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Effect of Age and Activity Level on Lower Extremity Gait Dynamics: An Introductory Study

Cabell, Lee1; Pienkowski, David2,3; Shapiro, Robert4; Janura, Miroslav5

Journal of Strength and Conditioning Research: June 2013 - Volume 27 - Issue 6 - p 1503–1510
doi: 10.1519/JSC.0b013e318269f83d
Original Research
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Cabell, L, Pienkowski, D, Shapiro, R, and Janura, M. Effect of age and activity level on lower extremity gait dynamics: An introductory study. J Strength Cond Res 27(6): 1503–1510, 2013—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.

1Department of Graduate Programs in Health Sciences, School of Health and Medical Sciences, Seton Hall University, South Orange, New Jersey

2Center for Biomedical Engineering, University of Kentucky, Lexington, Kentucky

Department of 3Orthopaedic Surgery, School of Medicine; and

4Kinesiology and Health Promotion, University of Kentucky, Lexington, Kentucky

5Department of Biomechanics and Engineering Cybernetics, Faculty of Physical Culture, Palacky University, Olomouc, Czech Republic

Address correspondence to Lee Cabell, lee.cabell@shu.edu.

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Introduction

Being physically active is an important part of leading a healthy lifestyle. However, it is especially important that seniors engage in regular exercise to maintain proper health and fitness. As we age, age-related musculoskeletal changes lead not only to stiff and less flexible joints but also have more serious consequences when these changes impair balance and gait. They may subsequently result in falls, hip fracture, loss of independence, and elevated risk of disability and death. Ninety percent of the more than 352,000 hip fractures in the United States each year are the result of a fall. By the year 2050, there will be an estimated 650,000 hip fractures annually. This is nearly 1,800 hip fractures per day (15). Factors responsible for falling were investigated in a study of community-dwelling elderly women, which focused on the effect of combined exercise training on bone, body balance, and gait ability (44,50); however, further research is required to elucidate specific balance and gait indicators of potential fall risk, including the possible role of abnormal function of intrinsic dynamic postural control strategies.

The relationships among aging, musculoskeletal system changes, and gait alterations are poorly understood because not all older adults experience similar changes in physical function. Several studies (27,28,33) have investigated age-related changes in gait, specifically the slower more stable gait pattern of some older adults that occurs during unobstructed walking (19,29,32,54,55) or on a raised surface (5). Such altered gait patterns may be an adaptation to declines in postural control abilities. Most falls occur during dynamic activities such as walking, but performance in standing-balance stability assessments has also produced significant results (23). Other studies demonstrated a significant age-related decline in functional mobility (28,42) or differences in muscle power between young and elderly men (49). It can be expected that aging effects will be pronounced in gait conditions that demand more strength in the subject's movements (35).

Many researchers have developed exercise programs aimed at improving balance and preventing falls, with some success. Studies on fall prevention suggest that exercise programs aimed at improving balance are effective in reducing the incidence of falls and fall-related injuries among the older women (20,25,36). In older women with low bone mass, group-based exercises have a beneficial effect on fall risk profiles and physical activity even 1 year after the withdrawal of the exercise program (38). Additionally, a balance training program has been shown to be highly effective in improving functional status and reducing the risk of falls in elderly women with osteoporosis. For example, Gillespie et al. (20) concluded in a review that individualized programs targeting balance and muscle strengthening were effective in enhancing balance among older adults. Similarly, Chang et al. (9) reported that exercise programs focused on improving balance, muscle strength, endurance, and flexibility showed a 22% reduction in the occurrence of falls and a 15% reduction in fall risk. In addition to conventional exercise training, as discussed above, other types of fall prevention measures are reported in the literature, for example, practice of Tai Chi has been reported to improve balance and, ultimately, prevent falls (34).

Because aging is the product of an interaction between genetic, environmental, and lifestyle factors (21), contributions from each may cause differences in physical abilities among older adults, which must be taken into consideration by conditioning and strength training professionals before devising individualized exercise regimens for their clients. Moreover, any model attempting to identify older adults predisposed to musculoskeletal impairments, falling, or fracture also should consider the effects of these factors (2,8,47).

