The effects of adiposity, muscular strength, cardiorespiratory fitness, and fatigue on gait biomechanics in overweight and obese children.

BACKGROUND: Obesity rates continue to increase in the child population. Muscular strength, cardiorespiratory fitness, and fatigue can potentially affect joint stresses in obese children. The purposes are to examine: (1) the relationship between cardiorespiratory fitness and the change in joint stress pre- to post-fatigue; (2) the predictive value of fitness, adiposity, and muscular strength on joint stresses in fatigued and non-fatigued states; and, (3) the relationships between % body fat from skinfold and air displacement plethysmography. METHODS: Twenty-seven children, with body mass index above the 85th percentile for their age participated in this study. Lower limb joint moments were recorded before and after a fatiguing Progressive Aerobic Cardiovascular Endurance Run protocol. Linear regression was used to assess the relationship between (1) fitness and change in joint stress pre- to post-fatigue, and (2) measures of %body fat using skinfold and plethysmography. Furthermore, Bland-Altman analysis quantified the agreement between measured adiposity using the two methods. FINDINGS: The strongest relationship was observed between fitness and the change in the knee extensor moment pre- to post-fatigue (R2 = 0.24). Regardless of fatigue state, adiposity and strength were identified as the strongest predictors of joint moments. Skinfold estimates were moderately predictive (R2 = 0.56) of %body fat from air displacement plethysmography, and these two measures demonstrated instrument agreement with no proportional bias. INTERPRETATION: Fitness level is not related to changes in biomechanics pre- to post-fatigue in overweight and obese children. Adiposity and lower extremity strength most strongly influenced joint moments in the frontal and sagittal planes.

Changes in Gait over a 30-min Walking Session in Obese Females.

PURPOSE: This study assessed the biomechanical gait changes in obese and normal-weight female adult subjects after a commonly recommended 30-min walking session. Hip and knee adduction and extensor moments, which are the primary modulators of frontal and sagittal plane load distribution, were hypothesized to increase in obese females after a 30-min walking period, resulting in more stress across the hip and knee joint. METHODS: Ten obese (37.7 ± 4.8 yr of age, body mass index [BMI] = 36.1 ± 4.2 kg·m) and 10 normal-weight control female subjects (38.1 ± 4.5 yr of age, BMI = 22.6 ± 2.3 kg·m) walked 30 min continuously on the treadmill at their self-selected speed. V˙O2max was estimated using Ebbeling protocol. A three-dimensional pre- and posttreadmill gait analysis was conducted using infrared markers and force plates to calculate hip and knee moments. RESULTS: Knee extensor moments increased in both obese, pretreadmill (0.54 ± 0.28 N·m·kg) to posttreadmill (0.78 ± 0.43 N·m·kg) (P = 0.01), and control subjects, pretreadmill (0.57 ± 0.34 N·m·kg) to posttreadmill (0.80 ± 0.49 N·m·kg) (P = 0.02). Hip extensor moments decreased for both obese and control subjects. Knee adduction moments did not change in either obese or control subjects. Knee extensor and adductor moments showed good to moderate relationships with V˙O2max, but not BMI or waist circumference. CONCLUSION: Obese and normal-weight subjects experienced an increase in knee extensor moments after 30 min of walking similarly; therefore, clinicians do not need special consideration for obese individuals when recommending 30-min walking sessions. Fitness may be the important factor in judging the implications of exercise on joint mechanics and parameters of a walking program.

Do fitness and fatigue affect gait biomechanics in overweight and obese children?

