Comparing three generic musculoskeletal models to estimate the tibiofemoral reaction forces during gait and sit-to-stand tasks

The choice of musculoskeletal (MSK) model is crucial for performing MSK estimations to evaluate muscle demands and joint forces. This study compared two previously published generic MSK models and a modified model to estimate tibiofemoral reaction forces (TFRF) during gait, sit-to-stand, and stand-to-sit. The estimated tibiofemoral reaction forces were compared with an in vivo dataset from six patients using an instrumented knee prosthesis. A correlation and root mean square error (RMSE) in the time-series analysis and relative peak error (RPE) were evaluated. The results showed that the three MSK models were similar in estimating the vertical forces, with a large correlation, and RPE was found around 20 % during gait. The RMSE and the RPE indicated that the modified model had lower total and lateral compartment forces errors for sit-to-stand and stand-to-sit, showing the best performance. The shear forces for all tasks and models showed significant errors. Future MSK studies should consider these findings when researching functional tasks. The modified model was found to be more effective in estimating the vertical tibiofemoral joint reaction forces in tasks that impose greater demands on muscle forces and require high knee and hip flexion.

Relationship Between Body Size and Skeletal Age with Muscle Damage in Young Soccer Players

This study verified the relationship between body size and skeletal age (SA) with the behavior of blood markers of muscle damage and delayed onset muscle soreness (DOMS) after a soccer match in the U-13 and U-15 categories. The sample consisted of 28 soccer players in the U-13 and 16 in the U-15 categories. Creatine kinase (CK), lactate dehydrogenase (LDH), and DOMS were evaluated up to 72 h after the match. Muscle damage was elevated at 0 h in U-13, and from 0 h to 24 h in U-15. DOMS increased from 0 h to 72 h in U-13 and from 0 h to 48 h in U-15. Significant associations of SA and fat-free mass (FFM) with muscle damage markers and DOMS were observed only in U-13, specifically at time 0 h, when SA explained 56% of CK and 48% of DOMS and FFM explained 48% of DOMS. We concluded that in the U-13 category, higher SA is significantly associated with muscle damage markers, and increase in FFM is associated with muscle damage markers and DOMS. Furthermore, U-13 players need 24 h to recover pre-match muscle damage markers and more than 72 h to recover DOMS. In contrast, the U-15 category needs 48 h to recover muscle damage markers and 72 h to recover DOMS.

Using Social Network Analysis to Study Relationships Between Young Soccer Players' Bone Age, Body Size, and the Centrality of Their Pass Interactions

Prior research has suggested relevance to anthropometric variance of youth athletes at various stages of their maturation, and prior studies of youth players' soccer skills have failed to consider their interdependent interactions during play. Accordingly, to address both of these separate research omissions, we aimed in this study to analyze the relationships between young (U-13 and U-15 groups) soccer players' bone age and body size indicators and centrality measures of their pass interactions during small sided games. We included young 81 athletes (M age = 14.4, SD = 1.1 years) from whom we took anthropometric measurements of body mass, height, and trunk-cephalic height and obtained their bone age using the Tanner-Whitehouse 3 classification method. We also filmed small-sided games in the goal keeper/three player (GK3-3GK) format to analyze the centrality of their passing actions on the following measures: degree of centrality, closeness of centrality, degree of prestige, and proximity of prestige. There were no group differences in the prominence of passing actions across these three measures (t_mean = -3.13; p > .05). Canonical correlations of these relationships were significant only in the U-13 group, in which centrality in passing actions was related to body size (r = 0.71; R² = 0.21; ʌ = 0.28; p = .03). U-13 players who were physically larger and who presented higher bone age showed centralized main passing actions.

Non-radiographic validity and reliability measures for assessing foot types: A systematic review

BACKGROUND

Foot type classification is well recognized in clinical practice and orthopedic literature, a universally accepted classification or standardized measures to determine foot types are lacking. The objective of this study was to identify which non-radiographic assessment methods are considered valid and/or reliable for the classification of foot types.

