Higher Ground Reaction Forces Research Articles

Comparative Analysis of Kinetic Responses and Injury Risk During Landing from 45 cm Height: A Study of Barefoot vs. Sports Shoes Conditions

Jumping and landing biomechanics are closely related to the risk of acute injury due to prolonged exposure to high-ground reaction forces in basketball-like sports, which can lead to lower-limb musculoskeletal injuries in the hip, knee, and ankle. Footwear greatly impacts jumping mechanics, but going barefoot provides a unique perspective on how the human body interacts with the ground. This study aims to find out the kinetic responses during drop landing from 45 cm height with and without sports shoe conditions. Twenty-five healthy young adults were volunteers for this study. Kinetic parameters were recorded and processed by using Quattro Jump force plat and Mars Quarter performance analysis software. Data were presented as mean ± SD values and statistical analysis was performed using statistical software package SPSS-26. The drop landing data of with and without shoe shows scattered parameters with maximum forces of 4706.12N and 5393.04N at 45 cm height, indicating a 66% and 75% risk of metatarsal injury. The stabilization force was 632.64N and 623.64N at 45 cm, reached at 0.58s and 0.66s respectively. Time from Max Force to MFBS Regression analysis indicated a low R-squared value and a random fit plot. In barefoot (without shoe) conditions, the initial contact force, and maximum force were 85.71% and 13.60% higher (250N and 5393.04N respectively) compared to landing with shoes (100N and 4706.12N). However, the stabilization force was higher (632.64N) when landing with shoes compared to landing barefoot (623.64N). As a result, the risk of musculoskeletal injuries and joint stress was higher when landing barefoot due to the higher initial contact force and maximum force. On the other hand, landing with shoes enhances balance and stability due to the higher stabilization force.

Gait analysis of male professional boxers

Introduction: Gait plays a crucial role in both daily life and sports performance. This study analyzes professional boxers’ gait, as it is essential to understand its influence on performance and injury risk. However, there is a need to comprehend the effects of boxing training on gait and the occurrence of asymmetries between limbs. Research Question: Does the gait of professional boxers exhibit significant differences between limbs, and what are the potential implications of this asymmetry? Materials and Methods: The study involved 36 professional boxers, and the Gaitway 3D Pressure treadmill was used to collect data. The analysis was performed using statistical tests with a pre-determined level of significance. Results: Significant differences were found between limbs in gait phase parameters and ground reaction forces. A longer swing phase of the right leg was observed, potentially affecting the reduction of single-limb support and right-leg propulsion. Additionally, higher ground reaction forces were noted on the left side. Conclusions: This analysis of gait in professional boxers provides valuable insights into the asymmetry between limbs, which may impact performance and injury risk. It also shows the correct characteristics of selected gait parameters. These findings are relevant for tailoring training programs, reducing injuries, and enhancing overall physical conditioning of athletes. Further-more, they can be applied in both sports and daily life for injury prevention and rehabilitation, where maintaining balance and stability are crucial in avoiding injuries and improving the quality of life.

Controlling jumps through latches in small jumping robots

Small jumping robots can use springs to maximize jump performance, but they are typically not able to control the height of each jump owing to design constraints. This study explores the use of the jumper’s latch, the component that mediates the release of energy stored in the spring, as a tool for controlling jumps. A reduced-order model that considers the dynamics of the actuator pulling the latch and the effect of spring force on the latch is presented. This model is then validated using high speed video and ground reaction force measurements from a 4g jumper. Both the model and experimental results demonstrate that jump performance in small insect-inspired resource-constrained robots can be tuned to a range of outputs using latch mediation, despite starting with a fixed spring potential energy. For a fixed set of input voltages to the latch actuator, the results also show that a jumper with a larger latch radius has greater tunability. However, this greater tunability comes with a trade-off in maximum performance. Finally, we define a new metric, ‘Tunability Range,’ to capture the range of controllable jump behaviors that a jumper with a fixed spring compression can attain given a set of control inputs (i.e. latch actuation voltage) to choose from.

Newly compiled Tai Chi (Bafa Wubu) promotes lower extremity exercise: a preliminary cross sectional study.

