Differences in balance control between healthy younger and older adults during steady-state walking

Age related differences in whole body and body part angular momentum in the frontal plane during walking

The contribution of body part angular momentum (BPAM) to whole body angular momentum (WBAM) in the frontal plane during walking differs across age groups. We investigated age related differences in BPAM and WBAM during walking. We used marker coordinate data from a publicly available database for 54 individuals aged 20-30 years and 78 aged 60-70 years. Angular momentum in the frontal plane was calculated as the sum of the translational component and the rotational component for each segment. The angular momentum of each segment was categorized into five BPAM: right and left lower limbs (foot, shank, and thigh), right and left arms (hand, forearm, and upper arm), and torso (head, thorax, and pelvis). BPAM at WBAM peak frames during stride cycles was compared between older and younger adults. The peak WBAM, angular momentum of the stance-and swing side upper limbs, and torso in older adults was significantly larger than that in younger adults, with increases of 74.6% in the stance-side upper limb, 127.5% in the swing-side upper limb, and 30.9% in the torso. These results suggest that interventions aimed at improving torso control could decrease the amplitude of WBAM in the frontal plane in older adults.

Walking balance control in different settings: Effects of walking speed and biological sex

BACKGROUND

Previous research has suggested that spatiotemporal step parameters differ between settings; however, it remains unclear how different settings influence walking balance control.

RESEARCH QUESTION

How do settings and sex influence walking balance control during walking at different speeds for young adults?

METHODS

Forty-two adults (21 male (23 ± 4 years), 21 female (24 ± 5 years)) completed overground walking trials in four settings: laboratory (10 m), hallway, indoor open, and outdoor pathway (all 20 m) at three self-selected speeds (slow, preferred, fast) following verbal instructions. Participants wore 17 inertial sensors (Xsens Awinda, Movella, Henderson, NV) to capture total body kinematics. The number of included strides was matched across all conditions, with six strides included in each condition for all participants. Medial-lateral and anterior-posterior total body angular momentum range over each stride was calculated (HML range and HAP range). Setting × speed × sex mixed factorial analysis of variance with repeated measures on setting and speed were used for statistical analysis (α =.05).

RESULTS

Significant setting × speed interactions (p <.001) were present for both outcomes. HML range was greater in the laboratory and hallway compared to the indoor open and outdoor pathway settings for slow walking speed only. HAP range was lower in the outdoor pathway compared to all indoor settings at slow and preferred walking speeds. Differences in HAP range between settings was more pronounced at the slow speed condition. Across setting and speed conditions, HML range was greater for males compared to females.

SIGNIFICANCE

Young adults may alter their balance control strategy depending on the setting (laboratory, indoor open and outdoor pathway), particularly at slow speeds. Researchers and clinicians are cautioned not to assume walking in laboratory settings reflects walking in all settings nor that males and females can be examined as a single group.

The effect of amplitude normalization technique, walking speed, and reporting metric on whole-body angular momentum and its interpretation during normal gait

Whole-body angular momentum (WBAM) represents the cancellations of angular momenta that are produced during a reciprocal gait pattern. WBAM is sensitive to small changes and is used to compare dynamic gait patterns under different walking conditions. Study designs and the normalization techniques used to define WBAM vary and make comparisons between studies difficult. To address this problem, WBAM about each anatomical axis of rotation from a healthy control population during normal gait were investigated within four metrics: 1) range of WBAM, 2) integrated WBAM, 3) statistical parametric mapping (SPM), and 4) principal component analysis (PCA). These data were studied as a function of walking speed and normalization. Normalization techniques included: 1) no normalization, 2) normalization by height, body mass and walking speed, and 3) normalization by height, body mass and a scalar number, gravity×height, that is independent of walking velocity. Significant results were obtained as a function of walking speed regardless of normalization technique. However, the interpretation of significance within each metric was dependent on the normalization technique. Method 3 was the most robust technique as the differences were not altered from the expected relationships within the raw data. Method 2 actually inverted the expected relationship in WBAM amplitude as a function of walking speed, which skewed the results and their interpretation. Overall, SPM and PCA statistical methods provided better insights into differences that may be important. However, depending on the normalization technique used, caution is advised when interpreting significant findings when comparing participants with disparate walking speeds.

