Dr.Biol., Professor Yu.N. Romanov
PhD, Associate Professor A.S. Aminov
PhD, Associate Professor E.B. Perel'man
Postgraduate K.E. Ryabina
South Ural State University, Chelyabinsk

Keywords: hook kick, kickboxing, video captures, kinematics profiling analysis, striking velocity.

Background. Striking combat sports are highly demanding to a variety of aspects of athletic fitness. Some researchers [2-4] hold to the opinion that the technical mastery that largely secures success in fights is always based on due theoretical, psychological, tactical and physical fitness aspects, with special emphasis on the offensive punching actions which bring scoring points on the one hand and may even result, on the other hand, in the fight being won by a single powerful kick that not only brings a win but saves forces of the winner for the next fight of the tournament. The fighter’s mastery in throwing fast, strong and accurate strikes undoubtedly increases his winning chances in every fight. It is the biomechanical analysis on the whole and the striking action kinematics profiling analysis in particular that generate key data to rate the individual fighting skills including the key offensive actions [1].

Objective of the study was to profile the kinematics of an offensive right-hand hook to the head thrown by a skilled light-heavyweight kickboxer. 

Methods and structure of the study. The study was designed to obtain video captures of the right-hand hook to the head thrown by a subject light-heavyweight kickboxer qualified Master of Sport of Russia, a prize-winner of the Russian Championship in full-contract fights. The movement sequence was captured by a high-speed MIRO video camera (the US-made) mounted on a special 5-meter-high support with the objective lens directed downward on the kickboxer who performed the kick on the command of the cameraman, with the process being controlled by the computer keyboard. Special plastic markers with reflective coating were pasted on the right wrist, elbow and shoulder of the fighter to trace the striking sequence at the rate of 200 frames per second. The video data were processed by Star Trace 2D software toolkit of the Ultra Motion Pro FAST system.

Study results and discussion. Having processed the video capturing data, we obtained kinematic profiles of the right-hand hook performance sequence for the so-called swinging technique that implies the fist arching route to the target following the sharply-growing rotation radius. This rounded-motion striking technique, as compared to the classical hook and cross strikes, makes it possible to speed up the fist to the highest striking velocity. When analyzing the fist trajectories to the target as provided hereunder on Figures 1 and 2, we would note that the primary coordinates of the A point are insignificant for us in the case. It is only the х₁ – х₂ and у₁ –у₂ intervals – with the х₁ – х₂ representing the highest distance from the fist to the target line (i.e. the swing action amplitude), and the у₁ –у₂ showing the shortest distance from the fist prior to the striking action to the target point in space (e.g. the pad held by an assistant).

Figure 1. Fist travel trajectory in the standing right-hand hook performance sequence

Figure 2. Fist travel trajectory in the step-forward right-hand hook performance sequence

   In case of the standing hook, х₂ - х₁ = 390 mm and у₂ - у₁= 860 mm; and in case of the step-forward hook, х₂ - х₁ =412 mm and у₂ - у₁= 984 mm. These data show that the standing hook is performed in a more compact manner, with the fist sideward travel being 22 mm shorter versus that in the step-forward striking sequence; plus the target hitting distance is 124 mm shorter.

Having analyzed the data given in Tables 1 and 2 hereunder, we should note that the striking velocity is attained much faster in case of the standing hook, with the resultant velocity coming to as much as 13.1 m/s at the time point of t=0.25 s. In the next 0.025 s, the fist travel velocity reached the strike-specific maximum of 15.14 m/s. In case of the step-forward shot, the resultant striking velocity reached only 8,042 m/s at the time point of 0.25 s, and the maximum velocity of 16.28 m/s was achieved at the time point of only 0.31 s.

The axial constituents V_x and V_y of the resultant fist travel velocity were found to vary unevenly over the striking sequence time. In both versions of the hook, it was the V_y axial velocity (i.e. the progressive component of the striking sequence) that came first to the maximum. In the standing hook performance sequence, the V_y axial velocity was found to reach its maximum of 10.143 m/s at the time point of t=0.25 s; whilst the V_x axial component reached its maximum of 13.87 m/s at the time point of t=0.28 s.

