rss_2.0Journal of Human Kinetics FeedSciendo RSS Feed for Journal of Human Kinetics of Human Kinetics Feed Validity and Applicability of a Team-Sport-Specific Change of Direction Test<abstract> <title style='display:none'>Abstract</title> <p>Cuts and changes of direction (COD) are frequent movements during games in team sports. Since those movements are seen as a key performance variable, COD assessments are included in performance diagnostics. However, some tests are criticized as they seem to be confounded by variables such as linear sprinting. Therefore, it is suggested that not only total COD time should be assessed, but also the athletes' COD movements should be examined more closely. For example, split times could be analyzed in tests with more than one COD like the Team-Sport-Specific COD (TSS-COD) test. We aimed to investigate the construct validity of the TSS-COD test, focusing on the homogeneity of the different test parts. We also tested how far sprint performance mapped onto COD performance. Test data were analyzed from 154 elite male and female volleyball and basketball athletes. A Fitlight© System was used to assess duration of the TSS-COD test. For the sprint tests, magnetic gates (Humotion GmbH) were used to measure sprint time. Explorative principal component analysis (PCA) was conducted including the test interval duration and the athletes’ 5, 10, and 20 m sprint performance, to test the validity of the TSS-COD test. PCA results showed that the start interval formed a factor separate from the other COD sub-intervals. In addition, sprint performance was separated from all COD interval measures. The findings of the PCA were confirmed by split-half validation. Since sprint and COD performance represent independent performance domains within this analysis, we suggest the TSS-COD test to be a valid test to assess COD performance.</p></abstract>ARTICLEtrue and Kinematic Analysis of Initial Step Patterns for Multidirectional Acceleration in Team and Racquet Sports<abstract> <title style='display:none'>Abstract</title> <p>The ability for quick multidirectional accelerations is crucial for athletic performance in team and racquet sports. So far, there has been little research dedicated to different initial step patterns usually applied by players. Therefore, the present study investigated the kinematic characteristics and effectiveness of the following step patterns: Jab Step (JS), Pivot Step (PS), Gravity Step (GS) and Counter Step (CS). Twenty-two male competitive team and racquet sport athletes completed maximum lateral accelerations utilizing the step patterns. Following familiarization with each step pattern, three 5 m sprints (5 m STs) into both directions (left &amp; right) were completed. Sprint times, the translation of the center of mass (CoM) and joint angles were obtained using three-dimensional motion analysis. 5 m STs of the CS were faster compared to the GS and PS for both directions. A detailed distance-time analysis revealed that for shorter distances only the JS was faster than the GS. Regarding the sequence in which the maximum angular velocities (max. <inline-formula><alternatives><inline-graphic xmlns:xlink="" xlink:href="graphic/j_hukin-2022-0106_eq_001.png"/><mml:math xmlns:mml=""> <mml:mrow class="MJX-TeXAtom-ORD"> <mml:mover> <mml:mi>w</mml:mi> <mml:mo stretchy="false">→<!-- → --></mml:mo> </mml:mover> </mml:mrow> </mml:math><tex-math> $\vec{w}$</tex-math></alternatives></inline-formula>) in the hip, the knee, and the ankle were reached during the push off, there was a proximal-to-distal sequence for the JS and the CS, but a distal-to proximal sequence for the GS and the PS. The results reveal that the JS and the CS are superior for accelerations towards the lateral direction. Specifically, they indicate that the JS is more suitable for covering very short distances and the CS is superior for covering further distances. In addition, the distal-to-proximal sequence of max. <inline-formula><alternatives><inline-graphic xmlns:xlink="" xlink:href="graphic/j_hukin-2022-0106_eq_002.png"/><mml:math xmlns:mml=""> <mml:mrow class="MJX-TeXAtom-ORD"> <mml:mover> <mml:mi>w</mml:mi> <mml:mo stretchy="false">→<!-- → --></mml:mo> </mml:mover> </mml:mrow> </mml:math><tex-math> $\vec{w}$</tex-math></alternatives></inline-formula>during the push-off in the GS and the PS might indicate lower kinematic efficiency.