Lower-limb joint quasi-stiffness in the frontal and sagittal planes during walking at different step widths

Quasi-stiffness describes the intersegmental joint moment-angle relationship throughout the progression of a task. Previous work has explored sagittal-plane ankle quasi-stiffness and its application for the development of powered lower-limb assistive devices. However, frontal-plane quasi-stiffness remains largely unexplored but has important implications for the development of exoskeletons since clinical populations often walk with wider steps and rely on frontal-plane balance recovery strategies at the hip and ankle. This study aimed to characterize frontal-plane hip and ankle quasi-stiffness during walking and determine how step width affects quasi-stiffness in both the frontal and sagittal planes. Kinematic and kinetic data were collected and quasi-stiffness values computed for healthy young adults (n = 15) during treadmill walking across a range of step widths. We identified specific subphases of the gait cycle that exhibit linear and quadratic frontal-plane quasi-stiffness approximations for the hip and ankle, respectively. In addition, we found that at wider step widths, sagittal-plane ankle quasi-stiffness increased during early stance (∼12-35% gait cycle), sagittal-plane hip quasi-stiffness decreased in late stance (∼40-55% gait cycle) and frontal-plane hip quasi-stiffness decreased during terminal stance (∼48-65% gait cycle). These results provide a framework for further exploration of frontal-plane quasi-stiffness, lend insight into how quasi-stiffness may relate to balance control at various step widths, and motivate the development of stiffness-modulating assistive devices to improve balance related outcomes.

Load modulation affects pediatric lower limb joint moments during a step-up task

Performance in a single step has been suggested to be sensitive measure of movement quality in pediatric clinical populations. Although there is less information available in children with typical development, researchers have postulated the importance of analyzing the effect of body weight modulation on the initiation of stair ascent, especially during single limb stance where upright stability is most critical. The purpose of this study was to investigate the effect of load modulation from -20% to +15% of body weight on typical pediatric lower limb joint moments during a step-up task. Fourteen participants between 5-21 years with no known history of neurological or musculoskeletal concerns were recruited to perform multiple step-up trials. Peak extensor support and hip abduction moments were identified during the push-off and pull-up stance phases. Linear regressions were used to determine the relationship between peak moments and load. Mixed effects models were used to estimate the effect of load on hip, knee, and ankle percent contributions to peak support moments. There was a positive linear relationship between peak support moments and load in both stance phases, where these moments scaled with load. There was no relationship between peak hip abduction moments and load. While the ankle and knee were the primary contributors to the support moments, the hip contributed more than expected in the pull-up phase. Clinicians can use these results to contextualize movement differences in pediatric clinical populations including cerebral palsy and highlight potential target areas for rehabilitation for populations such as adolescent athletes.

The influence of step width on balance control and response strategies during perturbed walking in healthy young adults

Individuals with neuromuscular deficits often walk with wider step widths compared to healthy adults. Wider steps have been linked to a higher destabilizing frontal-plane external moment and greater range of frontal-plane whole-body angular momentum (HR), which is an indicator of decreased balance control. The purpose of this study was to experimentally determine 1) how step width alters balance control during steady-state walking, and 2) if step width changes the balance response strategies following mediolateral surface perturbations in healthy adults. Fifteen healthy young adults (7 male, age: 25 ± 4 years) walked on an instrumented treadmill at narrow, self-selected, wide and extra-wide step widths. During perturbed trials, the treadmill provided random mediolateral surface translations to each foot midway through single-leg-stance. Muscle electromyography, biomechanical measures (HR, frontal-plane external moment and joint moments) and deviations (differences in these measures between the perturbed and unperturbed walking trials) were compared across step widths. During steady state walking, wider steps were associated with decreased balance control. Increasing step widths were also associated with increased gluteus medius activity and reduced hip abduction and ankle inversion moments, which suggests healthy subjects rely more on a lateral ankle strategy to maintain balance at increasing step widths. There was no change in the plantarflexion moment. During perturbed walking, lateral, but not medial, surface translations adversely affected balance control. Further, wider steps did not change the balance response strategies following the perturbations, which suggests healthy individuals have the capacity to respond similarly to the perturbations at different step widths.

