Postgraduate А.V. Illarionova¹
Dr.Med., Professor L.V. Kapilevich^{1, 2
1}National Research Tomsk State University, Tomsk
²National Research Tomsk Polytechnic University, Tomsk

Keywords: coordination, electromyography, training session, accuracy, shot, throw 

Introduction. Training process results and success in any movement sequence mastering process will largely depend on the intrinsic motor coordination qualities of an athlete that may be described as the ability to control muscular tension as required by the concrete movement sequence performance process [1, 3]. In a movement system control process, top priority role will be played by the self-control ability based on the relevant clear motor-sequence-specific notions [2]. It is the bioelectric activity indices of the muscles that are rated among the most important criteria of the necessary motor skills formation process [4, 5].

Objective of the study was to explore the inter-muscular coordination pattern in accurate ball shooting skills formation process.

Methods and structure of the study. Subject to the study were 20 young women aged 18-20 years. The women were trained to throw a tennis ball with the right hand to the target at distance of 3 meters from the legs-apart sitting position, making 2 eyes-open and 2 eyes-closed ball shooting attempts. Accurate hits scored 3 points, deviations up to 0.5 meter from the target scored 2 points, and deviations within 0.5 to 1 meter from the target scored 1 point, with the average score for 2 attempts being recorded. The training course was scheduled to include 12 training sessions of 3 times per week for one month. Prior to and after each training session, the interference surface electromyograms (EMG) of the musculus biceps brachii and musculus triceps brachii, musculus flexor carpi radialis and musculus extensor carpi radialis were recorded using the Neuro-EMG Electromyograph System (made by NeuroSoft Ltd.) and the BTS FREEMG 300 Unit (made by BTS Bioengineering Company).

Results and discussion. The eyes-open ball shooting attempts prior to the training course scored on average 1.75±0.50 points; and the eyes-closed ball shooting attempts scored on average 2±0.25 points, with the differences of the impulse amplitudes in the extensor vs. flexor muscles of shoulder and wrist being found insignificant. After the training course, the EMG amplitudes of both the shoulder and wrist muscles showed significant differences, whilst the shooting scores were 1.75±0.75 points and 1.5±0.5 points, respectively. That means that the shot accuracy was found to sag for the eyes-closed attempts after the training course, i.e. in the situations when signals from the visual analyzer system were lacking.

After the training course, higher EMG amplitudes and frequencies were recorded in the eyes-open ball shooting attempts; and it should be noted that it were musculus biceps brachii that showed the lowest EMG amplitude and musculus extensor carpi radialis that showed the highest frequency prior to the training course; whilst after the training course, no significant differences in the amplitudes of virtually all these muscles were found except for the musculus triceps brachii which showed the highest amplitude; and it were the musculus biceps brachii and musculus extensor carpi radialis that showed the highest frequency after the training session (see Table 1 hereunder).

Table 1. Bioelectric activity indices of the right hand muscles prior to and after the ball shooting training course, М±m

* Significant difference after the training course, p<0.05

The eyes-closed ball shots after the training course were associated with the higher EMG amplitudes in the musculus triceps brachii and musculus extensor carpi radialis and lower impulse frequencies in the musculus biceps brachii. Prior to the training course, the highest EMG amplitudes were recorded in the musculus extensor carpi radialis and musculus flexor carpi radialis; and after the training course, the highest EMG amplitude was recorded in the musculus triceps brachii, in contrast to the lowest EMG amplitude for the musculus biceps brachii in the ball shooting sequence. Prior to and after the training course, the highest impulse frequency was recorded in the musculus extensor carpi radialis and the lowest one – in the shoulder muscles (see Table 1).

The study found that activated first in the most cases in the ball shooting movement sequence from the starting position “with bent shoulder and forearm” were the musculus triceps brachii and musculus extensor carpi radialis with an insignificant contribution from the musculus biceps brachii. It were the musculus flexor carpi radialis followed by the musculus triceps brachii and, finally, by the musculus extensor carpi radialis where the first volley of impulses with gradual growth and then decline of the amplitude- and frequency- specific indices was recorded. After the training course, no significant changes were registered in this muscle activation sequence.

It should be noted that prior to the training course the largest EMG amplitude in the eyes-open ball shooting sequence was recorded in the musculus extensor carpi radialis, and in the eyes-closed ball shooting sequence – in the musculus flexor carpi radialis. In the post-training EMG measurements, the highest EMG amplitudes were recorded in the musculus triceps brachii, the effect being particularly expressed in the eyes-closed ball shooting sequence. The EMG frequencies in the musculus extensor carpi radialis prior to and after the training course in the eyes-closed versus eyes-open ball shooting sequences showed no significant differences from that of the other muscular groups.

Conclusions. The inter-muscular coordination pattern development is one of the key factors of accurate shooting skills formation process. A well-developed inter-muscular coordination is one of the key factors of any accurate shooting technique as it helps duly measure and control muscular efforts in the complexly coordinated movement sequences. In the accurate shooting skills formation process, a specific redistribution of activity from the forearm to shoulder muscles takes place, with the relevant reduction of activity in the antagonistic muscles. The inter-muscular coordination level was found higher in the eyes-closed shooting sequence.

References

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