Age-related reduction in sagittal plane center of mass motion during obstacle crossing
Introduction
Accidental falls are the leading cause of injury for persons over the age of 65 and the leading cause of death in persons over the age of 85 (Pocinki, 1990). Hip fractures resulting from falls can be costly, with an overall cost of each fracture estimated at $35,000. Of these elderly adults who suffer from a hip fracture, 25% make a full recovery, 40% require nursing home admission, and 50% of all hip fracture patients require a cane or walker for assisted ambulation (AAOS, 1998). Not as easily measured is the psychological impact of these falls and subsequent fractures. Tinetti and Speechley (1989) proposed that the psychological trauma of an injurious fall may induce a reduction in activity levels, followed by strength reduction, leading to ever-increasing risk of future falls. It is therefore evident that falls are frequent, costly, and potentially debilitating (both physically and psychologically) in the aging population.
Imbalance and tripping over obstacles during gait were reported as two of the most common causes of falls in the elderly (Overstall et al., 1977; Blake et al., 1988; Tinetti and Speechley, 1989; Campbell et al., 1990). Several gait studies were performed to study the effect of obstacle height on the joint kinematics and kinetics (McFadyen and Winter, 1991; Patla and Rietdyk, 1993; Chou and Draganich (1997), Chou and Draganich (1998)) of either the trailing (i.e., limb crossing the obstacle last) or leading (i.e., limb crossing the obstacle first) limb. It was demonstrated that greater joint motion of both lower limbs during swing and greater joint kinetic demands (forces and torques) of the trailing limb during stance are required in young adults when stepping over an obstacle. Healthy elderly adults were reported to adopt a more conservative strategy when crossing obstacles, with slower crossing speed, shorter step length, and smaller step width, than young adults and demonstrated an increased risk for obstacle contact (Chen et al (1991), Chen et al. (1994)). Recent studies further revealed that, compared to young adults, limited frontal plane pelvic motion, shorter stride length, kinetic accommodation in the sagittal plane, and non-optimal foot placement might be contributing factors to a greater risk of tripping in elderly adults (Begg and Sparrow, 2000; McFadyen and Prince, 2002). However, no information about age-related differences in balance maintenance while negotiating obstacles was reported. To better understand mechanisms underlying the increased incidence of tripping and falling in the elderly, it is necessary to monitor the whole body's response during obstacle crossing.
It may be that the natural processes of aging do not directly affect dynamic stability, but that age-associated pathologies (i.e., vestibular hypofunction, peripheral neuropathy, osteoarthritis, etc.) are more responsible for reductions in dynamic stability. Control of dynamic balance is challenged by the extrinsic risks encountered during locomotion. When balance is perturbed, the control system applies a series of reactive and feed- forward corrections via the musculoskeletal system to continuously maintain whole body center of mass (COM) trajectory within close range of the center of pressure (COP). A few studies reported the adequacy of the COM–COP interaction in demonstrating dynamic stability (balance control during locomotion), with a consistent COM trajectory passing between the alternating COP of each supporting foot (Jian et al., 1993; MacKinnon and Winter, 1993; Prince et al., 1994; Winter, 1995). Recent results showed that COM medio- lateral (M/L) displacement and peak M/L velocity during obstacle crossing could be used to better detect dynamic instability in elderly adults (Chou et al (2001), Chou et al (2003)).
The purpose of this study was to determine the age-related differences in dynamic stability between healthy young and elderly adults during level walking and obstacle crossing tasks. It was hypothesized that there would be age-related differences in the measures of whole body dynamic stability. Specifically, it was expected that the COM trajectory would be conservatively adjusted to remain closer to the COP in elderly adults, as compared to young adults.
Section snippets
Methods
Thirteen young adults (7 male/6 female; 25.7±3.6 years, 171.8±9.2 cm, 74.2±13.1 kg) and thirteen elderly adults (8 male/5 female; 72.8±6.0 years, 168.9±11.4 cm, 72.2±14.8 kg) were recruited for this study from the University of Oregon campus and surrounding community, within the guidelines of the Institutional Review Board. Elderly subjects were noted to be active community members, with many of them currently involved in recreational sporting activities. Informed consent was obtained from each
Results
Initial screening indicated that 19 individual data points were outside reasonable variability (±3 inter-quartile ranges). Of the 6630 total data points in the analysis (17 variables×26 subjects×5 conditions×3 trials), the outlying data accounted for only 0.3% of the total data collected. Removal of these data from the analysis was therefore justified.
All subjects were able to complete the condition trials with no incidents of tripping. No significant age group differences were found for any of
Discussion
As age-related declines occur in the balance control system, it is reasonable to expect that a reduced ability to maintain dynamic stability would be evident in altered patterns of COM motion and its coordination with the COP. Results from this study revealed that there are age-dependent decreases in A/P ROM of the COM, maximum anterior COM–COP distance allowed, and the instantaneous anterior COM velocity at the timing of maximum anterior or posterior COM–COP separation. These significant
Acknowledgments
This work was supported by the Oregon Medical Research Foundation, National Institutes of Health (HD042039-01A1 and AG022204-01) and the International Society of Biomechanics Dissertation Matching Grant. The authors gratefully acknowledge the assistance of Heng-Ju Lee and Marisa Hastie in data collection and analysis.
References (31)
- et al.
Prediction of hip joint center location from external landmarks
Human Movement Science
(1989) - et al.
Age effects on strategies used to avoid obstacles
Gait and Posture
(1994) - et al.
Stepping over an obstacle increases the motions and moments of the joints of the trailing limb in young adults
Journal of Biomechanics
(1997) - et al.
Placing the trailing foot closer to an obstacle reduces flexion of the hip, knee, and ankle to increase the risk of tripping
Journal of Biomechanics
(1998) - et al.
Motion of the whole body's center of mass when stepping over obstacles of different heights
Gait and Posture
(2001) - et al.
Medio-lateral motion of the center of mass during obstacle crossing distinguishes elderly individuals with imbalance
Gait and Posture
(2003) - et al.
Mini-mental statea practical method for grading the cognitive state of patients for clinicians
Journal of Psychiatric Research
(1975) - et al.
Trajectory of the body COG and COP during initiation and termination of gait
Gait and Posture
(1993) - et al.
Control of whole body balance in the frontal plane during human walking
Journal of Biomechanics
(1993) - et al.
Center of mass velocity-position predictions for balance control
Journal of Biomechanics
(1997)
Visual control of limb trajectory over obstacles during locomotioneffect of obstacle height and width
Gait and Posture
Anticipatory control of upper body balance during human locomotion
Gait and Posture
A FORTRAN package for generalized, cross-validatory spline smoothing and differentiation
Advances in Engineering Software
Gait characteristics of young and older individuals negotiating a raised surfaceimplications for the prevention of falls
Journal of Gerontology
Cited by (187)
Slowing down to preserve balance in the presence of optical flow perturbations
2022, Gait and PostureDon't get tripped up: Haptic modalities alter gait characteristics during obstacle crossing
2022, Human Movement ScienceLower limb muscle activation in response to balance-perturbed tasks during walking in older adults: A systematic review
2022, Gait and PostureCitation Excerpt :Therefore, proper muscular reactions to balance perturbations are critical to ensure safe performance of daily activities, such as walking. Many physical and cognitive events encountered during walking have been reported to perturb balance control [5–8]. Adjustments in muscular activation in terms of magnitude, timing, and agonist-antagonist co-contraction are important for maintaining gait balance.
Stability region derived by center of mass for older adults during trivial movements
2021, Biomedical Signal Processing and ControlInclination angles during cross-slope roof walking
2020, Safety Science