</p></abstract>ARTICLEtrue of Direction Ability as a Sensitive Marker of Adaptation to Different Training Configurations, and Different Populations: Results from Four Experiments<abstract> <title style='display:none'>Abstract</title> <p>This article includes four separate experiments. In the first experiment male beach handball players (n = 24) were randomly assigned to regular training (n = 12) or plyometric and sprint training (n = 12). In the second experiment, male players were assigned to a handball practice only (n = 12), a plyometric training (n = 12), or an eccentric-overload (e.g., versa-pulley machine) training group (n = 12). In the third experiment, participants were assigned to padel training (n = 12) or specific on-court neuromuscular technical actions (n = 12). In the fourth experiment, females between 50–59 years (n = 25), 60–64 years (n = 25), and 65–70 years (n = 25) completed 10 weeks of bench stepping training involving jumps, and were compared to age-matched controls (n = 45). The COD ability was assessed with the 10-m COD ability test (experiments one and two), the COD ability test with 90º and 180º turns (third experiment), and with the timed-up-and-go test (fourth experiment). In experiment one, greater COD improvement was noted in the experimental group compared to the control group (p &lt; 0.05). In experiment two, both intervention groups similarly improved COD when compared to the control group (p &lt; 0.05). In experiment three, although no significant group-time interactions were observed for COD, the experimental group improved all COD measures pre-post-training (p &lt; 0.05), with a larger effect size for COD with 180° turn to the right compared to the control group (effect size = 0.8 vs. 0.3). In experiment four, the three training groups improved COD ability compared to the control group (p &lt; 0.05). In conclusion, COD is a sensitive marker of adaptation to different training configurations in these diverse groups.</p></abstract>ARTICLEtrue Relationship among Acceleration, Deceleration and Changes of Direction in Repeated Small Sided Games<abstract> <title style='display:none'>Abstract</title> <p>The change of direction (COD) ability is perhaps the most significant fitness component in team sport games. One of the best ways to develop COD as well as other components of the game in soccer is the regular inclusion of small sided games (SSGs) in the training process. Therefore, the aim of this research was to determine changes in physiological and kinematic variables in repeated SSGs in youth soccer players. Additionally, we investigated the relationship between selected IMA variables such as acceleration, deceleration and changes of direction. Participants included sixteen U17 soccer players from a 2<sup>nd</sup> league professional team with a high aerobic capacity. The study design involved six 3-min 4 × 4 SSGs with goalkeepers and with a 3-min rest interval between games, during two training sessions played on a field of 25 x 35 m. The results showed that the intervention protocol consisting of repeated SSGs generated an intensity below the anaerobic threshold. This allowed for the maintenance of all variables (Heart Rate, Total Distance Covered, Velocity, Acceleration, Deceleration, Change of Direction) at a similar level throughout the subsequent six SSGs. The analysis revealed that in the six SSGs, players performed the most Acc and Dec, then COD Right and the least COD Left. From the third game on, a decrease in the number of COD Right was noticed. We hypothesized that progressive neuromuscular fatigue on the dominant side caused a more symmetrical trend in COD.</p></abstract>ARTICLEtrue between Sprint, Acceleration, and Deceleration Metrics with Training Load in Division I Collegiate Women’s Soccer Players<abstract> <title style='display:none'>Abstract</title> <p>Player load is a variable derived from GPS technology that quantifies external load demands. Sprints and change-of-direction movements are high-intensity activities that place stress on the body. Research is needed to determine which sprint metrics may relate to and predict player load during practice sessions in collegiate women’s soccer players, as coaches could manipulate the most impactful variables. This study analyzed which sprint metrics related to GPS player load in women’s soccer players from one Division I team. Data from 19 practice sessions for 18 field players were analyzed. Players wore GPS sensors during all training sessions, and the variables assessed were player load, sprint count, sprint volume, sprint distance, average top speed, maximum top speed, and the number of accelerations and decelerations in different speed zones (±1, ±2, ±3, ±4, ±5 m/s<sup>2</sup>). Pearson’s correlations (p &lt; 0.05) analyzed relationships