Tai Chi (Bafa Wubu) is a new type of simplified Tai Chi widely practiced by Tai Chi enthusiasts that has developed and perfected simplified Tai Chi movement and enriched Tai Chi practice methods. When practicing, Tai Chi athletes and enthusiasts can choose the Bafa Wubu movements to practice according to their physical conditions. The purpose of this article is to discuss the mechanism by which Bafa Wubu promotes lower extremity exercise from the perspective of exercise biomechanics. This article aims to explore the scientific training methods and technical characteristics of Bafa Wubu, and its contribution to comprehensive exercise of the lower extremities, by analyzing the biomechanical characteristics of the lower extremities of participants who practice Bafa Wubu at different levels and by comparing their ground reaction force, lower limb joints, and muscles during Bafa Wubu. A total of 16 male participants were recruited and divided into an amateur group (N = 8) and a professional group (N = 8). The data were collected by a BTS 3D infrared-based motion capture system, and Kistler 3D force plate. The lower extremity joint forces and muscle strength were calculated by anybody simulation software with inverse dynamics. During elbowing and leaning sideways with steps sideways (ELS), the ground reaction force of the professional group was significantly higher than that of the amateur group in the sagittal, vertical, and frontal axes (P < 0.01). While stepping forward, backward, and sideways, the professional group's joints loading at the hip, knee, and ankle was always higher in the vertical direction (P < 0.01). Furthermore, during warding off with steps forward (WOF), laying with steps forward (LF), and rolling back with steps backward (RBB), hip joint loading increased in the med-lat direction. During actions with steps backward and sideways, the professional group's ankle flexion/extension torque and hip abduction/rotation torque were significantly larger than those of the amateur group (P < 0.01). Different actions in Bafa Wubu activate muscles to different degrees, whereas the iliacus is mainly responsible for stabilizing postures when practitioners perform standing knee lifting motions. Professional groups who have been practicing Tai Chi (Bafa Wubu) for a long time have higher ground reaction force, and the force on the three joints of the lower extremities is different for various movements, which has positive significance for exercising the joints of the lower extremities. In addition, various motions activate muscles of different types at different levels. For amateurs to practice different movements to stimulate the muscles, targeted areas of practice promote the lower extremity muscles' synergistic force. In summary, the muscles and joints of the lower extremity can obtain comprehensive and balanced exercise through Bafa Wubu.

Blood python (Python brongersmai) strike kinematics and forces are robust to variations in substrate geometry.

Snake strikes are some of the most rapid accelerations in terrestrial vertebrates. Generating rapid body accelerations requires high ground reaction forces, but on flat surfaces snakes must rely on static friction to prevent slip. We hypothesize that snakes may be able to take advantage of structures in the environment to prevent their body from slipping, potentially allowing them to generate faster and more forceful strikes. To test this hypothesis, we captured high-speed video and forces from defensive strikes of juvenile blood pythons (Python brongersmai) on a platform that was either open on all sides or with two adjacent walls opposite the direction of the strike. Contrary to our predictions, snakes maintained high performance on open platforms by imparting rearward momentum to the posterior body and tail. This compensatory behavior increases robustness to changes in their strike conditions and could allow them to exploit variable environments.

Sclerostin as a biomarker of physical exercise in osteoporosis: A narrative review.

Osteoporosis, a disease of low bone mass, is characterized by reduced bone mineral density (BMD) through abnormalities in the microarchitecture of bone tissue. It affects both the social and economic areas, therefore it has been considered a lifestyle disease for many years. Bone tissue is a dynamic structure exhibiting sensitivity to various stimuli, including mechanical ones, which are a regulator of tissue sclerostin levels. Sclerostin is a protein involved in bone remodeling, showing an anti-anabolic effect on bone density. Moderate to vigorous physical activity inhibits secretion of this protein and promotes increased bone mineral density. Appropriate exercise has been shown to have an osteogenic effect. The effectiveness of osteogenic training depends on the type, intensity, regularity and frequency of exercise and the number of body parts involved. The greatest osteogenic activity is demonstrated by exercises affecting bone with high ground reaction forces (GRF) and high forces exerted by contracting muscles (JFR). The purpose of this study was to review the literature for the effects of various forms of exercise on sclerostin secretion.

Which typical floor movements of men’s artistic gymnastics result in the most extreme lumbar lordosis and ground reaction forces?

