Background: In combat sports of percussion (kicks and punches), the velocity of the technical actions are a differential to the sporting success. Technique and strategy chosen by the
athlete are velocity dependent. The quick access to the cinematic variable, is a great tool to the coach and their athletes to the training of planning. So, in order to assess the athlete’s velocity
performance, the Virtual Instrument System (VIS), named Nokachi System, described in this article, was developed.
Methods:The VIS was built integrating a triaxial accelerometer CMA 3000 – D01 (VTI Technologies) included at Chronus EZ 430 device, Texas Instrument, with a graphical user interface
developed in LabView plataform. The VIS presented relative error of 1%, relative reliability and repeatability of 0.59% and 66.6%, respectively. It was evaluated forty-five karate athletes, male
gender, 23 ± 3.4 y.o, 75 ± 12.3 kg, 1.74 ± 0.21 m, 13.2 ± 2.1 % fat mass, splitted into three groups: (G1) fifteen athletes of beginner level (from white up to red belt), (G2) fifteen for intermediate
level (from orange to purple belt) and (G3) fifteen for advanced level (from brown up to black belt). The accelerometer was placed on the wrist of the athletes and they performed five punches (gyako
zuki) with the dominant limb, with an interval of 5 s. of rest. The bandwith of the acceleration signal varied from 100 Hz up to 400 Hz. Velocity values were obtained by calculating the modulus for x,
y and z velocity vectors of the punches 2 (P2), 3 (P3) and 4 (P4). We applied Manova test, with the post hoc Bonferroni test (p<0.05).
Results: The maximum velocity among all punches performed were 12.1 ± 2.3 m/s. One by one, the results were: P2 = 10.7 ± 1.3 m/s; P3 = 12.5 ± 3.5 m/s; P4 = 11.9 ± 4.5 m/s for all the
groups. Comparing the groups, we observed higher velocity (P3 and P4) in G3 (F(3,21) = 34,2; p=0,001) than in G1 (p=0,002) and G2 (p=0,001), indicating that senior athletes have higher speed stroke.
There were difference between G1 and G2 (F(3,21)=25,2; p=0,02), specially for the P2 (p=0.02), with higher stroke speeds to G2.
Conclusions: The developed VIS estimates the execution velocity of punches in combat sports, especially for gyako zuki punch in karate. In the assessed sample, athletes of advanced
level have presented higher velocity on punch execution. The VIS is an important tool to the coaches and athletes with a good biofeedback in the training sessions, facilitating the training