Preparation and Load-Bearing Capacity of Lattice Cell Warren Truss Slot Resin-Stiffener-Reinforced Foam Sandwich Material

This study optimized and proposed a Warren truss slot-hole structure with a double-sided, square shallow slot and vertical and horizontal corrugated symmetry, achieved with inclined holes based on the stability and a good bearing capacity of an inclined strut truss structure. The tetrahedral truss lattice cells were obverse and reverse-staggered in the central core of the structure. Compared with the double-sided, square shallow groove cylindrical straight hole, the resin consumption of the Warren truss slot holes was similar to that of a vacuum-assisted resin infusion; however, the external flat compression force of the Warren truss slot holes on the resin stiffener structure doubled, and its bending contact force increased by approximately 1.5 times. Furthermore, the resulting Warren truss-slotted resin structure exhibited a late failure time. Compared with the double-sided, square shallow groove cylindrical straight hole foam-core sandwich composite, the Warren truss slot resin-stiffener-reinforced sandwich composite exhibited an increase of 4.7 kN in the flat compression load, an improvement of ~40% in flat compressive strength performance, an increase of ~0.58 kN in the bending load, and an improvement of ~60% in the bending strength, demonstrating its better bearing strength performance.

Exercise Biomechanics for Health: Evaluating Lifelong Activities for Well-Being

Biomechanics is a multidisciplinary study of the mechanical laws and principles that govern human movement and the functioning of biological systems [...].

Football movement profile analysis and creatine kinase relationships in youth national team players

Objective

Creatine kinase (CK) is widely used as a monitoring tool to make inferences on fatigue and readiness in elite soccer. Previous studies have examined the relationship between CK and GPS parameters, however these metrics may not accurately describe the players' load during soccer-specific movements. Football Movement Profile (FMP) monitoring is a viable option for such purposes, providing solely inertial sensor-based data and categorizing movements according to intensity (very low, low, medium, high) and movement type (running-linear locomotive, dynamic - change of direction or speed).

Methods

We investigated the relationship between the FMP distribution of youth (U16-U21) national team soccer players and the absolute day-to-day change in CK. We applied Spearman's correlations, principal component analysis and K-means clustering to classify players' CK responses according to their specific FMP.

Results

Moderate to large negative associations were found between very low intensity FMP parameters and CK change (r = -0.43 ± 0.12) while large positive associations were identified between CK change and other FMP metrics (r = 0.62 ± 0.12). Best fitting clustering methods were used to group players depending on their CK sensitivity to FMP values. Principal component analysis explained 83.0% of the variation with a Silhouette score of 0.61 for the 4 clusters.

Conclusions

Our results suggest that soccer players can be clustered based on the relationship between FMP measures and the CK change. These findings can help to plan soccer training or recovery sessions according to the desired load on skeletal muscle, as FMP monitoring might bridge the limitations of GPS telemetry.

Bilateral patellar tendon rupture in a weightlifter during an acute high-loading resistance exercise bout: A case study

Bilateral patellar tendon ruptures are exceedingly uncommon, especially when they occur in individuals without predisposing risk factors or systemic disease. Due to its rarity, many cases are missed on initial presentation resulting in poor patient outcomes. Identifying associated risk factors aids in diagnosis and mitigates this oversight. We report a case of a healthy, recreational weightlifter who sustained bilateral patellar tendon ruptures during an acute high-loading resistance exercise bout. We discuss how a spike in acute workload may have predisposed our patient to this injury. Research into training load and athlete injury risk is currently in vogue, however, no studies have analysed whether poor load management increases the risk of tendon ruptures. This case prompts awareness for clinicians who diagnose and manage this injury and helps to stimulate the formation of educational initiatives for athletes and coaches, aimed at injury prevention.

