Biomechanics, Volume 2, Issue 4 (December 2022) – 11 articles

Different measurements of foot morphological characteristics can effectively predict foot muscle strength. However, it is still uncertain if structural and postural alterations leading to foot pronation could be compensated with more efficient function of the intrinsic foot muscles and how mobility and strength are associated. Additionally, the relationship between foot mobility and the strength of the intrinsic muscles that control the foot arch is still unclear. Therefore, this study aimed to investigate the morphological parameters between dominant and non-dominant feet and the relationship between the intrinsic foot muscle strength and foot mobility in recreational runners. We used a cross-sectional study design to evaluate twenty-four healthy recreational runners (minimum 15 km/week) with an average training history of 70 ± 60 months. Foot Posture Index (FPI-6), isometric intrinsic muscle strength, overall morphology, and normalized mobility of both feet were assessed. Parametric tests analyzed the unidimensional measures, and paired analysis determined differences between dominant and non-dominant sides. Pearson’s and Spearman’s correlation coefficients determined the relationships between normalized strength and the variables of interest (CI = 95%). There was no significant association between intrinsic foot muscle strength and mobility. The only difference observed was between the dominant and non-dominant foot regarding the normalized foot length and midfoot width during non-weight-bearing, with small and medium effect sizes, respectively. Neither foot morphology nor foot mobility was associated with strength from intrinsic foot muscles in healthy recreational runners. Further work should explore the relationship investigated in our study with professional athletes and runners with symptomatic lower limb injuries to potentialize training and rehabilitation protocols. Full article

Background: Stair climbing is a part of the basic activities of daily living. Previous biomechanical analyses of stairs have been conducted in the laboratory, resulting in only a few steps. Therefore, the biomechanical characteristics of long stair climbing in the real world remain unclear. The purpose of this study was to identify differences in kinematic and kinetic in the lower limb between the beginning and end phases of long stair climbing in an outdoor environment using a wearable motion analysis system. Eight subjects (four males and four females) were included in the data analysis (age: 23.6 ± 0.5 years). The long stair was 66 consecutive steps out of 202 stone steps. A wearable motion analysis system comprised six inertial measurement units and foot pressure sensors. The maximum ankle joint flexion angle in the end phase was significantly increased more than in the beginning phase (p < 0.001). On the other hand, the other kinematic, kinetic, and stair climbing speeds showed no significant difference between the phases. The findings indicated that fatigue during long stair climbing might increase ankle dorsiflexion to compensate for forwarding propulsion. Full article

The single leg squat (SLS), forward step down (FSD), and lateral step down (LSD) are clinically reliable movement screens for identifying motion imbalances. The current understanding for the kinematic profiles of each task is limited to discrete time points such as peak knee flexion. However, analyses of the entire movement would better aid clinicians when selecting the appropriate task for rehabilitation or movement screen purposes. The current study used Statistical Parametric Mapping to ascertain differences in the kinematic waveforms for the entire duration of each task. The trunk, pelvis, hip, and knee were analyzed in the sagittal and frontal planes. Data for each variable and task were analyzed from 0–100% of the movement. Primary findings indicated that the FSD provoked a greater magnitude of knee abduction than the SLS and LSD from 26–66% of the movement. The SLS generated the greatest amounts of trunk, pelvic, and hip flexion for the entirety of the movement. The LSD elicited the least amount of ipsilateral trunk lean (90–100%). Thus, the FSD may be optimal for assessing frontal plane knee motion as a screen for injury risk, while the SLS has potential to place increased sagittal plane demand on the muscles of the hip. Full article

