Relationships Between Running Biomechanics and Femoral Articular Cartilage Thickness and Composition in Anterior Cruciate Ligament Reconstruction Patients.

BACKGROUND: Although individuals with anterior cruciate ligament reconstruction (ACLR) are at high risk for posttraumatic osteoarthritis, mechanisms underlying the relationship between running and knee cartilage health remain unclear. OBJECTIVE: We aimed to investigate how 30 min of running influences femoral cartilage thickness and composition and their relationships with running biomechanics in patients with ACLR and controls. METHODS: Twenty patients with ACLR (time post-ACLR: 14.6 ± 6.1 months) and 20 matched controls participated in the study. A running session required both groups to run for 30 min at a self-selected speed. Before and after running, we measured femoral cartilage thickness via ultrasound imaging. A MRI session consisted of T2 mapping. RESULTS: The ACLR group showed longer T2 relaxation times in the medial femoral condyle at resting compared with the control group (central: 51.2 ± 16.6 vs. 34.9 ± 13.2 ms, p = 0.006; posterior: 50.2 ± 10.1 vs. 39.8 ± 7.4 ms, p = 0.006). Following the run, the ACLR group showed greater deformation in the medial femoral cartilage than the control group (0.03 ± 0.01 vs. 0.01 ± 0.01 cm, p = 0.001). Additionally, the ACLR group showed significant negative correlations between resting T2 relaxation time in the medial femoral condyle and vertical impulse (standardized regression coefficients = -0.99 and p = 0.004) during running. CONCLUSIONS: Our findings suggest that those who are between 6 and 24 months post-ACLR have degraded cartilage composition and their cartilage deforms more due to running vGRF.

Effects of balance training with stroboscopic glasses on postural control in chronic ankle instability patients.

Individuals with chronic ankle instability (CAI) are believed to rely more on visual information during postural control due to impaired proprioceptive function, which may increase the risk of injury when their vision is limited during sports activities. OBJECTIVES: To compare (1) the effects of balance training with and without stroboscopic glasses on postural control and (2) the effects of the training on visual reliance in patients with CAI. DESIGN: A randomized controlled clinical trial. METHODS: Twenty-eight CAI patients were equally assigned to one of 2 groups: strobe or control group. The strobe group wore stroboscopic glasses during a 4-week balance training. Static postural control, a single-leg hop balance test calculated by Dynamic Postural Stability Index (DPSI), and the Y-Balance test (YBT) were measured. During the tests, there were different visual conditions: eyes-open (EO), eyes-closed (EC), and strobe vision (SV). Romberg ratios were then calculated as SV/EO, and EC/EO and used for statistical analysis. RESULTS: The strobe group showed a higher pretest-posttest difference in velocity in the medial-lateral direction and vertical stability index under SV compared with the control group (p < .05). The strobe group showed higher differences in EC/EO for velocity in the medial-lateral and anterior-posterior directions, and 95% confidence ellipse area (p < .05), and in SV/EO for velocity in the medial-lateral, 95% confidence ellipse area, and YBT-anterior direction (p < .05). CONCLUSION: The 4-week balance training with stroboscopic glasses appeared to be effective in improving postural control and altering visual reliance in patients with CAI.

Ultrasound Imaging Is Reliable for Tibialis Posterior Size Measurements.

OBJECTIVES: The tibialis posterior (TP) is a vital muscle for controlling the medial longitudinal arch of the foot during weight-bearing activities. Dysfunction of this muscle is associated with a variety of pathologic conditions; thus, it is important to reliably assess its morphologic characteristics. Ultrasound (US) has been used to assess characteristics of TP tendons but not the muscle cross-sectional area (CSA). The purpose of this study was to establish a reliable US technique to measure the TP CSA and thickness. METHODS: Twenty-three healthy volunteers participated. We evaluated the CSA and thickness at 4 measurement locations (anterior and posterior views at both 30% and 50% of the shank length). RESULTS: The participants included 12 female and 11 male volunteers (mean age ± SD, 31.23 ± 14.93 years). Excellent reliability was seen for the CSA and thickness at all locations (intraclass correlation coefficients, 0.988-0.998). Limits of agreement (LoA) and standard errors of the measurement (SEMs) were slightly lower at the 30% locations (LoA at 30%, 4.6-9.2; LoA at 50%, 6.4-9.7; SEM at 30%, 0.03-0.05; SEM at 50%, 0.04-0.07). Strong correlations were seen between anterior and posterior measurements of the CSA (30%, r = 0.99; P < .0001; 50%, r = 0.94; P < .0001) and thickness (30%, r = 0.98; P < .0001; 50%, r = 0.95; P = .0001). CONCLUSIONS: Based on these results, the TP can be measured accurately with US at any of the tested locations. Due to the ease of collection and the quality of the data, we recommend the anterior view at 30% of the shank length to measure the CSA. The ability to assess muscle size of the TP will aid in a variety of medical and research applications.