METHOD

A systematic database search was performed. Only cross-sectional studies that performed reliability and/or validity analysis of non-radiographic methods were included. To evaluate the risk of bias, the Critical Appraisal Tool (CAT) was used to evaluate the measurement properties of objective clinical methods.

RESULTS

Twenty-six studies were included. The results of reliability and validity, in general, demonstrated high scores, but, inconsistencies were related to the variability of the measurements, heterogeneity of the methods used to determine reliability and validity, and lack of parameters for classifying foot types, which resulted in few elements to determine which method of foot type evaluation is valid and reliable.

CONCLUSION

Given the Intraclass Correlation Coefficient and CAT results and the presence of normative values, the static measurements of the "Arch Height Index", "Foot Posture Index", and "Staheli Arch Index" can be suggested to classify foot types.

Influence of the medial longitudinal arch of the foot in adult women in ankle isokinetic performance: a cross-sectional study

BACKGROUND

Maintenance of the medial longitudinal arch (MLA) of the foot is fundamental during functional tasks and disorders can lead to clinical alterations. Studies have demonstrated that deficits in ankle isokinetic performance can predispose an individual to lower limb injuries.

OBJECTIVES

To evaluate the muscular performance of cavus, planus, and normal feet by means of torque/body mass and the isokinetic phases, to generate 3D surface map analysis, and to verify whether there is a relationship between MLA height and arch height flexibility with isokinetic performance.

METHODS

The sample consisted of 105 healthy adult women, divided into three groups: normal, cavus, and planus. Assessment in concentric mode at 30, 60, and 90 °/s in the dorsiflexion and plantarflexion of the ankle joint were analyzed during the three isokinetic phases (acceleration, sustained velocity, and deceleration). The variables total range of motion, peak of torque (PT), and angle of PT were extracted within the sustained velocity.

RESULTS

In dorsiflexion at 60 °/s, the phase where the velocicty is sustained (load range phase) was higher in the planus group (M_eanD_ifference=10.9 %; ω²_p = 0.06) when compared with the cavus group. Deficits in the peak torque/body mass in dorsiflexion at 60 °/s (cavus feet: MD=-3 N.m/kg; ω²_p = 0.06; and planus feet: MD=-1.1 N.m/kg; ω²_p = 0.06) were also observed as well as in the 3D surface maps, when compared with the normal group. The flexibility of MLA had a negative correlation of PT at 30 °/s in cavus group. The heigth of MLA had a postive correlation with the PT for the cavus and planus group ate 60 °/s. All other results did not show differences between the groups.

CONCLUSIONS

The planus groups showed a better capacity of attain and sustained the velocity in dorsiflexion in relation the cavus group. The cavus and planus group had deficts in torque in relation the normal. The correlations were weak between the measures of MLA and PT. Thereby, in general the differences between foot types showed small effect in isokinetic muscle performance measures of the plantar and dorsi flexores.

TRIAL REGISTRATION

Study design was approved by the IRB (#90238618.8.0000.5231).

Simple and reliable protocol for identifying talented junior players in team sports using small-sided games

We designed and tested a protocol for measuring the performance of individuals in small-sided soccer games. We tested our protocol on three different groups of youth players from elite Brazilian football academies. Players in each group played a series of 3v3 games, in which individuals were randomly assigned into new teams and against new opponents for each game. We calculated each individual's average individual goals scored, goals scored by teammates, goals conceded, and net team goals per game. Our protocol was consistent across days and repeatable across groups, with intraclass correlation coefficients (ICCs) of 0.57-0.69 for average net goals per game across testing days. Players could achieve high success by scoring goals or ensuring their team concede few goals. We also calculated the first and second dimension of a principal component analysis based on each player's number of goals scored, goals scored by teammates, and number of goals conceded per game. Players that were overall high performers had higher PC₁ scores, while PC₂ scores represented the type of contribution made by a player to overall performance. Positive PC₂ values were indicative of high number of individual goals while negative values were associated with more goals from teammates and fewer conceded goals. Our design allows coaches and scouts to easily collect a robust metric of individual performance using randomly designed, small-sided games. We also provide simulations that allow one to apply our methodology for individual talent identification to other small-sided games in any team sport.