ABSTRACT Back pain is prevalent among gymnast populations and extreme flexion or extension of the lumbar spine along with high ground reaction forces (GRFs) are known to increase intervertebral stress. The aim of this study was to determine which postures and dynamic conditions among common floor movements provide the greatest risk of injury in men’s artistic gymnastics (MAG). For this purpose, lumbar spine curvatures, obtained through a full-body subject-specific kinematic model fed by motion capture data, and GRFs on feet and hands were compared between typical floor movements of MAG (pike jump, round off back handspring, front handspring, forward and backward tucked somersaults) performed by six adolescent gymnasts. The round off back handspring and the pike jump resulted respectively in the largest lumbar extension and flexion, and the forward tucked somersault take-off in the highest GRF. At ground impacts, the largest lumbar flexion was during the backward tucked somersault landing and only the back handspring hands ground contact phase led to lumbar extension. Such identification of high-risk conditions should enable better back pain management in gymnastics through more tailored training adaptations, particularly in case of pathologies or musculoskeletal specificities.

Metatarsal fusion resisted bending as jerboas (Dipodidae) transitioned from quadrupedal to bipedal.

Hind limbs undergo dramatic changes in loading conditions during the transition from quadrupedal to bipedal locomotion. For example, the most early diverging bipedal jerboas (Rodentia: Dipodidae) are some of the smallest mammals in the world, with body masses that range between 2–4 g. The larger jerboa species exhibit developmental and evolutionary fusion of the central three metatarsals into a single cannon bone. We hypothesize that small body size and metatarsal fusion are mechanisms to maintain the safety factor of the hind limb bones despite the higher ground reaction forces associated with bipedal locomotion. Using finite-element analysis to model collisions between the substrate and the metatarsals, we found that body size reduction was insufficient to reduce bone stress on unfused metatarsals, based on the scaled dynamics of larger jerboas, and that fused bones developed lower stresses than unfused bones when all metatarsals are scaled to the same size and loading conditions. Based on these results, we conclude that fusion reinforces larger jerboa metatarsals against high ground reaction forces. Because smaller jerboas with unfused metatarsals develop higher peak stresses in response to loading conditions scaled from larger jerboas, we hypothesize that smaller jerboas use alternative dynamics of bipedal locomotion to reduce the impact of collisions between the foot and substrate.

Effects of Leg Stiffness Regulated by Different Landing Styles on Vertical Drop Jump Performance.

The purpose of this study was to investigate the effects of stiffness regulated by landing styles on drop jump performance. Twenty-four male lacrosse athletes performed drop jumps with stiff (ST), self-selected (SS), and soft (SF) landing from a 0.42 m box. Leg stiffness, ground contact time, depth, jump height, maximum ground reaction force (GRF), GRF at the start of the propulsive phase, mean power, peak power, and the reactive strength index (RSI) were calculated. The results showed that jump height and the RSI had strong correlations to power production in all drop jump styles. Power would be a key factor to overall athletic performance. Repeated measures ANOVA showed significant differences (p < 0.05) in all variables among the three styles. Drop jumps with SS landing had comparable jump height to drop jumps with SF landing and power output to drop jumps with ST landing. Drop jumps with ST landing had significantly lower jump height, but higher GRF, power, and the RSI compared to drop jumps with SF landing. In drop jump testing, drop jumps with SS landing should be used if power and jump height were the major concerns; if the RSI was the major concern, drop jumps with ST landing should be used. Training with drop jumps, one of the main objectives should be increasing power output due to its significant correlation to jump height and the RSI in all conditions.

Muscle Strength And Loading Patterns During Sport-related Tasks In Persons With Acetabular Dysplasia

