The influence of women's age and fall history on foot and lower limb kinematics during transition step descent.

Falls are a major public health concern, with older women being at the greatest risk to experience a fall. Step descent increases the likelihood of a fall injury, yet the influence of age and fall history on lower extremity kinematics have not been extensively studied. The purpose of this study was to examine lower extremity and foot kinematics of women with and without a fall history during single step descent. Hip, knee, and foot kinematics of young women (n = 15, age = 22.6 ± 3.2 years), older women with no recent falls (n = 15, age = 71.6 ± 4.4 years), and older women with a fall history (n = 15, age = 71.5 ± 5.0 years) as they descended a 17 cm step were examined. Differences in initial contact angles and ROM during landing were examined with between group MANOVA tests. Distal foot initial contact angles were not significant between groups. For range of motion, both older groups went through greater hip extension (p = 0.003, partial η2 = 0.25), but less hip adduction (p = 0.002, partial η2 = 0.27) and less lateral midfoot dorsiflexion (p = 0.001, partial η2 = 0.28) than the younger women. The older fall group had reduced knee flexion (p = 0.004, partial η2 = 0.23) than the younger group, and the older non-fallers slightly plantarflexed at the medial midfoot (p = 0.005, partial η2 = 0.23) while the young women dorsiflexed. Thelanding phase ROMdifferences exhibited by the older adult groupsmayincrease the likelihood of a misstep, which may result in a fall.

Foot kinematics in runners with plantar heel pain during running gait.

BACKGROUND: Plantar heel pain associated with plantar fascia pathology (PHP) is one of the most common running overuse injuries. Degeneration and changes in the mechanical properties of the plantar fascia associated with PHP can result in changes in foot kinematics during gait. RESEARCH QUESTION: How do running gait foot kinematics differ between female and male runners with and without PHP? METHODS: Retrospective study of 13 runners with PHP (7 female, 6 male) and a matched group of 13 uninjured runners (6 female, 7 male). A seven-segment foot model was used to quantify six functional articulations (rearfoot complex, lateral and medial midfoot, lateral and medial forefoot, and first metatarsophalangeal). Functional articulation ROM during early, mid, and propulsion running stance subphases was assessed. Two-way ANOVAs and Friedman's two-way ANOVA for ranks tests were conducted for normally distributed variables and non-normally distributed variables, respectively. RESULTS: During early stance, PHP runners demonstrated significantly increased lateral midfoot eversion ROM compared to uninjured runners. During the propulsion phase, male runners with PHP demonstrated increased medial midfoot eversion and dorsiflexion ROM and increased medial forefoot plantar flexion compared to uninjured male runners. Also during propulsion, females with PHP went through significantly less medial forefoot plantar flexion ROM compared to uninjured female runners. SIGNIFICANCE: Given the function of the plantar fascia to assist foot supination, the differences in runners with PHP, which were consistent with increased pronation or inadequate supination, may be the result of insufficient tension during the stance phase of running gait caused by degeneration of the plantar fascia. Further, the significant medial midfoot and medial forefoot group by sex interactions during propulsion suggest that PHP may affect male and female runners differently. Understanding the effect of PHP on foot function during running may aid in the development of future rehabilitation programs and/or treatment outcome assessments.

The Effect of Age and Fall History on Lower Extremity Neuromuscular Function During Descent of a Single Transition Step.

Despite the higher injury rate of falls on steps versus level ground, few studies have examined the influence of age and fall history on step descent. The purpose of this study was to determine the lead and trail limb neuromuscular function (peak joint moments and powers, electromyographic activity) differences between young females (n = 15) and older females with (n = 15) and without (n = 15) a fall history while descending a single step. Trail limb moments and powers did not differ between groups. Lead limb sagittal plane powers at the hip and knee were greater in the young adults. Electromyographic co-activation levels (knee and ankle) were not significantly different between groups. However, peroneal activation was greater in the older groups, which may have assisted in stabilizing the ankle joint in lieu of increased co-activation at the ankle. These results demonstrate consideration of step descent is important in working with older women at risk of falls.

The influence of age and fall history on single transition step kinematics.

