THE APPLICATION OF FITLIGHT TRAINER SYSTEM IN SPORTS

The purpose of this systematic review is to point out the application of the Fitlight trainer system in sports. The following electronic databases were used to search the literature: Google Scholar, PubMed, Medline, Mendeley, 2014-2020. Following the selection procedure according to the relevant criteria, 22 studies were selected as fit to needs of this systematic review. A review of researches that used the Fitlight training system in sports has revealed a rather heterogeneous selection of topics. The results obtained are classified according to the sports in which the research was conducted. The results summary provided us with the insight into the multiple uses of the Fitlight system in sports as a training and measurement tool. It can be used in both individual and team sports. It can test sensory-cognitive and various motor skills: reaction speed, speed of single movement, speed of running, agility. Based on all of the information provided, the possibility of multiple applications of the Fitlight system in sports was highlighted.


INTRODUCTION
It is well known that different audio and visual signs are used in order to train the speed of athletes' reaction, but experts have sought to advance this field with certain technical solutions. The former Danish handball player, Rasmussen, invented the Octopus Trainer in 2007, which is the predecessor of the Fitlight system and the two are very much alike (Stack, 2020). From the initial model, certain modifications occurred, the system became easier to use, switched to wireless mode, etc. and so in 2012 the Fitlight system gets its present appearance and was released as a new product in the same year. The Fitlight trainer system (FTS) is a unique system for training speed of reaction in athletes. It consists of LED markers controlled by a tablet controller (Mackala, et al., 2020;Schelly, et al., 2019). The Fitlight system consists of 8 markers that are used as targets for the athlete, as he/she seeks to activate or deactivate them as needed. This training system is designed to collect human performance data related to visual, cognitive, and dynamic reactions. It is portable and easy to set up and use, making it a great tool for both training and testing (Fitlight, 2020).
As a fairly new product on the market, the Fitlight system has so far been put in a little use in scientific research in the field of sports. Currently, there are only about 30 available studies in which this instrument has been used. It is mainly used as a measuring instrument, although its creators emphasize that it can also be used as a training tool to improve performance, primarily speed of reaction and sensory-cognitive abilities.
This indicates that using the Fitlight system in different sports and with different research, topics could lead to some answers in this field. In this regard, this review aims to point out the application of the Fitlight system in sports.

Source of data and strategies
The following electronic databases were used to review the literature. Searches were made using the following keywords: Fitlight, sport, athlete. The search strategy was modified for each electronic database, where possible, to increase sensitivity. All titles and abstracts have been reviewed for potential papers that could be included in the systematic review. Also, reference lists of the previous original researches were reviewed. Relevant studies were obtained after detailed examination, provided they met the required criteria to be included. Exclusion criteria where: Papers that have not been published in English, research that has not been presented in its entirety (only abstracts), study in which the results have not been clearly presented, repeated research ... The strength training program has led to a significant improvement in physical parameters. Therefore, it is recommended to integrate strength exercises as a regular regimen in the physical conditioning protocol in order to develop the physical performance of young swordsmen.

RESULTS
Vargas, The block periodization training model provided an improvement in the fitness and motor skills of taekwondists. The group using a three-week tapering strategy, which implied a 50% reduction in training volume, performed better in all measured parameters than the group that trained regularly. Coh,