Test-retest reliability of multiscale fractal dimension measurements of plantar pressure maps during dynamic tasks

The tools used to evaluate foot types are divergent since they adopt classic linear analyzes, based on anthropometric or image measurements, which do not dynamically contemplate the variability of foot shape. The use of newer techniques such as multiscale fractal dimension (MFD) may be a key to this type of problem. However, for these measures to be used safely and consistently, it is essential to evaluate their reliability. The aim of this study was to evaluate the test-retest reliability of MFD measurements of adult plantar pressure maps during gait, as well as the standard error of measurement (SEM), and minimal detectable change (MDC₉₀). Seventy-two subjects were included in the test-retest, with a one week interval. The plantar pressure maps were constructed using a pressure platform. The data were processed in a routine for extracting the MFD curve measurements (maximum and integral values). The Intraclass Correlation Coefficient results (ICC_3,k) were excellent for both measurements (maximum value 0.96, 95% confidence interval [0.93-0.97], and integral 0.95 [0.92-0.97]) with low SEM and MDC₉₀ values below 10% of the mean. The application of MFD to the plantar pressure data generated by the pressure platform is reliable and could allow exploration of the complexity of foot shapes, enabling their classification.

Unlocking the potential of big data to support tactical performance analysis in professional soccer: A systematic review

In professional soccer, increasing amounts of data are collected that harness great potential when it comes to analysing tactical behaviour. Unlocking this potential is difficult as big data challenges the data management and analytics methods commonly employed in sports. By joining forces with computer science, solutions to these challenges could be achieved, helping sports science to find new insights, as is happening in other scientific domains. We aim to bring multiple domains together in the context of analysing tactical behaviour in soccer using position tracking data. A systematic literature search for studies employing position tracking data to study tactical behaviour in soccer was conducted in seven electronic databases, resulting in 2338 identified studies and finally the inclusion of 73 papers. Each domain clearly contributes to the analysis of tactical behaviour, albeit in - sometimes radically - different ways. Accordingly, we present a multidisciplinary framework where each domain's contributions to feature construction, modelling and interpretation can be situated. We discuss a set of key challenges concerning the data analytics process, specifically feature construction, spatial and temporal aggregation. Moreover, we discuss how these challenges could be resolved through multidisciplinary collaboration, which is pivotal in unlocking the potential of position tracking data in sports analytics.

Team Dynamics, Running, and Skill-Related Performances of Brazilian U11 to Professional Soccer Players During Official Matches

Palucci Vieira, LH, Aquino, R, Moura, FA, Barros, RMLd, Arpini, VM, Oliveira, LdP, Bedo, BLdS, and Pereira Santiago, PR. Team dynamics, running, and skill-related performances of Brazilian U11 to professional soccer players during official matches. J Strength Cond Res 33(8): 2202-2216, 2019-Analyses of movements during soccer competition have been used previously to help develop conditioning programs. However, this has not been extensively studied in youth populations. Therefore, the purposes of this study were to examine (1) dynamics of collective tactical movements, (2) running, and (3) skill-related performances during soccer matches disputed by children to senior players. A total of 120 Brazilian players in the age groups U11, U13, U15, U17, U20, and professional (PRO) were monitored during official competition matches (N = 12). Using semiautomatic video-based tracking (30 Hz), match running variables including total distance traveled, average speed, maximum sprint speed, and high-intensity activities were evaluated. Tactical metrics were computed as team surface area, spread, and median frequency. Through notational analysis, technical skills such as involvements with the ball, passes, ball touches, duels, and goal attempts were also recorded. One-way analysis of variance and magnitude-based inferences were used to detect differences between ages. Although the average speed, team surface area, and spread tended to present stabilized increases from the U15 (e.g., U15 > U13 > U11), maximal sprinting speed (PRO > U17 > U15, U13, U11) and percentage at very high-intensity activities (U20 > PRO, U17 > U15 > U13 > U11) demonstrated continuous gains. Median frequencies were higher in the younger groups (U13, U15, U17 > U20, PRO), although the percentage of successful passes was higher in the older groups (PRO > U17, U15 > U13, U11). We concluded that Brazilian U11 to PRO players present different performance profiles for running, collective movement dynamics, and technical skills, and that the rate of development regarding these components varies. Coaches should be aware of these differences to select and adapt training content for each age group.

