New Specific Kinesthetic Differentiation Tests for Female Volleyball Players: Reliability, Discriminative Ability, and Usefulness.

This study aimed to determine the test-retest reliability and discriminative ability of five sport-specific kinesthetic differentiation ability tests in female volleyball players. The sample of participants consisted of 98 female volleyball players aged 15.20 ± 1 years from six clubs in Bosnia and Herzegovina. Kinesthetic differentiation ability was determined by the overhead passing test, forearm passing test, float service with a net test, float service without a net test, and float service 6 m from the net test. To estimate test-retest reliability, a sub-sample of 13 players performed all tests on two testing occasions. Furthermore, the discriminative ability of the tests was determined by analyzing the performance between players of different playing positions and situational performances. Parameters of the intraclass correlation coefficient (ICC) were excellent (0.87-0.78) in all tests except for the float service with the net test, whose reliability was good (0.66). For the absolute reliability estimates, the SEM was higher than SWC (0.2) for all variables except the float service 6 m from the net test, and the SEM was lower than SWC (0.6, 1.2). One-way ANOVA detected no statistically significant inter-positional differences in all five tests (p > 0.05). A significant difference was found between less and more successful players (p < 0.01) for all applied tests. The results of this study show that a specific battery test is a reliable and valid measure and can be used to monitor kinesthetic differentiation ability in young female volleyball players.

Validity and Reliability of Isometric-Bench for Knee Isometric Assessment.

There is a strong need for a new, probably cheaper, smaller, and more portable isometric dynamometer. With this aim, we investigated the concurrent validity and reliability of a low-cost portable dynamometer to measure the isometric strength of the lower limb. Seventeen young participants (age 16.47 ± 0.51 years) were randomly assessed on three different days for knee flexion and extension isometric forces with two different devices: a commonly used isokinetic dynamometer (ISOC) and a portable isometric dynamometer prototype (ISOM). No significant differences were observed between the ISOC and the ISOM (all comparisons p > 0.05). Test-retest comparison showed the ISOM to have high reliability (ICC 0.879-0.990). This study showed that measurements with the ISOM could be performed without systematic bias and with high reliability. The ISOM is a device that is able to assess knee isometric strength with excellent concurrent validity and reliability.

Development and factorial validity of the Psychological Skills Inventory for Sports, Youth Version - Short Form: Assessment of the psychometric properties.

Researchers in sport often try to investigate relations between athletes' psychological skills and their sports results to predict top athletic achievements or unexpectedly poor performances. The Psychology Skills Inventory for Sports (Youth version), PSIS-Y, was developed to measure psychological characteristics of young athletes-differentiating well more talented and less talented young athletes. Nevertheless, previous studies revealed its inadequate, factorial validity. Thus, the aim of this study was to develop and investigate the psychometric proprieties of a brief version of the PSIS-Y (PSIS-Y-SF) in a sample of young Croatian athletes. Participants (n = 304; 188 females and 116 male) were recruited in clubs/teams all over Croatia and all of them competed in the Croatian Championship in youth (n = 157) and junior category (n = 147). The PSIS-Y-SF was derived by ten expert psychologists with five of them who had past experiences of agonistic sport practice. Psychometric analysis included Confirmatory Factor Analysis (CFA), internal consistency analysis (Raykov's Maximal Reliability), and correlation between subscales. Moreover, Multivariate Analyses of Variance (MANOVA) was run to test statistical differences between the players' categories (male youth vs. male junior vs. female youth vs. female junior) in all of the subscales. Results of the CFA suggested the adequateness of the supposed six first-order factor solution for the PSIS-Y-SF. The Maximal Reliability statistics suggest a good internal consistency for all of the subscales and the MANOVA suggested differences between the player's categories. The PSIS-Y-SF resulted to be a valid and reliable tool for the assessment of sports psychological skills. Findings from the psychometric evaluation of PSIS-Y-SF suggest that this is a useful tool, which may further assist in the measurement and conceptualization of sport psychological skills.