Table 1. Variations of the axial components (V_x and V_y) of the resultant striking velocity V_рез in the standing right-hand hook performance sequence

Table 2. Variations of the axial components (V_x and V_y) of the resultant striking velocity V_рез in the step-forward right-hand hook performance sequence

The synergic muscular groups directly engaged in the right-hand hook performance sequence may be classified into the following two groups. Group one is responsible for the progressive component of the fist travel to the target, with the load being mostly controlled by the musculus triceps brachii; and group two performs the rotation component of the strike mostly controlled by the dorsal and pectoral muscles. If the striker were capable of harmonizing both synergic muscle group actions in such a way that both maximum striking velocities were achieved at the same time point, the resultant velocity could theoretically come to as much as 17.18 m/s (61.86 km/ hour) in the standing hook sequence and to 18.38 m/s (66.16 km/ hour) in the step-forward hook sequence – that would give the velocity growth by 13% in the both versions of the hook. The benefit may seem insignificant, but it should be remembered that velocity is squared in the kinematic energy formula and, consequently, the striking power is increased by 27% that is a quite significant growth.

It should be noted that the time interval between the peak points of the axial components V_x and V_y of the resultant striking velocity for the standing and step-forward hook sequences is estimated at 0.03 s in both cases. This fact brings up at least two questions. Does it mean that the subject fighter so strictly and automatically keeps this time interval in between the peak points of the axial components V_x and V_y for it was formed and fixed by his long-term practice? Or is it the cerebral cortex of the fighter that prevents the peaks from being overlapped by separating and sequencing the nervous impulses to activate first the synergic muscle group one and only then the group two when the fist is accelerated on the way to the target? Responses to these questions may hopefully be found in further studies that could be designed to:

1. Put together a set of technical exercises with the arm being fast extended in the elbow joint and raised horizontally, with the trunk simultaneously turned right-to-left and the right arm explosively thrown by the pectoral muscle action;
2. Put together a set of speed-strength exercises to make the relevant muscle groups fit for the explosive actions;
3. Complete the individualized technical and speed-strength training of the subject athlete(s) based on the prior hook performance kinematics profiling data;
4. In 4-6 weeks of the training process, make video captures of the right-hand hook performance sequence followed by the data processing and analyses using the relevant application software and hardware system; and
5. Rate the technical and speed-strength progress of the athlete(s) with an emphasis on the resultant striking velocity of the hook to hopefully find responses to the above questions.

Conclusion. The study and analyses of the striking sequence kinematic profiles made it possible to detect a temporal disharmony in actions of the synergized muscle groups involved in the swinging hand hook performance sequence. Coaching teams in their practical work are recommended to give a top priority to the reasonably grouped training methods to secure the synergic muscle group actions being highly balanced.

References

1. Donskoy D.D. Biomekhanika: uchebnik dlya institutov fizicheskoy kul'tury (Biomechanics: textbook for institutes of physical education) / D.D. Donskoy, V.M. Zatsiorskiy. – Moscow: Fizkul'tura i sport, 1979. – 264 p.
2. Matveev L.P. Vvedenie v obshchuyu teoriyu fizicheskoy kul'tury. Teoriya i metodika fizicheskoy kul'tury. Ch. 1. (Introduction to general theory of physical education. Theory and methods of physical education. Part 1.) / L.P. Matveev. – Moscow, 2002.
3. Ostyanov V.I. Boks: ucheb. posobie (Boxing: study guide) / V.I. Ostyanov, I.I. Gaydamak. – Kiev: Olimpiyskaya literatura, 2000. – 356 p.
4. Filimonov V.I. Boks. Pedagogicheskie osnovy obucheniya i sovershenstvovaniya: uchebnik (Boxing. Pedagogical grounds for learning and development processes: textbook) / V.I. Filimonov. – Moscow: INSAI, 2001. – 400 p.

Corresponding author: kickbox@mail.ru

Abstract
Objective of the study was to profile the kinematics of an offensive right-hand hook to the head thrown by a skilled kickboxer. We used MIRO video camera (made in the US) for the purposes of the study. The study data were processed by Star Trace 2D software toolkit to obtain the striking fist travel coordinates; velocity, acceleration rates and elbow joint angle variation rates. Analysis of the Vx and Vy axial striking velocities made it possible to detect a temporal disharmony in actions of the synergic muscle groups involved in the hook performance sequence. The temporal gap between the peak points of the axial constituents (Vx and Vy) of the resultant fist travel velocity for the right-hand hooks performed in standing or step-forward positions – was estimated at 0.03 s for both versions of the punch. The article offers solutions to the issues that came up in the analysis.