The purpose of this study was to analyze the effects of locking plate fixation used for bridging of tibial segmental ostectomy and of cast immobilization on gait biomechanics in goats. We hypothesized that stable fixation of a segmental bone defect, using a locking plate construct, would result in minimal changes in biomechanical variables of gait in goats, but full-limb immobilization would result in lasting alterations in the immobilized limb’s gait kinetics. A pressure-sensing walkway was used to measure biomechanical characteristics for stride, gait, and walking vertical force. Thirteen, non-lame adult Boer-cross goats were trained to walk over a pressure-sensing walkway prior to instrumentation. Segmental ostectomy was performed on the right hind tibia of each goat and the defect was stabilized using bridging plate fixation with a locking compression plate. Per the protocol of an ongoing orthopedic study, the same goats underwent right hindlimb cast immobilization between one and four months postoperatively. Data was collected preoperatively and then over twelve months postoperatively in goats with unrestricted mobility. Statistical analysis revealed no significant alterations in hindlimb kinematics or maximum force when comparing the period after surgery with that after cast immobilization; significant decreases in forelimb stride length and velocity were noted postoperatively but normalized prior to cast placement, suggesting the overall functional stability of fixation. Cast immobilization had a profound and sustained effect on gait with significant alterations in both forelimb kinetics and hindlimb kinetics and kinematics for the remainder of the trial period; increased hindlimb asymmetry characterized by greater weight distribution and impulse to the left hindlimb was observed, suggesting the potential for long-term and/or permanent detrimental effects of prolonged limb immobilization. Full article

(1) Background: We aimed to compare gender differences in knee biomechanics and neuromuscular characteristics, and to determine the relationships between lower limb muscle pre-activations and knee biomechanics during a single leg drop landing, in order to identify riskier landing patterns to prevent injury and intervene properly. (2) Methods: Descriptive laboratory cross-sectional study on 38 healthy untrained subjects with low to moderate physical activity status. (3) Results: During the initial-contact phase of landing, females demonstrated greater peak vertical ground reaction force (GRF) normalized to body weight (49.12 ± 7.53 vs. 39.88 ± 5.69 N/kg; p < 0.001; Hedge’s g = 1.37), peak knee anterior reaction force normalized to body weight (0.23 ± 0.04 vs. 0.17 ± 0.05 N/kg; p < 0.001; Hedge’s g = 1.33), and decreased pre-activation of the semitendinosus (45.10 ± 20.05% vs. 34.03 ± 12.05%; p = 0.04; Hedge’s g = 0.67). The final regression equation was peak knee anterior reaction force = 0.024 + 0.025 (peak knee flexion moment) − 0.02 (semitendinosus-to-vastus lateralis pre-activation ratio) + 0.003 (peak vertical GRF) (R² = 0.576, p < 0.001). (4) Conclusions: Overall, the data provided in this study support that a reduced semitendinosus-to-vastus lateralis pre-activation ratio predicted an increase in knee anterior reaction force and potentially an increase in ACL forces. Female non-athletes had gender-specific landing characteristics that may contribute to ACL injury. Future studies are warranted to consider more possible predictors of non-contact ACL injury. Full article

The application of Whole Body Vibration (WBV) has been demonstrated to be effective in improving muscle strength/power by a number of studies, but an optimal training protocol has never been established. This paper presents a review of studies on the effects of WBV on muscles and an analysis of data to identify the optimal protocols for the most beneficial neuromuscular responses in terms of vibration frequency, amplitude, knee flexion angle, body posture (standing, sitting, supine, prone), muscle type (quadriceps, hamstrings), and vibration mode (superoinferior, anteroposterior, rotational). Ninety articles were selected for final review from initially selected 2093 articles using PRISMA guidelines. The findings suggest that the beneficial effects of WBV increase with frequency and amplitude but the optimal frequency and amplitude have not been established. The effect of the knee flexion angle is not clear. The optimal WBV protocol should be determined by considering the adverse effects of WBV on all parts of the human body including that related to head acceleration. WBV in sitting or lying positions may provide a better muscle response than standing. Directions for future research are discussed with regard to establishing the optimal WBV protocol as a safe and effective therapeutic/exercise modality for improving muscle strength and health. Full article

While being an integral part of both the offensive and defensive segments of the game, the biomechanical parameters of setting motions remain understudied in the scientific literature. Thus, the purpose of the present study was to examine differences in kinetic and kinematic characteristics between: (a) three types of setting motions (i.e., front, middle, back); (b) two types of setting approaches (i.e., stationary, step-in); and (c) proficient (PRO) and non-proficient (N-PRO) volleyball players. Twenty recreationally active females performed five stationary and five step-in setting approaches to Zone 4–2 in a randomized order. Uni-dimensional force plate sampling at 1000 Hz and high-definition camera recording at 30 fps were used to obtain kinetic and kinematic variables of interest. The total number of setting attempts performed by each subject was 30, accounting for a grand total of 600 attempts. PRO setters had less knee flexion, shoulder flexion, and ankle dorsiflexion at the initial concentric phase of the volleyball setting motion when compared to the N-PRO setters. Moreover, significantly greater peak concentric and landing forces, impulse, rate of force development, and vertical jump height were observed for PRO setters compared to N-PRO setters, while no significant differences were found between different setting targets and approaches. Full article

