COD Performance Research Articles

A Comparative Analysis of the 2021 NFL Combine Data: The Relationship Between Linear Sprint, Momentum, Vertical and Horizontal Jumps and Change of Direction Deficit

The majority of COD execution assessments employ the use of total time as the metric by which COD performance is judged. This study investigated the relationships between CODD time, sprint time, 5-10-5 and jump performance. Performance data of 328 participants of the 2021 NFL Combine (age: 22.35 ± 1.00 years; height: 1.87 ± 0.07m; weight: 108.51 ± 21.61kg) was collected and used for the analysis. CODD correlated to the 5- 10-5 pro-agility (r= 0.69 - 0.71) test but not sprint time (r= 0.15 - 0.27) for both the drafted and undrafted groups. Meanwhile, there was a large to very large association between 5-10-5 proagility time and the sprint variables (r = 0.62 - 0.82) for both drafted and undrafted groups. The correlation between CODD time and momentum was minor (r= 0.26 – 0.28) for both drafted and undrafted groups, but the 5-10-5 pro-agility reported a strong to a very strong association with momentum (r= 0.57 – 0.75). There was an inversely small correlation between CODD time and VJh (r= – 0.27) and BJ (r= -0.25– -0.28) for both drafted and undrafted groups whereas the 5-10-5 pro-agility time reported an inversely large to very large correlation with VJH (r= -0.51 – -0.68) and BJ (r= -0.57 – -0.71) on both groups. The magnitude and impact of the momentum, horizontal jump, and vertical jump of participants on their CODD time indicate that coaches and fitness experts should focus on improving the technical aspects of the COD execution when attempting to improve their CODS.

Association between Lower Body Qualities and Change-of-Direction Performance: A Meta-Analysis.

The aim of the present study is to determine the associations between lower-extremity muscle strength qualities and change of direction (CoD) performance. Three databases were used to perform a systematic literature search, and up to September 30 2022. From the studies that met the inclusion criteria, the Pearson's r correlation coefficient to examine relationships muscle strength qualities and COD performance was extracted. The quality of included studies was evaluated by the modified version of the Downs and Black Quality Index tool. Heterogeneity was testified via the Q statistic and I2, and Egger's test was used to assess small study bias. The results revealed that lower-extremity maximal strength (pooled: r=-0.54, dynamic: r=-0.60, static: r=-0.41), joint strength (pooled: r=-0.59, EXT-ecc: r=-0.63, FLEX-ecc: r=-0.59), reactive strength (r=-0.42) and power (pooled: r=-0.45, jump height: r=-0.41, jump distance: r=-0.60, peak power: r=-0.41) were negatively and moderately related to CoD performance. To conclude, the results highlight that a number of muscle strength qualities are associated with CoD performance, that are pertinent to specific phases of a directional change. It should be noted that the conclusions of this study do not establish causality and further research is needed to better understand their training effects and underlying mechanisms.

Effects of physical training on change of direction performance: A systematic review with meta-analysis

Background One of the most sought-after skills for performance in team sports is change of direction. Training the physical qualities of strength, speed, and power has been used to improve change of direction. These qualities of change of direction have been studied extensively for the last 20 years, and their influence is still questioned. Additionally, it is currently unknown how moderating training variables affect COD performance. Objective This study examines the impact of strength, power, and speed training on change of direction performance. Method Following the PRISMA guidelines, a meta-analysis was conducted. Electronic databases were searched for studies conducted from 1991 to April 2021. All studies identified for inclusion were peer-reviewed and published in English and Spanish and used an athlete population as participants. For all analyses, a significance level is set at p < 0.05. Results Sixty-six articles were included in this meta-analysis. Two hundred fifty-one effect sizes were calculated, representing 2056 participants aged between 12 and 25 years. The global effect size (ES) for each quality is reported and Cochran's Q test: Strength ( N = 48) ES: 0.844 Q = 77.63 (95%CI: 0.65;1.07); Speed (N = 17) ES: 0.70 Q = 5.69 (CI95% = 0.35;1.05); Power (N = 49) ES: 0.85 Q = 47.58 (CI95% = 0.64;1.06); Agility ( N = 57) ES: 1.05 Q = 79.63 (CI95% = 0.86;1.24); Combined training ( N = 13) ES: 0.51 Q = 13.79 (CI95% = 0.14;0.93), and the Control Group ( N = 67) ES: 0.53 Q = 47.40 (IC95% = −0.12;0.23), all ES were statistically significant except control group. The ANOVA-LIKE presented a statistically significant difference between physical qualities and the control group (Sig = 0.000 Q = 69.18). Conclusion The training of strength, speed, power, and agility, are effective training methods for improving change of direction ability. Each of these qualities has one or more moderating variables that influencing its development.

