# Reaction Time and Postural Control Under Dual-Task Conditions in Brazilian Jiu-Jitsu Athletes
## 2 Materials and Methods  
### Participants and Procedures  
This study involved 31 participants, consisting of 15 Brazilian Jiu-Jitsu athletes (9 men and 6 women) with an average age of 26.67 \(\pm\) 3.57 years, a body height of 171.20 \(\pm\) 8.49 cm, and a body mass of 68.32 \(\pm\) 10.71 kg. These athletes had an average of 5.73 \(\pm\) 5.28 years of training experience. The control group comprised 16 individuals (10 men and 6 women), with an average age of 25 \(\pm\) 1.80 years, a body height of 178.62 \(\pm\) 7.57 cm, and a body mass of 78.29 \(\pm\) 13.25 kg.  
Athletes were included based on the following criteria: at least one year of non-professional Brazilian Jiu-Jitsu experience (defined as training without competition participation); no orthopedic or physiological injuries; a training frequency of 3-4 times per week; and no chronic diseases, disabilities, or pain disorders. For the control group, inclusion criteria included the absence of orthopedic injuries or neurological conditions that might interfere with postural stability testing, as well as regular participation in recreational physical activities (such as running, cycling, or walking) several times per week.  
Before the measurements, all participants were informed about the experimental procedures. Both athletes and control participants took part in this study during the afternoon, between 4:00 and 7:00 p.m. Additionally, they attended the testing sessions before their training, ensuring they were well rested. This approach effectively minimized the potential impact of fatigue and prior physical exertion on the study outcomes. The measurements were conducted on days prior to training and divided into two parts. The first part of this study measured reaction time using the FitLight Trainer system (FitLight Sports Corp., Kingston, ON, Canada) (Figure 1A). The FitLight Trainer system is a tool designed to measure reaction time by utilizing a series of eight interactive, wireless lights. These lights can be placed in various positions and are activated in random sequences. Participants are required to react as quickly as possible by deactivating the lights (usually by touching or pressing them) when they light up. In this study, the protocol was carried out in standing and sitting positions (Figure 1B,C), with participants positioned in front of the wall-mounted lights. In both positions, they could comfortably reach each LED light with their writing hand without leaning forward. During a 60 s task, participants responded to light signals by touching the illuminated lights, while a dedicated program recorded and calculated reaction time and the total number of switched-off lights. In this system, reaction time was measured by recording the duration between the activation of a light and the participant's response to deactivate it.  
The second part of the measurements assessed postural control using the STANIAK JB platform (100 Hz). Each participant completed four trials, each lasting 30 s, with a one-minute break between trials. (1) Bipedal standing (2 eo): participants stood barefoot, arms at their sides, eyes open, and focused on a fixed point at eye level. (2) Single-leg standing (1 eo): participants stood on their non-dominant leg, determined by their preferred kicking leg. (3) Bipedal standing with visual tracking (2 eos): participants stood, following an irregularly moving dot on a screen located 190 cm away at eye level. (4) Single-leg standing with visual tracking (leos): participants stood on one leg, following an unpredictable moving dot on the screen.