| Abstract | Effects Of Sensorimotor Training On Motor Control And Dynamic Balance In Hearing Impaired Handball Players Temeljni cilj ovog istraživanja bio je istražiti učinke senzomotornoga treninga na motoričku kontrolu u koljenom zglobu i dinamičku ravnotežu rukometaša s oštećenjem sluha. Sekundarni cilj istraživanja bio je utvrditi utjecaj senzomotornoga treninga na motoričku kontrolu u koljenom zglobu i dinamičku ravnotežu rukometaša s oštećenjem sluha u uvjetima umora. Prema dosadašnjim spoznajama iz područja neurofiziologije, sportskog treninga i motoričke kontrole, postavljene su četiri hipoteze: provedeni senzomotorni trening proizvesti će statistički značajno poboljšanje motoričke kontrole u koljenom zglobu rukometaša s oštećenjem sluha (H1), provedeni senzomotorni trening proizvesti će statistički značajno poboljšanje dinamičke ravnoteže rukometaša s oštećenjem sluha (H2), provedeni senzomotorni trening proizvesti će statistički značajno poboljšanje motoričke kontrole u koljenom zglobu rukometaša s oštećenjem sluha u uvjetima umora (H3) i provedeni senzomotorni trening proizvesti će statistički značajno poboljšanje dinamičke ravnoteže rukometaša s oštećenjem sluha u uvjetima umora (H4). Istraživanje je provedeno na prigodnom uzorku od dvadeset i četiri rukometaša s oštećenjem sluha Zagrebačke županije i Grada Zagreba, muškog spola, prosječne dobi od 28 godina (± 6,3 godine), koji su nasumično raspoređeni ili u kontrolnu (12) ili u eksperimentalnu (12) skupinu. U trenažnom razdoblju od pet tjedana ispitanici eksperimentalne skupine proveli su ukupno 20 trenažnih jedinica senzomotornoga treninga, dok su ispitanici kontrolne skupine nastavili s njihovim uobičajenim aktivnostima. Utjecaj provedenog senzomotornoga treninga na dinamičku ravnotežu i motoričku kontrolu ispitanika procijenjen je zvjezdolikim testom ravnoteže, zadatkom precizne reprodukcije kuta fleksijom potkoljenice i testom brzine kretanja braniča kliznim koracima u dva trokuta. Za sve varijable izračunati su osnovni centralni i disperzivni parametri u inicijalnom i finalnom mjerenju. Promjene između početnog i završnog mjerenja za svaku skupinu ispitanika posebno, provjerene su uz pomoć t-testa za zavisne uzorke. Veličina učinka trenažnih programa procijenjena je Cohenovim indexom veličine učinka. Razlika u promjenama između skupina nakon trenažnog razdoblja u svakoj od zavisnih varijabli, utvrđena je pomoću dvofaktorske analize varijance (grupa x vrijeme) s ponovljenim mjerenjima na jednom faktoru (vrijeme). Razina statističke značajnosti postavljena je na p < 0,05. Istraživanjem je utvrđen pozitivan utjecaj provedenog senzomotornoga treninga na motoričku kontrolu u koljenom zglobu i dinamičku ravnotežu rukometaša s oštećenjem sluha u uvjetima odmora i smanjeni utjecaj umora na motoričku kontrolu u koljenom zglobu i dinamičku ravnotežu rukometaša s oštećenjem sluha. Zaključno, istraživanjem otkriveni lokalni mehanizmi specifične adaptacije na trening i mogućnost odgode utjecaja umora na stabilnost koljena sportaša s oštećenjem sluha predstavljaju značajan znanstveni doprinos području koji proučava prevencijske strategije u smislu smanjenja iznimno često ozlijeđenog koljenog zgloba. Dobiveni rezultati predstavljaju i praktičan doprinos unapređenju planiranja i programiranja prevencijskih strategija u radu sa sportašima s oštećenjem sluha, a pogotovo rukometašima. |
| Abstract (english) | Purpose: The main goal of this research was to investigate the effects of sensorimotor training on postural control in the knee joint and the dynamic balance of hearing-impaired male handball players. The secondary goal was to investigate the effects of sensorimotor training on postural control in the knee joint and the dynamic balance of hearing-impaired male handball players in conditions of fatigue. According to recent insights in neurophysiology, sports training and motor control, the four main hypotheses were set: the conducted sensorimotor training will significantly improve postural control in the knee joint of hearing-impaired male handball players (H1), the conducted sensorimotor training will significantly improve the dynamic balance of hearing-impaired male handball players (H2), the conducted sensorimotor training will significantly improve postural control in the knee joint of hearing-impaired male handball players in conditions of fatigue (H3) and the conducted sensorimotor training will significantly improve the dynamic balance of hearing-impaired male handball players in conditions of fatigue (H4). Methods: The research was conducted on a suitable sample of twenty-four male handball players with hearing impairment from the city of Zagreb and Zagreb County. They were approximately twenty-eight years of age (± 6,3 years). Before starting the research, a joint meeting was conducted at which the handballers with the hearing impairment were briefed in detail of the research plan as well as the possible risks of their participation. The basic objective of the research was explained, and a detailed description of the experimental plan was given to them. The estimated measurement procedure, fatigue protocol and experimental training programme were also described. After the meeting, the respondents signed a declaration of voluntary consent to the participation in the research. The criteria for the inclusion