Instantaneous Load Research Articles

Simplified Method for Consolidation Settlement Calculation of Combined Composite Foundation

Treating weak saturated soil foundation by drainage powder jetting pile foundation can not only increase the bearing capacity of the foundation but also accelerate the drainage and consolidation process of the foundation. Having been commonly used in engineering, the plum blossom pile layout scheme is based on the foundation axisymmetric consolidation model (the powder jetting pile is the model center and the drainage board is located at the outer boundary of the model). It adopts reasonable boundary conditions and foundation seepage conditions and the method of pile-soil composite modulus and obtains the expression of the average excess pore water pressure of the composite foundation of the instantaneous loading of the drainage powder jetting pile under the simplified model. Therefore, the average consolidation degree of the foundation is acquired. The expression of the average consolidation degree can comprehensively reflect factors such as pile-soil modulus ratio, displacement ratio, drain spacing ratio, and those which affect the consolidation process of the foundation. The obtained analytical solution is of certain practical application significance for the consolidation settlement calculation of such engineering.

Leg Stiffness and Vertical Stiffness of Habitual Forefoot and Rearfoot Strikers during Running.

Foot strike patterns influence the running efficiency and may be an injury risk. However, differences in the leg stiffness between runners with habitual forefoot (hFFS) and habitual rearfoot (hRFS) strike patterns remain unclear. This study aimed at determining the differences in the stiffness, associated loading rate, and kinematic performance between runners with hFFS and hRFS during running. Kinematic and kinetic data were collected amongst 39 runners with hFFS and 39 runners with hRFS running at speed of 3.3 m/s, leg stiffness (Kleg), and vertical stiffness (Kvert), and impact loads were calculated. Results found that runners with hFFS had greater Kleg (P = 0.010, Cohen′s d = 0.60), greater peak vertical ground reaction force (vGRF) (P = 0.040, Cohen′s d = 0.47), shorter contact time(tc) (P < 0.001, Cohen′s d = 0.85), and smaller maximum leg compression (ΔL ) (P = 0.002, Cohen′s d = 0.72) compared with their hRFS counterparts. Runners with hFFS had lower impact peak (IP) (P < 0.001, Cohen′s d = 1.65), vertical average loading rate (VALR) (P < 0.001, Cohen′s d = 1.20), and vertical instantaneous loading rate (VILR) (P < 0.001, Cohen′s d = 1.14) compared with runners with hRFS. Runners with hFFS landed with a plantar flexed ankle, whereas runners with hRFS landed with a dorsiflexed ankle (P < 0.001, Cohen′s d = 3.35). Runners with hFFS also exhibited more flexed hip (P = 0.020, Cohen′s d = 0.61) and knee (P < 0.001, Cohen′s d = 1.15) than runners with hRFS at initial contact. These results might indicate that runners with hFFS were associated with better running economy through the transmission of elastic energy.

Association Between Knee- and Hip-Extensor Strength and Running-Related Injury Biomechanics in Collegiate Distance Runners.

Running-related injuries are common in distance runners. Strength training is used for performance enhancement and injury prevention. However, the association between maximal strength and distance-running biomechanics is unclear. To determine the relationship between maximal knee- and hip-extensor strength and running biomechanics previously associated with injury risk. Cross-sectional study. Research laboratory. A total of 36 collegiate distance runners (26 men, 10 women; age = 20.0 ± 1.5 years, height = 1.74 ± 0.09 m, mass = 61.97 ± 8.26 kg). Strength was assessed using the 1-repetition maximum (1RM) back squat and maximal voluntary isometric contractions of the knee extensors and hip extensors. Three-dimensional running biomechanics were assessed overground at a self-selected speed. Running variables were the peak instantaneous vertical loading rate; peak forward trunk-lean angle; knee-flexion, internal-rotation, and -abduction angles and internal moments; and hip-extension, internal-rotation, and -adduction angles and internal moments. Separate stepwise linear regression models were used to examine the associations between strength and biomechanical outcomes (ΔR2) after accounting for sex, running speed, and foot-strike index. Greater 1RM back-squat strength was associated with a larger peak knee-flexion angle (ΔR2 = 0.110, ΔP = .045) and smaller peak knee internal-rotation angle (ΔR2 = 0.127, ΔP = .03) and internal-rotation moment (ΔR2 = 0.129, ΔP = .03) after accounting for sex, speed, and foot-strike index. No associations were found between 1RM back-squat strength and vertical loading rate, trunk lean, or hip kinematics and kinetics. Hip- and knee-extensor maximal voluntary isometric contractions were also not associated with any biomechanical variables. Greater 1RM back-squat strength was weakly associated with a larger peak knee-flexion angle and smaller knee internal-rotation angle and moment in collegiate distance runners. Runners who are weaker in the back-squat exercise may exhibit running biomechanics associated with the development of knee-related injuries.

