In vivo measurements of muscle specific tension in adults and children

This article is available open access through the publisher’s website at the link below. Copyright @ 2009 The Authors.To better understand the effects of pubertal maturation on the contractile properties of skeletal muscle in vivo, the present study investigated whether there are any differences in the specific tension of the quadriceps muscle in 20 adults and 20 prepubertal children of both sexes. Specific tension was calculated as the ratio between the quadriceps tendon force and the sum of the physiological cross-sectional area (PCSA) multiplied by the cosine of the angle of pennation of each head within the quadriceps muscle. The maximal quadriceps tendon force was calculated from the knee extension maximal voluntary contraction (MVC) by accounting for EMG-based estimates of antagonist co-activation, incomplete quadriceps activation using the interpolation twitch technique and magnetic resonance imaging (MRI)-based measurements of the patellar tendon moment arm. The PCSA was calculated as the muscle volume, measured from MRI scans, divided by optimal fascicle length, measured from ultrasound images during MVC at the estimated angle of peak quadriceps muscle force. It was found that the quadriceps tendon force and PCSA of men (11.4 kN, 214 cm2) were significantly greater than those of the women (8.7 kN, 152 cm2; P 0.05) between groups: men, 55 ± 11 N cm−2; women, 57.3 ± 13 N cm−2; boys, 54 ± 14 N cm−2; and girls, 59.8 ± 15 N cm−2. These findings indicate that the increased muscle strength with maturation is not due to an increase in the specific tension of muscle; instead, it can be attributed to increases in muscle size, moment arm length and voluntary activation level

The human patellar tendon moment arm assessed in vivo using dual-energy X-ray absorptiometry

Accurate assessment of muscle-tendon forces in vivo requires knowledge of the muscle-tendon moment arm. Dual-energy X-ray absorptiometry (DXA) can produce 2D images suitable for visualising both tendon and bone, thereby potentially allowing the moment arm to be measured but there is currently no validated DXA method for this purpose. The aims of this study were (i) to compare in vivo measurements of the patellar tendon moment arm (d) assessed from 2D DXA and magnetic resonance (MR) images and (ii) to compare the reliability of the two methods. Twelve healthy adults (mean±SD: 31.4±9.5yr; 174.0±9.5cm; 76.2±16.6kg) underwent two DXA and two MR scans of the fully extended knee at rest. The tibiofemoral contact point (TFCP) was used as the centre of joint rotation in both techniques, and the d was defined as the perpendicular distance from the patellar tendon axis to the TFCP. The d was consistently longer when assessed via DXA compared to MRI (+3.79±1.25mm or +9.78±3.31%; P<0.001). The test-retest reliability of the DXA [CV=2.13%; ICC=0.94; ratio limits of agreement (RLA)=1.01 (*/÷1.07)] and MR [(CV=2.27%; ICC=0.96; RLA=1.00 (*/÷1.07)] methods was very high and comparable between techniques. Moreover, the RLA between the mean DXA and MRI d values [1.097 (*/÷1.061)] demonstrated very strong agreement between the two methods. In conclusion, highly reproducible d measurements can be determined from DXA imaging with the knee fully extended at rest. This has implications for the calculation of patellar tendon forces in vivo where MR equipment is not available. © 2014 Elsevier Ltd

The contributions of fibre atrophy, fibre loss, in situ specific force and voluntary activation to weakness in sarcopenia

The contributions of fibre atrophy, fibre loss, in situ specific force and voluntary activation to weakness in sarcopenia remain unclear. To investigate, forty older (20 women; age 72±4yrs) and 31 younger adults (15 women, age 22±3yrs) completed measurements. The knee extensor maximal voluntary torque (MVC) was measured as well as voluntary activation, patella tendon moment arm length, muscle volume and fascicle architecture to estimate in situ specific force. Fibre cross-sectional area (FCSA), fibre numbers and connective tissue contents were also estimated from vastus lateralis biopsies. The MVC, quadriceps volume and specific force were 39%, 28% and 17% lower, respectively, in old compared with young, but voluntary activation was not different. The difference in muscle size was due in almost equal proportions to lower type II FCSA and fewer fibres. Five years later (n=23) the MVC, muscle volume and voluntary activation in old decreased an additional 12%, 6% and 4%, respectively, but there was no further change in specific force. Conclusions: in situ specific force declines relatively early in older age and reduced voluntary activation occurs later, but the overall weakness in sarcopenia is mainly related to loss of both type I and II fibres and type II fibre atrophy

