Associations among knee adduction moment, frontal plane ground reaction force, and lever arm during walking in patients with knee osteoarthritis

The adduction moment about the knee during walking gait has been proposed as an indirect measure of dynamic knee joint load. However, the relative contributions of the variables primarily used to calculate the knee adduction moment have not been investigated. The objectives of this paper were to: (1) describe and compare the magnitude and temporal characteristics of the knee adduction moment, frontal plane lever arm, and frontal plane ground reaction force (GRF) during gait in patients with knee osteoarthritis (OA) and, (2) examine the associations among these variables. Results indicated that both the knee adduction moment and the frontal plane GRF varied considerably throughout stance and exhibited the characteristic "double-hump" pattern, while the frontal plane lever arm magnitude varied only slightly during stance. Knees with OA had significantly greater peak knee adduction moments and frontal plane lever arms, but significantly less peak frontal plane GRF than knees without OA. Pearson product moment correlations indicated a higher association between peak knee adduction moment and peak frontal plane lever arm than between peak knee adduction moment and peak frontal plane GRF, particularly in knees with OA. These results suggest that the frontal plane lever arm assessed during walking is an important variable in the examination of knee OA, and warrants further investigation.     

Strong independent associations between gait biomechanics and pain in patients with knee osteoarthritis

We investigated the simple and multivariate associations between knee pain and gait biomechanics. 279 patients with medial knee osteoarthritis (OA) and discordant changes in pain between limbs after walking completed bilateral three-dimensional gait analysis. For each limb, patients rated their pain before and after a 6-min walk and the change in pain was recorded as an increase (≥1 points) or not (≤0 points). Among paired limbs, the simple and multivariate associations between an increase in pain and the external moments in each orthogonal plane were evaluated using conditional logistic regression. The analyses were then repeated for knee angles. Univariate analyses demonstrated associations in each plane that varied in both magnitude and direction, with larger associations for the knee moments [Odds Ratio (95% confidence interval) = first peak adduction moment: 2.80 (2.02, 3.88), second peak adduction moment: 2.36 (1.73, 3.24), adduction impulse: 6.65 (3.50, 12.62), flexion moment: 0.46 (0.36, 0.60), extension moment: 0.56 (0.44, 0.71), internal rotation moment: 7.54 (3.32, 17.13), external rotation moment: 0.001 (0.00, 0.04)]. Multivariate analyses with backward elimination resulted in a model including only the adduction impulse [5.35 (2.51, 11.42)], flexion moment [0.32 (0.22, 0.46)] and extension moment [0.28 (0.19, 0.42)]. The varus, flexion and extension angles were included in the final multivariate model for the knee angles. When between-person confounding is lessened by comparing limbs within patients, there are strong independent associations between knee pain and multiple external knee moments that vary in magnitude and direction. While controlling for other knee moments, a greater adduction impulse and lower flexion and extension moments were independently associated with greater odds of an increase in pain.     

Hip joint moments in symptomatic vs. asymptomatic people with mild radiographic hip osteoarthritis

Our primary objective was to examine external hip joint moments during walking in people with mild radiographic hip osteoarthritis (OA) with and without symptoms and disease-free controls. Three groups were compared (symptomatic with mild radiographic hip OA, n = 12; asymptomatic with mild radiographic hip OA, n = 13; OA-free controls, n = 20). Measures of the external moment (peak and impulse) in the sagittal, frontal and transverse plane during walking were determined. Variables were compared according to group allocation using mixed linear regression models that included individual gait trials, with group allocation as fixed effect and walking speed as a random effect. Participants with evidence of radiographic disease irrespective of symptoms walked 14–16% slower compared to disease-free controls (p = 0.002). Radiographic disease without symptoms was not associated with any altered measures of hip joint moment compared to asymptomatic OA-free controls once speed was taken into account (p ≥ 0.099). People with both mild radiographic disease and symptoms had lower external peak hip adduction moment (p = 0.005) and lower external peak internal rotation moment (p < 0.001) accounting for walking speed. Among angular impulses, only the presence of symptoms was associated with a reduced hip internal rotation impulse (p = 0.002) in the symptomatic group. Collectively, our observations suggest that symptoms have additional mechanical associations from radiographic disease alone, and provide insight into potential early markers of hip OA. Future research is required to understand the implications of modifying walking speed and/or the external hip adduction and internal rotation moment in people with mild hip OA.     