Upgrading Seismic Behaviors of R/C Frames with Shaped Memory Alloys Based Braces

Intelligent systems in structural engineering are systems that are capable of automatically adapting structural behavior in response to instantaneous loads, thereby ensuring the safety of extended structural life and performance. One of the new technologies that makes it possible to achieve these goals is the production and development of smart materials. Examples of these smart materials used in structural engineering include piezo-ceramics, magnetorheological fluids, electrorheological fluids, and form-memory alloys. Shaped Memory Alloys (SMAs) are new materials that have been used in various fields of science and engineering in recent decades. In recent years, these materials attracted the attention of researchers in the field of building and earthquake engineering due to their properties such as high damping capacity, low permanent displacement and structural fatigue resistance. One of the application areas of these materials is that they are used as a brace in the structures, so the research results have shown the acceptable performance and operability of such structural systems. In this study, shape memory bracelets and steel bracelets installed as structural brackets were used as a lateral load system in the seismic improvement of concrete bending frames and factors such as residual displacement and base shear in these two load-bearing systems are compared.&amp;amp;nbsp; The model under studying is a 6-story frame that has been subjected to time history analysis. SeismoStruct software was used to analyze the model.

Determination of the load capability for a lithium-ion battery pack using two time-scale filtering

Accurate determination of the continuous and instantaneous load capability is important for safety, durability, and energy deployment of lithium-ion batteries. It is also a crucial challenge for the battery-management-system to determine the load capability of a pack due to inevitable differences among in-pack cells. To overcome these challenges, a flexible battery equivalent-circuit-model is first developed without prior knowledge of in-pack cells’ capacity and internal resistance. Then, a method for determining the load capability of a pack is proposed based on a two time-scale filter using a combination of recursive-least-square-method and Kalman-filter. Distinguished from traditional model-based state-of-charge estimation strategies, only the terminal voltages and currents are used to estimate the open-circuit-voltages of each cell. The temperature and hysteresis effects are compensated to improve estimation accuracy. To reduce the computational complexity, a two time-scale scheme is designed to monitor the state-of-charge and model parameters of in-pack cells, which are further used to determine the peak power of the battery pack. Experiments and simulations conducted on LiFePO4 battery pack are employed to verify the performance of the proposed approach under dynamic operating currents and temperatures. The results indicate that the proposed approach is suitable for determining the load capability of a battery pack.

Fatigue-related changes in vertical impact properties during normal and silent running

ABSTRACT Running while minimizing sound volume can reduce vertical impact loading, potentially reducing injury risks. Fatigue can increase the vertical loading rate during running, but it is unknown whether fatigue influences silent running similarly. This study aimed to explore the differences in vertical impact properties during normal and silent running following a fatiguing task. Seventeen participants performed overground running (normal and silent) before and after a fatiguing running protocol. Running footfall sounds were collected using four microphones surrounding a force platform on the track. Peak impact sound, vertical impact peak force (IPF), instantaneous (VILR), and average vertical loading rate (VALR) were compared from Pre- to Post-fatigue. Peak impact sounds were significantly greater for fatigued runners during normal running when compared to silent running (p < 0.005), without changes in force parameters. Moreover, peak impact sounds, IPF, VILR, and VALR from normal running were greater when compared to silent running (p < 0.001), both fresh or fatigued. Our results suggest that fatigue may not compromise silent running technique, which may be relevant to reduce early vertical impact loading. Therefore, runners seeking to modify running style towards the reduction of impact loading may benefit from including silent running drills in their training sessions.

