Biomechanics Institute of Valencia

Background: The back squat is one of the most widely prescribed resistance exercises in athletic performance, rehabilitation, and strength training programs. Despite its extensive use, considerable variability exists in coaching practices and execution strategies due to differences in anthropometry, mobility, and training objectives. The absence of a unified biomechanical framework has contributed to inconsistent technique instruction and increased risk of mechanical overload and injury. This study presents a conceptual biomechanical framework derived from existing literature and biomechanical modeling to standardize squat technique evaluation. Objective: The purpose of this position paper is to propose a comprehensive biomechanical framework for the back squat that integrates anthropometric considerations, joint mechanics, neuromuscular control, and real-time biomechanical feedback to guide technique standardization and injury-risk reduction. Methods: The framework synthesizes evidence from biomechanical literature and integrates quantitative parameters derived from three-dimensional motion capture, force-plate kinetics, surface electromyography (EMG), and inertial measurement unit (IMU) data. Twenty-six biomechanical parameters (A–Z) were organized to describe key aspects of squat execution, including base of support, bar path mechanics, joint kinematics, torque distribution, neuromuscular control, and movement consistency under load. Framework and Key Parameters: The proposed model establishes recommended ranges for joint angles, intra-abdominal pressure, ground reaction forces, and bar-path deviation during the back squat. The framework also identifies critical fault thresholds (e.g., lumbar flexion >10°, knee valgus >5°, bar path deviation >3 cm) and integrates sensor-based monitoring approaches to facilitate real-time feedback during training and rehabilitation contexts. Practical Implications: By combining anthropometric individualization with objective biomechanical measurement, this framework provides a structured reference for coaches, clinicians, and researchers seeking to optimize squat mechanics, enhance performance outcomes, and reduce injury risk. Adoption of standardized biomechanical parameters may improve consistency in instruction, support movement screening protocols, and advance evidence-based practice in strength and conditioning.

The purpose of this study was to investigate the athlete biomechanical differences across three artificial turfs associated with changes in athletic performance. Eighteen university grid-iron football players performed three modified football specific movements (agility drill, vcut, three-cone drill) on three artificial turf surfaces (Control, Shockpad and Low Faceweight) that have been shown to alter athletic performance. The utilized traction and player kinematics were recorded and compared between the surfaces using a repeated-measures ANOVA within participant factors of surface and between participants’ factors of player position. The significant effect of the surface on utilized traction at takeoff, and the frontal plane ankle angle was present with the players utilizing a lower traction and peak frontal plane ankle angle on the low-traction surface (Low Faceweight). During the agility drill and vcut, the significant effect of the surface was seen for peak frontal plane rearfoot–floor angle, with players having a flatter foot on high-traction surfaces (Control and Shockpad). Across tasks, high-traction surfaces were associated with flatter foot orientations and increased frontal plane ankle and foot kinematics during the cutting movements.

The intrinsic microenvironments of biomolecular condensates play decisive roles in applications spanning synthetic cell construction, targeted drug delivery systems, cell engineering, bioreactor development, and precision disease interventions. Recent studies highlight that divalent cations play a central role in modulating the internal condensate microenvironments. However, the complex multivalent interaction networks within condensates create significant challenges in unraveling the molecular mechanisms. This study employs model systems of cationic peptides (arginine decamer (R10), lysine decamer (K10)) and polyanionic polymers (polyadenylic acid (PolyA), polyinosinic acid (PolyI), polyglutamic acid (PolyE), polyaspartic acid (PolyD)) to systematically investigate Mg2+-mediated modulation of condensate properties. Mg2+ enrichment dynamically controls ionic microenvironments through competitive interactions with polyelectrolytes. When interpolyelectrolyte affinity dominates (e.g., R10/PolyA), weakly bound Mg2+ enhances the surface potential, promoting small-molecule enrichment and ribozyme catalytic efficiency. Conversely, when Mg2+-polyelectrolyte binding prevails (e.g., R10/PolyE), stable ion-polyelectrolyte complexes reduce the system polarity and amplify dye accumulation but compromise phase stability. Macrophage coculture experiments demonstrate that R10/PolyA@Mg condensates enable targeted magnesium delivery, significantly boosting TNF-α secretion and immune regulation. These findings establish a mechanistic framework for ion-mediated control of condensate microenvironments, offering theoretical insights into the intracellular ionic regulation of phase separation. This work suggests a Mg2+-responsive condensate design strategy for modulating macrophage responses, providing a foundation for the design of biomaterials with a tunable immunostimulatory potential.

ObjectivesThe purpose of this study was to (1) establish the agreement of multiple expert reviewers’ identification of hamstring strain injury (HSI) scenarios and related body postures among National Football League (NFL) players and (2) determine the prevalence of each HSI scenario and associated body posture in the NFL between 2018 and 2022.MethodsVideos from 305 HSIs in the NFL were reviewed in a blinded fashion by two expert reviewers, who classified the injuries into seven predefined injury scenarios developed by a separate committee of experts. Lower extremity body postures were also identified. Cohen’s Kappa coefficients were calculated to determine inter-rater agreement and used to select the subset of injuries to be described via injury scenario and body posture with the intent of minimising bias or ambiguity in reporting.Results137/305 (45%) injury videos met the criteria for inclusion in the final dataset based on assessment of classification agreement. Agreement in injury scenario and body posture ranged from poor to moderate. Sprinting injuries were the most common scenario (59/137, 43%). Unique scenarios specific to American football demonstrated the importance of excessive trunk flexion during contact, or during acceleration and change of direction (54/137, 39%).ConclusionsUsing a systematic approach involving multiple expert reviewers, sprint-related injury scenarios were highlighted as the most common injury scenario for HSIs. Specific to American football; however, excessive trunk flexion during contact plays or during acceleration and change of direction may be important to consider for injury prevention or rehabilitation from HSIs.

