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Most sports and leisure activities involve repetitive movements in the upper limb, which are typically linked to pain and discomfort in the neck and shoulder area. Movement variability is generally expressed by changes in movement parameters from one movement to another and is a time-dependent feature of repetitive activities. The purpose of this study was to examine the effect of repeated movement-induced fatigue on biomechanical coordination and variability in athletes with and without chronic shoulder pain (CSP). In this controlled laboratory study, 24 overhead athletes in two groups of athletes with ( N  = 12) and without ( N  = 12) CSP were recruited. Biomechanical and Electromyographical data were recorded while the athletes were asked to perform repeating reaching tasks (RRT). Kinematic data was recorded every 30 s of the minutes of the repetitive pointing task (RPT). The kinematic and electromyography data were recorded at the first 30 s of “Fatigue-Terminal” (FT) and the last 30 s of “No-Fatigue” (NF) in the repetitive pointing task (RPT). Raw data was analyzed by using MATLAB code to extract the relevant coordination and movement variability data. Different fatigue conditions led to significant kinematic changes during the repetitive pointing task. In the CSP group, trunk lateral flexion decreased after fatigue, while it increased in the CON group ( p  < 0.013). Trunk rotation and shoulder elevation angles were smaller before fatigue than after in both groups ( p  < 0.001). Variability in joint angles, including trunk lateral flexion and elbow flexion, increased after fatigue, indicating less stability in movement patterns ( p  < 0.001). The coordination between trunk movement and shoulder elevation was altered post-fatigue, with significant changes in EMG variability for muscles like the Lower Trapezius and Long Head of the Biceps ( p  < 0.001). Results of our study indicate that both groups were able to accomplish fatigue, but they employed different movement strategies. The CSP group primarily focused on controlling the shoulder joint, while the CON group utilized both the shoulder and elbow joints in their strategy. This difference suggests that individuals in the CSP group who experienced chronic pain may have developed a strategy to minimize pain and fatigue during the task. Specifically, the CSP group’s approach appeared to involve adjustments in movement patterns to manage the task despite fatigue. This adaptation contrasts with the CON group’s more complex movement strategy, which involved greater variability and adjustments in both the shoulder and elbow joints.

It has been indicated that dual tasks may multiply the possibility of injuries due to divided attention. This study aimed to investigate the effect of dual-task on kinematics and kinetics of jump landing in female athletes with and without dynamic knee valgus. In this study, 32 recreational athletes between 18 and 30 years old were recruited and divided into with (n = 17) and without (n = 15) dynamic knee valgus groups. The 3-D positions of retroreflective markers were recorded at 200 Hz using a 8-camera Kestrel system (Motion Analysis Corporation, Santa Rosa, CA), while ground reaction forces were synchronously recorded at 1000 Hz using 2 adjacent force plates (FP4060-NC; Bertec Corporation, Columbus, OH). Kinematics and kinetics of jump landing were recorded while counting backward digits as a dual task, and also without counting backward digits as a single task. One-way repeated measures of variance were used to analyse data at the significant level of 95% (α < 0.05). The study found that the dual-task affected the angles and moments of hip, knee, and ankle joints ( P  < 0.05) in both groups. Additionally, the effect of the dual-task differed significantly between the two groups in the angles hip flexion ( P  < 0.001), knee abduction ( P  < 0.001), and ankle internal rotation ( P  = 0.001), as well as the moments hip flexion ( P  < 0.001), hip abduction ( P  = 0.011), knee flexion ( P  = 0.017), knee internal rotation ( P  < 0.001), ankle dorsiflexion ( P  = 0.046), ankle eversion ( P  < 0.001), and ankle internal rotation ( P  = 0.046). Athletes with dynamic knee valgus may have been less able to protect themselves during the landing and are more prone to lower extremities injuries. As a result, using kinematics and kinetics in athletes with dynamic knee valgus during landing may help identify potential mechanisms associated with risk factors of lower extremity injuries and ACL injuries as well.