Background The risk of falls during locomotion increases with age, and step negotiation is one of the most hazardous types of gait for older adults. Further, a history of a fall is one of the strongest predictors of a future fall; and women fall more frequently, and incur greater medical costs, compared to men. The purpose of the study was to identify lower extremity kinematic factors associated with transition step clearance and foot placement in young women and older women with and without a fall history. Methods Forty-five female participants (15 per group) completed trials that consisted of walking barefoot along a raised walkway at a self-selected speed, descending a 17 cm step, and continued level ground walking. Variables of interest included lead and trail limb minimum step clearance and foot placement, and bilateral lower extremity joint positions at step clearance and at lead foot initial contact. Findings Significant group differences, with large effect sizes, were found in lead foot placement and knee flexion position at initial contact. Both older groups landed more closely to the step and made initial contact with the lead knee in a more flexed position compared to the young group. Interpretation The kinematic differences may be a strategy utilized by older adults to create an early landing to minimize time in single limb stance and compensate for age-related loss of lower extremity strength, range of motion, and/or balance. However, the greater knee flexion may also increase the risk a fall due to lead limb collapse.

Foot joint coupling variability differences between habitual rearfoot and forefoot runners prior to and following an exhaustive run.

As joint coupling variability has been associated with running-related lower extremity injury, the purpose of this study was to identify how variability within the foot may be different between forefoot (FFS) and rearfoot strike (RFS) runners. Identifying typical variability in uninjured runners may contribute to understanding of ideal coordination associated with running foot strike patterns. Fifteen FFS and 15 RFS runners performed a maximal-effort 5 km treadmill run. A 7-segment foot model identified 6 functional articulations (rearfoot, medial and lateral midfoot and forefoot, and 1st metatarsophalangeal) for analysis. Beginning and end of the run motion capture data were analyzed. Vector coding was used to calculate 6 joint couples. Standard deviations of the coupling angles were used to identify variability within subphases of stance (loading, mid-stance, terminal, and pre-swing). Mixed between-within subjects ANOVAs compared differences between the foot strikes, pre and post run. Increased variability was identified within medial foot coupling for FFS and within lateral foot coupling for RFS during loading and mid-stance. The exhaustive run increased variability during mid-stance for both groups. Interpretation. Joint coupling variability profiles for FFS and RFS runners suggest different foot regions have varying coordination needs which should be considered when comparing the strike patterns.

A Principal Components Analysis Approach to Quantifying Foot Clearance and Foot Clearance Variability.

Low foot clearance and high variability may be related to falls risk. Foot clearance is often defined as the local minimum in toe height during swing; however, not all strides have this local minimum. The primary purpose of this study was to identify a nondiscrete measure of foot clearance during all strides, and compare discrete and nondiscrete measures in ability to rank individuals on foot clearance and variability. Thirty-five participants (young adults [n = 10], older fallers [n = 10], older nonfallers [n = 10], and stroke survivors [n = 5]) walked overground while lower extremity 3D kinematics were recorded. Principal components analysis (PCA) of the toe height waveform yielded representation of toe height when it was closest to the ground. Spearman's rank order correlation assessed the association of foot clearance and variability between PCA and discrete variables, including the local minimum. PCA had significant (P < .05) moderate or strong associations with discrete measures of foot clearance and variability. An approximation of the discrete local minimum had a weak association with PCA and other discrete measures of foot clearance. A PCA approach to quantifying foot clearance can be used to identify the behavioral components of toe height when it is closest to the ground, even for strides without a local minimum.

Identifying trippers and non-trippers based on knee kinematics during obstacle-free walking.

Trips are a major cause of falls. Sagittal-plane kinematics affect clearance between the foot and obstacles, however, it is unclear which kinematic measures during obstacle-free walking are associated with avoiding a trip when encountering an obstacle. The purpose of this study was to determine kinematic factors during obstacle-free walking that are related to obstacle avoidance ability. It was expected that successful obstacle avoidance would be associated with greater peak flexion/dorsiflexion and range of motion (ROM), and differences in timing of peak flexion/dorsiflexion during swing of obstacle-free walking for the hip, knee and ankle. Three-dimensional kinematics were recorded as 35 participants (young adults age 18-45 (N = 10), older adults age 65+ without a history of falls (N = 10), older adults age 65+ who had fallen in the last six months (N = 10), and individuals who had experienced a stroke more than six months earlier (N = 5)) walked on a treadmill, under obstacle-free walking conditions with kinematic features calculated for each stride. A separate obstacle avoidance task identified trippers (multiple obstacle contact) and non-trippers. Linear discriminant analysis with sequential feature selection classified trippers and non-trippers based on kinematics during obstacle-free walking. Differences in classification performance and selected features (knee ROM and timing of peak knee flexion during swing) were evaluated between trippers and non-trippers. Non-trippers had greater knee ROM (P = .001). There was no significant difference in classification performance (P = .193). Individuals with reduced knee ROM during obstacle-free walking may have greater difficulty avoiding obstacles.

