- Email: [email protected]
Gait characteristics as a function of age and gender
Gait characteristics gender
as a function of age and
B M Nigg, V Fisher, J L Ronsky
Human
Performance
Laboratory,
The University
of Calgary,
Alberta,
Canada
Summary Sixty male and fifty-eight female subjects ranging in age from 20 to 79 years performed walking at a controlled pace barefoot, wearing standard shoes, and wearing their personal shoes. Additionally these subjects performed walking in the standard shoe at a freely selected speed. Selected kinematic variables for the knee and ankle joint complexes and ground reaction forces were measured in three dimensions to determine differences with respect to age and gender. Additionally a comparison of the path of motion during ground contact and the active range of motion measured in a range of motion fixture were made. A multivariate analysis revealed a number of the kinematic and kinetic variables which were significantly different although the absolute differences were generally small. The comparison of path of motion and range of motion revealed a high correlation for abduction and adduction and plantarflexion and dorsiflexion. It is speculated that changes in gait pattern with increasing age are associated with decreasing muscle strength and a need for increased stability during locomotion with increasing age. The high correlation between path of motion and range of motion is associated with the decrease in muscle strength with increasing age, which is assumed to influence both path of motion and range of motion. Key words:
Gait, ageing,
Gait & Posture
Definition
gender,
strength
1994: Vol. 2: 213-220,
December
of terms
Range of motion (ROM): Maximal values of movement of one segment relative to another segment. Comment: In this paper the expression ROM is used for the ankle joint complex and for the knee joint. For the ankle joint complex the ROM indicates the rotational movement of the foot relative to the leg, specifically plantarflexion and dorsiflexion, abduction and adduction, and inversion and eversion. For the knee joint the ROM is determined for flexion-extension. Active ROM: ROM achieved by actively moving one segment with respect to the other segment, using muscle strength.
Passive ROM: ROM achieved by applying well-defined external moments to one segment. Path of motion (PoM): Actual range of values of rotational movement of one segment relative to another segment. Comment: PoM measurements use variables similar to ROM measurements. The PoM for one specific rotational variable is defined as the difference between its maximal and its minimal value. e^,:Unit vector in direction of the i axis
Introduction Rec~ziwi: 16 April 1993 .~ceepred: 4 May 1994 Correspondence und reprint requests to: Benno M. Nigg, Human Performance Laboratory. The University of Calgary. 2500 University Dr. N.W. Calgary, Alberta. Canada T?N lN4
0 1994 3utterworth-Heinemann 0966-6362-94-040213-08
Ltd
As the mean age of the population continues to increase, more research efforts are being devoted to determining changes with age and ways in which any changes seen as being detrimental can be minimized. One increasing area of study has been to investigate changes in gait, since maintaining independent mobility is important to the ageing individual. A common
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Gait & Posture 1994; 2: No 4
observation is that there is a decrease in walking speed with age I4 , due to a shorter step length rather than reduced cadence4. An increase in stance time has also been found’,?.4, and along with the decreased stride length has been suggested as a strategy used by the elderly population to maintain stability. A number of variables describing changes in joint kinematics have been found with increasing age. In a study of Japanese women a significant decrease in lower limb joint displacements were found caused in particular by decreased joint angles at toe-off?. Additionally a decrease in the ankle ROM for elderly women compared to younger groups was found5. Furthermore increasing age was associated with an increase in foot abduction], a decrease in ankle extension at the end of the stance phase’, a decrease in peak heel rise’, a more plantigrade landing4, and a decrease in push-off power4. In a recent study, a decrease in maximal active ankle ROM was reported with increasing age6. It would be of interest to determine whether the reductions in the PoM with age reported earlier in gait studies is associated with the decrease in active ROM and/or stability considerations. Previous studies analysing gait characteristics have typically used either male or female subjects. Few studies have examined gender differences. Significant differences between males and females have been reported in an ankle ROM study6, and since this range may influence gait it was suggested that future studies should determine whether gender effects occur. Studies investigating gait characteristics have also in general required subjects to walk at their own pace. Inter-individual differences in walking speed and related segment velocities may, however, influence the kinematic variables measured’. Because of this, a constant walking speed across subjects may be advantageous. The purposes of this paper were (1) to investigate changes in gait characteristics with age for both genders, through kinematic and kinetic analyses, when a constant speed was maintained by all subjects, and (2) to compare the path of motion during walking with the ROM measured with an active ROM assessment.
Methods Subjects
One hundred and twenty healthy subjects (60 male, 60 female) volunteered and gave informed consent to participate in the study. These subjects met the criteria for inclusion in the study which were: participation in some type of physical activity at least once a week, no artificial joints, no walking aids, current physical condition to be pain free, and previous major injuries not to influence gait and/or flexibility. Based on their age the subjects were grouped into four categories: 20-39 years, 40-59 years, 60-69 years and 70-79 years. Mean data and standard deviations for age, height and body mass are summarized in Table 1. Some trials were deleted because of hidden or merging markers and therefore the final number of subjects was 118 (60 male, 58 female). Kinematic and kinetic measurements
Three-dimensional (3D) kinematic measurements of the left thigh, leg, and foot were collected with a 3D motion analysis system (Motion Analysis Corp., Santa Rosa, CA. (MAC)) consisting of a VP3 10 videoprocessor, four NAC high-speed videocameras operating simultaneously at a frequency of 100 Hz, and a SUN 31280 computer for storage of raw data. The spatial movement of each of the lower limb segments was determined from the position of reflective spherical markers, 10 mm in diameter, which were securely fixed to specific landmarks as shown in Figure 1. A description of the landmarks can be found in the Appendix. The markers were mounted with adhesive tape directly to the skin surface and to the exterior shoe surface (immediately superior to the sole for markers H and I) in the standard and personal shoe conditions. The test movement was walking over a force platform mounted in the centre of a 25-m walkway. The subjects performed the tests in four conditions, differing in walking speed and footwear: (1) controlled speed, barefoot, (2) controlled speed, standard shoe, (3) controlled speed, personal shoe, and (4) freely selected speed, standard shoe. The walking speed was controlled at 1.25 m s-i (? 0.3 m s-i) using two infrared photocells mounted
Table 1. Mean and (SD) for age, height (HI, weight, and number of subjects for each age and gender group Age group
20-39 40-59 60-69 70-79
Male age
Fern age
Male
Fern
Male mass
Fern mass
(years)
(years)
(n)
(n)
(kg)
(kg)
26.1 (4.5) 50.9 (5.9) 63.5 (2.1) 73.4 (3.0)
28.2 (5.9) 48.8
77.0 (5.8) 80.0
61.8 (6.4) 66.6 (10.0) 63.0 (8.1) 62.5 (9.6)
14
15
15
15
15
14
16
14
(6.0) 64.9 (2.9) 73.6 (4.6)
(6.9) 79.6 (I 1.5) 76.7 (8.9)
Male
Fern
CcHm)
ccH,I
182.4 (9.5) 177.7 (6.3) 176.5 (4.3) 169.9 (5.8)
165.9 (4.1) 166.3 (4.1) 161.5 (5.8) 159.4 (5.3)
Nigg et al.: Gait as a function
Figure 1. Location of the markers used for the kinematic analysis.