The load borne by the Achilles tendon during exercise: A systematic review of normative values

The Achilles tendon (AT) can be exposed to considerable stress during athletic activities and is often subject to pathologies such as tendinopathies. When designing a prevention or rehabilitation protocol, mechanical loading is a key factor to consider. This implies being able to accurately determine the load applied to the AT when performing exercises that stress this tendon. A systematic review was performed to synthesize the load borne by the AT during exercises/activities. Three databases (Pubmed, Embase and Cochrane) were searched for articles up to May 2021, and only the studies assessing the AT load in newtons relative to body-weight (BW) on humans during activities or exercises were included. Most of the 11 included studies assessed AT load when running or walking (N = 10), and only three tested exercises were usually performed during rehabilitation. The load on the tendon ranged from 2.7 to 3.95 BW when walking, from 4.15 to 7.71 BW when running, and from 0.41 to 7.3 BW according to the strengthening exercise performed. From the collected data, a progression of exercises progressively loading the Achilles tendon, as well as the possible connections with walking and running activities, could be defined. However, the trends highlighted in the relationship between tendon loading and walking or running speeds present some inconsistencies. Further research is still needed to clarify them, but also to complete the data set in healthy and injured people.

SARS-CoV-2 Serum Viral Load and Prognostic Markers Proposal for COVID-19 Pneumonia in Low-Dose Radiation Therapy Treated Patients

Several studies have shown that the plasma RNA of SARS-CoV-2 seems to be associated with a worse prognosis of COVID-19. In the present study, we investigated plasma RNA in COVID-19 patients treated with low-dose radiotherapy to determine its prognostic value. Data were collected from the IPACOVID prospective clinical trial (NCT04380818). The study included 46 patients with COVID-19 pneumonia treated with a whole-lung dose of 0.5 Gy. Clinical follow-up, as well as laboratory variables, and SARS-CoV-2 serum viral load, were analyzed before LDRT, at 24 h, and one week after treatment. The mean age of the patients was 85 years, and none received any of the SARS-CoV-2 vaccine doses. The mortality ratio during the course of treatment was 33%. RT-qPCR showed amplification in 23 patients. Higher mortality rate was associated with detectable viremia. Additionally, C-reactive protein, lactate dehydrogenase, and aspartate aminotransferase were significant risk factors associated with COVID-19 mortality. Our present findings show that detectable SARS-CoV-2 plasma viremia 24 h before LDRT is significantly associated with increased mortality rates post-treatment, thus downsizing the treatment success.

Study of Chloride Ion Diffusion in Coral Aggregate Seawater Concrete with Different Water-Cement Ratios under Load

This study was conducted to investigate the chloride ion transport in coral aggregate seawater concrete (CASC) with varying water-cement ratios under different loads. The ultimate compressive strength was obtained by conducting compression testing of three groups of CASC with different water-cement ratios. Steady loads of 0%, 10%, and 20% of their respective ultimate compressive strengths were applied to the concrete specimens with different water-cement ratios. After being subjected to a seawater erosion test for 30, 60, 90, 120, and 180 days, the chloride ion concentration at different depths was measured to determine the chloride ion diffusion coefficient. Meanwhile, the chloride ion diffusion coefficients of CASC were verified by comparing them with results obtained from numerical simulations performed using COMSOL software. The test results show that the internal pore space of CASC expands, leading to acceleration of the chloride ion transport rate when applied loads are increased. The initial chloride ion concentration of CASC rises as the water-cement ratio rises, and the concentration gradient formed with artificial seawater lowers, decreasing the chloride ion transport rate. When the water cement ratio decreases and the load increases, the diffusion coefficient increases. Using the numerical simulation method of COMSOL software, it was proved that the model has good applicability and accuracy in predicting chloride ion transport in CASC.

Decomposing Working Memory in Recurrent Major Depression: Impaired Encoding and Limited Maintenance Immune-to-Encoding Constraint

It is generally believed that working memory (WM) is dysfunctional in depression. However, whether this impaired performance originates from impaired encoding, maintenance or both stages is still unclear. Here, we aimed to decompose the abnormal characteristics of encoding and maintenance in patients with recurrent major depressive disorder (MDD). Thirty patients and thirty-nine healthy controls completed a spatial working memory task where the encoding time and the retention time could vary under different load levels. Encoding performance was assessed by comparing accuracies between short and long encoding times, and maintenance performance was assessed by comparing accuracies between short and long retention times. The results show a lower performance in depression than the controls. However, while the decreased accuracy by long retention (vs. short retention) was increased by a short encoding time in the control group, the retention performance of the depression group did not further suffer from the short encoding time. The generally impaired encoding, together with limited maintenance of immunity against the constrained encoding time, suggests a common bias for fixed internal processing over external processing in recurrent MDD. The paradigm provided in this study can be a convenient and efficient clinical test for assessing the WM encoding and maintenance function.

