Reduced hip extension during walking: healthy elderly and fallers versus young adults

OBJECTIVES: To test the hypothesis that reduced hip extension range during walking, representing a limiting impairment of hip tightness, is a consistent dynamic finding that (1) occurs with increased age and (2) is exaggerated in elderly people who fall. DESIGN: Using a 3-dimensional optoelectronic motion analysis system, we compared full sagittal plane kinematic (lower extremity joint motion, pelvic motion) data during walking between elderly and young adults and between elderly fallers and nonfallers. Comparisons were also performed between comfortable and fast walking speeds within each elderly group. SETTING: A gait laboratory. PARTICIPANTS: Twenty-three healthy elderly subjects, 16 elderly fallers (otherwise healthy elderly subjects with a history of recurrent falls), and 30 healthy young adult subjects. MAIN OUTCOME MEASURES: All major peak joint angle and pelvic position values. RESULTS: Peak hip extension was the only leg joint parameter measured during walking that was both significantly lower in elderly nonfallers and fallers than in young adult subjects and was even lower in elderly fallers compared with nonfallers (all p <.05). Peak hip extension +/- standard deviation during comfortable walking speed averaged 20.4 degrees +/- 4.0 degrees for young adults, 14.3 degrees +/- 4.4 degrees for elderly nonfallers, and 11.1 degrees +/- 4.8 degrees for elderly fallers. Peak hip extension did not significantly improve when elderly subjects walked fast. CONCLUSION: An isolated and consistent reduction in hip extension during walking in the elderly, which is exaggerated in fallers, implies the presence of functionally significant hip tightness, which may limit walking performance. Overcoming hip tightness with specific stretching exercises is worthy of investigation as a simple intervention to improve walking performance and to prevent falls in the elderly.     

The effect of walking speed on lower-extremity joint powers among elderly adults who exhibit low physical performance

OBJECTIVES: To compare peak joint powers and joint angles between comfortable and fast walking speeds among a group of elderly adults who exhibit low physical performance, and to test the primary hypothesis that peak ankle powers would not change when walking speed was increased, but that peak hip power output would increase significantly with speed. DESIGN: Three-dimensional analysis of joint kinematics and kinetics during comfortable and fast walking by both healthy and low-performing elderly adults (age, >70y). SETTING: Gait laboratory. PARTICIPANTS: Twenty-four healthy elderly adults and 27 elders who exhibited low performance on a standard battery of walking, standing balance, and chair-rise tasks that places them at risk of mobility-related disability. INTERVENTIONS: Not applicable. MAIN OUTCOME MEASURES: Peak lower-extremity joint powers and joint angles. RESULTS: Low-performing elders increased both ankle and hip power outputs to increase walking speed. However, peak ankle power remained significantly below that of the healthy elderly adults even when the low-performing elders walked at a faster gait speed. Joint-power changes in the low-performing elderly were accompanied by a reduction in hip extension and ankle dorsiflexion, and an increase in transverse pelvic rotation. CONCLUSIONS: Compared with healthy elderly, the low-performing elderly adults showed speed-independent differences in ankle and hip mechanics that may reflect underlying neuromuscular impairments. In particular, an understanding of the interdependent contributions of hip flexibility and ankle power limitations seem important to inform interventions to maintain gait into advanced age.     

Gait characteristics of elderly people with a history of falls: a dynamic approach