Lower extremity muscle activity during descent from varying step heights.

During step descent, lower extremity musculature is critical for positioning the foot and ankle for initial contact and stabilizing the structures following contact. Although continuous stair descent has been extensively examined, curb/single transition steps where many injuries occur requires further study. The purpose of this study was to identify the influence of landing strategy and step height on lower extremity muscle activity of uninjured individuals during transition step descent. Twenty-two participants walked along a level walkway, stepped down a single step (heights: 5-cm, 15-cm, 25-cm) landed with the heel or forefoot, and continued walking. Muscle activity of the leading leg's peroneals, tibialis anterior, and medial gastrocnemius were recorded 200 ms before and after initial contact. Two-way Repeated Measures ANOVAs within the three step heights and two landing strategies were run for both the pre- and post-contact periods. Step height by landing strategy interactions existed during the pre-contact periods for all three muscles. During the post-contact period, all muscle activity increased with each step height increment. Additionally, the medial gastrocnemius and tibialis anterior demonstrated significant landing strategy differences. This study highlights the importance of considering both landing strategy and step height when designing or interpreting investigations of transition step negotiation.

Foot and Ankle Kinematics During Descent From Varying Step Heights.

In the general population, one-third of incidences during step negotiation occur during the transition to level walking. Furthermore, falls during curb negotiation are a common cause of injury in older adults. Distal foot kinematics may be an important factor in determining injury risk associated with transition step negotiation. The purpose of this study was to identify foot and ankle kinematics of uninjured individuals during descent from varying step heights. A 7-segment foot model was used to quantify kinematics as participants walked on a level walkway, stepped down a single step (heights: 5 cm, 15 cm, 25 cm), and continued walking. As step height increased, landing strategy transitioned from the rearfoot to the forefoot, and the rearfoot, lateral and medial midfoot, and medial forefoot became more plantar flexed. During weight acceptance, sagittal plane range of motion of the rearfoot, lateral midfoot, and medial and lateral forefoot increased as step height increased. The changes in landing strategy and distal foot function suggest a less stable ankle position at initial contact and increased demand on the distal foot at initial contact and through the weight acceptance phase of transition step negotiation as step height increases.

Reliability of a Seven-Segment Foot Model with Medial and Lateral Midfoot and Forefoot Segments During Walking Gait.

In-vitro and invasive in-vivo studies have reported relatively independent motion in the medial and lateral forefoot segments during gait. However, most current surface-based models have not defined medial and lateral forefoot or midfoot segments. The purpose of the current study was to determine the reliability of a 7-segment foot model that includes medial and lateral midfoot and forefoot segments during walking gait. Three-dimensional positions of marker clusters located on the leg and 6 foot segments were tracked as 10 participants completed 5 walking trials. To examine the reliability of the foot model, coefficients of multiple correlation (CMC) were calculated across the trials for each participant. Three-dimensional stance time series and range of motion (ROM) during stance were also calculated for each functional articulation. CMCs for all of the functional articulations were ≥ 0.80. Overall, the rearfoot complex (leg-calcaneus segments) was the most reliable articulation and the medial midfoot complex (calcaneus-navicular segments) was the least reliable. With respect to ROM, reliability was greatest for plantarflexion/dorsiflexion and least for abduction/adduction. Further, the stance ROM and time-series patterns results between the current study and previous invasive in-vivo studies that have assessed actual bone motion were generally consistent.

The relationship among foot posture, core and lower extremity muscle function, and postural stability.

