- Email: [email protected]
Comparisons of plantar pressures between the elderly and young adults
T W Kernozek PhW, E E LaMott PhD* ‘Division of Kinesiology, Universitv of Minnesota, Minneapolis, and Physical Education, Concordia College St Paul, Minnesota,
and ZDepartment USA
of Health
Summary variables were compared for 35 elderly (71-90 years) and 35 young adult (aged 18-24 participants. Plantar pressures were measured at 70 Hz with a capacitiv8 platform with a resolution of two sensors per square centimetre. Subjects were required to walk barefoot at their ‘preferred’ gait speed down a 15-m walkway. Gait speed was determined via a photoelectric timing system. Five right foot pressure trials w8re gath8red and stored. During analysis seven plantar r8gions were identified: one heel, on8 midfoot, thfe8 for8foot (medial, central, and lat8ralL and two toe (m8dial toe or hallux and Ieaser toes). Averages were genefeted for each loading variable respective to each plantar region. Gait speed was signifiiantly slower for the elderly than the young adults. Thus, gait spe8d was used as a covariate in a multivariate analysis of covariance (MANCOVAI to det8ct differenc8s between the yowng ad&s and the elderly. Similar loading charact8ristics were found in the heel region of th8 foot. For the young adults, great8r plantar loading occurred across the midfoot region. There was a difference in the loading rate across the medial forefoot region for th8 elderly and no differences in force or peak pressures. The medial forefoot region exhibit8d gr8et8st peak pressure for the elderly. No diff8rences wer8 found betw8en groups in the central for&oot. The elderly exhibited a greater contact area and less contact time. For the 8ld8rly, less force was produced relative to the medial toe mgion. No differences Loading
betwe8n exhibited.
the loading
characteristics
of the lateral
toe region
betw8en
the two groups
were
Key words: Elderly, gait, pressure, force, kinetics Gait
&
Posturs
1995; Vol. 3: 143-148, September
Introduction The elderly comprise the fastest growing portion of the population. Projections indicated that the number of people aged 65 and older will increase by the year 2020 to over 52 million and people aged 8.5 and older will increase to more than 6.7 million’. The obstacles associated with an ageing society in the 1990s and beyond clearly present many challenges to physicians, therapists as well as movement scientists. Schultz (19912)~encouraged researchers to focus on the mobility impairments of the elderly. Mobility research Received: IO September 1994 Accepm/: 5 December 1994 Correspondence und reprint requests
of Kinesiology. USA
to: T W Kernozek PhD, Division University of Minnesota, Minneapolis, MN S5455
0966-636Z95 $09.50 0 Elsevier Science B.V. All rights reserved
may direct clinical interventions as a means of preventative care. The inability to perform basic activities of daily living such as gait increases the elderly individual’s propensity for nursing home care. Schneider and Guralink’ indicated that the average nursing home cost in the United States in 1985 was approximately $23 600 per resident, costing society over $3 1. I billion annually. The number of elderly nursing home residents is expected to increase over 3 times by the year 20403. This increase presents a considerable financial concern to our health-care system as well as our society, With advancing age the foot experiences changes in appearance, joint mobility> alterations in proprioception, and muscle and plantar fat pad atrophy”. As an individual ages these subtle changes may adversely affect overall foot function during gait. Thus compensatory mechanisms may be seen in the gait patterns of
144
Gait & Posture
1995: 31 No 3
the elderly to accommodate these changes. The purpose of this study was to characterize the loading patterns of the elderly individual during gait. Pressure patterns were compared to a group of young adults. At present no normative pressure distribution data exists in the literature related to the elderly during normal gait. Methods Subjects
This investigation was conducted using 35 elderly individuals (28 females, 7 males) aged between 71 and 90 years and a group of 35 young adults (25 females, 10 males) aged between 18 and 24 years. All elderly participants were volunteers from various independent living communities throughout a metropolitan area. Ail young adults were volunteers from fitness activity classes at a metropolitan university. All individuals were considered to be in good health during the time of study. No attempts were made to differentiate between the various foot types or lower extremity alignments. The mean age of the elderly individuals was 78 years (SD 3.01) while that of the young adults was 22 years (SD 2.15). Mean weight for the elderly individuals was 67.91 kg (SD 14.53) and that for the young adults was 67.73 kg (SD 11.97). Procedures