The purpose of this study was to determine how an overweight or obese child's cardiorespiratory fitness level and a state of fatigue affect gait biomechanics. METHODS: Using a three-dimensional motion analysis system, twenty-nine (female and male) overweight and obese children aged 8-11 years walked on force plates before and after being fatigued from the Progressive Aerobic Cardiovascular Endurance Run (PACER) protocol. Joint moments were calculated for the knee and hip in the frontal and sagittal planes. RESULTS: In a non-fatigued state, peak hip and knee adductor moments showed a negative relationship with cardiorespiratory fitness level (R2=0.26, 0.26). After the subjects were fatigued, peak hip extensor (p=0.02), peak knee extensor moments (p=0.02) and peak knee adductor moments (p=0.01) showed a significant increase. CONCLUSION: This trend illustrates that as an overweight or obese individual's fitness improves, the lower limb joint moments in the frontal plane decrease when walking. However, with the introduction of cardiorespiratory fatigue, lower limb joint moments tend to increase in the frontal and sagittal planes. Increased joint stress may have potential implications for obese children performing physical activity, as well as for clinicians who are attempting to intervene in the cycle of obesity.

Short and long-term effects of gait retraining using real-time biofeedback to reduce knee hyperextension pattern in young women.

The use of real-time biofeedback has been shown to enable individuals to make changes to their gait patterns. It remains unknown whether the short-term improvements reported in previous studies are retained in the longer term. In this study, the paradigm used to investigate the short and long-term effects of real-time biofeedback was modifying knee range of motion during gait to prevent knee hyperextension in women. The purpose of this study was to investigate the short-term (1-month follow up) and long-term (8-month follow up) effects of a gait retraining program using real-time biofeedback to correct knee hyperextension in young women. Seventeen healthy women, ages 18-35 years, with asymptomatic knee hyperextension underwent a three-week (6 sessions) treadmill gait retraining program. Real-time feedback of kinematic data (Visual 3D) was provided during treadmill training. Knee extension range of motion was monitored during overground gait evaluations and training sessions. Gait evaluations were performed pretraining, posttraining (2days after), and 1-month, and 8-month after the last training session. This study showed significant reduction in knee hyperextension patterns immediately following training (mean±SD, 10.9°±4°), and at 1-month (7.5°±5°) and 8-month (6.3°±3.5°) follow ups. There was an increase in knee extension between posttraining and 1-month follow up (3.4°±5°). Reduction in knee hyperextension range of motion was retained at 8-month follow up evaluation. The present study shows the effects of real-time biofeedback in facilitating the acquisition and retention of proficiency in reducing knee hyperextension gait patterns, documenting that the retention is sustained for up to 8 months.

Biomechanical loads during common rehabilitation exercises in obese individuals.

BACKGROUND: Squats and lunges are commonly prescribed rehabilitation exercises used to improve performance across a wide spectrum of patient populations. However, biomechanical studies have mainly examined young, normal weight populations performing these exercises at a difficulty level potentially too challenging for obese individuals. Understanding how obesity and different levels of difficulty affect lower extremity biomechanics could help to inform rehabilitation approaches used for obese individuals. PURPOSE: The purpose of this study was to analyze and compare the lower extremity kinematics and kinetics in obese and normal weight females during performance of progressively more difficult squat and lunge exercises. STUDY DESIGN: Cross-sectional study design. METHODS: Ten obese females (mean age, 37.4 years; BMI 39.2 ± 3.7 kg/m(2)) and ten normal-weight, age-matched female controls (38.1 years, BMI < 23 kg/m(2)) volunteered for the study. Each group performed two exercises, each in three different iterations: squatting at three standardized knee angles (60°, 70°, and 80°) and lunging at three standardized distances (1.0, 1.1, and 1.2 times tibial length). Three dimensional motion analysis using infrared markers and force plates was used to calculate range of motion as well as hip, knee, ankle and support moments (normalized for body weight). A repeated measures ANOVA model was used to determine between and within group differences. RESULTS: Support moments were higher in obese females for squat 70° (p=0.03) and 80° (p=0.01). Ankle extensor moments were higher in obese females for squat 80° (p=0.04). During lunge at all levels (1.0, 1.1, and 1.2), hip extensor moments were higher in obese subjects (p=0.004, 0.003, and 0.007 respectively). Within group, the support moments were significantly higher during squat 80° than squat 60° (p=0.01) in obese females. A non-linear relationship was found between hip moments and BMI during squat 60°, 70°, and 80°. CONCLUSION: During two commonly prescribed rehabilitation exercises (squat and lunge), there were significantly greater support moments in obese individuals compared to normal controls. The non-linear associations between kinetic and anthropometric measures make the assessment of how best to approach exercise in obese individuals challenging. LEVEL OF EVIDENCE: Level 3.