Use of Cine Loops and Structural Landmarks in Ultrasound Image Processing Improves Reliability and Reduces Error in the Assessment of Foot and Leg Muscles.

OBJECTIVES: Foot and leg muscle strength and size are crucial to proper function. It is important to assess these characteristics reliably. Our primary objective was to compare the measurement of still images to cine loops. The secondary purpose was to determine interoperator and intraoperator reliability between operators of different experience levels using video clips and internal and external landmarks. METHODS: Twelve healthy volunteers participated in our study. Internal (navicular tuberosity) and external (lateral leg length at 30% and 50% from the knee joint line) landmarks were used. Two operators each captured and later measured still and cine loop images of selected foot and leg muscles. RESULTS: The 12 participants included 8 male and 4 female volunteers (mean age ± SD, 23.5 ± 1.9 years). Good to excellent intraoperator and interoperator reliability was seen (intraclass correlation coefficient range of 0.946-0.998). The use of cine loops improved the intraclass correlation coefficients for both intraoperator and interoperator reliability (0.5%-4% increases). The use of cine loops decreased the intraoperator standard error of the measurement and limits of agreement of the novice operator (decreases of 45%-73% and 24%-51%, respectively), and these became comparable to those of experienced operators using still images. The interoperator standard errors of the measurement dropped by 42% to 53%, whereas the limits of agreement dropped by 27% to 40%. No substantial changes were noted in the tibialis anterior across reliability metrics. CONCLUSIONS: Improved protocols that take advantage of using internal bony landmarks and cine loops during both the image-gathering and measurement processes improve the reliability of research examining muscle size changes in the lower leg or foot associated with muscle changes due to exercise, injury, disuse, or disease.

Functional assessments of foot strength: a comparative and repeatability study.

BACKGROUND: Evaluating the strength of the small muscles of the foot may be useful in a variety of clinical applications but is challenging from a methodology standpoint. Previous efforts have focused primarily on the functional movement of toe flexion, but clear methodology guidelines are lacking. A novel foot doming test has also been proposed, but not fully evaluated. The purposes of the present study were to assess the repeatability and comparability of several functional foot strength assessment techniques. METHODS: Forty healthy volunteers were evaluated across two testing days, with a two-week doming motion practice period between them. Seven different measurements were taken using a custom toe flexion dynamometer (seated), custom doming dynamometer (standing), and a pressure mat (standing). Measurements from the doming dynamometer were evaluated for reliability (ICCs) and a learning effect (paired t-tests), while measurements from the toe flexion dynamometer and pressure mat were evaluated for reliability and comparability (correlations). Electromyography was also used to descriptively assess the extent of muscle isolation in all measurements. RESULTS: Doming showed excellent within-session reliability (ICCs > 0.944), but a clear learning effect was present, with strength (p < 0.001) and muscle activity increasing between sessions. Both intrinsic and extrinsic muscles were engaged during this test. All toe flexion tests also showed excellent reliability (ICCs > 0.945). Seated toe flexion tests using the dynamometer were moderately correlated to standing toe flexion tests on a pressure mat (r > 0.54); however, there were some differences in muscle activity. The former may better isolate the toe flexors, while the latter appeared to be more functional for many pathologies. On the pressure mat, reciprocal motion appeared to display slightly greater forces and reliability than isolated toe flexion. CONCLUSIONS: This study further refines potential methodology for foot strength testing. These devices and protocols can be duplicated in the clinic to evaluate and monitor rehabilitation progress in clinical populations associated with foot muscle weakness.

New Perspectives on Foot Segment Forces and Joint Kinetics-Integrating Plantar Shear Stresses and Pressures with Multi-segment Foot Modeling.