BACKGROUND AND PURPOSE: This study investigated changes in the kinematics of elderly people who experienced at least one fall 6 months prior to data collection. The authors hypothesized that, in order to decrease variability of walking, people with a history of falls would show different kinematic adaptations of their walking patterns compared with elderly people with no history of falls. SUBJECTS AND METHODS: Twenty-one elderly people who had fallen within the previous 6 months ("fallers"; mean age=72.1 years, SD=4.9) and 27 elderly people with no history of falls ("nonfallers"; mean age=73.8 years, SD=6.4) walked at their preferred stride frequency (STF) as treadmill speed was gradually increased (from 0.18 m/s to 1.52 m/s) and then decreased in steps of 0.2 m/s. Gait parameter measurements were recorded, and statistical analysis was applied using walking speed and STF as independent variables. RESULTS: Fifty-seven percent of the fallers were unable to walk at the fastest speed, whereas all nonfallers walked comfortably at all walking speeds. Although the fallers showed significantly greater STF, smaller stride lengths, smaller center-of-mass lateral sway, and smaller ankle plantar flexion and hip extension during push-off, they showed increased variability of kinematic measures in their coordination of walking compared with the nonfallers. DISCUSSION AND CONCLUSION: Although the fallers' adaptations were expected to reduce variability in the coordination of walking, they showed less stable gait patterns (ie, greater variability) compared with the nonfallers. Increased variability of walking patterns may be an important gait risk factor in elderly people with a history of falls.     

Gait analysis of elderly women after total knee arthroplasty

[Purpose] The purpose of this study was to investigate ability and muscle activities of elderly women after total knee arthroplasty (TKA) and compare them with those of healthy ones. [Subjects and Methods] Fifteen female patients with TKA due to advanced degenerative arthritis of the measured on knee joint and 19 healthy elderly females participated. Tibiofemoral angles of TKA patients were using a gait analysis system anterioposterior X-rays of the weight-bearing knee. The knee flexion angle and gait parameters were measured. Muscle activities and prolongation time were EMG system. The gait of the treated limb of each participant was evaluated in three consecutive trials at fast speed and comfortable speed. [Results] The knee flexion angle %stance phase, stride length, step length, speed, cadence, and gait cycle significantly decreased at both the fast speed and comfortable speeds, and the onset and duration time of rectus femoris activity was significantly increased at the comfortable speed in the TKA group. [Conclusion] In conclusion, elderly women who received TKA showed decreased gait ability and muscle activity compared to the healthy elderly women.Key words: Arthroplasty, Gait, Electromyography     

Fall risk assessment in very old males and females living in nursing homes

BACKGROUND: Several studies identified muscle weakness, history of falls, gait deficit and balance deficit as the most common risk factors for falls. AIMS: To determine risk factors of fall in older males and females living in nursing homes and to compare characteristics of fallers and non fallers. METHODS: This is a cross-sectional study with a convenience sample of 40 nursing home elderly (13 males and 27 females), mean age 86.35, of which 17 (6 males and 11 females) fell at least once in the previous year and 23 (7 males and 16 females) had not fallen. Each participant filled a self-assessment questionnaire (general health questions and selected questions from the SF-36). An objective evaluation was performed with measurements of blood pressure and heartrate (supine and standing), lower extremity strength and power (dominate side only) by Biodex isokinetic dynamometry, dynamic postural stability by Biodex balance system (5 s trials at level 8) and gait assessment (6 min walk test at comfortable speed) by gait treadmill Biodex. RESULTS: The fallen males decreased significantly knee flexion peak torque (p=0.08), ankle plantarflexion peak torque and average power (p=0.05), compared with the not fallen group. The fallen females decreased significantly knee extension peak torque and average power (p<0.05), walking speed (p<0.005) and cadence (p<0.01), compared with the not fallen group. CONCLUSIONS: This study shows that the fallen males had greater deficits of ankle plantar-flexion strength and power, while fallen females had greater deficits of knee extension strength and power and less walking speed.     

The influence of patella alta on patellofemoral joint stress during normal and fast walking

Objective: To determine if persons with patella alta exhibit elevated patellofemoral joint stress compared to pain-free controls during normal and fast walking speeds.

Subjects: Twenty-four subjects (13 patella alta, 11 pain-free controls) participated.

Methods: Sagittal and axial magnetic resonance images of the knee were obtained to quantify subject specific knee extensor mechanics and patellofemoral joint contact area. Instrumented gait analysis was used to quantify knee joint kinematics and kinetics. MRI and gait data were used as input variables into a model of patellofemoral joint stress. Analysis of variance with repeated measures was used to compare group differences and group × gait speed interactions for each dependent variable during stance.