Influence of aging on the control of the whole-body angular momentum during volitional stepping: An UCM-based analysis

Evidence suggests that whole-body angular momentum (WBAM) is a highly controlled mechanical variable for performing our daily motor activities safely and efficiently. Recent findings have revealed that, compared to young adults, older adults exhibit larger range of WBAM during various motor tasks, such as walking and stepping. However, it remains unclear whether these age-related changes are ascribed to a poorer control of WBAM with age or not. The purpose of the present study was to examine the effect of normal aging on WBAM control during stepping. Twelve young adults and 14 healthy older adults performed a series of volitional stepping at their preferred selected speed. An Uncontrolled Manifold (UCM) analysis was conducted to explore the presence of synergies among the angular momenta of the body segments (elemental variables) to control WBAM (performance variable); i.e., to stabilize or destabilize it. Results revealed the existence of a stronger synergy destabilizing the WBAM in the sagittal-plane older adults compared to young adults during stepping, while there was no difference between the two groups in the frontal and transversal planes. Although older participants also had a larger range of WBAM in the sagittal plane compared to young adults, we found no significant correlation between synergy index and the range of WBAM in the sagittal plane. We concluded that the age-related changes in WBAM during stepping are not ascribed to alterations in the ability to control this variable with aging.

Influence of transcutaneous electrical nerve stimulation on walking kinematics and standing balance of older adults who differ in walking speed

The purpose was to determine the impact of transcutaneous electrical nerve stimulation (TENS) on measures of walking kinematics and standing balance of healthy older adults who were stratified into two groups based on differences in the distance walked during the 6-min test of walking endurance. Regression models were developed to explain the variance in the 6-min distance and to assess the predictive power of balance metrics to categorize the 26 older adults (72 ± 5.4 yrs) as either slow or fast walkers. Walking kinematics were measured during 6- and 2-min walk tests that were performed with and without the concurrent application of TENS to the hip flexor and ankle dorsiflexor muscles. Participants walked briskly during the 6-min test and at a preferred pace during the 2-min test. The supplementary sensory stimulation provided by TENS did not alter the power of the models to explain the variance in the Baseline 6-min distance: Baseline, R² = 0.85; TENS, R² = 0.83. In contrast, TENS improved the explanatory power of the data obtained during the 2-min walk to account for the variance in the Baseline 6-min distance: no TENS, R² = 0.40; TENS, R² = 0.64. Logistic regression models based on force-plate and kinematic data obtained during the balance tasks were able to discriminate between the two groups with excellent certainty. The impact of TENS was greatest when older adults walked at a preferred speed but not when they walked at a brisk pace or performed tests of standing balance.

Gait-phase specific transverse-plane momenta generation during pre-planned and late-cued 90 degree turns while walking

Turning while walking is ubiquitous and requires linear and angular momenta generation to redirect the body's trajectory and rotate towards the new direction of travel. This study examined strategies that healthy young adults used during each gait phase to generate transverse-plane momenta during pre-planned and late-cued 90° turns. During leftward turns, we expected that momenta would be generated most during the gait phases known to generate leftward linear and angular momenta during straight line gait. We found distinct roles of gait phases towards generating momenta during turns that partially supported our hypotheses. Supporting one hypothesis, the change in transverse-plane angular momentum and average moment were greater during double support with the left foot in front vs. other gait phases. Also, the change in leftward linear momentum and average leftward force were greater during right single support vs. other gait phases during straight-line gait and late-cued turns. However, during pre-planned turns, the average leftward force was not significantly greater during right single support vs. other gait phases. Overall, transverse-plane angular momentum generation during turns is similar to its generation during straight-line gait, suggesting that healthy young adults can leverage momenta control strategies used during straight-line gait during turns.