Pressure distribution was assessed for the right foot during full gait down a 15-m walkway. All participants were required to walk barefoot. Data were collected using a capacitive pressure measurement platform (EMED SF Pedography Analyser, Novel GMBH, Munich) and stored on floppy disk for further analysis. The pressure platform consisted of a 32 X 62 sensor matrix with a resolution of two sensors per square centimetre. The sampling frequency was fixed at 70 Hz and was autotriggered by first contact with the platform, which initiated data collection. The pressure platform was located flush within a wooden walkway at the approximate midpoint. The walkway was painted a flat black and the housing of the pressure platform was covered with a flat black paper to make the platform less conspicuous. Infrared photocells were interfaced with a digital clock and located 3 m apart, equidistant from the centre of the platform. Gait speed was calculated by dividing this 3-m distance by the time taken to travel that distance. Gait speed was not used as a criterion for an acceptable trial but rather for descriptive purposes. Participants in this investigation walked across the platform at their self-selected walking speed. No attempts were made to artificially control gait speed or force an individual to walk at a certain pace. Trials in which the participant altered their stride or did not place their whole foot on the platform were not stored. Five acceptable trials were gathered for each participant. Hughes et al. (1991)’
indicated that there was excellent reliability using a similar capacitive platform with five trials per participant. Plantar regions
For each pressure measurement trial seven plantar regions on the foot were identified: one heel region, one midfoot region, three forefoot regions, and two toe regions. The three forefoot regions underneath the area of the metatarsal heads were divided into equal thirds. The medial forefoot region was underneath the first metatarsal head, the central region was underneath the second and third metatarsal heads, and the lateral region was underneath the fourth and fifth metatarsal heads. The toe region was subdivided into two regions consisting of the hallux and the lesser toes. Figure 1 illustrates the various geometric plantar regions or masks. These regions were determined using the maximum pressure picture of each trial using the Novel Multimask software. The following variables were generated for each of the seven plantar regions of the foot: total area of the maximum pressure picture (cm*), total force of the maximum pressure picture (% BW), peak pressure of the maximum pressure picture (kPa), length of the contact phases (ms), pressure time integrals (kPa*s), force time integrals (% BWs), instant of peak pressure (ms), and the instant of peak force (ms). Both the pressure and force time integrals enable the load distribution to be related to anatomical regions of the foot. Similar analyses have been performed by other researchers to understand foot function8s9. Results and discussion Sample descriptives
The purpose of this study was to characterize the foot pressure distribution of the elderly individual during gait. Comparisons were made to a group of young adults. Pearson product moment correlations were performed between gait speed and all the loading variables for the foot across both groups. A significant positive correlation was found between gait speed and the total vertical force of the maximum pressure picture, r = 0.66, P < 0.01. A small non-significant negative correlation was found between gait speed and peak pressure of the maximum pressure picture, r = -0.07, P > 0.05. Clarke (198O)‘O had also shown a poor relationship between plantar pressures and gait speed. Results showed an increase in plantar pressures of 7.2% across all foot regions with an increase in gait speed of 1.33 m s-l to 1.79 m s-l. Significant negative correlations were found between gait speed and each of the following: stance time in milliseconds, r = -0.54, P c 0.01; the pressure time integral, r = -0.43, P < 0.01; the force-time integral, r = -0.43, P < 0.01; the instant of peak pressure in
Kernozek
and LaMott:
Plantar
pressures
in the elderly
and young
145
participants was 0.95 m s-i (SD 0.11) and the young adults was 1.28 m s-l (SD 0.09). Previous research has indicated that free gait speed has been 4-g!/& slower at age 60 than at age 20 using cross-sectional samplesi’,‘z. The results of this study found the free gait speed of the elderly participants to be 0.3 m s-i slower than data previously reported Ii-l’. This slower gait speed may also be reflected in the recruitment of older participants in this study. Regional foot comparisons between groups
Figure 1. Seven plantar regions or ‘masks’ used in the analysis. HL, heel; MF, midfoot; MFF, medial forefoot; CFF, central forefoot; LFF lateral forefoot; MT, medial toe; LT, lesser toe.