Results: During normal speed gait there were no group differences in peak knee flexion angle, knee extensor moment, joint reaction force, or stress. However, the patella alta group had significantly less contact area. During fast speed gait there were no group differences in peak knee flexion angle, knee extensor moment, or joint reaction force. However, the patella alta group demonstrated significantly less contact area and significantly greater stress compared to controls.

Conclusion: Persons with patella alta demonstrated greater calculated patellofemoral stress during fast walking. This was the result of reductions in contact area as joint reaction forces were similar between groups.

Relevance Persons with patella alta may be predisposed to patellofemoral dysfunction through elevations in joint stress. Therefore, treatments aimed at increasing the load-bearing surface area between the patella and femur, such as bracing, may be beneficial in this patient population.     

Changes of kinematic parameters of lower extremities with gait speed: a 3D motion analysis study

[Purpose] The purpose of this study was to investigate the changes in hip, knee and ankle kinematic variables of the lower extremities at different gait speeds. [Subjects and Methods] Forty healthy subjects who had no previous history of neurological, musculo-skeletal or other medical conditions that could affect gait were recruited. The subjects were asked to walk 10 m down a walkway at three different gait speeds: normal gait speed, and self-selected fast, and slow speeds. The experimental order was randomly chosen across these gaits. The hip, knee and ankle kinematic data were evaluated using a VICON 3D motion analysis system and force plates. [Results] The flexion peak and external rotation peak of the knee joint significantly increased with the increase of gait speed. The plantarflexion peaks of the ankle joint significantly increased with increase of gait speed. However, none of the kinematic data of the hip joint were significantly dependent on increase of gait speed. [Conclusion] The relationship of the knee and ankle joint can be described as coupling motion which is dependent on gait speed. Our present findings suggest that coupling motion of the knee joint and plantarflexion of the ankle joint significantly increase with increase of gait speed. These results will provide important insight into gait mechanisms for the evaluation of pathological populations.Key words: Gait speed, 3D motion analysis, Lower extremity     

Gait adaptation in chronic anterior cruciate ligament-deficient patients: Pivot-shift avoidance gait

Background

A variety of biomechanical adaptations of the knee during gait have been reported in ACL-deficient patients to cope with anteroposterior knee instability. However, strategies to prevent rotatory knee instability are less recognized. We hypothesized that ACL-deficient patients would make distinctive gait changes to prevent anterolateral rotatory knee instability. Specifically, we hypothesized that during the terminal stance phase of the gait cycle, ACL-deficient patients would reduce the internal rotation knee joint moment and exhibit a higher knee flexion angle. We call this altered gait a pivot-shift avoidance gait. We also hypothesized that patients would not be able to adapt their knee biomechanics as efficiently at a fast gait speed.

Methods

Twenty-nine patients with chronic ACL deficiency and 15 healthy volunteers took part in a treadmill gait analysis. The terminal stance phase was analyzed under both comfortable and fast gait speed conditions.

Findings

At both gait speeds, ACL-deficient patients significantly reduced the internal rotation knee joint moment and showed larger knee flexion angles during the terminal stance phase of the gait cycle than did the control group. However, the difference in the minimum knee flexion angle between groups under the fast gait speed condition was not statistically significant.

Interpretation

ACL-deficient patients adopted the proposed pivot-shift avoidance gait, possibly to prevent anterolateral rotatory knee instability. The patients were not able to adapt their knee biomechanics as effectively during fast-paced walking. This study reinforces the pertinence of gait analysis in ACL-deficient knees to acquire more information about the function of the knee joint.     

