Spatial relationships among offender, knife, and victim during slashing attacks: implications for crime scene reconstruction.

BACKGROUND: The offender-victim spatial relationship is crucial in reconstructing a crime scene. The study aims to evaluate the spatial relationship of performing slashing attacks on a dummy using a Chinese kitchen knife, and thus to establish a scientific basis for crime scene reconstruction. METHODS: Twenty-four participants (12 males and 12 females) slashed a dummy's neck or chest using a kitchen knife, and the kinematic data were obtained using a three-dimensional motion capture system. The spatial relationships among offender, knife, and victim during slashing attacks were analyzed. RESULTS: Slashing distance and occupancy area are significantly influenced by gender (all P < 0.05), with males having higher values than females. Body parts significantly influence bevel angle, offender and victim azimuth angles, slashing distance, relative slashing distance, and occupancy area (all P < 0.01), with slashing the chest resulting in larger values than slashing the neck. CONCLUSION: Gender and body position significantly influence the spatial relationships of slashing action. Our data indicate that males stand farther away and occupy a larger area during slashing attacks. When the chest is slashed, the wound orientation is more diagonal, the offender's standing position and slashing distance are farther, and the occupancy area is larger compared to the neck. The findings could help identify the spatial relationships among offender, knife, and victim, providing a scientific basis for criminal investigations and court trials.

Validity of Actigraph for Measuring Energy Expenditure in Healthy Adults: A Systematic Review and Meta-Analysis.

PURPOSE: The objective of this systematic review and meta-analysis was to assess the validity of the Actigraph triaxial accelerometer device in measuring physical activity energy expenditure (PAEE) in healthy adults, with indirect calorimetry (IC) serving as the validity criterion. METHODS: A comprehensive search was conducted using the PubMed, Web of Science, and sportdiscuss databases, in addition to manual searches for supplementary sources. Search strategies were employed that involved conducting single keyword searches using the terms "gt3x" and "Actigraph gt3x". The literature search encompassed the timeframe spanning from 1 January 2010 to 1 March 2023. The methodological quality of the studies included in the analysis was evaluated using both the Downs and Black checklist and the Consensus-Based Criteria for Selection of Measurement Instruments (COSMIN) checklist. The meta-analysis was conducted using the Review Manager 5.4 software. The standardized mean difference (SMD) was calculated and expressed as a 95% confidence interval (CI). The significance level was set at α = 0.05. A systematic assessment of the Actigraph's performance was conducted through the descriptive analysis of computed effect sizes. RESULTS: A total of 4738 articles were retrieved from the initial search. After eliminating duplicate articles and excluding those deemed irrelevant, a comprehensive analysis was conducted on a total of 20 studies, encompassing a combined sample size of 1247 participants. The scores on the Downs and Black checklist ranged from 10 to 14, with a mean score of 11.35. The scores on the COSMIN checklist varied from 50% to 100%, with an average score of 65.83%. The meta-analysis findings revealed a small effect size (SMD = 0.01, 95% CI = 0.50-0.52, p = 0.97), indicating no statistically significant difference (p > 0.05). CONCLUSIONS: The meta-analysis revealed a small effect size when comparing the Actigraph and IC, suggesting that the Actigraph can be utilized for assessing total PAEE. Descriptive analyses have indicated that the Actigraph device has limited validity in accurately measuring energy expenditure during specific physical activities, such as high-intensity and low-intensity activities. Therefore, caution should be exercised when utilizing this device for such purposes. Furthermore, there was a significant correlation between the activity counts measured by the Actigraph and the PAEE, indicating that activity counts can be utilized as a predictive variable for PAEE.

Predicting vertical ground reaction force in rearfoot running: A wavelet neural network model and factor loading.

This study proposed a simple method for selecting input variables by factor loading and inputting these variables into a wavelet neural network (WNN) model to predict vertical ground reaction force (vGRF). The kinematic data and vGRF of 9 rearfoot strikers at 12, 14, and 16 km/h were collected using a motion capture system and an instrumented treadmill. The input variables were screened by factor loading and utilized to predict vGRF with the WNN. Nine kinematic variables were selected, corresponding to nine principal components, mainly focusing on the knee and ankle joints. The prediction results of vGRF were effective and accurate at different speeds, namely, the coefficient of multiple correlation (CMC) > 0.98 (0.984-0.988), the normalized root means square error (NRMSE) < 15% (9.34-11.51%). The NRMSEs of impact force (8.18-10.01%), active force (4.92-7.42%), and peak time (7.16-12.52%) were less than 15%. There was a small number (peak, 4.12-6.18%; time, 4.71-6.76%) exceeding the 95% confidence interval (CI) using the Bland-Altman method. The knee joint was the optimal location for estimating vGRF, followed by the ankle. There were high accuracy and agreement for predicting vGRF with the peak and peak time at 12, 14, and 16 km/h. Therefore, factor loading could be a valid method to screen kinematic variables in artificial neural networks.

