OBJECTIVE: Deep tissue injury (DTI) is caused by prolonged mechanical loading that disrupts blood flow and metabolic clearance. A patient simulator that mimics the biomechanical aspects of DTI initiation, stress and strain in deep muscle tissue, would be potentially useful as a training tool for pressure-relief techniques and testing platform for pressure-mitigating products. As a step toward this goal, this study evaluates the ability of silicone materials to mimic the distribution of stress in muscle tissue under concentrated loading. METHODS: To quantify the mechanical properties of candidate silicone materials, unconfined compression experiments were conducted on 3 silicone formulations (Ecoflex 0030, Ecoflex 0010, and Dragon Skin; Smooth-On, Inc, Easton, Pennsylvania). Results were fit to an Ogden hyperelastic material model, and the resulting shear moduli (G) were compared with published values for biological tissues. Indentation tests were then conducted on Ecoflex 0030 and porcine muscle to investigate silicone’s ability to mimic the nonuniform stress distribution muscle demonstrates under concentrated loading. Finite element models were created to quantify stresses throughout tissue depth. Finally, a preliminary patient simulator prototype was constructed, and both deep and superficial “tissue” pressures were recorded to examine stress distribution. RESULTS: Indentation tests showed similar stress distribution trends in muscle and Ecoflex 0030, but stress magnitudes were higher in Ecoflex 0030 than in porcine muscle. All 3 silicone formulations demonstrated shear moduli within the range of published values for biological tissue. For the experimental conditions reported in this work, Ecoflex 0030 exhibited greater stiffness than porcine muscle. CONCLUSION: Indentation tests and the prototype patient simulator trial demonstrated similar trends with high pressures closest to the bony prominence with decreasing magnitude toward the interfacial surface. Qualitatively, silicone mimicked the phenomenon observed in muscle of nonuniform stress under concentrated loading. Although shear moduli were within biological ranges, stress and stiffness values exceeded those of porcine muscle. This research represents a first step toward development of a preclinical model simulating the biomechanical conditions of stress and strain in deep muscle, since local biomechanical factors are acknowledged to play a role in DTI initiation. Future research is needed to refine the capacity of preclinical models to simulate biomechanical parameters in successive tissue layers of muscle, fat, dermis, and epidermis typically intervening between bone and support surfaces, for body regions at risk for DTI.

Acetabular labral tears are a common cause of hip pain, but specific diagnosis can be difficult due to limitations in current physical examination techniques and radiographic imaging. Pelvic dynamics were captured in 18 participants (10 labral tear patients) who performed single leg squats and stance exercises. Comparisons were made between the pathologic and non-pathologic legs of patients and between patients and controls. The analysis of bilateral symmetry showed significant differences in most parameters implying unique patient compensatory dynamics. Bilateral symmetry was found to be significant in detecting differences in movement patterns and may become a useful tool for clinical evaluation.

An improved understanding of the early behavioral indicators of lumbosacral disease in working dogs may allow earlier interventions and help reduce premature retirement because of disability. However, recognition of early behavioral indicators can be challenging in stoic, high-drive working dogs because they often mask clinical signs. The purpose of this feasibility study was to develop a technique for visualizing canine skeletal movements during working tasks and to describe veterinary clinical specialist opinions on the utility of the visualization technique. Three detection-trained police dogs with a recent history of working task deficits and suspected lumbosacral disease were recruited for the study. Conventional and motion capture video recordings were acquired as dogs performed walking and search high working tasks. Whole-body computed tomography (CT) scans were acquired using clinical multislice CT scanners. Image data from motion capture recordings and whole-body CT scans were analyzed and merged. Three-dimensional (3D) computer animation video clips of skeletal movements were created for each dog and each task, using multiple viewing angle perspectives. Interactive meetings with veterinary clinical specialist reviewers were used to refine point placements for the final renderings. Veterinary clinical specialists reviewed final 3D animation movie clips and recorded their opinions on the utility for the visualization technique. Veterinary clinical specialists reported that the computer animations helped them recognize behavioral characteristics that they had not initially noticed in physical examinations. Potential applications for this visualization technique include creating educational training aids for veterinary students, owners, and handlers; assisting veterinarians in planning rehabilitative treatments; and assisting researchers in developing computer models for biomechanical analyses. Future controlled prospective studies are needed in a large number of normal and affected working dogs to improve accuracy of the visualization technique and test the effect of the technique on observer performance.