PURPOSE: Acetabular dysplasia (AD) is described as insufficient bony coverage of the femoral head by the acetabulum that leads to joint instability, pain, and decreased function. Little is known regarding the effects of AD on muscle strength and loading patterns during sport-related tasks. We compared muscle strength and loading patterns during squat and countermovement jump (CMJ) tasks between limbs and examined associations among these variables in persons with AD. METHOD: We enrolled 12 persons with AD (11 females) and evaluated isometric strength of the knee flexors and extensors and the hip flexors, extensors, and abductors using an electromechanical dynamometer (Biodex 3). We used peak torque values (Nm/kg) for the involved and uninvolved limbs to calculate limb symmetry indices (LSI) for each muscle group. Loading patterns during a squat and CMJ takeoff and landing were evaluated using two portable force plates (ForceDecks). Average peak ground-reaction force (GRF) for the involved and uninvolved limbs (N/N) and LSI for each task were calculated. We used Wilcoxon signed-rank test to evaluate differences in muscle strength and loading patterns between limbs. We examined associations between involved limb muscle strength and loading patterns using Spearman’s rho test. RESULT: The involved limb exhibited lower knee extensor strength compared to the uninvolved limb (involved = 1.75 Nm/Kg; uninvolved = 2.11 Nm/Kg; p = 0.005). There were no other differences between limbs for the remaining muscle strength variables or for squat and CMJ loading patterns variables (all p > 0.05). Per muscle group, the following proportions exhibited ≥90% LSI: 41.7% for knee extensors and flexors and hip flexors; 66.7% for hip extensors; 90% for hip abductors. Per movement task, the following proportions exhibited ≥90% LSI: 72.7% for the squat; 90% for CMJ takeoff; 54.5% for CMJ landing. Higher hip extensor strength was associated with higher GRF during CMJ landing for involved limb (r = 0.70; p = 0.016). CONCLUSION: Persons with AD exhibited decreased involved limb knee extensor strength and asymmetric strength and loading patterns. Higher hip strength was associated with higher involved limb landing during CMJ. Further study of the associations among strength and joint loading patterns is needed in larger samples of persons with AD.

Investigating the biomechanical validity of the V-spine angle technique in cricket fast bowling

The effective utilisation of braking ground reaction forces is considered an essential biomechanical characteristic of fast bowling in cricket. The configuration of the trunk and legs during the delivery stride phase has been hypothesised to increase braking forces, causing the upper body segments to increase their angular momentum and thereby increase ball release speed. This study investigated the relationship between V-spine angle, front shank angle (plant angle) and front knee angle with braking ground reaction forces and ball release speed. Three-dimensional kinematic and kinetic analyses were performed for 17 male pace bowlers (17.2 ± 1.7 years) of New South Wales grade club level using data from a Cortex 2.0 motion analysis system (200 Hz) and Kistler force plates (1000 Hz). V-spine angle was strongly and significantly correlated with braking ground reaction force (r = −0.691), plant angle (r = −0.806) and front knee angle (r = −0.606). In addition, stepwise multiple linear regression analysis revealed that front shank angle was the strongest predictor of braking ground reaction force. The data suggests that V-spine angle and plant angle may play an important role in generating high braking ground reaction forces in bowling, with the front knee angle possibly playing a supporting role. Coaches may need to consider these findings when assessing the techniques of pace bowlers.

Effects of step frequency during running on the magnitude and symmetry of ground reaction forces in individuals with a transfemoral amputation

BackgroundIndividuals with unilateral transfemoral amputation are prone to developing health conditions such as knee osteoarthritis, caused by additional loading on the intact limb. Such individuals who can run again may be at higher risk due to higher ground reaction forces (GRFs) as well as asymmetric gait patterns. The two aims of this study were to investigate manipulating step frequency as a method to reduce GRFs and its effect on asymmetric gait patterns in individuals with unilateral transfemoral amputation while running.MethodsThis is a cross-sectional study. Nine experienced track and field athletes with unilateral transfemoral amputation were recruited for this study. After calculation of each participant’s preferred step frequency, each individual ran on an instrumented treadmill for 20 s at nine different metronome frequencies ranging from − 20% to + 20% of the preferred frequency in increments of 5% with the help of a metronome. From the data collected, spatiotemporal parameters, three components of peak GRFs, and the components of GRF impulses were computed. The asymmetry ratio of all parameters was also calculated. Statistical analyses of all data were conducted with appropriate tools based on normality analysis to investigate the main effects of step frequency. For parameters with significant main effects, linear regression analyses were further conducted for each limb.ResultsSignificant main effects of step frequency were found in multiple parameters (P < 0.01). Both peak GRF and GRF impulse parameters that demonstrated significant main effects tended towards decreasing magnitude with increasing step frequency. Peak vertical GRF in particular demonstrated the most symmetric values between the limbs from − 5% to 0% metronome frequency. All parameters that demonstrated significant effects in asymmetry ratio became more asymmetric with increasing step frequency.ConclusionsFor runners with a unilateral transfemoral amputation, increasing step frequency is a viable method to decrease the magnitude of GRFs. However, with the increase of step frequency, further asymmetry in gait is observed. The relationships between step frequency, GRFs, and the asymmetry ratio in gait may provide insight into the training of runners with unilateral transfemoral amputation for the prevention of injury.

