Prognostic Power of Foot Mobility in Identifying the Risk of Musculoskeletal Injuries: A Cross-Sectional Study of Male Volleyball Players at Different Competitive Levels.

(1) Background: The arch structure and mobility of the foot are considered injury risk factors in volleyball. However, there are limited studies presenting differences in injury prevalence and the risk of lower limb injuries in relation to the competitive level in male volleyball. Therefore, the main aim of the current study was to evaluate foot mobility (through navicular drop test) as an injury risk factor in volleyball players from different competitive levels. (2) Methods: The reliability and usefulness of navicular drop testing were initially assessed in test-retest procedures (based on a sample of eight participants and 16 feet measurements), with primary analyses conducted using foot measurements of the twelve top-level volleyball players (24 feet) and eighteen academic-level volleyball players (36 feet). The modified navicular drop test was conducted, and the feet were classified based on arch height, and injury prevalence was retrospectively assessed with a previously validated questionnaire. Chi-squared tests, receiver operating curves, and logistic regression were used as statistical methods. The navicular drop test was verified as a reliable tool by intraclass correlation coefficient (ICC) (3.1) analysis. (3) Results: There were no significant differences in injury prevalence between academic- and top-level volleyball players, though there was a significant relationship between pronated foot and injury risk independent of competitive level. Generally, for both groups, thresholds above 10 mm of the navicular drop were predictors of lower limb injuries. The risk of injury if the foot was pronated ranged from 70% (academic level) to over 90% (top-level players). However, no statistically significant effect of competitive level on the chance of injury was observed. (4) Conclusions: Our study found a high prevalence of foot injuries independently of competitive level. There was a relationship between pronation of the foot and the risk of injury. However, the risk of lower limb injury was higher in pronated top-level players. Also, a navicular drop greater than 10 mm was an excellent predictor of injuries at both competitive levels.

Effects of six-week stroboscopic training program on visuomotor reaction speed in goal-directed movements in young volleyball players: a study focusing on agility performance.

BACKGROUND: In team sports, deficits in visuomotor reaction speed are considered a significant and modifiable risk factor that can lead to decreased performance and an increased risk of injuries. Thus, identifying effective methods to enhance visuomotor abilities is crucial. The main objective of this research was to investigate the impact of a six-week stroboscopic intervention on visuomotor reaction speed in goal-directed specific movements based on agility among young volleyball players. Additionally, the study aimed to explore the impact of saccade dynamics on visuomotor reaction speed performance throughout the experiment. METHODS: There were 50 athletes (26 males and 24 females) with an average age of 16.5 years (± 0.6) who participated in this study. Over a six-week training period, athletes performed volleyball-specific training either wearing stroboscopic glasses (intervention) or under normal visual conditions (control). Prior to and after the training period, the agility tests based on change-of-direction speed (CODS) and reactive agility (RA) were used to identify visuomotor reaction speed performance. To measure agility performance a five-repetition shuttle run to gates was conducted. The REAC-INDEX, which represents visuomotor reaction speed, was analyzed as the resulting difference between the CODS test and the RA test. To elicit saccadic dynamics, a laboratory visual search task was performed. RESULTS: A significant GROUP×TIME interaction was observed for the REAC-INDEX (p = 0.012, ηp2 = 0.13). ANCOVA analyses revealed significant GROUP differences, indicating improved post-training REAC-INDEX results (p = 0.004, d = 0.87), regardless of gender. Training-induced modulations in saccade acceleration did not reach significance, but a significant relationship was observed between changes in saccade acceleration and changes in the REAC-INDEX (r = -0.281, p = 0.048), indicating that higher performance gains following training were associated with a stronger increase in saccade acceleration. CONCLUSIONS: This study demonstrates that stroboscopic training effectively enhances visuomotor reaction speed in goal-directed movements based on agility. Furthermore, visuomotor reaction speed gains could potentially be mediated by saccade dynamics. These findings provide valuable insights into the effectiveness of stroboscopic eyewear for training sport-specific visuomotor skills among young volleyball players.