Kinematic adaptations to a variable stiffness shoe: mechanisms for reducing joint loading

A recently described variable-stiffness shoe has been shown to reduce the adduction moment and pain in patients with medial-compartment knee osteoarthritis. The mechanism associated with how this device modifies overall gait patterns to reduce the adduction moment is not well understood. Yet this information is important for applying load modifying intervention for the treatment of knee osteoarthritis. A principal component analysis (PCA) was used to test the hypothesis that there are differences in the frontal plane kinematics that are correlated with differences in the ground reaction forces (GRFs) and center of pressure (COP) for a variable-stiffness compared to a constant-stiffness control shoe. Eleven healthy adults were tested in a constant-stiffness control shoe and a variable-stiffness shoe while walking at self-selected speeds. The PCA was performed on trial vectors consisting of all kinematic, GRF and COP data. The projection of trial vectors onto the linear combination of four PCs showed there were significant differences between shoes. The interpretation of the PCs indicated an increase in the ankle eversion, knee abduction and adduction, decreases in the hip adduction and pelvic obliquity angles and reduced excursion of both the COP and peak medial-lateral GRFs for the variable-stiffness compared to the control shoe. The variable-stiffness shoe produced a unique dynamic change in the frontal plane motion of the ankle, hip and pelvis that contributed to changes in the GRF and COP and thus reduced the adduction moment at a critical instant during gait suggesting a different mechanism that was seen with fixed interventions (e.g. wedges).     

Knee moment outcomes using inverse dynamics and the cross product function in moderate knee osteoarthritis gait: A comparison study

Inverse dynamics are the cornerstone of biomechanical assessments to calculate knee moments during walking. In knee osteoarthritis, these outcomes have been used to understand knee pathomechanics, but the complexity of an inverse dynamic model may limit the uptake of joint moments in some clinical and research structures. The objective was to determine whether discrete features of the sagittal and frontal plane knee moments calculated using inverse dynamics compare to knee moments calculated using a cross product function. Knee moments from 74 people with moderate knee osteoarthritis were assessed after ambulating at a self-selected speed on an instrumented dual belt treadmill. Standardized procedures were used for surface marker placement, gait speed determination and data processing. Net external frontal and sagittal plane knee moments were calculated using inverse dynamics and the three-dimensional position of the knee joint center with respect to the center of pressure was crossed with the three-dimensional ground reaction forces in the cross product function. Correlations were high between outcomes of the moment calculations (r > 0.9) and for peak knee adduction moment, knee adduction moment impulse and difference between peak flexion and extension moments, the cross product function resulted in absolute values less than 10% of those calculated using inverse dynamics in this treadmill walking environment. This computational solution may allow the integration of knee moment calculations to understand knee osteoarthritis gait without data collection or computational complexity.     

Predicting changes in knee adduction moment due to load-altering interventions from pressure distribution at the foot in healthy subjects

The purpose of this pilot study of healthy subjects was to determine if changes in foot pressure patterns associated with a lateral wedge can predict the changes in the knee adduction moment. We tested two hypotheses: (1) increases or decreases in the knee adduction moment and ankle eversion moment due to load-altering footwear interventions can be predicted from foot pressure distribution and (2) changes in magnitude of the knee adduction moment and ankle eversion moment due to lateral wedges can be predicted from pressure distribution at the foot during walking. Fifteen healthy adults performed walking trials in three shoes: 0 degrees , 4 degrees , and 8 degrees laterally wedged. Maximum heel pressure ratio, first peak knee adduction moment, and peak ankle eversion moment were assessed using a pressure mat, motion capture system, and force plate. Increases or decreases in the knee adduction moment and ankle eversion moment were predicted well from foot pressure distribution. However, the magnitude of the pressure change did not predict the magnitude of the peak knee adduction moment change or peak ankle eversion moment change. Factors such as limb alignment or trunk motion may affect the knee adduction moment and override a direct relationship between the pressure distribution at the shoe-ground interface and the load distribution at the knee. However, changes (increases or decreases) in the peak knee adduction moment due to load-altering footwear interventions predicted from pressure distribution during walking can be important when evaluating these types of interventions from a clinical perspective.     