Sensor Location Matters When Estimating Player Workload for Baseball Pitching

Estimating external workload in baseball pitchers is important for training and rehabilitation. Since current methods of estimating workload through pitch counts and rest days have only been marginally successful, clubs are looking for more sophisticated methods to quantify the mechanical loads experienced by pitchers. Among these are the use of wearable systems. While wearables offer a promising solution, there remains a lack of standards or guidelines for how best to employ these devices. As a result, sensor location and workload calculation methods vary from system to system. This can influence workload estimates and blur their interpretation and utility when making decisions about training or returning to sport. The primary purpose of this study was to determine the extent to which sensor location influences workload estimate. A secondary purpose was to compare estimates using different workload calculations. Acceleration data from three sensor locations-trunk, throwing upper arm, and throwing forearm-were collected from ten collegiate pitchers as they threw a series of pitches during a single bullpen session. The effect of sensor location and pitch type was assessed in relation to four different workload estimates. Sensor location significantly influenced workload estimates. Workload estimates calculated from the forearm sensor were significantly different across pitch types. Whole-body workload measured from a trunk-mounted sensor may not adequately reflect the mechanical loads experienced at throwing arm segments. A sensor on the forearm was the most sensitive to differences in workloads across pitch types, regardless of the calculation method.

Comparing the Energy-Stretch Properties of Two Compression Bandage Systems in a Laboratory-Based Test under Controlled Conditions

OBJECTIVE

To compare the characteristics of two commercially available compression systems, a dual-compression bandage system (DCS) and a traditional two-layer bandage (TLB), using a laboratory bench test.

METHODS

The compression systems were evaluated in a computer-controlled tensile test to generate force-deflection curves for each sample. The compressive work and the theoretical pressure applied to the limb by the respective compression bandages were calculated at the maximum stretch and a stretch instructed by the manufacturers. The manufacturer of the DCS provides reference points on how much the bandage should be stretched to provide the desired pressure, and the TLB stretch was calculated from the product’s datasheet.

RESULTS

The combined results of layers 1 and 2 for the DCS showed greater load and work than the TLB at both the maximum and recommended stretch. The recommended stretch for DCS and TLB was less than 50% of the deflection up to the breaking point.

CONCLUSIONS

The high work provided by the two layers of the DCS suggests a wider range of performance than the TLB when applied to the lower limb, especially after the limb volume is initially reduced by compression. Moreover, using the tensile test and the guide of the reference points on layers 1 and 2 from DCS, the calculated pressure achieved the expected values stated by the manufacturer. Human studies should be conducted to determine whether the reference points provided by DCS are beneficial for obtaining repeatable values.

Association of Training and Game Loads to Injury Risk in Junior Male Elite Ice Hockey Players: A Prospective Cohort Study

Background

Training and game loads are potential risk factors of injury in junior elite ice hockey, but the association of training and game loads to injuries is unknown.

Purpose

To investigate the association of chronic training and game loads to injury risk in junior male elite ice hockey players.

Study Design

Cohort study; Level of evidence, 2.

Methods

In this prospective cohort study, we monitored all health problems among 159 male junior ice hockey players (mean age, 16 years; range, 15-19 years) at sports-specific high schools during the 2018-2019 school year. Players reported their health problems every week using the Oslo Sports Trauma Research Center Overuse Questionnaire on Health Problems (OSTRC-H2). The number of training sessions and games was reported for 33 weeks. We calculated the previous 2-week difference in training/game loads as well as the cumulative training/game loads of the previous 2, 3, 4, and 6 weeks and explored potential associations between training/game loads and injury risk using mixed-effects logistic regression.