COORDINATION VARIABILITY DURING OVERGROUND, TREADMILL AND TREADMILL-ON-DEMAND RUNNING

The purpose of this study was to investigate differences in lower extremity coordination variability between overground, treadmill and treadmill-on-demand running. A modified normalised root mean square difference technique was used to quantify the variability in lower extremity coordination calculated from the kinematic data collected during ten strides of overground, treadmill and treadmill-on-demand running at 3.5 m.s". Although no significant differences were observed between the two types of treadmill, significantly reduced (p < 0.02) coordination variability was seen in the treadmill and treadmill-ondemand conditions compared to overground locomotion. Therefore, a constant belt speed during treadmill locomotion does not account for the differences seen between overground and treadmill running and further work is required to determine factors that cause the difference

Polymorphisms in PTK2 are associated with skeletal muscle specific force: an independent replication study

Purpose The aim of the study was to investigate two single nucleotide polymorphisms (SNP) in PTK2 for associations with human muscle strength phenotypes in healthy men. Methods Measurement of maximal isometric voluntary knee extension (MVCKE) torque, net MVCKE torque and vastus lateralis (VL) specific force, using established techniques, was completed on 120 Caucasian men (age = 20.6 ± 2.3 year; height = 1.79 ± 0.06 m; mass = 75.0 ± 10.0 kg; mean ± SD). All participants provided either a blood (n = 96) or buccal cell sample, from which DNA was isolated and genotyped for the PTK2 rs7843014 A/C and rs7460 A/T SNPs using real-time polymerase chain reaction. Results Genotype frequencies for both SNPs were in Hardy–Weinberg equilibrium (X 2 ≤ 1.661, P ≥ 0.436). VL specific force was 8.3% higher in rs7843014 AA homozygotes than C-allele carriers (P = 0.017) and 5.4% higher in rs7460 AA homozygotes than T-allele carriers (P = 0.029). No associations between either SNP and net MVCKE torque (P ≥ 0.094) or peak MVCKE torque (P ≥ 0.107) were observed. Conclusions These findings identify a genetic contribution to the inter-individual variability within muscle specific force and provides the first independent replication, in a larger Caucasian cohort, of an association between these PTK2 SNPs and muscle specific force, thus extending our understanding of the influence of genetic variation on the intrinsic strength of muscle.Published versio

Identifying Robust Risk Factors for Knee Osteoarthritis Progression: An Evolutionary Machine Learning Approach

Knee osteoarthritis (KOA) is a multifactorial disease which is responsible for more than 80% of the osteoarthritis disease’s total burden. KOA is heterogeneous in terms of rates of progression with several different phenotypes and a large number of risk factors, which often interact with each other. A number of modifiable and non-modifiable systemic and mechanical parameters along with comorbidities as well as pain-related factors contribute to the development of KOA. Although models exist to predict the onset of the disease or discriminate between asymptotic and OA patients, there are just a few studies in the recent literature that focused on the identification of risk factors associated with KOA progression. This paper contributes to the identification of risk factors for KOA progression via a robust feature selection (FS) methodology that overcomes two crucial challenges: (i) the observed high dimensionality and heterogeneity of the available data that are obtained from the Osteoarthritis Initiative (OAI) database and (ii) a severe class imbalance problem posed by the fact that the KOA progressors class is significantly smaller than the non-progressors’ class. The proposed feature selection methodology relies on a combination of evolutionary algorithms and machine learning (ML) models, leading to the selection of a relatively small feature subset of 35 risk factors that generalizes well on the whole dataset (mean accuracy of 71.25%). We investigated the effectiveness of the proposed approach in a comparative analysis with well-known FS techniques with respect to metrics related to both prediction accuracy and generalization capability. The impact of the selected risk factors on the prediction output was further investigated using SHapley Additive exPlanations (SHAP). The proposed FS methodology may contribute to the development of new, efficient risk stratification strategies and identification of risk phenotypes of each KOA patient to enable appropriate interventions

Identifying soccer players’ playing styles: a systematic review

Identifying playing styles in football is highly valuable for achieving effective performance analysis. While there is extensive research on team styles, studies on individual player styles are still in their early stages. Thus, the aim of this systematic review was to provide a comprehensive overview of the existing literature on player styles and identify research areas required for further development, offering new directions for future research. Following the PRISMA guidelines for systematic reviews, we conducted a search using a specific strategy across four databases (PubMed, Scopus, Web of Science, and SPORTDiscus). Inclusion and exclusion criteria were applied to the initial search results, ultimately identifying twelve studies suitable for inclusion in this review. Through thematic analysis and qualitative evaluation of these studies, several key findings emerged: (a) a lack of a structured theoretical framework for player styles based on their positions within the team formation, (b) absence of studies investigating the influence of contextual variables on player styles, (c) methodological deficiencies observed in the reviewed studies, and (d) disparity in the objectives of sports science and data science studies. By identifying these gaps in the literature and presenting a structured framework for player styles (based on the compilation of all reported styles from the reviewed studies), this review aims to assist team stakeholders and provide guidance for future research endeavors

