Kinetic alterations independent of walking speed in elderly fallers

Surface, but Not Age, Impacts Lower Limb Joint Work during Walking and Stair Ascent

Older adults often suffer an accidental fall when navigating challenging surfaces during common locomotor tasks, such as walking and ascending stairs. This study examined the effect of slick and uneven surfaces on lower limb joint work in older and younger adults while walking and ascending stairs. Fifteen young (18-25 years) and 12 older (>65 years) adults had stance phase positive limb and joint work quantified during walking and stair ascent tasks on a normal, slick, and uneven surface, which was then submitted to a two-way mixed model ANOVA for analysis. The stair ascent required greater limb, and hip, knee, and ankle work than walking (all p < 0.001), with participants producing greater hip and knee work during both the walk and stair ascent (both p < 0.001). Surface, but not age, impacted positive limb work. Participants increased limb (p < 0.001), hip (p = 0.010), and knee (p < 0.001) positive work when walking over the challenging surfaces, and increased hip (p = 0.015), knee (p < 0.001), and ankle (p = 0.010) work when ascending stairs with challenging surfaces. Traversing a challenging surface during both walking and stair ascent tasks required greater work production from the large proximal hip and knee musculature, which may increase the likelihood of an accidental fall in older adults.

Sensorimotor function and standing balance in older adults with transtibial limb loss

BACKGROUND

Limited research has focused on older prosthesis users despite the expected compounded effects of age and amputation on sensorimotor function, balance, and falls. This study compared sensorimotor factors and standing balance between older individuals with and without transtibial amputation, hypothesizing that prosthesis users would demonstrate worse sensorimotor function. Secondarily we assessed the relationship between standing balance and somatosensation in prosthesis users.

METHODS

Thirteen persons with unilateral transtibial amputation (71.7 years) and 10 able-bodied controls (71.7 years) participated in this cross-sectional observational study. Passive joint range-of-motion, muscle strength, proprioception (joint position sense), tactile sensitivity, and standing balance (center-of-pressure sway) were compared between groups. A multiple linear regression analysis assessed the relationship between proprioception and balance (without vision) in prosthesis users.

FINDINGS

Our hypotheses were generally not supported, with the only differences being reduced joint range-of-motion and strength in prosthesis users (with large effect sizes), but comparable sensation and balance. Notably, prosthesis users demonstrated better proprioception than controls as reflected through better joint position sense when the limb was non-weight bearing. Worse amputated limb proprioception was associated with better standing balance in prosthesis users.

INTERPRETATION

Older prosthesis users have impaired passive joint motion and muscle strength compared to controls that could challenge their ability to position and control the amputated limb to avoid falls during daily activities. However, their better amputated limb proprioception might help counteract those limitations by leveraging sensory feedback from the suspended limb. The relationship between amputated limb proprioception and standing balance suggests a nuanced relationship that warrants further study.

Identification of characteristics of foot position and angle during swing phase in fallers using principal component analysis

Identifying the characteristics of fallers is important for preventing falls because such events may reduce quality of life. It has been reported that several variables related to foot positions and angles during gait (e.g., sagittal foot angle and minimum toe clearance) differ between fallers and non-fallers. However, examining such representative discrete variables may not be sufficient to detect crucial information, which may be contained in the large portions of unanalyzed data. Therefore, we aimed to identify the comprehensive characteristics of foot position and angle during the swing phase of gait in non-fallers and fallers using principal component analysis (PCA). Thirty non-fallers and 30 fallers were recruited for this study. We performed PCA to reduce the dimensions of foot positions and angles during the swing phase and obtained principal component scores (PCSs) for each principal component vector (PCV), which were then compared between groups. The results revealed that the PCS of PCV3 in fallers was significantly larger than that in non-fallers (p = 0.003, Cohen's d = 0.80). We reconstructed waveforms of foot positions and angles during the swing phase using PCV3 and our main findings can be summarized as follows. Compared to non-fallers, fallers have a 1) low average foot position in the z-axis (i.e., height) during the initial swing phase 2) small average foot angle in the x-axis (i.e., rotation in the sagittal plane), during the initial swing phase, and 3) large variability in foot position in the y-axis (i.e., anterior/posterior position) during the initial swing phase. We can conclude that these are characteristics of gait related to fallers. Therefore, our findings may be beneficial for evaluating fall risk during gait using a device such as a shoe- or insole-embedded inertial measurement unit.

Ankle plantar flexor muscle performance and patient reported outcomes in people following total ankle arthroplasty

BACKGROUND

The purpose of this study was to prospectively evaluate ankle power generation during gait in people with total ankle arthroplasty, and examine the relationships between postoperative plantar flexor strength, ankle power, and patient outcomes.

METHODS

Nineteen people with end-stage ankle arthritis who received a total ankle arthroplasty and 19 healthy matched controls participated in this case-control study. Patient reported outcomes included a region specific measure of foot function and a generic measure of physical function. Gait speed was recorded with the 6-min walk test. Isokinetic plantar flexor strength was measured with an instrumented dynamometer. Motion capture and force plate data were used to calculate peak ankle power generation during walking. Paired or independent t-tests were used to compare ankle power across time and between groups, respectively. Bivariate correlations were performed to examine the interplay of postoperative strength, ankle power, gait speed, and patient reported outcomes.

FINDINGS

Ankle power was not different between the preoperative and 6-month postoperative time points (d = 0.20). Six-month postoperative ankle power was less than controls (d = 1.32). Strength, ankle power, and gait speed were directly correlated in the patient group 6-months postoperatively (r or ρ ≥ 0.47). Six-month postoperative strength and ankle power were directly correlated to select 2-year patient reported outcomes (both ρ = 0.54).

INTERPRETATION

Lower than normal 6-month postoperative ankle power, which was correlated to strength, gait speed, and longer-term patient reported outcomes, suggests efforts toward improving ankle plantar flexor muscle performance may improve patient outcomes.