Effect of shoe cushioning on landing impact forces and spatiotemporal parameters during running: results from a randomized trial including 800+ recreational runners

In a recent randomized trial including 800+ recreational runners, injury risk was lower in those who received the Soft shoe version compared to those using the Hard version (Hazard ratio = 1.52; 95% Confidence Interval = 1.07–2.16). Here, we investigated the effect of shoe cushioning on ground reaction forces (GRF) and spatiotemporal parameters in the same cohort, with a special focus on Vertical Impact Peak Force (VIPF) and Vertical Instantaneous Loading Rate (VILR). Healthy runners (n = 848) randomly received one of two shoe prototypes that differed only in their cushioning properties (Global stiffness: 61 ± 3 and 95 ± 6 N/mm in the Soft and Hard versions, respectively). Participants were tested on an instrumented treadmill at their preferred running speed. GRF data was recorded over 2 min. VIPF was higher in the Soft shoe group compared to the Hard shoe group (1.53 ± 0.21 vs. 1.44 ± 0.23 BW, respectively; p < 0.001). However, the proportion of steps with detectable VIPF was lower in the Soft shoe group (84 vs. 97%, respectively; p < 0.001) and Time to VIPF was longer (46.9 ± 8.5 vs. 43.4 ± 7.4 milliseconds, respectively; p < 0.001). No significant differences were observed for VILR (60.1 ± 13.8 vs. 58.9 ± 15.6 BW/s for Soft and Hard shoe group, respectively; p = 0.070) or any other kinetic variable. These results show that the beneficial effect of greater shoe cushioning on injury risk in the present cohort is not associated with attenuated VIPF and VILR. These GRF metrics may be inappropriate markers of the shoe cushioning-injury risk relationship, while delayed VIPF and the proportion of steps displaying a VIPF could be more relevant. Trial registration: ClinicalTrials.gov identifier: NCT03115437..

Impact-Related Ground Reaction Forces Are More Strongly Associated With Some Running Injuries Than Others

Background: Inconsistent associations have been reported for impact-related ground reaction force variables and running injuries when grouping all injuries together. However, previous work has shown more consistent associations when focusing on specific injuries. Purpose: To compare ground reaction force variables between healthy and injured runners as a group and within specific common injuries. Study Design: Controlled laboratory study. Methods: A total of 125 runners presenting with patellofemoral pain, tibial bone stress injury, plantar fasciitis, Achilles tendinopathy, or iliotibial band syndrome and 65 healthy controls completed an instrumented treadmill assessment at a self-selected speed. Impact-related ground reaction force variables included vertical average (VALR) and instantaneous (VILR) load rates, posterior and medial/lateral instantaneous load rates, and vertical stiffness at initial loading (VSIL). Mean comparisons were made between the general and specific injury and control groups (α = .05). Cutoff thresholds were established and evaluated using several criteria. Results: VALR (+17.5%; P < .01), VILR (+15.8%; P < .01), and VSIL (+19.7%; P < .01) were significantly higher in the overall injured versus control groups. For individual injuries, VALR, VILR, and VSIL were significantly higher for patellofemoral pain (+23.4%-26.4%; P < .01) and plantar fasciitis (+17.5%-29.0%; P < .01), as well as VSIL for Achilles tendinopathy (+29.4%; P < .01). Cutoff thresholds showed better diagnostic criteria for individual versus grouped injuries. Conclusion: Impact variables (VALR, VILR, and VSIL) were significantly higher when assessing the injured group as a whole. However, these findings were driven by specific injury groups, highlighting the importance of taking an injury-specific approach to biomechanical risk factors for running injury. Clinical Relevance: These results suggest that practitioners may want to address impact loading in their treatment of injured runners, especially in those with patellofemoral pain and plantar fasciitis.

Predicting cumulative load during running using field-based measures.

The main objective was to investigate whether the cumulative load of the lower limbs, defined as the product of external load and step rate, could be predicted using spatiotemporal variables gathered with a commercially available wearable device in running. Therefore, thirty-nine runners performed two running tests at 10 and 12km/h, respectively. Spatiotemporal variables (step rate, ground contact time, and vertical oscillation) were collected using a commercially available wearable device. Kinetic variables, measured with gold standard equipment (motion capture system and instrumented treadmill) and used for the calculation of a set of variables representing cumulative load, were peak vertical ground reaction force (peak vGRF), vertical instantaneous loading rate (VILR), vertical impulse, braking impulse, as well as peak extension moments and angular impulses of the ankle, knee and hip joints. Separate linear mixed-effects models were built to investigate the prediction performance of the spatiotemporal variables for each measure of cumulative load. BMI, speed, and sex were included as covariates. Predictive precision of the models ranged from .11 to .66 (R2 m ) and .22 to .98 (R2 c ), respectively. Greatest predictive performance was obtained for the cumulative peak vGRF (R2 m =.66, R2 c =.97), VILR (R2 m =.43, R2 c =.97), braking impulse (R2 m =.52, R2 c =.98), and peak hip extension moment (R2 m =.54, R2 c =.90). In conclusion, certain variables representing cumulative load of the lower limbs in running can be predicted using spatiotemporal variables gathered with a commercially available wearable device.