The role of the many small foot articulations and plantar tissues in gait is not well understood. While kinematic multi-segment foot models have increased our knowledge of foot segmental motions, the integration of kinetics with these models could further advance our understanding of foot mechanics and energetics. However, capturing and effectively utilizing segmental ground reaction forces remains challenging. The purposes of this study were to (1) develop methodology to integrate plantar pressures and shear stresses with a multi-segment foot model, and (2) generate and concisely display key normative data from this combined system. Twenty-six young healthy adults walked barefoot (1.3 m/s) across a pressure/shear sensor with markers matching a published 4-segment foot model. A novel anatomical/geometric template-based masking method was developed that successfully separated regions aligned with model segmentation. Directional shear force plots were created to summarize complex plantar shear distributions, showing opposing shear forces both between and within segments. Segment centers of pressure (CoPs) were shown to be primarily stationary within each segment, suggesting that forward progression in healthy gait arises primarily from redistributing weight across relatively fixed contact points as opposed to CoP movement within a segment. Inverse dynamics-based normative foot joint moments and power were presented in the context of these CoPs to aid in interpretation of tissue stresses. Overall, this work represents a successful integration of motion capture with direct plantar pressure and shear measurements for multi-segment foot kinetics. The presented tools are versatile enough to be used with other models and contexts, while the presented normative database may be useful as a baseline comparison for clinical work in gait energetics and efficiency, balance, and motor control. We hope that this work will aid in the advancement and availability of kinetic MSF modeling, increase our knowledge of foot mechanics, and eventually lead to improved clinical diagnosis, rehabilitation, and treatment.

Kinetic coupling in distal foot joints during walking.

BACKGROUND: Kinematic coupling between the first metatarsophalangeal (MTP) and midtarsal joints is evident during gait and other movement tasks, however kinetic foot coupling during walking has not been examined. Furthermore, contributing factors to foot coupling are still unclear. Therefore, the purpose of this study was to investigate kinematic and kinetic coupling within the foot by restricting MTP motion during overground walking. We hypothesized that when the MTP joint was prevented from fully extending, the midtarsal joint would achieve less peak motion and generate less positive work compared to walking with normal MTP motion. METHODS: Twenty-six individuals participated in this randomized cross-over study. Using motion capture to track motion, participants walked at 1.3 m/s while wearing a brace that restricted MTP motion in a neutral (BR_NT) or extended (BR_EX) position. Additionally, participants walked while wearing the brace in a freely moveable setting (BR_UN) and with no brace (CON). A pressure/shear sensing device was used to capture forces under each foot segment. During stance, peak joint motion and work were calculated for the MTP and midtarsal joints using inverse dynamics. A series of ANOVAs and Holm post hoc tests were performed for all metrics (alpha = 0.05). RESULTS: The brace successfully decreased peak MTP motion by 19% compared to BR_UN and CON. This was coupled with 9.8% less midtarsal motion. Kinetically, the work absorbed by the MTP joint (26-51%) and generated by the midtarsal joint (30-38%) were both less in BR_EX and BR_NT compared to BR_UN. CONCLUSION: Implications and sources of coupling between the MTP and midtarsal joints are discussed within the context of center of pressure shifts and changes to segmental foot forces. Our results suggest that interventions aimed at modulating MTP negative work (such as footwear or assistive device design) should not ignore the midtarsal joint.

The signed helical angle: A technique for characterizing midfoot motion during gait.

Quantifying motion in the midfoot during gait and other movements is important for a variety of applications, but challenging due to the complexity of the multiple small articulations involved. The most common motion capture based techniques are limited in their ability to characterize the non-planar nature of the midfoot joint axes. In this study we developed a novel Signed Helical Angle (SHA) to quantify midfoot angular displacement. Motion capture data from 40 healthy subjects walking at a controlled speed were used to calculate finite helical axes and angles from a two-segment foot model. Axes were classified as either pronation or supination based on their orientation, and given a sign, thus either adding to or subtracting from the angular displacement. Analysis focused on insights from axis orientation and comparisons to other techniques. Results showed that when transitions were excluded, pronation and supination axes were fairly well clustered in the transverse plane. The resulting SHA midfoot angle waveform was comparable to sagittal plane Euler and helical component waveforms, but with 39% (approximately 3°) greater range of motion in pronation and 25% (approximately 4°) greater in supination, due to the direct measurement of the motion path and the influence of the other planes. The proposed SHA method may provide an intuitive and useful method to analyze midfoot motion for a variety of applications, particularly when interventions cause subtle changes that may be diluted in planar analyses.