Faster or longer steps: Maintaining fast walking in older adults at risk for mobility disability

BACKGROUND

The ability to walk at various speeds is essential to independence for older adults. Maintaining fast walking requires changes in spatial-temporal measures, increasing step length and/or decreasing step time. It is unknown how mobility affects the parameters that change between preferred and fast walking.

RESEARCH QUESTION

How does preferred walking performance and measures of strength and mobility relate to the approach (decreasing step time or increasing step length) older adults at risk for mobility disability use to maintain fast walking speeds?.

METHODS

Peak isokinetic dynamometry of knee and ankle and several mobility evaluations, including the Timed Up-and-Go, Short Physical Performance Battery, and Dynamic Gait Index, assessed mobility and strength in 57 participants, aged 65-80. Biomechanical gait analysis was used to analyze step length, step time, gait speed at preferred and fast gait speeds and ground reaction force during preferred walking. A score combining the differences between step length and time at fast and preferred speeds (Length-Time Difference) separated participants into two groups: (1) Length, representing a predominant increase in step length to walk fast and (2) Time, a predominant decrease in step time.

RESULTS

Those who decreased step time to produce increased speed performed worse during repeated chair stands (p = .006) with no difference in isokinetic strength (p ≥ .15). During preferred walking, the Time group displayed increased propulsive impulse compared to the Length group (p = .007), despite no differences in preferred speed, step length, or time (p ≥ .50).

SIGNIFICANCE

While kinetics of preferred walking differed between groups separated by Length-Time Difference, basic spatial-temporals of preferred walking did not in this homogenous population. Length-Time Difference relates to a common mobility assessment and could be easily calculated by clinicians to provide a quantitative and more sensitive measure of ambulatory performance.

The role of attentional focus on walking efficiency among older fallers and non-fallers

Background

This study evaluated the effect of attentional focus instructions on movement efficiency during a level-ground walking task in older adults with and without a history of falls.

Methods

One hundred and thirty-four community-dwelling older adults were categorised into older fallers (OF) (n = 37) and older non-fallers (ONF) (n = 97). Each participant was instructed to walk at a self-selected pace along a 6 m walkway under three attentional focus conditions (i.e. internal, goal-directed and control) for a total of nine trials. Average muscle activity indices of lower limb co-contractions were measured using surface electromyography.

Results

Both shank and thigh muscle co-contractions were higher in OF than in ONF in all three conditions. OF also demonstrated higher shank muscle co-contraction under the internal relative to the goal-directed condition, with no such change observed in ONF.

Conclusion

Despite no significant between-group differences in functional balance and balance confidence, relative walking inefficiencies were observed in OF compared with ONF. This finding demonstrates the debilitating consequences of falling that can occur with relative independence from various physiological or psychological factors that are commonly associated with falling and used to rationalise behavioural change. We also provide evidence that OF are more susceptible to conditions that provoke them to allocate attention internally. Therefore, in clinical contexts (e.g. gait rehabilitation), verbal instructions that refer to body movements (internal focus) might serve to compromise movement efficiency in older adults with a history of falls. Such changes will, theoretically, lessen the ability to react efficiently to changing environments experienced in daily life.

Effect of walking speed on the intersegmental coordination of lower-limb segments in elderly adults

BACKGROUND

Ageing brings profound changes in walking gait. For example, older adults reduce the modification of pelvic and trunk kinematics with walking speed. However, the modification of the coordination between lower-limb segments with age has never been investigated across various controlled speeds.

RESEARCH QUESTION

Is the effect of speed on the intersegmental coordination different between elderly and young adults?

METHODS

Nineteen senior and eight young adults walked on a treadmill at speeds ranging from 0.56 to 1.94 m s^-1. The motion of the lower-limb segments in the sagittal plane was recorded by cinematography. When the angles of the thigh, shank and foot during a stride are plotted one versus the other, they describe loops constraint on a plane. The coordination between lower-limb segments was thus evaluated by performing a principal component analysis between the thigh, shank and foot elevation angles. The effect of speed and age on the intersegmental coordination was examined using a two-level linear mixed model ANOVA.

RESULTS

In both age groups the orientation of the plane changes with speed, due to a more in-phase shank and foot motion. However, the effect of speed on the covariation plane is lessened with age.

SIGNIFICANCE

Our results demonstrate that there is an age-related specific adjustment of the intersegmental coordination to speed. In particular, older adults restrict their repertoire of angular segment motion. These differences in coordination are mainly related to different foot-shank coordination.

Gait kinematics and kinetics are affected more by peripheral arterial disease than by age

Peripheral arterial disease (PAD) produces abnormal gait and disproportionately affects older individuals. The current study investigated PAD gait biomechanics in younger (<65 yr) and older (>/=65 yr) subjects. The study included 61 patients with PAD (31 younger, age: 57.4 +/- 5.3 yr, and 30 older, age: 71.9 +/- 5.2 yr) and 52 nondisabled age-matched control subjects. Patients with PAD were tested during pain-free walking and compared with control subjects. Joint kinematics and kinetics (torques) were compared using a 2 x 2 analysis of variance (groups: patients with PAD vs control subjects, age: younger vs older). Patients with PAD had significantly increased ankle and decreased hip range of motion during the stance phase as well as decreased ankle dorsiflexor torque compared with control subjects. Gait changes in older individuals are largely constrained to time-distance parameters. Joint kinematics and kinetics are significantly altered in patients with PAD during pain-free walking. Symptomatic PAD produces a consistent ambulatory deficit across ages definable by advanced biomechanical analysis. The most important finding of the current study is that gait, in the absence of PAD and other ambulatory comorbidities, does not decline significantly with age based on advanced biomechanical analysis. Therefore, previous studies must be examined in the context of patients with potential PAD being present in the population, and future ambulatory studies must include PAD as a confounding factor when assessing the gait function of elderly individuals.