CONTEXT: Identification of impaired balance as a risk factor for lower extremity injury regardless of injury history has led to subsequent investigation of variables that may adversely affect balance in healthy individuals. OBJECTIVES: To investigate the relationship among core and lower extremity muscle function, foot posture, and balance. DESIGN: Descriptive laboratory study. SETTING: Musculoskeletal injury biomechanics laboratory. PATIENTS OR OTHER PARTICIPANTS: A total of 108 individuals (40 men, 68 women; age = 22.8 ± 4.7 years, height = 168.5 ± 10.4 cm, mass = 69.9 ± 13.3 kg) participated in the study. MAIN OUTCOME MEASURE(S): Core endurance was assessed during 1 time-to-failure trial, and isometric hip and ankle strength were assessed using a handheld dynamometer and isokinetic dynamometer, respectively. Foot structure was quantified using the digital photographic measurement method. Single-limb-stance time to boundary was assessed using a force plate during an eyes-closed condition. Hierarchical multiple regression analyses were performed to predict balance using lower extremity strength, foot posture, and core endurance. RESULTS: Foot posture (ß = -0.22, P = .03) and ankle-inversion strength (ß = -0.29, P = .006) predicted mediolateral balance. Increasing arch posture and ankle-inversion strength were associated with decreased mediolateral single-limb-stance balance. CONCLUSIONS: Increasing arch height was associated with decreased mediolateral control of single-limb stance. The relationship between time to boundary and injury risk, however, has not been explored. Therefore, the relationship between increasing arch height and injury due to postural instability cannot be determined from this study. If authors of future prospective studies identify a relationship between decreased time to boundary and increased injury risk, foot structure may be an important variable to assess during preparticipation physical examinations. The relationship between increasing ankle-inversion strength and decreased balance may require additional study to further elucidate the relationship between ankle strength and balance.

Effect of patellofemoral pain on strength and mechanics after an exhaustive run.

PURPOSE: To investigate the effects of an exhaustive run on trunk and lower extremity strength and mechanics in patients with and without patellofemoral pain (PFP), we hypothesized that strength would decrease and mechanics would change after the exhaustive run. METHODS: Nineteen subjects with PFP and 19 controls participated (10 men and 9 women per group). Lower extremity and trunk mechanics during running, body mass-normalized strength, and pain assessments before and after an exhaustive run were quantified. A repeated-measures ANOVA was used to assess group differences and exhaustion-related changes (P < 0.05), with t-test post hoc analyses performed when significant interactions were identified (P < 0.0125). RESULTS: Pain significantly increased with the exhaustive run in the PFP group (P = 0.021). Hip strength was reduced after the exhaustive run, more so in those with PFP (abduction: before = 0.384 ± 0.08, after = 0.314 ± 0.08, P < 0.001; external rotation: before = 0.113 ± 0.02, after = 0.090 ± 0.02, P < 0.001). Persons with PFP also demonstrated increased knee flexion (before = 41.6° ± 5.5°, after = 46.9° ± 7.5°, P < 0.001), hip flexion (before = 30.4° ± 6.8°, after = 42.5° ± 9.7°, P < 0.001), and anterior pelvic tilt (before = 7.2° ± 5.1°, after = 13.3° ± 6.7°, P = 0.001) after the exhaustive run compared to controls. Trunk flexion increased in both PFP (before = 13.09° ± 6.2°, after = 16.31° ± 5.3°, P < 0.001) and control (before = 1393° ± 4.7°, after = 15.99° ± 5.9°, P < 0.001) groups. Hip extension (before = -2.09 ± 0.49 N · m · kg(-1), after = -2.49 ± 0.54 N · m · kg(-1), P = 0.002) moments increased only in subjects with PFP. CONCLUSIONS: Exhaustive running results in reduced hip strength in subjects with PFP; however, this did not result in changes to hip internal rotation or adduction kinematics. Kinematic and kinetic changes after the exhaustive run are more indicative of compensatory changes to reduce pain. Increasing trunk flexion during running might provide pain relief during running; however, reducing anterior pelvic tilt may also warrant attention during treatment.

The effect of boundary shape and minima selection on single limb stance postural stability.

The effect of time-to-boundary minima selection and stability limit definition was investigated during eyes open and eyes closed condition single-limb stance postural stability. Anteroposterior and mediolateral time-to-boundary were computed using the mean and standard deviation (SD) of all time-to-boundary minima during a trial, and the mean and SD of only the 10 absolute time-to-boundary minima. Time-to-boundary with rectangular, trapezoidal, and multisegmented polygon defined stability limits were also calculated. Spearman's rank correlation coefficient test results revealed significant medium-large correlations between anteroposterior and mediolateral time-to-boundary scores calculated using both the mean and SD of the 10 absolute time-to-boundary minima and of all the time-to-boundary minima. Friedman test results revealed significant mediolateral time-to-boundary differences between boundary shape definitions. Follow-up Wilcoxon signed rank test results revealed significant differences between the rectangular boundary shape and both the trapezoidal and multisegmented polygon shapes during the eyes open and eyes closed conditions when both the mean and the SD of the time-to-boundary minima were used to represent postural stability. Significant differences were also revealed between the trapezoidal and multisegmented polygon definitions during the eyes open condition when the SD of the time-to-boundary minima was used to represent postural stability. Based on these findings, the overall results (i.e., stable versus unstable participants or groups) of studies computing postural stability using different minima selection can be compared. With respect to boundary shape, the trapezoid or multisegmented polygon shapes may be more appropriate than the rectangular shape as they more closely represent the anatomical shape of the stance foot.