The influence of bed height as a percentage of participant height on low back forces when boosting a patient up in bed.

BACKGROUND: Repositioning patients is a frequent task for healthcare workers causing substantial stress to the low back. Patient handling methodologies that reduce low back load should be used. Some studies have observed the effect of bed height on back forces using a limited range of heights. This study details a wider range. OBJECTIVE: The aim of this study was to discover an optimal bed height for reducing low back force when boosting a patient. METHODS: 11 university students and local residents participated by completing a series of boosts with a 91.6 kg research assistant acting as dependent. The bed was adjusted 3% of participant height and 3 boosts were completed at each height which resulted in 8-10 different bed heights depending on the height of the participant. Motion and force data were collected to estimate low back forces via 3DSSPP. Pearson's R was performed to observe the correlation between caregiver height and low back forces. RESULTS: There were significant negative correlations between bed height and low back compression force at L4-L5 (r = -0.676, p = <0.001) and L5-S1 (r = -0.704, p = <0.001). There were no significant correlations with any shear forces. CONCLUSION: The highest bed height led to decreased low back compression forces regardless of participant height, but there was not a significant difference in shear forces. Thus, healthcare workers may experience less low back stress with the bed at a higher height. There may be a force tradeoff between the low back and other parts of the body that needs further exploration. Healthcare workers need to be made aware of the implications of adjusting the environment when performing patient handling tasks.

Low-cost prosthetic feet for underserved populations: A comparison of gait analysis and mechanical stiffness.

BACKGROUND: Lower-limb loss is an ongoing cause of disability throughout the world. Despite advancements in prosthetic technologies, there are numerous underserved populations in need of effective low-cost prosthetic foot options. OBJECTIVE: To evaluate the biomechanical performance of several low-cost prosthetic feet, using a combination of instrumented gait analysis and mechanical stiffness testing. STUDY DESIGN: Randomized crossover with additional case study. METHODS: We compared the solid-ankle-cushioned-heel (SACH), Jaipur, and Niagara feet with carbon fiber feet. Mechanical stiffness was evaluated using a cantilever-style bending test at 2 angles that was designed to mimic late stance gait loading. Eight below-knee amputees participated in the gait analysis, which focused on foot and ankle motion and energetics. RESULTS: Metric analysis showed significant differences among feet in ankle motion and power as well as distal-to-shank power, with SACH showing reduced ankle motion and positive work compared with the other feet. Waveform analysis additionally revealed a compensatory knee flexion moment in SACH and a knee extension moment in Niagara and Jaipur during midstance. In mechanical stiffness testing, SACH had the highest stiffness, with Niagara and carbon fiber roughly similar, and Jaipur the most compliant with the greatest hysteresis. CONCLUSIONS: There may be an optimal stiffness range for future prosthesis designs that maximizes propulsive energy. This may be achieved by combining some characteristics of Jaipur and Niagara feet in new designs. Ultimately, optimizing stiffness and energetics for gait biomimicry while maintaining cost, availability, and versatility across cultures will alleviate the effects of limb loss among underserved populations.

For plantar taping, direction of elasticity matters.