Elastic energy in locomotion: Spring-mass vs. poly-articulated models

The human is often modeled as a Poly-Articulated Model (PAM) with rigid segments while some authors use a Spring Mass Model (SMM) for modeling locomotion. These two models are considered independent, and the objective of this study was to link them in order to enlighten the origin of the elasticity in locomotion. Using the characteristics of the two models, a theoretical relationship demonstrates that the variation of elastic energy of the SMM equals the variation of the internal kinetic energy minus internal forces work of the PAM. This theoretical relationship was experimentally investigated among 19 healthy participants walking and running on a treadmill. The results showed that the equality is verified except during the double support phase at 0.56ms(-1), at high walking speeds (1.67 and 2.22ms(-1)) or during the aerial phase of running. The formal relationship showed that the global stiffness of the SMM is directly related to the work of the internal forces of the PAM, and thus, to the characteristics of the musculoskeletal system. It also showed the relevance of taking into account the participation of each joint in the global stiffness. Finally, the coordination of internal forces work to produce a global stiffness may be considered as a new criterion of movement optimization for clinical purposes or motion planning for humanoid robots.

Depth-dependent variations in Achilles tendon deformations with age are associated with reduced plantarflexor performance during walking

The anatomical arrangement of the Achilles tendon (AT), with distinct fascicle bundles arising from the gastrocnemius and soleus muscles, may facilitate relatively independent behavior of the triceps surae muscles. A reduced capacity for sliding between adjacent tendon fascicles with age may couple gastrocnemius and soleus muscle behavior, thereby potentially contributing to diminished plantarflexor performance commonly observed in old adults. Nine healthy young (mean age, 23.9 yr) and eight healthy old (69.9 yr) adults walked at three speeds (0.75, 1.00, and 1.25 m/s) on a force-sensing treadmill. We coupled dynamic ultrasound imaging of the free AT with motion capture and inverse dynamic analyses to compute, in part: 1) depth-dependent variations in AT tissue displacements and elongations and 2) net ankle joint kinetics during push-off. The difference in displacements between superficial and deep AT regions, and in their corresponding elongations, did not differ between old and young adults at the slower two walking speeds (P > 0.61). However, old adults walked with 41% smaller depth-dependent variations in free AT displacements and elongations at 1.25 m/s (P = 0.02). These more uniform tendon deformations in old adults most strongly correlated with reduced peak ankle moment (R(2) = 0.40), but also significantly correlated with reduced peak power generation (R(2) = 0.15) and positive ankle work during push-off (R(2) = 0.19) (P > 0.01). Our findings: 1) demonstrate a potential role for nonuniform AT deformations in governing gastrocnemius and soleus muscle-tendon function and 2) allude to altered tendon behavior that may contribute to the age-related reduction in plantarflexor performance during walking.

Reference values of maximum walking speed among independent community-dwelling Danish adults aged 60 to 79 years: a cross-sectional study

OBJECTIVES

To establish reference values for maximum walking speed over 10 m for independent community-dwelling Danish adults, aged 60 to 79 years, and to evaluate the effects of gender and age.

DESIGN

Cross-sectional study.

SETTING

Danish companies and senior citizens clubs.

PARTICIPANTS

Two hundred and fifty-two adults (167 women, 85 men) with a mean age of 70 [standard deviation (SD) 4] years.

INTERVENTIONS

Not applicable.

MAIN OUTCOME MEASURE

Results for the 10-m walk test (10 MWT) were used to establish reference values.

RESULTS

The mean reference value for maximum walking speed over 10 m for all participants was 1.94 (SD 0.31) m/second. Reference values for women aged 60 to 69 years and 70 to 79 years were 1.96 (SD 0.26) and 1.81 (SD 0.29) m/second, respectively. Reference values for men aged 60 to 69 years and 70 to 79 years were 2.10 (SD 0.35) and 2.01 (SD 0.30) m/second, respectively. Significant differences (P<0.01) were observed in the age and gender categories. Men were found to walk faster than women, and individuals aged 60 to 69 years walked faster than individuals aged 70 to 79 years.

CONCLUSIONS

This study established the reference values for maximum walking speed over 10 m among independent community-dwelling Danish adults aged 60 to 79 years. The study results showed significant differences in maximum walking speed for different ages and between men and women.

Effect of age and activity level on lower extremity gait dynamics: an introductory study

Elderly adults should perform exercises that maintain or improve balance to reduce risk of injury from falls. Bone fractures secondary to falls in the elderly, particularly sedentary females, continue to pose a major health and economic problem. A greater understanding of the processes that contribute to the propensity for falling may be obtained by considering changes in gait biodynamics with age and activity level. Therefore, the purpose of this study was to quantify the relationships between age/activity level and selected biodynamic parameters of the lower extremity during normal gait. Seventeen healthy women, 9 young and 8 elderly, were divided into groups of 9 active and 8 sedentary subjects. Three-dimensional (3D) video motion and force platform kinematic and kinetic data were collected from the hip, knee, and ankle of the right lower extremity as the subjects walked at self-selected speeds. Data were analyzed as functions of age and activity level by using a 2-way analysis of variance. As expected, our results show that the elderly group had significantly greater (p < 0.05) functional and mobility limitations in their lower extremity joints than did the younger group. Significant, age-related lower-limb gait alterations were manifested primarily at the ankle, whereas activity-related alterations were manifested most prominently at the hip. The knee showed the fewest changes accompanying age or activity level. Thus, age and activity level affect gait, which may have a role in the subsequent development of a predisposition to gait-related imbalances and resultant falling and increased hip fracture risk. Strength and conditioning professionals may consider these factors related to age and activity level when individualizing exercise regimens for their older, or sedentary, clients. Prophylactic physical activities involving specific, controlled 3D body movements may help prevent abnormal lower-limb joint kinematics (and their hypothetically coupled, intrinsic postural control strategies), thereby reducing fall and fracture propensity.