Knee biomechanics of moderate OA patients measured during gait at a self-selected and fast walking speed

Osteoarthritis (OA) is a chronic disorder resulting in degenerative changes to the knee joint. Three-dimensional gait analysis provides a unique method of measuring knee dynamics during activities of daily living such as walking. The purpose of this study was to identify biomechanical features characterizing the gait of patients with mild-to-moderate knee OA and to determine if the biomechanical differences become more pronounced as the locomotor system is stressed by walking faster. Principal component analysis was used to compare the gait patterns of a moderate knee OA group (n=41) and a control group (n=43). The subjects walked at their self-selected speed as well as at 150% of that speed. The two subject groups did not differ in knee joint angles, stride length, and stride time or walking speed. Differences in the magnitude and shape of the knee joint moment waveforms were found between the two groups. The OA group had larger adduction moment magnitudes during stance and this higher magnitude was sustained for a longer portion of the gait cycle. The OA group also had a reduced flexion moment and a reduced external rotation moment during early stance. Increasing speed was associated with an increase in the magnitude of all joint moments. The fast walks did not, however, increase or bring out any biomechanical differences between the OA and control groups that did not exist at the self-selected walks.     

Gait retraining to reduce the knee adduction moment through real-time visual feedback of dynamic knee alignment

Varus knee alignment is a risk factor for medial knee osteoarthritis and is associated with high knee adduction moments. Therefore, reducing the knee adduction moment in varus-aligned individuals with otherwise healthy knees may reduce their risk for developing osteoarthritis. A gait modification that improves dynamic knee alignment may reduce the adduction moment, and systematic training may lead to more natural-feeling and less effortful execution of this pattern. To test these hypotheses, eight healthy, varus-aligned individuals underwent a gait modification protocol. Real-time feedback of dynamic knee alignment was provided over eight training sessions, using a fading paradigm. Natural and modified gait were assessed post-training and after 1 month, and compared to pre-training natural gait. The knee adduction moment, as well as hip adduction, hip internal rotation and knee adduction angles were evaluated. At each training session, subjects rated how effortful and natural-feeling the modified pattern was to execute. Post-training, the modified pattern demonstrated an 8° increase in hip internal rotation and 3° increase in hip adduction. Knee adduction decreased 2°, and the knee adduction moment decreased 19%. Natural gait did not differ between the three visits, nor did the modified gait pattern between the post-training and 1 month visits. The modified pattern felt more natural and required less effort after training. Based on these results, gait retraining to improve dynamic knee alignment resulted in significant reductions in the knee adduction moment, primarily through hip internal rotation. Further, systematic training led to more natural-feeling and less effortful execution of the gait pattern.     

Experimentally reduced hip abductor function during walking: Implications for knee joint loads

Hip and knee functions are intimately connected and reduced hip abductor function might play a role in development of knee osteoarthritis (OA) by increasing the external knee adduction moment during walking. The purpose of this study was to test the hypothesis that reduced function of the gluteus medius (GM) muscle would lead to increased external knee adduction moment during level walking in healthy subjects. Reduced GM muscle function was induced experimentally, by means of intramuscular injections of hypertonic saline that produced an intense short-term muscle pain and reduced muscle function. Isotonic saline injections were used as non-painful control. Fifteen healthy subjects performed walking trials at their self-selected walking speed before and immediately after injections, and again after 20 min of rest, to ensure pain recovery. Standard gait analyses were used to calculate three-dimensional trunk and lower extremity joint kinematics and kinetics. Surface electromyography (EMG) of the glutei, quadriceps, and hamstring muscles were also measured. The peak GM EMG activity had temporal concurrence with peaks in frontal plane moments at both hip and knee joints. The EMG activity in the GM muscle was significantly reduced by pain (?39.6%). All other muscles were unaffected. Peaks in the frontal plane hip and knee joint moments were significantly reduced during pain (?6.4% and ?4.2%, respectively). Lateral trunk lean angles and midstance hip joint adduction and knee joint extension angles were reduced by ?1°. Thus, the gait changes were primarily caused by reduced GM function. Walking with impaired GM muscle function due to pain significantly reduced the external knee adduction moment. This study challenge the notion that reduced GM function due to pain would lead to increased loads at the knee joint during level walking.     