Comparison on biological nutrient removal and microbial community between full-scale anaerobic/anoxic/aerobic process and its upgrading processes

A comparative study was conducted for the anaerobic/anoxic/aerobic (AAO) process and its two upgrading processes, five-stage Bardenpho and AAO coupling moving bed bioreactors (AAO + MBBR), using long-term operation data of six full-scale wastewater treatment plants. The three processes all had good COD and phosphorus removal performance. The reinforcing effects of carriers on nitrification were moderate at full-scale applications, while the Bardenpho was advantageous in nitrogen removal. The AAO + MBBR and Bardenpho processes both had higher microbial richness and diversity than the AAO. The AAO + MBBR favored bacteria to degrade complex organics (Ottowia and Mycobacterium) and to form biofilms (Novosphingobium), and preferentially enriched denitrifying phosphorus-accumulating bacteria (DPB) (norank_o__Run-SP154) with the highest anoxic to aerobic phosphorus uptake rates of 65.3 % − 83.9 %. The Bardenpho enriched bacteria tolerant to varied environments (Norank_f__Blastocatellaceae, norank_o__Saccharimonadales, and norank_o__SBR103), and was more suitable for the upgrading of the AAO because of its excellent pollutant removal performance and flexible operation mode.

Relationship Among the Change of Direction Ability, Sprinting, Jumping Performance, Aerobic Power and Anaerobic Speed Reserve: A Cross-Sectional Study in Elite 3x3 Basketball Players.

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 (VmaxIFT), 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 (VmaxIFT), and anaerobic speed reserve (ASR) were also considered. Anaerobic Speed Reserve (ASR) was calculated as the difference between MSS and VmaxIFT. 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 (VmaxIFT), 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 VmaxIFT, 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.

Adsorption and in-situ photocatalytic Fenton multifield coupled degradation of organic pollutants and coking wastewater via Fe[sbnd]BiOBr modification of three-dimensional graphene aerogel

Both adsorption and advanced oxidation processes can achieve rapid removal of organic pollutants. Based on this, FeBiOBr was modified on the surface of three-dimensional graphene aerogel (3D rGA) to construct FeBiOBr/rGA composites. Using the surface adsorption properties of graphene to quickly adsorb pollutants, combined with photocatalytic Fenton degradation by FeBiOBr catalysts, the adsorption and in-situ photocatalytic Fenton multifield coupled degradation system was constructed by the consistency of adsorption and catalytic degradation sites. Experimental results showed that FeBiOBr/rGA has a 2.92-fold increase in the adsorption capacity for phenol compared with bulk rGA. Meanwhile, the degradation rate constant was 2.7 times higher than that of FeBiOBr because of the excellent electrical conductivity of graphene. In addition, it also exhibited excellent COD and TOC removal performance for different phenolic and coking wastewaters. The effects of graphene content, catalyst dosage, H2O2 concentration and other factors on the adsorption-catalytic degradation activity of the synergistic system were further investigated. Based on the influence of active species, the mechanism of FeBiOBr/rGA composite adsorption and in-situ catalytic degradation multifield coupling removal of pollutants was proposed. In addition, the 3D rGA could effectively solve the problem of difficult recycling of powder catalysts and has significant practical application potential.

The Effects of Inter-Limb Asymmetry on Change of Direction Performance: A Systematic Review