Coaches or strength and conditioning professionals may wish to identify seniors predisposed to adverse, age-related, musculoskeletal gait-related changes that may be indicative of underlying postural control abnormalities. This is important because early therapeutic intervention strategies that reduce the risk of falling and hip fracture may be developed. Toulotte et al. (51) identified fallers under dual-task conditions with a single-leg balance test; others measured joint angles at critical events in the gait cycle that provided a useful indication of age-related degeneration in the control of lower limb trajectories (6). Efforts seeking to identify those at greater risk of falling, and implement preventative measures, are clinically, economically, and ethically preferable to those who merely advance the treatment of the resulting musculoskeletal injury and disability (7,13,30,49). The purpose of the present study was to determine if relevant kinematics and kinetics of the lower extremity joints during gait differ as a function of age or activity level between young and elderly women.

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Methods

Experimental Approach to the Problem

Subjects were classified as active or sedentary based on the Centers for Disease Control/American College of Sports Medicine physical activity guidelines (4). Subjects were classified as active if they reported at least 30 minutes of exercise for 5 days per week.

To determine the dynamic changes in the joints of the lower extremity, a gait cycle was studied. The walking cycle was divided into 2 phases and normalized: right stance phase (60% of the cycle) and right swing phase (40% of the cycle). The right stance phase was evaluated at 3 events for kinematic analysis: heel strike (HS), midstance (MS), and toe off (TO). A fourth event, initial peak vertical ground reaction force (VGRF), was added for the kinetic analysis. The HS, TO, and VGRF were identified from the force platform output, and MS was defined as the time when the tibia was perpendicular to the ground. The basic gait temporospatial parameters were obtained, and 3-dimensional (3D) angular displacement, velocity, and acceleration were calculated for the hip, knee, and ankle joints. Three-dimensional internal moments were also determined for hip, knee, and ankle joints of the right leg (45) by using OrthoTrak II software (Motion Analysis, Corp., Santa Rosa, CA, USA). Data analysis was limited to the right leg. The effects of leg dominance were neglected in this preliminary study.

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Subjects

Seventeen healthy female subjects (Table 1) without a history of falling or musculoskeletal trauma, congenital disorders, or abnormality participated in this study. Subjects provided written informed consent as approved by the University Institutional Review Board.

Table 1

Table 1

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Experimental Procedures

While the subjects were standing in their own street shoes and wearing tight shorts (provided), they were marked for video analysis with the basic simplified (“Helen Hayes”) marker set of 15 retroreflective external markers. These markers were attached to specific anatomical locations on the shorts and skin of the subjects' lower extremities (26). This marker set minimized the number of markers to simplify trajectory identification. Markers were placed (bilaterally) on the following anatomical locations: (a) anterior superior iliac spine, (b) mid-thigh marker-on-wand (collinear with markers on the greater trochanter and the lateral knee), (c) knee directly lateral to the estimated axis of rotation, (d) mid-shank marker-on-wand, (e) lateral malleolus, (f) toe, between second and third metatarsal heads, and (g) heel. A 15th marker was placed on the sacrum.

Instrumented subjects were then instructed to walk at a self-selected pace across a force platform centered within a 20-m gait laboratory walkway. Each subject performed a minimum of 3 practice walking trials, allowing them to adjust their starting point so that the right foot naturally (and completely) contacted the force plate during each trial. Investigators observed each gait trial, eliminating those trials where subjects missed or “targeted” the force platform. Data collected during 3 successful walking trials were averaged for each subject.

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Instrumentation and Data Processing

Video image data were obtained from 5 high-resolution video cameras (FALCON HR 240; Motion Analysis, Corp.). Sampling at 60 Hz, the video cameras were located such that at least 2 cameras could view each marker at any time—a requirement for the subsequent 3D image reconstruction that was performed by the direct linear transformation algorithm (1). The resulting 3D coordinate data for each marker were filtered with a low-pass fourth-order Butterworth filter with a cutoff frequency of 6 Hz (54) (EvA Software; Motion Analysis, Corp.). The ground reaction forces (GRFs) were measured with a piezoelectric force platform (Model 9261A; Kistler Instrumentation, Corp., Winterthur, Switzerland). The analog force data were converted to digital signals and sampled using an analog-to-digital board (Model 2821-F-16SE; Data Translation, Marlboro, MA, USA) at a nominal rate of 1,000 Hz per channel and synchronized with the video measurements. All data were stored on a SUN SPARC workstation (Sun Microsystems, Inc., Mountain View, CA, USA).

