Abstract
To achieve good performance, athletes need to synchronize a series of movements in an optimal manner. One of the indicators used to monitor this is the order of occurrence of relevant events in the movement timeline. However, monitoring of this characteristic of rapid movement is practically limited to the laboratory settings, in which motion tracking systems can be used to acquire relevant data. Our motivation is to implement a simple-to-use and robust IMU-based solution suitable for everyday praxis. In this way, repetitive execution of technique can be constantly monitored. This provides augmented feedback to coaches and athletes and is relevant in the context of prevention of stabilization of errors, as well as monitoring for the effects of fatigue. In this research, acceleration and rotational speed signal acquired from a pair of IMUs (Inertial Measurement Unit) is used for detection of the time of occurrence of events. The research included 165 individual strikes performed by 14 elite and national-level karate competitors. All strikes were classified as slow, average, or fast based on the achieved maximal velocity of the hand. A Kruskal–Wallis test revealed significant general differences in the order of occurrence of hand acceleration start, maximal hand velocity, maximal body velocity, maximal hand acceleration, maximal body acceleration, and vertical movement onset between the groups. Partial differences were determined using a Mann–Whitney test. This paper determines the differences in the temporal structure of the reverse punch in relation to the achieved maximal velocity of the hand as a performance indicator. Detecting the time of occurrence of events using IMUs is a new method for measuring motion synchronization that provides a new insight into the coordination of articulated human movements. Such application of IMU can provide additional information about the studied structure of rapid discrete movements in various sporting activities that are otherwise imperceptible to human senses.
Highlights
Karate is a high-intensity combat sport that imposes high psychophysical and physiological demands on the athlete [1,2]
This paper has proposed a new method for measurement of the synchronization of the movement kinematics, using two IMUs mounted on the body of the athlete
The established differences indicate that the strikes that achieved a high maximal velocity of the hand have a different temporal pattern of relevant events when compared to the average and low-velocity strikes
Summary
Karate is a high-intensity combat sport that imposes high psychophysical and physiological demands on the athlete [1,2]. The reverse punch is a fundamental technique taught to all karate practitioners from the very beginning of their training It is executed from a guard position, with the hand opposite to the lead leg [7]. In relation to the inter-joint coordination, the motion is characterized by a consecutive proximal-to-distal sequencing [9,10], which enables the hand to be imparted with the energy of the preceding motion This is a pattern found in different striking or throwing-like movements [11] and is considered essential for generating high velocities at the endpoint of the kinetic chain, in this case, the fist. Permanent and periodical monitoring of the athletes’ technique can be considered a precondition for unhampered progression toward efficient execution of the technique in competitive settings [16,17]
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