Results

The players reported 133 acute injuries, 75 overuse injuries, and 162 illnesses in total, and an average of 8.8 (SD ±3.9) training sessions and 0.9 (SD ± 1.1) games per week. We found no association between the difference of the two previous weeks or the previous 2- 3- and 4-week cumulative, training or game load and acute injuries, nor the difference of the two previous weeks, or the previous 4- and 6-week cumulative, training or game load and overuse injuries (OR, ∼1.0; P > .05 in all models).

Conclusion

In the current study of junior elite ice hockey players, there was no evidence of an association between cumulative exposure to training/game loads and injury risk.

Long-Term Performance Evolution of RIOHTrack Pavement Surface Layer Based on DMA Method

Asphalt mixture is a typical viscoelastic material, and its road performance will change with the action of environment and load during actual service. This study conducted experimental research on the surface course asphalt mixture of three categories and six typical structures of RIOHTrack based on the Dynamic Mechanical Analysis method. Moreover, this study explored the performance evolution law of asphalt mixture under the coupling action of load and environment in the process of loading from 0 million to 54 million standard axle times. Results demonstrated that the phase transition characteristic temperature of the surface course materials of the three types of typical structures showed a trend of first increasing and then decreasing with the accumulation of load and environmental effects, indicating the presence of two stages of the dual coupling effect of environmental aging and load rolling on the asphalt mixture during service. In addition, the results suggested that the phase transition characteristic temperature, modulus, and phase angle of the surface layer materials have obvious material differences and structure dependencies.

What are the significant turning demands of match play of an English Premier League soccer team?

This study aimed to compare the significant turning demands of English Premier League soccer match play relative to playing position using LiDAR technology. Turning data were collected from an English Premier League soccer team (2020-2021 season; 18 fixtures) using a Sportlight® LiDAR tracking system. Turns were tracked during match play, sub-categorised by entry speed (<3.0, 3.0-5.5, 5.5-7.0 and >7.0 m/s) and turning angle (Low: 20-59°; Medium: 60-119°; High: 120-180°). Turning metric frequencies were compared between playing positions (centre backs, full-backs, central midfielders, wide midfielders, and central forwards). On average, per match, central midfielders performed more total turns (~38 vs ~18-27), turns with entry speeds <3.0 (~15 vs ~7-10) and 3.0-5.5 m/s (~21 vs ~8-15) and low (~4 vs ~1-2), medium (~10 vs ~3-6) and high angled turns (~24 vs ~12-18) compared to all other playing positions (p ≤ 0.001, d = 0.96-2.74). Approximately, 90% of turns during matches were performed with entry speeds <5.5 m/s and ~63-70% were high angled turns. This study provides unique insights into the turning demands of English Premier League soccer matches , which can be used to inform position-specific physical preparation strategies, turning testing battery selection, agility drill construction, and rehabilitation and return to play standards.

Analysis of Creep Properties and Factors Affecting Wood Plastic Composites

Wood plastic composite (WPC) materials are mainly used as building slabs and load-bearing slabs, which will cause creep deformation, structural failure, and safety problems. Therefore, this work used high-density polyethylene and poplar wood flour as the main raw materials to prepare wood–plastic boards. The bending creep tests of wood–plastic sheets were carried out using an orthogonal test method. According to the creep test results, the influences of the WPC ratio molding temperature, pelleting temperature, coupling agent screw speed, and other technological factors on the creep properties of WPC composites under different loads are analyzed, and the influences of WPC creep properties on structural reliability are also analyzed. The results indicate that the wood–plastic ratio and screw speed are significant factors when the load is at 30% bending strength within the 24h creep test. When the load is at 50% bending strength, the wood–plastic ratio and molding temperature are the significant factors. When the load is at 70% bending strength, the wood–plastic ratio is the most significant factor. When the load is at 50% bending strength within the 240 h creep test, the wood–plastic ratio and molding temperature are significant factors. When the load is at 30% bending strength, the influence of each factor on the creeping variable is provided in the following descending order: wood–plastic ratio, molding temperature, granulation temperature, coupling agent, and screw speed, but none of them are significant factors.