The Prevalence of Responders and Non-Responders for Body Composition, Resting Blood Pressure, Musculoskeletal, and Cardiorespiratory Fitness after Ten Weeks of School-Based High-Intensity Interval Training in Adolescents.

Many observations have demonstrated great heterogeneity in the magnitude of the response to the physical exercise stimulus. Only a few studies have investigated the effects of high-intensity interval training (HIIT) on the prevalence of non-responders (NRs) in adolescents while considering health-related fitness measurements and other co-variables. Therefore, the aim of the current work was twofold: (1) to assess the effects of ten weeks of school-based HIIT on the prevalence of responders (Rs) and NRs for body composition, resting blood pressure (BP), cardiorespiratory and musculoskeletal fitness, and (2) to assess the relationship of this prevalence with sex, body mass category, and biological maturation status, while estimating the likelihood of a response. Adolescents aged 16 years (n = 73) were included in the study. Waist-to-hip ratio, body fat percentage (BFP), skeletal muscle mass (SMM), BP, cardiorespiratory fitness (CRF), and musculoskeletal fitness were the primary outcomes. Co-variables included sex, body mass index (BMI), and maturity offset. The percentages of the Rs and NRs were analyzed based on changes (Δ) between post-intervention and pre-intervention values. The typical error (TE) method was used to identify Rs and NRs. Results showed a variation in the relative size of changes (% of changes) depending on the variable and sex. The greatest changes were observed in females' abdomen muscle strength (Δ% = 23.89%), and the difference from that of males (Δ% = 5.98%) was statistically significant (p < 0.001) with very large effect size of (Cohen's d = 0.941). Similar significant differences in relative changes were observed in body composition, but in the reverse direction. Males gained more from HIIT in the decrease in the body fat percentage (Δ% = -8.24%) and increase in skeletal muscle mass (Δ% = 3.38%) comparing to females (Δ% = 0.46, p = 0.040 and Δ% = 1.06%, p = 0.007, respectively). Effect size for body fat was small (Cohen's d = 0.469), and for skeletal muscle mass it was moderate (Cohen's d = -0.659). The results also showed positive significant differences in the prevalence of Rs compared to NRs in BFP, SMM, systolic BP (SBP), diastolic BP (DBP), CRF, and abdominal muscular strength (ABS) (p = 0.047, p = 0.047, p < 0.001, p = 0.003, p = 0.014, and p = 0.014, respectively). The effect was greatest and largest for SBP (Cohen's ω = 0.67). Sex was related to the prevalence of Rs for ABS and close to significance for SMM. More males than females benefited from HIIT in SMM (p = 0.058), but more females than males had ABS benefits (p = 0.050). Males were more likely (2.5-fold) to be Rs than females in SMM. BMI was not related to the prevalence of Rs and NRs. Biological maturation was related to the prevalence of Rs and NRs in SMM (p = 0.036) and SBP (p = 0.016). In SBP, 100% of the early matured derived benefit from HIIT, but the effect size was small (Cramer's V = 0.27). Those who maturated later were more likely (almost 70%) to be Rs. Thus, the HIIT program introduced to a typical physical education (PE) lesson can be considered partially effective. Therefore, there is a need to continue the search for an optimal and effective program for all health-related parameters. The close relationship between analyzed values and sex and biological maturation, but not BMI, indicates that the intervention programs should be tailored specifically for males and females.

Effects of in-situ stroboscopic training on visual, visuomotor and reactive agility in youth volleyball players.