This study aimed to compare 2 protocols for the management of back pain in police working dogs. Twenty animals were signaled based on history, trainer complaints, physical and radiographic examination consistent with back pain. In a retrospective study, 2 groups were considered: GM, treated with a solution comprising a combination of lidocaine, dexamethasone, and tiocolchicoseide; and GT, treated with the same solution, with the addition of Traumeel LT. Response to treatment, measured by the Canine Brief Pain Inventory (CBPI, divided into pain interference score – PIS, and pain severity score - PSS) and Hudson Visual Analogue Scale (HVAS), was evaluated before treatment (T0), after 15 (+15d) days and 1 (+30d), 2 (+60d), 3 (+90d), 4 (+120d), 5 (+150d) and 6 (+180d) months. Results were compared using an independent samples t-test or a Paired Samples t-test. Comparing results for each moment with T0 within each group, differences where observed only in GM at +15d (P < .01 for PIS and P < .01 for PSS), +30d (P = .04 for PIS and P < .01 for PSS), +60d (P = .03 for PIS and P = .02 for PSS) and +90d (P = .02 for PSS). Treatment was successful in reducing PSS (reduction of ≥1) in 8/10 animals of GM at +15d (80%), 8/10 at +30d (80%), 5/10 at +60d (50%), 4/10 at +90d (40%), 3/9 at +120d (33.3%) and 2/9 at +150d −+ 180d (22.2%). In GT, treatment was successful in 1/10 at +15d −+30d (10%), 2/10 at +60d (20%) and 1/10 at +90d (10%). No differences were observed with HVAS any time point for either intervention or when comparing groups in each moment. The protocol used in GM produced significant improvements, while the addition of Traumeel did not, rather reducing the effect of treatment in working dogs with back pain. Further studies are required.

Common forms of hip disease include labral tears, synovitis, chondromalacia, or femoroacetabular impingement [1, 2]. Most patients with one of these medical conditions seek treatment to alleviate the pain. However, in addition to the pain, dynamic control of hip joint movement may also be impaired. This impairment may result from damage to proprioceptive organs or alterations in sensory capability caused by inflammation. Reduced biofeedback can lead to a loss of joint control that may result in additional injuries due to excessive tissue strain or falling due to a loss of balance. Our hypothesis is that acetabular labral tears alter normal pelvic movement and reduce subject balance control placing the patient at increased risk for additional injuries.

Objective:To examine ground reaction forces (GRFs); frontal plane hip, knee, and ankle joint angles; and moments in high-arched (HA) and low-arched (LA) athletes during landing. Design:Experimental study. Setting:Controlled research laboratory. Participants:Twenty healthy female recreational athletes (10 HA and 10 LA). Interventions:Athletes performed 5 barefoot drop landings from a height of 30 cm. Main Outcome Measures:Frontal plane ankle, knee, and hip joint angles (in degrees) at initial contact, peak vertical GRF, and peak knee flexion; peak ankle, knee, and hip joint moments in the frontal plane. Results:Vertical GRF profiles were similar between HA and LA athletes (P = 0.78). The HA athletes exhibited significantly smaller peak ankle inversion angles than the LA athletes (P = 0.01) at initial contact. At peak vertical GRF, HA athletes had significantly greater peak knee (P = 0.01) and hip abduction angles than LA athletes (P = 0.02). There were no significant differences between HA and LA athletes in peak joint moments (hip: P = 0.68; knee: P = 0.71; ankle: P = 0.15). Conclusions:These findings demonstrate that foot type is associated with altered landing mechanics, which may underlie lower extremity injuries. The ankle-driven strategy previously reported in female athletes suggests that foot function may have a greater relationship with lower extremity injury than that in male athletes. Future research should address the interaction of foot type and gender during landing tasks.