Does age affect the response of pelvis and spine to simulated leg length discrepancies? A rasterstereographic pilot study

PURPOSE

The purpose of this study was to investigate age differences in the response of the spine and pelvis to simulated leg length inequalities (LLIs).

METHODS

A total of 107 subjects, separated into three age groups (group 1: 20-39 years, group 2: 40-59 years, group 3: >60 years), were used to evaluate for any age effects in the response to LLIs. LLIs of +10, +20, and +30 mm were simulated with a simulation platform on both sides, and the respective changes of pelvic position (pelvic obliquity, pelvic torsion) and spinal posture (lateral deviation, surface rotation, kyphotic, and lordotic angles) were measured with a rasterstereographic system.

RESULTS

In all three age groups an increase in LLI led to significant changes in the pelvic position as measured by the parameters of pelvic obliquity and torsion. No significant differences in the response of the pelvis to the LLIs were found between the age groups. In all age groups an increase in surface rotation and lateral deviation of the spine with increasing LLIs was found. However, none of these parameters responded significantly different between the three age groups.

CONCLUSIONS

Under static conditions, LLIs lead to significant changes of the pelvic position and spinal posture. Despite all known age-related changes, no significant differences of the measured pelvic and spinal parameters in elderly patients as a response to the simulated LLIs occurred.

Association between energy cost of walking, muscle activation, and biomechanical parameters in older female fallers and non-fallers

OBJECTIVE

To determine the nervous activation, muscle strength, and biomechanical parameters that influence the cost of walking in older fallers and non-fallers.

METHODS

Maximal voluntary isokinetic torque was measured for the hip, knee and ankle of older women. Oxygen consumption was measured at rest and during 8min of walking at self-selected speed. An additional minute of walking was performed to collect kinematic variables and the electromyographic signal of trunk, hip, knee, and ankle muscles, which was analyzed by the linear envelope. Cost of walking was calculated by subtracting resting body mass-normalized oxygen consumption from walking body mass-normalized oxygen consumption. Stride time and length, and ankle and hip range of motion were calculated from kinematic data.

FINDINGS

Older adult fallers had 28% lower knee extensor strength (p=0.02), 47% lower internal oblique activation at heel contact (p=0.03), and higher coactivation between tibialis anterior and gastrocnemius lateralis in each of the gait phases (p<0.05). For fallers, a higher activation of gluteus maximus was associated with a higher cost of walking (r=0.55, p<0.05 and r=0.71, p<0.01, before and after heel contact, respectively). For non-fallers, an association between cost of walking and age (r=0.60, p=0.01) and cost of walking and thigh muscle coactivation (r=0.53, p=0.01) existed.

INTERPRETATION

This study demonstrated that there may be links between lower-extremity muscle weakness, muscle activation patterns, altered gait, and increased cost of walking in older fallers.

Gait mechanics are different between healthy controls and patients with multiple sclerosis

Multiple sclerosis (MS) causes severe gait problems in relatively young individuals, yet there have been limited studies to quantitatively identify the specific gait parameters that are affected. The purpose of this study was to define any differences in biomechanical gait parameters between patients with MS and healthy controls. A total of 31 MS patients and 31 healthy controls were evaluated: joint torques and joint powers were calculated at the ankle, knee, and hip during the stance phase of gait. The self-selected walking velocity was used as a covariate in the analysis to ensure that group differences were not due to differences in walking velocity between the MS and healthy control groups. Reduced angular range, less joint torque, and reduced joint power were seen in patients with MS. We also found significant correlations between biomechanical gait parameters and EDSS score, which provides a clinical rating of disease severity. Our findings provide a quantitative assessment of the gait mechanics employed in patients with MS. The altered lower extremity mechanics observed in patients with MS reflect both a neurological and strength deficit compared with healthy controls during walking.

The role of physical activity in changes in walking mechanics with age

While age-related declines in walking mechanics have been documented, it remains unclear if changes in walking mechanics with age occur as a natural consequence of aging and to what extent these changes are related to a reduction in fitness and physical activity with aging. The study aim was to determine if the walking mechanics of an older (>50) yet highly active population are different from a younger population (<40). Gait mechanics data for 79 middle-aged (50-64 yrs) and 54 older (65-80 yrs) individuals with ≥ 7500 steps/day, based on a 7 day activity monitoring history, and 33 younger adults (ages 18-40) were collected. The older subjects did not reduce self-selected walking speed relative to the younger subjects. However, the walking speed was maintained by increasing cadence while reducing stride-length for middle-aged and older subjects. Middle-aged and older adults had less ankle dorsi-flexion landing at heel-strike and older adults also had less plantar flexion at toe-off. Small decreases in the ankle dorsi-flexion moments (p=0.019, p=0.008) and increases in the hip extension moments (p=0.004, p=0.005) were found for two normalized walking speeds for the middle-aged and older adults compared to the young adults. These results provide quantitative evidence that increased activity with aging can mitigate declines in walking performance and mechanics with age. The high volume of walking activity in the older subjects did not fully prevent changes in gait mechanics, but may have minimized the magnitude of age-related changes on ambulatory function relative to other reports of older inactive subjects.

Persons with multiple sclerosis show altered joint kinetics during walking after participating in elliptical exercise

Patients with multiple sclerosis (MS) experience abnormal gait patterns and reduced physical activity. The purpose of this study was to determine if an elliptical exercise intervention for patients with MS would change joint kinetics during gait toward healthy control values. Gait analysis was performed on patients with MS (n = 24) before and after completion of 15 sessions of supervised exercise. Joint torques and powers were calculated, while also using walking velocity as a covariate, to determine the effects of elliptical exercise on lower extremity joint kinetics during gait. Results show that elliptical exercise significantly altered joint torques at the ankle and hip and joint powers at the ankle during stance. The change in joint power at the ankle indicates that, after training, patients with MS employed a walking strategy that is more similar to that of healthy young adults. These results support the use of elliptical exercise as a gait training tool for patients with MS.