Plantar taping has been used in clinical settings as a short-term conservative treatment for plantar heel pain and related pathologies. The rise of at-home taping methods may offer patients more independence, but effectiveness has not been established. The purpose of this study was to evaluate the effects of plantar taping on foot mechanics during gait. We hypothesized that material compliance would drive mechanical effectiveness, with longitudinally inelastic tape reducing medial longitudinal arch (MLA) motion and anterior/posterior (A/P) plantar tissue spreading forces, and laterally inelastic tape reducing medial/lateral (M/L) tissue spreading. We also hypothesized that these effects would be influenced by foot structure. Fifteen healthy participants were tested in a randomized cross-over study design. Barefoot (BF) plus four taping methods were evaluated, including two inelastic tapes (Low-Dye, LD, and FasciaDerm, FD) along with longitudinally elastic kinesiology tape (KT) and a novel laterally elastic kinesiology tape (FAST, FS). Participants' arch height and flexibility were measured followed by instrumented gait analysis with a multi-segment foot model. Ankle eversion and MLA drop/rise were calculated from rearfoot and forefoot reference frames, while plantar tissue spreading was calculated from shear stresses. ANOVAs with Holm pairwise tests evaluated tape effects while correlations connected arch structure and taping effectiveness (α = 0.05). The three longitudinally inelastic tapes (LD, FD, FS) reduced MLA drop by 11-15% compared with KT and BF. In late stance, these tapes also inhibited MLA rise (LD by 29%, FD and FS by 10-15%). FS and FD reduced A/P spreading forces, while FD reduced M/L spreading forces compared with all other conditions. Arch height had a moderately strong correlation (r = -0.67) with the difference in MLA drop between BF and FS. At-home plantar taping can affect the mechanical function of the foot, but tape elasticity direction matters. Longitudinally elastic kinesiology tape has little effect on mechanics, while inelastic tapes control MLA drop but also restrict MLA rise in late stance. Lateral elasticity does not limit tissue spreading and may increase comfort without sacrificing MLA control. At-home taping has the potential to broaden conservative treatment of plantar heel pain, flat foot deformity, and related pathologies, but additional studies are needed to connect mechanics with symptom relief.

The influence of the windlass mechanism on kinematic and kinetic foot joint coupling.

BACKGROUND: Previous research shows kinematic and kinetic coupling between the metatarsophalangeal (MTP) and midtarsal joints during gait. Studying the effects of MTP position as well as foot structure on this coupling may help determine to what extent foot coupling during dynamic and active movement is due to the windlass mechanism. This study's purpose was to investigate the kinematic and kinetic foot coupling during controlled passive, active, and dynamic movements. METHODS: After arch height and flexibility were measured, participants performed four conditions: Seated Passive MTP Extension, Seated Active MTP Extension, Standing Passive MTP Extension, and Standing Active MTP Extension. Next, participants performed three heel raise conditions that manipulated the starting position of the MTP joint: Neutral, Toe Extension, and Toe Flexion. A multisegment foot model was created in Visual 3D and used to calculate ankle, midtarsal, and MTP joint kinematics and kinetics. RESULTS: Kinematic coupling (ratio of midtarsal to MTP angular displacement) was approximately six times greater in Neutral heel raises compared to Seated Passive MTP Extension, suggesting that the windlass only plays a small kinematic role in dynamic tasks. As the starting position of the MTP joint became increasingly extended during heel raises, the amount of negative work at the MTP joint and positive work at the midtarsal joint increased proportionally, while distal-to-hindfoot work remained unchanged. Correlations suggest that there is not a strong relationship between static arch height/flexibility and kinematic foot coupling. CONCLUSIONS: Our results show that there is kinematic and kinetic coupling within the distal foot, but this coupling is attributed only in small measure to the windlass mechanism. Additional sources of coupling include foot muscles and elastic energy storage and return within ligaments and tendons. Furthermore, our results suggest that the plantar aponeurosis does not function as a rigid cable but likely has extensibility that affects the effectiveness of the windlass mechanism. Arch structure did not affect foot coupling, suggesting that static arch height or arch flexibility alone may not be adequate predictors of dynamic foot function.

The effect of existing and novel walker boot designs on offloading and gait mechanics.

BACKGROUND: Orthopedic walker boots are often used to treat foot ulcers and other wounds with the goal of offloading plantar pressure. However, poor ulcer healing outcomes and high recurrence rates show a need for additional solutions in the growing diabetes epidemic. We compared a novel spring-loaded walker boot to a traditional rigid ankle boot and a hinged ankle boot as well as a control shoe. Our aim was to better understand how boot design affects offloading mechanisms. We hypothesized that all boots would offload force from the foot to the shank, but that the hinged boot would have fewer gait alterations and the spring boot would further reduce pressure in early and late stance. METHODS: Ten healthy participants tested each of the four conditions in static stance and walking gait. Offloading was quantified by the difference between pressure insole and platform forces, while joint mechanics changes were calculated from instrumented gait analysis and inverse dynamics. RESULTS: Minimal offloading was found in the rigid and hinged boots compared to athletic shoes. In contrast, the spring boot offloaded nearly 50% of total load in static stance, with similarly large reductions in peak pressures during gait, particularly under the hindfoot during early stance. All boots resulted in some ankle joint mechanics compensations, with the rigid and spring boots showing similar restrictions in ankle motion and propulsive work. While the hinged boot resulted in ankle mechanics more like the shoe condition, it increased dorsiflexion and negative work, suggesting energetic inefficiency. CONCLUSIONS: The novel spring boot shows promise for more effective offloading that could lead to improved healing outcomes.