Pelvic and lower limb compensatory actions of subjects in an early stage of hip osteoarthritis

OBJECTIVE: To determine if compensatory actions take place at the pelvis and other joints of the affected lower limb in subjects who were in an early stage of hip osteoarthritis (OA). DESIGN: Nonrandomized, case-control study. SETTING: A gait laboratory. PARTICIPANTS: Seventeen patients with OA of the hip (clinical group) matched with 17 healthy elderly subjects (nonclinical group). INTERVENTIONS: Video data obtained while subjects walked a 10-meter walkway twice and stepped across a forceplate. MAIN OUTCOME MEASURES: Four phasic and temporal gait parameters (walking speed, stance phase relative duration, stride length, cadence) 10 pelvic (pelvic tilt, obliquity, rotation at push-off maximum range of motion for all 3) and hip (3 hip angles at push-off, maximum hip flexion) kinematic parameters, 3 hip moments, and twenty-seven 3-dimensional peak muscle powers (labeled by joint, peak power, plane) developed in the lower limb joints during the gait cycle. RESULTS: Subjects in the clinical group were characterized by a 12.4% slower walking speed. The pelvis was more upwardly tilted (2.5 times) at push-off in the clinical group than in the nonclinical group. Obliquity, measured in the frontal plane, revealed that the pelvis dropped more (2.4 times) on the unsupported limb of the clinical group at push-off. In the sagittal plane, subjects in the clinical group absorbed less energy in their second hip peak power for decelerating the thigh extension and generated less hip pull (third hip peak power) than the nonclinical group by 34% and 29%, respectively. In the sagittal plane, the clinical group had 57% lower second knee peak power to straighten the joint shortly after heel strike, and 43% less knee absorption (third peak power) at push-off. During the push-off phase, the clinical group developed more than twice their third peak knee power in the frontal plane and 5 times more their third peak knee power in the transversal plane than the peak knee power of the nonclinical group in an attempt to control knee adduction and to facilitate body-weight transfer by an internal rotation. At the end of the swing phase, the fourth peak power in the sagittal plane showed the absorption power required to decelerate the leg; it was reduced by 35% in the clinical group, representing a strategy to increase walking speed by lengthening the stride length. CONCLUSIONS: Even at an early stage of hip OA, joint degeneration was compensated by an increase in pelvis motion and muscle power generation or absorption modifications in other lower limb joints.     

A clinical comparison of variable-damping and mechanically passive prosthetic knee devices

OBJECTIVE: Although variable-damping knee prostheses offer some improvements over mechanically passive prostheses to transfemoral amputees, there is insufficient evidence that such prostheses provide advantages at self-selected walking speeds. In this investigation, we address this question by comparing two variable-damping knees, the hydraulic-based Otto Bock C-leg and the magnetorheological-based Ossur Rheo, with the mechanically passive, hydraulic-based Mauch SNS. DESIGN: For each prosthesis, metabolic data were collected on eight unilateral amputees walking at self-selected speeds across an indoor track. Furthermore, kinetic, kinematic, and electromyographic data were collected while walking at self-selected speeds across a 10-m walkway in a laboratory. RESULTS: When using the Rheo, metabolic rate decreases by 5% compared with the Mauch and by 3% compared with the C-leg. Furthermore, for the C-leg and Rheo knee devices, we observe biomechanical advantages over the mechanically passive Mauch. These advantages include an enhanced smoothness of gait, a decrease in hip work production, a lower peak hip flexion moment at terminal stance, and a reduction in peak hip power generation at toe-off. CONCLUSION: The results of this study indicate that variable-damping knee prostheses offer advantages over mechanically passive designs for unilateral transfemoral amputees walking at self-selected ambulatory speeds, and the results further suggest that a magnetorheological-based system may have advantages over hydraulic-based designs.     