The Effect of Physical Activity on Cognitive Performance in an Italian Elementary School: Insights From a Pilot Study Using Structural Equation Modeling.

When compared to the previous generations, younger generations have become sedentary on a global level. Physical activity positively contributes to human growth and development, causing, indeed, both physiological and psychological benefits. The aim of the current study was examining the relationship between physical activity and school achievement in a sample of 80 Italian elementary (viz. primary) school last year responding children (11.0 ± 0.3 years, 1.46 ± 0.09 m, 39.5 ± 7.9 kg). Such an aim was fulfilled by investigating eventual correlations between physical tests results and school marks and by disclosing eventual mutual relationships between socio-demographics, family context, lifestyle (including physical activity), and school performance information using a structural modeling approach. Children were assessed for lower/upper limbs muscle strength and running/agility performance. Pearson's correlation between physical tests and school performance was studied. We found that agility correlated with English, Italian, mathematics, music, and sport marks, whereas jump correlated with English, mathematics, sport, and technologies marks. Sprint correlated with mathematics, sport, and technologies marks. All correlation coefficients were moderate, except for correlations between sport marks and physical tests (strong correlation). From the structural model, we found that socio-demographics and lifestyle significantly impacted on school achievement. In particular, lifestyle was found to fully moderate the impact of the family context on school achievement. Schools and households represent important settings for improving children physical and psychological-cognitive health and status, offering physical activities opportunities.

Leg Press vs. Smith Machine: Quadriceps Activation and Overall Perceived Effort Profiles.

First aim was describing Smith machine squat and leg press exercise as nominal load, knee extensors activity, and rating of perceived exertion. Second aim was developing predictive equations to provide same muscular activation and same perceived exertion nominal loads during the two exercises. To do that, vastus lateralis and vastus medialis activation, as their summed surface electromyography signal integrals, and overall perceived exertions were measured at different nominal loads during Smith machine squat and leg press exercise in adult male athletes experienced in weight training. Correlation and multistep stepwise analyses were performed. Then, two different results-driven predictive equations to provide same electromyography signals and same perceived exertion nominal loads were developed. The same electromyography signal equation results were less accurate (i.e., less predictive) due to high inter-individual differences, whereas the same perceived exertion equation results were more accurate, because perceived exertion is more related to the Smith machine squat and leg press exercise overall level of exertion than to the two single muscles that were investigated. In conclusion, these two equations represented an initial attempt to provide athletes and coaches with a new tool to mutually convert equivalent nominal loads during Smith machine squat and leg press exercise over a training period.

Corrigendum: Leg Press vs. Smith Machine: Quadriceps Activation and Overall Perceived Effort Profiles.

[This corrects the article DOI: 10.3389/fphys.2018.01481.].

Intra and Interzone Differences of Attack and Counterattack Efficiency in Elite Male Volleyball.

The primary goal of this study was to identify and explain differences in a volleyball set between winning and defeated teams, based on frequency and efficiency of the attack and counterattack, both overall and from particular zones of the volleyball court. Research was conducted on a randomly chosen sample of 206 sets played in 55 matches of the Men's Champions League. A total of 10555 spikes in the attack and counterattack from various zones of the volleyball court were analyzed. Between-subjects 2×5 factorial ANOVA (Outcome×Zone) was used to identify significant differences between the set outcome and zones or their interaction for both attack and counterattack efficiency. Significant differences were found in the efficiency of spikes in attacks and counterattacks from various zones of the volleyball court and between winning and losing teams. Post-hoc analysis of interaction effects also revealed significant differences. The obtained results substantiate the importance of spiking, both in the attack and counterattack, for winning a volleyball set, and indicate the specific values of spiking in the attack and counterattack from various zones, for both winning and defeated teams. The results of this study can be useful for coaches, in evaluation of player's performance in the match, in planning and programming the training process as well as in the technical and tactical preparation of the team for the tournament.

Lower Arm Muscle Activation during Indirect-Localized Vibration: The Influence of Skill Levels When Applying Different Acceleration Loads.

