aerobic capacity, futsal players could perform intense, repetitive movements from the beginning to the end of the match and improve the recovery mechanism after several days of playing in matches (Romero et al., 2020). Thus, the research results could be used as an illustration for sports coaches and practitioners to evaluate performance in futsal matches and play a role in distinguishing well-trained futsal players or not. The research results showed that the value of aerobic and anaerobic capacities in PELATDA athletes was still relatively low for the size of semi-professional players.
Therefore, a more intense exercising program and additional adequate nutritional intake for futsal players, especially in this research, must be programmed by the coach to impact later the aerobic and anaerobic capacities of adolescent futsal players.

CONCLUSION
This research concluded that PELATDA athletes had better aerobic and anaerobic capacities than non-PELATDA athletes. However, these results were still far from being compared to semi-professional athletes.
Thus, the research results could provide an overview for coaches about the aerobic and anaerobic capacities standards of adolescent futsal players and could be used as a reference in making an exercise program to improve the aerobic and anaerobic capacities of futsal athletes.