DISCUSSION
The review included 22 studies that addressed the use of the Fitlight system in sports. There are only two surveys from years 2014-2015. by the same group of authors, while all other studies from the period 2017-2020. This indicates that these are fairly recent studies because the Fitlight system itself is a new device on the market. The survey included a total of 975 subjects in the aforementioned 22 studies, representing an average of close to 44 participants per study. There were at least 12 examinees in one survey and a maximum of 159. As many as 15 studies were conducted on male and female athletes together, 6 papers were for men only, while only 1 study was based solely on female participants. When it comes to the Fitlight system, 7 or 8 electrodes were used in most studies (in 15 papers). The electrodes were most commonly placed on cones, as they were reaction and agility tests (in 9 studies), then vertically mounted on the wall (6 studies), as well as horizontally on the table (3), which examined the reaction rate of the upper extremities. Other studies did not describe the details of the test protocol. In five studies, the average age of participants was below 18 years, while all other studies ranged from 18-25 years, and in one study the average was over 25 (27.4 years). During the systematic review on the application of the Fitlight system in sports, the predominantly examined category were athletes (7 studies), which includes athletes from different sports classified into one category. This is followed by research on football players (5), handball players (2), taekwondists (2), badminton players (2), and one study each on karate players, swordsmen, hockey players, and rugby players.
Athletes have been found to perform better than non-athletes as well as men performing better than women, and this is applied for both planned and unplanned agility tests (p<0.05) (Coh, 2019;Coh, et al., 2018). Better time measurements for men can be explained by greater motor potential, especially in terms of explosive power, reactive power, acceleration, and deceleration (Coh, et al., 2018). Existing findings suggest that planned and unplanned agility are two distinct and independent skill domains that define responsiveness. Also, the more complex the structure of the movement, the greater the difference between planned and unplanned agility among samples of athletes and non-athletes (Coh, 2019;Coh, et al., 2018), further implying that these characteristics must be treated separately. Mackala et al. (2020) point out that team athletes have a stronger connection between sprint and planned agility (CODS) in frontal configuration (FR) (r=0.62) and lateral configuration (LA) (r=0.60), while individual athletes have a stronger correlation between unplanned agility and sprint and jump performance. The visual response times of athletes from different sports are very different and specific, so it is impossible to determine differences between them (Millikan, Grooms, Hoffman, & Simon, 2019; Örs, Cantas, Gungor, & Simsek, 2020). In general, it is suggested that exercises to improve reaction time should be included in the training plan, with specific technical-tactical tasks for a particular sport. One study conducted a program for prevention of anterior cruciate ligaments and found that athletes who showed the greatest reduction in knee joint amplitude showed greater hip adduction and showed appropriate improvements in hip and knee flexion kinematics, which could help therapists identify and determine individual training for those at higher risk of injury (Taylor, Nguyen, Shultz, & Ford, 2018). Wilke, Vogel, & Ungricht, (2020) found that all but one test dimension showed satisfactory reliability (ICC 0.60-0.94, p<0.05). The conclusion is that the tests presented show moderate to high reliability and can, therefore, be used for scientific testing.
The sport that has had the most testing with the Fitlight system is football. In their work, the Slovenian authors found that both groups were slower on the test with visual signals compared to the test without (T>TVS) (~2.5s, p<0.01), and those elite footballers performed all the tests faster than amateur footballers (~3s, p<0.01). The average number of visual errors was significantly lower in the group of elite footballers (FE) relative to amateurs group (FA) in all tests (p<0.01). The results demonstrated the importance of assessing dribbling along with visual stimuli in FE and FA (Bekris, Gissis, Ispyrlidis, Mylonis, & Axeti, 2018). Snyder, & Cinelli, (2020) found that trained footballers achieved significantly lower levels of dicplacment center of pressure (dCOP) than non-athletes in tests, especially in medium-lateral test (ML) (p=0.005). Not only do footballers show better balance control, but also better proprioception and use of sensor-motor information, as well as improved executive control functions. Rauter et al. (2018) point out that agility in football represents different physical qualities and therefore should be diagnosed and developed with separate assessments and training sessions. The authors agree that reactive agility is a dominant feature in football and therefore needs to be developed through a different, more specific training regime (Rauter, et al. 2018; Zakharova, Mekhdieva, Krasilnikov, & Timokhina, 2019). In one specific study concerning football, the authors found that differential learning (DL) achieved a greater improvement over contextual interference (CI) in visuomotor response time (VMRT) after training, but after one hour of rest, differences were no longer observed. Both groups showed improved motor control, as evidenced by a stronger synergy of post-training movement, with no difference between DL and CI (Serrien, et al. 2019).
Only two studies were performed in handball, badminton, and taekwondo. Handball players achieved significantly shorter total reaction times (TT) than non-athletes (1:43:13-41:56, p<0.01). In other words, handball players have a higher level of ability to maintain attention than non-athletes (Zwierko, Florkiewicz, Fogtman, & Kszak-Krzyżanowska, 2014). Florkiewicz, Fogtman, Lesiakowski, & Zwierko, (2015) showed that a six-week training program showed that perceptual skills are susceptible to change and can be improved by appropriate training. The Dutch authors have found that the response time measured by reaction time test for badminton players (BRIT) can serve as a starting point in a training program aimed at improving the performance of badminton players. The aim was to examine the reproducibility and validity of the inhibitory control assessment, and it seems that BRIT (badminton reaction inhibition test) can be considered as a reproducible and valid measure of reaction time in badminton players (Van de Water, Huijgen, Faber, & Elferink-Gemser, 2017). Guðmundsdóttir, (2017) found differences in several physical fitness tests between elite group of badminton players (BP) compared to semiprofessional badminton players (BS) and recreational badminton players (BR) groups BP>BS and BR in counter movement jump (CMJ), agility test (T505), grip strength (GS), maximum rate of oxygen consumption (TVO2) (p<0.05), but this difference between the elite and sub-elite group was not significant in any of the motor tests. Also in the same study, a moderate to very strong correlation was found between four physical fitness tests in men and five tests in women. When it comes to taekwondo, Vargas, & Jiménez, (2018) examined the training model using block periodization and found that it provided an improvement in the fitness and motor skills of the taekwondo.
The group using the three-week tapering strategy, which implied 50% less training, achieved better results in all measured parameters than the group that regularly trained in motor ability (MS) (p=0.01), squat jump (SJ) (p=0.01), countermovement jump CMJ (p=0.01), countermovement jump with free arm (ACMJ) (p=0.01), depth jump (DJ) (p=0.01) (Vargas, & Jiménez, 2018). Group analyses showed no significant association between sleep efficiency and physical performance. The individual analysis showed that the performance of three participants was related to sleep efficiency. Current evidence do not support the general claim that sleep efficiency is related to physical performance (Vargas, & Jiménez, 2020).
Other sports represented had one study each: karate, rugby, fencing and ice hockey. The results show that long-term karate training improves reaction time among young people and that there is a significant difference between elite athletes and beginners in karate when it comes to reaction time (RT) (p<0.001). This study demonstrates that Fitlight trainer system (FTS) can be a potentially standardized means of estimating reaction time by light stimulation (Liu et al., 2019). Mitchell, & Cinelli, (2019) have shown that Go/No-Go tasks driven by choice and speed of decision can objectively identify differences among young athletes with and without prior sport related concusion (SRC). It should be noted that defects in visual-motor control and balance may persist after clinical recovery. Smith (2017) found in his study that most positive anthropometric and physiological adaptations occurred during the first half of the season when rugby player conditioning training was focused on technical skills (p<0.001). The reason for the increased maximum aerobic power and agility may be that rugby players become leaner and adapt to fitness training. Middle season (MiS) and post season (PoS) led to fat reduction, increased agility, speed, and maximum oxygen consumption. The research, which was based on the training of fencing athletes, concluded that the strength program led to a significant improvement in the physical parameters of athletes. Therefore, it is recommended to integrate strength exercises as a regular regimen in the physical conditioning protocol to develop the physical performance of young fencing athletes (Tsolakis, Tsekouras • The presented FTS tests show moderate to high reliability (Wilke, et al., 2020). • FTS can be a potentially standardized tool for estimating reaction time by light stimulation (Liu et al., 2019).
A review of the research so far provides insight into the widespread use of the Fitlight system in sports. However, given that it is a fairly new instrument, it is clear why there are very few studies published. So many popular sports such as basketball, volleyball, athletics, swimming and more do not have any studies using the Fitlight system. This review shows that the Fitlight system can be used in various ways and in different sports. It can be used in both individual and team sports. It can test sensory-cognitive and motor skills: reaction rate, speed of single movement, speed of running, agility. Based on all the information provided, the possibility of multiple applications of the Fitlight system in sports was highlighter.