Added body mass alters plantar shear stresses, postural control, and gait kinetics: Implications for obesity.

CONTEXT: Obesity is a growing global health concern. The increased body mass and altered mass distribution associated with obesity may be related to increases in plantar shear that putatively leads to physical functional deficits. Therefore, measurement of plantar shear may provide unique insights on the effects of body mass and body distribution on physical function or performance. PURPOSE: 1) To investigate the effects of body mass and distribution on plantar shear. 2) To examine how altered plantar shear influences postural control and gait kinetics. HYPOTHESIS: 1) a weighted vest forward distributed (FV) would shift the center of pressure (CoP) location forward during standing compared with a weighted vest evenly distributed (EV), 2) FV would increase plantar shear spreading forces more than EV during standing, 3) FV would increase postural sway during standing while EV would not, and 4) FV would elicit greater compensatory changes during walking than EV. METHODS: Twenty healthy young males participated in four different tests: 1) static test (for measuring plantar shear and CoP location without acceleration, 2) bilateral-foot standing postural control test, 3) single-foot standing postural test, and 4) walking test. All tests were executed in three different weight conditions: 1) unweighted (NV), 2) EV with 20% added body mass, and 3) FV, also with 20% added body mass. Plantar shear stresses were measured using a pressure/shear device, and several shear and postural control metrics were extracted. Repeated measures ANOVAs with Holms post hoc test were used to compare each metric among the three conditions (α = 0.05). RESULTS: FV and EV increased both AP and ML plantar shear forces compared to NV. FV shifted CoP forward in single-foot trials. FV and EV showed decreased CoP range and velocity and increased Time-to-Boundary (TTB) during postural control compared to NV. EV and FV showed increased breaking impulse and propulsive impulse compared to NV. In addition, EV showed even greater impulses than FV. While EV increased ML plantar shear spreading force, FV increased AP plantar shear spreading force during walking. CONCLUSION: Added body mass increases plantar shear spreading forces. Body mass distribution had greater effects during dynamic tasks. In addition, healthy young individuals seem to quickly adapt to external stimuli to control postural stability. However, as this is a first step study, follow-up studies are necessary to further support the clinical role of plantar shear in other populations such as elderly and individuals with obesity or diabetes.

Whole body kinematic sex differences persist across non-dimensional gait speeds.

Sex differences in human locomotion are of interest in a broad variety of interdisciplinary applications. Although kinematic sex differences have been studied for many years, the underlying reasons behind several noted differences, such as pelvis and torso range of motion, are still not well understood. Walking speed and body size in particular represent confounding influences that hinder our ability to determine causal factors. The purpose of this study was to investigate sex differences in whole body gait kinematics across a range of controlled, non-dimensional walking and running speeds. We hypothesized that as task demand (i.e. gait speed) increased, the influences of modifiable factors would decrease, leading to a kinematic motion pattern convergence between sexes. Motion capture data from forty-eight healthy young adults (24 M, 24 F) wearing controlled footwear was captured at three walking and three running Froude speeds. Spatiotemporal metrics, center of mass displacement, and joint/segment ranges of motion were compared between sexes using 2x6 mixed-model ANOVAs. Three dimensional time-series waveforms were also used to describe the time-varying behavior of select joint angles. When controlling for size, sex differences in spatiotemporal metrics and center of mass displacement disappeared. However, contrary to our hypothesis, sagittal plane ankle, frontal plane pelvis, and transverse plane pelvis and torso range of motion all displayed sex differences that persisted or increased with gait speed. Overall, most spatiotemporal sex differences appear to be related to size and self-selection of gait speeds, while in contrast, sex differences in joint motion may be more inherent and ubiquitous than previously thought. Discussion on potential causal factors is presented.

Simultaneous ice and transcutaneous electrical nerve stimulation decrease anterior knee pain during running but do not affect running kinematics or associated muscle inhibition.