Effects of Footwear Selection on Plantar Pressure and Neuromuscular Characteristics during Jump Rope Training.

This study examined what footwear type influenced plantar pressure and lower extremity muscle activations in jump rope training. Ten healthy physical-education graduate students participated in this study. The biomechanical parameters during the jump rope training were collected by an AMTI force platform, a Novel Pedar-X insole and a wireless electromyography (EMG) system. The results of the force platform indicate that vertical ground reaction force (vGRF) and contact time were much higher in the one-leg landing (both p = 0.001). The GRF, GRF (BW) and Lat MF pressure were significantly greater in the one-leg landing (p = 0.018, 0.013 and 0.027); the pressure of the Lat MF and H area were significantly greater in the volleyball shoe (p = 0.025, 0.031); the pressure of the Mid FF and Lat FF area were significantly greater in the jumping shoe (p = 0.005, 0.042). No significant difference in EMG was found between footwear and landing conditions. In summary, the running shoe and jumping shoe might be a better choice for people who exercise. However, the running shoe is recommended for people when both jumping and running are required.

Biomechanical characteristics of slashing attack on different body parts of a dummy using a kitchen knife.

BACKGROUND: Slashing attack is one of the most common ways of committing a homicide. The purpose of this study was to evaluate the biomechanical characteristics of slashing different body parts of a dummy by young males and females using a Chinese kitchen knife and thus provide scientific evidence for criminal investigations and court trials. METHODS: A total of 12 male and 12 female college students participated in this study. Biomechanical parameters, including joint velocity, slashing velocity, slashing force, energy, and impulse, were evaluated when slashing the chest and the neck of a dummy using a Chinese kitchen knife. RESULTS: When slashing the neck or the chest of a dummy, male participants showed higher elbow and wrist velocities (21.2% and 28.5%, respectively) as well as higher knife velocity (33.6%), slashing velocity (25.3%), slashing force (23.3%), and energy (57.6%) compared to female participants (all p < 0.05). When slashing the chest, participants showed higher shoulder, elbow, and wrist velocities (31.9%, 12.7%, and 12.6%) as well as knife velocity (3.8%), slashing velocity (7.3%), and energy (23.2%) compared to slashing the neck (all p < 0.05), regardless of gender. CONCLUSION: Both gender and slashing position have great impact on biomechanical characteristics of the slashing movement. Our data indicate that when slashing using a Chinese kitchen knife, males may induce severer wounds than females, and slashing different body parts may generate different slashing velocity or energy. Compared to slashing position, gender may have greater influence on the biomechanical characteristics. Findings from this study may expand our knowledge about knife slashing attacks by Chinese kitchen knives as well as other knives with comparative heavy blades.

Effects of Jump-Rope-Specific Footwear Selection on Lower Extremity Biomechanics.

Footwear is among the most important equipment in sports to decrease injuries and enhance performance during exercise. In this study, we investigated differences in lower extremity plantar pressure and muscle activations during jump rope activities. Ten participants performed jump rope under two landing conditions with different footwear. A force platform (AMTI, 1000 Hz), a Novel Pedar-X system (Nove, 100 Hz), and a wireless electromyography (EMG) system (Noraxon, 1500 Hz) were used to measure biomechanical parameters during the jump rope exercise. Vertical ground reaction forces (vGRF), plantar pressure, and lower extremity muscle activations were analyzed. One-leg landing resulted in a significantly greater vGRF and shorter fly time than two-leg landing (p < 0.05). A significantly higher peak pressure and lesser toe (LT) area pressure was shown with the jumping shoe (all p < 0.05), but lower plantar pressure resulted in the middle foot area (p < 0.05). The EMG results of tibialis anterior (TA) were significantly greater with one-leg landing (all p < 0.05) during the pre- and background activity (BGA) phases. The results suggest that plantar pressure distribution should be considered when deciding on footwear during jump rope exercises, but care should be taken with regards to recovery after repeated collisions and fatigue. The jumping shoe provides benefits in terms of decreased plantar pressure sustained during jump rope exercises.