Mental distractions and physical impairments can increase the risk of accidents by affecting a driver's ability to control the vehicle. In this article, we developed a linear mathematical model that can be used to quantitatively predict drivers' performance over a variety of possible driving conditions. Predictions were not limited only to conditions tested, but also included linear combinations of these tests conditions. Two groups of 12 participants were evaluated using a custom drivers' reaction speed testing device to evaluate the effect of cell phone talking, texting, and a fixed knee brace on the components of drivers' reaction speed. Cognitive reaction time was found to increase by 24% for cell phone talking and 74% for texting. The fixed knee brace increased musculoskeletal reaction time by 24%. These experimental data were used to develop a mathematical model to predict reaction speed for an untested condition, talking on a cell phone with a fixed knee brace. The model was verified by comparing the predicted reaction speed to measured experimental values from an independent test. The model predicted full braking time within 3% of the measured value. Although only a few influential conditions were evaluated, we present a general approach that can be expanded to include other types of distractions, impairments, and environmental conditions.

The medial longitudinal arch plays a major role in determining lower extremity kinematics. Thus, it is necessary to understand the dynamics of the arch structure in response to load. The purpose of this study was to examine arch function in high- and low-arched feet during a vertical loading condition. Ten high- and ten low-arched females performed five trials in a sit-to-stand exercise. Ground reaction force (1200 Hz) and three-dimensional kinematics (240 Hz) were collected simultaneously. The high-and low-arched athletes had no differences in vertical deformation of the arch. High-arched participants were less everted than the low-arched athletes; furthermore, the high-arched athletes had smaller mid-forefoot eversion excursions. Differences between the high-arched and low-arched athletes occur through and motion at the mid-forefoot joint.

Obesity is characterized by excessive body mass relative to height and is a predictor of knee osteoarthritis (OA). Despite the assumption that reduced body mass reduces knee joint loads and knee OA risk, these loads have not been identified in obese people or in formerly obese people after weight loss. PURPOSE: To identify the effects of weight loss on knee joint and muscle forces in obese adults. METHODS: Ground reaction forces and 3D kinematics were measured during walking prior to (baseline, BMI = 43.2) and 6 (BMI = 31.6) and 12 months (BMI = 28.6) after bariatric surgery in 10 adults. Musculoskeletal modeling was applied to these data to predict knee joint and muscle forces which were analyzed with 1-way ANOVA and post-hoc tests comparing baseline vs 6 months and 6 vs 12 months. All subjects gave written informed consent. RESULTS: Body mass decreased 27% from baseline to 6 months and 9% more at 12 months (126 vs 92 vs 84 kg, both p<0.05). Self-selected walking speed was statistically unchanged at 6 months (1.30 vs 1.35 m/s, N.S.) but increased 7% from 6 to 12 months (1.45 m/s, p<0.05). Maximum knee compressive force decreased 18% (2,943 vs 2,417, p<0.05) at 6 months then was statistically unchanged at 12 months (2,557 N). Maximum hamstrings (661 vs 550 N, p<0.05) and gastrocnemius (1,055 vs 805 N, p<0.05) forces were reduced at 6 months compared to baseline. Quadriceps force was statistically unchanged. CONCLUSIONS: Reduced body weight was the primary mechanism in changing knee joint compressive force. Indeed, knee force and body weight were correlated at r=0.82. Knee force most likely did not change from 6 to 12 months because increased walking speed probably counteracted the effect of reduced weight. Speed was correlated to knee force at r=0.49. Quadriceps force went unchanged despite weight loss most likely because step length (r=0.72 with quadriceps force) and knee flexion (r=0.44 with quadriceps force) both increased through the trial (data not shown) increasing quadriceps demand. Our data suggest 1) reduced weight led to reduced hamstrings and gastrocnemius forces which then led to reduced knee force and 2) reduced body weight may serve as a protective mechanism against knee OA incidence by reducing knee joint forces.