This PhD thesis explores the neuroimmune mechanisms in neck pain and investigates if musculoskeletal physiotherapy affects these mechanisms. The research aims to better understand the physiological processes of neck pain by examining both systemic inflammatory markers and spinal neuroinflammation, and by assessing how musculoskeletal interventions influence these neuroimmune responses. The thesis is divided into three parts. Part I: Systemic Inflammatory Markers in Neck Pain This section investigates whether people with neck pain exhibit elevated levels of systemic inflammatory markers compared to pain-free controls and how these markers relate to symptoms and pain persistence. It includes four chapters: Chapter 1 reviews neuroimmune interactions in musculoskeletal conditions, detailing the role of the immune and nervous systems and their interplay in spinal pain and nerve injury. It also discusses prospects for targeted therapies. Chapter 2 addresses the complexity of interpreting systemic inflammatory markers, cautioning against oversimplified conclusions due to potential confounding variables. Chapter 3 presents a cross-sectional study identifying associations between systemic neuroimmune markers and clinical, psychological, and lifestyle factors in people with non-specific neck pain and painful cervical radiculopathy. Chapter 4 describes a prospective cohort study that follows people with acute neck pain over six months, identifying distinct recovery trajectories based on inflammatory, clinical, and psychological profiles. Part II: Spinal Neuroinflammation in Cervical Radiculopathy This part focuses on developing and applying neuroimaging techniques to assess localised inflammation in the spinal cord and neuroforamina of patients with painful cervical radiculopathy. It includes two chapters: Chapter 5 introduces a pharmacokinetic model using the radiotracer [11C]DPA713 with dynamic PET/CT imaging to quantify neuroinflammation. The study establishes the model’s test-retest reliability. Chapter 6 applies this method to show that patients with painful cervical radiculopathy have increased tracer binding, indicating neuroinflammation, at affected sites compared to controls. It also explores correlations with clinical symptoms. Part III: Effects of Musculoskeletal Physiotherapy on Neuroimmune Mechanisms This section evaluates how musculoskeletal physiotherapy impacts systemic and localised neuroimmune responses. It includes five chapters: Chapter 7 is a systematic review and meta-analysis that suggests joint and nerve mobilisation can influence neuroimmune responses in animal models and some human studies, though research in humans remains limited. Chapter 8 introduces the CROM-VAS Test, a novel tool to assess short-term changes in pain intensity post-treatment. The test is shown to have good inter-rater reliability. Chapter 9 outlines the protocol for a randomised, placebo-controlled trial examining the effects of joint mobilisation and manipulation on systemic neuroimmune markers in people with persistent neck pain. Chapter 10 presents the results of this trial, which found no significant short-term changes in systemic markers following a single session of treatment. Chapter 11 shifts focus to localised inflammation, evaluating spinal neuroinflammation before and after a six-week neural tissue management intervention in two patients. The intervention showed potential in reducing neuroinflammation. The thesis concludes with a comprehensive discussion of the findings (Chapter 12), summaries in Dutch and English (Chapter 13), appendices (Chapter 14), and author information and publications (Chapter 15). Overall, this thesis highlights the complex neuroimmune landscape of neck pain and provides foundational evidence for the potential, yet still limited, impact of musculoskeletal physiotherapy on local neuroinflammation. It underscores the need for more mechanistic research for a better understanding of neck pain and the workingmechanisms of musculosksletal physiotherapy.

Cycling offers numerous health benefits. However, an improperly adjusted saddle setback can lead to discomfort and injury. There is limited evidence about the effect of intensity and sex when manipulating saddle setback. The present study analyzes how saddle setback, pedaling intensity and sex impact on comfort, perceived exertion, and lower limb kinematics in recreational cyclists. Thirty-four (N = 34) recreational cyclists (14 women and 20 men) were measured. Cyclists performed the same protocol on a cyclergometer under 3 different saddle setbacks (preferred, forward, backward) and 2 pedaling intensities (first and second ventilatory thresholds, VT1 and VT2). Perceived exertion was only significantly increased during VT2, compared to VT1 (p < 0.05) and comfort was lower at backward saddle setback compared to forward saddle setback and preferred condition (p < 0.05). Angular kinematics showed significant differences (p < 0.05), mainly influenced by saddle setback and intensity. A more rearward saddle position (+ 10%) resulted in greater extension across all joints, while higher intensities (VT2) led to reduced hip flexion and increased ankle dorsiflexion. The multiple linear regression analysis showed the existence of a relationship between the variables of the cyclist’s height, saddle height, inseam length, and foot length. Therefore, a new equation for adjusting saddle setback was calculated from the present study. A greater saddle setback increases knee and ankle joint extension and reduces hip flexion-extension, especially at higher intensities, while also decreasing comfort without significantly affecting perceived exertion.

ABSTRACTMorphological analysis of the human body is crucial for various applications in ergonomics and product design, with significant economic and commercial implications. This paper presents a novel exploration of statistical methods for the analysis of human body shapes based on 3D landmark data. It focuses on the application of well‐established statistical methods within the framework of Kendall's 3D shape space. It is well known that Kendall's 3D shape space has non‐constant curvature at all points. A key contribution of this study is the detailed examination of the curvature of Kendall's space at points corresponding to human body shapes, highlighting its implications for posterior statistical analysis. A study of the distances in the dataset is also carried out. From this point, we also compare the performance of intrinsic (Riemannian) methods and Euclidean approximations for mean shape estimation, group difference identification, and dimensionality reduction, providing a comprehensive assessment of their respective strengths and limitations in these contexts. These findings aim to improve the statistical understanding of body morphology and provide valuable guidance for applications in fields such as product design and ergonomics.