of participants in the research consisted of: a diagnosed hearing impairment (at least 55 dB on an audiometry test in the better ear), less than 40 years of age and regular handball training (either only within the club system or within the club and through the preparation system for the national team). The exclusion criteria were: acute lower extremity injury within one year before the start of the study, having an overuse syndrome or lumbar pain and having a neuromuscular disorder. After the initial measurement was carried out, the participants were randomly assigned to one of the following groups: control group (K) - 12 participants and experimental group (E) - 12 participants. The conducted research belongs to the category of randomized controlled studies. As a part of the research, the effects of the training programme (sensorimotor training), which lasted for five weeks with a total of 20 training units, were studied. Participants in the experimental group were included in sensorimotor training. Each training unit consisted of an initial ten-minute warm-up (running with tasks and stretching exercises), the main unit that carried out exercises to develop strength, postural control, plyometrics and dynamic balance along with the units for the development of motor control under the specific conditions of handball game. The control group (K) participants did not have any specific sensorimotor training during the five-week training period, however, they continued with their usual activities. Dynamic balance was measured using the star excursion balance test. Dynamic balance measures were the average length on each of the eight directions measured in centimetres, and the calculated total covered area, as an overall measure of the dynamic balance of each leg. Motor control in the knee joint was assessed by the task of accurately reproducing the angle by flexion of the lower leg. The ability to accurately reproduce the angle in the knee joint was assessed through the average deviation produced from the reference angle (Ō), expressed in degrees. Another test for motor control assessment was the defender's movement in two triangles test. The test was carried out using two-stepping right-angled triangles of a 1,5 m long cathetus each. The time spent to cover the given surface forming two triangles (right and left) with slide steps, in milliseconds, was used as an indicator of motor control in a specific handball situation. The examiner described and demonstrated each task, and the participants had enough time to try them out before officially performing them. The fatigue protocol was based on the implementation of four sections of running with tasks of different lengths at maximum speed (2x10m, 2x20m, 2x30m and 2x40m). The tasks included lateral movement at maximum speed with imitation of blocking shots, running with changes in direction of movement and slalom run with the imitation of jump shots. The average duration of the protocol was 90 seconds, and it was repeated four times with two minutes rest in-between repetitions. The total duration of the fatigue protocol was 12 minutes in average. Such a protocol brings the organism to the conditions of maximum glycolysis, which ensures the onset of local fatigue. The state of fatigue of the respondents was checked through lactate measurements (two minutes after the implementation of the fatigue protocol) and through a modified Borg scale for subjective assessment of the state of fatigue (from 1 for slight fatigue to 10 for extreme fatigue). To measure the monitored abilities in rested and fatigued participants, the fatigue protocol was carried out at the initial and final measurement, and the intended tests were carried out before and after the fatigue protocol. The implementation of the fatigue protocol at the initial and final measurements made it possible to check the impact of the conducted sensorimotor training on dynamic balance and motor control in conditions of present or non-present fatigue. For all variables, the basic central and dispersive parameters in the initial and final measurements were calculated. Changes between the initial and final measurements for each group of subjects were checked separately by means of a t-test for dependent samples. The magnitude of the effect of training programmes was estimated by Cohen's effect size index. The difference in changes between groups after the training period, in each of the dependent variables, was determined using two-factor variance analysis (group x time) with repeated measurements on one factor (time). The level of statistical significance was set at p < 0.05. Results: The body weight and consequently the body mass index of participants for both groups, in particular, did not change significantly during the implementation of the five-week experimental sensorimotor training programme. The values of the body weight and body mass index measured at the end of the five-week training period did not differ between groups either (bodyweight p = 0.89; body mass index p = 0.21). As part of the research, motor control in the knee joint was assessed through kinesthesia and agility tasks. The results indicate a certain effect of the conducted sensorimotor training on the motor control of hearing-impaired handball players, assessed through kinesthesia tasks (precise reproduction