P4626Neuronal nitric oxide sintetase polymorphism increases sympathetic activity and recurrent cardiovascular events after myocardial infarction

Background

The expression and activity of neuronal nitric oxide sintetase (nNOS) in central and peripheral nervous system attenuate the sympathetic response and promote other cardioprotective effects in animal models. However, in humans those effects are uncertain. Recently, a polymorphism at the sequence rs41279104 G/T has been associated with a reduced expression of nNOS, but its clinical impact has never been studied in the context of ST elevation myocardial infarction (STEMI) in humans.

Purpose

We investigated the impact of the T allele at rs41279104 in sympathetic activation after STEMI and its influence in the incidence of recurrent major cardiovascular events (MACE). We sought to determine a pathway to autonomic nervous system modulation during STEMI and its possible clinical impact.

Methods

297 patients were admitted in the first 24h (D1) after STEMI and followed prospectively. Blood samples and an electrocardiogram were obtained upon D1 and fifth day (D5). We assessed glycosylated hemoglobin, glucose, insulin, C-peptide, lipid profile and nitric oxide (NOx) plasma levels. We genotyped rs41279104 and grouped patients according to carrier status (GT+TT vs. GG). The heart rate variability was obtained with a 15min electrocardiogram recording and processed into spectral analysis variables including low (LF) and high frequencies (HF) and LF/HF ratio. Flow-mediated dilation (FMD) was performed after 30 days. Clinical follow–up was carried over until two years after MI and the endpoint was a composite of major cardiovascular events (MACE) consisting of fatal MI, non-fatal MI, unstable angina with hospitalization and cardiac sudden death.

Results

T-allele carriers showed a decreased parasympathetic activity and an increased sympathetic activity between D1 and D5 (ΔLF −68.43 (median) [IQR −324.76 to −6.29] vs −4.49 [−190.29 to 72.03], p<0.001; ΔHF −19.40 [−185.55 to 6.21] vs −10.73 [−79.53 to 137.53], p=0.004; ΔLF/HF 0.07 [−2.32 to 1.44] vs −0.11 [−1.14 to 0.96], p<0.001). Decreased FMD (6.9±4.7 vs 7.5±4.9, p=0.046) was also detected among T-allele carriers. In the Cox -regression analysis adjusted by sex, age, betablocker use and mean simvastatin dose, T-allele carriers had a relative risk for MACE of 2.112 (95% CI: 1.133–3.938; p=0.019).

Conclusions

The presence of the T allele at nNOS gene rs41279104 sequence is associated with increased sympathetic tone at acute phase of STEMI and a higher incidence of recurrent MACE.

Velocity-specific knee strength between professional and under-17 female volleyball players

Background

Many studies have investigated isokinetic performance in volleyball players but not through surface maps.

Objectives

The goals of this study were to assess velocity-specific isokinetic knee extensor–flexor muscle strength and to compare the isokinetic knee extensor–flexor muscles between professional (PRO) and under-17 (U17) female volleyball players.

Method

This cross-sectional laboratory study was developed with two groups: PRO (n = 12), median_age = 21.3 years, and U17 (n = 9), median_age = 15 years. Peak torque, total work, mean power, angle of peak torque, hamstring–quadriceps torque ratio (H–Q ratio) and torque–angle–velocity surface maps were analysed from knee extension–flexion at 60, 120 and 300 degrees per second (°/s).