Background: Stroboscopic training is based on an exercise with intermittent visual stimuli that force a greater demand on the visuomotor processing for improving performance under normal vision. While the stroboscopic effect is used as an effective tool to improve information processing in general perceptual-cognitive tasks, there is still a lack of research focused on identifying training protocols for sport-specific settings. Therefore, we aimed at assessing the effects of in-situ stroboscopic training on visual, visuomotor and reactive agility in young volleyball players. Methods: Fifty young volleyball athletes (26 males and 24 females; mean age, 16.5 ± 0.6 years) participated in this study and were each divided randomly into an experimental group and a control group, who then both performed identical volleyball-specific tasks, with the experimental group under stroboscopic influence. The participants were evaluated three times using laboratory based tests for simple and complex reaction speed, sensory sensitivity and saccade dynamics; before the after the 6-week-long training (short-term effect) and 4 weeks later (long-term effect). In addition, a field test investigated the effects of the training on reactive agility. Results: A significant TIME vs GROUP effect was observed for (1) simple motor time (p = 0.020, ηp2 = 0.08), with improvement in the stroboscopic group in the post-test and retention test (p = 0.003, d = 0.42 and p = 0.027, d = 0.35, respectively); (2) complex reaction speed (p < 0.001, ηp2 = 0.22), with a large post-test effect in the stroboscopic group (p < 0.001, d = 0.87) and a small effect in the non-stroboscopic group (p = 0.010, d = 0.31); (3) saccade dynamics (p = 0.011, ηp2 = 0.09), with post-hoc tests in the stroboscopic group not reaching significance (p = 0.083, d = 0.54); and (4) reactive agility (p = 0.039, ηp2 = 0.07), with a post-test improvement in the stroboscopic group (p = 0.017, d = 0.49). Neither sensory sensitivity nor simple reaction time was statistically significantly affected as a result of the training (p > 0.05). A significant TIME vs GENDER effect was observed for saccadic dynamics (p = 0.003, ηp2 = 0.226) and reactive agility (p = 0.004, ηp2 = 0.213), with stronger performance gains in the females. Conclusions: There was a larger effectiveness from the 6-week volleyball-specific training in the stroboscopic group compared to the non-stroboscopic group. The stroboscopic training resulted in significant improvements on most measures (three of five) of visual and visuomotor function with more marked enhancement in visuomotor than in sensory processing. Also, the stroboscopic intervention improved reactive agility, with more pronounced performance gains for short-term compared to the long-term changes. Gender differences in response to the stroboscopic training are inconclusive, therefore our findings do not offer a clear consensus.

Prognostic Potential of the Body Composition Indices in Predicting Positive Changes in Resting Blood Pressure after High-Intensity Interval Training in Adolescents.

This study aimed to investigate the prognostic potential of body composition indices in predicting the improvement in resting blood pressure after 10 weeks of high-intensity interval training (HIIT) implemented in physical education lessons. The participants were 141 adolescents aged 16 years. Independent variables were body mass index (BMI), fat mass index (FMI), muscle mass index (SMI), and mass to fat ratio (MFR); dependent variables were systolic and diastolic blood pressure (SBP, DBP) and its indices: pulse pressure (PP), mid-blood pressure (MBP), and mean arterial pressure (MAP). The receiver operating curve (ROC) method was employed. SMI and MFR are body composition indices with prognostic potential to predict positive changes in SBP in males (SMI: AUC = 0.82; p < 0.001, MFR = 0.70; p = 0.039) and MFR in females (AUC = 0.72; p = 0.035). The respective cut-off point values used to classify participants as a beneficiary of HIIT intervention concerning SBP were SMI = 7.84 and MFR = 2.43 in males, and for SMI = 10.12 and MFR = 1.94 in females. Body composition indices based on skeletal muscle (SMI, MFR) were more likely to predict positive changes in SBP after HIIT intervention in adolescents. PP, MBP, and MAP did not reflect the detecting power of SMI and MFR. However, these thresholds' utility is limited to adolescents of 16 years of age.

The Functional Form of the Relationship between Body Height, Body Mass Index and Change of Direction Speed, Agility in Elite Female Basketball and Handball Players.