Hip muscle activity during 3 side-lying hip-strengthening exercises in distance runners.

CONTEXT: Lower extremity overuse injuries are associated with gluteus medius (GMed) weakness. Understanding the activation of muscles about the hip during strengthening exercises is important for rehabilitation. OBJECTIVE: To compare the electromyographic activity produced by the gluteus medius (GMed), tensor fascia latae (TFL), anterior hip flexors (AHF), and gluteus maximus (GMax) during 3 hip-strengthening exercises: hip abduction (ABD), hip abduction with external rotation (ABD-ER), and clamshell (CLAM) exercises. DESIGN: Controlled laboratory study. SETTING: Laboratory. PATIENTS OR OTHER PARTICIPANTS: Twenty healthy runners (9 men, 11 women; age = 25.45 ± 5.80 years, height = 1.71 ± 0.07 m, mass = 64.43 ± 7.75 kg) participated. INTERVENTION(S): A weight equal to 5% body mass was affixed to the ankle for the ABD and ABD-ER exercises, and an equivalent load was affixed for the CLAM exercise. A pressure biofeedback unit was placed beneath the trunk to provide positional feedback. MAIN OUTCOME MEASURE(S): Surface electromyography (root mean square normalized to maximal voluntary isometric contraction) was recorded over the GMed, TFL, AHF, and GMax. RESULTS: Three 1-way, repeated-measures analyses of variance indicated differences for muscle activity among the ABD (F(3,57) = 25.903, P < .001), ABD-ER (F(3,57) = 10.458, P < .001), and CLAM (F(3,57) = 4.640, P = .006) exercises. For the ABD exercise, the GMed (70.1 ± 29.9%), TFL (54.3 ± 19.1%), and AHF (28.2 ± 21.5%) differed in muscle activity. The GMax (25.3 ± 24.6%) was less active than the GMed and TFL but was not different from the AHF. For the ABD-ER exercise, the TFL (70.9 ± 17.2%) was more active than the AHF (54.3 ± 24.8%), GMed (53.03 ± 28.4%), and GMax (31.7 ± 24.1%). For the CLAM exercise, the AHF (54.2 ± 25.2%) was more active than the TFL (34.4 ± 20.1%) and GMed (32.6 ± 16.9%) but was not different from the GMax (34.2 ± 24.8%). CONCLUSIONS: The ABD exercise is preferred if targeted activation of the GMed is a goal. Activation of the other muscles in the ABD-ER and CLAM exercises exceeded that of GMed, which might indicate the exercises are less appropriate when the primary goal is the GMed activation and strengthening.

Custom-molded foot-orthosis intervention and multisegment medial foot kinematics during walking.

CONTEXT: Foot-orthosis (FO) intervention to prevent and treat numerous lower extremity injuries is widely accepted clinically. However, the results of quantitative gait analyses have been equivocal. The foot models used, participants receiving intervention, and orthoses used might contribute to the variability. OBJECTIVE: To investigate the effect of a custom-molded FO intervention on multisegment medial foot kinematics during walking in participants with low-mobile foot posture. DESIGN: Crossover study. SETTING: University biomechanics and ergonomics laboratory. PATIENTS OR OTHER PARTICIPANTS: Sixteen participants with low-mobile foot posture (7 men, 9 women) were assigned randomly to 1 of 2 FO groups. INTERVENTION(S): After a 2-week period to break in the FOs, individuals participated in a gait analysis that consisted of 5 successful walking trials (1.3 to 1.4 m/s) during no-FO and FO conditions. MAIN OUTCOME MEASURE(S): Three-dimensional displacements during 4 subphases of stance (loading response, midstance, terminal stance, preswing) were computed for each multisegment foot model articulation. RESULTS: Repeated-measures analyses of variance (ANOVAs) revealed that rearfoot complex dorsiflexion displacement during midstance was greater in the FO than the no-FO condition (F(1,14) = 5.24, P = .04, partial η(2) = 0.27). Terminal stance repeated-measures ANOVA results revealed insert-by-insert condition interactions for the first metatarsophalangeal joint complex (F(1,14) = 7.87, P = .01, partial η(2) = 0.36). However, additional follow-up analysis did not reveal differences between the no-FO and FO conditions for the balanced traditional orthosis (F(1,14) = 4.32, P = .08, partial η(2) = 0.38) or full-contact orthosis (F(1,14) = 4.10, P = .08, partial η(2) = 0.37). CONCLUSIONS: Greater rearfoot complex dorsiflexion during midstance associated with FO intervention may represent improved foot kinematics in people with low-mobile foot postures. Furthermore, FO intervention might partially correct dysfunctional kinematic patterns associated with low-mobile foot postures.