A variable-stiffness shoe lowers the knee adduction moment in subjects with symptoms of medial compartment knee osteoarthritis

The purpose of this study was to evaluate the effectiveness of variable-stiffness shoes in lowering the peak external knee adduction moment during walking in subjects with symptomatic medial compartment knee osteoarthritis. The influence on other lower extremity joints was also investigated. The following hypotheses were tested: (1) variable-stiffness shoes will lower the knee adduction moment in the symptomatic knee compared to control shoes; (2) reductions in knee adduction moment will be greater at faster speeds; (3) subjects with higher initial knee adduction moments in control shoes will have greater reductions in knee adduction moment with the intervention shoes; and (4) variable-stiffness shoes will cause secondary changes in the hip and ankle frontal plane moments. Seventy-nine individuals were tested at self-selected slow, normal, and fast speeds with a constant-stiffness control shoe and a variable-stiffness intervention shoe. Peak moments for each condition were assessed using a motion capture system and force plate. The intervention shoes reduced the peak knee adduction moment compared to control at all walking speeds, and reductions increased with increasing walking speed. The magnitude of the knee adduction moment prior to intervention explained only 11.9% of the variance in the absolute change in maximum knee adduction moment. Secondary changes in frontal plane moments showed primarily reductions in other lower extremity joints. This study showed that the variable-stiffness shoe reduced the knee adduction moment in subjects with medial compartment knee osteoarthritis without the discomfort of a fixed wedge or overloading other joints, and thus can potentially slow the progression of knee osteoarthritis.     

Differences in lower limb transverse plane joint moments during gait when expressed in two alternative reference frames

When comparing previous studies that have measured the three-dimensional moments acting about the lower limb joints (either external moments or opposing internal joint moments) during able-bodied adult gait, significant variation is apparent in the profiles of the reported transverse plane moments. This variation cannot be explained on the basis of adopted convention (i.e. external versus internal joint moment) or inherent variability in gait strategies. The aim of the current study was to determine whether in fact the frame in which moments are expressed has a dominant effect upon transverse plane moments and thus provides a valid explanation for the observed inconsistency in the literature. Kinematic and ground reaction force data were acquired from nine able-bodied adult subjects walking at a self-selected speed. Three-dimensional hip, knee and ankle joint moments during gait were calculated using a standard inverse dynamics approach. In addition to calculating internal joint moments, the components of the external moment occurring in the transverse plane at each of the lower limb joints were calculated to determine their independent effects. All moments were expressed in both the laboratory frame (LF) as well as the anatomical frame (AF) of the distal segment. With the exception of the ankle rotation moment in the foot AF, lower limb transverse plane joint moments during gait were found to display characteristic profiles that were consistent across subjects. Furthermore, lower limb transverse plane joint moments during gait differed when expressed in the distal segment AF compared to the LF. At the hip, the two alternative reference frames produced near reciprocal joint moment profiles. The components of the external moment revealed that the external ground reaction force moment was primarily responsible for this result. Lower limb transverse plane joint moments during gait were therefore found to be highly sensitive to a change in reference frame. These findings indicate that the different transverse plane joint moment profiles during able-bodied adult gait reported in the literature are likely to be explained on this basis.     