Intensive Gait Training for Older Adults with Symptomatic Knee Osteoarthritis.

OBJECTIVE: The objective of this study was to determine whether individualized gait training is more effective than usual care for reducing mobility disability and pain in individuals with symptomatic knee osteoarthritis. DESIGN: Adults aged 60 yrs or older with symptomatic knee osteoarthritis and mobility limitations were randomized to physical therapist-directed gait training on an instrumented treadmill, with biofeedback individualized to optimize knee movements, biweekly for 3 mos or usual care (control). Mobility disability was defined using Late Life Function and Disability Index Basic Lower Limb Function score (primary); mobility limitations, using timed 400-m walk, chair-stand, and stair-climb tests; and symptoms, using the Knee Injury/Osteoarthritis Outcome Score at baseline, as well as at 3, 6, and 12 mos. The analyses used longitudinal mixed models. RESULTS: There were no significant intergroup differences between the 35 gait-training (74.3% women; age, 69.7 ± 8.2 yrs) and 21 control (57.1% women; age, 68.9 ± 6.5 yrs) participants at baseline. At 3 mos, the gait-training participants had greater improvement in mobility disability (4.3 ± 1.7; P = 0.0162) and symptoms (8.6 ± 4.1; P = 0.0420). However, there were no intergroup differences detected for pain, 400-m walk, chair-stand, or stair-climb times at 3 mos or for any outcomes at 6 or 12 mos. CONCLUSIONS: Compared with usual care, individualized gait training resulted in immediate improvements in mobility disability knee symptoms in adults with symptomatic knee osteoarthritis, but these effects were not sustained.

Long-term results of tibialis anterior tendon transfer for relapsed idiopathic clubfoot treated with the Ponseti method: a follow-up of thirty-seven to fifty-five years.

BACKGROUND: Relapse of idiopathic clubfoot deformity after treatment can be effectively managed with repeat casting and tibialis anterior tendon transfer during early childhood. We evaluated the long-term effects on adult foot function after tibialis anterior tendon transfer for relapsed idiopathic clubfoot deformity during childhood. METHODS: Thirty-five patients (sixty clubfeet) in whom idiopathic clubfoot was treated with the Ponseti method from 1950 to 1967 were followed. At an average age of forty-seven years (range, thirty-seven to fifty-five years), the patients underwent a detailed musculoskeletal examination, radiographic evaluation, pedobarographic analysis, and surface electromyography (EMG). They also completed three quality-of-life patient questionnaires. RESULTS: Fourteen patients (twenty-five clubfeet, 42%) had required repeat casting and tibialis anterior tendon transfer in childhood for relapsed clubfoot deformity after initial casting and served as the study group. Twenty-one patients (thirty-five clubfeet, 58%) were successfully treated with initial casting without relapse (the reference group). No patient in either group had subsequent relapse or required additional operative intervention associated with clubfoot deformity. The mean ankle dorsiflexion was similar between the groups. Radiographically, the tendon transfer group showed a smaller mean anteroposterior talocalcaneal angle and slightly more talar flattening than the reference group with no associated clinical differences. Peak pressures, total force distribution, and surface EMG results were not significantly different between the groups. Outcome questionnaires demonstrated no significant difference between the groups. CONCLUSIONS: Tibialis anterior tendon transfer is very effective at preventing additional relapse of deformity without affecting long-term foot function of patients with idiopathic clubfoot.

Home-based treadmill training to improve gait performance in persons with a chronic transfemoral amputation.