We investigated the electromyographic response to synchronous indirect-localized vibration interventions in international and national table tennis players. Twenty-six male table tennis players, in a standing position, underwent firstly an upper arms maximal voluntary contraction and thereafter two different 30-s vibration interventions in random order: high acceleration load (peak acceleration = 12.8 g, frequency = 40 Hz; peak-to-peak displacement = 4.0 mm), and low acceleration load (peak acceleration = 7.2 g, frequency = 30 Hz, peak-to-peak displacement = 4.0 mm). Surface electromyography root mean square from brachioradialis, extensor digitorum, flexor carpi radialis, and flexor digitorum superficialis recorded during the two vibration interventions was normalized to the maximal voluntary contraction recording. Normalized surface electromyography root mean square was higher in international table tennis players with respect to national ones in all the interactions between muscles and vibration conditions (P < 0.05), with the exception of flexor carpi radialis (at low acceleration load, P > 0.05). The difference in normalized surface electromyography root mean square between international table tennis players and national ones increased in all the muscles with high acceleration load (P < 0.05), with the exception of flexor digitorum superficialis (P > 0.05). The muscle activation during indirect-localized vibration seems to be both skill level and muscle dependent. These results can optimize the training intervention in table tennis players when applying indirect-localized vibration to lower arm muscles. Future investigations should discriminate between middle- and long-term adaptations in response to specific vibration loads.

Identification af explosive power factors as predictors of player quality in young female volleyball players.

With the purpose of determining the factor structure of explosive power, as well as the influence of each factor on situational efficiency, 56 young female volleyball players were tested using 14 tests for assessing nonspecific and specific explosive power. By factor analysis, 4 significant factors were isolated which explained the total of over 80% of the common variability in young female volleyball players. The first factor was defined as volleyball-specific jumping, the second factor as nonspecific jumping and sprinting, the third factor as throwing explosive power, while the fourth factor was interpreted as volleyball-specific throwing and spiking speed from the ground. Results obtained by regression analysis in the latent space of explosive power indicate that the identified factors are good predictors of player quality in young female volleyball players. The fourth factor defined as throwing and spiking speed from the ground had the largest influence on player quality, followed by volleyball-specific jumping and nonspecific jumping and sprinting, and to a much lesser extent, by throwing explosive power The results obtained in this age group bring to the fore the ability of spiking and serving a ball of high speed, which hinders the opponents from playing those balls in serve reception and field defence. This ability, combined with a high standing vertical jump reach and spike approach vertical jump reach (which is the basis of the 1st varimax factor) enables successful performance of all volleyball elements by which points are won in complex 1 (spike) and complex 2 (serve and block). Even though the 2nd factor (nonspecific jumping and sprinting) has a slightly smaller impact on situational efficiency in young players, this ability provides preconditions i.e. preparation for successful realisation of all volleyball elements, so greater attention must be paid to perfecting it in young female volleyball players.

Relations of competitive state anxiety and efficacy of young volleyball players.

With the aim of validating the Competitive State Anxiety Inventory on a population of young Croatian volleyball players, 286 examinees, 106 male and 180 female volleyball players (average age of 16.09+/-1.83), filled out the CSAI-2, constructed by Martens, Vealey, Burton, Bump and Smith (1990)1. Given the fact that all scales of the Competitive State Anxiety Inventory have good homogeneity, reliability and sensitivity, it can be concluded that they represent high-quality measuring instruments for measuring psychological characteristics of young volleyball players. Young male and female volleyball players generally have a moderate level of self-confidence, and their cognitive anxiety is more prominent that somatic anxiety. In order to determine the age and gender differences in somatic and cognitive anxiety and self-confidence, parametric analysis of differences was performed and coefficients of the independent samples t-test were calculated. By analysis of differences according to age, it has been established that female junior players, in relation to female youth players, express a significantly lower level of somatic and cognitive anxiety and a significantly higher level of self-confidence. As opposed to female players, male youth and junior players do not differ in any of the analysed variables. By analysis of differences according to gender, it has been established that male youth players have a significantly higher level of self-confidence in comparison to female youth players. No significant differences were found in the level of competitive anxiety and self-confidence by analysis of variance between different player roles. No significant differences were found by discriminant analysis in somatic and cognitive anxiety, and self-confidence of female volleyball players of different situational efficacy. The group of least efficient male volleyball players is characterized by a very low level of self-confidence, while the most efficient group of volleyball players is characterized by a somewhat lower level of cognitive and somatic anxiety.