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Statistical Analyses

The kinematic and kinetic data were initially analyzed using a 2-factor (independent variables: age and activity level) analysis of variance. A Scheffe analysis based on Fisher's least significant difference procedure was used for all post hoc pair-wise comparisons (SAS, version 9.1.3; SAS Institute, Inc., Cary, NC, USA). The level of significance was set at 0.05. The desired power of the study was 0.8 for the differences in the variables noted in this study.

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Results

All data are presented as mean ± SD. Spatiotemporal gait characteristics of the young (n = 9) and elderly (n = 8) subject groups were not significantly different, except for normalized stride length (Table 2). The direction of ankle angular acceleration of young subjects (plantarflexion) was different (p = 0.0002) from the elderly subjects (dorsiflexion) at mid-stance (Table 3). Young subjects exhibited an eversion moment about the ankle, and this differed (p = 0.006) from the elderly subjects who exhibited an inversion moment (at the time the maximal GRF was produced; Table 4). Knee angular velocity about the long axis of the tibia of the younger subjects, measured at TO, was different (p = 0.002) from the elderly subjects in magnitude and direction, with the young subjects exhibiting internal rotation (Table 5). No other gait parameters of the lower extremity joints differed as a function of age.

Table 2

Table 2

Table 3

Table 3

Table 4

Table 4

Table 5

Table 5

The magnitude and direction of the frontal plane knee moment differed between active and sedentary groups (p = 0.04) during TO. The active group demonstrated a varus-directed moment, whereas the sedentary group demonstrated a valgus moment (Table 6). No other gait-related differences were observed in the knee. Parameters at the hips of active adults showed 4 significant differences when compared with the hip dynamics of sedentary adults. Active adults had (a) greater abduction at TO (Table 7), (b) internal rotation at HS while sedentary group had external rotation (Table 8), (c) external rotation during mid-stance while sedentary had internal rotation (Table 8), and (d) greater external rotation at TO moment (Table 9) compared with the sedentary adults. No other gait parameters of any lower extremity joints were significantly different as a function of activity level. The above significant changes were observed in the direction of hip motion (note the change in sign of the entries in Tables 7–9). The results of this study show that age and activity level affect the biodynamics of the lower extremity during gait (Figure 1).

Table 6

Table 6

Table 7

Table 7

Table 8

Table 8

Table 9

Table 9

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Discussion

The purpose of this preliminary study was to investigate potential relationships among gait-related biomechanics parameters, age, and physical activity level of female subjects that might be useful in understanding hip fracture and related injuries. The results also suggest that age and activity level interact and thus cannot be considered in isolation.

Figure 1

Figure 1

When groups were compared based on activity level, the greatest number of differences among biodynamic variables was observed at the hip. These data might be interpreted as an indication that the hip is more acutely sensitive to changes in postural control and balance during activity than either the knee or the ankle. The knee showed only 2 parameters that were significantly different—one a function of activity level, and the other a function of age. One could conclude that the knee is less sensitive to changes in activity level or age than the hip or the ankle (respectively). Alternatively, it could be inferred that the effects of activity or age begin at the hip or ankle (respectively) and then progress either distally or proximally, with the knee demonstrating no significant alterations.

Biodynamic differences observed at the ankle were primarily age-related, but activity level may also affect age-related changes. These effects on the ankle may be partially because of the high-amplitude repetitive loading experienced by this most-distal lower extremity joint. More specifically, variation in the magnitude and direction of the ankle moments in the frontal plane during inversion may have contributed to the sizeable increase in ankle angular acceleration observed in the older women. The dominant ankle invertors may provide the older women with a more secure position because at full-weight acceptance, the eccentric inversion moment holds the foot in a rigid position to control motion. Also, these differences in ankle parameters may reflect a controlled hip strategy where the subject is maintaining balance by using hip and lower trunk musculature (14) to make fine discriminatory adjustments during gait.