The effects of single-leg landing technique on ACL loading.

Anterior Cruciate Ligament (ACL) injury is one of the most serious and costly injuries of the lower extremity, occurring more frequently in females than males. Injury prevention training programs have reported the ability to reduce non-contact ACL injury occurrence. These programs have also been shown to alter an athletes' lower extremity position at initial contact with the ground and throughout the deceleration phase of landing. The purpose of this study was to determine the influence of single-leg landing technique on ACL loading in recreationally active females. Participants were asked to perform "soft" and "stiff" drop landings. A series of musculoskeletal models were then used to estimate muscle, joint, and ACL forces. Dependent t-tests were conducted to investigate differences between the two landing techniques (p<0.05). Instructing participants to land 'softly' resulted in a significant decrease in peak ACL force (p=0.05), and a significant increase in hip and knee flexion both at initial contact (IC) and the time of peak ACL force (F(PACL)). These findings suggest that altering landing technique using simple verbal instruction may result in lower extremity alignment that decreases the resultant load on the ACL. Along with supporting the findings of reduced ACL force with alterations in sagittal plane landing mechanics in the current literature, the results of this study suggest that simple verbal instruction may reduce the ACL force experienced by athletes when landing.

A digital photographic measurement method for quantifying foot posture: validity, reliability, and descriptive data.

CONTEXT: Although abnormal foot posture long has been associated with lower extremity injury risk, the evidence is equivocal. Poor intertester reliability of traditional foot measures might contribute to the inconsistency. OBJECTIVES: To investigate the validity and reliability of a digital photographic measurement method (DPMM) technology, the reliability of DPMM-quantified foot measures, and the concurrent validity of the DPMM with clinical-measurement methods (CMMs) and to report descriptive data for DPMM measures with moderate to high intratester and intertester reliability. DESIGN: Descriptive laboratory study. SETTING: Biomechanics research laboratory. PATIENTS OR OTHER PARTICIPANTS: A total of 159 people participated in 3 groups. Twenty-eight people (11 men, 17 women; age  =  25 ± 5 years, height  =  1.71 ± 0.10 m, mass  =  77.6 ± 17.3 kg) were recruited for investigation of intratester and intertester reliability of the DPMM technology; 20 (10 men, 10 women; age  =  24 ± 2 years, height  =  1.71 ± 0.09 m, mass  =  76 ± 16 kg) for investigation of DPMM and CMM reliability and concurrent validity; and 111 (42 men, 69 women; age  =  22.8 ± 4.7 years, height  =  168.5 ± 10.4 cm, mass  =  69.8 ± 13.3 kg) for development of a descriptive data set of the DPMM foot measurements with moderate to high intratester and intertester reliabilities. INTERVENTION(S): The dimensions of 10 model rectangles and the 28 participants' feet were measured, and DPMM foot posture was measured in the 111 participants. Two clinicians assessed the DPMM and CMM foot measures of the 20 participants. MAIN OUTCOME MEASURE(S): Validity and reliability were evaluated using mean absolute and percentage errors and intraclass correlation coefficients. Descriptive data were computed from the DPMM foot posture measures. RESULTS: The DPMM technology intratester and intertester reliability intraclass correlation coefficients were 1.0 for each tester and variable. Mean absolute errors were equal to or less than 0.2 mm for the bottom and right-side variables and 0.1° for the calculated angle variable. Mean percentage errors between the DPMM and criterion reference values were equal to or less than 0.4%. Intratester and intertester reliabilities of DPMM-computed structural measures of arch and navicular indices were moderate to high (>0.78), and concurrent validity was moderate to strong. CONCLUSIONS: The DPMM is a valid and reliable clinical and research tool for quantifying foot structure. The DPMM and the descriptive data might be used to define groups in future studies in which the relationship between foot posture and function or injury risk is investigated.