Quantitative evaluation of the major determinants of human gait

Accurate knowledge of the isolated contributions of joint movements to the three-dimensional displacement of the center of mass (COM) is fundamental for understanding the kinematics of normal walking and for improving the treatment of gait disabilities. Saunders et al. (1953) identified six kinematic mechanisms to explain the efficient progression of the whole-body COM in the sagittal, transverse, and coronal planes. These mechanisms, referred to as the major determinants of gait, were pelvic rotation, pelvic list, stance knee flexion, foot and knee mechanisms, and hip adduction. The aim of the present study was to quantitatively assess the contribution of each major gait determinant to the anteroposterior, vertical, and mediolateral displacements of the COM over one gait cycle. The contribution of each gait determinant was found by applying the concept of an ‘influence coefficient’, wherein the partial derivative of the COM displacement with respect to a prescribed determinant was calculated. The analysis was based on three-dimensional measurements of joint angular displacements obtained from 23 healthy young adults walking at slow, normal and fast speeds. We found that hip flexion, stance knee flexion, and ankle-foot interaction (comprised of ankle plantarflexion, toe flexion and the displacement of the center of pressure) are the major determinants of the displacements of the COM in the sagittal plane, while hip adduction and pelvic list contribute most significantly to the mediolateral displacement of the COM in the coronal plane. Pelvic rotation and pelvic list contribute little to the vertical displacement of the COM at all walking speeds. Pelvic tilt, hip rotation, subtalar inversion, and back extension, abduction and rotation make negligible contributions to the displacements of the COM in all three anatomical planes.     

Feasibility of a gait retraining strategy for reducing knee joint loading: increased trunk lean guided by real-time biofeedback

The purpose of this feasibility study was to examine changes in frontal plane knee and hip walking biomechanics following a gait retraining strategy focused on increasing lateral trunk lean and to quantify reports of difficulty and joint discomfort when performing such a gait modification. After undergoing a baseline analysis of normal walking, 9 young, healthy participants were trained to modify their gait to exhibit small (4°), medium (8°), and large (12°) amounts of lateral trunk lean. Training was guided by the use of real-time biofeedback of the actual trunk lean angle. Peak frontal plane external knee and hip joint moments were compared across conditions. Participants were asked to report the degree of difficulty and the presence of any joint discomfort for each amount of trunk lean modification. Small (4°), medium (8°), and large (12°) amounts of lateral trunk lean reduced the peak external knee adduction moment (KAM) by 7%, 21%, and 25%, respectively, though the peak KAM was only significantly less in the medium and large conditions (p<0.001). Increased trunk lean also significantly reduced the peak external hip adduction moments (p<0.001). All participants reported at least some difficulty performing the exaggerated trunk lean pattern and three participants reported ipsilateral knee, hip, and/or lower spine discomfort. Results from this study indicate that a gait pattern with increased lateral trunk lean can effectively reduce frontal plane joint moments. Though these findings have implications for pathological populations, learning this gait pattern was associated with some difficulty and joint discomfort.     

Hemiplegic gait: a kinematic analysis using walking speed as a basis.

The kinematics of treadmill ambulation of stroke patients (N = 9) and healthy subjects (N = 4) was studied at a wide range of different velocities (i.e. 0.25-1.5 m s-1), with a focus on the transverse rotations of the trunk. Video recordings revealed, for both stroke patients and healthy subjects, similar relations between walking speed and stride length as well as stride frequency. The phase difference between pelvic and thoracic rotations (i.e. trunk rotation) and the total range of trunk rotation were almost linearly related to the walking speed. Healthy subjects showed a marked increase in pelvic rotation from 1 to 1.5 m s-1. Using dimensional analysis in a comparison between stroke patients and healthy subjects, invariances in the coordination of gait were found for stride length, stride frequency, pelvic rotation, and trunk rotation. Constant relations were obtained between, on the one hand, dimensionless velocity and, on the other, dimensionless stride length as well as stride frequency. Transitions were found between the velocities 0.75 and 1 m s-1 for dimensionless pelvic rotation and trunk rotation, indicating that, from this velocity range onwards, pelvic swing lengthens the stride: rotations of pelvis, thorax and trunk become tightly coordinated. On the basis of the dimensionless stride length, stride frequency, pelvic rotation and trunk rotation, deficits in the gait of stroke patients could be quantified. It is concluded that walking speed is an important control parameter, which should be used as a basic variable in the evaluation of the gait of stroke patients.     