Objectives: This review aimed to clarify the associations between COD performance and asymmetries on horizontal jumping, vertical jumping, and strength. Methods: Three databases, including PubMed, Web of Science, and MEDLINE(EBSCOhost) were used to perform a systematic literature search. The search was up to 13 March 2022 and was limited to the literature in the English language and on the human species. Studies included reported exact measurement tools and correlation coefficients and studies in which participants aged >14 years were included. Moreover, studies that were not peer-reviewed and those that did not report an asymmetry index were excluded, as were studies for which the full text was not available. The modified Downs and Black Quality Index tool was used to evaluate the quality of the studies. Results: The systematic literature identified 1151 studies, but only 12 studies were included in this review. A total of 354 participants, ranging from 15 to 23 years of age, were recruited for these studies. The methodological quality score ranged from 6 to 8, with an average of 7.25. The associations between COD performance and vertical jump height, horizontal jump distance, and lower-limb strength asymmetries were examined in 11, 5, and 2 studies, respectively. Six studies reported that vertical jump height asymmetries scores can significantly reduce COD performance, while significant associations between COD performance and horizontal jump distance asymmetries and strength asymmetries were only observed in one study each. Specifically, four studies explored the relationships between CMJ height asymmetries scores and COD performance, and all reported significant associations between them. The main limitations of this review were that it did not consider the sports in which the participants were involved. Conclusions: This study suggests that drop jump height and eccentric knee strength asymmetries can reduce COD performance. Moreover, low horizontal jump asymmetries may not influence COD performance. Further research needs to determine whether the minimal threshold of horizontal jump asymmetries would not affect COD performance.

Relationship between sprint, jump, dynamic balance with the change of direction on young soccer players' performance

The aim of the present paper was to determine the relationship between linear sprinting and jump performance, dynamic balance and change of direction on young soccer players. Ninety-four healthy young highly trained male soccer players belonging to the same high-performance academy agreed to participate in the study [twenty-seven soccer players U16 (14.8 ± 0.4 years; height: 170.6 ± 5.6 cm; body mass 64.7 ± 8.4 kg)] and [sixty-seven soccer players U19 (16.6 ± 1.3 years; height: 173.7 ± 7.2 cm; body mass 66.7 ± 8.0 kg)]. Participants completed 3 testing sessions, 7 days apart. Data from a CMJ, Crossover Hop Test, 10-m sprint test, 505 COD tests and the 90° COD test were collected. Moderate correlations were found in some of the cases (r values were between 0.2 and 0.5 in all cases, being p < 0.05), indicating that linear sprinting, jumping performance and dynamic balance are influential factors in agility but are not the main limiting factor. The highest correlation was found between the cross-over hop test and the 505 COD test (r = 0.44; p < 0.001). The main evidence from the current study suggested that linear sprinting, jumping performance and dynamics balance are determinants of COD, namely explaining the variations in such a skill. The current study revealed that short-distance sprint and jumping performance significantly explain the variations of COD performance on young soccer players.

Deciphering the concurrence of comammox, partial denitrification and anammox in a single low-oxygen mainstream nitrogen removal reactor

One-stage anammox-based autotrophic nitrogen removal technology has attracted increasing interest to sustainable biological nitrogen removal for future wastewater treatment. However, its application in mainstream municipal wastewater treatment is still challenging due to low nitrogen and high organics of raw wastewater. Herein, a novel Simultaneous Carbon Oxidation, partial Comammox, Denitratation and Anammox (SCOCDA) was firstly developed in a single sequencing batch biofilm reactor operated at a dissolved oxygen concentration of ∼0.5 mg/L for treating synthetic municipal wastewater (50 mg/L NH4+-N and 100–250 mg/L COD). The long-term operation showed that almost complete COD and nitrogen removal performance could be achieved at a carbon/nitrogen ratio (COD/NH4+-N) of 3–5 with the corresponding effluent total nitrogen (TN)＜5 mg/L. Microbial community and amoA-targeting amplicon sequencing analysis further verified that comammox Nitrospira spp., denitrifier Thauera and other aerobic/facultative heterotrophs could work synergistically with anammox bacteria, Candidatus Kuenenia. Moreover, nitrogen metabolic and inorganic carbon fixation pathways through the interaction between comammox and anammox were also revealed with the aid of Kyoto Encyclopedia of Genes and Genomes (KEGG). Lastly, potential application of proposed SCOCDA process was illustrated. This research sheds new light on advanced nitrogen removal towards limit of technology via the synergy of comammox and anammox.

A low-volume Nordic hamstring curl programme improves change of direction ability, despite no architectural, strength or speed adaptations in elite youth soccer players

ABSTRACT Nordic hamstring curls (NHC) are a commonly used injury intervention method in amateur team sports. Seventeen elite male academy soccer players performed an 8-week low volume NHC programme. Pre-post intervention measures of isokinetic eccentric knee flexor (KF) strength, linear speed, COD performance, hamstring muscle thickness, pennation angle and fascicle length were recorded. No significant main effects were observed for measures of isokinetic KF strength (P ≥ 0.19), linear sprint speed (P ≥ 0.47) or hamstring muscle architecture (P ≥ 0.30). However, significance was noted for improved COD performance (P < 0.01; mean difference, −0.06, p = 0.001, 95% CI = 0.03 to 0.09; d = 0.80), exceeding the minimal detectable difference (MDD = 0.05 s). A low-volume NHC intervention may contribute to significant improvements in COD ability, independent of no significant changes in eccentric KF strength, linear sprint speed or muscle architectural properties in elite youth soccer players.