Is there a relationship between fatigue questionnaires and gait mechanics in persons with multiple sclerosis?

OBJECTIVE

To evaluate reported fatigue levels and gait deficits in patients with multiple sclerosis (MS) to determine the relationships that may exist between fatigue in patients with MS and alterations in gait mechanics.

DESIGN

Cross-sectional.

SETTING

Biomechanics laboratory.

PARTICIPANTS

Subjects with MS (n=32) and age- and sex-matched controls (n=30).

INTERVENTIONS

None.

MAIN OUTCOME MEASURES

Fatigue Severity Scale (FSS), Modified Fatigue Index Scale (MFIS), and 36-Item Short Form Health Survey (SF-36) to assess fatigue and general health. Biomechanical gait analysis was performed to measure peak joint torques and powers in the sagittal plane at the ankle, knee, and hip. Correlations were performed between fatigue measures and degree of deficit within each patient with MS for each joint torque and power measure.

RESULTS

FSS score significantly correlated with deficits in ankle power generation at late stance and walking velocity. MFIS score significantly correlated with deficits in peak knee extensor torque and knee power absorption at early stance. SF-36 subscale scores correlated with several joint torque and power variables.

CONCLUSIONS

Subjective fatigue rating scale scores alone should not be used as an indicator of motor disability or disease progression as it affects walking performance of patients with MS.

Are changes in leg power responsible for clinically meaningful improvements in mobility in older adults?

OBJECTIVES

From among physiological attributes commonly targeted in rehabilitation, to identify those in which changes led to clinically meaningful differences (CMDs) in mobility outcomes.

DESIGN

Secondary analysis of data collected for a randomized controlled trial of exercise using binary outcomes defined by recording a large CMD (Short Physical Performance Battery (SPPB)=1 unit; gait speed (GS)=0.1 m/s). Iterative models were performed to evaluate possible confounding between physiological variables and relevant covariates.

SETTING

Outpatient rehabilitation centers.

PARTICIPANTS

Community-dwelling mobility-limited older adults (n=116) participating in a 16-week randomized controlled trial of two modes of exercise.

MEASUREMENTS

Physiological measures included leg power, leg strength, balance as measured according to the Performance-Oriented Mobility Assessment (POMA), and rate pressure product at the maximal stage of an exercise tolerance test. Outcomes included GS and SPPB. Leg power and leg strength were measured using computerized pneumatic strength training equipment and recorded in Watts and Newtons, respectively.

RESULTS

Participants were 68% female, had a mean age of 75.2, a mean of 5.5 chronic conditions, and a baseline mean SPPB score of 8.7. After controlling for age, site, group assignment, and baseline outcome values, leg power was the only attribute in which changes were significantly associated with a large CMD in SPPB (odds ratio (OR)=1.48, 95% confidence interval (CI)=1.09-2.02) and GS (OR=1.31, 95% CI=1.01-1.70).

CONCLUSION

Improvements in leg power, independent of strength, appear to make an important contribution to clinically meaningful improvements in SPPB and GS.

Abnormal joint powers before and after the onset of claudication symptoms

OBJECTIVE

Claudication is the most common manifestation of peripheral arterial disease, producing significant ambulatory compromise. Our study evaluated patients with bilateral lower limb claudication and characterized their gait abnormality based on advanced biomechanical analysis using joint torques and powers.

METHODS

Twenty patients with bilateral claudication (10 with isolated aortoiliac disease and 10 with combined aortoiliac and femoropopliteal disease) and 16 matched controls ambulated on a walkway while 3-dimensional biomechanical data were collected. Patients walked before and after onset of claudication pain. Joint torques and powers at early, mid, and late stance for the hip, knee, and ankle joints were calculated for claudicating patients before and after the onset of claudication pain and were compared to controls.

RESULTS

Claudicating patients exhibited significantly reduced hip and knee power at early stance (weight-acceptance phase) due to decreased torques produced by the hip and knee extensors. In mid stance (single-limb support phase), patients had significantly reduced knee and hip power due to the decreased torques produced by the knee extensors and the hip flexors. In late stance (propulsion phase), reduced propulsion was noted with significant reduction in ankle plantar flexor torques and power. These differences were present before and after the onset of pain, with certain parameters worsening in association with pain.

CONCLUSIONS

The gait of claudication is characterized by failure of specific and identifiable muscle groups needed to perform normal walking (weight acceptance, single-limb support, and propulsion). Parameters of gait are abnormal with the first steps taken, in the absence of pain, and certain of these parameters worsen after the onset of claudication pain.

Kinematic adaptations to ischemic pain in claudicants during continuous walking

Intermittent claudication has been associated with impaired gait and balance. The study aim was to compare gait adaptations over time between claudicants classified with good versus poor balance. Kinematic data were collected from 24 claudicants during continuous walking. Balance was assessed using; Timed Up and Go test (TUG), and Sensory Organisation (SOT) and Motor Control (MCT) Tests using NeuroCom Equitest®. 'Good balance' (GB) was operationally defined as those claudicants achieving normal scores on at least 2 of 3 tests whereas 'poor balance' (PB) claudicants achieved normal scores on 0 or 1 test. Temporal-spatial and sagittal plane joint kinematics were analysed at three time intervals; 'no pain' (prior to onset), 'initial pain' and 'maximal pain' (unable to continue walking). A two-way mixed design ANOVA was performed. Claudicants demonstrated a significant decrease in walking speed, step frequency and increased time in double support (p<0.05). Inter-group analysis showed no differences between GB and PB on any temporal-spatial or kinematic parameters (p>0.05). There was no significant time and group interaction for any temporal-spatial or kinematic variable except hip flexion. GB claudicants demonstrated increased hip flexion as pain progressed but this adaptive strategy was not seen in PB claudicants. Claudicants make adaptations to walking by slowing (down) when in pain. Differences between GB and PB were not seen in temporal-spatial or ankle, knee and pelvic kinematic gait parameters. However adaptation to pain in GB claudicants involved a hip strategy, not seen in PB claudicants.