The effects of walking speed on obstacle crossing in healthy young and healthy older adults

The effects of walking speed and age on the peak external moments generated about the joints of the trailing limb during stance just prior to stepping over an obstacle and on the kinematics of the trailing limb when crossing the obstacle were investigated in 10 healthy young adults (YA) and 10 healthy older adults (OA). The peak hip and knee adduction moments in OA were 21-43% greater than those in YA (p相似文献   

Toe-out gait in patients with knee osteoarthritis partially transforms external knee adduction moment into flexion moment during early stance phase of gait: a tri-planar kinetic mechanism

Altered gait kinematics and kinetics are observed in patients with medial compartment knee osteoarthritis. Although various kinematic adaptations are proposed to be compensatory mechanisms that unload the knee, the nature of these mechanisms is presently unclear. We hypothesized that an increased toe-out angle during early stance phase of gait shifts load away from the knee medial compartment, quantified as the external adduction moment about the knee. Specifically, we hypothesized that by externally rotating the lower limb anatomy, primarily about the hip joint, toe-out gait alters the lengths of ground reaction force lever arms acting about the knee joint in the frontal and sagittal planes and transforms a portion of knee adduction moment into flexion moment. To test this hypothesis, gait data from 180 subjects diagnosed with medial compartment knee osteoarthritis were examined using two frames of reference. The first frame was attached to the tibia (reporting actual toe-out) and the second frame was attached to the laboratory (simulating no-toe-out). Four measures were compared within subjects in both frames of reference: the lengths of ground reaction force lever arms acting about the knee joint in the frontal and sagittal planes, and the adduction and flexion components of the external knee moment. The mean toe-out angle was 11.4 degrees (S.D. 7.8 degrees , range -2.2 degrees to 28.4 degrees ). Toe-out resulted in significant reductions in the frontal plane lever arm (-6.7%) and the adduction moment (-11.7%) in early stance phase when compared to the simulated no-toe-out values. These reductions were coincident with significant increases in the sagittal plane lever arm (+33.7%) and flexion moment (+25.0%). Peak adduction lever arm and moment were also reduced significantly in late stance phase (by -22.9% and -34.4%, respectively) without a corresponding increase in sagittal plane lever arm or flexion moment. These results indicate that toe-out gait in patients with medial compartment knee osteoarthritis transforms a portion of the adduction moment into flexion moment in early stance phase, suggesting that load is partially shifted away from the medial compartment to other structures.     

Training multi-parameter gaits to reduce the knee adduction moment with data-driven models and haptic feedback

The purpose of this study was to evaluate gait retraining for reducing the knee adduction moment. Our primary objective was to determine whether subject-specific altered gaits aimed at reducing the knee adduction moment by 30% or more could be identified and adopted in a single session through haptic (touch) feedback training on multiple kinematic gait parameters. Nine healthy subjects performed gait retraining, in which data-driven models specific to each subject were determined through experimental trials and were used to train novel gaits involving a combination of kinematic changes to the tibia angle, foot progression and trunk sway angles. Wearable haptic devices were used on the back, knee and foot for real-time feedback. All subjects were able to adopt altered gaits requiring simultaneous changes to multiple kinematic parameters and reduced their knee adduction moments by 29-48%. Analysis of single parameter gait training showed that moving the knee medially by increasing tibia angle, increasing trunk sway and toeing in all reduced the first peak of the knee adduction moment with tibia angle changes having the most dramatic effect. These results suggest that individualized data-driven gait retraining may be a viable option for reducing the knee adduction moment as a treatment method for early-stage knee osteoarthritis patients with sufficient sensation, endurance and motor learning capabilities.     