Characteristics of the Distance and Space Required for Knife Slashing Using a Motion Capture System.

OBJECTIVES: To investigate the relationship between the perpetrator's sex, victim's position and slashing location as well as anthropometric parameters on distance and space required for slashing, to provide the theoretical basis for the judgment of whether the crime scene was consistent with the criminal activity space. METHODS: The kinematics data of 12 male and 12 female subjects slashing the neck of standing and supine mannequins as well as the chest of the standing mannequins with a kitchen knife were obtained by using a 3D motion capture system. The relationship between the perpetrator's sex-victim's position, the perpetrator's sex-slashing location, and anthropometric parameters and the distance and space required for the slashing were analyzed by two-factor repeated measures ANOVA and Pearson correlation analysis respectively. RESULTS: Compared with slashing the neck of supine mannequins, the distance (L) and normalized L (l) of slashing the neck of standing mannequins were greater, while vertical distance (LVR) and normalized LVR (lVR) of the knife side were smaller. Compared with slashing the neck of standing mannequins, the L and l slashing the chest of standing mannequins were greater, while LVR and lVR were smaller. Horizontal distance (LHR) and normalized LHR (lHR) of the knife side in males were greater than that in females. Height and arm length were positively correlated with L, LHR, and LVR when striking the standing mannequins. CONCLUSIONS: When slashing the neck of supine or standing victims, the slashing distance is shorter and the slashing height is greater. Furthermore, the distance and space required for slashing are correlate with anthropometric parameters.

Effects of Shoe Midsole Hardness on Lower Extremity Biomechanics during Jump Rope in Healthy Males.

This study investigated differences in lower extremity muscle activations and vertical stiffness during a 2.2 Hz jump rope exercise with different midsole hardnesses (45, 50, 55, and 60 Shores C). Twelve healthy male participants wore customized shoes with different hardness midsoles and performed jump rope exercises in a random order. A nine-camera motion analysis system (150 Hz), a force platform (1500 Hz), and a wireless electromyography (EMG) system (Noraxon, 1500 Hz) were used to measure the biomechanical parameters during the jump rope exercise. The biceps femoris %MVC of barefoot participants was significantly greater than that of those wearing the 45 Shores C (p = 0.048) and 55 Shores C (p = 0.009) midsole 100 ms before landing. The vastus medialis %MVC of barefoot participants was significantly greater than that of those wearing the 55 C midsole (p = 0.005). Nonsignificant differences in vertical stiffness were found between midsole hardnesses and barefoot. Lower extremity muscle activation differed between conditions. The results of this study indicate that for repetitive activities that entail multiple impacts, sports shoes with a low midsole hardness (e.g., 50 Shores C or 45 Shores C) may be appropriate. It is important to provide customers with information regarding midsole hardness in shoe product labeling so that they properly consider the function of the shoes.

Strategies of elite Chinese gymnasts in coping with landing impact from backward somersault.

This study aimed to investigate how elite Chinese gymnasts manage the landing impact from a backward somersault. Six international-level male gymnasts performed backward somersault tests with a synchronous collection of kinematics (250 Hz), ground reaction forces (1,000 Hz), and surface electromyography (EMG) (2,000 Hz). A 19-segment human model was developed and lower extremity joints torques were calculated by means of a computer simulation. The angles of the lower extremity joints initially extended and then flexed. These angular velocities of extension continued to decrease and the joint torques changed from extensor to flexor within 100 ms before touchdown. The angles of the hips, knees, and ankles flexed rapidly by 12°, 36°, and 29°, respectively, and the angular velocities of flexion, flexor torque, and EMG peaked sharply during the initial impact phase of the landing. The angles of the hips, knees, and ankles flexed at approximately 90°, 100°, and 80°, respectively. The torques were reversed with the extensor torques, showing a relatively high level of muscle activation during the terminal impact phase of the landing. The results showed that the international-level gymnasts first extended their lower extremity joints, then flexed just before touchdown. They continued flexing actively and rapidly in the initial impact phase and then extended to resist the landing impact and maintain body posture during the terminal impact phase of the landing. The information gained from this study could improve our understanding of the landings of elite gymnasts and assist in injury prevention.

The influence of landing mat composition on ankle injury risk during a gymnastic landing: a biomechanical quantification.