Impact of biomotor dimensions on player quality in young female volleybal players.

A set of 18 test for assessing anthropometric characteristics and 12 tests for assessing motor abilities was used on a sample of 183 young female volleyball players (average age of 13.11 +/- 1.07 years). The main goal of this research was to determine the latent structure of biomotor status, as well as relations of that status to situational efficiency in female volleyball players. Situational efficiency of young volleyball players was assessed on a five-point Likert scale, in relation to each individual player's contribution to the performance of her team, and with regard to the result of that team achieved in the competition. By factor analysis, 3 anthropometric ("endo-mesomorphy", "longitudinal dimensionality of the skeleton" and "transverse dimensionality of the skeleton") and 4 motor factors ("explosive power of legs and agility", "precision", "explosive power of arms and flexibility" and "balance") were obtained. Significant impact of morphological-motor factors on situational efficiency of young female volleyball players was obtained by regression analysis. Set of predictor variables accounts for 40% of the total variance of the system. On a univariate level, all extracted factors, except precision and balance, had a significant impact on situational efficiency. Factors named "longitudinal dimensionality of the skeleton" and "explosive power of legs and agility" had the greatest partial contribution in explaining the criteria. Obtained results confirmed previous findings about the importance of individual dimensions of biomotor status for efficiency in volleyball.

Biomotor status and kinesiological education of girls aged 10 to 12 years--example: volleyball.

The aim of this study was to define processes of orientation and/or selection towards sports game of volleyball in schoolgirls of Kastela, aged 10-12, by examining the relations between regular classes of physical education (PE) and extracurricular sport activities. For this purpose, two morphological measures were used (body height and body mass) and a set of 11 motor tests (6 basic motor abilities tests and 5 motor achievement tests) on a sample of 242 girls aged 10-12 was used, divided into a subsample of 42 girls participating in volleyball training (Volleyball players) and a subsample of 200 girls who do not participate in volleyball training (volleyball non-players). Based on the comparison of test results of schoolgirls from Kastela and Croatian norms, factor analysis of applied variables and discriminant analysis of these variables between volleyball players and non-players, processes and/or phases of selection in forming quality volleyball players were defined. Selection processes are preceded by orientation processes in physical education classes, i.e. choosing those sport activities which are in accordance with the biomotor status of students. Results have shown that orientation and initial selection in female volleyball needs to be executed based on the motor set of psychomotor speed, repetitive strength of the trunk and flexibility (muscle tone regulation), and body height. Volleyball training has affected the muscle mass development and the development of strength factors, so that explosive strength of jumping and/or takeoff along with body height, has predominantly differentiated female volleyball players from non-players, aged 10 to 12, and serve and spike quality will have dominant influence on the match outcome.

Integration of technical and situation efficacy into the morphological system in young female volleyball players.

The aim of the study was to identify morphological structures of young female volleyball players according to age, and to assess the impact of these morphological structures on technical and situation efficacy. A set of 13 morphological measures as predictor variables, a set of 6 technique elements, and assessment of performance quality as criterion variables were employed in a sample of 246 female volleyball players. The sample consisted of 32 players aged 12-13, 147 players aged 14-15, 50 players aged 16-17, and 17 players aged 18-19. Analysis of variance showed the female volleyball players of various age groups to differ significantly according to the variables assessing the longitudinal skeleton dimensionality, and body mass and volume, as well as in all tests used on volleyball technique evaluation. Factor analysis of morphological measures applied across all age groups generally yielded two morphological structures: the one determined by skeleton development, i.e. longitudinal and transverse bone growth, and another one determined by soft tissue development, i.e. muscle and adipose tissue growth. Results of regression analysis revealed the longitudinal skeleton dimensionality to significantly determine the block technique performance across all age groups, and to a lesser extent performance of the spike technique in the 14-15 and 16-17 age groups. Regression correlation analysis also showed the developed skeleton based on the predominance of longitudinality to be a significant positive predictor of situation performance in all age groups.