Matching walking speed of controls affects identification of gait deviations in patients with a total knee replacement

BackgroundThe assessment of functional recovery of patients after a total knee replacement includes the quantification of gait deviations. Comparisons to comfortable gait of healthy controls may incorrectly suggest biomechanical gait deviations, since the usually lower walking speed of patients already causes biomechanical differences. Moreover, taking peak values as parameter might not be sensitive to actual differences. Therefore, this study investigates the effect of matching walking speed and full-waveform versus discrete analyses.MethodsGait biomechanics of 25 knee replacement patients were compared to 22 controls in two ways: uncorrected and corrected for walking speed employing principal component analyses, to reconstruct control gait biomechanics at walking speeds matched to the patients. Ankle, knee and hip kinematics and kinetics were compared over the full gait cycle using statistical parametric mapping against using peak values.FindingsAll joint kinematics and kinetics gait data were impacted by applying walking speed correction, especially the kinetics of the knee. The lower control walking speeds used for reference generally reduced the magnitude of differences between patient and control gait, however some were enlarged. Full-waveform analysis identified greater deviating gait cycle regions beyond the peaks, but did not make peak value analyses redundant.InterpretationMatching walking speed of controls affects identification of gait deviations in patients with a total knee replacement, reducing deviations confounded by walking speed and revealing hidden gait deviations related to possible compensations. Full-waveform analysis should be used along peak values for a comprehensive quantification of differences in gait biomechanics.     

不同速度下正常老年人下肢关节的角度参数

背景：目前国内主要采用步态分析仪测量患者步行时的关节角度,但是在每一个康复治疗时期进行这些测量非常耗费时间。利用Lokomat步态康复机器人则可以在患者训练过程中对患者的关节角度、肌力等参数进行实时记录,省时省力。目的：采用步态康复机器人Lokomat测定正常老年人不同速度下的下肢关节角度参数。方法：选取健康老年人30名,男15名,女15名,年龄60~64（62.40±1.58）岁。利用步态康复机器人评估工具,在减重40%,引导力60%,速度1.6,1.8,2.0km/h状态下对正常老年人的下肢关节角度参数进行记录。结果与结论：老年人关节角度参数动态指标测试结果显示,在速度1.6km/h状态下左髋关节最大伸展角度,在速度2.0km/h状态下左、右髋关节最大屈曲角度,男女组间差异有显著性意义（P〈0.05）。老年人不同速度下髋膝关节角度测试结果显示,老年人左右膝关节最大伸展角度在步行速度1.6km/h与1.8km/h,1.6km/h与2.0km/h,1.8km/h与2.0km/h相比差异有显著性意义（P〈0.05）。结果可见不同速度下髋关节最大屈曲角度男性大于女性,治疗师在进行Lokomat步态康复训练时应根据患者的性别差异,调整髋膝关节角度和训练模式。随着步行速度的增加老年人髋膝关节屈曲角度增加,伸展角度减小,治疗师应根据步速的增减适当调节髋膝关节活动度,增强患者腿部运动与机器人外骨骼式机械腿的配合,提高患者的训练效果。     

The effect of total knee replacement on dynamic support of the body during walking and stair ascent

BACKGROUND: Little is known about the effects of total knee replacement surgery on the contributions of individual joint moments to the total support moment. A better understanding of these effects may enhance rehabilitation protocols and determine factors related to long-term surgical outcome. METHOD: Twenty-one subjects with total knee replacement and 21 controls performed level walking and stair ascent at two testing periods, pre- and 6 months post-surgery. Variables studied included gait velocity, stride length, knee flexion angle, net joint moments of the hip, knee and ankle, and total support moment. Data were analyzed at the first peak vertical ground reaction force. FINDINGS: For level walking, the total support moment, knee extensor moment, and knee flexion angle of total knee replacement patients were less than controls at post-surgery. For stair ascent, the patient group total support moment, ankle plantarflexor moment, and knee flexion angle were less than controls at both testing periods, while knee extensor moment was less than controls at post-surgery. Extensor synergies of the total knee replacement patients revealed less knee and more hip contributions during level walking and larger hip contributions during stair ascent to the total support moment than controls at both testing periods. INTERPRETATION: A feature of total knee replacement gait, pre- and post-surgery, is a stiff knee attitude which may serve to protect the quadriceps. The larger hip extensor contribution to the total support moment observed in the patients may compensate for the diminished knee extensor contribution during level walking and stair ascent.     