Athletes with Subacromial Impingement Syndrome (SIS) exhibit altered muscular coordination and variability during repetitive shoulder movements compared to athletes without SIS. This research compared the Coordination and Variability of Muscular Activation in Male Athletes with and Without SIS. In this case-control study, twenty-four male athletes were recruited and divided into two groups: those with SIS (n = 12) and those without SIS (n = 12). Participants performed a repetitive reaching task (RRT) for a minimum of fifteen repetitions. Electromyography (EMG) data were recorded from selected shoulder muscles. Muscle synergies, intra-group variability, and inter-group variability were extracted from the EMG data. An independent sample t-test or Mann-Whitney U-test was employed to analyze data at a significance level of 95% (α < 0.05). Three observable muscle synergy patterns were identified in both groups. Significant differences in variance accounted for (VAFmuscle) were found in the posterior deltoid, subscapular, and middle deltoid muscles, but these differences may not be clinically significant and warrant further research. No significant statistical differences were found in intra-group variability between the groups, which may suggest that the hypothesis is not fully supported. However, significant differences in inter-group variability were observed between the SIS and control (CON) groups. This study showed differences in muscular coordination and variability during RRT in athletes with and without SIS. Three different muscle synergy patterns were demonstrated in both groups. It seems that timing and coordination changes in muscle activation may influence movement efficiency and increase the risk of performance errors.

Typically, athletes alter movement mechanics in the presence of back pain, but the effect of these changes on lower extremity injury risk is not well understood. This study aimed to compare the effect of fatigue on electromechanical response times during a choice reaction task in basketball players with and without persistent low back pain. Twenty-four male basketball players participated. Total reaction time (TRT), premotor time (PMT), and electromechanical delay (EMD data were recorded before and after fatigue. The chronic low back pain (CLBP) group had significantly longer EMD in Med gastrocnemius ( p  = 0.001) and Tibialis anterior ( p  = 0.001), and shorter EMD in Vastus Lateralis ( p  = 0.001), Vastus Medialis Oblique ( p  = 0.003), and Semitendinosus ( p  = 0.025) muscles after fatigue. PMT in the CLBP group had longer than the Non-CLBP in Vastus Lateralis ( p  = 0.010), Vastus Medialis Oblique ( p  = 0.017), Semitendinosus ( p  = 0.002). Also, TRT was longer in knee flexion ( p  = 0.001) and ankle plantarflexion ( p  = 0.001) muscle groups. The different effects of fatigue on electromechanical response times of the knee and ankle in people with CLBP may represent the effect of an axial injury on lower extremity injury risk factors in situations of higher cognitive load, similar to competitive play.

Background Scapulothoracic motion during arm elevation involves scapular posterior tilt (PT), upward rotation (UR), and external rotation (ER). Abnormal scapular kinematics are common in people with chronic shoulder pain, potentially exacerbating symptoms and impairing function. Push-ups, a common exercise for shoulder rehabilitation, may influence scapular motion but have not been extensively studied in this context. Thus, this study aimed to investigate the effect of hand position on scapular kinematics during a push-up exercise in athletes with and without chronic shoulder pain (CSP). Methods Twenty-four male overhead athletes were allocated into two groups: CSP ( n  = 12) and Control (CON; n  = 12). Scapular kinematics in three planes (PT, UR, and ER) were measured using a Vicon motion capture system during push-ups in three hand positions (internal rotation, IR; neutral rotation, NR; and external rotation, ER). Measurements were taken in the concentric phase of the push-up. Statistical analyses using repeated-measures ANOVA assessed the effects of hand position and elbow extension on scapular kinematics between the two groups. Results For PT of the scapula, in the IR hand position, participants from both the CON and CSP groups showed similar decreases (CON group = from 25.74° to -16.10°; P  < 0.001). In the NR hand condition, the CON group decreased PT from 16.12° to -15.98° ( P  < 0.001), but there was no significant change in the CSP group. In the ER hand condition, for the CON group, PT decreased from 18.63° to -9.38° ( P  < 0.026), with no significant change observed in the CSP group. For UR of the scapula, the CON group showed significant decreases in the IR hand condition (from 15.37° to -2.28°; P  < 0.019), while the CSP showed minimal changes. In the IR hand condition, the ER of the scapula increased from 20.44° to 25.13° ( P  < 0.003) in the CON group. At the same time, the CSP showed smaller changes. In the NR hand condition, ER of the scapula in the CON group decreased from 24.79° to 9.38° ( P  < 0.001), with no significant change observed in the CSP group. Conclusion Scapular kinematics (UR, PT, and ER) differed significantly across hand rotation conditions and groups. The CON group exhibited more pronounced changes in these kinematic measures, while the CSP group showed limited variation. This may indicate an association between chronic pain and movement restriction. These findings emphasize the need for targeted rehabilitation strategies that consider these kinematic differences.