milliseconds, r = -0.60, P c 0.01; and the instant of peak force in milliseconds, r = -0.48, P < 0.01. Thus as speed of gait increases each of these time-related variables tend to decrease. An independent f test found that the mean gait speed was significantly less for the elderly participants than for the young adults, t(68) = -8.60, P = 0.00. The mean gait speed for the elderly
Since gait speed was significantly different between the elderly and young adult groups, a muitivariate analysis of covariance (MANCOVA) was used to detect significant differences between the groups in each of the loading variables relative to the seven regions of the foot. Gait speed was used as the covariate. Plantar pressure data. Figure 2 shows the adjusted means for each plantar region of the foot across the two groups. The only significant difference between the two groups existed in the midfoot (MF) region. The young adults exhibited significantly greater plantar pressure in the MF than the elderly participants, F(l,67) = 14.01, P = 0.000. When examining the other plantar regions of the foot some interesting trends appeared. The greatest peak pressure in the elderly participant occurred in the medial forefoot (MFF) region. This area, which included the region under the first metatarsal head, exhibited a peak pressure of 521.90 kPa. For the elderly participants load was higher on the MFF region than any other forefoot region. Pressure data from the medial forefoot for the elderly participants were higher than previous data presented on normal adults by Hennig et al.X.9. For the young adults the area of greatest pressure was the medial toe (MT) region. This plantar region underneath the hallux exhibited a peak pressure of 433.50 kPa. The second largest pressure for the elderly was 404.56 kPa in the central forefoot region (CFF). When comparing the groups, the young adults tended to load the MFF and CFF regions of the foot more evenly than the elderly (384.99 kPa and 395.73 kPa respectively). Pressure data for the young adults were comparable to other data in the literature8,9. Heel region (HL). Comparisons were made between the elderly and young adults relative to the HL region of the foot. There were no significant differences in the loading variables between the two groups relative to the HL region. These results were contradictory to the statements by Evanskiij and Edelsteir#, which noted that the elderly individual tended to exhibit less force on heel during early stance due to a shorter stride and gait speed. In the present study stride length was not measured but there were no differences in heel loading between groups when gait speed was used as a covariate. h4idfoot region (MF). When examining the MF region there were several significant differences
146
Gair & Posrure
1995; 3: No 3
PRESSURE (kPa)
600 500 400 300 200 . .
100 0
-
HL
MF
MFF
CFF
LFF
H
LT
PLANTAR REGIONS OF THE FOOT Figure
2. Peak pressures:
elderly
versus
young
adults.
n elderly
between the groups. As mentioned previously, the elderly participants exhibited a lower peak pressure (89.50 kPa) than the young adults (26.90 kPa) when examining the adjusted means for the MF region. The time that this region of the foot was in contact with the ground was significantly less for the elderly participants, F(l,67) = 13.10, P = 0.001. The adjusted means for the elderly participants were 63.46 ms and the young adults were 71.95 ms of contact time. The elderly participants had a significantly lower pressure time impulse than the young adults, F(l,67) = 7.62, P = 0.007. The pressure-time integral adjusted means were 22.20 kPa*s for the elderly participants and 64.50 kPa*s for the young adults. There was a significantly lower force time integral on the MF region of the elderly participants when compared the young adults, F(l,67) = 6.93, P = 0.003 (see Figure 3). The adjusted means for the elderly participants were 4.04%BW*s compared to 7.73%BW*s for the young adults. The peak pressure and peak forces occurred significantly earlier in MF region of the foot for the elderly participants when compared to the young adults, F(l,67) = 17.44, P = 0.000 and F(l,67) = 4.32, P = 0.042 respectively. The adjusted means for the elderly group for time of peak pressure and time of peak force were
0 young
adults;
*PC 0.05.