New Perspectives of the Traditional and Modified 5-0-5 Change of Direction Test

ABSTRACT Change of direction (COD) ability is considered essential for successful participation in many field and court sports. Several COD models that currently exist identify technique, leg strength qualities, and straight sprint speed as the key determinants of COD performance. This narrative review discusses the original COD model, focusing on specific leg strength qualities (concentric, eccentric, isometric, and reactive strength) and their relationship with 5-0-5 COD performance. It is clear from the existing literature that each of these leg strength qualities contributes to the performance of the 5-0-5 COD test; however, it is unclear which are most at play during the phases of performing a COD. This review introduces a new COD model and a way to split the modified 5-0-5 COD test into 4 distinct phases (acceleration, deceleration, 180○ turn, and reacceleration). This new perspective and proposed method of testing provides greater diagnostic value to the modified 5-0-5 COD test and allows coaches and practitioners to be more targeted with feedback and programming to improve COD and sporting performance.

On-Court Change of Direction Test: an Effective Approach To Assess COD Performance in Badminton Players.

The aim of this research was to assess the reliability of a specific change of direction test (i.e., “On-Court COD test”) in youth badminton players, evaluate the effect of age on On-Court COD performance, and examine its correlations with linear speed, change of direction speed, and vertical jump tests. Forty-two young badminton players (27 males and 15 females; age: 17.3±1.6 years, body height: 170.3±7.5 cm, body mass: 59.0±9.7 kg) were divided into two age groups (Under 17 years and under 19 years). Tests included: linear sprints (5, 10, and 20-m), bilateral/unilateral countermovement jumps, a hexagon test, traditional and modified 505 change of direction tests; and On-court COD. Results showed an excellent intraclass correlation coefficient score (0.90) and a very low coefficient of variation values (1.6%) for the On-Court COD test. Comparing age groups, under 19 players were significantly faster in linear sprints (i.e., 5, 15 and 20-m; small to moderate effect sizes) and in all change of direction tests (moderate to large effect sizes). Moreover, the On-Court COD test showed moderate to large (r=.513-.779) relationships with both acceleration and COD abilities in under 17 players, and with linear sprints, COD, and jump performances in under 19 players. These data indicate that the On-Court COD test is a useful and reliable means to assess COD performance in youth badminton players and it is associated with acceleration, sprint and jump performance.

Predicting change-of-direction performance in elite young badminton players: A multiple regression analysis on acceleration- and deceleration-related qualities

The aim of this study was to examine the interrelationships between direct (sprint and change-of-direction [COD] velocities) and indirect measures (COD-deficit [CODD], deceleration deficit [DD], and sprint momentum) of speed-related performances in young badminton players. Thirty young male badminton players (age: 16.8 ± 1.4 years; body-mass: 61.5 ± 7.9 kg; height: 170 ± 5.8 cm) performed a 20-m sprint followed by 505 COD tests, on the same day. A Pearson product moment test was applied to determine the relationships among variables. A multiple regression analysis was used to verify whether the combination of CODD and DD increased the capacity to predict COD performance. Large and significant relationships were observed between COD and linear sprint velocity and sprint momentum ( r ranging from 0.62 to 0.84; P &lt; 0.05). COD velocity revealed a moderate significant ( r = −0.38) and a small non-significant ( r = 0.29) relationship with CODD and DD, respectively. The multiple regression model combining CODD and DD explained 44% of the variance in COD performance. In summary, young badminton players who sprint faster are equally faster in COD manoeuvres but present higher levels of CODD and DD. Coaches should be aware that faster badminton players may exhibit greater magnitudes of CODD-DD, thus requiring specific interventions to optimize the transition between high deceleration and (re) acceleration phases.