between the sprint variables and player load. Stepwise regression analyses (p &lt; 0.05) determined if any metrics predicted player load. The results indicated significant relationships between player load and sprint count, maximum top speed, sprint distance, sprint volume, number of decelerations at –1, –2, and –3 m/s<sup>2</sup>, and accelerations at 1, 2, and 5 m/s<sup>2</sup>(r = 0.512–0.861, p ≤ 0.025). Sprint distance and decelerations at 1 m/s<sup>2</sup>predicted player load (p = 0.001, r<sup>2</sup>= 0.867). Maximal sprinting and decelerations and accelerations at different speeds were significant contributors to player load in collegiate women’s soccer players. Sprint distance, decelerations, and accelerations could be targeted in training drills via dimension and movement manipulation to adjust training intensity for collegiate women’s soccer players.</p></abstract>ARTICLEtrue Agility in Competitive Young Volleyball Players: A Gender Comparison of Perceptual-Cognitive and Motor Determinants<abstract> <title style='display:none'>Abstract</title> <p>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 &lt; 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 &lt; 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.</p></abstract>ARTICLEtrue among the Change of Direction Ability, Sprinting, Jumping Performance, Aerobic Power and Anaerobic Speed Reserve: A Cross-Sectional Study in Elite 3x3 Basketball Players<abstract> <title style='display:none'>Abstract</title> <p>The main purpose of this study was to determine the relationships among sprinting performance, change of direction ability (COD), change of direction deficit (CODD), and aerobic power expressed by maximal oxygen velocity (V<sub>max</sub>IFT), anaerobic speed reserve (ASR) as well as jumping performance (countermovement jump with (CMJa) and without an arm swing (CMJ)) in elite 3x3 basketball players. A total of 15 Polish Olympic 3x3 team players (age: 26.86 ± 8.28 years; body height: 191 ± 5.33 cm; body mass: 90.68 ± 10.03 kg, basketball experience: 15.53 ± 5.8 years) participated in the study. Athletes were tested for the following measures: the linear speed at the first section (5 m), the second section (9 m), the third section (10 m) and total distance (24 m), two sets; the 30-15 Intermittent Fitness Test (first session); COD speed by the Change of Direction and Acceleration Test (CODAT) (the same sections and total distance as in the linear speed test), five repetitions, two sets; and jumping performance by the CMJ with and without an arm swing (second session). CODD was calculated by subtracting the COD speed time from linear speed time at adequate sections and total distance. Maximal sprinting speed (MSS), maximal aerobic velocity (V<sub>max</sub>IFT), and anaerobic speed reserve (ASR) were also considered. Anaerobic Speed Reserve (ASR) was calculated as the difference between MSS and V<sub>max</sub>IFT. A Pearson’s correlation test was used to determine the relationship between power-speed-related variables and CODD, final velocity attained at the 30-15 Intermittent Fitness Test (V<sub>max</sub>IFT), ASR, and COD performance. Moderate to strong correlations were registered between COD and linear speed at 5, 10, and 24 m, while moderate to strong negative correlations were detected between COD, CODD, and CMJ, CMJa. Moreover, moderate to strong correlations were observed between COD, CODD, and V<sub>max</sub>IFT, MSS at 9, 10, and 24 m sprints. No relationship was detected between COD, CODD, LS, and ASR in any measured sector. Finally, statistically significant differences were registered in COD and CODD between trial 1 and trial 2.</p></abstract>ARTICLEtrue of Arm Dominance and Decision Demands on Change of Direction Performance in Handball Players<abstract> <title style='display:none'>Abstract</title> <p>This field study investigated the effect of unilateral dominance (handedness of players) on the change of direction speed in a specific cutting manoeuvre with a ball (in the direction of the throwing arm vs. against the direction of the throwing arm) in team handball. In addition, the effect of a cutting manoeuvre in response to an immediate stimulus compared to one planned in advance on the movement speed was analysed. Forty participants (22 male, 18 female, M<sub>age</sub> 23 years) performed change of direction actions to the left and the right side (the direction of the throwing arm vs. against the direction of the throwing arm) under planned and reactive (light as visual stimuli) conditions. Change of direction speed was measured post-hoc by