Dynamics of the behaviour of a vertical wetland (French system) operating in warm-climate conditions, evaluated by means of variables continuously measured in situ

The sewage treatment system in this study was operated with only the first stage of a French system of vertical wetlands, composed of two units in parallel and running with an extended feeding cycle (7 days). This research sought to evaluate and relate continuous variables measured in situ (dissolved oxygen (DO), pH and redox potential) throughout the feeding cycle, with measurements at distinct heights along the filter vertical profile. Additionally, the influence of the surface organic sludge deposit was investigated. A close link between the hydraulic behaviour and the effluent quality was verified, with both being related to the batch volume and the instantaneous hydraulic loading rate. The drop in DO as the feed days progressed could be related to the loss of hydraulic conductivity. A thicker sludge layer decreased the aeration capacity of the filter. The effluent was observed to be aerated when percolating through the medium. DO and pH data suggested that nitrification varied along the filter depth, the batch duration and the feed cycle. The monitored parameters may be indicative of the behaviour of other parameters.

Effects of 12-week cadence retraining on impact peak, load rates and lower extremity biomechanics in running.

BackgroundExcessive impact peak forces and vertical load rates are associated with running injuries and have been targeted in gait retraining studies. This study aimed to determine the effects of 12-week cadence retraining on impact peak, vertical load rates and lower extremity biomechanics during running.MethodsTwenty-four healthy male recreational runners were randomised into either a 12-week cadence retraining group (n = 12), which included those who ran with a 7.5% increase in preferred cadence, or a control group (n = 12), which included those who ran without any changes in cadence. Kinematics and ground reaction forces were recorded simultaneously to quantify impact force variables and lower extremity kinematics and kinetics.ResultsSignificantly decreased impact peak (1.86 ± 0.30 BW vs. 1.67 ± 0.27 BW, P = 0.003), vertical average load rates (91.59 ± 18.91 BW/s vs. 77.31 ± 15.12 BW/s, P = 0.001) and vertical instantaneous load rates (108.8 ± 24.5 BW/s vs. 92.8 ± 18.5 BW/s, P = 0.001) were observed in the cadence retraining group, while no significant differences were observed in the control group. Foot angles (18.27° ± 5.59° vs. 13.74° ± 2.82°, P = 0.003) and vertical velocities of the centre of gravity (CoG) (0.706 ± 0.115 m/s vs. 0.652 ± 0.091 m/s, P = 0.002) significantly decreased in the cadence retraining group at initial contact, but not in the control group. In addition, vertical excursions of the CoG (0.077 ± 0.01 m vs. 0.069 ± 0.008 m, P = 0.002) and peak knee flexion angles (38.6° ± 5.0° vs. 36.5° ± 5.5°, P < 0.001) significantly decreased whilst lower extremity stiffness significantly increased (34.34 ± 7.08 kN/m vs. 38.61 ± 6.51 kN/m, P = 0.048) in the cadence retraining group. However, no significant differences were observed for those variables in the control group.ConclusionTwelve-week cadence retraining significantly increased the cadence of the cadence retraining group by 5.7%. This increased cadence effectively reduced impact peak and vertical average/instantaneous load rates. Given the close relationship between impact force variables and running injuries, increasing the cadence as a retraining method may potentially reduce the risk of impact-related running injuries.

Effects of BMI on Walking Speed and Gait Biomechanics after Anterior Cruciate Ligament Reconstruction.