OBJECTIVE: To investigate the effectiveness of a home-based multiple-speed treadmill training program to improve gait performance in persons with a transfemoral amputation (TFA). DESIGN: Repeated measures. SETTING: Research laboratory. PARTICIPANTS: Individuals with a TFA (N=8) who had undergone a unilateral amputation at least 3 years prior as a result of limb trauma or cancer. INTERVENTION: Home-based treadmill walking for a total of 30 minutes a day, 3 days per week for 8 weeks. Each 30-minute training session involved 5 cycles of walking for 2 minutes at 3 speeds. MAIN OUTCOME MEASURES: Participants were tested pretraining and after 4 and 8 weeks of training. The primary measures were temporal-spatial gait performance (symmetry ratios for stance phase duration and step length), physiological gait performance (energy expenditure and energy cost), and functional gait performance (self-selected walking speed [SSWS], maximum walking speed [MWS], and 2-minute walk test [2MWT]). RESULTS: Eight weeks of home-based training improved temporal-spatial gait symmetry at SSWS but not at MWS. A relative interlimb increase in stance duration for the prosthetic limb and proportionally greater increases in step length for the limb taking shorter steps produced the improved symmetry. The training effect was significant for the step length symmetry ratio within the first 4 weeks of the program. Energy expenditure decreased progressively during the training with nearly 10% improvement observed across the range of walking speeds. SSWS, MWS, and 2MWT all increased by 16% to 20%. CONCLUSIONS: Home-based treadmill walking is an effective method to improve gait performance in persons with TFA. The results support the application of training interventions beyond the initial rehabilitation phase, even in individuals considered highly functional.

Estimates of gastrocnemius muscle length during simulated pathological gait.

The purpose of this study was to compare estimates of gastrocnemius muscle length (GML) obtained using a segmented versus straight-line model in children. Kinematic data were acquired on eleven typically developing children as they walked under the following conditions: normal gait, crouch gait, equinus gait, and crouch with equinus gait. Maximum and minimum GML, and GML change were calculated using two models: straight-line and segmented. A two-way RMANOVA was used to compare GML characteristics. Results indicated that maximum GML and GML change during simulated pathological gait patterns were influenced by model used to calculate gastrocnemius muscle length (interaction: P = .004 and P = .026). Maximum GML was lower in the simulated gait patterns compared with normal gait (P < .001). Maximum GML was higher with the segmented model compared with the straight-line model (P = .030). Using either model, GML change in equinus gait and crouch with equinus gait was lower compared with normal gait (P < .001). Overall, minimum GML estimated with the segmented model was higher compared with the straight-line model (P < .01). The key findings of our study indicate that GML is significantly affected by both gait pattern and method of estimation. The GML estimates tended to be lower with the straight-line model versus the segmented model.

Morbid obesity may increase dislocation in total hip patients: a biomechanical analysis.

BACKGROUND: Obesity has reached epidemic proportions in the United States. Recently, obesity, especially morbid obesity, has been linked to increased rates of dislocation after THA. The reasons are unclear. Soft tissue engagement caused by increased thigh girth has been proposed as a possible mechanism for decreased joint stability. QUESTIONS/PURPOSES: We asked (1) whether thigh soft tissue impingement could decrease THA stability, and if so, at what level of BMI this effect might become evident; and (2) how THA construct factors (eg, head size, neck offset, cup abduction) might affect stability in the morbidly obese. METHODS: The obesity effect was explored by augmenting a physically validated finite element model of a total hip construct previously comprising just implant hardware and periarticular (capsular) soft tissue. The model augmentation involved using anatomic and anthropometric data to include graded levels of increased thigh girth. Parametric computations were run to assess joint stability for two head sizes (28 and 36 mm), for normal versus high neck offset, and for multiple cup abduction angles. RESULTS: Thigh soft tissue impingement lowered the resistance to dislocation for BMIs of 40 or greater. Dislocation risk increased monotonically above this threshold as a function of cup abduction angle, independent of hardware impingement events. Increased head diameter did not substantially improve joint stability. High-offset necks decreased the dislocation risk. CONCLUSIONS: Excessive obesity creates conditions that compromise stability of THAs. Given such conditions, our model suggests reduced cup abduction, high neck offset, and full-cup coverage would reduce the risks of dislocation events.