A multiple regression normalization approach to evaluation of gait in total knee arthroplasty patients

BackgroundGait features characteristic of a cohort may be difficult to evaluate due to differences in subjects' demographic factors and walking speed. The aim of this study was to employ a multiple regression normalization method that accounts for subject age, height, body mass, gender, and self-selected walking speed in the evaluation of gait in unilateral total knee arthroplasty patients.MethodsThree-dimensional gait analysis was performed on 45 total knee arthroplasty patients and 31 aged-matched controls walking at their self-selected speed. Gait data peaks including joint angles, ground reaction forces, net joint moments, and net joint powers were normalized using subject body mass, standard dimensionless equations, and a multiple regression approach that modeled subject age, height, body mass, gender, and self-selected walking speed.FindingsNormalizing gait data using subject body mass, dimensionless equations, and multiple regression approach resulted in a significantly lower knee adduction moment and knee extensor power in total knee arthroplasty patients compared to controls (p < 0.05). In contrast to normalization using body mass and dimensionless equations, multiple regression normalization greatly reduced variance in gait data by minimizing correlations with subject demographic factors and walking speed, resulting in significantly higher peak hip extension angles and peak hip flexion powers in total knee arthroplasty patients (p < 0.05).InterpretationTotal knee arthroplasty patients generate greater hip extension angles and hip flexor power and have a lower knee adduction moment than healthy controls. This gait pattern may be a strategy to reduce muscle and joint loading at the knee.     

脑卒中偏瘫患者膝过伸步态运动学特点分析

目的:探讨脑卒中偏瘫患者膝过伸步态的三维运动学特点及其与步行速度的相关性,从运动学角度探讨影响膝过伸患者步行速度的主要因素。方法:利用三维步态分析系统对15例伴有膝过伸步态的脑卒中偏瘫患者和15例健康老年人进行运动学定量比较,并将其与步行速度进行相关性分析。结果:与正常对照组相比,膝过伸患者的步长、步频减小,步速减慢,支撑期百分比延长(均P0.05);膝过伸患者髋、膝、踝关节活动范围减小,最大伸髋、屈膝、踝背屈角度减小,最大伸膝角度增加(均P0.05)。步行速度与步频、支撑相百分比、膝踝关节活动范围、最大屈膝角度和最大踝跖屈角度均相关(均P0.05)。结论:脑卒中偏瘫膝过伸患者下肢关节活动不同程度受限,步行速度下降,其中屈膝和踝跖屈异常是影响膝过伸患者步行速度的主要因素。     

Fall risk assessment in very old males and females living in nursing homes

Background:?Several studies identified muscle weakness, history of falls, gait deficit and balance deficit as the most common risk factors for falls.

Aims:?To determine risk factors of fall in older males and females living in nursing homes and to compare characteristics of fallers and non fallers.

Methods:?This is a cross-sectional study with a convenience sample of 40 nursing home elderly (13 males and 27 females), mean age 86.35, of which 17 (6 males and 11 females) fell at least once in the previous year and 23 (7 males and 16 females) had not fallen. Each participant filled a self-assessment questionnaire (general health questions and selected questions from the SF-36). An objective evaluation was performed with measurements of blood pressure and heartrate (supine and standing), lower extremity strength and power (dominate side only) by Biodex isokinetic dynamometry, dynamic postural stability by Biodex balance system (5?s trials at level 8) and gait assessment (6?min walk test at comfortable speed) by gait treadmill Biodex.

Results:?The fallen males decreased significantly knee flexion peak torque (p?=?0.08), ankle plantarflexion peak torque and average power (p?=?0.05), compared with the not fallen group. The fallen females decreased significantly knee extension peak torque and average power (p?<?0.05), walking speed (p?<?0.005) and cadence (p?<?0.01), compared with the not fallen group.