1.5 m apart and 1 m above the force platform. The standard shoes were running shoes (Adidas, Detroit) in different sizes which were worn without socks to provide a snug fit of the foot in the shoe. Condition (4) was always performed at the beginning of the testing session to avoid an influence of the controlled speed on the freely selected walking speed. In each condition the subjects completed at least five practice trials and when they felt comfortable the data for one successful trial with the left foot was collected. The positiontime trajectories of the markers with respect to the inertial reference frame (LCS) were calculated from the video data with a direct linear transformation (DLT) method8. The resulting movement trajectories were smoothed using a 4th-order bidirectional low-pass filter with zero time lag and with a cutoff frequency of 25 Hz. A joint-fixed coordinate system for each limb segment (SCS) was derived using a set of three orthogonal joint axes, based on a coordinate transformation of the landmark marker locations. The spatial data for the coordinate transformation was obtained based on a standard neutral position for all subjects to allow for intersubject comparison. This position was defined as that in which the greater trochanter was 5 cm anterior to the lateral calcaneus, and was comparable with normal standing. For the kinematic analysis the three dimensional joint attitude and movement of the lower leg and foot were defined using a joint coordinate system (JCS)9. Four sets of JCS angles were defined as follows: position of the foot with respect to the inertial reference frame (LAB/FOOT), relative position of the foot with respect
of age and gender
2 15
to the leg (LEG/FOOT), relative position of the leg with respect to the foot (FOOT/LEG). and relative position of the leg with respect to the thigh (THIGH/LEG). Movement of the foot within the shoe during walking was assumed to be small in comparison to the shoe movement. Therefore, with the exception of the barefoot condition the term ‘foot’ refers to the foot segment defined by markers attached to the shoe. All coordinate system axes were chosen such that the sequence of rotations was flexion-extension. abductionadduction. and inversion-eversion. For the ankle joint the flexion-extension and inversion-eversion components of movement were described with the LEG/FOOT coordinate system (Figure 2). The tibia1 rotation movement component at the ankle joint. indicated by the axial rotation of the leg with respect to the foot. was quantified using the FOOT/LEG coordinate system. In this case the JCS axis ej was the longitudinal axis of the lower leg. Analysis of movement at the knee joint was limited to the flexion-extension component using the THIGH/LEG coordinate system. The remaining knee joint movement components contained substantial errors due to skin marker movement and are not presented. The average repeatability for calculated JCS angles was determined in a pilot study and was estimated to be +2.3” and was primarily attributed to marker movement artefacts. In order to provide results in terms of the LCS an adjustment factor was applied for plantarflexiondorsiflexion, inversioneversion, and abduction-adduction for the LAB-FOOT system. The variables used to define the position components in the various coordinate systems are defined as follows:
Figure 2. JCS with 6, defined as the mediolateral (2) axis of the leg coordinate system and 9, defined as the anteroposterior (Xl axis of the foot coordinate system.
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Gait & Posture 1994; 2: No 4
LAB/FOOT
coordinate system
Ab-adduction angle of the foot with respect to a line parallel to the walking direction, determined as a rotation about an inferior-superior axis (C,) through the foot. Foot adduction is positive, abduction is negative. Inversion-eversion angle of the foot with respect to the ground, determined as a rotation of the foot about the longitudinal axis (C,) of the foot. Foot eversion is positive, ankle joint inversion is negative.
Comparison of PoA4 and ROM results Active ROM measurements were performed for the same subject pool using a 6 degree of freedom ROM machine that was developed for in-vivo measurements of ankle joint complex ROM and has been described earlier6. These data from these ROM measurements were used to compare with the actual path of motion, PoM, results during walking. Statistical analyses
LEG/FOOT
coordinate system
Plantar- dorstflexion angle between the leg and the foot, determined as a rotation about the mediolateral axis (C,) of the leg. Dorsiflexion is positive, plantarilexion is negative. Ankle joint inversion-eversion angle of the ankle joint complex, determined as a rotation of the foot with respect to the leg, about the longitudinal axis (8,) of the foot. Ankle joint eversion is positive, inversion is negative.
The data was analysed multivariately to determine age and gender effects across shoe conditions for each of the kinematic variables examined in the labfoot, leg-foot and thigh-leg coordinate systems as well as the kinetic variables. Post-hoc tests were performed to determine where differences among the shoes occurred. A univariate analysis was completed to determine differences between the control and free speed conditions. The level of significance was set to P = 0.01. Results
FOOT/LEG
coordinate system
Rotation of the leg angle with respect to the foot about the longitudinal axis (C,) of the leg. External leg rotation is positive, internal leg rotation is negative. THIGH/LEG
coordinate system
kYneeJlexion/extension angle between the thigh and the lower leg, determined as a rotation of the leg about the mediolateral axis (e,) of the thigh. Knee extension is positive, flexion is negative. In addition to these variables, knee flexion and ankle joint PoMs were determined. Three-dimensional ground reaction forces were measured using a Kistler force platform, sampling at 1000 Hz, which was synchronized with the video system used to determine the kinematic measures. The errors in the force measurements are less than + 3% for each force component. The three components of the total ground reaction force were defined as follows: Vertical force component, defined as the component of the ground reaction force in the vertical direction (positive in the upward direction), Mediolateral force component, defined as the component of the ground reaction force in the mediolateral direction (positive in the medial direction), and Anterior-posterior force component, defined as the component of the ground reaction force in the anterior-posterior direction (positive in the anterior direction). The time variables were normalized to percentage of stance. The specific variables analysed included the local maxima and minima of the force-time curves for the three force components. Definitions of the kinetic variables analysed are included in Appendix B.
Mean results and standard deviation for selected kinematic variables are illustrated in Figure 3. Speed and foo twear The average control speed was 1.25 m s-l while the mean freely selected speed was 1.49 m s-i. Significant differences between speed conditions were found, independent of age and gender, for five kinematic and seven kinetic variables. However, the differences were small and were not considered relevant. Therefore speed differences will not be considered further in this paper and the results are discussed for the controlled walking speed condition. Significant differences between footwear conditions were found, independent of age and gender, for the kinematic and kinetic variables. Posthoc tests showed that the differences between standard and personal shoes were minimal (< 1.4 degrees for the kinematic variables and < 1.3 % of body weight for the kinetic variables). Differences between both shoe conditions and the barefoot condition were larger (up to 7.8 degrees for the kinematic variables and up to 2.3% of bodyweight for the kinetic variables). However, there was no interaction across footwear conditions for either age or gender. Therefore differences for age and gender are presented across the two shoe conditions.
