Journal of Human Kinetics最新文献

The purposes of this study were to characterize the magnitude and the direction of inter-limb asymmetries in elite youth female basketball players and to evaluate any associations with indicators of change-of-direction (COD) performance. Eighteen elite youth female basketball players (17.79 ± 0.67 years; 71.10 ± 7.43 kg; 1.82 ± 0.07 m; 23.01 ± 1.69 kg∙(m²)^-1) participated in a battery of tests, including 70° and 180° COD, single-leg countermovement jump (SLCMJ), and single-leg drop jump (SLDJ) tests. Inter-limb asymmetry indices (ASIs) were calculated, and correlations with COD performance indicators were examined. The results indicated significant differences between dominant and non-dominant limbs in all tasks, with ASI values ranging from 3.02% to 27.8%. Directionality of asymmetry varied across tests. Correlation analysis revealed that greater asymmetry was associated with slower COD performance (ρ range = -0.67 to 0.57). Moreover, asymmetry in some tasks was related to lower ground reaction forces (GRFs) (ρ range = -0.60 to -0.42) and higher contact times during COD 180° (ρ = 0.45). The results of this study support the need to address inter-limb asymmetries in basketball players. Coaches and practitioners should consider targeted interventions to minimize asymmetry and enhance COD skills. A comprehensive battery of fitness assessments is recommended to provide a holistic understanding of inter-limb asymmetries.

This study compared male amateur basketball players with asymptomatic patellar tendon tendinopathy (ASYM) to healthy controls (CON) during simulated games to explore the differences in patellar tendon force (PTF) and related metrics. Data on kinematics, kinetics, and electromyography were collected from 24 participants, comprising 12 in the ASYM group and 12 in the CON group, performing a stop-jump task in four stages (1^st, 2^nd, 3^rd, 4^th). A musculoskeletal model was used to calculate PTF, and Orthogonal Partial Least Squares Discriminant Analysis (OPLS-DA) identified significant variables. In the first three stages, the ASYM group showed significantly greater PTF and the ankle discrete relative phase (ADRP) than the CON group, with differences of 0.98, 0.79, 0.81kg•BW^-1 (p < 0.001) and 7.34°, 11.24°, and 2.49° (p < 0.05), respectively. In the last three stages, the ASYM group had a higher knee co-activation index (KCAI) than the CON group, with differences of 0.33, 0.28, and 0.25 (p < 0.05). Correlations between PTF and the ADRP and between PTF and the KCAI were the highest, at 0.58 and 0.61, respectively. The OPLS-DA model effectively distinguished between the groups, suggesting potential applications in tendon health monitoring. The findings suggest that elevated PTF may be linked to tendinopathy in male amateur basketball players, highlighting the importance of comprehensive strategies, such as improving ankle symmetry and optimizing muscle coordination to mitigate tendon load and injury risk.

This study aimed to compare: 1) the effects of a 4-week unresisted vs. resisted sprint training programs (UST and RST with 50% body mass, respectively) on both resisted and unresisted sprint performance; and 2) the effects of these sprint training schemes on various strength-power measures (i.e., one-repetition maximum [1RM] and the isometric squat test (ISqT), eccentric hamstring strength in the Nordic hamstring exercise [NHE], and vertical and horizontal jump distances). Thirty-five under-19 male academy rugby players participated in the study and were randomly assigned to one of the two training groups. Players' unresisted and resisted (50% BM) 30-m sprint performance, squat 1RM, ISqT, NHE, and jump capabilities were tested on different occasions. Only UST produced a significant reduction in unresisted 30-m sprint time (p < 0.05), whereas both groups exhibited significant changes in resisted sprint times at 10 m and 30 m, as well as maximum velocity (p < 0.005; ES: large). Regarding strength measures, RST led to significant increases in ISqT peak force, horizontal jump distance, and NHE strength (p < 0.011; ES: large). Overall, no significant differences were detected between UST and RST in any of the primary or secondary measures after the intervention. Both training methods were equally effective in improving resisted sprint performance in youth male rugby players. Moreover, UST and RST could be effective options for maintaining or even improving various neuromuscular measures (e.g., dynamic-explosive, isometric, and eccentric strength) when lower limb resistance training is reduced during the competitive season due to the congested schedule.