BACKGROUND: Runners often experience anterior knee pain and this pain is associated with altered running neuromechanics. The purpose of this study was to examine potential therapeutic benefits (reduced pain and restored running neuromechanics) of simultaneously applied ice and transcutaneous electrical nerve stimulation on experimentally-induced anterior knee pain. METHODS: Nineteen healthy subjects completed a sham and treatment data collection session. For both sessions, hypertonic saline was infused into the infrapatellar fat pad for approximately 80 min to induce experimental anterior knee pain. Perceived pain levels were measured every two minutes and running neuromechanics were recorded at four time points: pre-pain, pain before treatment, pain immediately post-treatment, and pain 20 min post-treatment. FINDINGS: The saline infusion significantly increased perceived knee pain from 0 to 2.8 cm. The ice/transcutaneous electrical nerve stimulation treatment significantly reduced perceived knee pain by 35%, six minutes after the treatment initiation. Perceived knee pain remained reduced until eight minutes after the treatment termination. The knee pain significantly decreased peak gluteus medius, vastus lateralis, and vastus medialis activation during running, each by an average of 17% plus/minus 6%; however, none of these decreases were resolved via the therapeutic treatment. Neither the knee pain nor the therapeutic treatment significantly affected peak gluteus maximus activation or peak hip adduction angle. INTERPRETATION: The experimental pain model effectively produced anterior knee pain and decreased muscle activation during running. The simultaneous ice/transcutaneous electrical nerve stimulation treatment effectively decreased anterior knee pain, but did not restore running neuromechanics that were altered due to the pain.

Early-Stage Diabetic Neuropathy Reduces Foot Strength and Intrinsic but Not Extrinsic Foot Muscle Size.

BACKGROUND: Tracking progression of diabetic peripheral polyneuropathy (DPN) is usually focused on sensory nerves and subjective testing methods. Recent studies have suggested that distal muscle atrophy may precede sensation loss. Methods to objectively measure distal muscle size and strength are needed to help understand how neuropathy affects muscle function. PURPOSE: To evaluate individual intrinsic and extrinsic foot muscle sizes and functional foot strength in participants with DPN. METHODS: Thirty individuals participated in this cross-sectional study (15 DPN and 15 matched controls). Sizes of 10 separate muscles of the lower leg and foot were measured using ultrasound imaging. Functional foot strength was also quantified using custom great toe and lateral toe flexion tests along with a doming test. Muscle size and strength metrics were compared between groups using ANOVAs and paired t-tests (α = 0.05). Correlations between strength and relevant muscle sizes were also evaluated. RESULTS: The sizes of all four intrinsic foot muscles were smaller in individuals with DPN (p ≤ 0.03), while only one (toe extensor) of the six extrinsic muscles was smaller (p ≤ 0.03), while only one (toe extensor) of the six extrinsic muscles was smaller (p ≤ 0.03), while only one (toe extensor) of the six extrinsic muscles was smaller (p ≤ 0.03), while only one (toe extensor) of the six extrinsic muscles was smaller (r ≤ 0.80) with several corresponding intrinsic muscle sizes. The doming strength test did not show any difference between groups and was moderately correlated with one muscle size (r ≤ 0.80) with several corresponding intrinsic muscle sizes. The doming strength test did not show any difference between groups and was moderately correlated with one muscle size (. CONCLUSION: Diabetic peripheral polyneuropathy affects intrinsic muscles before extrinsics. Ultrasound imaging of individual muscles and functional toe flexion tests can be used clinically to monitor DPN progression and foot function. Participants need to be trained in the doming test before a relationship can be established between this test and DPN foot function. Future studies should include muscle quality measurements to better understand characteristics of affected muscles.

Ankle and midtarsal joint quasi-stiffness during walking with added mass.