The aim of this study was to assess the functional form of the relationship between two anthropometric measurements-body height (BH) and body mass index (BMI)-and two motor abilities-change of direction speed (CODS) and agility (AG)-in female elite basketball and handball players. It was hypothesized that BH and BMI might be significantly associated with AG and CODS. Two scenarios of the Five-Time Shuttle Run to Gates test (planned and unplanned) were used to evaluate the CODS and AG. Two forms of models were built to assess functional forms of the relationships between CODS and AG vs. BH and BMI: simple linear regression and binomial curvilinear regression for each type of team sport. The results confirmed the relationships between both anthropometric measurements and motor abilities only in HB, whereas in BB only a significant relationship was noted between BH and AG. Moreover, two curvilinear functional forms of the relationship were identified: inverted L-shape and inverted U-shape. Therefore, it was concluded that the first form of function indicated an initially proportional relationship between anthropometric measurement and motor test results and plateau after reaching a certain value of the BH or BMI. Similarly, the second form of function indicated the peak value of the BH or BMI which is threshold for the value of the anthropometric measurement when a progressive effect in the functional feature occurs.

The Relative Importance of Age at Peak Height Velocity and Fat Mass Index in High-Intensity Interval Training Effect on Cardiorespiratory Fitness in Adolescents: A Randomized Controlled Trial.

Background: This study aimed to evaluate the role of biological age in the relationship between preintervention fat mass and cardiorespiratory fitness effects (CRF) after High-Intensity Interval Training (HIIT) intervention in adolescents. Methods: A total of 141 boys and girls (16 years) were examined as control (CG) and experimental (EG) groups that conducted a 10-week HIIT implemented in physical education. Measurements: body height, body weight, fat mass index (FMI), CRF (Harvard Step Test). Predicted age at peak height velocity (APHV) was calculated. Pathway analyses were conducted to identify the influences of the measured variables. Results: APHV harmed the level of ΔFI (fitness index) (ß = −0.270; p = 0.035), while HIIT had a positive effect on changes in ΔFI (ß = 0.246; p = 0.002). Sex affected the changes in CRF (ß = 0.344; p = 0.011). Two models were designed respective to sex. The effect of the APHV on ΔFI in girls was close to significant (p = 0.053) but was non-significant in boys (p = 0.311). Changes in CRF in girls were positively and close to significance (p < 0.100) affected by FMIbaseline. Conclusion: HIIT is an effective way of exerting positive changes in CRF in adolescents, which is greater in boys than girls. APHV plays a role only in girls. The HIIT should be tailored to girls depending on their maturity status.

Contributing Factors to Sensorimotor Adaptability in Reactive Agility Performance in Youth Athletes.

Sensorimotor adaptability facilitates adjusting behaviour for changing environmental stimuli to maintain appropriate goal-directed motor performance. Its effectiveness is associated with perceptual-cognitive modulation. As the factors affecting it are still not completely known, the aim of our study was therefore to analyse the association between selected variables (demographic, training, anthropometric, genetic) and sensorimotor adaptation in reactive agility tasks in youth team-sport athletes. The study group consisted of 85 youth athletes (aged 12.61 ± 0.98 years). Based on an initial evaluation, participants were divided into faster and slower agility groups. The resultant differences between change of direction speed tests and reactive agility tests provided the REAC-INDEX as a dependent variable. The independent variables were as follows: gender, calendar age, body mass, height, BMI, maturity offset, training status and the BDNF rs6265 polymorphism. Multiple linear regression showed that the maturity offset (ß = 0.269; p = 0.012) and calendar age (ß = -0.411; p < 0.001) significantly contributed to the REAC-INDEX of all participants (R2 = 0.13). In the slower group, the c.196G BDNF allele had a significant influence (ß = -0.140; p = 0.044) on the REAC-INDEX. The best predictive model comprised female gender (ß = 0.799; p < 0.001), maturity offset (ß = -0.586; p < 0.001) and training experience (ß = -0.225; p = 0.009), contributing to 49% of RA variance. Sensorimotor adaptability is mainly dependent on gender and age, and can be improved through systematic sports training. The BDNF rs6265 polymorphism may be considered a contributing factor to SA variability in the initial stages of training, although polymorphism-related differences blurred as the effect of participation in sports training increased.