History of an anterior cruciate ligament reconstruction (ACLR) and high body mass index (BMI) are strong independent risk factors for knee osteoarthritis (KOA) onset. The combination of these risk factors may further negatively affect joint loading and KOA risk. We sought to determine the combined influence of BMI and ACLR on walking speed and gait biomechanics that are hypothesized to influence KOA onset. Walking speed and gait biomechanics (peak vertical ground reaction force [vGRF], peak vGRF instantaneous loading rate [vGRF-LR], peak knee flexion angle, knee flexion excursion [KFE], peak internal knee extension moment [KEM], and peak internal knee abduction moment [KAM]) were collected in 196 individuals with unilateral ACLR and 106 uninjured controls. KFE was measured throughout stance phase, whereas all other gait biomechanics were analyzed during the first 50% of stance phase. A 2 × 2 ANOVA was performed to evaluate the interaction between BMI and ACLR and main effects for both BMI and ACLR on walking speed and gait biomechanics between four cohorts (high BMI ACLR, normal BMI ACLR, high BMI controls, and normal BMI controls). History of an ACLR and high BMI influenced slower walking speed (F1,298 = 7.34, P = 0.007), and history of an ACLR and normal BMI influenced greater peak vGRF-LR (F1,298 = 6.56, P = 0.011). When evaluating main effects, individuals with an ACLR demonstrated lesser KFE (F1,298 = 7.85, P = 0.005) and lesser peak KEM (F1,298 = 6.31, P = 0.013), and individuals with high BMI demonstrated lesser peak KAM (F1,297 = 5.83, P = 0.016). BMI and history of ACLR together influence walking speed and peak vGRF-LR. History of an ACLR influences KFE and peak KEM, whereas BMI influences peak KAM. BMI may need to be considered when designing interventions aimed at restoring gait biomechanics post-ACLR.

Numerical study of trimaran motion and wave load prediction based on time-domain Rankine-Green matching method

The theoretical prediction of trimaran motion and load in complex environment has always been a hot issue in the field of ship and ocean engineering. Based on the calculation principle of Rankine source and free-surface Green function for solving ship-wave interaction, a new kind of nonlinear three-dimensional time-domain Rankine-Green matching method for simulating the trimaran motion and wave load in head seas is studied. In the numerical simulation, the influence of factors such as wave slamming, green water, panel space and density, are investigated systematically. And the elevation of surrounding wave surface caused by speed effect and side hull interference is also considered to modify the instantaneous impact load. In order to verify the reliability of Rankine-Green matching method, a kind of segmented trimaran model with water jet propulsion system was designed and taken in regular and irregular waves. Finally, the numerical forecasting values based on Rankine-Green matching method are compared with the results of model test and traditional frequency-domain Green function method to illustrate its advantages and application scope.

Multifactorial Determinants of Running Injury Locations in 550 Injured Recreational Runners.

Despite the health benefits of running, the prevalence of running-related injuries (RRI) remains high. The underlying risk factors between these injuries are still not well understood. Therefore, the aim of this study was to compare biomechanical, anthropometric, and demographic injury risk factors between different locations in injured recreational runners. In this retrospective case-control analysis, 550 injured runners (49.6% female) with a medically diagnosed RRI were included. All runners had undergone an instrumented treadmill analysis to determine habitual footstrike pattern, vertical instantaneous load rate, peak vertical ground reaction force (vGRF) and cadence. Injuries were classified by location according to a recent consensus statement. A logistic regression model was used to determine the association between the biomechanical parameters and RRI locations. Because injuries can be associated with age, sex, and body mass index, these variables were also entered into the logistic regression. Strike pattern and peak vGRF were the only biomechanical variable distinguishing an injury from the group of injuries. A midfoot strike differentiated Achilles tendon injuries (odds ratio [OR], 2.27; 90% confidence interval [CI], 1.17-4.41) and a forefoot strike distinguished posterior lower leg injuries (OR, 2.59; 90% CI, 1.50-4.47) from the rest of the injured group. Peak vGRF was weakly associated with hip injuries (OR, 1.14; 90% CI, 1.05-1.24). Female sex was associated with injuries to the lower leg (OR, 2.65; 90% CI, 1.45-4.87) and hip/groin (OR, 2.22; 90% CI, 1.43-3.45). Male sex was associated with Achilles tendon injuries (OR, 1.923; 90% CI, 1.094-3.378). Sex, foot strike pattern, and vGRF were the only factors that distinguished specific injury locations from the remaining injury locations.