The functions of the medial longitudinal arch have been the focus of much research in recent years. Several studies have shown kinematic differences between high- and low-arched runners. No literature currently compares the inter-segmental foot motion of high- and low-arched recreational athletes. The purpose of this study was to examine inter-segmental foot motion in the frontal plane during dynamic loading activities in high- and low-arched female athletes. Inter-segmental foot motions were examined in 10 high- and 10 low-arched female recreational athletes. Subjects performed five barefooted trials in each of the following randomized movements: walking, running, downward stepping and landing. Three-dimensional kinematic data were recorded. High-arched athletes had smaller peak ankle eversion angles in walking, running and downward stepping than low-arched athletes. At the rear-midfoot joint high-arched athletes reached peak eversion later in walking and downward stepping than the low-arched athletes. The high-arched athletes had smaller peak mid-forefoot eversion angles in walking, running and downward stepping than the low-arched athletes. The current findings show that differences in foot kinematics between the high- and low-arched athletes were in position and not range of motion within the foot.

Abnormal foot function has been associated with an increased rate of injury in the athletic population. It has been shown that high-arched (HA) and low-arched (LA) athletes experience different injury patterns. These may be the manifestation of different loading and joint torque patterns in HA and LA athletes. It has been shown that HA and LA athletes have unique kinematic and kinetic patterns during running. However, little research has examined ground reaction forces (GRF) and lower extremity joint kinetics in HA and LA athletes during landing tasks. PURPOSE: To examine GRF and knee and ankle joint torques in HA and LA athletes during a landing task. METHODS: Ten HA (age: 20.8±2.5 years; height: 1.62±0.07 m; mass: 58.3±5.4 kg; arch index: 0.386±0.010) and 10 LA (age: 21.1±2.3; height: 1.63±0.07m; mass: 58.9±10.9kg; arch index: 0.259±0.043) female recreational athletes participated in this study. Each subject performed five barefooted drop landing trials from a height of 30 cm. GRFs and three-dimensional (3D) kinematics were recorded simultaneously using a force plate (1200 Hz, AMTI) and 7-camera motion analysis system (240 Hz, Vicon). GRFs and joint torques were calculated using Visual 3D (C-Motion, Inc.) and critical events were determined using custom software. A one-way ANOVA was used to compare group differences with an alpha level of p<0.05. RESULTS: The GRF profiles were similar between the HA and LA athletes. However, HA athletes exhibited a mean eversion moment compared to an inversion moment in LA athletes (HA: -0.05±0.08 Nm/kg; LA: 0.04±0.07 Nm/kg). Additionally, the HA athletes generated greater peak knee external rotation torques (HA: 0.18±0.06 Nm/kg; LA: 0.26±0.08 Nm/kg) compared to LA athletes during the landing task. Knee extension and abduction torques were similar between the two groups in contrast to previous findings. CONCLUSIONS: The greater mean eversion torques exhibited by the HA athletes may be a response to being more inverted throughout the landing task. Increased eccentric contraction of the ankle everters would control eversion during landing. Similarly, the increased knee external rotation torques would act to limit knee internal rotation during landing. These altered kinetic patterns may increase the risk of injury within these groups of athletes.