Prevalence of Positive Effects on Body Fat Percentage, Cardiovascular Parameters, and Cardiorespiratory Fitness after 10-Week High-Intensity Interval Training in Adolescents.

Analysis of the interventions on cardiovascular disease risk factors focuses on quantitative changes, omitting assessment of positive effect frequency in individuals. The aim of this study was to assess the prevalence of positive effects of high-intensity interval training (HIIT) on body composition, cardiovascular parameters, and cardiorespiratory fitness among adolescents. A total of 52 boys and 89 girls from a secondary school were separated into an experimental group (EG) with HIIT and a control group (CG). Body fat % (BFP), resting systolic blood pressure (SBP), diastolic blood pressure (DBP), and fitness index (FI) changes were calculated. We assessed the influence and interaction of three factors: intervention (INT), sex (SEX), and body mass index (BMIstatus) on the ratio of individuals with and without positive changes. We used log-linear models for interactions and multivariate correspondence analysis (MCA). The results indicate that HIIT affects the prevalence of positive changes in SBP, DBP, and FI. Interactions between factors suggest boys with low BMI get more benefit from the intervention than girls. The MCA indicates a relationship between FI and BFP and between BP parameters. The effectiveness of HIIT was confirmed concerning the prevalence of the positive changes in measured parameters. We suggest that HIIT should be implemented in PE lessons, although there is a need to look for a more efficient method for girls.

Mediation effect of cardiorespiratory fitness on relationships between high-intensity interval training and body fat in overweight and obese adolescents.

BACKGROUND: High-intensive interval training (HIIT) is an effective way to reduce body fat. Numerous studies confirmed the effectiveness of the HIIT for cardiorespiratory fitness development. Fewer studies examined the relationship between these factors in one dependencies model in overweight and obese adolescents. Therefore, the main aim of this study was to examine whether cardiorespiratory fitness mediated the relationship between HIIT and body fat% and whether sex moderated this relation. METHODS: Thirty-six students (15 boys and 21 girls) aged 16.02±0.39 years were examined. Participants were assigned to the HIIT intervention or control group. The intervention lasted 14 minutes during one physical education lesson per week for ten weeks. Harvard step-test results which reflected cardiorespiratory fitness and body fat% received via bioimpedance, were analyzed. RESULTS: Mediation analysis was conducted in the whole group because sex was not a moderator in any associations (P>0.05). HIIT intervention was associated with reducing body fat% (B=-3.63, P=0.029) and improvement of cardiorespiratory fitness (B=4.487, P<0.001). Simultaneously, body fat% was significantly mediated by changes in cardiorespiratory fitness (B=-2.21, P<0.049). Significant effect of HIIT on body fat% decreased (Bdirecttotal) and was no longer significant after including cardiorespiratory fitness (B=-1.42, P=0.431). CONCLUSIONS: HIIT training is an effective method of reducing body fat% and improving cardiorespiratory fitness. A higher cardiorespiratory fitness level may be conducive to increase the effectiveness of HIIT training, which translates into a more effective reduction of body fat. Due to the lack of sex moderation in the observed relationships, this effect occurs in both sexes.

The high-intensity interval training introduced in physical education lessons decrease systole in high blood pressure adolescents.