Normalized shorter step lengths in the elderly may be explained by changes in the dorsiflexed ankle angular accelerations that were noted at MS. The increased dorsiflexion angular acceleration observed in the older women may have been because of less force production during plantarflexor eccentric contraction, which may in turn result in shifting of the center of mass off the base of support, potentially contributing to an increased potential for a trip-induced fall at the critical time at MS. The activation of the plantarflexors is carefully managed because these propulsive muscles add mechanical energy to the system (41). The walking speed of the subject also affects muscle function and the production of mechanical energy during gait movement. Reported plantarflexor weakness in the elderly, measured by Cheal et al. (11), may help to explain why the elderly experience limb instability during single-leg stance. Plantarflexor weakness, the timing of muscle activation, and resulting increased ankle angular acceleration during dorsiflexion tend to cause the body to pitch forward faster during the single-leg support phase. To compensate, the swing leg is then placed on the ground sooner to quickly establish balance during the double limb support phase. This walking pattern, manifested via a reduced normalized stride length, may be a symptom of decreased postural stability, which may increase the likelihood of falling and sustaining a hip fracture. Based on this evidence, therapeutic programs for elderly individuals should target maintenance of flexibility, strengthening of ankle plantarflexors, and strengthening knee extensors (32).

Aging induces a shift in joint power production during walking, reduced ankle plantarflexor power during push off, and increased hip flexor power during late stance or hip extensor power during early stance and MS (40,46). Older adults experience both active and passive contributions to joint kinetics while walking. The observed higher external hip rotation velocity at HS in the sedentary group might also support Smith's (48) description of hip fractures. He suggested that faster external rotation of the hip produced a greater anterior bending moment across the femoral neck. Muscle weakness in sedentary females may lead to poor motor control and, therefore, increased hip rotational velocity at HS that may increase the amplitude of bone loading. This in turn may produce a greater propensity for a fatigue-related femoral neck fracture mechanism, which is then followed by a fall. Specifically, Hayes et al. (24) reported that 90% of hip fractures are the result of falls, but the order of these events is often unrecognized (42).

Hip angular adduction followed by abduction before TO is experienced in the stance as one limb is loaded and then unloaded in the normal population (12). The muscle moments responsible for this control are predominantly abductor in origin and result from the need to control the large mass of the head-arms-trunk that are working against the demands of gravity and balance (37). The active subjects in this investigation demonstrated a small hip abductor angular change, whereas the sedentary subjects remained in adduction before TO. This difference helps to explain the weakness in the sedentary population's abductor muscle group. The normal healthy population has a valgus (abductor) knee moment during stance that changes to a small varus (adductor) moment as the knee unloads before TO (3). As expected, the active subjects showed a small normalized varus moment before TO when an unloading in the lateral (fibular) collateral ligament occurs. The sedentary subjects, however, experienced a valgus knee moment before TO, which may be the result of abductor muscle weakness that already influenced the hip angular position in the frontal plane.

Although the reduced peak hip extension that was observed by others (27,33) was not observed in this study, the present findings were in agreement with those observed by other investigators (18) and support the suggestion that inactivity may be partially responsible for musculoskeletal dysfunction (22,39).

Limitations of this study include the relatively small sample size in each of the groups. Nevertheless, within these study populations, significant differences were observed that await verification in future studies employing larger sample sizes. The study may also be adversely affected by other uncontrolled (unknown) variables, for example, lifestyle of the older women during their youth, genetic predisposition, usage of prescription drugs, and so on. The existence of these as-yet unknown variables is suggested by the presence of the large SDs. This is not a serious detraction from the study but rather an indication of a multifactorial event for which we currently have incomplete information.

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Practical Applications

The results of this study suggest that, for their elderly clients in particular, coaches and strength and conditioning trainers should encourage maintenance of an active lifestyle, including exercises that combine resistance, flexibility, and low-intensity movements of the lower limbs. Exercise routines aimed at coordinating movements about specific lower extremity joints (i.e., the ankle) may need to be added to remedy specific deficits. Even short-term resistance training readily increased knee isokinetic (10–18.5%) and 1 repetition maximum strength (107–227%) of older women (174 ± 31%) (16) and was well tolerated (10). This may reduce the age-related and activity-related loss of coordination that predisposes one to an increased susceptibility to falling. Exercises that exclusively improve aerobic capacity or muscle strength may not have a beneficial effect upon dynamic stability. However, this tactic is debated because studies examining the effects of physical activity on balance control have shown conflicting results (16,52).