Research on Meshing Characteristics of Shearer Walking Wheel Based on Rigid-Flexible Coupling

Frequent failure of the walking wheel seriously restricts the performance of the whole shearer. To reduce the failure rate and improve the working performance of the walking wheel, the meshing characteristics of the tooth pin are researched. The dynamic state equations of the walking wheel and the contact force model of tooth pin meshing are established. The rigid-flexible coupling simulation model of tooth pin meshing is built. The load distribution characteristics of the walking wheel are analyzed, as well as the effects of impact load amplitude and duration. Results show that the curve of the longitudinal load distribution coefficient (Kβ) of the contact area is W-shaped, with a maximum of 1.325 at the moment of a single tooth contact. The end of the transition curve is the most serious position of the longitudinal load imbalance at the tooth root. In addition, on the impact moment,Kβtends to decrease and maximum stress obviously increases with the increase in impact load under 40%; the material at the contact position will fail under an extra 39% instantaneous impact load. Furthermore, with the impact load of 30%, the influence of load impact duration under 0.5 s on the meshing characteristics of the walking wheel is relatively faint. The results provide some guidance for the design optimization of the walking wheel and provide a reference for improving the reliability of the shearer.

Validating Commercial Wearable Sensors for Running Gait Parameters Estimation

A growing number of people all over the world are running. Gathering in-field data with wearable sensors is attractive for runners, clinicians and coaches to improve running performance, avoid injury or return to running after an injury. However, it is yet to be proven that commercially available wearable sensors provide valid data. The objective of this study was to assess the validity of five wearable sensors (Moov Now™, MilestonePod, RunScribe™, TgForce and Zoi) to measure ground reaction force related metrics, step rate, foot strike pattern, and vertical displacement of the center of mass during running. Concurrent/criterion validity was assessed against a laboratory-based system using Pearson’s correlation coefficients and ANOVAs. Step rate measurement provided by all wearable sensors was valid (all r > 0.96 and p < 0.001). Only Zoi provided valid vertical displacement of the center of mass (r = 0.81, p < 0.001); only TgForce provided meaningful estimates of instantaneous vertical loading rate (r = 0.76, p < 0.001); only MilestonePod could discriminate between a rear-, mid- and fore-foot strike pattern during running (p < 0.001). None of the wearable sensors was valid for estimating peak braking force. In conclusion, only a few metrics provided by these commercially available wearable sensors are valid. Potential buyers should therefore be aware of such limitations when monitoring running gait variables.

Numerical study of the coupling between the instantaneous blade loading/power of an axial wind turbine and upstream turbulence at high Reynolds numbers

Abstract Little is known about how the range of scales in the approaching turbulent flow can interact dynamically with wind turbine and influence its ability to produce power. Here, a numerical study of a horizontal-axis wind turbine at different Reynolds numbers (corresponding to different tip speed ratios) has been conducted to investigate the instantaneous turbine response to upstream turbulence. A computational approach, combining large eddy simulation with actuator line modelling, is adopted. Comparison between Power Spectral Density (PSD) of the turbine thrust/power and PSD of the velocity at the rotor plane and one rotor diameter upstream of it confirms that there is a coupling between the instantaneous turbine thrust/power and the upstream turbulence ( 1 D upstream of the turbine) for frequencies below a critical frequency. Furthermore, it has been shown for the first time, that PSD of the turbine thrust/power and the velocity PSD at the rotor plane are very similar, indicating that the instantaneous turbine thrust/power and the velocity at the rotor plane are coupled for all frequencies. This means that the PSD of velocity at the rotor plane or shortly behind it can provide interesting information for the instantaneous turbine loads that are very important for the turbine operational life.

Effects Of Minimal, Traditional, And Highly Cushioned Shoes On Injury-related Biomechanics In Rear And Non-rearfoot Strike Runners