Age A main effect of age was found for both the kinematic and kinetic variables across shoes, with no interaction effects due to gender and shoe. The kinematic variables measured across shoes showed the following significant differences with increasing age: an increase in initial shoe eversion of 6.5 degrees, an increase in maximal shoe eversion of 6.1 degrees, a decrease in the ankle
Nigg et al.: Gait as a function
PLANTAR-DORSI FLEXION ANGLE
of age and gender
217
tion of 2.0 degrees, and a smaller knee flexion path of motion of 2.4 degrees, which is associated with a greater initial knee flexion position at heel strike of 2.4 degrees. The kinetic variables measured across shoes showed that females had a smaller peak vertical force during weight acceptance of 3.4% of bodyweiglit, a higher peak vertical force during push-off of 3.0% of bodyweight, and a smaller medial force peak during the initial 50% of ground contact of 0.8% of bodyweight, as compared to males.
Ided
110 100 90 00 ‘10 SHOE IN-EVERSION ANGLE (FOOT-GROUND) Idcgl 0 -5
Comparison of PoM and ROM results
-10
The ROM and PoM results for males and females for selected variables are summarized in Table 2. Plantar-dorsiflexion ROM showed a significant decrease of 11.1 degrees with increasing age. Similarily, plantar-dorsiflexion PoM showed a significant decrease of 4.4 degrees with increasing age. Abduction-adduction ROM showed a significant decrease of 13.6 degrees with increasing age. Similarily, abduction-adduction PoM showed a significant decrease of 4.2 degrees with increasing age. Inversion-eversion ROM showed a significant decrease of 6.7 degrees with increasing age. However, inversioneversion PoM showed no significant change with increasing age.
-15 -20
ANKLE JOINT IN-EVERSION ANGLE tded 20 10 0 -10 -20 LEG ROTATION ANGLE [dcgl 10
t
Discussion
KNEE FLEXION ANGLE tdcgl 40 20
I 0
FIRST
I
SO
NORhfALiZ@DTfhfE 1 100
I%1
LAST CONTAm
Figure 3. Lower limb kinematic variables for typical elderly subject. The time 0 corresponds to heel strike, the time 100 to toe-off.(a) Lab/foot dorsiflexion-plantarflexion; (b) lab/foot eversion-inversion; (c) leg/foot eversion-inversion; (d) foot/leg external-internal rotation; (e) thigh/leg extension-flexion. flexion PoM of 4.4 degrees, an increase of the initial knee angle of 2.8 degrees, and an increase in tibia1 rotation of 2.9 degrees. The kinetic variables measured showed an increase in the vertical force peak during landing of 4.7% of bodyweight, and a decrease in maximal anterior-posterior force at push-off of 1.8% of bodyweight. Gender
Across shoes, females were found to have a smaller initial shoe eversion of 1.1 degrees, a smaller tibia1 rota-
Changes in gait pattern as a function of age may be interpreted as a result of changes in muscular strength. Decrements in dorsiflexor and plantarflexor muscle strength were found to occur in healthy males and females starting at about age 50 years12.13. Significant decreases in both the maximum isometric and isokinetic torques were reported that could be generated by the knee extensors14. Reduced walking speed in the elderly has been associated among other factors with a decrease in calf strength l5. Changes in gait pattern as a function of age may also be interpreted as a result of changes in motor control as a function of age. Reduced stability, for instance, may be associated with motor unit changes that occur with increasing age. Losses of motor units were found with increasing age, with large reductions after age 6016. Fast twitch muscle fibres decrease with age while the motor units of the slow twitch fibres reinnervate some neighbouring fibres13.i6.17.Related to this is an increase in time to peak tension and time to relaxation13. As a result the muscle will not be able to create force as quickly during motions requiring a fast response, such as recovering from a trip or slip. Therefore movements that challenge the elderly with respect to time are likely to show differences when compared with young adults. Performance in cognitive tasks has also been related to time constraints. Although it is generally thought that cognitive functioning decreases with age, it has been shown’* that if test length is reduced and time is
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1994; 2: No 4
Table 2. Mean and (SD) of ROM and PoM results for males and females for selected variables using the laboratory shoe for ROM and PoM with n(20-39) = 29 (14 male and 15 female), n(40-59) = 30 (15 male and 15 female, n(60-69) = 29 (15 male and 14 female, and for n(70-79) = 30 (16 male and 14 female). PD = plantar- dorsiflexion, IE = in- eversion, AA = ab- adduction Var
Age
ROM All (years)
ROM Male (years)
ROM Fern (years)
PoM All (deg)
PoM Male (deg)
PoM Fern (de@
PD
20-39
70.7 (12.9) 65.7 (10.1) 62.1 (6.0) 59.6 (8.6)
66.8 (15.6) 67.0 (8.3) 61.6 (6.1) 60.1 (9.0)
74.2 (8.9) 64.3 (11.7) 62.7 (6.1) 59.1 (8.3)
29.9 (3.9) 28.2 (4.1) 27.0 (4.2) 25.5 (3.7)
28.8 (3.7) 28.2 (3.3) 26.4 (3.5) 25.0 (3.1)
31.2 (4.0) 27.5 (4.5) 27.0 (3.8) 25.4 (3.9)
35.4 (9.1) 34.5 (10.0) 29.6 (6.6) 28.7 (7.1)
32.0 (5.9) 35.1 (10.1) 32.0 (6.1) 30.0 (6.2)
38.6 (10.4) 33.8 (10.1) 27.1 (6.5) 27.2 (7.9)
16.2 (4.3) 16.2 (3.9) 16.4 (4.6) 16.7 (3.9)
17.0 (5.0) 15.8 (3.8) 15.7 (5.3) 16.8 (4.4)
14.4 (3.0) 15.6 (4.5) 17.3 (5.4) 16.6 (3.6)
72.0 (16.1) 63.2 (12.1) 59.8 (9.8) 58.4 (11.3)
67.7 (16.0) 64.7 (10.3) 61.4 (6.9) 57.4 (9.0)
76.0 (15.7) 61.6 (13.8) 58.1 (12.3) 59.5 (13.7)
15.4 (5.5) 14.4 (4.1) 12.7 (5.0) 11.2 (4.6)
15.3 (2.9) 13.5 (4.4) 11.1 (3.5) 10.0 (3.2)
15.6 (6.6) 14.8 (3.4) 13.8 (6.0) 13.5 (4.4)
40-59 60-69 70-79
IE
20-39 40-59 60-69 70-79
AA
20-39 40-59 60-69 70-79
increased, the elderly are able to perform as well in cognitive tests of fluid intelligence (problem solving in tasks dealing with complex relations and novel materialsi9) as young adults. The results found in this study are discussed with these two major aspects, reduction of muscle strength and change in motor control as a function of age, in mind. Obviously the set-up of the experiment does not allow conclusive interpretation. However, some indications for one or the other results may be appropriate. The differences for significant variables were between 3.2 and 6.5 degrees, generally considered a small difference in gait analysis. The reduction of the PoM for the ankle joint with increasing age corresponds to a stiffening of the movement. A similar trend can be seen in the knee joint (Figure 4). The reduction of PoM may be associated with the shortening of the stride length, which has been reported earlierG4, and is thought to be a strategy to maintain stability. The results for the movement in the ankle joint complex showed a somewhat contradictory behaviour with respect to movement stability. The plantar- dorsiflexion PoM decreased with increasing age, which was expected and is interpreted as a strategy to increase stability. Additionally the foot ab- adduction decreased with increasing age, which again may be interpreted as a strategy to increase stability. However, the third rotational movement of the ankle joint complex, shoe eversion, showed an increase with increasing age which
cannot be interpreted as a strategy to increase stability. It may be a result of an increased eversion moment due to a slightly more abducted position of the foot for the older subject groups and/or a result of an increased laxity of the plantar ligaments supporting the arch of the foot which occurs with age”. The tendency to become more flatfooted with age usually results in an increase in abduction as well as eversion”. The maximum absolute differences for significant variables in the kinetic analysis were small and within the sensitivity of the force plate. They are not considered relevant and will not be discussed further.