Analysis of playing styles in European football: insights from a visual mapping approach

Performance analysis is a rapidly evolving field in football and a subject of extensive international scientific research. Recognizing playing styles is now considered essential for effective performance analysis. This study aimed to create a map of 174 teams from 11 European leagues that could, through visualization, provide practical insights applicable to football teams' daily practice. The t-distributed Stochastic Neighbor Embedding (t-SNE) method was used to reduce the dimensions of 19 tactical situations derived from previous research. The resulting two coordinates were employed to generate a scatter plot, and simultaneous k-means cluster analysis (k = 11) was conducted. Greece (86%) and Scotland (83%) had the highest percentages of teams within the same cluster as their country's average, while Germany (11%) and Croatia (10%) had the lowest percentages. In terms of cluster dispersion, England ranked first with 9 clusters, followed by Spain and Germany with 7 clusters, while Greece and Scotland had the least with 2 clusters. The visualization and clustering of teams led to the following conclusions. a) There are variations in playing styles not only between teams from different countries but also within the same country, particularly when there is a disparity in quality. b) Coaches' philosophies and implemented strategies significantly influence the adoption of playing styles by teams. These findings provide valuable information for coaches, analysts, and team scouts, assisting them in their respective roles. By understanding the diverse playing styles present in European football, practitioners can tailor their approaches to optimize team performance and gain a competitive edge

Exploring the influence of playing styles on physical demands in professional football

Purpose. The aim of the current study was to investigate differences in the physical performance indicators when implementing various playing styles across a range of tactical situations. Methods. The sample comprised 238 matches (476 observations) from the 2021–22 season of the Turkish league’s 1st division. For each observation, nine physical performance indicators obtained through the InStat Scout optical tracking method were analysed. Additionally, 19 factor scores (representing 19 tactical situations) derived from previous research were utilised to categorise each observation into two distinct playing styles. Results. Effect sizes (Cohen’s d) obtained from independent samples t-tests revealed significant differences in physical performance indicators in 17 out of the 19 tactical situations. Match interruptions, transitions, final attempts, and the starting position on the field from which a team initiates pressing were identified as influential factors in determining physical demands. Conversely, the playing style adopted by teams during the build-up phase (possession or direct play) did not appear to significantly alter the physical demands. Conclusions. The results indicate that in various tactical situations, the physical demands vary based on the playing style adopted by the teams. These findings carry practical implications, as they can assist coaches in making decisions that combine tactical and physical factors

A multivariate and cluster analysis of diverse playing styles across European football leagues

Performance analysis is a valuable tool for team coaches and has been the subject of extensive study in international research. A significant portion of the scientific literature in the field of football has been devoted to studying playing styles in recent years. The identification of playing styles is now regarded as crucial for conducting an efficient performance analysis. This study aimed to explore the variances in playing styles among eleven distinct European domestic football leagues. A comprehensive sample of 2996 matches, accounting for 5992 observations, was scrutinized. Nineteen latent variables, representing thirty-eight different game styles previously identified in sports science literature, served as the basis for this investigation. Multivariate analysis of variance (MANOVA) revealed significant differences across countries in ten out of nineteen variables. The variables with the highest effect sizes (partial η2) were transition game, effective game, and defending aggressively, implying that these factors contributed to the most substantial differences among countries. To visualize these disparities, the t-distributed stochastic neighbor embedding (t-SNE) method was employed. Subsequently, k-means clustering was applied to the t-SNE results, grouping the eleven participating countries into five distinct clusters. A unique playing style was discerned in the Scottish league (Cluster 4), setting it apart from all other leagues. Other clusters included Austria, Belgium, and Switzerland (Cluster 1); Spain, Turkey, and Croatia (Cluster 2); Greece and Italy (Cluster 3); and Germany and England (Cluster 5). The findings offer valuable insights for coaches, managers, scouts, and sporting directors, potentially guiding the development of effective game styles and enhancing recruitment strategies for both players and coaches