Strength and conditioning professionals may best serve their older clients by suggesting participation in low-intensity activities such as walking, light jogging, golf, and Tai Chi Chuan exercises that increase strength and balance. These activities provide the same benefits to the ankle joint as high-intensity activities without the added risk of injury associated with high-intensity activities (often inappropriate for older adults), such as running or racquet sports. Moreover, practice of such exercises has been shown to decrease incidence and risk of falls (9,34). For older or sedentary clients, low-energy intensity activities might also be better than exercise machine-based resistance training because such low-energy activities are performed in 3 dimensions, as opposed to the single planes of controlled motion found in most machines, and resistance training alone may have only a modest effect on improving mobility.

Water-borne or walking-related exercise programs are the most easily started and maintained and should be recommended to nearly all sedentary and active elderly persons. Training that combines resistance, flexibility, and low-energy activities, either sequentially or simultaneously, may be the most beneficial to the aging population. Coaches and trainers should pay special attention to exercises that focus on the ankle joints of elderly clients. For those clients who are sedentary as well, trainers should incorporate exercises specifically targeting the hip joints.

A gait and balance evaluation may be useful to assess individual client needs and possible predisposition to musculoskeletal dysfunctions, such as a potential trip-induced fall or a nontraumatic hip fracture, which may assist conditioning professionals in individualizing prophylactic and maintenance exercise regimens. Further research applying appropriate interventions to prevent and correct age- and activity-related gait deficits is merited.