ANKLEPGM We21
+
KNEEPGM
+ Idrol
Figure 4. Change of the PoM for the ankle and knee joint as a function of age for male and female subjects together (mean and standard error)
Nigg et al.: Gait as a function of age and gender Gender
The statistical analysis showed significant differences between males and females for some of the kinematic and kinetic variables; however, the absolute differences were quite small and are not considered functionally relevant. They will not be discussed further. Comparison of PoM and ROM results
PoMs for plantardorsiflexion. foot in-eversion. and foot ab- adduction from the present study were compared with corresponding active ROM measurement& as summarized in Table 2. No relationship between the PoM and the ROM results could be found for foot ineversion, but consistent results were found for the relationship between the PoM and the active ROM for foot plantardorsiflexion and abadduction. As the ROM of plantardorsiflexion decreases with increasing age there was a corresponding decrease in the PoM found during gait (Figure 5 top). A similar result was found for ab adduction (Figure 5 bottom). This relationship indicates that similar mechanisms may be acting to influence ROM and PoM. One may speculate that the major influence is muscle strength, which decreases with increasing age and affects similarly ROM and PoM.
219
and it is speculated that the measured differences would be more pronounced for inactive test subjects. Second, the differences discussed in this paper were consistent throughout all footwear conditions. which suggests that the results are a pattern rather than a pure coincidence. The differences found across age and gender could consistently be explained with decreasing strength and the attempt to increase stability during locomotion with increasing age. There was no evidence that aspects of motor control would play a major role for the selected movement of walking. However, it is speculated that the findings may be different for movement tasks closer to the limits of the test subjects. The correlation between PoM and ROM for plantar dorsiflexion and ab-adduction suggests that strength training for the ankle (and possibly knee) complex may change the gait characteristics for the elderly and provide an improved (subjective or objective) feeling of stability, since all the changes in movement seem to point toward effects of a decrease in strength. Acknowledgements This research was supported by a grant from Fitness and Lifestyle Canada and by Adidas. The authors would like to thank Margo Fraser for her help in data analysis and editing.
General discussion
The differences found as a function of age were rather small and one may debate their relevance. There are at least two facts that suggest in the view of the authors that some of these differences are relevant. First, the subjects included in the study were all physically active POM
WI
PLANTAR-DORSIFLEXION
3+---t-I
I
26 26 ROM
__
POM IAS-ADDUCTION
16 14
I
-+ I
female
+
male
12
Figure 5. Relationship between the PoM and the ROM for dorsiflexion-plantarflexion (top) and abduction-adduction (bottom) for male and female subject groups.
Appendix Description of marker locations
A. Greater trochanter: lateral on the thigh on a line between the greater trochanter and the lateral femoral epicondyle, in as close proximity to the greater trochanter as possible. B. Mid-anterior femur: anteriorly in the mid-sagittal plane of the thigh between spheres A and C. C. Lateral epicondyle: on the lateral epicondyle of the femur. D. Tibia1 tuberosity: on the tibia1 tuberosity in the mid-sagittal plane of the lower leg. E. Posterior lateral mid-tibia: posterolateral on the lower leg, between spheres D and F. F. Anterior lateral lower tibia: anterolateral on the calf, approximately 10 cm proximal to the lateral malleolus. G.. Superior navicular: in the mid-sagittal plane of the foot, approximately halfway between the toe and the heel, in a straight line with markers B and D. H. Lateral calcaneus: lateral on the foot in approximate alignment with the extrapolation of a line from the lateral epicondyle-lateral malleolus, and in a straight line with markers A and C.
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I.
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Head of fifth metatarsal: on the head of the fifth metatarsal, articulation with the fifth phalanx.
just prior to the
References Murray MP, Kory RC, Clarkson BH. Walking patterns in healthy old men. J Gerontol 1969; 24: 169-78 Kaneko M, Morimoto Y, Kimura M et al. A kinematic analysis of walking and physical fitness in elderly women. Can J Sport Sci 1991; 16(3): 223-8
Himann JE, Cunningham DA, Rechnitzer PA, Paterson DH. Age related changes in speed of walking. Med Sci Sports Exert 1988; 20(2): 161-6
Winter DA, Patla AE, Frank JS, Walt walking pattern changes in the fit and Phys Ther 1990; 70(6): 340-7 Hageman PA, Blanke DJ. Comparison women and elderly women. Phrs Ther
SE: Biomechanical healthy elderly. of gait of young 1986; 66(9):
1382-7
Nigg BM, Fisher V, Allinger TL et al. Range of motion of the foot as a function of age. Foot Ankle 1992; 13(6): 336-43
Nigg BM Biomechanics of Running Shoes. Champaign, IL, Human Kinetics, 1986; 59-60 Abdel-Aziz YI, Karara HM. Direct linear transformation from comparator coordinates into object-space coordinates. In: Proceedings ASP/W Symposium on Close-Range Photogrammetry. American Society of Photogrammetry, Falls Church, VA., 1971; 1-18 Grood ES, Suntay WJ. A joint coordinate system for the clinical description of three-dimensional motions:
application to the knee. J Biomech Eng 1983; 105: 136-44 10 Nigg BM, Skleryk BN. Gait Characteristics of the elderly. Clin Biomech 1988; 3: 79-87 11 Moore KL. Clinically Oriented Anatomy. Williams and Wilkins, Baltimore, USA., 1992; 495-6 12 Vandervoort AA, McComas AJ. Contractile changes in opposing muscles of the human ankle joint with aging. J Appl Physiol 1986; 61(l): 361-7 13 Vandervoort AA Chesworth BM, Cunningham DA et al. Age and sex effects on mobility of the human ankle. J Gerontol 1992; 47(l): M17-21 14 Murray MP, Gardner GM, Mollinger LA, Sepic SB. Strength of isometric contractions. Knee muscles of men aged 20 to 86. Phys Ther 1980; 60: 412-19 15 Bendall MJ, Bassey EJ, Pearson MB. Factors affecting walking speed of elderly people. Age Aging 1989; 18: 327-32
16 Brown WF, Strong MJ, Snow, R. Methods for estimating numbers of motor units in biceps-brachialis muscles and losses of motor units with aging. Muscle Nerve 1988; 11: 423-32 . 17 Kanda K, Hashizume K. Changes in properties of the medial gastrocnemius motor units in aging rats. J Neurophysiol 1989; 61(4): 73746 18 Baltes PB, Kliegl R, Dittmann-Kohli F. On the locus of training gains in research on the plasticity of fluid intelligence in old age. J Educ Psychof 1988; 80(3): 392-400
19 Baltes PB, Willis SL. Plasticity and enhancement of intellectual functioning in old age: Penn State’s adult development and enrichment project (ADEPT). In: Craik FJM, Trehub SE, eds. Aging and Cognitive Processes. Plenum Press, New York, 1982; 353-89
as a function of age and
B M Nigg, V Fisher, J L Ronsky
Human
Performance
Laboratory,
The University
of Calgary,
Alberta,
Canada