190.42 ms and 232.01 ms respectively. The adjusted means for time to peak pressure and time of peak force were 335.37 ms and 280.05 ms for the young adults. These results indicate a higher rate of loading for the elderly participants when compared to the young adults. Medial forefoot region (MFF). The MFF region underneath the first metatarsal head yielded one significant difference in the loading variables between the two groups. The instant of peak force for the elderly participants was significantly earlier when compared to the young adults, F(l,67) = 4.08, P = 0.47. The adjusted means were 448.44 ms for the elderly participants and 501.78 ms for the young adults. This earlier occurrence contributed to a greater loading rate across the region of the first metatarsal for the elderly participants. The peak force for the elderly participants occurred 217.15 ms prior to the foot leaving the floor as opposed to 162.50 ms for the young adults. The MFF region of the foot was the area of greatest pressure in the elderly participants. Central forefoot region (CFF). When examining the CFF region of the foot underneath metatarsal heads two and three there were no significant differences between the elderly participants and the young adults
Kernozek
FORCE TIME
INTEGRAL
and LaMott:
Plantar
pressures
in the elderly
and young
147
(%BW’s) --
I4 12 10 8 6 4 2 -
0 HL
MF
MFF
PLANTAR m Figure
3.
Force time
integrals:
CFF
versus
MT
LT
REGIONS OF THE FOOT
ELDERLY elderly
LFF
young
m adults
for any of the loading variables. As a result similar loading characteristics were exhibited for the central forefoot region of the foot between groups. Lateral forefoot region (LFF). When examining the LFF region of the forefoot underneath the fourth and fifth metatarsal heads there were two significant differences in the loading variables between the elderly participants and the young adults. The elderly participants had significantly greater contact area relative to the maximum pressure picture than the young adults, F(1,67) = 25.56, P = 0.000. The adjusted means were 13.69 cm2 for the elderly participants and 9.66 cm* for the young adults. This greater contact area may be due to the splaying of the foot and the build up of callus tissue often seen in the geriatric patient. The elderly participants did spend significantly less time in the LFF region of the foot compared to the young adults, F(1,67) = 4.22, P = 0.044. The adjusted means for the elderly participants was 562.99 ms and 604.68 ms for the young adults. Medial toe region (MT). When examining the MT region of the forefoot underneath the hallux there were two significant differences in the loading variables between the elderly participants and the young adults.
YOUNG
ADULTS
*f c 0.05
The elderly participants exhibited significantly lower total force than the young adults, F(1,67) = 4.64, P = 0.035. The adjusted means were 20.82%BW for the elderly and 26.14%BW for the young adults. The elderly participants produced a significantly smaller force time integral than the young adults. The elderly produced a force time integral of 4.38%BW*s when compared to 5.85%BW*s for young adults (see Figure 3). These results may indicate poor propulsion from the hallux during the gait of the elderly in comparison to the young adults. Lateral toe region (LT). There were no significant differences in the LT region underneath the lesser toes in any of the loading variables between groups. Thus similar loading characteristics were seen between the elderly participants and the young adults. Conclusions The present study compared the free gait pressure patterns under the feet of 35 elderly participants and 35 young adults. Pressure was measured at 70 Hz with a capacitive platform with a resolution of two sensors
148
Gair & Posrure
1995; 3: No 3