Differences in Force-Velocity Profiles During Countermovement Jump and Flywheel Squats and Associations With a Different Change of Direction Tests in Elite Karatekas

The force-velocity (F-v) relationship has been proposed as a biomechanical characteristic to comprehensively evaluate neuromuscular capabilities within different tasks such as vertical jumping, sprinting and bench pressing. F-v relationship during flywheel (FW) squats was already validated, however, it was never compared to F-v profile of vertical jumps or associated with change of direction (CoD) performance. The aims of our study were (1) to compare F-v profiles measured during counter movement jumps (CMJs) and FW squats, (2) to determine correlations of F-v mechanical capacities with different CoD tests, (3) to investigate the portion of explained variance in CoD tests with the F-v outcome measures. A cross-sectional study was conducted on 39 elite karatekas. They performed CMJs and FW squats using progressive loads to calculate F-v profile outcome variables and different CoD tests (CoD at 90°, CoD at 180°, t-test, short karate specific test (KST) and long KST). Our results showed significantly higher values in all F-v outcome variables (F0-theoretical maximal force, V0-maximal unloaded velocity, Pmax-maximal power output, F-vslope-the slope of F-v relationship) calculated from CMJs compared to FW squats (all p < 0.01). Significant positive moderate correlations between the tasks were found for F0 and Pmax (r = 0.323-0.378, p = 0.018-0.045). In comparison to F-v outcome variables obtained in FW squats, higher correlations were found between F-v outcome variables calculated from CMJs and CoD tests. The only significant correlation in F-v outcome variables calculated from FW squats was found between Pmax and short KST time. For all CoD tests, only one F-v predictor was included; more specifically-CMJ-F0 for CoD 90°, CoD 180° and t-test, and FW-Pmax for short KST performance. To conclude, our results showed that F-v relationship between CMJs and FW squats differed significantly and cannot be used interchangeably for F-v profiling. Moreover, we confirmed that high force and power production is important for the successful performance of general and karate specific CoD tasks.

Load-Bearing Radioulnar Distances to Evaluate an Unstable Distal Radioulnar Joint in Patients With Triangular Fibrocartilage Complex Tears

PURPOSE

Tears of the proximal component of the triangular fibrocartilage complex (pc-TFCC) lead to instability in the distal radioulnar joint. The aim of this study was to measure the load-bearing radioulnar distances (RaUls) and to evaluate its diagnostic suitability in patients with pc-TFCC tears.

METHODS

We retrospectively assessed and compared the lateral wrist radiographs of 61 adult patients with arthroscopically confirmed tears of pc-TFCC with those of a control group of 64 healthy participants. The RaUl was measured on lateral radiographs, and the difference in RaUl (D-value) between load-bearing and nonloading conditions was calculated in the 2 groups. Receiver operator characteristic curves were plotted to determine the diagnostic accuracy and optimal cutoff-score of load-bearing RaUl and RaUl D-value. The diagnostic performance was verified in a validation sample of patients (30 wrists) with pc-TFCC tears and a control group of healthy individuals (30 wrists).

RESULTS

In the training sample, load-bearing RaUls of the affected wrists were higher than the same side of the controls (12.0 mm vs 7.1 mm). The TFCC-injury group showed a significantly higher RaUl D-value than the control group (8.5 mm vs 3.4 mm). Using a receiver operator characteristic curve, the cutoff value of load-bearing RaUl was 10 mm (sensitivity = 97.6%, specificity = 85.7%) and that of RaUl D-value was 6.5 mm (sensitivity = 90.2%, specificity = 78.5%). The areas under the curve of load-bearing RaUl and RaUl D-value were 0.96 and 0.88, respectively. In the test sample, the sensitivity, specificity, and accuracy of RaUl were 0.93, 0.70, and 0.82 and those of RaUl D-value were 0.77, 0.83, and 0.80 respectively.

CONCLUSIONS

Load-bearing RaUl measurement is a simple method to diagnose an unstable distal radioulnar joint in patients with TFCC injury. The load bearing RaUl of >10 mm or RaUl D-value of >6.5 mm can be used to differentiate TFCC injuries and showed acceptable accuracy.

TYPE OF STUDY/LEVEL OF EVIDENCE

Diagnostic II.