Summary Sixty male and fifty-eight female subjects ranging in age from 20 to 79 years performed walking at a controlled pace barefoot, wearing standard shoes, and wearing their personal shoes. Additionally these subjects performed walking in the standard shoe at a freely selected speed. Selected kinematic variables for the knee and ankle joint complexes and ground reaction forces were measured in three dimensions to determine differences with respect to age and gender. Additionally a comparison of the path of motion during ground contact and the active range of motion measured in a range of motion fixture were made. A multivariate analysis revealed a number of the kinematic and kinetic variables which were significantly different although the absolute differences were generally small. The comparison of path of motion and range of motion revealed a high correlation for abduction and adduction and plantarflexion and dorsiflexion. It is speculated that changes in gait pattern with increasing age are associated with decreasing muscle strength and a need for increased stability during locomotion with increasing age. The high correlation between path of motion and range of motion is associated with the decrease in muscle strength with increasing age, which is assumed to influence both path of motion and range of motion. Key words:
Gait, ageing,
Gait & Posture
Definition
gender,
strength
1994: Vol. 2: 213-220,
December
of terms
Range of motion (ROM): Maximal values of movement of one segment relative to another segment. Comment: In this paper the expression ROM is used for the ankle joint complex and for the knee joint. For the ankle joint complex the ROM indicates the rotational movement of the foot relative to the leg, specifically plantarflexion and dorsiflexion, abduction and adduction, and inversion and eversion. For the knee joint the ROM is determined for flexion-extension. Active ROM: ROM achieved by actively moving one segment with respect to the other segment, using muscle strength.
Passive ROM: ROM achieved by applying well-defined external moments to one segment. Path of motion (PoM): Actual range of values of rotational movement of one segment relative to another segment. Comment: PoM measurements use variables similar to ROM measurements. The PoM for one specific rotational variable is defined as the difference between its maximal and its minimal value. e^,:Unit vector in direction of the i axis
Introduction Rec~ziwi: 16 April 1993 .~ceepred: 4 May 1994 Correspondence und reprint requests to: Benno M. Nigg, Human Performance Laboratory. The University of Calgary. 2500 University Dr. N.W. Calgary, Alberta. Canada T?N lN4
0 1994 3utterworth-Heinemann 0966-6362-94-040213-08
Ltd
As the mean age of the population continues to increase, more research efforts are being devoted to determining changes with age and ways in which any changes seen as being detrimental can be minimized. One increasing area of study has been to investigate changes in gait, since maintaining independent mobility is important to the ageing individual. A common
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observation is that there is a decrease in walking speed with age I4 , due to a shorter step length rather than reduced cadence4. An increase in stance time has also been found’,?.4, and along with the decreased stride length has been suggested as a strategy used by the elderly population to maintain stability. A number of variables describing changes in joint kinematics have been found with increasing age. In a study of Japanese women a significant decrease in lower limb joint displacements were found caused in particular by decreased joint angles at toe-off?. Additionally a decrease in the ankle ROM for elderly women compared to younger groups was found5. Furthermore increasing age was associated with an increase in foot abduction], a decrease in ankle extension at the end of the stance phase’, a decrease in peak heel rise’, a more plantigrade landing4, and a decrease in push-off power4. In a recent study, a decrease in maximal active ankle ROM was reported with increasing age6. It would be of interest to determine whether the reductions in the PoM with age reported earlier in gait studies is associated with the decrease in active ROM and/or stability considerations. Previous studies analysing gait characteristics have typically used either male or female subjects. Few studies have examined gender differences. Significant differences between males and females have been reported in an ankle ROM study6, and since this range may influence gait it was suggested that future studies should determine whether gender effects occur. Studies investigating gait characteristics have also in general required subjects to walk at their own pace. Inter-individual differences in walking speed and related segment velocities may, however, influence the kinematic variables measured’. Because of this, a constant walking speed across subjects may be advantageous. The purposes of this paper were (1) to investigate changes in gait characteristics with age for both genders, through kinematic and kinetic analyses, when a constant speed was maintained by all subjects, and (2) to compare the path of motion during walking with the ROM measured with an active ROM assessment.
Methods Subjects
One hundred and twenty healthy subjects (60 male, 60 female) volunteered and gave informed consent to participate in the study. These subjects met the criteria for inclusion in the study which were: participation in some type of physical activity at least once a week, no artificial joints, no walking aids, current physical condition to be pain free, and previous major injuries not to influence gait and/or flexibility. Based on their age the subjects were grouped into four categories: 20-39 years, 40-59 years, 60-69 years and 70-79 years. Mean data and standard deviations for age, height and body mass are summarized in Table 1. Some trials were deleted because of hidden or merging markers and therefore the final number of subjects was 118 (60 male, 58 female). Kinematic and kinetic measurements
Three-dimensional (3D) kinematic measurements of the left thigh, leg, and foot were collected with a 3D motion analysis system (Motion Analysis Corp., Santa Rosa, CA. (MAC)) consisting of a VP3 10 videoprocessor, four NAC high-speed videocameras operating simultaneously at a frequency of 100 Hz, and a SUN 31280 computer for storage of raw data. The spatial movement of each of the lower limb segments was determined from the position of reflective spherical markers, 10 mm in diameter, which were securely fixed to specific landmarks as shown in Figure 1. A description of the landmarks can be found in the Appendix. The markers were mounted with adhesive tape directly to the skin surface and to the exterior shoe surface (immediately superior to the sole for markers H and I) in the standard and personal shoe conditions. The test movement was walking over a force platform mounted in the centre of a 25-m walkway. The subjects performed the tests in four conditions, differing in walking speed and footwear: (1) controlled speed, barefoot, (2) controlled speed, standard shoe, (3) controlled speed, personal shoe, and (4) freely selected speed, standard shoe. The walking speed was controlled at 1.25 m s-i (? 0.3 m s-i) using two infrared photocells mounted
Table 1. Mean and (SD) for age, height (HI, weight, and number of subjects for each age and gender group Age group
20-39 40-59 60-69 70-79
Male age
Fern age
Male
Fern
Male mass
Fern mass
(years)
(years)
(n)
(n)
(kg)
(kg)
26.1 (4.5) 50.9 (5.9) 63.5 (2.1) 73.4 (3.0)
28.2 (5.9) 48.8
77.0 (5.8) 80.0
61.8 (6.4) 66.6 (10.0) 63.0 (8.1) 62.5 (9.6)
14
15
15
15
15
14
16
14
(6.0) 64.9 (2.9) 73.6 (4.6)
(6.9) 79.6 (I 1.5) 76.7 (8.9)
Male
Fern
CcHm)
ccH,I
182.4 (9.5) 177.7 (6.3) 176.5 (4.3) 169.9 (5.8)
165.9 (4.1) 166.3 (4.1) 161.5 (5.8) 159.4 (5.3)
Nigg et al.: Gait as a function
Figure 1. Location of the markers used for the kinematic analysis.