per square centimetre. The foot was divided into seven plantar regions for analysis. Similar loading characteristics were found in the HL region of the foot when comparing the elderly participants to the young adults. Greater plantar loading was exhibited across the MF region for the young adults. The young adults yielded greater contact times, greater forces, greater force and pressure time integrals, and greater time to peak pressure and force. The loading rate on the MFF was greater for the elderly participants than the young adults, with no significant differences in force or localized pressures. However, the elderly participants did exhibit the greatest plantar pressures across the MFF region of the foot. No differences in plantar loading were found between groups relative to the CFF. The elderly participants exhibited greater contact area and less contact time in the LFF region compared to the young adults. Less force was produced relative to the MT region in the elderly participants. There were no differences between the loading characteristics of the LT region between the two groups. Acknowledgements We would like to thank the All University Council on Aging at the University of Minnesota for their support in this research project. References 1 Schneider EL, Guralink JM. The aging of America impact on health care costs. JAMA 1990; 263: 2335-2340 2 Schultz AB. Mobility impairment in the elderly: chal-
lenges for biomechanics research. J Biomech 1992; 25: 5 19-528
3 Olshansky SJ, Ault AB. The fourth stage of the epidemiological transition: the age of degenerative diseases. Milbunk
Q 1986; 64: 355-391
4 Edelstein JE. Foot care for the aging. Phys Ther 1988; 68: 82-86 5 Jahss MH. Geriatric aspects of the foot and ankle. In: Rossman I, ed. Clinical Geriatrics, 3rd edn. Philadelphia,
JB Lippincott 1986 6 Walker JM, Sue D, Miles-Elkousky N, Ford G, Trevelyan H. Active mobility of the extremities in older subjects. Phys Ther 1984; 64: 919-923 7 Hughes J, Pratt L, Linge K, Clark P, Klenerman L. Reliability of pressure measurements: the EMED F system. Clin Biomech 1991; 6: 14-18 8 Hennig EM, Rosenbaum D. Pressure distribution patterns under the feet of children in comparison with adults. Foot Ankle 1991; 11: 306-311 9 Hennig EM, Staats A, Rosenbaum D. Plantar pressure distribution pattern of young school children in comparison to adults. Foot Ankle 1994; 15: 3540 10 Clarke TE. The pressure distribution under the foot during burejoot wulking. [Doctoral dissertation]. The Pennsylvania State University, 1980 I Bassey EJ, MacDonald IA, Patrick JM. Factors affecting heart rate in self paced walking. Eur J Appl Physiol 1982; 48: 105-115 2 Himann JE, Cunningham DA, Rechnitzer PA, Paterson DH. Age related changes in speed of walking. A4ed Sci Sports Exert 1988; 20: 161-166
3 Hageman PA, Blanke DJ. Comparison of gait of young women and elderly women. Whys Ther 1986; 66: 1382-1387 14 Blanke DJ, Hageman PA. Comparison of gait of young men and elderly men. Whys Ther 1989; 69: 144148 15 Evanski PM. The geriatric foot. In: Jahss MH, ed. Disorders of the Foot. JB Lippincott, Philadelphia, 1982
and ZDepartment USA
of Health
Summary variables were compared for 35 elderly (71-90 years) and 35 young adult (aged 18-24 participants. Plantar pressures were measured at 70 Hz with a capacitiv8 platform with a resolution of two sensors per square centimetre. Subjects were required to walk barefoot at their ‘preferred’ gait speed down a 15-m walkway. Gait speed was determined via a photoelectric timing system. Five right foot pressure trials w8re gath8red and stored. During analysis seven plantar r8gions were identified: one heel, on8 midfoot, thfe8 for8foot (medial, central, and lat8ralL and two toe (m8dial toe or hallux and Ieaser toes). Averages were genefeted for each loading variable respective to each plantar region. Gait speed was signifiiantly slower for the elderly than the young adults. Thus, gait spe8d was used as a covariate in a multivariate analysis of covariance (MANCOVAI to det8ct differenc8s between the yowng ad&s and the elderly. Similar loading charact8ristics were found in the heel region of th8 foot. For the young adults, great8r plantar loading occurred across the midfoot region. There was a difference in the loading rate across the medial forefoot region for th8 elderly and no differences in force or peak pressures. The medial forefoot region exhibit8d gr8et8st peak pressure for the elderly. No diff8rences wer8 found betw8en groups in the central for&oot. The elderly exhibited a greater contact area and less contact time. For the 8ld8rly, less force was produced relative to the medial toe mgion. No differences Loading
betwe8n exhibited.