Association between chair stand strategy and mobility limitations in older adults with symptomatic knee osteoarthritis.

OBJECTIVE: To determine which lower limb strength and joint kinetic and kinematic parameters distinguish sit-to-stand (STS) performance of older adults with symptomatic knee osteoarthritis (OA) with higher and lower chair stand time. DESIGN: Cross-sectional. SETTING: Motion analysis laboratory. PARTICIPANTS: Individuals (N=49; 26 men, 23 women) aged 50 to 79 years (mean ± SD age, 64.7±8.1y) with radiographic knee OA and daily symptoms, stratified by chair stand times. INTERVENTIONS: Not applicable. MAIN OUTCOME MEASURES: Lower limb strength and STS strategy. RESULTS: The chair stand times (mean ± SD) in the high-, moderate-, and low-functioning groups in men were 6.5±0.7, 8.6±0.7, and 11.5±1.3 seconds, respectively, and in women were 7.6±1.2, 10.0±0.5, and 12.8±1.8 seconds, respectively. Chair stand time (P=.0391) and all measures of lower limb strength (all P<.0001) differed by sex. In men, no strength measure differed between groups, whereas in women hip abductor strength on the more affected side differed between groups. In men, sagittal hip range of motion (ROM) (P=.0122) differed between groups, and there was a trend toward a difference in sagittal knee power (P=.0501) during STS, while in women only sagittal knee ROM (P=.0392) differed between groups. CONCLUSIONS: Higher- and lower-functioning adults with symptomatic knee OA appear to use different strategies when standing from a chair. Higher-functioning men flexed more at the hip and produced greater knee power than lower-functioning men. Higher-functioning women used less knee flexion than lower-functioning women. Since STS is an important mobility task, these parameters may serve as foci for rehabilitation aimed at reducing mobility limitations.

Pregnancy leads to lasting changes in foot structure.

OBJECTIVE: Women are disproportionately affected by musculoskeletal disorders. Parous women seem to be at a particularly elevated risk for structural and functional changes in the lower limbs. The combination of increased weight on the joints with potentially greater laxity during pregnancy could lead to permanent structural changes in the feet. Although arches may become lax during pregnancy, it is unknown whether the changes persist. The objective of this study was to determine whether arch height loss persists postpartum. DESIGN: Forty-nine women completed this longitudinal study. Static and dynamic arch measurements were collected in the first trimester and at 19 wks postpartum. Linear mixed models were used to determine whether outcome measures significantly changed overall or by parity. RESULTS: Arch height and rigidity indices significantly decreased, with concomitant increases in foot length and arch drop. The first pregnancy accounted for the reduction in arch rigidity and the increases in foot length and arch drop. No changes were detected in the center of pressure excursion index. CONCLUSIONS: Pregnancy seems to be associated with a permanent loss of arch height, and the first pregnancy may be the most significant. These changes in the feet could contribute to the increased risk for musculoskeletal disorders in women. Further research should assess the efficacy of rehabilitative interventions for prevention of pregnancy-related arch drop.

Abdomen-thigh contact during forward reaching tasks in obese individuals.

During seated forward reaching tasks in obese individuals, excessive abdominal tissue can come into contact with the anterior thigh. This soft tissue apposition acts as a mechanical restriction, altering functional biomechanics at the hip, and causing difficulty in certain daily activities such as bending down, or picking up objects from the floor. The purpose of the study was to investigate the contact forces and associated moments exerted by the abdomen on the thigh during seated forward-reaching tasks in adult obese individuals. Ten healthy subjects (age 58.1 ± 4.4) with elevated BMI (39.04 ± 5.02) participated in the study. Contact pressures between the abdomen and thigh were measured using a Tekscan Conformat pressure-mapping sensor during forward-reaching tasks. Kinematic and force plate data were obtained using an infrared motion capture system. The mean abdomen-thigh contact force was 10.17 ± 5.18% of body weight, ranging from 57.8 N to 200 N. Net extensor moment at the hip decreased by mean 16.5 ± 6.44% after accounting for the moment generated by abdomen-thigh tissue contact. In obese individuals, abdomen-thigh contact decreases the net moment at the hip joint during seated forward-reaching activities. This phenomenon should be taken into consideration for accurate biomechanical modeling in these individuals.