Examination of how the ankle and midtarsal joints modulate stiffness in response to increased force demand will aid understanding of overall limb function and inform the development of bio-inspired assistive and robotic devices. The purpose of this study is to identify how ankle and midtarsal joint quasi-stiffness are affected by added body mass during over-ground walking. Healthy participants walked barefoot over-ground at 1.25 m/s wearing a weighted vest with 0%, 15% and 30% additional body mass. The effect of added mass was investigated on ankle and midtarsal joint range of motion (ROM), peak moment and quasi-stiffness. Joint quasi-stiffness was broken into two phases, dorsiflexion (DF) and plantarflexion (PF), representing approximately linear regions of their moment-angle curve. Added mass significantly increased ankle joint quasi-stiffness in DF (p < 0.001) and PF (p < 0.001), as well as midtarsal joint quasi-stiffness in DF (p < 0.006) and PF (p < 0.001). Notably, the midtarsal joint quasi-stiffness during DF was ~2.5 times higher than that of the ankle joint. The increase in midtarsal quasi-stiffness when walking with added mass could not be explained by the windlass mechanism, as the ROM of the metatarsophalangeal joints was not correlated with midtarsal joint quasi-stiffness (r = -0.142, p = 0.540). The likely source for the quasi-stiffness modulation may be from active foot muscles, however, future research is needed to confirm which anatomical structures (passive or active) contribute to the overall joint quasi-stiffness across locomotor tasks.

The Role of the Midfoot in Drop Landings.

PURPOSE: The midfoot is instrumental to foot function; however, quantifying its roles in human movement has been difficult. A forceful dynamic activity like landing may help elucidate the midfoot's contribution to foot energetics and function. The main purpose of this study was to measure midtarsal joint kinematics and kinetics during a barefoot single-leg landing task. A secondary aim of this study was to explore the relationship between static foot posture and dynamic midfoot function. METHODS: In a cross-sectional study design, 48 females (age = 20.4 ± 1.8 yr, body mass index = 21.6 ± 1.7 kg·m) performed drop landings from a height of 0.4 m onto split force platforms. Subjects hung from wooden rings and landed on their dominant leg. Midtarsal joint kinematic and kinetic data were recorded using a 14-camera optical motion capture system in conjunction with two in-ground force platforms and a custom kinetic three-segment foot model. Foot structure was measuring using the arch height index (AHI) and the static midtarsal joint angle from motion capture. RESULTS: Kinematic data revealed an average sagittal plane midtarsal joint range of motion of 27° through the landing phase. Kinetic data showed that between 7% and 22% of the total lower extremity joint, work during the landing was performed by the midtarsal joint. Both standing AHI and static midtarsal joint angle (static MA) were correlated with sagittal plane midtarsal joint range of motion (standing AHI: r = -0.320, P = 0.026; static MA: r = 0.483, P < 0.001) and with midtarsal joint work (standing AHI: r = 0.332, P = 0.021; static MA: r = -0.323, P = 0.025). CONCLUSION: The midfoot contributes substantially to landing mechanics during a barefoot single-leg landing task. Static foot posture measures have limited value in predicting midfoot kinematics and kinetics during sportlike landings.

Walking in Minimalist Shoes Is Effective for Strengthening Foot Muscles.

INTRODUCTION: Weakness of foot muscles may contribute to a variety of loading-related injuries. Supportive footwear may contribute to intrinsic foot muscle weakness by reducing the muscles' role in locomotion (e.g., absorbing forces and controlling motion). Increased stimulus to the foot muscles can be provided through a variety of mechanisms, including minimalist footwear and directed exercise. PURPOSE: To determine the effect of walking in minimalist footwear or performing foot strengthening exercises on foot muscle size and strength. METHODS: Fifty-seven runners were randomly assigned to one of three groups-minimalist shoe walking (MSW), foot strengthening (FS) exercise, or control (C). All groups maintained their prestudy running mileage throughout the study. The MSW group walked in provided footwear, increasing weekly the number of steps per day taken in the shoes. The FS group performed a set of progressive resistance exercises at least 5 d·wk. Foot muscle strength (via custom dynamometers) and size (via ultrasound) were measured at the beginning (week 0), middle (week 4), and end (week 8) of the study. Mixed model ANOVA were run to determine if the interventions had differing effects on the groups. RESULTS: There were significant group-time interactions for all muscle size and strength measurements. All muscle sizes and strength increased significantly from weeks 0 to 8 in the FS and MSW groups, whereas there were no changes in the C group. Some muscles increased in size by week 4 in the FS and MSW groups. CONCLUSIONS: Minimalist shoe walking is as effective as foot strengthening exercises in increasing foot muscle size and strength. The convenience of changing footwear rather than performing specific exercises may result in greater compliance.