Independent influence of gait speed and step length on stability and fall risk

With aging, individuals' gaits become slower and their steps shorter; both are thought to improve stability against balance threats. Recent studies have shown that shorter step lengths, which bring the center of mass (COM) closer to the leading foot, improve stability against slip-related falls. However, a slower gait, hence lower COM velocity, does the opposite. Due to the inherent coupling of step length and speed in spontaneous gait, the extent to which the benefit of shorter steps can offset the slower speed is unknown. The purpose of this study was to investigate, through decoupling, the independent effects of gait speed and step length on gait stability and the likelihood of slip-induced falls. Fifty-seven young adults walked at one of three target gait patterns, two of equal speed and two of equal step length; at a later trial, they encountered an unannounced slip. The results supported our hypotheses that faster gait as well as shorter steps each ameliorates fall risk when a slip is encountered. This appeared to be attributable to the maintenance of stability from slip initiation to liftoff of the recovery foot during the slip. Successful decoupling of gait speed from step length reveals for the first time that, although slow gait in itself leads to instability and falls (a one-standard-deviation decrease in gait speed increases the odds of fall by 4-fold), this effect is offset by the related decrease in step length (the same one-standard-deviation decrease in step length lowers fall risk by 6 times).

The effect of pharmacological treatment on gait biomechanics in peripheral arterial disease patients

Background

Pharmacological treatment has been advocated as a first line therapy for Peripheral Arterial Disease (PAD) patients suffering from intermittent claudication. Previous studies document the ability of pharmacological treatment to increase walking distances. However, the effect of pharmacological treatment on gait biomechanics in PAD patients has not been objectively evaluated as is common with other gait abnormalities.

Methods

Sixteen patients were prescribed an FDA approved drug (Pentoxifylline or Cilostazol) for the treatment of symptomatic PAD. Patients underwent baseline gait testing prior to medication use which consisted of acquisition of ground reaction forces and kinematics while walking in a pain free state. After three months of treatment, patients underwent repeat gait testing.

Results

Patients with symptomatic PAD had significant gait abnormalities at baseline during pain free walking as compared to healthy controls. However, pharmacological treatment did not produce any identifiable alterations on the biomechanics of gait of the PAD patients as revealed by the statistical comparisons performed between pre and post-treatment and between post-treatment and the healthy controls.

Conclusions

Pharmacological treatment did not result in statistically significant improvements in the gait biomechanics of patients with symptomatic PAD. Future studies will need to further explore different cohorts of patients that have shown to improve significantly their claudication distances and/or their muscle fiber morphology with the use of pharmacological treatment and determine if this is associated with an improvement in gait biomechanics. Using these methods we may distinguish the patients who benefit from pharmacotherapy and those who do not.

The change of gait parameters during walking at different percentage of preferred walking speed for healthy adults aged 20-60 years

This study aims to investigate the effects of age, gender and walking speed on the gait performance during walking at a range of percentage of preferred walking speed (PPWS). The subjects were aged from 20 to 60 years and both genders were equally represented. A nested-factorial analysis of variance was employed. The independent variables include walking speed (80%, 100%, 120%, and 140% PPWS), age (young, middle, and older groups) and gender. The response measures include lower limb joint motion, vertical ground reaction force (VGRF), muscle electromyography (EMG), heart rate, and perceived exertion of whole body and local areas. The results show that different age and gender groups had similar gait performance on most of the joint motions, HR, as well as the perceived exertions while walking at a range of PPWS. In addition, these performance generally increased with the increasing walking speed and the trend becomes more obvious when the speed was higher than 120% PWS. Age and gender differences have been found in VGRFs and muscle EMG. Females exhibited significantly higher VGRF in the heel-strike and toe-off stages, as well as higher tibialis anterior muscle activity. Older subjects had significantly higher rectus femoris muscle activity than younger adults. Besides, the interaction between gender and walking speed was significant on VGRF in the toe-off stage. Further discussions are addressed.

Gait alterations of diabetic patients while walking on different surfaces

Patients with diabetes have been shown to suffer from increased fall risk. However, authors disagree as to whether only diabetic patients with neuropathy, or also those without neuropathy, present gait alterations. Existing studies evaluate gait indoors, i.e. in specialized gait laboratories. This study evaluates gait parameters in diabetic patients under various real life conditions and compares them to those recorded for healthy controls.

METHODS

We conducted a clinical observation study. Forty-five subjects' gait was assessed on three different surfaces (tar, grass and stones) with a Physilog system (BioAGM, CH), consisting of accelerometers and gyroscopes. Temporal and spatial gait parameters as well as stride-to-stride variability of 30 patients with type 2 diabetes, 15 with and 15 without neuropathy were compared to 15 healthy controls. The three groups were comparable for age, height and body weight (p>0.05).

RESULTS

Diabetic patients' gait parameters differed significantly from those of healthy controls. Post hoc analysis revealed a significant difference between healthy individuals and patients with neuropathy, and between healthy individuals and patients without neuropathy. No difference was observed between patients with and without neuropathy. The highest surface effect was found in patients with diabetic neuropathy, followed by patients without neuropathy and healthy controls.

CONCLUSIONS

Walking in real life conditions revealed gait difficulties in patients with type 2 diabetes before neuropathy was clinically detectable. Clinicians should be aware that diabetic individuals' gait capacity decreases and fall risk increases at an early stage of the disease.