Kinematics and kinetics during gait in symptomatic and asymptomatic limbs of children with myelomeningocele.

BACKGROUND: Knee pain and early arthrosis have emerged as significant problems in young adults with myelomeningocele (MMC). The purpose of our study was to examine kinematics and kinetics during gait in symptomatic and asymptomatic limbs of children with an MMC to better understand the factors that may predispose individuals with an MMC to potentially debilitating knee problems. METHODS: Seven children with L3-L4 level MMC and 8 age-matched typically-developing control children participated in this study. Three-dimensional kinematic and kinetic data were obtained bilaterally during gait. A custom-designed femoral tracking device, with established reliability and validity was used to track the thigh. The limbs in an MMC group were subdivided into 2 subgroups (n=6 and 8, symptomatic and asymptomatic, respectively) based on history of pain at the knee joint after walking/weight bearing activity in the last 6 months. An 1-way analysis of variance with post hoc Bonferroni adjustments was used to compare lower extremity kinematic and kinetic variables between symptomatic, asymptomatic, and control limbs. The Pearson product moment correlation (r) was used to assess the relationship between variables of interest. RESULTS: Symptomatic limbs showed increased knee flexion in stance (P=0.01) compared with asymptomatic limbs. Symptomatic limbs showed trends toward increased knee extension, adduction, and internal rotation moments (P=0.031, P=0.025, and P=0.024, respectively) compared with asymptomatic limbs. Hip internal rotation was positively associated with knee internal rotation moment (r=0.93, P=0.008 and r=0.76, P=0.08 in symptomatic and asymptomatic limbs, respectively) and increased knee adduction moment (r=0.84, P=0.03 and r=0.91, P=0.01 in symptomatic and asymptomatic limbs, respectively). CONCLUSIONS: Symptomatic limbs in children with an MMC showed increased knee flexion and trends toward higher extension, adduction, and internal rotation moments. Increased knee flexion accompanied by inadequate control of hip transverse kinematics may have significant implications for knee joint loading in this population. LEVEL OF EVIDENCE: Level 4 (Case series with controls, motion laboratory gait analysis).

Efficacy of gait training with real-time biofeedback in correcting knee hyperextension patterns in young women.

STUDY DESIGN: Single cohort study. OBJECTIVES: To investigate the efficacy of real-time biofeedback provided during treadmill gait training to correct knee hyperextension in asymptomatic females while walking. BACKGROUND: Knee hyperextension is associated with increased stress to the posterior capsule of the knee joint, anterior cruciate ligament, and the anterior compartment of the tibiofemoral joint. Previous methods aimed at correcting knee hyperextension have shown limited success. METHODS: Ten women, ages 18 to 39 years, with asymptomatic knee hyperextension during ambulation, were provided with 6 sessions of real-time feedback of kinematic data (Visual 3D) during treadmill training. Gait evaluations were performed pretraining, posttraining, and 1 month after the last training session. RESULTS: Participants showed improved control of knee hyperextension during overground walking at 1.3 m/s at posttraining and at 1 month posttraining. CONCLUSION: The present study demonstrated that knee sagittal plane kinematics may be influenced by gait retraining using real-time biofeedback.

A new device for assessing ankle dorsiflexion motion: reliability and validity.