video-analyses. The results showed two effects. First, the decision demand in reaction to a visual stimulus reduced the speed in the change of direction compared to the planned action. Second, participants performed their action faster in the direction of the throwing arm than against it. The results replicate the effects of decision demands of previous studies and regardless of the reaction to the stimuli being unspecific, further studies could investigate if specific training can reduce the speed loss due to decision demands. The lateral speed differences of cutting manoeuvres of handball players have been analysed for the first time in this study. This effect could have several causes (e.g., coordination, power, motivation) which should be investigated in future studies in more detail.</p></abstract>ARTICLEtrue of Direction Performance and its Physical Determinants Among Young Basketball Male Players<abstract> <title style='display:none'>Abstract</title> <p>The main aim of the present study was to examine the effects of the age group (U-15, U-17 and U-19) on change of direction (COD) performance and its specific physical determinants among young basketball male players. Thirty-one young male basketball players (13–18 years) volunteered to participate in this study. The sample was divided into 3 age groups (U-15, U-17, U-19). All the evaluations were carried out in the same order in 3 sessions as follows: 1) body composition, self-reported sexual maturation, COD performance, and intermittent endurance capacity; 2) reactive strength index (RSI), 15-m sprint, and repeated sprint ability (RSA) test; 3) vertical and horizontal jumps and lower-limb strength. The results showed significant differences between groups for age, sexual maturation, endurance capacity, horizontal and vertical jump performances, RSI, COD, RSA, and lower-limb strength (p &lt; 0.05). Significant correlations were identified between COD performances and some physical determinants such as jumping ability and RSA performance (-0.43 &lt; r &lt; 0.85; p ≤ 0.05). In conclusion, there are age effects on COD performance and its specific physical determinants among young basketball male players. The associations between COD performance and its determinants should be considered by practitioners when programing athletic talent development for this population.</p></abstract>ARTICLEtrue to Improve Pro-Agility Performance: A Systematic Review<abstract> <title style='display:none'>Abstract</title> <p>Effective directional change in sport is imperative to success in key game situations. Change of direction (COD) ability is underpinned by various athletic qualities which can be developed through specific and non-specific training methods. This review examined the effect of specific and non-specific training methods on pro-agility performance, by analysing the intervention type and resulting magnitude of training effects on pro-agility shuttle performance. A total of 20 studies were included for review. Data from 638 subjects and 29 intervention groups involving seven different training methods were extracted and analysed in relation to training method classification and primary outcome measures. Interventions involving sprint training, plyometric training, resistance training, and combined resistance, plyometric, and sprint training were found to produce statistically significant positive change on pro-agility performance per session (p &lt; 0.05). Sprint training (0.108 ES), plyometric training (0.092 ES), resistance training (0.087 ES), and combined resistance, plyometric, and sprint training (0.078 ES) methods were found to have the highest per session training effect. While total time is the typical unit of measure for this test, different types of training may lead to preferential improvements in either acceleration, deceleration, or COD phases of the pro-agility shuttle. Specifically, resisted or inclined sprinting may develop the linear acceleration phases, unilateral resistance training may promote increased strength to overcome the imposed forces during the deceleration and COD phases, multiplanar plyometrics can help enhance stretch-shortening cycle capabilities across different force vectors, and a combination of two or more of these methods may enable simultaneous development of each of these qualities.