This study investigated the between-session variability and concurrent validity of the relative load-velocity relationship obtained from different methods during the free-weight back squat. In counterbalanced order, 39 resistance-trained male participants performed two sessions with six different loads (i.e., a multiple-point test) and two sessions with two different loads (i.e., a 2-point test) followed by the actual one-repetition maximum (1RM) attempts. The mean velocity (MV) corresponding to various %1RMs (at every 5% interval from 40 to 90%1RM) was determined through individualized linear regression models using three methods: (i) multiple-point: data of ~40, 50, 60, 70, 80, and 90%1RM from the multiple-point test, (ii) non-field 2-point: data of the lightest and heaviest loads from the multiple-point test, and (iii) field 2-point: data of ~40 and 90%1RM from the 2-point test. The main findings revealed that the between-session variability of the MVs derived from the %1RM-MV relationships was low (absolute differences = 0.02‒0.03 m•s^-1) and similar (p = 0.074‒0.866) across the three methods. Additionally, when compared to the multiple-point method, both the non-field and field 2-point methods showed high correlations (pooled r across all %1RMs = 0.95 ± 0.01 and 0.72 ± 0.09, respectively) and small systematic biases (ranging from -0.01 to 0.01 m•s^-1). Therefore, we recommend that strength and conditioning practitioners use the %1RM-MV relationship, modeled by the field 2-point method, as a quicker and fatigue-free procedure for prescribing the relative load during the free-weight back squat. Specifically, a light load near 40%1RM and a heavy load near 90%1RM are suggested for this method.

This study aims to examine the tactical behavior, decision-making, and technical skills of young novice basketball players in small-sided games (SSGs) with different numerical configurations and court sizes. Participants were 16 novice male players aged between 11 and 15 years with no competitive experience. A total of 13 games were played, comprising nine SSG formats with numerical equality, superiority, and inferiority, in two court sizes: a full court (FC) and a half court (HC). In SSGs played in the FC, pass efficacy was significantly higher (p < 0.05) in 5 vs. 4 and 4 vs. 3 formats, while dribble efficacy was significantly higher (p < 0.05) in the 2 vs. 1 HC format. The 3 vs. 3 FC format showed greater (p < 0.05) shot efficacy. Reception efficacy was significantly higher (p < 0.05) in the 2 vs. 1 HC format, as well as rebound efficacy. However, appropriate passes were significantly lower (p < 0.05) in the 4 vs. 3 FC format. Dribble efficacy was significantly greater (p < 0.05) in the 2 vs. 1 HC format and appropriate shots were significantly greater (p < 0.05) in the 2 vs. 1 HC format. Regarding defensive and offensive technical-tactical actions, the 3 vs. 3 HC format presented significantly higher values (p < 0.05) of support, while ball marking was significantly greater (p < 0.05) in the 3 vs. 2 HC format. In conclusion, this study indicates that smaller (balanced and unbalanced) SSG formats tend to enhance the frequency, effectiveness, and appropriateness of attacking and defensive behaviors, particularly those involving direct actions.

The human pelvis is subjected to forces generated by abdominal muscles. Pelvic asymmetry (PA) might therefore be related to the asymmetrical postural activity of the lateral abdominal muscles (LAMs: transversus abdominis (TrA); internal oblique (IO); external oblique (EO)). The main aim of this study was to evaluate the potential relationship between PA, expressed by the asymmetry index in the frontal (PAIf) and sagittal (PAIs) planes and LAM postural activity as described by the tissue deformation index (TDI). A group of 126 healthy volunteers (59 females) was involved. Positions of the anatomic landmarks for PA measurement were registered by the motion capture system. The response of LAMs to postural disturbation was recorded using the M-mode ultrasounds. We found weak negative correlations between PAIf and TDI values as well for the right and the left side of the body except for EO muscle (PAIf-TRA right: r = -0.11, left: r = -0.06; PAIf-IO right: r = -0.15, left: r = -0.10; PAIf-EO right: r = 0.02, left: r = 0.12). On the contrary, analysis between PAIs and TDI values revealed weak positive correlations, also except for EO muscle (PAIf-TRA right: r = 0.004, left: r = 0.003; PAIf-IO right: r = 0.05, left: r = 0.06; PAIf-EO right: r = 0.07, left: r = -0.02). For all tested correlations, we recorded non-significant outcomes (all p > 0.05). We found no evidence to support the claim that PA is related to the LAM activity in the group of young, healthy, and active people.

Numerous studies have investigated physical and motor performance during dual-task protocols in different sports. However, only few studies have investigated tactical performance in dual-task situations in real-world game situations, such as small-sided games (SSGs). Moreover, sport-specific literature is unclear about the effects of motor or cognitive secondary tasks and the type of the stimulus (memorization, math operations) on players' tactical performance. This study considered the impact of dual tasks on soccer players' tactical performance within SSGs and compared the effects of motor and cognitive secondary tasks on soccer players' tactical performance. A total of 24 U-13 soccer players (12.34 ± 0.55 years) took part in the study, playing SSGs under four different conditions: a single task (ST) condition: players performed only SSGs; a motor dual-task (MDT) condition: players performed SSGs while balancing a basketball ball on a cone; a cognitive dual-task 1 (CDT1) condition: players performed SSGs while doing math operations; a cognitive dual-task 2 (CDT2) condition: players performed SSGs while doing a memorization task. Tactical performance was assessed using the FUT-SAT under all experimental conditions. Players showed higher tactical performance in SSGs with a ST than SSGs with secondary tasks (p < 0.001). When comparing secondary tasks in SSGs, players presented a better tactical performance in SSGs with cognitive secondary tasks than in SSGs with a motor secondary task (p = 0.02). In conclusion, dual tasks impair the tactical performance of soccer players, with the motor secondary task inducing greater impairment than secondary cognitive tasks.