Effect of Dolomite Addition on Fly Ash Based Ceramic Membrane to Reduce COD and BOD of Liquid Waste

Ceramic membrane technology plays an essential role in separation fields such as wastewater treatment. Fly ash as a membrane material has proven to be very effective for many separation processes, including water and air purification, as well as industrial and environmental resource recovery. This study aims to develop a microfiltration ceramic membrane based on fly ash with the addition of dolomite. The synthesized ceramic membranes were then characterized using XRD, SEM, and TGA. Ceramic membranes are used to reduce COD and BOD levels in tofu industrial wastewater. The results showed that the value of membrane porosity tends to increase with the addition of dolomite 0% (D0) to 30% (D30). The increase in the porosity value in the membrane was followed by a decrease in the average pore size, namely 1.6994 m at D0 and 1.1730 m at D30. The membrane with 30% dolomite composition has the best mechanical properties with a compressive strength of 35.29 MPa and superior thermal resistance. This is very beneficial for the use of membranes in the long term. Meanwhile, the membrane filtration ability and the ability of the membrane to reduce COD and BOD levels of waste increased with the addition of dolomite from 0% to 30%. However, the decrease in COD and BOD was smaller in the membrane with 45% dolomite. D30 membrane can reduce COD 80% and BOD up to 71.44%. D30 membrane is the most effective fly ash and dolomite composition in forming pores on the membrane with the best COD and BOD reduction performance.

Traditional and Modified 5-0-5 Change of Direction Test: Normative and Reliability Analysis

ABSTRACT Change of direction (COD) ability is an important performance factor in many field and court sports. A common COD maneuver is the 180-degree turn, which is commonly assessed through the 5-0-5 COD test. Coaches and practitioners need to assess an athlete's COD performance and have access to normative data for these assessments. This review focuses on the traditional and modified 5-0-5 COD test. The 5-0-5 COD performance results have been gathered across 50 different studies and 11 different sports to create sport, sex, and level specific normative data so performance comparisons can be made, which in turn can drive programming to better effect. The reliability of both the traditional and modified 5-0-5 COD tests has been evaluated and discussed. Traditional COD ability of male athletes is better understood given there were 300 male athletes, compared with 62 female athletes. On average, males were 6.03% faster than females. Elite males were 7.78% faster than subelite and novice males, and subelite females were 3.30% faster than novice female athletes. Further research or collation of normative data is needed on female, youth, and elite cohorts to build more comprehensive databases.

Percentage-Based Change of Direction Deficit: A New Approach to Standardize Time- and Velocity-Derived Calculations.

Freitas, TT, Pereira, LA, Alcaraz, PE, Azevedo, PHSM, Bishop, C, and Loturco, I. Percentage-based change of direction deficit: a new approach to standardize time- and velocity-derived calculations. J Strength Cond Res 36(12): 3521-3526, 2022-Change of direction (COD) efforts are crucial in team sports, and an extensive body of research has been devoted to investigating this complex and multifaceted skill. Most studies have assessed players' ability to change direction by reporting completion time or average velocity in different COD tasks. However, it has been argued that these variables may not accurately portray an athlete's true capability to quickly change direction. In this context, new metrics such as the COD Deficit (CODD) have been proposed to provide complementary information on the efficiency to change direction. The current literature presents 2 different CODD computations: time-derived and velocity-derived calculations. Despite both being consistent and representing the same phenomenon, the decision of using one or the other may produce different outcomes, thus influencing coaches' decisions and training strategies. To overcome this issue, we propose a new approach to the computation of the CODD, based on the difference in percentage between linear sprint and COD abilities, in an attempt to standardize the estimation of this variable and simplify the evaluation of COD performance.

The Influence of Sprint Mechanical Properties on Change of Direction in Female Futsal Players.

The aim of the present study was to analyze the association of the sprint force-velocity profile [Hzt FV profile] variables with change of direction [COD] performance in female futsal players. Twelve female futsal players (age: 19.83 ± 4.2 years; body height: 160.75 ± 8.37 cm; body mass: 57.64 ± 8.3 kg) volunteered to be evaluated in the following assessments: Hzt FV profile, 505 test, modified 505 test [M505test] and V-cut test. The Spearman’s correlation coefficient [rs] (p < 0.05) was used to determine the relationship of the mechanical variables of the sprint (maximum power output [Pmax], maximum horizontal force production [F0] and maximum velocity [V0]) with COD performance. V0 showed a very large significant association with the 505 test (rs = -0.767; 90% CI: (-0.92 to -0.43); p < 0.01) and a large association with the V-cut test (rs = -0.641; 90% CI: (-0.86 to -0.21); p < 0.05), whereas Pmax was strongly associated with results of the 505 test (rs = -0.821; 90% CI: (-0.94 to -0.55); p < 0.01) and largely associated with the V-cut test results (rs = -0.596; 90% CI: (-0.84 to -0.14); p < 0.05). In conclusion, maximal power and velocity output during sprinting are determinant factors to successful COD in 180º and 45º cuts, thus, the Hzt FV profile should be assessed in female futsal players to better understand the influence of sprint mechanical properties on COD performance and prescribe individualized training programs