</p></abstract>ARTICLEtrue Limb Skeletal Robustness Determines the Change of Directional Speed Performance in Youth Ice Hockey<abstract> <title style='display:none'>Abstract</title> <p>The factors that influence the on-ice change of directional speed (COD) of ice hockey players remain unclear. Therefore, this study aimed to determine which off-ice and anthropometric variables determine hockey COD with and without a puck. Thirty-two elite ice hockey players (age: 17.64 ± 1.02 years, body height: 180 ± 7.5 cm, body mass: 76.4 ± 7.8 kg) performed squat jumps, broad jumps, countermovement jumps, and pull-ups and were assessed on agility office and on-ice, with and without a puck. Anthropometric characteristics were determined according to the modified somatotype method. A moderate correlation (r = 0.59–0.6) was observed among all agility tests, between on-ice agility with a puck and lower limb skeletal robustness (r = 0.45), and between on-ice agility with a puck and sit-and-reach scores (r = -0.50). Agility without a puck correlated with squat jump height (r = -0.36). Multiple regression analysis indicated that off-ice agility (β = 0.51) and skeletal robustness of the lower limbs (β = 0.35) determined (R<sup>2</sup> = 0.41) on-ice agility with a puck. Players’ COD was assessed by Illinois tests of agility off-ice and on-ice, with and without a puck; each of these tests moderately predicted the others, but differed in their physical constraints. Players with higher skeletal robustness used more strength and power to achieve COD performance, while players with lower skeletal robustness used techniques and skills to achieve COD, resulting in superior COD performance with a puck compared to stronger athletes. CODs with and without a puck are discrete skills requiring different abilities.</p></abstract>ARTICLEtrue of Direction Deficit: A Promising Method to Measure a Change of Direction Ability in Adolescent Basketball Players<abstract> <title style='display:none'>Abstract</title> <p>The aims of this study were to determine the relationship between vertical jumping performance, linear speed, change of direction speed (CODs) time and the COD deficit (CODD) in adolescent basketball players and to analyze the CODD between faster and slower players based on linear speed performance. Thirty-eight male basketball players (age: 15.47 ± 0.51 years; body height: 185.19 ± 5.67 cm; body mass: 71.87 ± 7.29 kg) completed countermovement jumps (CMJ) with and without an arm swing, squat jumps (SJs), linear sprints at 20 m with split times at 5 and 10 m, the pro–agility test and the zig-zag tests. Furthermore, the CODD was calculated as the difference between the 20 m linear speed result and CODs time in both COD tests. Pearson and Spearman analyses were used to determine the correlations between power-speed-related variables and the CODD. Moreover, independent t-tests and Cohen’s d effect size (ES) were used to analyze the differences between the faster and slower players in the CODD. Moderate to strong significant negative correlations were observed between the CODD in the pro-agility test and linear speed at 5 m, 10 m, and 20 m (r = –0.55 to –0.46), while moderate negative significant correlation was found between the zig-zag CODD and SJs (r = –0.37) as well as small positive significant correlation between the CODD in the zig–zag test and the eccentric utilization ratio (EUR) (r = 0.23). Additionally, faster basketball players displayed significantly higher CODD values performing the pro-agility test. In summary, these findings underline the complexity of COD performance and the importance of remodeling traditional training programs in basketball players.</p></abstract>ARTICLEtrue Demands of a Professional Ice Hockey Team with Special Emphasis on Fatigue Development and Playing Position<abstract> <title style='display:none'>Abstract</title> <p>The aim of this study was to describe the game activity profile of a professional ice hockey team with special emphasis on fatigue development and playing position. Data were collected using a wearable 200-Hz accelerometric system and heart rate (HR) throughout eight official games in a professional ice hockey team (6 defensemen and 11 forwards; n = 122 files). On-ice 10- and 30-m sprint performance, repeated sprint ability and HR responses to the submaximal Yo-Yo Intermittent recovery level 1 test were assessed to determine associations with game performance. Although the 3<sup>rd</sup> period was largely longer than the 1<sup>st</sup> and 2<sup>nd</sup> periods (r = 0.56–0.59), no differences were observed between periods in activity pattern, except a moderate decline in the number of decelerations &lt;-2 m·s<sup>-2</sup> per min (Dec2/min) in the 2<sup>nd</sup> period for forwards (r = 0.06–0.60). Mean HR, time spent &gt;85% HRmax (t85HR), as well as the total number of intense