1.5 m apart and 1 m above the force platform. The standard shoes were running shoes (Adidas, Detroit) in different sizes which were worn without socks to provide a snug fit of the foot in the shoe. Condition (4) was always performed at the beginning of the testing session to avoid an influence of the controlled speed on the freely selected walking speed. In each condition the subjects completed at least five practice trials and when they felt comfortable the data for one successful trial with the left foot was collected. The positiontime trajectories of the markers with respect to the inertial reference frame (LCS) were calculated from the video data with a direct linear transformation (DLT) method8. The resulting movement trajectories were smoothed using a 4th-order bidirectional low-pass filter with zero time lag and with a cutoff frequency of 25 Hz. A joint-fixed coordinate system for each limb segment (SCS) was derived using a set of three orthogonal joint axes, based on a coordinate transformation of the landmark marker locations. The spatial data for the coordinate transformation was obtained based on a standard neutral position for all subjects to allow for intersubject comparison. This position was defined as that in which the greater trochanter was 5 cm anterior to the lateral calcaneus, and was comparable with normal standing. For the kinematic analysis the three dimensional joint attitude and movement of the lower leg and foot were defined using a joint coordinate system (JCS)9. Four sets of JCS angles were defined as follows: position of the foot with respect to the inertial reference frame (LAB/FOOT), relative position of the foot with respect
of age and gender
2 15
to the leg (LEG/FOOT), relative position of the leg with respect to the foot (FOOT/LEG). and relative position of the leg with respect to the thigh (THIGH/LEG). Movement of the foot within the shoe during walking was assumed to be small in comparison to the shoe movement. Therefore, with the exception of the barefoot condition the term ‘foot’ refers to the foot segment defined by markers attached to the shoe. All coordinate system axes were chosen such that the sequence of rotations was flexion-extension. abductionadduction. and inversion-eversion. For the ankle joint the flexion-extension and inversion-eversion components of movement were described with the LEG/FOOT coordinate system (Figure 2). The tibia1 rotation movement component at the ankle joint. indicated by the axial rotation of the leg with respect to the foot. was quantified using the FOOT/LEG coordinate system. In this case the JCS axis ej was the longitudinal axis of the lower leg. Analysis of movement at the knee joint was limited to the flexion-extension component using the THIGH/LEG coordinate system. The remaining knee joint movement components contained substantial errors due to skin marker movement and are not presented. The average repeatability for calculated JCS angles was determined in a pilot study and was estimated to be +2.3” and was primarily attributed to marker movement artefacts. In order to provide results in terms of the LCS an adjustment factor was applied for plantarflexiondorsiflexion, inversioneversion, and abduction-adduction for the LAB-FOOT system. The variables used to define the position components in the various coordinate systems are defined as follows:
Figure 2. JCS with 6, defined as the mediolateral (2) axis of the leg coordinate system and 9, defined as the anteroposterior (Xl axis of the foot coordinate system.
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Gait & Posture 1994; 2: No 4
LAB/FOOT
coordinate system
Ab-adduction angle of the foot with respect to a line parallel to the walking direction, determined as a rotation about an inferior-superior axis (C,) through the foot. Foot adduction is positive, abduction is negative. Inversion-eversion angle of the foot with respect to the ground, determined as a rotation of the foot about the longitudinal axis (C,) of the foot. Foot eversion is positive, ankle joint inversion is negative.
Comparison of PoA4 and ROM results Active ROM measurements were performed for the same subject pool using a 6 degree of freedom ROM machine that was developed for in-vivo measurements of ankle joint complex ROM and has been described earlier6. These data from these ROM measurements were used to compare with the actual path of motion, PoM, results during walking. Statistical analyses
LEG/FOOT
coordinate system
Plantar- dorstflexion angle between the leg and the foot, determined as a rotation about the mediolateral axis (C,) of the leg. Dorsiflexion is positive, plantarilexion is negative. Ankle joint inversion-eversion angle of the ankle joint complex, determined as a rotation of the foot with respect to the leg, about the longitudinal axis (8,) of the foot. Ankle joint eversion is positive, inversion is negative.
The data was analysed multivariately to determine age and gender effects across shoe conditions for each of the kinematic variables examined in the labfoot, leg-foot and thigh-leg coordinate systems as well as the kinetic variables. Post-hoc tests were performed to determine where differences among the shoes occurred. A univariate analysis was completed to determine differences between the control and free speed conditions. The level of significance was set to P = 0.01. Results
FOOT/LEG
coordinate system
Rotation of the leg angle with respect to the foot about the longitudinal axis (C,) of the leg. External leg rotation is positive, internal leg rotation is negative. THIGH/LEG
coordinate system
kYneeJlexion/extension angle between the thigh and the lower leg, determined as a rotation of the leg about the mediolateral axis (e,) of the thigh. Knee extension is positive, flexion is negative. In addition to these variables, knee flexion and ankle joint PoMs were determined. Three-dimensional ground reaction forces were measured using a Kistler force platform, sampling at 1000 Hz, which was synchronized with the video system used to determine the kinematic measures. The errors in the force measurements are less than + 3% for each force component. The three components of the total ground reaction force were defined as follows: Vertical force component, defined as the component of the ground reaction force in the vertical direction (positive in the upward direction), Mediolateral force component, defined as the component of the ground reaction force in the mediolateral direction (positive in the medial direction), and Anterior-posterior force component, defined as the component of the ground reaction force in the anterior-posterior direction (positive in the anterior direction). The time variables were normalized to percentage of stance. The specific variables analysed included the local maxima and minima of the force-time curves for the three force components. Definitions of the kinetic variables analysed are included in Appendix B.
Mean results and standard deviation for selected kinematic variables are illustrated in Figure 3. Speed and foo twear The average control speed was 1.25 m s-l while the mean freely selected speed was 1.49 m s-i. Significant differences between speed conditions were found, independent of age and gender, for five kinematic and seven kinetic variables. However, the differences were small and were not considered relevant. Therefore speed differences will not be considered further in this paper and the results are discussed for the controlled walking speed condition. Significant differences between footwear conditions were found, independent of age and gender, for the kinematic and kinetic variables. Posthoc tests showed that the differences between standard and personal shoes were minimal (< 1.4 degrees for the kinematic variables and < 1.3 % of body weight for the kinetic variables). Differences between both shoe conditions and the barefoot condition were larger (up to 7.8 degrees for the kinematic variables and up to 2.3% of bodyweight for the kinetic variables). However, there was no interaction across footwear conditions for either age or gender. Therefore differences for age and gender are presented across the two shoe conditions.
