Futsal is an acyclic sport with high neuromuscular demands involving accelerations, decelerations, changes of direction, jumps, and kicks. At competitive level, players average more than 3000 meters and up to 26 sprints per match mostly at high intensities (15.5–18.3 km/h).1 In addition, futsal involves a variety of rapid decision-making situations, suggesting that in addition to physical ability, sustained attention and decision-making are also critical.1

A balance between external and internal training loads help athletes sustain the high neuromuscular/cognitive demand several times a week for an entire competitive season, which may last 36 to 44 weeks.2 Internal load, as defined by the athlete's responses to an external demand,3 can be estimated by perceived exertion and directly relates to physiological performance markers such as blood lactate concentration and heart rate.4 The perception of effort also depends on emotional reactions being influenced by conditions like mental fatigue.5,6 External load is related to the work imposed and performed by an athlete, often measured by exposure time, speed, distance, volume, or intensity of movement.2 The external load can be manipulated to promote changes in the internal load resulting in training adaptations.2 In this scenario, the monitoring and planning of internal and external loads are important components of futsal physical training, although they are not simple to determine, and there is little information about factors that influence internal loads in high performance athletes, especially during a whole competitive season.7,8

The number and concentration of matches over a period of time influences the perception of internal load,7 but also the different times of the season affect these loads differently between athletes according to their physical characteristics9 and aerobic capacity.8 Cognitive condition, mental fatigue and stress can also have a direct influence on physical capacity and perceived exertion.10 The determination of which neuromuscular and cognitive characteristics influence internal loads in cross-sectional analysis is limited because it might not be sensitive to the evolutions during repeated exercise sessions over a season. Tracking changes during the competitive season becomes more substantial to provide evidence that translates into the optimization of periodization processes and training schedules. After all, different of the observed for an exercise session, the season involves more fluctuations in external and internal loads.11

Whether the perception of internal load relates to physical and/or cognitive ability differently, and whether this relationship changes over a regular season are the questions that motivated our study. Although the literature provides evidence regarding training programs12 and effective methods for improving physical qualities common to futsal and similar sports,13 little is known about how physical and cognitive qualities can influence perception of internal load, especially at different stages of the season. Here we determine which variables can influence the internal load during periods of high and low internal load accumulated in a professional futsal team.

Table 1 presents the descriptive data of the parameters evaluated in the group of athletes.

In the period of low accumulated load, the total perceived effort and perceived effort per session showed a direct correlation with errors in the Stroop test (rho = 0.60; p = 0.048). Simple linear regression analysis determined that the amount of errors in the Stroop test explains 36.4% of the variance in total perceived effort and per session (Table 2).

In the period of high accumulated load, the total perceived effort and perceived effort per session showed an inverse correlation with jump power (r = - 0.721; p = 0.02). The multiple linear regression model determined that power explains 52% of the variance in total perceived effort and per session (Table 2).

In this study we determine which physical and cognitive characteristics influence the perception of effort in professional futsal athletes at different times of a regular competitive season. One of our main findings refers to the distinct influence of cognitive performance and jump power output at different times of the season on perceived effort. The monitoring of loads throughout the season allowed us to observe these relationships that have important implications for futsal training and competition. In addition, load monitoring routine has become popular in futsal, and the addition of some assessments at specific times of the season can provide important insights for coaches when defining training approaches as well as performance monitoring.

Futsal involves significant cognitive demand for decision making, focus of attention, and error minimization1. We found that selective attention capacity seems to have important relevance for perception of effort among futsal athletes during a period of low accumulated load. Athletes with less performance in selective attention task report higher levels of perceived exertion. Our findings are new to the literature, and future studies should focus on investigating the mechanisms that may explain this effect and also how this relationship can directly affect athletes' performance during the matches. In other sports conditions, cognitive performance involving for example selective attention has proved to be important for both performance and decision making.22 On the other hand, this type of relationship can be influenced by the athlete's fitness level.23 As the phase of low accumulated load was at the beginning of the season, it is possible that this relationship was not maintained at the end of the season because important indicative of physical conditioning showed important improvements at the end of the season (Table 1), most likely a result of training in previous weeks.24

In the period of high accumulated load, jump power seems to be the preponderant physical quality influencing the perception of effort in futsal athletes. While aerobic capacity and the ability to perform high intensity repeated stimuli are related to the perception of internal load15 our study points out that the ability to produce explosive force has a greater ability (greater than 50%) to explain internal charges at the end of the season. This relationship has important practical implications as the maximum sprints common in futsal1 require high power output capacity. In addition, power is increasingly being highlighted as a factor related to several important aspects of futsal, such as linear sprints and change of direction performance.25 In rugby athletes, it is observed that higher values of perceived effort are directly related to the incidence of non-contact injuries.26 As higher power values appear to decrease internal load, apparently higher power may also decrease the risk of non-contact injury due to residual fatigue. Thus, increasing power in futsal athletes seems to be beneficial both in terms of performance, due to increased strength and injury prevention, as well as being able to decrease perceived exertion and possible mental stress.

Our findings provide important and novel information that can assist in training programs especially in a period that is characterized by decisive matches and requires efficient methods. Plyometric trainings12 and resistance training with loads in optimal zones27 or near these zones28 should be encouraged at this stage as they are able to increase power output and, according to our results, decrease the perceived at a turning point in the season.

No significant differences were found in the values of strength and power when compared to the period of low and high accumulated load, indicating that even with few changes in these variables, power became determinant at the end of the season in this period of high accumulated load. Therefore, adopting a monitoring program for both power levels and effort perception levels is critical in a competitive, high-performance futsal environment where small changes in perceived effort levels can have a final outcome in power level produced, and directly interfere with performance at key moments of a sporting season.

Based on our findings, we recommend that cognitive characteristics should be considered during some periods of the sporting season, especially in the pre-season. Our findings indicate that power output should be determined and monitored throughout the season, during training sessions, and pre-competition, as it strongly related to the level of perceived exertion especially in the final phase of the season.

Over the course of a competitive futsal season various aspects of neuromuscular and cognitive function influence the perception of internal load, so we believe that especially at the beginning of the season coaches should perform cognitive assessments to determine levels of selective attention and decision-making skills, important skills in futsal performance and which may influence the perception of effort. Tests that use specific game situations should be encouraged, as well as assessments using quizzes and software.

Muscle power training should be used at all stages of the futsal season, including at the end of the season, where the impact of this physical quality can be a determining factor in perceived effort.