Increased resting blood pressure (BP) is a risk factor for many health complications. The prevalence of elevated BP is growing among adolescents. There is a need to investigate effective ways of decreasing excessive blood pressure in this age group. The study aim was to determine the effect of 10-weeks High-Intensive Interval Training (HIIT)-Tabata protocol-introduced in physical education (PE) lessons on resting blood pressure in adolescents. The sample included 52 boys aged 16.23 ± 0.33 years body height176.74 ± 6.07 (m), body weight 65.42 ± 12.51 (kg), BMI 20.89 ± 3.53 (kg/m2) and 89 girls aged 16.12 ± 0.42 years, body height 164.38 ± 6.54 (m), body weight 56.71 ± 10.23 (kg), BMI 20.93 ± 3.08 (kg/m2) from secondary school. Based on resting BP, the fractions of boys and girls with normal BP and high BP were identified and divided into experimental (EG) and control (CG) groups. EG completed a 10-weeks HIIT program (three cycles of Tabata protocol) implemented in one PE lesson during a week. The duration of the effort was 14 min. The intensity was at 75-80% of maximal heart rate. Changes in systolic and diastolic BP after the experiment were examined. The results indicated the improvement in SBP in EG with high BP compared to the rest of the groups (average reduction of 12.77 mmHg; p < 0.0001). The EG normotensive had a statistically significant higher reduction of SBP comparing CG normotensive (average decrease of 1.81 mmHG; p = 0.0089). HIIT effectively decreases BP in adolescents. Implementing HIIT in PE lessons in secondary school is recommended to improve BP parameters.

The Mediation Role of Fatness in Associations between Cardiorespiratory Fitness and Blood Pressure after High-Intensity Interval Training in Adolescents.

BACKGROUND: Low cardiorespiratory fitness (CRF), elevated blood pressure (BP), and high fatness are cardiovascular disease risk factors. It remains unknown how fatness affects the influence of CRF on BP. Therefore, the aim was to examine whether the associations between baseline CRF and HIIT-postintervention resting BP were mediated through fatness in adolescents. MATERIAL AND METHODS: The sample (n = 64) comprised 28 boys 36 girls aged 16 years. The analysed factors were fitness index- reflecting CRF, body fat mass (BFM), fat mass index (FMI), and body mass index (BMI). Bootstrapped mediation procedures were performed. The mediation analysis was conducted concerning the sex moderation effect. RESULTS: The mediation effect of sex was confirmed; therefore, mediations models were designed separately for boys and girls. The results showed a statistically significant inverse relationship between baseline CRF and post-intervention systolic blood pressure (SBP) in both sexes (boys: B = -0.603, p = 0.010; girls: B = -0.394, p = 0.037). The relations between CRF and SBP revealed the mediation effect of the BFM and the FMI only in boys. CONCLUSIONS: Fatness mediated associations between CRF and SBP in boys. Therefore, both CRF and fatness are necessary to maintain positive results of the BP revealed in normal SBP ranges after HIIT.

Sex Moderated Mediation of the Musculoskeletal Fitness in Relationship between High-Intensive Interval Training Performing during Physical Education Classes and Cardiorespiratory Fitness in Healthy Boys and Girls.

High-intensive interval training (HIIT) is indicated as a means of improving cardiorespiratory fitness (CRF) and musculoskeletal fitness (MSF). The relationship between CRF and MSF was examined too. Little is known about gaining CRF from HIIT independence of MSF in adolescents. Therefore, this study is aimed at investigating whether MSF mediated the relationship between HIIT and CRF and whether sex moderate this relation. The study sample included 122 individuals (45 boys, 77 girls) 16.12 ± 0.38 years of secondary school age. Participants were assigned to the HIIT intervention or control groups. The intervention lasted 14 minutes during one physical education lesson per week for ten weeks. Outcome and potential mediator were residual changes calculated from pre- and postintervention results of MSF components: handgrip (HG), sit-ups (ABS), sit-and-reach (FL), vertical jump (VJ), and Harvard step-test representing cardiorespiratory fitness (CRF). MSF index (MSFI) was calculated as a construct, agglomerating all MSF, and tested its usefulness. HIIT significantly impacted CRF in boys and girls (B = 2.32, p = 0.032; B = 2.28, p = 0.005, respectively). The impact of the HIIT program on the ABS and FL was observed only in girls. The moderation effect of sex was confirmed. Significant effect of HIIT on CRF decreased (B direct < B total) and was no significant after including FL (B = 1.46, p = 0.62)-complete mediation, but no ABS (B = 2.97, p = 0.001)-partial mediation. CRF was mediated by changes in ABS (B = 2.28, p < 0.001) and FL (4.18, p < 0.001). MSFI was not mediating; its usefulness was limited. HIIT is an effective tool in the development of CRF in both sexes. MSF played a limited role in the relationship between HIIT and CRF. It suggested different mechanisms in both sexes: girls who performed better to the HIIT had better values of FL and ABS, but not boys. HIIT intervention involved modifications in ABS or FL, which also influenced the increase of CRF.