the loading
characteristics
of the lateral
toe region
betw8en
the two groups
were
Key words: Elderly, gait, pressure, force, kinetics Gait
&
Posturs
1995; Vol. 3: 143-148, September
Introduction The elderly comprise the fastest growing portion of the population. Projections indicated that the number of people aged 65 and older will increase by the year 2020 to over 52 million and people aged 8.5 and older will increase to more than 6.7 million’. The obstacles associated with an ageing society in the 1990s and beyond clearly present many challenges to physicians, therapists as well as movement scientists. Schultz (19912)~encouraged researchers to focus on the mobility impairments of the elderly. Mobility research Received: IO September 1994 Accepm/: 5 December 1994 Correspondence und reprint requests
of Kinesiology. USA
to: T W Kernozek PhD, Division University of Minnesota, Minneapolis, MN S5455
0966-636Z95 $09.50 0 Elsevier Science B.V. All rights reserved
may direct clinical interventions as a means of preventative care. The inability to perform basic activities of daily living such as gait increases the elderly individual’s propensity for nursing home care. Schneider and Guralink’ indicated that the average nursing home cost in the United States in 1985 was approximately $23 600 per resident, costing society over $3 1. I billion annually. The number of elderly nursing home residents is expected to increase over 3 times by the year 20403. This increase presents a considerable financial concern to our health-care system as well as our society, With advancing age the foot experiences changes in appearance, joint mobility> alterations in proprioception, and muscle and plantar fat pad atrophy”. As an individual ages these subtle changes may adversely affect overall foot function during gait. Thus compensatory mechanisms may be seen in the gait patterns of
144
Gait & Posture
1995: 31 No 3
the elderly to accommodate these changes. The purpose of this study was to characterize the loading patterns of the elderly individual during gait. Pressure patterns were compared to a group of young adults. At present no normative pressure distribution data exists in the literature related to the elderly during normal gait. Methods Subjects
This investigation was conducted using 35 elderly individuals (28 females, 7 males) aged between 71 and 90 years and a group of 35 young adults (25 females, 10 males) aged between 18 and 24 years. All elderly participants were volunteers from various independent living communities throughout a metropolitan area. Ail young adults were volunteers from fitness activity classes at a metropolitan university. All individuals were considered to be in good health during the time of study. No attempts were made to differentiate between the various foot types or lower extremity alignments. The mean age of the elderly individuals was 78 years (SD 3.01) while that of the young adults was 22 years (SD 2.15). Mean weight for the elderly individuals was 67.91 kg (SD 14.53) and that for the young adults was 67.73 kg (SD 11.97). Procedures
Pressure distribution was assessed for the right foot during full gait down a 15-m walkway. All participants were required to walk barefoot. Data were collected using a capacitive pressure measurement platform (EMED SF Pedography Analyser, Novel GMBH, Munich) and stored on floppy disk for further analysis. The pressure platform consisted of a 32 X 62 sensor matrix with a resolution of two sensors per square centimetre. The sampling frequency was fixed at 70 Hz and was autotriggered by first contact with the platform, which initiated data collection. The pressure platform was located flush within a wooden walkway at the approximate midpoint. The walkway was painted a flat black and the housing of the pressure platform was covered with a flat black paper to make the platform less conspicuous. Infrared photocells were interfaced with a digital clock and located 3 m apart, equidistant from the centre of the platform. Gait speed was calculated by dividing this 3-m distance by the time taken to travel that distance. Gait speed was not used as a criterion for an acceptable trial but rather for descriptive purposes. Participants in this investigation walked across the platform at their self-selected walking speed. No attempts were made to artificially control gait speed or force an individual to walk at a certain pace. Trials in which the participant altered their stride or did not place their whole foot on the platform were not stored. Five acceptable trials were gathered for each participant. Hughes et al. (1991)’
indicated that there was excellent reliability using a similar capacitive platform with five trials per participant. Plantar regions
For each pressure measurement trial seven plantar regions on the foot were identified: one heel region, one midfoot region, three forefoot regions, and two toe regions. The three forefoot regions underneath the area of the metatarsal heads were divided into equal thirds. The medial forefoot region was underneath the first metatarsal head, the central region was underneath the second and third metatarsal heads, and the lateral region was underneath the fourth and fifth metatarsal heads. The toe region was subdivided into two regions consisting of the hallux and the lesser toes. Figure 1 illustrates the various geometric plantar regions or masks. These regions were determined using the maximum pressure picture of each trial using the Novel Multimask software. The following variables were generated for each of the seven plantar regions of the foot: total area of the maximum pressure picture (cm*), total force of the maximum pressure picture (% BW), peak pressure of the maximum pressure picture (kPa), length of the contact phases (ms), pressure time integrals (kPa*s), force time integrals (% BWs), instant of peak pressure (ms), and the instant of peak force (ms). Both the pressure and force time integrals enable the load distribution to be related to anatomical regions of the foot. Similar analyses have been performed by other researchers to understand foot function8s9. Results and discussion Sample descriptives