Age A main effect of age was found for both the kinematic and kinetic variables across shoes, with no interaction effects due to gender and shoe. The kinematic variables measured across shoes showed the following significant differences with increasing age: an increase in initial shoe eversion of 6.5 degrees, an increase in maximal shoe eversion of 6.1 degrees, a decrease in the ankle
Nigg et al.: Gait as a function
PLANTAR-DORSI FLEXION ANGLE
of age and gender
217
tion of 2.0 degrees, and a smaller knee flexion path of motion of 2.4 degrees, which is associated with a greater initial knee flexion position at heel strike of 2.4 degrees. The kinetic variables measured across shoes showed that females had a smaller peak vertical force during weight acceptance of 3.4% of bodyweiglit, a higher peak vertical force during push-off of 3.0% of bodyweight, and a smaller medial force peak during the initial 50% of ground contact of 0.8% of bodyweight, as compared to males.
Ided
110 100 90 00 ‘10 SHOE IN-EVERSION ANGLE (FOOT-GROUND) Idcgl 0 -5
Comparison of PoM and ROM results
-10
The ROM and PoM results for males and females for selected variables are summarized in Table 2. Plantar-dorsiflexion ROM showed a significant decrease of 11.1 degrees with increasing age. Similarily, plantar-dorsiflexion PoM showed a significant decrease of 4.4 degrees with increasing age. Abduction-adduction ROM showed a significant decrease of 13.6 degrees with increasing age. Similarily, abduction-adduction PoM showed a significant decrease of 4.2 degrees with increasing age. Inversion-eversion ROM showed a significant decrease of 6.7 degrees with increasing age. However, inversioneversion PoM showed no significant change with increasing age.
-15 -20
ANKLE JOINT IN-EVERSION ANGLE tded 20 10 0 -10 -20 LEG ROTATION ANGLE [dcgl 10
t
Discussion
KNEE FLEXION ANGLE tdcgl 40 20
I 0
FIRST
I
SO
NORhfALiZ@DTfhfE 1 100
I%1
LAST CONTAm
Figure 3. Lower limb kinematic variables for typical elderly subject. The time 0 corresponds to heel strike, the time 100 to toe-off.(a) Lab/foot dorsiflexion-plantarflexion; (b) lab/foot eversion-inversion; (c) leg/foot eversion-inversion; (d) foot/leg external-internal rotation; (e) thigh/leg extension-flexion. flexion PoM of 4.4 degrees, an increase of the initial knee angle of 2.8 degrees, and an increase in tibia1 rotation of 2.9 degrees. The kinetic variables measured showed an increase in the vertical force peak during landing of 4.7% of bodyweight, and a decrease in maximal anterior-posterior force at push-off of 1.8% of bodyweight. Gender
Across shoes, females were found to have a smaller initial shoe eversion of 1.1 degrees, a smaller tibia1 rota-
Changes in gait pattern as a function of age may be interpreted as a result of changes in muscular strength. Decrements in dorsiflexor and plantarflexor muscle strength were found to occur in healthy males and females starting at about age 50 years12.13. Significant decreases in both the maximum isometric and isokinetic torques were reported that could be generated by the knee extensors14. Reduced walking speed in the elderly has been associated among other factors with a decrease in calf strength l5. Changes in gait pattern as a function of age may also be interpreted as a result of changes in motor control as a function of age. Reduced stability, for instance, may be associated with motor unit changes that occur with increasing age. Losses of motor units were found with increasing age, with large reductions after age 6016. Fast twitch muscle fibres decrease with age while the motor units of the slow twitch fibres reinnervate some neighbouring fibres13.i6.17.Related to this is an increase in time to peak tension and time to relaxation13. As a result the muscle will not be able to create force as quickly during motions requiring a fast response, such as recovering from a trip or slip. Therefore movements that challenge the elderly with respect to time are likely to show differences when compared with young adults. Performance in cognitive tasks has also been related to time constraints. Although it is generally thought that cognitive functioning decreases with age, it has been shown’* that if test length is reduced and time is
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1994; 2: No 4
Table 2. Mean and (SD) of ROM and PoM results for males and females for selected variables using the laboratory shoe for ROM and PoM with n(20-39) = 29 (14 male and 15 female), n(40-59) = 30 (15 male and 15 female, n(60-69) = 29 (15 male and 14 female, and for n(70-79) = 30 (16 male and 14 female). PD = plantar- dorsiflexion, IE = in- eversion, AA = ab- adduction Var
Age
ROM All (years)
ROM Male (years)
ROM Fern (years)
PoM All (deg)
PoM Male (deg)
PoM Fern (de@
PD
20-39
70.7 (12.9) 65.7 (10.1) 62.1 (6.0) 59.6 (8.6)
66.8 (15.6) 67.0 (8.3) 61.6 (6.1) 60.1 (9.0)
74.2 (8.9) 64.3 (11.7) 62.7 (6.1) 59.1 (8.3)
29.9 (3.9) 28.2 (4.1) 27.0 (4.2) 25.5 (3.7)
28.8 (3.7) 28.2 (3.3) 26.4 (3.5) 25.0 (3.1)
31.2 (4.0) 27.5 (4.5) 27.0 (3.8) 25.4 (3.9)
35.4 (9.1) 34.5 (10.0) 29.6 (6.6) 28.7 (7.1)
32.0 (5.9) 35.1 (10.1) 32.0 (6.1) 30.0 (6.2)
38.6 (10.4) 33.8 (10.1) 27.1 (6.5) 27.2 (7.9)
16.2 (4.3) 16.2 (3.9) 16.4 (4.6) 16.7 (3.9)
17.0 (5.0) 15.8 (3.8) 15.7 (5.3) 16.8 (4.4)
14.4 (3.0) 15.6 (4.5) 17.3 (5.4) 16.6 (3.6)
72.0 (16.1) 63.2 (12.1) 59.8 (9.8) 58.4 (11.3)
67.7 (16.0) 64.7 (10.3) 61.4 (6.9) 57.4 (9.0)
76.0 (15.7) 61.6 (13.8) 58.1 (12.3) 59.5 (13.7)
15.4 (5.5) 14.4 (4.1) 12.7 (5.0) 11.2 (4.6)
15.3 (2.9) 13.5 (4.4) 11.1 (3.5) 10.0 (3.2)
15.6 (6.6) 14.8 (3.4) 13.8 (6.0) 13.5 (4.4)
40-59 60-69 70-79
IE
20-39 40-59 60-69 70-79
AA
20-39 40-59 60-69 70-79
increased, the elderly are able to perform as well in cognitive tests of fluid intelligence (problem solving in tasks dealing with complex relations and novel materialsi9) as young adults. The results found in this study are discussed with these two major aspects, reduction of muscle strength and change in motor control as a function of age, in mind. Obviously the set-up of the experiment does not allow conclusive interpretation. However, some indications for one or the other results may be appropriate. The differences for significant variables were between 3.2 and 6.5 degrees, generally considered a small difference in gait analysis. The reduction of the PoM for the ankle joint with increasing age corresponds to a stiffening of the movement. A similar trend can be seen in the knee joint (Figure 4). The reduction of PoM may be associated with the shortening of the stride length, which has been reported earlierG4, and is thought to be a strategy to maintain stability. The results for the movement in the ankle joint complex showed a somewhat contradictory behaviour with respect to movement stability. The plantar- dorsiflexion PoM decreased with increasing age, which was expected and is interpreted as a strategy to increase stability. Additionally the foot ab- adduction decreased with increasing age, which again may be interpreted as a strategy to increase stability. However, the third rotational movement of the ankle joint complex, shoe eversion, showed an increase with increasing age which
cannot be interpreted as a strategy to increase stability. It may be a result of an increased eversion moment due to a slightly more abducted position of the foot for the older subject groups and/or a result of an increased laxity of the plantar ligaments supporting the arch of the foot which occurs with age”. The tendency to become more flatfooted with age usually results in an increase in abduction as well as eversion”. The maximum absolute differences for significant variables in the kinetic analysis were small and within the sensitivity of the force plate. They are not considered relevant and will not be discussed further.