Association between biological maturation and anterior cruciate ligament injury risk factors during cutting.

Adolescent females are particularly susceptible to suffering anterior cruciate ligament (ACL) injuries, likely influenced by well-established maturational changes. This study investigated ACL biomechanical injury risk factors and their association with biological maturation in females. Thirty-five adolescent females (15±1 year) completed a series of maximum-effort 90° unanticipated cutting maneuvers. Established biomechanical ACL injury risk factors (including external knee abduction moments, knee abduction, hip abduction, knee flexion, ground reaction force) were derived from an optoelectronic motion analysis system and force platforms, with inter-limb asymmetries in these risk factors also computed. Biological maturation (percentage of predicted adult stature) was assessed using validated regression equations, incorporating anthropometric measures of participants and their biological parents. Significant bilateral asymmetries were observed with higher peak external knee abduction moments, higher ground reaction forces and less knee flexion (from 0-18% and 30-39% of contact) during the non-dominant vs. dominant cuts (effect sizes =0.36, 0.63 and 0.50, respectively). Maturation did not appear to influence these asymmetries; however, less hip abduction was observed (e.g., 21-51% of contact for dominant cuts) in more biologically-mature females. These results highlight a potential maturation-related change in cutting technique that may explain the apparent heightened ACL injury risk in this population. As females mature, training targeted at neuromuscular control of hip abductor (e.g. gluteal) muscle groups could potentially mitigate ACL injury risk.

Validation of the wearable sensor system - MoveSole® smart insoles

Biomechanical analysis of gait is commonly used in physiotherapy. Ground reaction forces during phases of gait is one element of kinetic analysis. In this article, we analyze if the MoveSole® smart insole is valid and accurate equipment for measuring ground reaction forces in clinical physiotherapy. MoveSole® StepLab is a mobile measurement system for instant underfoot force measurements during gait. Unique electromagnetic film (EMFI) based sensor technology and printed electronics production technology is integrated in the MoveSole® StepLab measurement system. The MoveSole® StepLab measures plantar ground reaction force distribution over the sensors and provides an estimation of the maximum total ground reaction force. We developed a two phase validation process to extract relevant parameters and compared the results to a Kistler force plate using the BioWare® analyzing program as a reference method. Our results show that MoveSole® smart insoles reach the strong level of accuracy needed in clinical work concerning highest ground reaction forces during step (Pearson correlation .822 - .875). The correlation of the time when the maximum ground reaction force occurred was moderate, e.g. during heel strike or toe-off (Pearson correlation natural gait speed .351 - .462, maximum gait speed .430). Our conclusion is that MoveSole® smart insoles are a potential tool for analyzing and monitoring gait ground reaction forces during physiotherapy processes.

Design and Evaluation of Torque Compensation Controllers for a Lower Extremity Exoskeleton.

In this article, we present an integrated human-in-the-loop simulation paradigm for the design and evaluation of a lower extremity exoskeleton that is elastically strapped onto human lower limbs. The exoskeleton has three rotational DOFs on each side and weighs 23 kg. Two torque compensation controllers of the exoskeleton are introduced, aiming to minimize interference and maximize assistance, respectively. Their effects on the wearer's biomechanical loadings are studied with a running motion and predicted ground reaction forces (GRFs). It is found that the added weight of the passive exoskeleton substantially increases the wearer's musculoskeletal loadings. The maximizing assistance controller reduces the knee joint torque by 31% when compared with the normal running (without exoskeleton) and by 50% when compared with the passive exoskeleton case. When compared with the normal running, this controller also reduces the hip flexion and extension torques by 31% and 38%, respectively. As a result, the peak activations of the biceps short head, gluteus maximus, and rectus femoris muscles are reduced by more than a half. Nonetheless, the axial knee joint reaction force increases for all exoskeleton cases due to the added weight and higher ground reaction forces. In summary, the results provide sound evidence of the efficacy of the proposed controllers on reducing the wearer's musculoskeletal loadings. And it is shown that the human-in-the-loop simulation paradigm presented here can be used for virtual design and evaluation of powered exoskeletons and pave the way for building optimized exoskeleton prototypes for experimental evaluation.