Normalizing hip muscle strength: establishing body-size-independent measurements.

OBJECTIVE: To investigate the effectiveness of computing body-size-independent hip strength measures using muscle-specific allometric scaling and ratio standard normalization methods. DESIGN: Cross-sectional study. SETTING: University laboratory. PARTICIPANTS: A convenience sample of healthy participants (N=113; 42 men, 71 women). INTERVENTIONS: Not applicable. MAIN OUTCOME MEASURES: Anthropometric measurements of the leg and thigh were obtained, and maximal hip strength was tested (medial and lateral rotation, abduction, adduction, flexion, extension). Strength was measured isometrically as force (kg) and then converted to torque (Nm). RESULTS: The allometric scaling analysis resulted in exponents for normalizing body mass (BM) in each muscle group assessed. In addition, a 6-muscle average exponent was also computed (bavg) for force (men, .554; women, .335) and torque (men, .792; women, .482). The nonsignificant results of the linear regression analysis revealed that normalizing hip strength to BM(bavg) (hip strength/BM(bavg)) effectively removed the influence of BM on force and torque. However, sex should be factored into analyses of allometric scaling because men have higher b-values than women for both force and torque. The linear regression analyses also demonstrated that force normalized to BM (P=.162-.895) and torque normalized to BM × Height (P=.146-.889) were body-size-independent measures. Force normalized to BM°·67 (P=.001-.191) and body mass index (BMI) (P=<.001-.066), and torque normalized to BM (P=.004-.415) and BMI (P<.001) were significantly related to BM and therefore were not body-size independent. CONCLUSIONS: Normalizing force and torque to BM(bavg) is the most effective method of removing body-size dependence and allowing comparisons of persons with differing body sizes.

The effect of low-mobile foot posture on multi-segment medial foot model gait kinematics.

A number of in vitro, invasive in vivo, and non-invasive marker based multi-segment foot models (MSFMs) have reported significant motion in the articulations distal to the calcaneus during gait. Few studies, however, have applied a MSFM to the investigation of the effect of foot posture on gait kinematics. Differences in stance phase kinematics between participants with low-mobile (LMF) (n=11) versus "typical" (TYPF) (n=11) foot postures were investigated using a multi-segment medial foot model. Three-dimensional position and stance phase excursions of four functional articulations (rearfoot complex [RC], calcaneonavicular complex [CNC], medial forefoot, first metatarsophalangeal complex) were quantified using an eight optical camera motion analysis system (Vicon Motus, Vicon Motions Systems, Centennial, CO) and a custom written software program (Matlab 7.0.1, The MathWorks, Natick, MA), respectively. Excursions during four subphases of stance phase (loading response, midstance, terminal stance, pre-swing) at each of the functional articulations were compared using multivariate analyses of variance (alpha

The effect of 6 weeks of custom-molded foot orthosis intervention on postural stability in participants with >or=7 degrees of forefoot varus.

OBJECTIVE: Postural stability (PS) was assessed in a group of participants with >or=7 degrees of forefoot varus (FV) after 6 weeks of custom-molded functional foot orthosis (FO) intervention to investigate the effect of FO intervention in a population that may have decreased PS due to their foot structure. DESIGN: A force platform was used to assess right and left single-limb stance position and eyes open and eyes closed condition PS. SETTING: PS was assessed in a biomechanics research laboratory. PARTICIPANTS: Twelve participants with >or=7 degrees of FV (MFV) and 5 participants with <7 degrees of FV (LFV) participated in the study. INTERVENTIONS: PS of the MFV group was assessed initially when FOs were received and after 6 weeks of FO intervention. The LFV group PS was assessed during initial and 6-week testing sessions. MAIN OUTCOME MEASURES: The root mean square of the center of pressure velocity was used to quantify single-limb stance PS during no FO and FO conditions. RESULTS: LFV group PS did not change significantly (P=0.829) over the 6-week time period. Significant improvement was, however, reported in the MFV group anteroposterior (P=0.003) and mediolateral (P=0.032) PS at the 6-week assessment versus the initial assessment during both the noFO and FO conditions. CONCLUSIONS: Six weeks of FO intervention may significantly improve PS in participants with >or=7 degrees of FV both when wearing FOs and when not wearing FOs.