Background Regarding their skill levels, badminton players present different movement patterns during front and right lunging. The main objective of this study was to compare the mechanical energy transfers attributable to right-forward lunges between amateur and professional badminton players to study variations in mechanical efficiency at various skill levels. Method In this cross-sectional study, twenty female badminton players were recruited (Professional group n = 10 and Amateur group n = 10). The kinematics and kinetics of the lower extremities were recorded while performing right-forward lunges using Vicon motion capture and Kistler force plates. Mechanical energy expenditures (MEE) were extracted in eccentric transfer, concentric transfer, and no-transfer phases for the hip, knee, and ankle joints. At each joint, mechanical energy compensations (MEC) were also determined. Independent samples t-tests were used to analyze data at a significance level of α = 0.05. Result Regards to mechanical energy expenditures at the initial heel contact phase, the professional players demonstrated statistically significant more ankle no-transfer (p < 0.003), less knee concentric transfer (p < 0.026), more knee eccentric transfer (p < 0.001), and less hip no-transfer (p < 0.001). At the same time, the amateur athletes showed significantly more ankle eccentric transfer (p < 0.042) at maximal knee flexion angle time point. Analyzing mechanical energy compensation coefficients showed that the professional athletes had significantly less ankle concentric transfer (p < 0.001), more knee concentric transfer (p < 0.001), more knee eccentric transfer (p < 0.001), and more hip eccentric transfer (p < 0.001) at initial contact phase. While they found to have significantly more ankle eccentric transfer (p < 0.007), less knee concentric transfer (p < 0.001), less knee eccentric transfer (p < 0.001), more hip concentric transfer (p < 0.001), and more hip eccentric transfer (p < 0.001) at maximal knee flexion angle. Conclusion it is shown that the mechanical energy efficiency of the right-forward lunge is skill-related. It seems that altered lunge landing biomechanics may increase the risk of ankle and knee injuries and muscular damages in amateur athletes. It is recommended for amateur players to follow a injury prevention training program that promotes proper lunging technique.

Background The purpose of this study was to examine the association of sacroiliac joint (SIJ) dysfunction and pain with overuse and acute lower limb and pelvic girdle injuries of Iranian basketball players. Methods In this cross-sectional study, basketball-related injury data were collected during 2019–2020 from 204 basketball players of the Iranian league using the online Information Retrospective Injury Questionnaire. A researcher then performed ten clinical tests to assess SIJ dysfunction and pain (five tests for dysfunction and five tests for pain). Data analysis was performed by logistic regression at the confidence interval of 95%. Results Within our sample (n = 204), injury rates were calculated across sub-groups of athletes that had only SIJ pain (n = 19), only SIJ dysfunction (n = 67), both SIJ pain and dysfunction (n = 15) or no SIJ complaints (n = 103). Across these groups, a total of 464 injuries were reported. SIJ pain group reported 80 injuries (17.2%), SIJ dysfunction group reported 210 injuries (45.2%), both SIJ pain and dysfunction group reported 58 injuries (12.5%, and the no SIJ pain or SIJ dysfunction group reported 116 injuries (25.0%). Participants with SIJ pain were more likely to report previous pelvic girdle injuries (overuse: odds ratio (OR): 0.017; 95% CI: 0.005–0.56; p < 0.001 and acute: OR: 0.197; 95%CI: 0.101–0.384; p < 0.001) and also lower limb injuries (overuse: OR: 0.179, 95%CI: 0.082–0.392, p < 0.001). Participants with SIJ dysfunction only were likely to report acute pelvic girdle injuries (OR: 0.165; 95%CI: 0.070–0.387; p < 0.001) and acute lower limb injuries (OR: 0.165; 95%CI: 0.030–0.184; p < 0.001). Conclusion The presence of SIJ dysfunction and pain is associated with a history of acute and overuse injuries in the pelvic girdle and lower limb. Thus, SIJ dysfunction and pain should be specifically evaluated and addressed when designing rehabilitation programs for sports-related injuries.