Biomechanical Determinants Of Return To Sport Following Anterior Cruciate Ligament Reconstruction

The ability to return to sport (RTS) after an anterior cruciate ligament reconstruction (ACLR) return to sport is due to many factors. To date, few studies have considered the role of poor biomechanics to predict RTS status. Potentially, higher ground reaction forces (GRF) and better frontal plane knee alignment at a 6 month follow up, may indicate an athlete who is able to return to sport at their pre-injury level. However, this has never been formally tested. Purpose: To determine the biomechanical factors at six months that predict return to sport at pre-injury level following ACLR. Methods: 21 subjects, (13 F, 20.1 ± 5.9 years, 22.3 ± 2.1 BMI, Pre-injury Tegner 8.1 ± 2.1 ) six months (190.6 ± 15.3 days) following ACLR, ran on an instrumented treadmill during three-dimensional assessment. Visual 3D was used to analyze peak GRF, impact peak, and frontal plane knee angle. Subjects were contacted at 4.5 ± 2.1 years post-surgery to answer a questionnaire regarding RTS. Logistic regression model selection was performed using the Feasible Solutions Algorithm with AIC as a criterion. p-values presented here are based on the main effect significance tests from the selected model. Results: Of the 21 subjects, 62% returned to sport at their pre-injury level. Subjects who returned to sport had significantly higher peak GRF (RTS 2.1 ± 0.24 BW, No RTS 1.98 ± 0.18 BW, p=0.03), impact peak (RTS 1.6 ± 0.3 BW, No RTS 1.4 ± 0.16 BW, p=0.04), and maximum frontal plane knee angle (RTS 5.2 ± 3.0o, No RTS 3.3 ± 3.3o, p=0.04). Conclusion: This data indicates that athletes who run with greater axial loading and whose knee is in a more adducted position are more likely to RTS at pre-injury level. We speculate that athletes who land with greater impact forces are more confident in their knee function and, thus, are more likely to return to sport. In addition, positioning the knee in more adduction may help the athlete feel more secure in their knee and, consequently, return to playing sport. Rehabilitation efforts should focus greater impact loading and improved frontal plane alignment of the knee during running to increase the likelihood of RTS at pre-injury level.

Effect of rocker-sole footwear on knee joint biomechanics while walking in people with ACL-reconstructed knees: a cross-sectional biomechanical study

Background: Reinjury has occurred at a high rate after anterior cruciate ligament (ACL) reconstruction. Low knee flexion angles and high peak posterior ground reaction forces in landing tasks increase ACL loading. Some studies reported that rocker-sole shoes increased knee flexion angle in the early stance phase of the gait. The aim of this study was to investigate the biomechanics of walking with a custom-made heel-to-toe rocker shoe design, with special attention to the sagittal knee joint kinematics of patients after ACL reconstruction. Methods: This study examined 10 male participants with ACL-reconstruction participants. Three-dimensional gait analysis was performed under two conditions of level walking that were tested in random order using either modified footwear adapted with a heel-to-toe rocker sole or baseline footwear with a flat sole. The knee flexion angle at initial foot contact with the ground, average knee flexion angle from heel strike to 25% stance phase, and first peak knee flexion angle were compared across footwear conditions. Results: Walking with the heel-to-toe rocker shoes increased the knee flexion angle at the early stance phase of the gait cycle when compared with the baseline footwear. Conclusions: Rocker-shoe intervention was found to have potential as a rehabilitation tool to modify gait patterns in the sagittal plane of people with ACL-reconstructed knees and may protect against high reinjury rates. Further research is required to evaluate whether prolonged wear of rocker-sole shoes can modify lower extremity biomechanics of participants who have undergone ACL reconstruction. Level of Evidence: Level II.

The effect of biological maturity status on ground reaction force production during sprinting.