Conclusions:?This study shows that the fallen males had greater deficits of ankle plantar-flexion strength and power, while fallen females had greater deficits of knee extension strength and power and less walking speed.     

Identification of kinetic differences between fallers and nonfallers in the elderly.

Falls are a major cause of decreased mobility and disability in the elderly. Multiple factors are believed to contribute to falling. Among these, gait abnormalities have drawn attention as a possible risk factor. Although previous studies have revealed few differences in gait parameters compared with similar aged controls, it was hypothesized that because of intrinsic differences in balance and motor control, we would observe differences in joint kinetics. In this study, 15 subjects (mean age, 77 +/- 9 yr), who had at least 2 mo of repeated falls from an unclear cause, were evaluated in a gait laboratory and were compared with a control group of 15 subjects (mean age, 75 +/- 5 yr) with no history of falls. Analysis of data demonstrated a significantly greater peak torque in the falls group for the following: hip flexion, hip adduction, knee extension, knee varum, ankle dorsiflexion, and ankle eversion (P < 0.003 in each comparison). Also, ankle plantarflexion torque was significantly decreased in the falls group (P = 0.001). Joint powers showed different absorption at the knee and ankle in the falls group. The discovery of these kinetic differences may provide further insight into the mechanism of falls in the elderly and, more importantly, lead to identifiable markers to detect those who may be susceptible to falls.     

Effect of a hip flexor-stretching program on gait in the elderly

OBJECTIVES: To test whether a reduction in peak hip extension during the terminal stance phase of walking in elderly compared with young adult subjects represents a hip flexor contracture impairment rather than some dynamic consequence and to test the hypothesis that stretching the hip flexors improves both static and dynamic peak hip extension, as well as other age-related gait changes about the ankle. DESIGN: A double-blinded, randomized, controlled trial. SETTING: Stretching exercises were performed in the subjects' homes. Pre- and postassessments were performed in a gait laboratory. PARTICIPANTS: Ninety-six healthy elderly individuals in 2 groups: treatment (n=47) and control (n=49). INTERVENTION: The treatment group received a 1-time instruction in hip flexor stretching, whereas the control group received a 1-time instruction in shoulder abductor stretching. Participants in each group were asked to perform stretching exercises on their own twice daily for 10 weeks. MAIN OUTCOME MEASURES: Static and dynamic peak hip extension, peak anterior pelvic tilt, and other peak kinematic and kinetic variables during the gait cycle. RESULTS: There was a modest improvement in static peak hip extension as measured by a goniometer within the treatment group (mean +/- standard deviation, 6.1 degrees +/-2.5 degrees to 7.7 degrees +/-3.6 degrees, P=.032) compared with no change in the control group. At comfortable walking speed, dynamic hip extension tended to increase in the treatment group (5.1 degrees +/-9.7 degrees to 7.1 degrees +/-8.0 degrees, P=.103) compared with no real change in the control group (5.3 degrees +/-8.9 degrees to 5.4 degrees +/-7.5 degrees, P=.928). Similarly, at fast walking speed, dynamic hip extension tended to increase in the treatment group (6.4 degrees +/-9.8 degrees to 8.4 degrees +/-8.0 degrees, P=.093) compared with no change in the control group. Changes in ankle kinematics and kinetics included a significant improvement in peak ankle plantarflexion and a tendency to improved ankle power generation. CONCLUSION: The static and dynamic trends to improvement in peak hip extension were of similar magnitude, suggesting that age-related reduction in peak hip extension during gait is the result of a static hip flexion contracture rather than a dynamic consequence. Additionally, age-related changes in ankle kinematics and kinetics may be secondarily related to hip flexion contracture impairment rather than impairment at the ankle per se. This study was limited by the exercises being unsupervised and relying on 1-time instruction. A more rigorous and supervised hip flexor-stretching exercise program may yield more substantial improvements in gait parameters.