Kinematics and kinetics of the lower extremities of young and elder women during stairs ascent while wearing low and high-heeled shoes

The effect of the heel height on the temporal, kinematic and kinetic parameters was investigated in 16 young and 11 elderly females. Kinematic and kinetic data were collected when the subjects ascended stairs with their preferred speed in two conditions: wearing low-heeled shoes (LHS), and high-heeled shoes (HHS). The younger adults showed more adjustments in forces and moments at the knee and hip in frontal and transverse planes. Besides a few significantly changes in joint forces and moments, the elder group demonstrated longer cycle duration and double stance phase, larger trunk sideflexion and hip internal rotation, less hip adduction while wearing HHS. Most differences in joint motions between two groups were found at the hip and knee either in LHS or HHS condition. Instead, the differences in moment occurred at the hip joint and only in HHS. The interaction of the heel height and age showed the influences of heel height on trunk rotation, hip abduction/adduction, and knee and hip force and moment at the frontal plane depended on age. These phenomena suggest that younger and elderly women adapt their gait and postural control differently during stair ascent (SA) while wearing HHS.     

Females and males use different hip and knee mechanics in response to symmetric military-relevant loads

The purpose of this study was to determine if females and males use different hip and knee mechanics when walking with standardized military-relevant symmetric loads. Fifteen females and fifteen males walked on a treadmill for 2-min at a constant speed under three symmetric load conditions (unloaded: 1.71 kg, medium: 15 kg, heavy: 26 kg). Kinematic and kinetics of the hip and knee were calculated in the sagittal and frontal planes of the dominant limb. In females, hip abduction moments (normalized to total mass) and sagittal knee excursion decreased with increased load (p ≤ 0.024). In males, hip frontal excursion and adduction angle increased with load (p ≤ 0.003). Females had greater peak hip adduction angle than males in the unloaded and medium load conditions (p ≤ 0.036). Across sex, sagittal hip and knee excursion, peak knee extension angle, and peak hip and knee flexion angles increased with increased load (p ≤ 0.005). When normalized to body mass, all peak joint moments increased with each load (p ≤ 0.016) except peak hip adduction moment. When normalized to total mass, peak hip adduction moment and knee flexion, extension, and adduction moments decreased with each load (p < 0.001). While hip frontal plane kinetic alterations to load were only noted in females, kinematic changes were noted in males at the hip and females at the knee. Differences in strategies may increase the risk of hip and knee injuries in females compared to males. This study noted load and sex effects that were previously undetected, highlighting the importance of using military-relevant standardized loads and investigating frontal plane adaptations.     

Effect of centerline-guided walking on gait characteristics in healthy subjects

One of the challenges in collecting ground reaction force (GRF) and moment data for gait analysis is to obtain “good hits” when the subject walks past the forceplates. We examined whether centerline-guided walking would significantly increase the chance of good hits and alter gait characteristics. Thirty-five healthy individuals (age: 37±13 yrs) walked on a walkway with five embedded forceplates at comfortable self-selected speeds under two conditions: (1) free walking and (2) walking along a centerline and avoiding stepping on it. Gait kinematics and GRF were collected using an 8-camera optoelectronic system and five forceplates, respectively. Surface electromyographic (EMG) activity of the rectus femoris, hamstring, gastrocnemius (GAS), and tibialis anterior (TA) were monitored bilaterally. The probability of good hits significantly increased with the centerline-guided walking (p=0.008). Repeated measures MANOVA and follow-up univariate tests revealed no significant differences between the two conditions in any of the spatiotemporal parameters except for a significant increase in step width with centerline walking (p<0.001). Centerline guiding significantly increased peak mediolateral GRF (p<0.001) and hip adduction/abduction and ankle internal/external rotation ranges of motion (p<0.01). In addition, the average EMG activity in GAS and TA during the stance phase significantly increased with the centerline walking (p<0.001). In general, the centerline walking tended to impact women more than men. Centerline-guided walking increases the chance of good hits but biomechanical characteristics of gait in the frontal and transverse planes and EMG activity should be interpreted with caution, especially in women.