of the angle in the knee joint). The variables assessing the agility of the participants did not show a statistically significant effect of the performed sensorimotor training (from p = 0.18 to p = 0.14), although the insight into descriptive indicators showed a trend of improving performance in the final measurement. The comparison between the groups, in the results achieved in the initial and final measurements, in motor control indicators (kinesthesia and agility), indicated significant differences in the average deviation produced from the reference angle for the 60° knee joint angle for the preferred (p = 0.03) and unpreferred (p = 0.04) leg. The results also indicate a statistically significant effect of sensorimotor training in eight indicators of the dynamic balance of hearing-impaired handball players. The comparison between the groups, in the results achieved in the initial and final measurements, in dynamic balance pointed to significant intersecting differences in nine directions. The obtained results indicate a certain effect of fatigue on the motor control of hearing-impaired handball players, assessed through agility tasks (the time taken to perform the task of moving in sliding steps in two triangles) and kinesthesia (precise reproduction of the angle in the knee joint), measured on the initial test. The statistically significant effect of fatigue on the monitored variables was found in both experimental and control group participants. The obtained results indicate a certain effect of fatigue on the dynamic balance of handball players with hearing loss, assessed through the task of a star excursion balance test, measured at the initial measurement. The statistically significant effect of fatigue on the assessed variables was found both in the experimental and control group participants. The obtained results do not indicate a significant effect of fatigue on the motor control of handball players with hearing impairment of the experimental group, assessed through agility tasks (the time required to perform the task of moving in sliding steps in two triangles) and kinesthesia (precise reproduction of the angle in the knee joint), on the final measurement. On the other hand, a statistically significant fatigue effect was found in the control group participants in both agility and kinesthesia assessment variables. In the experimental group, there is a clear trend of deterioration of results in almost all the variables in conditions of fatigue, but these changes are not statistically significant. The obtained results do not indicate a significant effect of fatigue on the dynamic balance of handball players with hearing impairment of the experimental group, assessed through the task of a star excursion balance test on the final measurement. On the other hand, in the participants of the control group, a statistically significant effect of fatigue was found in most indicators of dynamic balance. Again, in condition of fatigue, participants of the experimental group tend to achieve worse results in almost all dynamic balance variables, however these changes are not statistically significant. Discussion and conclusions: In team sports, the deterioration of sensorimotor function including balance instability that could have been caused by previous injuries or muscle fatigue is considered a risk factor for injury in athletes. Fatigue can contribute to changing the motor control of the lower extremities subsequently impairing the ability to dynamically stabilize the knee. Nevertheless, the exact mechanism of action of fatigue on knee kinesthesia, dynamic balance and agility in specific sport situations is not fully understood, and the possibility of reducing the influence of fatigue by means of a sensorimotor training has not been explored to date. The results of the conducted study show for the first time a decrease in the acute impact of fatigue on kinesthesia in the knee joint as well as on agility and dynamic balance of trained athletes using sensorimotor training. The results of the impact of sensorimotor training on knee kinesthesia and dynamic balance of athletes convey current knowledge by testifying the targeted adaptation of muscle mechanoreceptors (muscle spindle and Golgi apparatus) to a combination of specific agility exercises, plyometrics, and balance. The fact that the study was conducted on handball players with hearing loss made it possible to test the local nervous adaptation on participants whose adaptation at the level of the auditory receptors was disrupted by the disease. The obtained results point to the fact that to reduce the impact of fatigue on knee joint motor control of trained handball players, the sensorimotor training must last at least five weeks, with a total of 20 training units, and consist of a combination of specific agility, balance and plyometric exercises. In conclusion, the research revealed local mechanisms for the influence of fatigue on the motor control of the knee and the possibility of delaying fatigue as well as a consequent deterioration of knee stability in hearing-impaired athletes representing thus a significant contribution to the scientific field that studies prevention strategies, as well as a practical contribution that improves the planning and programming of prevention strategies of handball players. |