STUDY DESIGN: Clinical measurement. OBJECTIVE: To determine the validity and reliability of measures obtained using a custom-made device for assessing ankle dorsiflexion motion and stiffness. BACKGROUND: Limited dorsiflexion has been implicated in the evolution of foot pain in a number of clinical populations. Assessment of ankle dorsiflexion range of motion (ROM) is, therefore, commonly performed as part of a foot and ankle examination. Conventional goniometric assessment methods have demonstrated limited intertester reliability, while alternative methods of measurements are generally more difficult to use. The Iowa ankle range of motion (IAROM) device was designed in an attempt to develop a simple, clinically relevant, and time- and cost-effective tool to measure ankle dorsiflexion range of motion and stiffness. METHODS: Validity and intertester reliability of dorsiflexion range-of-motion measures using the IAROM device were assessed at 10, 15, 20, and 25 Nm of passively applied dorsiflexion torque, with both the knee extended and flexed approximately 20°. Stiffness (change in torque/change in dorsiflexion angle) values were determined using the angular change obtained between the 15- and 25-Nm torque levels. Convergent validity (n = 12) was assessed through comparison of ankle dorsiflexion angles measured simultaneously with the IAROM device and an optoelectronic motion analysis system. Intertester reliability (n = 17) was assessed by 2 testers who took measurements within the same day. RESULTS: Validity testing demonstrated excellent agreement (intraclass correlation coefficient [ICC] values ranging from 0.95 to 0.98). Reliability testing demonstrated good to excellent intertester agreement (ICC values ranging from 0.90 to 0.95). The ICCs for ankle joint dorsiflexion stiffness were .71 and .85 for the knee in an extended and flexed position, respectively. CONCLUSION: The IAROM device provides valid and reliable measurement of ankle dorsiflexion ROM. The IAROM device also allows calculation of stiffness by measuring ROM at multiple torque levels, although the reliability of the measurement is not optimal.

The effect of arch height on kinematic coupling during walking.

The purpose of the current study was to assess kinematic coupling within the foot in individuals across a range of arch heights. Seventeen subjects participated in this study. Weight-bearing lateral radiographs were used to measure the arch height, defined as angle between the 1st metatarsal and the calcaneus. A kinematic model including the 1st metatarsal, lateral forefoot, calcaneus and tibia was used to assess foot kinematics during walking. Four coupling ratios were calculated: calcaneus frontal to forefoot transverse plane motion (Calcaneal EV/Forefoot AB), calcaneus frontal to transverse plane motion (Calcaneus EV/AB), forefoot sagittal to transverse plane motion (Forefoot DF/AB), and 1st metatarsal sagittal to transverse plane motion (1st Metatarsal DF/AB). Pearson product moment correlations were used to assess the relationship between arch height and coupling ratios. Mean (SD) radiographic arch angles of 129.8 (12.1) degrees with a range from 114 to 153 were noted, underscoring the range of arch heights in this cohort. Arch height explained approximately 3%, 38%, 12% and 1% of the variance in Calcaneal EV/Forefoot AB, Calcaneus EV/AB, Forefoot DF/AB and 1st Metatarsal DF/AB respectively. Calcaneal EV/Forefoot AB, Calcaneus EV/AB, Forefoot DF/AB and 1st Metatarsal DF/AB coupling ratios of 1.84 ± 0.80, 0.56 ± 0.35, 0.96 ± 0.27 and 0.43 ± 0.21 were noted, consistent with the twisted foot plate model, windlass mechanism and midtarsal locking mechanisms. Arch height had a small and modest relationship with kinematic coupling ratios during walking.

Relationships between segmental foot mobility and plantar loading in individuals with and without diabetes and neuropathy.

The purpose of our study was to examine dynamic foot function during gait as it relates to plantar loading in individuals with DM (diabetes mellitus and neuropathy) compared to matched control subjects. Foot mobility during gait was examined using a multi-segment kinematic model, and plantar loading was measured using a pedobarograph in subjects with DM (N = 15), control subjects (N = 15). Pearson product moment correlation was used to assess the relationship between variables of interest. Statistical significance and equality of correlations were assessed using approximate tests based on Fisher's Z transformation (alpha = 0.05). In individuals with DM, first metatarsal sagittal plane excursion during gait was negatively associated with pressure time integral under the medial forefoot (r = -0.42 and -0.06, DM and Ctrl, P = 0.02). Similarly, lateral forefoot sagittal plane excursion during gait was negatively associated with pressure time integral under the lateral forefoot (r = -0.56 and -0.11, DM and Ctrl, P = 0.02). Frontal plane excursion of the calcaneus was negatively associated with medial (r = -0.57 and 0.12, DM and Ctrl, P < 0.01) and lateral (r = -0.51 and 0.13, DM and Ctrl, P < 0.01) heel and medial forefoot pressure time integral (r = -0.56 and -0.02, DM and Ctrl, P < 0.01). The key findings of our study indicate that reductions in segmental foot mobility were accompanied by increases in local loading in subjects with DM. Reduction in frontal plane calcaneal mobility during walking serves as an important functional marker of loss of foot flexibility in subjects with DM.