Kinetic mechanisms to alter walking speed

A mechanism to modulate speed during human walking has not yet been proposed in the literature, even though changing walking speed is likely a necessary attribute of everyday ambulation. To understand how joint kinetics modulate walking speed 12 normal adults walked Fast (1.4m/s), Slow (1.0m/s), Accel (1.0-1.4m/s) and Decel (1.4-1.0m/s) trials while full body 3D kinematics and kinetics were collected. Reduced sagittal ankle plantarflexor moments were observed in Accel trials during early single limb stance (p<0.001) and increased sagittal plantarflexor moments were seen in Decel trials during early single limb stance (p<0.001) compared to steady speed walking. Modulating the sagittal ankle moment altered the center of pressure location and either attenuated (Accel) or accentuated (Decel) the early stance braking impulse to accelerate or decelerate the center of mass. The onset of walking speed changes occurred at approximately 15% of the gait cycle and did not support the concept of "controlled falling". Sagittal ankle push-off power appears a consequence of increased walking speed, but not the causative factor to increase walking speed.

Gait characteristics of diabetic patients: a systematic review

Patients with diabetes are at higher risk of experiencing fall-related injuries when walking than healthy controls. The underlying mechanism responsible for this is not yet clear. Thus we intend to summarize diabetic patients' gait characteristics and emphasize those which could be the possible underlying mechanisms for increased fall risk. This systematic review aims, in particular, to: (1) evaluate the quality of existing studies which investigate the gait characteristics of diabetic patients, (2) highlight areas of agreement and contradiction in study results, (3) discuss and emphasize parameters associated with fall risk, and (4) propose new orientations and further domains for research needed for their fall risk prevention. We conducted an electronic search of Pedro, PubMed, Ovid and Cochrane. Two authors independently assessed all abstracts. Quality of the selected articles was scored, and the study results summarized and discussed. We considered 236 abstracts of which 28 entered our full text review. Agreement on data quality between two reviewers was high (kappa: 0.90). Authors investigating gait parameters in a diabetic population evaluated in particular parameters either associated with fall risk (speed, step length or step-time variability) or with ulcers (pressure). There is agreement that diabetic patients walk slower, with greater step variability, and present higher plantar pressure than healthy controls. We concluded that diabetic patients present gait abnormalities, some of which can lead to heightened fall risk. To understand its' underlying mechanisms, and to promote efficient prevention, further studies should analyse gait under 'real-life' conditions.

Detection of gait instability using the center of mass and center of pressure inclination angles

OBJECTIVE

To define a parameter that quantifies balance control during gait and better identifies elderly people who are at a higher risk of falling.

DESIGN

Controlled study.

SETTING

University research laboratory.

PARTICIPANTS

Twelve elderly patients (mean age, 76.9+/-6y) with complaints of imbalance during walking, or with a history of falls, and 12 matched healthy elderly adults.

INTERVENTIONS

Not applicable.

MAIN OUTCOME MEASURES

Temporal-distance gait parameters (gait velocity, stride length, step width); and sagittal and frontal center of mass (COM) and center of pressure (COP) inclination angles.

RESULTS

Elderly patients demonstrated a significantly greater medial, but a significantly smaller anterior, inclination angle than their matched controls during both unobstructed and obstructed gait. The medial COM-COP inclination angle was not affected by the gait velocity in the healthy elderly. When the 2 groups were compared at a similar gait velocity ( approximately 1m/s), the elderly patients still had a significantly greater medial COM-COP inclination angle than did the controls.

CONCLUSIONS

Instantaneous COM-COP inclination angles during walking provide information about the ability to control COM position in relation to the corresponding COP. The medial COM-COP inclination angle may be a sensitive measure of gait stability in the elderly.

Kinematic variability and local dynamic stability of upper body motions when walking at different speeds

A ubiquitous characteristic of elderly and patients with gait disabilities is that they walk slower than healthy controls. Many clinicians assume these patients walk slower to improve their stability, just as healthy people slow down when walking across ice. However, walking slower also leads to greater variability, which is often assumed to imply deteriorated stability. If this were true, then slowing down would be completely antithetical to the goal of maintaining stability. This study sought to resolve this paradox by directly quantifying the sensitivity of the locomotor system to local perturbations that are manifested as natural kinematic variability. Eleven young healthy subjects walked on a motorized treadmill at five different speeds. Three-dimensional movements of a single marker placed over the first thoracic vertebra were recorded during continuous walking. Mean stride-to-stride standard deviations and maximum finite-time Lyapunov exponents were computed for each time series to quantify the variability and local dynamic stability, respectively, of these movements. Quadratic regression analyses of the dependent measures vs. walking speed revealed highly significant U shaped trends for all three mean standard deviations, but highly significant linear trends, with significant or nearly significant quadratic terms, for five of the six finite-time Lyapunov exponents. Subjects exhibited consistently better local dynamic stability at slower speeds for these five measures. These results support the clinically based intuition that people who are at increased risk of falling walk slower to improve their stability, even at the cost of increased variability.

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.

Reliability of Traditional and Fractal Dimension Measures of Quiet Stance Center of Pressure in Young, Healthy People

OBJECTIVES

To assess reliability of traditional and fractal dimension measures of quiet stance center of pressure (COP).

DESIGN

Cross-sectional study.

SETTING

University laboratory.

PARTICIPANTS

Thirty young healthy men (n=20) and women (n=10) (mean age, 23 y).

INTERVENTIONS

Not applicable.

MAIN OUTCOME MEASURES

COP was recorded for 3 trials across 4 conditions: eyes open and eyes closed standing on firm and foam surfaces. Traditional COP variables--peak sway velocity and range of sway, both in the anteroposterior (AP) and mediolateral (ML) directions, and total excursion area, and fractal dimension of the COP in the AP and ML directions--were calculated. Reliability statistics were calculated.