Morphological characteristics, technical and situation efficacy of young female volleyball players.

The aim of the study was to identify differences in morphological variables and variables for quality assessment of volleyball techniques in young female volleyball players according to age and situation efficacy, and to estimate the effect of technique quality on situation efficacy. A set of 13 morphological measures and 6 technique elements were used in a sample of 246 female volleyball players divided into four age groups: 32 players aged 12-13, 147 players aged 14-15, 50 players aged 16-17, and 17 players aged 18-19. The quality of performance was assessed as a criterion variable. Analysis of variance showed the female volleyball players of various age groups to differ significantly according to the variables assessing the longitudinal skeleton dimensionality, and body mass and volume, as well as in all tests used on volleyball technique evaluation. Analysis of variance within particular age groups additionally clarified the process of modification in all study variables. Regression correlation analysis indicated the set of variables for the 6 evaluated techniques to be a rather good predictor of situation efficacy in all age groups, with service technique as the best predictor of performance quality in youngest players aged 12-13 and 14-15; spike and block techniques in players aged 16-17; and field defense technique in players aged 18-19.

Motor structures in female volleyball players aged 14-17 according to technique quality and performance.

The aim of the study was to identify motor structures in elite female volleyball players aged 14-17, and to assess the effect of these motor structures on their technical and situation efficiency. For this purpose, a battery of 12 motor tests as predictor variables, and a set of six technical elements and evaluation of performance quality as criterion variables were applied in a sample of 147 female volleyballers aged 14-15 and a sample of 50 female volleyballers aged 16-17. Analysis of variance between subgroups within the groups of volleyballers aged 14-15 and those aged 16-17 showed the results on all motor tests to improve with the increase in situation performance, which was especially pronounced in the tests assessing explosive strength and agility. The same held true for the results on all tests assessing volleyball techniques, spike and block in particular. In both samples, factor analysis of motor tests isolated two factors underlain by the generation and regulation of strength, and the mechanism of speed regulation. Canonical correlation analysis between the motor regulatory mechanisms and technical elements revealed determination of the mechanisms of strength and technical efficiency in both samples. Regression correlation analysis showed the mechanisms of strength regulation and speed to be good predictors of game performance in female volleyballers aged 14-15 and 16-17, whereby the mechanism of strength regulation had greater effect on the game performance than the mechanism of speed regulation. Regression correlation analysis also revealed the set of 6 techniques evaluated to be a good predictor of situation efficiency in both groups of female volleyballers aged 14-15 and 16-17. The block and spike techniques were found to be the best predictors of game performance quality in the former, and the techniques of spike and block in the latter. Based on the results obtained, a possible model of selection for supreme score achievement in female volleyball is described.

Effect of new rules on the correlation between situation parameters and performance in beach volleyball.

The aim of the study was to assess the effect of basic technical-tactical elements, i.e. specific motor abilities, on performance in beach volleyball, with special reference to differences between the old and new official rules. Analysis of variance for 6 variables of technical-tactical elements between the winning and defeated teams included a sample of 129 sets played according to the old official rules (1995 and 1996) and 74 sets played according to the new official rules (2003). This was followed by regression analysis between these technical-tactical elements as predictors and a variable, i.e. score difference at which the team won or lost the game, as a criterion. Results of the analysis of variance between the winning and defeated teams showed highest differences in the performance of attack-hit, followed by counterattack-hit and blocking in both game types. However, difference in the performance of serve reception, serve, and field defense between the winning and defeated teams decreased significantly with the use of new rules as compared with the old ones. Results of regression analysis indicated the sets played according to the new rules relative to old ones to increase the predominant impact of technical-tactical elements in the above-net actions, especially attack-hit and block, on the final result in beach volleyball.