accelerations and decelerations were higher for defensemen. However, demands were similar when expressed relative to time on-ice, except that defenders performed more Dec2/min than forwards in all periods, whereas forwards spent more t85HR during the 2<sup>nd</sup> period (r = 0.46–0.57). Time spent on ice was inversely correlated with the total number of accelerations (Acc<sub>tot</sub>), accelerations &gt;2 m·s<sup>-2</sup> per min (Acc2/min), total decelerations per min (Dec<sub>tot</sub>/min), Dec2/min and t85HR (r = -0.63 to -0.18) and positively correlated with mean HR and peak HR (r = 0.20– 0.53). No significant correlations were found between physical fitness and game activity variables scaled by individual time on ice. Absolute acceleration and HR demands of professional ice hockey seem to differ between playing positions, but not in relation to time on ice. Further, no clear signs of fatigue were captured, possibly due to the longer duration of rest intervals in the 3<sup>rd</sup> period.</p></abstract>ARTICLEtrue Mechanical and Efficiency Constraints when Swimming Front Crawl with the Aquanex System<abstract><title style='display:none'>Abstract</title><p>The aim of this study was to compare the mechanical and efficiency constraints between free swim and swimming with differential pressure sensors (Aquanex System). These conditions were also analysed to understand the differences between sexes. Thirty young swimmers, 14 boys and 16 girls (12.31 ± 0.67 years) performed three 25-m front crawl maximal bouts under each condition: free swim and swimming with sensors. Under the condition with sensors, swimmers carried the Aquanex System composed of two hand pressure sensors (v.4.1, Model DU2, Type A, Swimming Technology Research, Richmond, VA, USA). The 25-m time (T25) was assessed as a swimming performance variable. The swimming velocity (v), stroke rate (SR), and stroke length (SL) were assessed and calculated as stroke mechanics variables. Thereafter, the stroke index (SI) and arm stroke efficiency (<italic>η</italic><sub>F</sub>) were estimated for swimming efficiency. Statistical significance was set at p ≤ 0.05. Swimming performance was impaired when swimmers swam with sensors (overall: p = 0.03, d = 0.14; Δ = 1.30%) and a significant decrease in v was found for overall (p = 0.04, d = 0.14; Δ = 1.42%) and the girls’ group (p &lt; 0.01, d = 0.39; Δ = -1.99%). The remaining stroke mechanics variables showed no differences between conditions, as well as for swimming efficiency. Furthermore, there were no differences between girls and boys in free swim and with sensors for all variables. Swimming with the Aquanex System seems not to impose constraints in the mechanics and efficiency of young swimmers, despite differences in swimming performance and v.</p></abstract>ARTICLEtrue and Power Performance Changes During an In-Season Resistance Training Program in Elite Futsal Players: A Case Study<abstract> <title style='display:none'>Abstract</title> <p>In this study, we aimed to analyze (i) the strength and power changes after resistance training (RT) in elite futsal players, and (ii) the associations between the session rate of perceived exertion (sRPE) and perceived total quality recovery (TQR), and the sRPE and TQR with the volume load of the RT program. Ten elite futsal players (24.8 ± 5.4 years; 76.2 ± 7.1 kg; 1.77 ± 0.05 m) performed an in-season 8-week RT program twice per week. RT consisted of 2-3 sets x 3-6 reps at 45-65% of one-repetition maximum (1RM) with maximal velocities in the full squat and complementary exercises with the same volume. We assessed the TQR before every session, while the sRPE was calculated after each RT session. One week before and after the intervention, we measured the countermovement jump (CMJ) height, isometric hip adduction strength (IHAS), 1RM, and peak power (PP) in the full squat progressive loading test. After the 8-week training program, there was a significant improvement in most outcomes, yet the gains (%Δ) remained below the minimal detectable change (MDC), except for IHAS (CMJ: p &lt; 0.05, %Δ = 6.7, MDC% = 7.2; IHAS: p &lt; 0.001, %Δ = 19.1, MDC% = 14.6; 1RM: p &gt; 0.05, %Δ = 9.2, MDC% = 21.5; PP: p &lt; 0.05; %Δ = 14.4, MDC% = 22.4). We also found a significant negative correlation between TQR and the sRPE (r = -0.45, p &lt; 0.001). Our data suggest that RT based on low-volume and low-to-moderate loads may not produce a sufficient stimulus to induce meaningful dynamic strength and power gains in elite futsal players, although it improves isometric strength. Furthermore, monitoring TQR before sessions may show coaches how the elite futsal player will perceive the session's intensity.