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References

1. Abdel-Aziz YI, Karara HM. Direct linear transformation from comparator coordinates into object space coordinates in close-range photogrammetry. In: Proceedings of the ASP/UI Symposium on Close Range Photogrammetry. Falls Church, VA, American Society of Photogrammetry, 1971. pp. 1–18.
2. Advani S, Wimalawansa SJ. Bones and nutrition: Common sense supplementation for osteoporosis. Curr Womens Health Rep 3: 187–192, 2003.
3. Allard P. Three-Dimensional Analysis of Human Locomotion. Toronto, Canada: Wiley, 1997.
4. American College of Sports Medicine (ACSM). The recommended quantity and quality of exercise for developing and maintaining cardiorespiratory and muscular fitness, and flexibility in healthy adults. Med Sci Sports Exerc 30: 975–991, 1998.
5. Begg RK, Sparrow WA. Gait characteristics of young and older individuals negotiating a raised surface: Implication for the prevention of falls. J Gerontol A Biol Sci Med Sci 55: 147–154, 2000.
6. Begg RK, Sparrow WA. Aging effects on knee and ankle joint angles at key events and phases of the gait cycle. J Med Eng Technol 30: 382–389, 2006.
7. Boulgarides LK, McGinty SM, Willet JA, Barnes CW. Use of clinical and impairment-based tests to predict falls by community-dwelling older adults. Phys Ther 83: 328–339, 2003.
8. Chan BKS, Marshall LM, Winters KM, Faulkner KA, Schwartz AV, Orwoll ES. Incident fall risk and physical activity and physical performance among older men the osteoporotic fractures in men study. Am J Epidemiol 165: 696–703, 2007.
9. Chang JT, Morton SC, Rubenstein LZ, Mojica WA, Maglione M, Suttorp MJ, Roth EA, Shekelle PG. Interventions for the prevention of falls in older adults: Systematic review and meta-analysis of randomized clinical trials. BMJ 328: 680, 2004.
10. Charette SL, McEvoy L, Pyka G, Snow-Harter C, Guido D, Wiswell RA, Marcus R. Muscle hypertrophy response to resistance training in older women. J Appl Physiol 70: 1912–1916, 1991.
11. Cheal EJ, Spector M, Hayes WC. Role of loads and prosthesis material properties on the mechanics of the proximal femur after total hip arthroplasty. J Orthop Res 10: 405–422, 1992.
12. Craik RL, Oatis CA. Gait Analysis—Theory and Application. St. Louis, MO: Mosby-Year Book, 1995.
13. Dargent-Molina P, Douchin MN, Cormier C, Meunier PJ, Breart G. Use of clinical risk factors in elderly women with low bone mineral density to identify women at higher risk of hip fracture: The EPIDOS prospective study. Osteoporos Int 13: 593–599, 2002.
14. Dreeben O. Physical Therapy Clinical Handbook. Sudbury, MA: Jones and Bartlett Publishers, 2007.
15. Falls and Hip Fractures. CDC Website. Available at: http://orthoinfo.aaos.org/topic.cfm?topic=A00121. Accessed May 19, 2012.
16. Feskanich D, Willett W, Colditz G. Walking and leisure-time activity and risk of hip fracture in postmenopausal women. JAMA 13: 2300–2306, 2002.
17. Fiatarone MA, Marks EC, Ryan ND, Meredith CN, Lipsitz LA, Evans WJ. High-intensity strength training in nonagenarians. Effects on skeletal muscle. JAMA 13: 3029–3034, 1990.
18. Finley FR, Cody KA. Locomotive characteristics of urban pedestrians. Arch Phys Med Rehabil 51: 423–426, 1970.
19. Frigo C, Tesio L. Speed-dependent variations of lower-limb joint angles during walking. A graphic computerized method showing individual patterns. Am J Phys Med 65: 51–62, 1992.
20. Gillespie LD, Robertson MC, Gillespie WJ, Sherrington C, Gates S, Clemson LM, Lamb SE. Interventions for preventing fall in older people living in the community. Cochrane Database Syst Rev 2012;CD007146.
21. Gonos ES. Genetics of aging: Lessons from centenarians. Exp Gerontol 35: 15–21, 2000.
22. Gorevic PD. Osteoarthritis. A review of musculoskeletal aging and treatment issues in geriatric patients. Geriatrics 59: 28–32, 2004.
23. Granata KP, Lockhart TE. Dynamic stability differences in fall-prone and healthy adults. J Electromyogr Kinesiol 18: 172–178, 2008.
24. Hayes WC, Myers ER, Morris JN, Gerhart TN, Yett HS, Lipsitz LA. Impact near the hip dominates fracture risk in elderly nursing home residents who fall. Calcif Tissue Int 52: 192–198, 1993.
25. Howe TE, Rochester L, Jackson A, Banks PMH, Blair VA. Exercise for improving balance in older people. Cochrane Database Syst Rev 2007;CD004963.
26. Kadaba MP, Ramakrishnan HK, Wootten ME. Measurement of lower extremity kinematics during level walking. J Orthop Res 8: 383–392, 1990.
27. Kerrigan DC, Lee LW, Collins JJ, Riley PO, Lipsitz LA. Reduced hip extension during walking: Healthy elderly and fallers versus young adults. Arch Phys Med Rehabil 82: 26–30, 2001.
28. Kerrigan DC, Lee LW, Nieto TJ, Markman JD, Collins JJ, Riley PO. Kinetic alterations independent of walking speed in elderly fallers. Arch Phys Med Rehabil 81: 730–735, 2000.
29. Kimura T, Kobayashi H, Nakayama E, Hanaoka M. Effects of aging on gait patterns in the healthy elderly. J Anthropol Sci 115: 67–72, 2007.