Reactive Agility in Competitive Young Volleyball Players: A Gender Comparison of Perceptual-Cognitive and Motor Determinants.

Limited evidence is available providing specific details about the perceptual-cognitive and motor factors that contribute to reactive agility (RA) and variations between genders in young athletes. The aim of the study was to investigate perceptual-cognitive and motor determinants of RA in competitive youth volleyball players. A total of 135 volleyball players (61 males, 74 females) aged 16-18 years were included in this study. The independent variables were as follows: explosive strength, maximal frequency of movements, simple and complex reaction time, selective attention, sensory sensitivity, and saccadic dynamics. Multiple linear regression analyses showed that explosive strength (ß = - 0.494; p < 0.001) and complex reaction time (ß = 0.225; p = 0.054) accounted for 23% of the variance in RA performance in male players. The best exploratory model for RA contributed 34.5% of the variance in RA for female players with significant determinants of explosive strength (ß = -0.387; p < 0.001), sensory sensitivity (ß = -0.326; p = 0.001) and selective attention (ß = 0.229; p = 0.020). Male athletes obtained better results in RA, in all motor tests (effect size of 0.88 to 2.58) and in five variables of perceptual-cognitive skills (effect size of 0.35 to 0.98). Motor and perceptual-cognitive components significantly contributed to performance in RA in competitive youth volleyball players. Gender differentiates between players' RA performance, motor properties and saccadic dynamics to a large extent, while the remaining analyzed perceptual-cognitive components vary between female and male players to a small and moderate extent.

Combined effects of home advantage and match result on interactions performed by Brazilian handball players

Abstract Aim: This study verified the combined effects of game result and match location on centrality measures based on the interactions of Brazilian handball players. Methods: The sample consisted of 3435 interactions performed by 15 players during 7 official Brazilian Regional Championship matches. Social network analysis was applied to investigate the following network properties: degree of centrality, closeness centrality, degree of prestige, proximity prestige, and network density. Results: Results revealed that playing at home increases closeness centrality (η2 = 0.99; p = 0.01), and network density (η2 = 1.00; p = 0.01). When the handball team lost the game, an increment in the network density in relation to the draw and win scenario was observed (η2 = 1.00; p = 0.01). It was observed that closeness centrality and network density increased when the team had lost and played at home, while when the team was playing away from home and losing, closeness centrality decreased (η2 = 0.99; p = 0.01). Conclusions: In conclusion, contextual variables impact the way that handball players interact during a match.

The Relationship Between Reactive Agility and Change of Direction Speed in Professional Female Basketball and Handball Players.

Assessing the physical ability of players to perform change of direction and the cognitive and motor abilities revealed in reactive agility (RA) is necessary to understand the physical requirements and capabilities of professional players in handball and basketball. The main aim of this study was to determine the differences between professional female basketball and handball players in terms of anthropometric features, change of direction speed (CODS), and the RA task. Moreover, the relationships among anthropometric features, agility, and parameters of perception were determined. Two scenarios of the Five-Time Shuttle Run to Gates test (planned and unplanned) were used to evaluate the CODS and RA. The response time (RT) was also measured in the unplanned scenario. Additionally, the index of reactivity (REAC-INDEX) was specified as the difference between the RA test result and the measurement of CODS. There was a significant difference found in terms of body height, with basketball players being taller than handball players (p = 0.032). Professional female handball players achieved better results than professional female basketball players with regard to RA tasks (p = 0.01) and CODS (p = 0.041). Significant simple correlations between each anthropometric feature (body height, body mass) and values for CODS and RA were observed (r = 0.49-0.53). Applying partial correlation allowed for the assessment of actual relationships among CODS, RA, RT, and REAC-INDEX, without a confounding variable. Detaching the anthropometric parameters from the rest of the relationships resulted in maintenance or changes in r-values and an increased significance in the relationships between each pair: RA vs. RT, RA vs. REAC-INDEX, and RT vs. REAC-INDEX. The strongest associations were related to RT vs. REAC-INDEX (r = 0.97 at detaching body height or body mass, p < 0.001) and CODS vs. RA (r = 0.66 at detaching body height and r = -0.67 at detaching body mass, p < 0.001). It is recommended to use partial correlations in subsequent studies, as simple correlations are not reliable and may not reveal the apparent relationships between the variables. In addition, when determining the CODS and RA, it is suggested to take anthropometric and perception variables into account, such as reaction time or REAC-INDEX.