</p></abstract>ARTICLEtrue of Masticatory Muscles Asymmetry and Oral Health with Postural Control and Leg Injuries of Elite Junior Soccer Players<abstract> <title style='display:none'>Abstract</title> <p>The influence of asymmetry between masticatory muscles on postural control is still under debate and only few studies examined the impact of oral health on injury risk. The present study investigated the relationships between masticatory muscles asymmetry, oral health, postural control and the prevalence of (non-contact or traumatic) leg injuries in a sample of 144 male elite junior soccer players. sEMG of the masseter and temporal muscles was performed during maximum teeth clenching, postural control was tested by measuring sway velocity during the unipedal stance with eyes closed, while oral health and the number of leg injuries were assessed using a questionnaire. The time-1 assessment was repeated in a subgroup of 69 players after one year. Pearson and partial correlation coefficients and adjusted odds ratios (OR) were used to assess associations. Asymmetry between the masseter and temporalis muscles (AMTM, quantified as anteroposterior coefficient, APC) was associated with higher sway velocity on the dominant leg (using time-1 data partial r = -0.24, p = 0.004, using longitudinal data partial r = -0.40, p = 0.005). Higher prevalence of two or more leg injuries throughout a competitive season was associated with poor oral health (adjusted OR (95%CI) using time-1 data = 2.14 (1.02–4.46), using longitudinal data = 4.47 (1.25–15.96)). These results indicate that AMTM has a negative influence on the sway velocity of the dominant leg only, possibly because frequent balancing exercises on the non-dominant leg may counteract negative influences of AMTM. The association of oral health with leg injuries underlines the need for oral health promotion and monitoring strategies in sports.</p></abstract>ARTICLEtrue of the Playing Time Benefits of Foreign Players in the Big-5 European Football Leagues<abstract><title style='display:none'>Abstract</title><p>To explore the benefits that foreign players bring to their clubs, this study used foreign players in the Big-5 European leagues (2013/2014-2017/2018 seasons) as samples and constructed a benefit model based on playing time and game points to evaluate the contribution of foreign players to their clubs in different leagues. The results showed the following: 1) from the 2013/2014 season to the 2017/2018 season, foreign players in the Bundesliga had the highest playing time benefits (PTBs) (0.526 ± 0.012), followed by foreign players in La Liga (0.523 ± 0.014), the Premier League (0.518 ± 0.011), Serie A (0.500 ± 0.012) and Ligue 1 (0.486 ± 0.011); 2) foreign players from South America had the highest PTBs in the Big-5 leagues, while those from Africa had the lowest PTBs. However, among the different leagues, there were no significant differences in the PTBs of foreign players from the same continent; 3) PTBs of foreign players in the forward position were lower than those of foreign players in the defender position; 4) the country that produced foreign players in the Big-5 leagues with the highest total PTBs was Brazil, followed by Argentina, Spain and France. Additionally, the top 15 countries by total PTBs qualified for either the 2014 or the 2018 World Cup Final.</p></abstract>ARTICLEtrue of Upper Trapezius Myofascial Trigger Points on Scapular Kinematics and Muscle Activation in Overhead Athletes<abstract> <title style='display:none'>Abstract</title> <p>Prolonged overactivity of the upper trapezius muscle with myofascial trigger points might cause muscle fatigue and subsequently change scapular kinematics and associated muscular activities. Scapular kinematics and associated muscular activities were investigated in 17 overhead athletes with upper trapezius myofascial trigger points and 17 controls before and after a fatigue task. Participants performed a fatigue task requiring sustained isometric scapular elevation. The outcomes included scapular kinematics (upward/downward rotation, external/internal rotation, posterior/anterior tilt) that were tracked by the Polhemus FASTRAK (Polhemus Inc., Colchester, VT, USA) system with Motion Monitor software and muscular activities (upper trapezius, lower trapezius and serratus anterior) that were collected at 1000 Hz per channel using a 16-bit analog-to-digital converter (Model MP 150, Biopac systems Inc., CA, USA) with pairs of silver chloride