RESULTS

Range of sway (AP) was the most reliable traditional variable (intraclass correlation coefficient model 2,1 [ICC(2,1)] range -.28 to .72.). Peak sway velocity (AP) had poorest reliability (ICC(2,1) range, .05-.29). Only 1 of the traditional variables had excellent reliability; total excursion area (firm, eyes closed) (ICC(2,1)=.95). All bar 1 fractal dimension measures had excellent ICCs. Relative technical error of measurement ranged from 4% to 7% for the fractal dimension measures. Coefficients of variation were also very good, ranging from 1.8% to 6.7%.

CONCLUSIONS

Fractal dimension measures were more reliable than traditional measures of COP. Although traditional measures are used extensively to assess COP, their reliability is questionable. Fractal dimension measures show promise to reliably quantify COP and warrant further investigation.

Outcomes after rehabilitation for adults with balance dysfunction

OBJECTIVES

To assess balance, dynamic gait, and dynamic visual acuity outcomes after a vestibular and balance rehabilitation program and to determine which variables were significantly associated with improved balance and ambulation.

DESIGN

Retrospective case series.

SETTING

Outpatient setting at a tertiary care facility.

PARTICIPANTS

Twenty patients who were seen for vestibular and balance therapy between July 1999 and June 2000.

INTERVENTIONS

A customized exercise program was developed for each patient according to the results of the assessment and included the following interventions, as indicated: gaze stabilization, balance and gait training, and habituation exercises.

MAIN OUTCOME MEASURES

The Dynamic Gait Index (DGI), Berg Balance Scale (BBS), Dynamic Visual Acuity Test (DVAT), and computerized post urography (Sensory Organization Test [SOT]).

RESULTS

The mean change scores for the DGI showed significant improvement for both patients with peripheral vestibular dysfunction and patients with central balance disorders. For the central balance disorders group, the BBS score also showed significant improvement. No difference was noted for pretherapy and posttherapy SOT scores between groups. The total group appeared to show an average improvement of more than 2 lines on the visual acuity chart on the clinical DVAT. Patients who were 66 years or older were 1.5 times more likely to score less than 20 on the DGI, and those whose pretherapy vertical dynamic visual acuity was 20/80 or worse were 1.3 times more likely to score less than 20 on the DGI.

CONCLUSIONS

Patients showed functional improvements in balance, visual acuity, and gait stability after balance and vestibular physical therapy. Age and pretherapy vertical dynamic visual acuity score influenced dynamic gait outcome after a balance rehabilitation program.

Acceleration patterns of the head and pelvis when walking are associated with risk of falling in community-dwelling older people

BACKGROUND

A large proportion of falls in older people occur when walking, however the mechanisms underlying impaired balance during gait are poorly understood. This study evaluated acceleration patterns of the head and pelvis when walking on a level and an unpredictably irregular surface to determine whether older people at risk of falling demonstrate an impaired ability to stabilize the body under challenging conditions.

METHODS

One hundred community-dwelling older people aged between 75 and 93 years were evaluated for their risk of falling using a range of physiological tests previously found to be accurate predictors of falling in prospective studies. Temporo-spatial gait parameters and acceleration patterns at the head and pelvis were then measured in three orthogonal planes while subjects walked on a flat corridor and an unpredictably irregular walkway. Harmonic ratios of head and pelvis accelerations in each plane were calculated to provide an indicator of stability.

RESULTS

Subjects with a high risk of falling exhibited reduced temporo-spatial gait parameters and increased step timing variability. Harmonic ratios of acceleration patterns were reduced at the head and pelvis in the vertical and antero-posterior directions. These differences were particularly evident when walking on the irregular surface.

CONCLUSION

Older people at risk of falling adopt a more conservative basic walking pattern, but this does not ensure that the movements of the head and pelvis are stable. The irregular pelvis and head accelerations evident in the high risk group suggests that these subjects may have difficulty controlling trunk motion and maintaining a stable visual field when walking, particularly on irregular terrain.

Swing phase mechanics of healthy young and elderly men

This study examined the effect of ageing on the swing phase mechanics of young and elderly gait. Sagittal plane marker trajectories and force plate data were collected while 10 young (24.9+/-0.9 years) and eight elderly (68.9+/-0.4 years) subjects walked at their preferred walking speeds. Comparison between young and elderly gait was made for a range of spatial-temporal, kinematic and kinetic variables with emphasis given to identifying possible differences at toe-off, minimum metatarsal-phalangeal joint clearance and heel contact. In order to control for the confounding effect of gait velocity on the dependent variables, a multivariate analysis of covariance was used to identify differences between the young and elderly subjects due to age. In contrast to studies that have reported lower preferred walking speeds in the elderly compared to the young [J.O. Judge, R.B. Davis III, S. Ounpuu, Step length reductions in advanced age: the role of ankle and hip kinetics, Journal of Gerontology: Medical Sciences 51 (1996) M303-312; D.C. Kerrigan, M.K. Todd, U. Della Croce, L.A. Lipsitz, J.J. Collins, Biomechanical gait alterations independent of speed in the healthy elderly: evidence for specific limiting impairments, Archives of Physical and Medical Rehabilitation 79 (1998) 317-322], no differences in walking speed nor in the spatial-temporal variables that determine walking speed were detected. The elderly were however, found to have a greater hip extension moment at the time of minimum metatarsal-phalangeal joint clearance, and a significantly higher anterior-posterior velocity heel contact velocity that was linked to a significantly higher shank and foot angular velocity at heel contact. Since many gait variables are highly correlated with walking speed [C. Kirtley, M.W. Whittle, R.J. Jefferson, Influence of walking speed on gait parameters, Journal of Biomechanical Engineering 7 (1985) 282-288; D.A. Winter, Biomechanical motor patterns in normal walking, Journal of Motor Behaviour 15 (1983) 302-330], differences between young and elderly gait found in the present study may therefore be attributed to ageing, rather than a secondary effect of differences in gait velocity.

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.