Bone mineral density in elite masters athletes: the effect of body composition and long-term exercise.

BACKGROUND: The purpose of the study was to examine how bone mineral density (BMD) is related to body composition depending on the practiced sport (endurance, speed-power, throwing sports) in participants of the World Masters Athletics Championship. METHODS: Dual-energy X-ray absorptiometry (DXA) was used to determine BMD and bone mass (BMC). Body composition was analyzed by means of the JAWON Medical X-scan analyzer using bioelectrical impedance methods. Percentage body fat (%BF), body fat mass (BFM), lean body mass (LBM), total body water (TBW), soft lean mass (SLM), intracellular water (ICW), and extracellular water (ECW) were evaluated. RESULTS: Among men, the most important variables affecting the BMD norm were LBM (OR = 32.578; p = 0.023), ECW (OR = 0.003; p = 0.016) and ICW (OR = 0.011; p = 0.031), in the distal part and SLM (OR = 5.008; p = 0.020) and ICW (0.354, p = 0.008) in the proximal part. In women, the most important predictors of normal BMD were ICW (OR = 10.174; p = 0.003) and LBM (OR = 0.470; p = 0.020) in the distal part and ICW (OR = 5.254; p = 0.038) in the proximal part. CONCLUSION: The representatives of strength based events had the most advantageous BMD levels. The condition of bone tissue evaluated by BMC and BMD of the forearm in masters athletes was strongly determined by the level of lean body components and the type of sports training associated with the track and field event. In the most important predictors of the BMD norm were also hydration components ECW and ICW. However, this relationship requires more research on the nature and mechanisms of these interactions.

Optimal Values of Body Composition for the Lowest Risk of Failure in Tabata Training's Effects in Adolescents: A Pilot Study.

BACKGROUND: The optimal body mass index (BMI) and fat mass index (FMI) values for a positive change or the lowest risk of no positive change after high-intensity interval training (HIIT) using the Tabata protocol remain unclear. This study is aimed at establishing these optimal BMI and FMI values for the lowest risk of failure of aerobic performance in adolescents. METHODS: A 10-week HIIT programme was introduced into the physical education of 73 students. BMI was calculated using height and weight. Bioelectrical impedance analysis measured body fat, and the InBody apparatus generated the FMI. Based on BMI and FMI, the participants were divided into four groups. Pre- and post-HIIT intervention analyses were carried out using the Harvard step test, which was used to determine the physical efficiency index (PEI). RESULTS: The Youden index confirmed that the risk of no positive effects in PEI was the lowest for the second BMI interval (19.01-22.00 kg/m2) and FMI Q 2-3 (7.96-8.91 kg/m2). The optimal BMI value for the lowest risk of no change in PEI was 20.60 kg/m2, and the optimal FMI value was 8.84 kg/m2. CONCLUSION: A comparison of the two indices shows that FMI had stronger effects on PEI than BMI. In addition, the model obtained for FMI had higher accuracy. Identifying at-risk individuals, those in need of improving health-related fitness (H-RF), and those with a low risk of poor H-RF allows for efficient planning of individual intervention services and training programmes.