Running barefoot, in minimal shoes, or traditional shoes alters certain injury-related biomechanical variables and these footwear effects can be influenced by foot strike pattern. It is unclear however how highly cushioned shoes might alter this interaction. PURPOSE: Given the increasing popularity in highly cushioned footwear in runners, this study assessed the interaction of footwear and foot strike pattern on injury-related biomechanical variables in experienced runners. METHODS: Six rear (RFS) and seven non-rearfoot strike (NRFS) experienced runners completed five running trials at 3.5m/s (±5%) in minimal (MSH), standard (SH) and high cushioned (HC) shoes. A mixed-design repeated measures ANOVA was used to test interaction effects for all injury-related variables. Paired t-tests were used to decipher any interaction effect and Cohen’s d effect sizes were computed to assess mean difference magnitudes. Given the preliminary nature of this work and the small sample size, alpha level was set to 0.1. RESULTS: Strike index confirmed the different strike patterns while running in SH between RFS (15.2±3.1%) and NRFS (102.8±11.8%) groups (p<0.001). Interaction effects were not observed for any of the variables except for peak eversion velocity (p=0.1) and instantaneous vertical loading rate (IVLR; p=0.1) (Figure 1). Main footwear effects were observed for IVLR (p=0.004) and peak eversion velocity (p=0.01). Main foot strike effects were observed for step length (p=0.041), strike index (p=0.00), and IVLR (p=0.00). CONCLUSION: Similar to prior research, these current preliminary findings suggest there might be an interaction between foot strike and footwear in experienced runners for peak eversion velocity and IVLR. Thus, if these biomechanical variables are of interest to scientists or clinicians, these findings suggest that footwear type and strike pattern should both be considered in research or return to running programs.Figure 1:: Instantaneous vertical loading rate (A; IVLR) and peak eversion velocity (B) in the three footwear conditions in rare (RFS; black) and non-rearfoot strike (NRFS; red) runners. *: foot strike group difference within footwear; #: footwear difference within foot strike group (p < 0.1).

The Influence Of Maximal And Minimal Shoes On Walking Biomechanics In Older Individuals

Older individuals frequently walk as a means for exercise and often wear running shoes during this activity. Recently there has been increased popularity in older individuals wearing maximal running shoes during walking. Maximal running shoes are unique because they are comprised of a highly cushioned midsole in both the rearfoot and forefoot that is supposed to improve shock attenuation. Minimal running shoes with little cushioning are also used in this population to improve proprioception and balance. Loading in the frontal plane is of particular interest for older individuals since it has been associated with increased risk of knee osteoarthritis. Little is currently known about how maximal and minimal shoes influence walking biomechanics in any age group. PURPOSE: To examine the influence of maximal and minimal running shoes on walking biomechanics in older individuals. METHODS: Walking biomechanics were collected on 16 female participants (age range: 51 – 64 years) using an 8-camera Vicon motion capture system and two embedded force plates. 3D kinematics and kinetics were collected while subjects walked along a 10-meter runway in three different footwear conditions (MAX, MIN, TRAD). Variables of interest included the 1st and 2nd peak of the vertical ground reaction force (Fz1, Fz2), the instantaneous vertical loading rate (IVLR), peak ankle eversion and knee varus angles, and the peak external ankle eversion and knee varus moments. Differences were determined using a repeated measures ANOVA. RESULTS: The external knee varus moment was significantly higher in the maximal shoe compared to the traditional shoe (MAX: 0.55 ± 0.16 Nm/kg, TRAD: 0.49 ± 0.14 Nm/kg, p = .005). The IVLR was significantly higher in the minimal shoe compared to the traditional shoe (MIN: 30.4 ± 3.4 BW/s, TRAD: 21.8 ± 1.8 BW/s, p < .001). No other significant differences were found for the variables of interest. CONCLUSION: The maximal shoe was found to increase the external knee varus moment, which has been linked to increased pain and disease progression in knee osteoarthritis. The IVLR was significantly higher in the minimal shoe, which has also been linked to injury. Based on these findings, there are no clear advantages to wearing a maximal or minimal shoe during walking, and doing so may be detrimental to injury risk. No grant support was provided.

RESIDUAL STRESS RELAXATION IN A HARDENED CYLINDER UNDER CREEP, LOADED BY AN AXIAL FORCE, TORQUE, AND INTERNAL PRESSURE

A method is developed for solving a boundary-value problem of residual stress relaxation in a surface-hardened hollow cylinder under combined loading by an axial force, torque, and internal pressure. Methods for determining the stress–strain state after hardening and its kinetics during creep are proposed. The effect of internal pressure along with a tensile load or torque on a thick-walled cylindrical sample made of ZhS6KP alloy after air-shot peening is investigated. Computational diagrams for stress tensor components under instantaneous temperature-force loading during creep and after unloading are given and analyzed. The behavior of unhardened and hardened samples at the stage of steady creep after complete residual stress relaxation is compared.