30. Ko S, Ling SM, Winters J, Ferrucci L. Age-related mechanical work expenditure during normal walking: The Baltimore longitudinal study of aging. J Biomech 42: 1834–1839, 2009.
31. Laughton CA, Slavin M, Katdare K, Nolan L, Bean JF, Kerrigan DC, Phillips E, Lipsitz LA, Collins JJ. Aging, muscle activity, and balance control: Physiologic changes associated with balance impairment. Gait Posture 18: 101–108, 2003.
32. Lee JH, Chun MH, Jang DH, Ahn JS, Yoo JY. A comparison of young and old using three-dimensional motion analyses of gait, sit-to-stand and upper extremity performance. Aging Clin Exp Res 19: 451–456, 2007.
33. Lee LW, Zavarei K, Evans J, Lelas JJ, Riley PO, Kerrigan DC. Reduced hip extension in the elderly: Dynamic or postural? Arch Phys Med Rehabil 86: 1851–1854, 2005.
34. Lin MR, Hwang HF, Wang YW, Chang SH, Wolf SL. Community-based Tai Chi and its effect on injurious falls, balance, gait, and fear of falling in older people. Phys Ther 86: 1189–1201, 2006.
35. Liu J, Lockhart TE. Comparison of 3D joint moments using local and global inverse dynamics approaches among three different age groups. Gait Posture 23: 480–485, 2006.
36. Liu-Ambrose TY, Khan KM, Eng JJ, Gillies GL, Lord SR, McKay HA. The beneficial effects of group-based exercises on fall risk profile and physical activity persist 1 year post intervention in older women with low bone mass: Follow-up after withdrawal of exercise. J Am Geriatr Soc 53: 1767–1773, 2005.
37. MacKinnon C, Winter DA. Control of whole body balance in the frontal plane during human walking. J Biomech 26: 633, 1993.
38. Madureira MM, Takayama L, Gallinaro AL, Caparbo VF, Costa RA, Pereira RM. Balance training program is highly effective in improving functional status and reducing the risk of falls in elderly women with osteoporosis: A randomized controlled trial. Osteoporos Int 18: 419–425, 2007.
39. Masdeu J, Sudarsky L, Wolfson L. Gait Disorders of Aging-Falls and Therapeutic Strategies. Philadelphia, PA: Lippincot-Raven Publishers, 1997.
40. Monaco V, Rinaldi LA, Macrì G, Micera S. During walking elders increase efforts at proximal joints and keep low kinetics at the ankle. Clin Biomech (Bristol, Avon) 24: 493–498, 2009.
41. Neptune RR, Sasaki K, Kautz SA. The effect of walking speed on muscle function and mechanical energetics. Gait Posture 28: 135–143, 2007.
42. Nevitt MC, Cummings SR, Kidd SR, Black D. Risk factors for recurrent nonsyncopal falls: A prospective study. JAMA 261: 2663–2668, 1989.
43. Owings TM, Grabiner MD. Variability of step kinematics in young and older adults. Gait Posture 20: 26–29, 2004.
44. Park H, Kim KJ, Komatsu T, Park SK, Mutoh Y. Effect of combined exercise training on bone, body balance, and gait ability: A randomized controlled study in community-dwelling elderly women. J Bone Miner Metab 26: 254–259, 2008.
45. Perry J. Gait Analysis—Normal and Pathological Function. Thorofare, NJ: SLACK Incorporated, 1992.
46. Silder A, Heiderscheit B, Thelen DG. Active and passive contributions to joint kinetics during walking in older adults. J Biomech 41: 1520–1527, 2008.
47. Slemenda C, Cummings S, Seeman E, Lips P, Black D, Karpf DB. Prevention of hip fractures: Risk factor modification. Am J Med 103: 65S–73S, 1997.
48. Smith LD. Hip fractures; the role of muscle contraction or intrinsic forces in the causation of fractures of the femoral neck. J Bone Joint Surg Am 35: 367–383, 1953.
49. Stalenhoef PA, Diederiks JP, Knottnerus JA, Kester AD, Crebolder HF. A risk model for the prediction of recurrent falls in community-dwelling elderly: A prospective cohort study. J Clin Epidemiol 55: 1088–1094, 2002.
50. Taylor BC, Schreiner PJ, Stone KL, Fink HA, Cummings SR, Nevitt MC, Bowman PJ, Ensrud KE. Long-term prediction of incident hip fracture risk in elderly white women: Study of osteoporotic fractures. J Am Geriatr Soc 52: 1479–1486, 2004.
51. Toulotte C, Thevenon A, Watelain E, Fabre C. Identification of healthy elderly fallers and non-fallers by gait analysis under dual-task conditions. Clin Rehabil 20: 269–276, 2006.
52. Wagner EH, LaCroix AZ, Buchner DM, Larson EB. Effects of physical activity on health status in older adults. I: Observational studies. Annu Rev Public Health 13: 451–468, 1992.
53. Watelain E, Barbier F, Allard P, Thevenon A, Angue JC. Gait pattern classification of healthy elderly men based on biomechanical data. Arch Phys Med Rehabil 81: 579–586, 2000.
54. Winter DA. The Biomechanics of Motor Control of Human Gait: Normal, Elderly and Pathological. Waterloo, Canada: University of Waterloo Press, 1991.
55. Winter DA, Patla AE, Frank JS, Walt SE. Biomechanical walking pattern changes in the fit and healthy elderly. Phys Ther 70: 340–347, 1990.
Keywords:

aging; biodynamics; exercise; walk; postural control

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