In-Season Microcycle Quantification of Professional Women Soccer Players-External, Internal and Wellness Measures

Although data currently exists pertaining to the intensity in the women’s football match, the knowledge about training is still scarce. Therefore, the aim of this study was to quantify external (locomotor activity) and internal (psychophysiological) intensities, as well as the wellness profile of the typical microcycle from professional female soccer players during the 2019/20 in-season. Ten players (24.6 ± 2.3 years) from an elite Portuguese women soccer team participated in this study. All variables were collected in 87 training session and 15 matches for analysis from the 2019−2020 in-season. Global positioning variables such total distance, high-speed running, acceleration, deceleration and player load were recorded as intensity while Rated Perceived Exertion (RPE) and session-RPE were recorded as internal measures. The Hooper Index (HI) was collected as a wellness parameter. The results showed that internal and external intensity measures were greater in matches compared to trainings during the week (match day minus [MD-], MD-5, MD-4, MD-2), p < 0.05 with very large effect size (ES). In the same line, higher internal and external intensity values were found in the beginning of the week while the lowest values were found in MD-2 (p < 0.05, with very large ES). Regarding wellness, there was no significant differences in the HI parameters between the training days and match days (p > 0.05). This study confirmed the highest intensity values during MD and the lowest on the training session before the MD (MD-2). Moreover, higher training intensities were found in the beginning of the training week sessions which were then reduced when the MD came close. Wellness parameters showed no variation when compared to intensity measures. This study confirmed the hypothesis regarding internal and external intensity but not regarding wellness.

In-Season Quantification and Relationship of External and Internal Intensity, Sleep Quality, and Psychological or Physical Stressors of Semi-Professional Soccer Players

The purpose of this study was two-fold: (a) to describe and analyse the relationship of the in-season variations of external and internal intensity metrics as well as well-being measures across different periods of a semi-professional soccer season (early-, mid- and end-season); and (b) to describe training monotony (TM) and training strain (TS) for 20 weeks in a semi-professional soccer season. Eighteen semi-professional players (age: 29 ± 4.1) from the Asian First League team participated in this study. The players were monitored for 20 consecutive weeks during in-season for external training intensity, internal training intensity and well-being parameters. The in-season was organized into three periods: early-season (weeks 1−7); mid-season (weeks 8−13); and end-season (weeks 14−20). Total distance (TD), high-speed running distance (HSRD), sprint distance, rate of perceived exertion (RPE), session-RPE (s-RPE), TM, TS, heart rate average and maximum, as well as sleep quality, stress and muscle soreness were collected. Results revealed that TD, HSRD and sprint distance (total values) were meaningfully greater during end-season than in the early-season. RPE showed a significantly highest value during the end-season (4.27 AU) than in early- (3.68 AU) and mid-season (3.65 AU), p < 0.01. TS showed significant differences between early-season with mid-season (p = 0.011) and end-season (p < 0.01), and the highest value occurred in week 17 during end-season (6656.51 AU), while the lowest value occurred in week 4 during early-season (797.17 AU). The average TD periods showed a moderate to large correlation with RPE, sleep and s-RPE at early-, mid- and end-season. Increasing the training intensity without considering the well-being of the players affects the performance of the team. Examining processes of the relationship between training intensity and other psychological indicators among players will probably be effective in training planning. Sports coaches and fitness professionals should be wary of changes in TM and TS that affect players performance. Therefore, to better control the training, more consideration should be given by the coaches.

Weekly Variations of Well-Being and Interactions with Training and Match Intensities: A Descriptive Case Study in Youth Male Soccer Players