Sprint ability develops nonlinearly across childhood and adolescence. However, the underpinning ground reaction force (GRF) production is not fully understood. This study aimed to uncover the kinetic factors that explain these maturation-related sprint performance differences in Japanese boys and girls. A total of 153 untrained schoolchildren (80 boys, 73 girls) performed two 50-m maximal effort sprints over a 52-force-platform system embedded in an indoor track. Maturity offset (years from peak height velocity; PHV) was estimated using anthropometric data and used to categorise the children into six-year-long maturation groups (from group 1 [5.5-4.5years before PHV] to group 6 [0.5years before to 0.5years after PHV). Maximum and mean step-averaged velocities across 26 steps were compared across consecutive maturation groups, with further GRF analysis (means and waveforms [statistical parametric mapping]) performed when velocity differences were observed. For boys, higher maximum velocities (effect size±90% CI=1.63±0.69) were observed in maturation group 2 (4.5-3.5years before PHV) compared to group 1 (5.5-4.5years before PHV), primarily attributable to higher antero-posterior GRFs across shorter ground contacts. Maximum velocities increased from maturation group 4 (2.5-1.5years before PHV) to group 5 (1.5-0.5years before PHV) in the girls (effect size±90% CI=1.00±0.78), due to longer ground contacts rather than higher GRFs per se. Waveform analyses revealed more effective reversal of braking forces and higher propulsive forces (e.g. 14%-77% of stance 4), particularly for comparisons involving boys, which suggested potentially enhanced stretch-shortening ability. Youth sport practitioners should consider these maturation-specific alterations when evaluating young athletes' sprint abilities.

The Effect of Breathing Pattern and Heel Strike Pattern on Peak Ground Reaction Force at Initial Contact During Walking

It has been proposed that during running, the greatest force occurs when the foot strikes the ground and simultaneously exhalation occurs at initial heel contact. As a result, breathing retraining has been used as a method to prevent lower extremity overuse injuries by modifying an individual's breathing pattern and consequently, reducing ground reaction forces. There is, however, little research exploring this link during walking. This study explored the interaction effect between the phase of respiration and foot strike pattern on measures of ground reaction forces while walking. The study also examined the correlation between the phase of respiration and peak forces. The research findings did not support the concept of breathing synchronization with higher ground reaction forces when exhalation occurred at heel strike during walking. The biomechanics of walking are very different than running and, therefore, the utility of breathing retraining may not be supported as has been proposed for running.

Effect of prosthetic alignment on gait and biomechanical loading in individuals with transfemoral amputation: A preliminary study

BackgroundInappropriate biomechanical loading usually leads to a high incidence of hip and knee osteoarthritis (OA) in individuals with lower-limb amputation, and prosthetic alignment may be an important influencing factor. The effect of alignment on the lower limb loading remains quantitatively unclear, and the relationship between malalignment and joint diseases is undefined. Research questionHow does alignment affect spatiotemporal gait parameters and ground reaction force (GRF) in individuals with transfemoral amputation? MethodsGait tests of 10 individuals with transfemoral amputation were performed with recommended alignment and eight malalignments, including 10 mm socket translation (anterior, posterior, medial, and lateral) and 6° socket angular changes (flexion, extension, abduction, and adduction). Fifteen individuals without amputation were recruited as a control group. The differences in spatiotemporal and GRF parameters under different alignments were analyzed and compared with those of the control group. Statistical analyses were performed by one-way ANOVA, repeated measure multivariate ANOVA, and paired t tests. ResultsThe medial GRF peaks and impulse on both sides and load rate on the intact side are significantly higher than those of the control group (P < 0.0056). The propulsive and braking peaks, vertical impulse, and medial and vertical load rates of GRF on the intact side are higher than those on the residual side (P < 0.05). The alignment of socket adduction significantly increases medial GRF peak and impulse on both sides (P < 0.0056). SignificanceAlignments exert remarkable and complicated effects on the biomechanical performance. The considerably higher GRF on the intact side of the individuals with transfemoral amputation may lead to internal stress changes of the intact joint, which may be an inducement for high incidence of joint diseases. Probably due to the increased lateral deviation of the center of gravity, the socket adduction alignment significantly increases medial GRF, which may lead to an increased risk of knee OA.