Extensive and Differential Deterioration of Hip Muscles May Preexist in Older Adults with Hip Fractures: Evidence from a Cross-Sectional Study

Hip muscles play an increasingly important role in lower limb function with aging. Investigating the deterioration of hip muscles and its relationship with hip fracture (HF) may help identify older adults prone to fall. In this study, patients with fall-related HF within 48 h and non-fracture controls aged ≥ 60 years were enrolled. The cross-sectional area (size) and attenuation (density) of the hip flexors, extensors, adductors, and abductors were calculated after segmentation on computed tomography images. The correlation of muscle parameters with HF and age were evaluated using logistic and multiple regression, respectively. Discrimination of HF was analyzed by receiver-operating characteristic analyses. A total of 220 patients and 91 controls were included. The size of the flexors, extensors, and abductors, and the density of the flexors, adductors, and abductors were lower in patients with HF after adjustment for sex, age, and body mass index (BMI). However, decreased muscle size was only observed in hip extensors in patients aged 60-74 years. Decreased muscle size was associated with HF independent of sex, age, BMI, and hip trabecular bone mineral density. Abductor size exhibited a significantly larger negative correlation with age in patients compared to controls. Including abductor size or all muscle size was effective for discrimination of HF in patients aged ≥ 75 years. In conclusion, older adults with HF may have sustained extensive and differential hip muscle deterioration before the injury; extensor atrophy in younger-old age and consideration of a closer relationship between abductor size and age deserve attention.

How Healthy Older Adults Enact Lateral Maneuvers While Walking

Background

Walking requires frequent maneuvers to navigate changing environments with shifting goals. Humans accomplish maneuvers and simultaneously maintain balance primarily by modulating their foot placement, but a direct trade-off between these two objectives has been proposed. As older adults rely more on foot placement to maintain lateral balance, they may be less able to adequately adapt stepping to perform lateral maneuvers.

Research Question

How do older adults adapt stepping to enact lateral lane-change maneuvers, and how do physical and perceived ability influence their task performance?

Methods

Twenty young (21.7 ± 2.6 yrs) and 18 older (71.6 ± 6.0 yrs) adults walked on a motorized treadmill in a virtual environment. Following an audible and visual cue, participants switched between two parallel paths, centered 0.6m apart, to continue walking on their new path. We quantified when participants initiated the maneuver following the cue, as well as their step width, lateral position, and stepping variability ellipses at each maneuver step.

Results

Young and older adults did not differ in when they initiated the maneuver, but participants with lower perceived ability took longer to do so. Young and older adults also did not exhibit differences in step width or lateral positions at any maneuver step, but participants with greater physical ability reached their new path faster. While only older adults exhibited stepping adaptations prior to initiating the maneuver, both groups traded-off stability for maneuverability to enact the lateral maneuver.

Significance

Physical and perceived balance ability, rather than age per se, differentially influenced maneuver task performance. Humans must make decisions related to the task of walking itself and do so based on both physical and perceived factors. Understanding and targeting these interactions may help improve walking performance among older adults.

Regulation of whole-body and segmental angular momentum in persons with Parkinson's disease on an irregular surface

BACKGROUND

Persons with Parkinson's disease have impaired motor control that increases their chance of falling when walking, especially on difficult terrains. This study investigated how persons with Parkinson's disease regulate their dynamic balance on a regular and an irregular surface.

METHODS

Nine participants with Parkinson's disease and nine healthy, age-matched control participants ambulated on both a regular and an irregular surface. Whole-body and segmental angular momenta were calculated using three-dimensional motion capture data. Major modes of variability between health groups on the two surfaces were investigated using principal component analysis, while differences within each health group between surfaces was investigated using statistical parametric mapping t-tests.

FINDINGS

Between groups, the Parkinson participants had greater sagittal, frontal, and transverse whole-body angular momentum on both surfaces, primarily following heel-strike, and the magnitude difference on the irregular surface was greater than on the regular surface. The greatest between group segmental differences on the irregular compared to the regular surface were the legs in the sagittal plane and the head/trunk/pelvis in the transverse plane, with the Parkinson group having greater magnitudes. The within-group comparison found the Parkinson participants had poorer regulation of whole-body angular momentum in the sagittal plane, while the healthy participants showed no consistent differences between surfaces.

INTERPRETATION

On an irregular surface, persons with Parkinson's disease exhibit poor control of dynamic balance in the frontal and sagittal planes. These results emphasize the need for weight transfer techniques and training in both the sagittal and frontal planes to maximize balance and reduce fall risk.