Obesity is characterized by increased body mass relative to height. Surprisingly obese vs lean adults can walk on level surface by increasing only ankle power. Incline walking however requires greater hip power in lean adults suggesting that gait adaptations in obese vs lean adults may be task dependent. PURPOSE: Compare lower extremity joint work in obese and lean adults during incline and decline walking. METHODS: 3D ground forces and kinematics were measured in 20 obese (119 kg, 40 kg/m2) and 20 lean (71 kg, 23 kg/m2) adults during 10° incline and decline walking at 1.5 m/s. Joint work and selected kinematic variables were analyzed with 2 × 2 mixed model ANOVA and post hoc tests, p<.05. RESULTS: Significant interactions for stride length (SL) and vertical displacement per step (both p=.015) showed lean had 0.17 m longer strides (p=0.002) and 0.017 m greater displacement (p=0.008) in incline but statistically equal SL and displacement in decline. Significant interaction (p=.014) for joint work summed over hip, knee, and ankle showed lean generated 20% more energy in incline (p=0.001) but dissipated statistically equal energy in decline. Hip (p=.001) and ankle (p=.011) work also significantly interacted between body mass and surface slope. Lean generated 32% more energy at the hip in incline (p=.002) while obese dissipated 237% more energy at the hip in decline (p=0.002). We note however that energy dissipation at the hip was low in decline walking and the lean-obese difference may not be physiological meaningful. Lean generated 17% more energy at the ankle in incline (p=.008) while obese dissipated 34% more energy at the ankle in decline (p=.038). CONCLUSION: The difference of increased body mass relative to height produced a complex response in gait adaptations that are task dependent. Full understanding of biomechanical outcomes of obesity therefore requires comprehensive biomechanical investigations.TABLE

Abnormal foot function has been associated with an increased propensity of injury (Kaufman et al., 1999). Both high- (HA) and low-arched (LA) athletes suffer a greater incidence of injury (Kaufman et al., 1999). Previous research has shown that HA compared to LA runners exhibit greater lower extremity stiffness and greater stiffness within the lower extremity joints (Williams et al., 2004). The purpose of the current study was to examine lower extremity stiffness as well as hip, knee and ankle joint stiffness in HA and LA athletes. It was hypothesized that the HA athletes would have greater stiffness values than the LA athletes within the lower extremity.

Inter-joint coordination and variability during gait provide insight into control and adaptability of the neuromuscular system. To date, coordination research has been restricted to laboratory settings, and it is unclear how these findings translate to real-world, outdoor walking environments.Compared to flat walking, to what extent do outdoor surfaces impact lower-limb inter-joint coordination and variability during gait, in healthy adults?Data from inertial measurement units placed on the lower-back, thigh, and shank were extracted from thirty healthy young adults (15 females, 23.5 ± 4.2 years) during outdoor walking on flat (paved sidewalk); irregular (cobblestone, grass); sloped (slope-up, slope-down); and banked (banked-right, banked-left) surfaces. Sagittal joint angles for the right knee and hip were computed and partitioned by gait phase (stance and swing). Continuous Relative Phase analysis determined inter-joint coordination and variability for the knee-hip joint pair using Mean Absolute Relative Phase (MARP) and Deviation Phase (DP), respectively. One-way repeated measures ANOVAs tested surface effects. Post-hoc Bonferroni adjusted surface comparisons were assessed.Significant knee-hip surface effects were seen during all gait phases for MARP (p < 0.001) and DP (p ≤ 0.001). Compared to flat walking, grass prompted more in-phase coordination (smaller MARP) during stance and swing phase (p ≤ 0.003). Slope-up caused more in-phase coordination during stance (p < 0.001), while slope-down caused more out-of-phase coordination during stance and swing (p ≤ 0.003), compared to the flat surface. Sloped surfaces prompted more variable (larger DP) knee-hip coordination (p ≤ 0.001), compared to flat walking during stance and swing phase.Compared to flat walking, changes in knee-hip coordination and variability were greatest on slope-up/slope-down surfaces. This could reflect greater changes in lower-limb kinematics on sloped surfaces and/or a neuromuscular response to the demands of a more challenging task.