The study presents a novel scheme that recognizes and classifies different sub-phases within the involuntary breathing movement (IBM) phase during breath-holding (BH). We collected force data from eight recreational divers until the conventional breakpoint (CB). They were in supine positions on force plates. We segmented their data into no-movement (NM) phases, i.e., the easy phase (EP) and IBM phase (comprising several events or sub-phases of IBM). Acceleration and jerk were estimated from the data to quantify the IBMs, and phase portraits were developed to select and extract specific features. K means clustering was performed on these features to recognize different sub-phases within the IBM phase. We found five–six optimal clusters separating different sub-phases within the IBM phase. These clusters separating different sub-phases have physiological relevance to internal struggles and were labeled as classes for classification using support vector machine (SVM), naive Bayes (NB), decision tree (DT), and K-nearest neighbor (K-NN). In comparison with no feature selection and extraction, we found that our phase portrait method of feature selection and extraction had low computational costs and high robustness of 96–99% accuracy. Full article

Landing kinetics and kinematics have historically been correlated with potential injury. A factor that requires more attention associated with its correlation to injury risk includes the impact of physiological fatigue. Fatigue is a multifaceted phenomenon involving central and peripheral factors resulting in a slowing or cessation of motor unit firing and a decrease in maximal force and power. Sports participation rarely results in momentary muscular failure occurring, as many sports consist of intermittent periods of activity that are interspersed with short rest periods that allow for recovery to take place. However, over the course of the competition, fatigue can still accumulate and can result in impaired performance. Current literature on the topic struggles to replicate the peripheral and central metabolic stresses required to induce a state of fatigue that would be equivalent to athletic exposure. Furthermore, the current literature fails to demonstrate consistency regarding the kinetic implications associated with fatigue, which may be secondary to the inconsistencies associated with fatigue protocols utilized. This article focuses on providing an overview of the current literature associated with fatigue’s impact on the kinetics associated with landing from a jump. The article will provide a prospective methodology utilizing repeat bouts of the Wingate Anaerobic Power Test. The proposed protocol may help further our understanding of the relationship between fatigue and lower extremity biomechanics. Full article

Neurotrauma continues to contribute to significant mortality and disability. The need for better protective equipment is apparent. This review focuses on improved helmet design and the necessity for continued research. We start by highlighting current innovations in helmet design for sport and subsequent utilization in the lay community for construction. The current standards by sport and organization are summarized. We then address current standards within the military environment. The pathophysiology is discussed with emphasis on how helmets provide protection. As innovative designs emerge, protection against secondary injury becomes apparent. Much research is needed, but this focused paper is intended to serve as a catalyst for improvement in helmet design and implementation to provide more efficient and reliable neuroprotection across broad arenas. Full article

Much of our current understanding of age-related declines in mobility has been aided by decades of investigations on the role of muscle–tendon units spanning major lower extremity joints (e.g., hip, knee and ankle) for powering locomotion. Yet, mechanical contributions from foot structures are often neglected. This is despite the emerging evidence of their critical importance in youthful locomotion. With the rapid growth in the field of human foot biomechanics over the last decade, our theoretical knowledge of young asymptomatic feet has transformed, from long-held views of the foot as a stiff lever and a shock absorber to that of a versatile system that can modulate mechanical power and energy output to accommodate various locomotor task demands. In this perspective review, we predict that the next set of impactful discoveries related to locomotion in older adults will emerge by integrating the novel tools and approaches that are currently transforming the field of human foot biomechanics. By illuminating the functions of the feet in older adults, we envision that future investigations will refine our mechanistic understanding of mobility deficits affecting our aging population, which may ultimately inspire targeted interventions to rejuvenate the mechanics and energetics of locomotion. Full article