Biomechanics

Background/Objectives: Hip abductor-to-adductor (ABD:ADD) strength characteristics and muscle activation may contribute to lower-limb control during landing, but their respective associations with landing biomechanics remain unclear. This study examined associations of the ABD:ADD strength ratio, strength imbalance index, and EMG activation ratios with lower-limb biomechanics during forward and lateral single-leg landing. Methods: Twenty male Division I collegiate basketball and volleyball athletes completed isokinetic hip strength testing, maximal voluntary isometric contraction EMG testing, and forward (FWD) and lateral (LAT) single-leg landing tasks. EMG activation ratios were quantified at initial contact (IC), peak ground reaction force (GRF), and from IC to peak GRF. Correlation analyses and exploratory regressions were performed. Results: During FWD Landing, strength measures were associated with knee flexion, knee transverse-plane angle, and hip frontal-plane moment, while the EMG ratio at IC was associated with hip and knee frontal-plane angles and hip transverse-plane moment. During LAT Landing, strength measures were associated with hip and knee kinematics and hip and knee frontal-plane moments. Mean early-phase EMG ratio was associated with hip flexion, knee flexion, hip frontal-plane angle, and hip frontal-plane moment. Retained regression models explained 20–33% of outcome variance. Conclusions: Hip ABD:ADD strength characteristics and EMG activation ratios were associated with different aspects of single-leg landing biomechanics. During lateral landing, the mean early-phase EMG ratio was associated with hip and knee flexion angles and hip frontal-plane angle at peak GRF. These exploratory findings indicate that strength capacity and task-specific neuromuscular recruitment provide complementary information regarding hip muscle function during landing.

Background/Objectives: Finite element analysis (FEA) enables evaluation of internal stresses and strains in the foot that are difficult to measure experimentally. This review synthesizes computational evidence on foot biomechanics, focusing on metatarsal loading and stress fractures, hallux valgus pathomechanics and surgical correction, fracture fixation, plantar loading and footwear, and ligament and soft-tissue mechanics. Methods: This critical review is based on a documented, non-systematic search of Scopus and hand searching. Of 169 records retrieved, 123 were retained and 16 sources were added, with six additional references incorporated during revision, yielding a total of 145 references. Information on model geometry, material formulation, loading and boundary conditions, and validation was extracted. Results: Soft-tissue and plantar-fascia properties substantially influenced predicted plantar pressure and internal stress. Metatarsal loading varied with anatomy, gait phase, footwear, and boundary conditions. Hallux valgus models indicated that osteotomy geometry and displacement can redistribute joint and metatarsal stresses, while minimally invasive fixation constructs often provided predicted stability comparable to conventional techniques. Patient-specific imaging, musculoskeletal coupling, and machine-learning methods are expanding model capability. However, most reported results were deterministic outputs from single-subject geometries, and validation evidence was generally narrower than the clinical decisions for which the models were discussed. Conclusions: FEA provides model-based mechanistic insight into foot loading, deformity, and fixation and can support comparative mechanical evaluation of designs and constructs. Its outputs are hypothesis-generating: no reviewed fixation or footwear ranking has been tested against clinical outcomes, and the results should not be read as evidence of clinical effectiveness. Stronger experimental validation, population-based modeling, uncertainty quantification, and clearer definition of model context of use are required before patient-specific clinical decisions can be supported reliably.

Background/Objectives: The purpose of this study was to quantify and compare three-dimensional knee kinematics between competitive and recreational athletes during dynamic tasks. It was hypothesized that competitive athletes would exhibit greater knee range of motion (RoM). Methods: Thirty-five varsity athletes (eight lacrosse athletes, eleven soccer athletes, nine volleyball athletes, and seven basketball athletes were recruited from the varsity athlete population) and 26 recreational athletes performed a countermovement vertical jump and 90° sidestep cutting task, common return-to-sport tasks. Markerless motion capture (Theia 3D) was used to extract knee joint angles at initial contact and 200 ms post-contact and RoM across all three anatomical planes. Results: During the vertical jump, competitive athletes exhibited significantly greater sagittal-plane RoM (8–12°), while recreational athletes demonstrated greater frontal- and transverse-plane RoM. During cutting, transverse-plane RoM was significantly greater in recreational athletes than competitive athletes. These differences persisted after controlling jump height or center-of-mass speed via ANCOVA. After Benjamini–Hochberg FDR correction, five comparisons remained statistically significant, all involving the vertical jump. Conclusions: Competitive and recreational athletes exhibit distinct knee kinematic profiles, with plane-dependent directional differences. These findings indicate that the level of sport participation is associated with differences in knee kinematics during dynamic tasks, and the clinical and functional implications remain yet to be determined through further prospective research.