Results

Significant differences were identified for extensor peak torque between PRO x = 202.3 Newton metre (N·m) (standard deviation [SD] = 24.4) and U17 x = 141.6 N·m (30.1) at 60 °/s (p < 0.001; d = 2.21) as well as flexor peak torque (PRO x = 75.7 N·m [10.3] and U17 x = 57.7 N·m [11.4]) at 120 °/s (p < 0.001; d = 1.65) for the dominant limb. There were also significant group differences for total work and mean power at all velocities for extension and flexion. Surface maps demonstrated higher torque at lower speeds for both groups with smaller torque changes across velocities for flexion.

Conclusion

Different groups of female volleyball players showed contrasting concentric knee muscle strength across isokinetic velocities.

Clinical implications

These results demonstrate the importance of specific strength training for different age groups, even within the same sport, and provide insight into muscle strength.

Oral antioxidant therapy for prevention and treatment of preeclampsia: Meta-analysis of randomized controlled trials

AIMS

To determine whether oral antioxidant therapies, of various types and doses, are able to prevent or treat women with preeclampsia.

DATA SYNTHESIS

The following databases were searched: MEDLINE, CENTRAL, LILACS, and Web of Science. Inclusion criteria were: a) randomized clinical trials; b) oral antioxidant supplementation; c) study in pregnant women; d) control group, treated or not with placebo. Papers were excluded if they evaluated antioxidant nutrient supplementation associated with other non-antioxidant therapies. Data were extracted and the risk of bias of each study was assessed. Heterogeneity was analyzed using the Cochran Q test, and I2 statistics and pre-specified sensitivity analyses were performed. Meta-analyses were conducted on prevention and treatment studies, separately. The primary outcome was the incidence of preeclampsia in prevention trials, and of perinatal death in treatment trials. Twenty-nine studies were included in the analysis, 19 for prevention and 10 for treatment. The antioxidants used in these studies were vitamins C and E, selenium, l-arginine, allicin, lycopene and coenzyme Q10, none of which showed beneficial effects on the prevention of preeclampsia (RR: 0.89, CI 95%: [0.79-1.02], P = 0.09; I² = 39%, P = 0.04) and other outcomes. The antioxidants used in the treatment studies were vitamins C and E, N-acetylcysteine, l-arginine, and resveratrol. A beneficial effect was found in intrauterine growth restriction.

CONCLUSIONS

Antioxidant therapy had no effects in the prevention of preeclampsia but did show beneficial effects in intrauterine growth restriction, when used in the treatment of this condition.

ISOKINETIC MUSCLE PERFORMANCE AFTER ANTERIOR CRUCIATE LIGAMENT RECONSTRUCTION: A CASE-CONTROL STUDY

BACKGROUND

and Purpose: Knee muscle strength deficits have been reported in individuals who have undergone anterior cruciate ligament reconstruction (ACLR). Isokinetic testing is a valid way to assess muscle strength. Some isokinetic variables, including the range of motion in the phases to attain a specific velocity, load range (sustained specific velocity), time to achieve deceleration, and qualitative analysis of the torque-angle velocity relationship, may contribute to understanding recovery of these individuals after surgery. Thus, the purpose of this study was to compare the load range (LR), time to attain velocity (TTAV), deceleration time (DT) phases, total range of motion (ROM), peak torque/body mass (PT/BM), angle of peak torque (AngPT) during LR and torque-angle-velocity relationships (TAV_3D) between post ACLR and matched control subjects.Study design: Case-control.

METHODS

Seven men who underwent ACLR and seven matched controls were evaluated from four to six months after surgery. Testing was performed on a Biodex System 4 isokinetic dynamometer in concentric mode at 60, 120 and 300 °/s, for knee flexion and extension.