Increased body mass affects gait kinematics and kinetics in adults. It is however unknown if increased body mass produces similar adaptations in children and adults. PURPOSE: To compare gait kinematics and kinetics between lean and obese children and adults. METHODS: Lean (age 13 y, BMI=18 kg/m2) and obese (age 13, BMI=31) children and lean (age 36, BMI=24) and obese (age 34, BMI=48) adults walked at 1.5 m/s on a level surface while gait kinematics and kinetics were measured in one session. RESULTS: The ratio of obesity was similar in children (0.58) and adults (0.50). Gait velocity (1.50 vs 1.48 m/s, p=0.356), stride length (1.50 vs 1.52 m, p=0.624), and cadence (120 vs 117.1 steps/min, p=0.243) were similar in children and adults. Table 1 shows the extensor angular impulses in the 4 groups and 3 joints. In the hip, there was an age (children vs adults, p=0.023), mass (lean vs obese, p=0.02), and a borderline interaction effect (p=0.071), with obese adults producing the highest impulse. In the knee, there was an age (p=0.046), mass (p=0.001), and a borderline interaction effect (p=0.053) with obese vs lean individuals producing more impulse and obese adults producing the highest impulse. In the ankle, there was an age, mass, and interaction effect (all p=0.001) with obese vs lean individuals producing higher impulses and obese adults producing the highest impulse. CONCLUSION: Obesity affects adult gait kinetics more than does obesity in children. This interaction is not due to an interaction of body mass between the four groups and signifies different neuromuscular adaptations to obesity in children and adults. Perhaps obese adults had a longer time to develop the hallmarks of obese gait. Supported in part by NIH R01AG024161Table 1: Extensor impulses (Nm·s, mean ±SD)

Many clinical conditions evoke adaptations in gait. Obese vs lean adults walk more slowly and with a more erect posture. It is unknown if such adaptations become hard-wired with obesity or there is a rapid re-adaptation of obese gait to lean gait after weight loss. PURPOSE: Examine the effects of extreme weight loss on human locomotion 6 months following bariatric surgery. METHODS: 3D lower limb kinematics and kinetics were assessed prior to (n = 5, BMI = 46.8) and six months after (n = 5, BMI = 32.7) bariatric surgery. Subjects walked at their self selected pace and the results of five acceptable trials were averaged. RESULTS: Following surgery, subjects had significantly longer stride lengths (1.42m to 1.49m, p<0.05). There were also large reductions in vertical ground reaction forces (1032N to 736N, p<0.05), and frontal plane average knee torques (-27.3Nm to -20.9Nm, p<0.05). Increases in normalized (body weight x height) sagittal plane maximal ankle plantar flexor torque (7.7Nm/kg*m to 8.5 Nm/kg*m, p<0.05) and normalized (body weight) sagittal plane ankle work (0.003 J/kg to 0.049 J/kg, p<0.05) were observed. CONCLUSIONS: The longer stride length appeared to be driven by the increased torque and work production at the ankle joint. The extreme amount of weight loss contributed to a large reduction in overall external loads placed on each individual. This resulted in large reductions in frontal plane torques at the knee joint to overcome the reduced external loads. The frontal plane knee torque result was especially significant since it is well documented that increased knee adduction torque is a predictor of knee osteoarthritis (OA), which may suggest that due to the significant weight loss, these individuals are less likely to develop knee OA. These data suggest a partial restoration of lean gait after surgery-induced large weight loss in obese adults, with disproportionately large changes in some variables. Supported by NIH R01AG024161.

A temporal analysis of electromyographic (EMG) activity has widely been used for non-invasive study of muscle activation patterns. Such an analysis requires robust methods to accurately detect EMG onset. We examined whether data conditioning, supplemented with Teager-Kaiser Energy Operator (TKEO), would improve accuracy of the EMG burst onset detection. EMG signals from vastus lateralis, collected during maximal voluntary contractions, performed by seventeen subjects (8 males, 9 females, mean age of 46 yrs), were analyzed. The error of onset detection using enhanced signal conditioning was significantly lower than that of onset detection performed on signals conditioned without the TKEO (40 +/-99 ms vs. 229 +/-356 ms, t-test, p = 0.023). The Pearson correlations revealed that neither accuracy after enhanced conditioning nor accuracy after standard conditioning was significantly related to signal-to-noise ratio (SNR) (r = -0.05, p = 0.8 and r = -0.19, p = 0.46, respectively). It is concluded that conditioning of the EMG signals with TKEO significantly improved the accuracy of the threshold-based onset detection methods, regardless of SNR magnitude.