Due to the substantial decrease of water resources as well as the increase in demand and climate change phenomenon, analyzing the trend of hydrological parameters is of paramount importance. In the present study, investigations were carried out to identify the trends in streamflow at 20 hydrometric stations and 11 rainfall gauging stations located in Karkheh River Basin (KRB), Iran, in monthly, seasonal, and annual time scales during the last 38 years from 1974 to 2011. This study has been conducted using two versions of Mann–Kendall tests, including (i) Mann–Kendall test by considering all the significant autocorrelation structure (MK3) and (ii) Mann–Kendall test by considering LTP and Hurst coefficient (MK4). The results indicate that the KRB streamflow trend (using both test versions) has decreased in all three time scales. There is a significant decreasing trend in 78 and 73 % of the monthly cases using the MK3 and MK4 tests, respectively, while these percentages changed to 80 and 70 % on seasonal and annual time scales, respectively. Investigation of the trend line slope using Theil–Sen’s estimator showed a negative trend in all three time scales. The use of MK4 test instead of the MK3 test has caused a decrease in the significance level of Mann–Kendall Z -statistic values. The results of the precipitation trends indicate both increasing and decreasing trends. Also, the correlation between the area average streamflow and precipitation shows a strong correlation in annual time scale in the KRB.

This study examines and compares the performance of four new attractive artificial intelligence techniques including artificial neural network (ANN), hybrid wavelet-artificial neural network (WANN), Genetic expression programming (GEP), and hybrid wavelet-genetic expression programming (WGEP) for daily mean streamflow prediction of perennial and non-perennial rivers located in semi-arid region of Zagros mountains in Iran. For this purpose, data of daily mean streamflow of the Behesht-Abad (perennial) and Joneghan (non-perennial) rivers as well as precipitation information of 17 meteorological stations for the period 1999–2008 were used. Coefficient of determination (R 2 ) and root mean square error (RMSE) were used for evaluating the applicability of developed models. This study showed that although the GEP model was the most accurate in predicting peak flows, but in overall among the four mentioned models in both perennial and non-perennial rivers, WANN had the best performance. Among input patterns, flow based and coupled precipitation-flow based patterns with negligible difference to each other were determined to be the best patterns. Also this study confirmed that combining wavelet method with ANN and GEP and developing WANN and WGEP methods results in improving the performance of ANN and GEP models.

Flood is a sudden event with the possibility of life and financial risks, and recently innovative technologies can help to increase the accuracy of its warning. In this research, which was conducted in the Behesht-Abad watershed located in Chaharmahal and Bakhtiari province in Iran, the integration of the Internet of Things, the hybrid of wavelet neural network (WANN) and the HEC-RAS 2D hydraulic models have been used for developing a flood warning system. The ten-minute streamflow data of mentioned river at three hydrometric stations as well as simultaneous information of precipitation and temperature of two meteorological stations were used. The target interval of river was divided into two parts, (i) Upstream and (ii) Downstream (floodplain) intervals. The floods at the upstream and downstream intervals were modeled using the WANN and HEC-RAS 2D models, respectively. The predicted flood discharge using WANN model at the end of upstream interval produces the main input of HEC-RAS 2D model for flood zoning at the downstream interval. The performance of WANN model for predicting discharges entering the floodplain was very well based on R 2 and RMSE criteria equal to 0.9996 and 0.6217 for the training period and 0.9992 and 0.2890 for the validation periods, respectively. The results show that this warning system can effectively estimate the flood discharge in short-term intervals with temporal prediction accuracy of about a minute and a spatial prediction based on cell size of 0.2 m and send it to user’s mobile phone through the Internet.