PURPOSE: About 70% injury of gymnasts happened during landing - an interaction between gymnast and landing mat. The most injured joint is the ankle. The current study examined the effect of mechanical properties of landing mat on ankle loading with aims to identify means of decreasing the risk of ankle injury. METHOD: Gymnastic skill - salto backward stretched with 3/2 twist was captured by two high-speed camcorders and digitized by using SIMI-Motion software. A subject-specific, 14-segment rigid-body model and a mechanical landing-mat model were built using BRG.LifeMODTM. The landings were simulated with varied landing-mat mechanical properties (i.e., stiffness, dampness and friction coefficients). RESULT: Real landing performance could be accurately reproduced by the model. The simulations revealed that the ankle angle was relatively sensitive to stiffness and dampness of the landing mat, the ankle loading rate increased 26% when the stiffness was increased by 30%, and the changing of dampness had notable effect on horizontal ground reaction force and foot velocity. Further, the peak joint-reaction force and joint torque were more sensitive to friction than to stiffness and dampness of landing mat. Finally, ankle muscles would dissipate about twice energy (189%) when the friction was increased by 30%. CONCLUSION: Loads to ankles during landing would increase as the stiffness and dampness of the landing mat increase. Yet, increasing friction would cause a substantial rise of the ankle internal loads. As such, the friction should be a key factor influencing the risk of injury. Unfortunately, this key factor has rarely attracted attention in practice.

Backward walking training improves balance in school-aged boys.

BACKGROUND: Falls remain a major cause of childhood morbidity and mortality. It is suggested that backward walking (BW) may offer some benefits especially in balance and motor control ability beyond those experienced through forward walking (FW), and may be a potential intervention for prevention of falls. The objective of this study was to investigate the effects of BW on balance in boys. METHODS: Sixteen healthy boys (age: 7.19 ± 0.40 y) were randomly assigned to either an experimental or a control group. The experimental group participated in a BW training program (12-week, 2 times weekly, and 25-min each time) but not the control group. Both groups had five dynamic balance assessments with a Biodex Stability System (anterior/posterior, medial/lateral, and overall balance index) before, during and after the training (week- 0, 4, 8, 12, 24). Six control and six experimental boys participated in a study comparing kinematics of lower limbs between FW and BW after the training (week-12). RESULTS: The balance of experimental group was better than that of control group after 8 weeks of training (P < 0.01), and was still better than that of control group (P < 0.05), when the BW training program had finished for 12 weeks. The kinematic analysis indicated that there was no difference between control and experimental groups in the kinematics of both FW and BW gaits after the BW training (P > 0.05). Compared to FW, the duration of stance phase of BW tended to be longer, while the swing phase, stride length, walking speed, and moving ranges of the thigh, calf and foot of BW decreased (P < 0.01). CONCLUSION: Backward walking training in school-aged boys can improve balance.

Model of depressed myocardium shows orthostatic intolerance with or without reduced blood volume.

INTRODUCTION: The development of orthostatic hypotension (OH) is complex and multi-factorial. Previous simulation work indicates that myocardial contractility depression (MCD) may increase OH when there is a total blood volume decrease. This paper hypothesized that MCD increased OH in both humans with and without decrease in blood volume. METHODS: A model, which was previously used to reproduce cardiovascular response to lower body negative pressure (LBNP), hypovolemia, and MCD, was modified by incorporating the physiologic mechanism of plasma filtration into the interstitium during LBNP. The model was evaluated by human experimental results. Using the model, HR and BP response to LBNP were simulated at conditions of 10%, 20%, and 30% MCD. Additionally, HR and BP response to LBNP were simulated at conditions of 10% and 20% MCD with a 12% decrease in blood volume. RESULTS: Simulation results indicate that the increments of HR and decrements of systolic BP (SBP) and mean arterial pressure (MAP) rise with the increases of MCD. Specifically, simulation results indicate that about 30% MCD would cause OH (HR: 117 bpm; SBP: 92 mmHg; MAP: 78 mmHg). It also indicates that about 20% MCD would cause OH (HR: 134 bpm, SBP: 84 mmHg, MAP: 73 mmHg) with a 12% decrease in total blood volume. CONCLUSION: It is suggested that MCD increases OH whether or not there is a total blood decrease, and further suggested that MCD induced by both spaceflight and heart disease may increase OH.

[Effects of simulated microgravity on cardiovascular function and counter effect of lower body negative pressure].

Studies on effect of simulated microgravity on cardiovascular function and counter effect of lower body negative pressure (LBNP) in recent years were summarized. The mechanism of simulated microgravity induced orthostatic intolerance may involve the reduction of cardiovascular function and cerebral blood flow, and endocrine changes. The significance of mathematical model in the study of mechanism of microgravity induced orthostatic intolerance was also discussed. The counter effect of LBNP was emphasized.