This study explored the impact of different tactical formations (TFs) on positional team behaviors in youth soccer during small sided games (SSGs). Eighteen U19 players participated in 7-a-side SSGs including goalkeepers, alternating between 2-3-1 and 3-1-2 TFs against a consistent opponent in the 3-3 TF. Positional data were collected with WIMU PRO GPS devices (Hudl, USA) to assess collective offensive and defensive dimensions that included teams´ width, length, height, the stretch index, and the surface area. The Mann-Whitney U test revealed that teams employing a 2-3-1 TF in offensive play exhibited increased height (p < 0.001; ES = 0.206), width (p = 0.006; ES = 0.113), and the surface area (p = 0.023; ES = 0.093) compared to the 3-1-2 TF. Conversely, defending with a 2-3-1 TF increased team height (p < 0.001; ES = 0.287) while decreasing length (p < 0.001; ES = 0.189), the surface area (p = 0.005; ES = 0.161), and the stretch index (p < 0.001; ES = 0.183) compared to the 3-1-2 TF. When attacking against a 2-3-1 TF, the offensive team experienced reduced height (p = 0.007; ES = 0.116) but an increased surface area (p < 0.001; ES = 0.241), width (p < 0.001; ES = 0.378) and the stretch index (p < 0.001; ES = 0.326) compared to the 3-1-2 TF. Finally, defending against a 2-3-1 TF resulted in decreased team length (p < 0.001; ES = 0.205), the surface area (p < 0.001; ES = 0.271) and the stretch index (p < 0.001; ES = 0.205) compared to defending against a 3-1-2 TF. Thus, coaches should acknowledge the significant role of TFs in modulating positional behaviors during SSGs, with relevant pedagogical implications for designing effective training sessions.

This study aimed to assess the effects of two different pitch dimensions on physical fitness responses and time-motion characteristics in young soccer players during the in-season period. Thirty-nine participants were randomly assigned to two playing areas: a 90 m² (PD90, n = 19) and a 180 m² (PD180, n = 20) area per player. During the eight-week soccer-specific high-intensity interval training (HIIT) intervention, both groups performed four bouts of 5-a-side games (SSGs) in two different pitch dimensions of 5 min with 3 min active rest intervals between games. The heart rate (HR), total distance (TD) and distances covered while walking (WLK), jogging (JOG), low-speed running (LSR), high-speed running (HSR), and sprinting (SPR) were recorded during SSGs. Before and after the intervention, the following tests and variables were completed and evaluated: physical work capacity (PWC170), the Wingate anaerobic test, the lactate threshold (LT), 5-m, 20-m, and 30-m sprint tests. Significant between-groups differences were found post-intervention in PWC170 (p = 0.018, ES = 0.15) and the 5-m sprint (p = 0.002, ES = 0.24). Greater playing areas could be more beneficial in developing aerobic fitness, while SSGs on smaller pitch sizes improve the ability of short-distance accelerations.

Visual information is crucial for motor control during a jump-landing, allowing for anticipation of landing timing and prediction of the impact. However, the effects of visual occlusion on lower extremity biomechanics are not well understood. To investigate this, we studied the impact of visual occlusion on motor control during a low-intensity single-leg landing. Seventeen female college students participated in the controlled laboratory investigation. They performed low-intensity repetitive vertical hopping on a single leg under eyes-open (EO) and eyes-closed (EC) conditions. Main outcome measurements were taken, including jump height, ground reaction forces, joint angles, and joint moments, using a motion capture system. The significant effects of visual occlusion were as follows: 1) a decrease in the hip flexion angle at ground contact (p = 0.02), 2) an increase in Fx (medio-lateral ground reaction force), knee valgus, and internal rotation angles in the early phase within 80 ms after ground contact (p < 0.05), and 3) an increase in Fz (vertical ground reaction force) and a reduction in hip and knee flexion angles at peak Fz (p < 0.05). The amount of angular change at the ankle joint correlated with the hip and knee joints only under the EC condition (p < 0.05). These changes indicate modifications in landing strategy for safety and/or deficiencies in control for an efficient and accurate landing. In conclusion, visual information contributes to safe and accurate motor control during low-intensity landing movements.