RESULTS

Statistically significant differences were seen for extension ROM at 60 °/s where ROM was greater in the control group. PT/BM for extensors was also significantly greater in controls by 20 % compared to ACLR at 60 and 120 °/s. PT/BM for flexors was significantly greater for controls at 60 °/s (∼15 %). TAV_3D showed differences in torque and, specifically, the control group sustained knee flexion torque for a greater range of motion when compared to the ACLR group.

CONCLUSION

The ACL group presented with lower ROM and PT/BM, therefore exhibiting worse muscle performance in comparison to the control group.Level of Evidence: 3.

Repeated-Sprint Sequences During Female Soccer Matches Using Fixed and Individual Speed Thresholds

Nakamura, FY, Pereira, LA, Loturco, I, Rosseti, M, Moura, FA, and Bradley, PS. Repeated-sprint sequences during female soccer matches using fixed and individual speed thresholds. J Strength Cond Res 31(7): 1802-1810, 2017-The main objective of this study was to characterize the occurrence of single sprint and repeated-sprint sequences (RSS) during elite female soccer matches, using fixed (20 km·h) and individually based speed thresholds (>90% of the mean speed from a 20-m sprint test). Eleven elite female soccer players from the same team participated in the study. All players performed a 20-m linear sprint test, and were assessed in up to 10 official matches using Global Positioning System technology. Magnitude-based inferences were used to test for meaningful differences. Results revealed that irrespective of adopting fixed or individual speed thresholds, female players produced only a few RSS during matches (2.3 ± 2.4 sequences using the fixed threshold and 3.3 ± 3.0 sequences using the individually based threshold), with most sequences composing of just 2 sprints. Additionally, central defenders performed fewer sprints (10.2 ± 4.1) than other positions (fullbacks: 28.1 ± 5.5; midfielders: 21.9 ± 10.5; forwards: 31.9 ± 11.1; with the differences being likely to almost certainly associated with effect sizes ranging from 1.65 to 2.72), and sprinting ability declined in the second half. The data do not support the notion that RSS occurs frequently during soccer matches in female players, irrespective of using fixed or individual speed thresholds to define sprint occurrence. However, repeated-sprint ability development cannot be ruled out from soccer training programs because of its association with match-related performance.

Syngeneic B16F10 Melanoma Causes Cachexia and Impaired Skeletal Muscle Strength and Locomotor Activity in Mice

Muscle wasting has been emerging as one of the principal components of cancer cachexia, leading to progressive impairment of work capacity. Despite early stages melanomas rarely promotes weight loss, the appearance of metastatic and/or solid tumor melanoma can leads to cachexia development. Here, we investigated the B16F10 tumor-induced cachexia and its contribution to muscle strength and locomotor-like activity impairment. C57BL/6 mice were subcutaneously injected with 5 × 10⁴ B16F10 melanoma cells or PBS as a Sham negative control. Tumor growth was monitored during a period of 28 days. Compared to Sham mice, tumor group depicts a loss of skeletal muscle, as well as significantly reduced muscle grip strength and epididymal fat mass. This data are in agreement with mild to severe catabolic host response promoted by elevated serum tumor necrosis factor-alpha (TNF-α), interleukin-6 (IL-6) and lactate dehydrogenase (LDH) activity. Tumor implantation has also compromised general locomotor activity and decreased exploratory behavior. Likewise, muscle loss, and elevated inflammatory interleukin were associated to muscle strength loss and locomotor activity impairment. In conclusion, our data demonstrated that subcutaneous B16F10 melanoma tumor-driven catabolic state in response to a pro-inflammatory environment that is associated with impaired skeletal muscle strength and decreased locomotor activity in tumor-bearing mice.

Torque-angle-velocity Relationships and Muscle Performance of Professional and Youth Soccer Players

Soccer matches consist of a variety of different activities, including repeated sprints. Time to attain velocity (TTAV), load range (LR) and the torque-angle-velocity relationship (TAV_3D) represent an important measurement of muscle performance, however there are few related studies. The aim of this study was to compare these outcomes between soccer players of different age category. 17 professional (PRO) and 17 under-17 (U17) soccer players were assessed for concentric knee flexion/extension at 60, 120 and 300°/s. For the extensor muscles, differences were found in favor of the U17 group for TTAV and LR outcomes at 120°/s, however, the PRO group maintained higher torques in both movement directions in comparison to the U17 in TAV_3D evaluation. These results suggest that muscle performance of the PRO group is more efficient than the U17 group.