circular surface electrodes (The Ludlow Company LP, Chocopee, MA) during arm elevation. Mixed ANOVAs were conducted to characterize the outcomes with and without a fatigue task in participants with myofascial trigger points. Decreased scapular posterior tipping during 90 degrees of arm raising/lowering (effect sizes of 0.51 and 0.59) was likely to be elicited by the scapular elevation fatigue task in the presence of myofascial trigger points. Activity of the lower trapezius was higher in the myofascial trigger point group (6.2%, p = 0.036) than in the control group. Following the fatigue task, both groups showed increased activity in the upper trapezius (9.0%, p = 0.009) during arm lowering and in the lower trapezius (2.7%, p &lt; 0.01) during arm raising and lowering. Decreased scapular posterior tipping during 90 degrees of arm raising/lowering after a fatigue task may lead to impingement. We found that the presence of upper trapezius myofascial trigger points in amateur overhead athletes was related to impaired scapular kinematics and associated muscular activities during arm elevation after a fatigue task, especially the decreased scapular tipping during 90 degrees of raising/lowering.</p></abstract>ARTICLEtrue of Jumper’s Knee with Extracorporeal Shockwave Therapy: A Systematic Review and Meta-Analysis<abstract> <title style='display:none'>Abstract</title> <p>The aim of this systematic review and meta-analysis was to determine the therapeutic efficacy of extracorporeal shockwave therapy (ESWT) for athletes with patellar tendinopathy. We searched PubMed, EBSCOHost and Ovid for randomized controlled trials (RCTs) which evaluated the therapeutic efficacy of ESWT in athletes with jumper’s knee. The methodological quality of RCTs was rated with the Physiotherapy Evidence Database scale. Data in the meta-analysis were expressed as standardized mean difference (SMDs) and 95% confidence intervals (CIs). Heterogeneity was assessed with I<sup>2</sup> statistics. Of 192 records identified, a total of seven articles met the inclusion criteria. The ESWT and control groups with any other conservative treatment did not differ significantly with respect to the Visual Analogue Scale (VAS) long-term scores obtained at ≥ 6 months of therapy completion (SMD: -0.33; 95% CI: -4.64 to 3.98; p = 0.87; I<sup>2</sup>= 98%). Furthermore, no significant differences were found between the ESWT and control groups regarding the pooled Victorian Institute of Sports Assessment for Patella (VISA-P) scores for long-term outcomes (SMD: 8.21; 95% CI: -39.3 to 55.73; p = 0.73; I<sup>2</sup>= 99%). The ESWT and control groups did not differ significantly on the VAS and VISA-P scores for long-term outcomes. In both cases, heterogeneity was considered to be high. Hence, no clear and generalized conclusions can be drawn regarding ESWT effectiveness in athletes with patellar tendinopathy.</p></abstract>ARTICLEtrue of Elevated Body Temperature on Selected Physiological Indices and Thermal Stress in Athletes and Non-Athletes<abstract> <title style='display:none'>Abstract</title> <p>The purpose of this study was to determine the effects of active and passive overheating. A group of athletes (A) and non-athletic men (N) underwent an exercise stress test at elevated ambient temperature and sauna bathing until an increase in rectal temperature of 1.2°C was observed. It was shown that group A performed physical exercise for a longer period of time, which elicited significantly higher amounts of work performed in the stress test. Both forms of overheating caused a significant decrease in BM and a significant change in plasma volume, while greater dehydration was observed after active overheating. Changes observed in group A were higher than in group N. MCV levels were initially higher in group A. The levels in both groups decreased after sauna bathing, although in non-athletes the decrease was greater. Both forms of overheating increased Hb, HCT, and SBP, while only the non-athletic group showed a decrease in DBP after the exercise stress test. However, a decrease in DBP was observed in both groups after sauna bathing. The PSI increased after both tests, yet to a higher extent after the stress test than after sauna bathing. The PSI was negatively correlated with VO<sub>2max</sub> in both groups. The increase in cortisol concentration was higher after sauna bathing. There was a correlation between cortisol levels and the work performed during the stress test in group A. Endurance training resulted in more efficient thermoregulatory mechanisms in athletes.</p></abstract>ARTICLEtrue