Changes in dynamic balance control in adults with obesity across walking speeds

Adults with obesity have gait instability, leading to increased fall risks and decreased physical activity. Whole-body angular momentum (WBAM) is regulated over a gait cycle, essential to avoid a fall. However, how obese adults regulate WBAM during walking is unknown. The current study investigated changes in WBAM about the body's center of mass (COM) during walking in obese and non-obese adults across different walking speeds. Twenty-eight young adults with obesity and normal weight walked barefoot at a fixed walking speed (FWS, 1.25 m/s) and at five different speeds based on their preferred walking speed (PWS): 50, 75, 100, 125, and 150 % of PWS. Adults with obesity walked slower with shorter step length, wider step width, and longer double support time (p < 0.01). The ranges of frontal- and transverse-plane WBAM were greater in obese adults (p < 0.01). We also found that the range of frontal-plane WBAM did not significantly change with walking speed (p > 0.05), while the range of transverse-plane WBAM increased with walking speed (p < 0.01). The ranges of frontal- and transverse-plane WBAM increased with the mediolateral ground reaction force and mediolateral moment arm (p < 0.01), which may be most affected by lateral foot placement relative to the body's COM. Our findings suggest that controlling mediolateral stability during walking is more challenging in obese adults, independent of their slow walking speed. Understanding whole-body rotational dynamics observed in obese walking provides an insight into the biomechanical link between obesity and gait instability, which may help find a way to reduce fall risks and increase physical activity.

Effects of age on dynamic balance measures and their correlation during walking across the adult lifespan

In this study, we aimed to discover (1) the effects of age on dynamic balance measures, including the margin of stability (MOS), whole-body angular momentum (H), and misalignment of the desired and measured centers of pressure (dCOP and mCOP, respectively) in the anteroposterior (AP) and mediolateral (ML) directions, (2) the relationship between gait parameters and these balance measures, and (3) the relationships between these balance measures. We used the kinetic and kinematic data of 151 participants aged 20–77 years from a publicly available database. Participants were divided into three groups: young, middle-aged, and old. The step width of the old group was higher than that of the young group. Age-related differences in dynamic measures were found in the ML direction and not in the AP direction: MOS, peak-to-peak range of H, and dCOP–mCOP in the old group were greater than in the young group. ML MOS positively correlated with the frontal peak-to-peak range of H. The ML peak-to-peak range of H positively correlated with ML dCOP–mCOP across the adult lifespan. Our findings provide new insights for understanding the effects of age on dynamic balance and the relationships between the metrics. Older adults walked with a larger step width, resulting in a large stability margin in the ML direction, although with increased moment and momentum around the center of mass in the frontal plane.

Frontal plane balance during pre-planned and late-cued 90 degree turns while walking

This study evaluated frontal-plane dynamic balance control during 90° left turns while walking. Ten healthy young adults performed straight-line gait, pre-planned turns, and turns cued visually (late-cued turns). We quantified rotational balance control via the range of frontal-plane angular momentum (Hf) about the center of mass (COM), and the relative positioning of the COM and the feet using the horizontal distance from the COM to the lateral edge of the base of support (lateral distance) and the mediolateral margin of stability (MOSml). We hypothesized that the Hf range would increase and the lateral distance and MOSml minima would decrease during each turn type vs. straight-line gait and during late-cued vs. pre-planned turns. We found that the range of Hf was significantly greater during each turn type vs. straight-line gait and during late-cued vs. pre-planned turns. Also, the lateral distance minima were significantly smaller during turns vs. straight-line gait, and during pre-planned vs. late-cued turns. Our hypotheses about MOSml were partially supported because the MOSml minima patterns were specific to right or left steps and were not significantly different between straight-line gait and pre-planned turns overall, but the right step's MOSml minima were more negative during late-cued vs. pre-planned turns and between either turn and straight-line gait. Finally, we observed slower gait speeds, fewer footfalls, shorter turn phase duration, and different turn strategies used during late-cued vs. pre-planned turns. Overall, these findings reveal multifaceted control of frontal-plane balance during turns encountered during everyday mobility.