[The changes of cardiovascular response to orthostatic stress caused by hypovolemia induced by weightlessness: a simulation study].

We introduced the method of computer simulation in the studies of gravitational physiology. Based on work of Melchior (1994), we developed a mathematical model that can be used to stimulate cardiovascular responses to orthostatic stress (lower body negative pressure, LBNP). The model includes 7 sub-models: the redistribution of blood, the filling of left ventricle, left ventricle working, peripheral circulation, control of heart rate (HR), control of peripheral resistance and control of venous tone. Then we simulated the changes of blood pressure (BP) and heart rate during lower body negative pressure, and the results agreed well with the results of our human experiment. By using the developed model, we also simulated the effects of hypovolemia on the BP, HR and shock index during orthostatic stress. The simulation results indicate that the cardiovascular responses to orthostatic stress change significantly when the decrease of blood volume is more than 15% of the total blood volume. However, if the amount of the decrease of blood volume is less than 5% of the total blood volume, HR and BP could be maintained in normal range by the regulation of baroreflex during LBNP. Our simulation results suggest that hypovolemia may be the main cause of orthostatic intolerance induced by weightlessness.

Effect of lower body negative pressure against orthostatic intolerance induced by 21 days head-down tilt bed rest.

BACKGROUND: Exposure to actual or simulated weightlessness is known to induce orthostatic intolerance in humans. Many different methods have been suggested to counteract orthostatic hypotension. The repetitive or prolonged application of lower body negative pressure (LBNP) has shown beneficial effects to counter orthostatic intolerance, but devoting so much time to countermeasures is not compatible with space mission objectives or costs. The purpose of the present study was to assess the effects of brief LBNP sessions against orthostatic intolerance during a 21-d head-down tilt (HDT) bed rest. METHODS: There were 12 healthy male volunteers who were exposed to -6 degrees HDT bed rest for 21 d. Six subjects received -30 mm Hg LBNP sessions for 1 h x d(-1) from day 15 to day 21 of the HDT, and six others served as control. Orthostatic tolerance was assessed by means of standard tilt test. RESULTS: Before HDT, all the subjects in the two groups completed the tilt tests. After 21 d of HDT, five subjects of the control group and one subject of the LBNP group could not complete the tilt test due to presyncopal or syncopal symptoms. The mean upright time in the control group 13.0 +/- 4.0 min) was significantly shorter (p < 0.05) than that in the LBNP group (19.0 +/- 2.2 min). Body weight decreased significantly in the control group during HDT, while increasing significantly on day 21 of HDT in the LBNP group. Urine volume increased on days 15-21 of HDT in the control group, but remained unchanged throughout HDT in the LBNP group. A significant decrease in cardiac output and cardiac index, and a significant increase in total peripheral resistance, pre-ejection period, plasma renin activity, aldosterone, and prostaglandin 12 were observed during HDT in both groups. There were no significant differences in these parameters between the two groups. CONCLUSIONS: Brief daily LBNP sessions were effective in preventing orthostatic intolerance induced by 21 d HDT bed rest. However, it did not improve cardiac pump and systolic functions and did not preserve volume regulating hormones.

Experimental study on hemorheological and pathological changes following severe myocardial contusion.

OBJECTIVE: To investigate the mechanism of severe myocardial contusion in rabbits. METHODS: A total of 32 New Zealand rabbits were randomly divided into 2 groups, the severe myocardial contusion group (the experimental group, n=16) and the sham-impact control group (the control group, n=16). Hemorheological parameters, interleukin-8 (IL-8) in serum, the water contents of myocardium and polymorphonuclear neutrophil (PMN) infiltration in contused myocardium were observed at 24 hours after the experiment. RESULTS: As compared with the control group, the hemorheological parameters in the experimental group including the whole blood viscosity (etab), erythrocyte aggregation index (EAI), hematocrit (HCT), serum fibrinogen (Fib), Casson viscosity (Gammay) and erythrocyte sedimentation rate (ESR), significantly increased. The IL-8, PMN infiltration and the water contents of the contused myocardium also significantly increased. CONCLUSIONS: It suggests that the hemorheological disorder, increase of IL-8 in serum, and PMN infiltration in contused myocardium may contribute to the development of cardiac edema and secondary myocardial damage following severe myocardial contusion in rabbits.