Arterial tissue and plasma concentration of enzymatic-driven oxysterols are associated with severe peripheral atherosclerotic disease and systemic inflammatory activity

INTRODUCTION

Cholesterol undergoes oxidation via both enzymatic stress- and free radical-mediated mechanisms, generating a wide range of oxysterols. In contrast to oxidative stress-driven metabolites, enzymatic stress-derived oxysterols are scarcely studied in their association with atherosclerotic disease in humans.

METHODS

24S-hydroxycholesterol (24S-HC), 25-hydroxycholesterol (25-HC), and 27-hydroxycholesterol (27-HC) were assessed in plasma and arteries with atherosclerotic plaques from 10 patients (54-84 years) with severe peripheral artery disease (PAD) as well as arteries free of atherosclerotic plaques from 13 individuals (45-78 years, controls).

RESULTS

Plasma 25-HC was higher in PAD individuals than in controls (6.3[2] vs. 3.9[1.9] ng/mgCol; p = 0.004). 24S-HC and 27-HC levels were, respectively, five- and 20-fold higher in the arterial tissue of PAD individuals than in those of the controls (p = 0.016 and p = 0.001). Plasma C-reactive protein correlated with plasma 24-HC (r = 0.51; p = 0.010), 25-HC (r = 0.75; p < 0.001), 27-HC (r = 0.48; p = 0.015), and with tissue 24S-HC (r = 0.4; p = 0.041) and 27-HC (r = 0.46; p = 0.023).

CONCLUSION

Arterial intima accumulation of 27-HC and 24S-HC is associated with advanced atherosclerotic disease and systemic inflammatory activity in individuals with severe PAD.

Analysis of the distances covered by first division brazilian soccer players obtained with an automatic tracking method

Methods based on visual estimation still is the most widely used analysis of the distances that is covered by soccer players during matches, and most description available in the literature were obtained using such an approach. Recently, systems based on computer vision techniques have appeared and the very first results are available for comparisons. The aim of the present study was to analyse the distances covered by Brazilian soccer players and compare the results to the European players', both data measured by automatic tracking system. Four regular Brazilian First Division Championship matches between different teams were filmed. Applying a previously developed automatic tracking system (DVideo, Campinas, Brazil), the results of 55 outline players participated in the whole game (n = 55) are presented. The results of mean distances covered, standard deviations (s) and coefficient of variation (cv) after 90 minutes were 10,012 m, s = 1,024 m and cv = 10.2%, respectively. The results of three-way ANOVA according to playing positions, showed that the distances covered by external defender (10642 ± 663 m), central midfielders (10476 ± 702 m) and external midfielders (10598 ± 890 m) were greater than forwards (9612 ± 772 m) and forwards covered greater distances than central defenders (9029 ± 860 m). The greater distances were covered in standing, walking, or jogging, 5537 ± 263 m, followed by moderate-speed running, 1731 ± 399 m; low speed running, 1615 ± 351 m; high-speed running, 691 ± 190 m and sprinting, 437 ± 171 m. Mean distance covered in the first half was 5,173 m (s = 394 m, cv = 7.6%) highly significant greater (p < 0.001) than the mean value 4,808 m (s = 375 m, cv = 7.8%) in the second half. A minute-by-minute analysis revealed that after eight minutes of the second half, player performance has already decreased and this reduction is maintained throughout the second half. Key pointsA novel automatic tracking method was presented. No previous work was found in the literature reporting data of simultaneous trajectories of all soccer players obtained by an automatic tracking method.The study reveals 7% reduction in mean distance covered in the second half and moreover after eight minutes of the second half, player performance has already decreased and this reduction is maintained throughout the second half.