CONCLUSION
During a systematic review on the application of Fitlight system in sports, few studies were found. The most tested category are athletes, namely represented by a group of young athletes from different sports. Also, it should be noted that in many popular sports there are still no studies using the Fitlight system, which is understandable, as it is a fairly new instrument.
Based on a survey that was quite heterogeneous in the choice of topics, type of sports, participants, etc. different conclusions were also drawn, which are, in this chapter, separated and classified according to sports categories.
Numerous conclusions have been established and they can be presented according to the following criteria: (a) Studies which involving combined groups of athletes, identifying: • Athletes score better than non-athletes on change of direction of speed pre-planned (CODS) and reactive agility (RS) tests. • Men score better than women on CODS and RS tests. • CODS and RS are two independent skill domains that define responsiveness.
•The more complex the movement structure, the greater the difference between CODS and RS.
• Team athletes have a stronger correlation between sprinting and CODS. • Individual athletes have a stronger link between RS and sprint performance. • The visual response times of different athletes are very different and specific. (b) Studies dealing with the application of FTS in football have concluded: • Soccer players are slower on the test with visual clues than on the test without them. • Elite football players conducted all the tests faster than amateur football players. • The number of visual errors was lower among elite football players compared to amateurs.
• Football players achieved a significantly lower level of movement of the center of mass than non-athletes.
• Football players showed better balance, proprioception and the use of sensor-motor info. • Differential learning (DL) achieved greater improvement over contextual interference (CI), but no difference after 1h.
(v) Studies addressing the use of Fitlight trainer system (FTS) in other sports have concluded: • Handball players achieved significantly shorter reaction times than non-athletes. • Perceptual skills are subject to change and can be improved by training. • Elite badminton players scored better on the motor tests. • Block periodization influenced the improvement in conditioning and motor ability. • The group using 3-week tapering was better in all parameters. • There is no relationship between sleep efficiency and physical performance. • There is a significant difference between elite karate players and beginners in reaction time (RT). • Go / No-Go objectively identifies differences among young athletes with and without SRC (sport related concussion). • Most positive physiological adaptation occurred during the first half of the season. • The strength program has led to a significant improvement in the physical parameters of athletes.
• FTS is a potential standardized tool for estimating reaction times. • The tests presented show moderate to high reliability. • Badminton reaction inhibition test (BRIT) can be considered a repeatable and valid measure of reaction time.
In conclusion, based on all the information provided, it is clear that the Fitlight system can be used in various ways and in different sports. It can be used in both individual and team sports. It can test sensory-cognitive and motor skills: speed of reaction, speed of single movement, speed of running, agility. Based on all of the information provided, the possibility of multiple applications of the Fitlight system in sports was highlighted.