Simultaneous reduction of antibiotics leakage and methane emission from constructed wetland by integrating microbial fuel cell

In this study, a microbial fuel cell coupled with constructed wetland (CW-MFC) was built to demonstrate that integration of MFC can enhance antibiotics (sulfadiazine (SDZ) and ciprofloxacin (CIP)) removal in CWs and control CH4 emissions. Better COD and antibiotics removal performance was obtained in CW-MFC. Notably, both reactors can remove more than 90.00% of CIP. A decline in methane fluxes (by 15.29%) was also observed in CW-MFC compared with CW. The presence of Acorus tatarinowii had no obvious effect on antibiotics removal but the application of manganese ore substrate reduced methane emissions. Further study showed that Proteobacteria was enriched on the Mn substrate anode and the relative abundance of Methanothrix was declined. The results suggested that suppression of methanogenesis may be contributed to a low methane flux in CW-MFC. This study will facilitate the application of CW-MFC to treat antibiotics wastewater and control the ecological risks of greenhouse gas emissions.

Performance changes during the off-season period in football players – Effects of age and previous hamstring injury

ABSTRACT The aims of this study were to investigate changes in selected performance measures during an off-season period, their association, and the potential role of age and previous hamstring injury in semi-professional and amateur football players. Seventy-four male players (age: 25 ± 4 years, stature: 178.0 ± 6.6 cm, body mass: 74.9 ± 8.1 kg) were assessed at the beginning and end of the off-season summer-period for sprint, change-of-direction performance and eccentric hamstring strength. Small to medium increases in sprint times were observed at 5 (d = 0.26, p = 0.057), 10 (d = 0.42, p < 0.001) and 30 m (d = 0.64, p < 0.001). Small (d = −0.23, p = 0.033) improvements were observed for COD performance, and no changes in eccentric hamstring strength (d = 0.10, p = 0.317). The changes in the outcomes were not affected by age (p = 0.449 to 0.928) or previous hamstring injury (p = 0.109 to 0.995). The impaired sprint performance was not related to changes in eccentric hamstring strength (r = −0.21 to 0.03, p = 0.213 to 0.856), instead, changes in COD performance were associated with changes in eccentric hamstring strength (r = −0.42, p = 0.008).

Seasonal Changes in the Physical Performance of Elite Youth Female Soccer Players.

Emmonds, S, Sawczuk, T, Scantlebury, S, Till, K, and Jones, B. Seasonal changes in the physical performance of elite youth female soccer players. J Strength Cond Res 34(9): 2636-2643, 2020-This study investigated the seasonal change in physical performance of 113 (Under 10: U10 [n = 20], U12 [n = 30], U14 [n = 31], and U16 [n = 32]) elite youth female soccer players. Players completed testing pre-, mid-, and post-season, including speed (10- and 30-m sprint), change of direction (CoD; 505 test), power (countermovement jump [CMJ]), strength (isometric midthigh pull), and aerobic capacity (Yo-Yo intermittent recovery test level 1 [YYIRL1]). A general linear model was used to evaluate the change in physical characteristics and the influence of covariates (baseline performance; change in maturity status) on each characteristic across the season. U10's speed and CoD performance decreased from pre-post season, whereas relative strength likely improved. U12's relative strength very likely improved; however, 10-m sprint performance decreased. Relative strength likely decreased, whereas 30-m sprint and CoD time very likely improved in U14's. U16's likely improved relative strength, CMJ, and 10-m sprint, and very likely improved 30-m sprint and CoD from pre-post season. U12-U16's improved YYIRL1 performance pre-post season. Strength and conditioning coaches working with U10-U12 players should look to develop speed, lower-body power, and CoD ability as part of structured strength and conditioning sessions as well as within warm-ups before pitch-based sessions. With U14-U16 players' manipulation of small-sided games combined with short-duration high-intensity running drills may provide an efficient training stimulus to develop the aerobic system while concurrently developing technical/tactical skills. Findings of this study provide a basis for the implementation of strategies to enhance the long-term athletic development of youth female soccer players.