The aim of this study was two-fold: (i) analyze the weekly variations of well-being and training/match intensity measures in youth soccer players, and (ii) test relations between well-being and training intensity outcomes. The study followed a descriptive case study design. Twenty-seven under-17 male soccer players were monitored for well-being and training intensity parameters over seventeen consecutive weeks. An adjusted version of the Hooper questionnaire was used to monitor the perceptive sleep quality, readiness, fatigue, and delayed onset muscle soreness (DOMS) early in the morning. The CR-10 Borg’s scale was also used for monitoring the rate of perceived exertion (RPE) of players after training sessions. Repeated-measures analysis of variance was executed to test the between-week variations of both well-being and training intensity outcomes. Moreover, Pearson product moment correlation was used to test the relations between well-being and training intensity outcomes. Repeated measures ANOVA revealed significant differences between weeks in the sleep quality (F = 0.422; p < 0.001; ηp2 = 0.140), readiness (F = 0.8.734; p < 0.001; ηp2 = 0.251), fatigue (F = 4.484; p < 0.001; ηp2 = 0.147), DOMS (F = 3.775; p = 0.001; ηp2 = 0.127), RPE (F = 7.301; p < 0.001; ηp2 = 0.219), and session-RPE (F = 17.708; p < 0.001; ηp2 = 0.405). Correlations between well-being and training intensity outcomes in the same week revealed moderate correlations between fatigue and session-RPE (r = 0.325). As conclusions, it was found that well-being and training intensity fluctuates over the season, while well-being outcomes seems to be related with training intensity, although with a small magnitude.

On rigid origami III: local rigidity analysis

In this article, rigid origami is examined from the perspective of rigidity theory. First- and second-order rigidity are defined from local differential analysis of the consistency constraint; while the static rigidity and prestress stability are defined after finding the form of internal force and load. We will show the hierarchical relation among these local rigidities with examples representing different levels. The development of theory here follows the same path as the conventional rigidity theory for bar-joint frameworks, but starts with different high-order rotational constraints. We also bring new interpretation to the internal force and geometric error of constraints associated with energy. Examining the different aspects of the rigidity of origami might give a novel perspective for the development of new folding patterns, or for the design of origami structures where some rigidity is required.

A Comparison of the External and Internal Demands Imposed during Conditioning Training and Match-Play in Semi-Professional and Development Female Netball Players

This case series, team-based study aimed to compare the demands imposed during conditioning training and match-play in netball players. Female netball players competing at semi-professional (n = 9, age: 22.2 ± 3.8 years) and development (n = 9, age: 22.3 ± 2.9 years) levels had their internal (rating of perceived exertion (RPE)) and external (relative PlayerLoad (PL) in total and in the forwards, sideways, and vertical vectors) loads measured during conditioning-based training sessions and matches in a season. Demand variables were compared between conditioning and match-play across all players and according to position in each playing level. Conditioning training imposed higher relative PL in total and in each vector compared to match-play in semi-professional and development players (small to large effects). In contrast, RPE was significantly (p = 0.006) higher during match-play than conditioning training in semi-professional and development players (medium effects). Furthermore, according to playing position, significantly higher relative PL variables were evident during conditioning training than match-play in wing attack and goalkeeper semi-professional players and in goal attack, goal shooter, goal keeper, and goal defence development players. These results suggest conditioning training practices elicit adequate external intensities but inadequate internal intensities relative to match-play across positions in semi-professional and development netball players.

Variation in Physical Performance of Futsal Players During Congested Fixtures

PURPOSE

To investigate the match-to-match variation of physical performance during official congested fixtures in elite futsal players.

METHODS

Physical performance was measured by external and internal load metrics in 12 elite male futsal players. Two periods with 3 matches within 4 days were analyzed. The variation in physical performance of the players during matches was analyzed using the latent growth curve modeling that estimated interindividual and intraindividual growth paths.

RESULTS

Playing time had a significant effect on physical performance growth with significant paths of interindividual and intraindividual variability. Players who competed for more time revealed lower initial levels (ie, first match) of total distance covered (β = -0.62), high-speed running (β = -0.18), accelerations (β = -0.31), decelerations (β = -0.44), and session rate of perceived exertion (β = 0.81) than players who competed for less time (P < .05). In addition, players who competed for more time revealed higher increases in total distance covered (β = 0.47), high-speed running (β = 0.16), and session rate of perceived exertion (β = 0.66) and lower increases in accelerations (β = -0.21) and decelerations (β = -0.58) than players who competed for less time from the first to the third match (P < .05).

CONCLUSIONS

Congested fixtures did not affect physical performance in elite futsal players. Playing time showed to be a key performance factor. There was a considerable heterogeneity in the responsiveness to physical performance over congested fixtures, suggesting an analysis of individual variability to evaluate real changes in match performance, training intensity, and workload.

