Sadettin Kirazci

Sensorimotor performance asymmetries predict hand selection

Handedness is most often measured by questionnaires that assess an individuals preference for using a particular hand to perform a variety of tasks. While such assessments have proved reliable, they do not address the underlying neurobehavioral processes that give rise to the choice of which hand to use. Recent research has indicated that handedness is associated with hemispheric specializations for different aspects of sensorimotor performance. We now hypothesize that an individuals choice of which hand to use for a given task should result from an interaction between these underlying neurobehavioral asymmetries with task conditions. We test this hypothesis by manipulating two factors in targeted reaching movements: (1) region of workspace and (2) visual feedback conditions. The first manipulation modified the geometric and dynamic requirements of the task for each arm, whereas the second modified the sensorimotor performance asymmetries, an effect predicted by previous literature. We expected that arm choice would be reflected by an interaction between these factors. Our results indicated that removing visual feedback both improved the relative performance of the non-dominant arm and increased the choice to use this arm for targets near midline, an effect that was enhanced for targets requiring larger movement amplitudes. We explain these findings in the context of the dynamic dominance hypothesis of handedness and discuss their implications for the link between hemispheric asymmetries in neural control and hand preference.

Motor Asymmetry in Elite Fencers

ABSTRACT The authors previously reported that asymmetrical patterns of hand preference are updated and modified by present sensorimotor conditions. They examined whether participation in long-term training in the upper extremity sport fencing might modify arm selection and performance asymmetries. Eight fencers and eight nonfencers performed reaching movements under 3 experimental conditions: (a) nonchoice right, (b) nonchoice left, and (c) choice, either right or left arm as selected by subject. The nonchoice conditions allowed assessment of potential interlimb differences in movement performance, while the choice condition allowed assessment of the frequency and pattern of arm selection across subject groups. Our findings showed that the athlete group showed substantially greater symmetry in the performance and selection measures. These findings suggest that arm selection and performance asymmetries can be altered by intense long-term practice.

Coincidence-Anticipation Timing Requirements are Different in Racket Sports

The aim of this study was to compare the coincidence-anticipation timing accuracy of athletes of different racket sports with various stimulus velocity requirements. Ninety players (15 girls, 15 boys for each sport) from tennis (M age = 12.4 yr., SD = 1.4), badminton (M age = 12.5 yr., SD = 1.4), and table tennis (M age = 12.4 yr., SD = 1.2) participated in this study. Three different stimulus velocities, low, moderate, and high, were used to simulate the velocity requirements of these racket sports. Tennis players had higher accuracy when they performed under the low stimulus velocity compared to badminton and table tennis players. Badminton players performed better under the moderate speed comparing to tennis and table tennis players. Table tennis players had better performance than tennis and badminton players under the high stimulus velocity. Therefore, visual and motor systems of players from different racket sports may adapt to a stimulus velocity in coincidence-anticipation timing, which is specific to each type of racket sports.

The effects of rhythm training on tennis performance.

The Effects of Rhythm Training on Tennis Performance Rhythm training is an integral part of sports. The purposes of the study were to analyze the effects of rhythm training on tennis performance and rhytmic competence of tennis players, to compare the improvement levels of tennis specific and general rhythm training and to examine the effects of shorter and longer tempos on rhythmic competence. Thirty university students whose mean score of International Tennis Number (ITN) was 7.3 (±0.9) were divided randomly into three sub-groups: Tennis Group, General Rhythm Training Group and Tennis-Specific Rhythm Training Group. The experimental procedure lasted 8 weeks. During this period, all groups had the same tennis training twice a week. The Tennis Group had regular tennis training sessions. In addition to regular tennis training sessions, the General Rhythm Training Group followed the general rhythm training sessions and the Tennis-Specific Rhythm Training Group had tennis-specific rhythm training. The measurement instruments were ITN, Rhythmic Competence Analysis Test and Untimed Consecutive Rally Test. The results indicated that participation in tennis-specific or general rhythm training resulted in progress in tennis playing levels, forehand consistency performance and rhythmic competence of the participants. On the other hand, attendance to the regular 8-week tennis training was enough to solely increase the tennis playing level but not sufficient to develop forehand consistency performance and rhythmic competence. Although the participants in the TRTG had better improvement scores than the ones in the GRTG, no significant difference was found between the rhythm training groups. The results also revealed that participants exhibited higher rhythmic competence scores on fast tempo compared to slow tempo.

Comparison of the Static and Dynamic Balance Between Normal-Hearing and Hearing-Impaired Wrestlers

Balance is fundamental in sport, especially when there is an opponent. Although balance can be improved with practice, it is highly aff ected by nervous system disorders, particularly by vestibular disorders and visual impairment. Th e purpose of this study was to compare static and dynamic balance between normal and hearing-impaired wrestlers. Th e participants were 52 young male hearing-impaired wrestlers (n=29, age=18.76±3.54) and normal-hearing athletes (n=23, age=19.09±2.76) competing at the national level. Th e static and dynamic balance were measured using the stork test on one foot and the Y-balance test (in anterior, posteromedial & posterolateral directions). MANOVA indicated signifi cant diff erences between groups (Wilks’ L=.284, F12,39=8.21, p<.05, η2=.72). Diff erences were detected in how long the participant had been active in the sport F(year) (F1,50=145.95, p<.025, η2=.75) and right leg static balance (F1,50=73.63, p<.025, η2=.60). As for the Y balance test, there was also a signifi cant diff erence in the anterior direction for the right leg (F1,50=4880.66, p<.025, η2=.99) and left leg (F1,50=3563.87, p<.025, η2=.99). Hearing-impaired wrestlers performed better balance abilities in the dynamic balance test of right and left legs in the anterior direction. In contrast, the amount of time active in the sport and the static balance of the right leg were found better in normal-hearing wrestlers. Being better than normal wrestlers only in the anterior direction of the dynamic balance might be due to the diff erences related to the directions of the test. Future studies are recommended for investigating the reasons for this diff erence.