ANKLEPGM We21
+
KNEEPGM
+ Idrol
Figure 4. Change of the PoM for the ankle and knee joint as a function of age for male and female subjects together (mean and standard error)
Nigg et al.: Gait as a function of age and gender Gender
The statistical analysis showed significant differences between males and females for some of the kinematic and kinetic variables; however, the absolute differences were quite small and are not considered functionally relevant. They will not be discussed further. Comparison of PoM and ROM results
PoMs for plantardorsiflexion. foot in-eversion. and foot ab- adduction from the present study were compared with corresponding active ROM measurement& as summarized in Table 2. No relationship between the PoM and the ROM results could be found for foot ineversion, but consistent results were found for the relationship between the PoM and the active ROM for foot plantardorsiflexion and abadduction. As the ROM of plantardorsiflexion decreases with increasing age there was a corresponding decrease in the PoM found during gait (Figure 5 top). A similar result was found for ab adduction (Figure 5 bottom). This relationship indicates that similar mechanisms may be acting to influence ROM and PoM. One may speculate that the major influence is muscle strength, which decreases with increasing age and affects similarly ROM and PoM.
219
and it is speculated that the measured differences would be more pronounced for inactive test subjects. Second, the differences discussed in this paper were consistent throughout all footwear conditions. which suggests that the results are a pattern rather than a pure coincidence. The differences found across age and gender could consistently be explained with decreasing strength and the attempt to increase stability during locomotion with increasing age. There was no evidence that aspects of motor control would play a major role for the selected movement of walking. However, it is speculated that the findings may be different for movement tasks closer to the limits of the test subjects. The correlation between PoM and ROM for plantar dorsiflexion and ab-adduction suggests that strength training for the ankle (and possibly knee) complex may change the gait characteristics for the elderly and provide an improved (subjective or objective) feeling of stability, since all the changes in movement seem to point toward effects of a decrease in strength. Acknowledgements This research was supported by a grant from Fitness and Lifestyle Canada and by Adidas. The authors would like to thank Margo Fraser for her help in data analysis and editing.
General discussion
The differences found as a function of age were rather small and one may debate their relevance. There are at least two facts that suggest in the view of the authors that some of these differences are relevant. First, the subjects included in the study were all physically active POM
WI
PLANTAR-DORSIFLEXION
3+---t-I
I
26 26 ROM
__
POM IAS-ADDUCTION
16 14
I
-+ I
female
+
male
12
Figure 5. Relationship between the PoM and the ROM for dorsiflexion-plantarflexion (top) and abduction-adduction (bottom) for male and female subject groups.
Appendix Description of marker locations
A. Greater trochanter: lateral on the thigh on a line between the greater trochanter and the lateral femoral epicondyle, in as close proximity to the greater trochanter as possible. B. Mid-anterior femur: anteriorly in the mid-sagittal plane of the thigh between spheres A and C. C. Lateral epicondyle: on the lateral epicondyle of the femur. D. Tibia1 tuberosity: on the tibia1 tuberosity in the mid-sagittal plane of the lower leg. E. Posterior lateral mid-tibia: posterolateral on the lower leg, between spheres D and F. F. Anterior lateral lower tibia: anterolateral on the calf, approximately 10 cm proximal to the lateral malleolus. G.. Superior navicular: in the mid-sagittal plane of the foot, approximately halfway between the toe and the heel, in a straight line with markers B and D. H. Lateral calcaneus: lateral on the foot in approximate alignment with the extrapolation of a line from the lateral epicondyle-lateral malleolus, and in a straight line with markers A and C.
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Head of fifth metatarsal: on the head of the fifth metatarsal, articulation with the fifth phalanx.
just prior to the
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Nigg BM Biomechanics of Running Shoes. Champaign, IL, Human Kinetics, 1986; 59-60 Abdel-Aziz YI, Karara HM. Direct linear transformation from comparator coordinates into object-space coordinates. In: Proceedings ASP/W Symposium on Close-Range Photogrammetry. American Society of Photogrammetry, Falls Church, VA., 1971; 1-18 Grood ES, Suntay WJ. A joint coordinate system for the clinical description of three-dimensional motions:
application to the knee. J Biomech Eng 1983; 105: 136-44 10 Nigg BM, Skleryk BN. Gait Characteristics of the elderly. Clin Biomech 1988; 3: 79-87 11 Moore KL. Clinically Oriented Anatomy. Williams and Wilkins, Baltimore, USA., 1992; 495-6 12 Vandervoort AA, McComas AJ. Contractile changes in opposing muscles of the human ankle joint with aging. J Appl Physiol 1986; 61(l): 361-7 13 Vandervoort AA Chesworth BM, Cunningham DA et al. Age and sex effects on mobility of the human ankle. J Gerontol 1992; 47(l): M17-21 14 Murray MP, Gardner GM, Mollinger LA, Sepic SB. Strength of isometric contractions. Knee muscles of men aged 20 to 86. Phys Ther 1980; 60: 412-19 15 Bendall MJ, Bassey EJ, Pearson MB. Factors affecting walking speed of elderly people. Age Aging 1989; 18: 327-32
16 Brown WF, Strong MJ, Snow, R. Methods for estimating numbers of motor units in biceps-brachialis muscles and losses of motor units with aging. Muscle Nerve 1988; 11: 423-32 . 17 Kanda K, Hashizume K. Changes in properties of the medial gastrocnemius motor units in aging rats. J Neurophysiol 1989; 61(4): 73746 18 Baltes PB, Kliegl R, Dittmann-Kohli F. On the locus of training gains in research on the plasticity of fluid intelligence in old age. J Educ Psychof 1988; 80(3): 392-400
19 Baltes PB, Willis SL. Plasticity and enhancement of intellectual functioning in old age: Penn State’s adult development and enrichment project (ADEPT). In: Craik FJM, Trehub SE, eds. Aging and Cognitive Processes. Plenum Press, New York, 1982; 353-89