Comparison of player-dependent and independent high-speed running thresholds to model injury risk in football

High-speed running (HSR) loads have been linked with non-contact injury risks in team-sports. This study investigated whether player-specific speed zones, reflecting individual fitness characteristics, impact the associations between non-contact injury and acute and chronic HSR loads. Semi-professional soccer players from two clubs (n = 47) were tracked over two seasons using 10 Hz GPS (5552 observations). HSR distances were calculated arbitrarily (≥5.5 m·s^-1), and in an individualised fashion based on the final speed of the 30-15 intermittent fitness test. Cumulative running loads were represented by exponentially weighted moving averages with 7-(acute) and 28-day (chronic) decay parameters. Physiotherapists collected non-contact, lower-limb, time-loss injury data (n = 101). Injury models using session type (training vs matches), coach, as well as arbitrary or individualised running loads were constructed via mixed-effect logistic regression. Session type had the largest effect on injury (training vs match OR = 0.28; 95%CI:0.17-0.44). Variations in individualised or arbitrary acute and chronic HSR loads within the mid-range of the observed data had negligible effects on predicted injury risk. However, the uncertainty of estimated effects at extreme values of acute and chronic HSR loads prevented any conclusive findings. Therefore, the efficacy of using customised speed thresholds in quantifying load for injury risk mitigation purposes remains unclear.

Is it appropriate to use external loads during side-lying hip abduction exercise for weakened gluteus medius?

BACKGROUND

Side-lying hip abduction exercise could be beneficial to improve the neuromuscular control of the hip abductor; however, there has been limited information available to determine the exercise load during the exercise.

OBJECTIVE

This study aimed to demonstrate the effects of using external loads on the hip abductor muscles during side-lying hip abduction exercises in females with gluteus medius (GM) weakness.

METHODS

This study enrolled 24 females with weakness in the GM. Electromyographic (EMG) data of the quadratus lumborum (QL) and GM muscles were recorded during the exercise under three load conditions: no-load, external load-1 (3% of body weight), and external load-2 (5% of body weight).

RESULTS

During the exercise, the EMG activities of the QL were significantly different under all three conditions (p< 0.05), with greater activity observed in the external load-2 condition (92.05 ± 65.93% maximal voluntary isometric contraction [MVIC]) as compared to the others, and in the external load-1 condition (82.47 ± 57.36% MVIC) as compared to the no-load condition (48.94 ± 45.09% MVIC). Furthermore, the GM/QL ratios showed significant differences between no-load (1.78 ± 1.47) and external load-1 conditions (0.93 ± 0.60), and between no-load and external load-2 (0.85 ± 0.45) conditions (p< 0.05).

CONCLUSION

These findings suggest that greater load could be a factor to increase the QL activity during the exercise in females with weakened GM.

[Fabrication of Supported Titanium Xerogel Adsorbent and Performance Evaluation for Arsenite Removal]

Although the adsorption capacity of titanium xerogel(TAX) for arsenite(As(Ⅲ)) is high(254 mg·g^-1), the adsorption rate is slow. Therefore, TAX was loaded onto activated carbon, sponge, and resin to fabricate a supported adsorbent, and the arsenite removal performance was evaluated. Except sponge, activated carbon and resin could successfully load TAX. The results showed that resin and activated carbon loaded TAX improved the As(Ⅲ) removal performance, and more significantly by the resin-based materials. Through wet digestion and adsorption kinetics experiments, the amount of titanium loaded was approximately 1.4% and 5% in the activated carbon-based(TAX@AC) and resin-based(TAX@resin) materials, respectively. For the initial concentration of 1.0 mg·L^-1 As(Ⅲ) solution, the adsorption rate constant of TAX@D201 was 0.85 mg·(g·min) ^-1, which was 21 times higher than that of unloaded TAX[0.04 mg·(g·min) ^-1]. Columns packed with TAX@resin could effectively lower arsenite concentration for up to 560 bed volumes, which is 2.8 times greater than that of the iron-based composites with the same metal mass. Therefore, loading TAX on macroporous resin is an effective strategy and provides an effective approach for the application of TAX in arsenite-containing groundwater.