Association of dynamic joint power with functional limitations in older adults with symptomatic knee osteoarthritis.

OBJECTIVES: To determine which lower-limb joint moments and powers characterize the level of gait performance of older adults with symptomatic knee osteoarthritis (OA). DESIGN: Cross-sectional observational study. SETTING: University motion analysis laboratory. PARTICIPANTS: Community-dwelling adults (N=60; 27 men, 33 women; age 50-79y) with symptomatic knee OA. INTERVENTIONS: Not applicable. MAIN OUTCOME MEASURES: Physical function was measured using the long-distance corridor walk, the Short Physical Performance Battery, and the Late Life Function and Disability Instrument (LLFDI Function). Joint moments and power were estimated using an inverse dynamics solution after 3-dimensional computerized motion analysis. RESULTS: Subjects aged 64.2+/-7.4 years were recruited. Ranges (mean +/- SD) for the 400-m walk time and the LLFDI Advanced Lower-Limb Function score were 215.3 to 536.8 (304.1+/-62.3) seconds and 31.5 to 100 (57.0+/-14.9) points, respectively. In women, hip abductor moment (loading response), hip abductor power (midstance), eccentric hamstring moment (terminal stance), and power (terminal swing) accounted for 41%, 31%, 14%, and 48% of the variance in the 400-m walk time, respectively (model R(2)=.61, P<.003). In men, plantar flexor and hip flexor power (preswing) accounted for 19% and 24% of the variance in the 400-m walk time, respectively (model R(2)=.32, P=.025). CONCLUSIONS: There is evidence that men and women with higher mobility function tend to rely more on an ankle strategy rather than a hip strategy for gait. In higher functioning men, higher knee extensor and flexor strength may contribute to an ankle strategy, whereas hip abductor weakness may bias women with lower mobility function to minimize loading across the knee via use of a hip strategy. These parameters may serve as foci for rehabilitation interventions aimed at reducing mobility limitations.

Weight, rather than obesity distribution, explains peak external knee adduction moment during level gait.

OBJECTIVE: To determine whether a lower-body obesity pattern increases estimated forces on the medial compartment of the knee joint. DESIGN: Cross-sectional clinical biomechanical study. RESULTS: Nineteen normal weight (body mass index, 22.8 +/- 1.8 kg/m2), 20 centrally obese (body mass index, 35.0 +/- 4.0 kg/m2 and waist-hip ratio >or=0.85 for women; >or=0.95 for men), and 20 lower-body obese (body mass index, 36.4 +/- 5.4 kg/m2) adults aged 37-55 yrs and without knee pain were recruited. There were no intergroup differences for age. Weight did not differ between obese groups, but thigh girth differed between groups (P < 0.0001). In univariate analysis, both obesity group and thigh girth were significantly related to peak external knee adduction moment in mid-stance phase. However, in multivariate analysis after adjusting for weight, no statistically significant differences persisted using either obesity distribution or thigh girth as predictors. Weight was a significant predictor of external knee adduction moment, explaining 33% (P < 0.0001) of variance in external knee adduction moment for level gait. CONCLUSIONS: These data do not support a significant difference in knee medial compartment loading based on obesity distribution, but do support greater torque with higher weight. This suggests that the mechanism of obesity increasing risk for knee osteoarthritis may not be related to obesity distribution.