The purpose of this study was to characterize the foot pressure distribution of the elderly individual during gait. Comparisons were made to a group of young adults. Pearson product moment correlations were performed between gait speed and all the loading variables for the foot across both groups. A significant positive correlation was found between gait speed and the total vertical force of the maximum pressure picture, r = 0.66, P < 0.01. A small non-significant negative correlation was found between gait speed and peak pressure of the maximum pressure picture, r = -0.07, P > 0.05. Clarke (198O)‘O had also shown a poor relationship between plantar pressures and gait speed. Results showed an increase in plantar pressures of 7.2% across all foot regions with an increase in gait speed of 1.33 m s-l to 1.79 m s-l. Significant negative correlations were found between gait speed and each of the following: stance time in milliseconds, r = -0.54, P c 0.01; the pressure time integral, r = -0.43, P < 0.01; the force-time integral, r = -0.43, P < 0.01; the instant of peak pressure in
Kernozek
and LaMott:
Plantar
pressures
in the elderly
and young
145
participants was 0.95 m s-i (SD 0.11) and the young adults was 1.28 m s-l (SD 0.09). Previous research has indicated that free gait speed has been 4-g!/& slower at age 60 than at age 20 using cross-sectional samplesi’,‘z. The results of this study found the free gait speed of the elderly participants to be 0.3 m s-i slower than data previously reported Ii-l’. This slower gait speed may also be reflected in the recruitment of older participants in this study. Regional foot comparisons between groups
Figure 1. Seven plantar regions or ‘masks’ used in the analysis. HL, heel; MF, midfoot; MFF, medial forefoot; CFF, central forefoot; LFF lateral forefoot; MT, medial toe; LT, lesser toe.
milliseconds, r = -0.60, P c 0.01; and the instant of peak force in milliseconds, r = -0.48, P < 0.01. Thus as speed of gait increases each of these time-related variables tend to decrease. An independent f test found that the mean gait speed was significantly less for the elderly participants than for the young adults, t(68) = -8.60, P = 0.00. The mean gait speed for the elderly
Since gait speed was significantly different between the elderly and young adult groups, a muitivariate analysis of covariance (MANCOVA) was used to detect significant differences between the groups in each of the loading variables relative to the seven regions of the foot. Gait speed was used as the covariate. Plantar pressure data. Figure 2 shows the adjusted means for each plantar region of the foot across the two groups. The only significant difference between the two groups existed in the midfoot (MF) region. The young adults exhibited significantly greater plantar pressure in the MF than the elderly participants, F(l,67) = 14.01, P = 0.000. When examining the other plantar regions of the foot some interesting trends appeared. The greatest peak pressure in the elderly participant occurred in the medial forefoot (MFF) region. This area, which included the region under the first metatarsal head, exhibited a peak pressure of 521.90 kPa. For the elderly participants load was higher on the MFF region than any other forefoot region. Pressure data from the medial forefoot for the elderly participants were higher than previous data presented on normal adults by Hennig et al.X.9. For the young adults the area of greatest pressure was the medial toe (MT) region. This plantar region underneath the hallux exhibited a peak pressure of 433.50 kPa. The second largest pressure for the elderly was 404.56 kPa in the central forefoot region (CFF). When comparing the groups, the young adults tended to load the MFF and CFF regions of the foot more evenly than the elderly (384.99 kPa and 395.73 kPa respectively). Pressure data for the young adults were comparable to other data in the literature8,9. Heel region (HL). Comparisons were made between the elderly and young adults relative to the HL region of the foot. There were no significant differences in the loading variables between the two groups relative to the HL region. These results were contradictory to the statements by Evanskiij and Edelsteir#, which noted that the elderly individual tended to exhibit less force on heel during early stance due to a shorter stride and gait speed. In the present study stride length was not measured but there were no differences in heel loading between groups when gait speed was used as a covariate. h4idfoot region (MF). When examining the MF region there were several significant differences
146
Gair & Posrure
1995; 3: No 3
PRESSURE (kPa)
600 500 400 300 200 . .
100 0
-
HL
MF
MFF
CFF
LFF
H
LT
PLANTAR REGIONS OF THE FOOT Figure
2. Peak pressures:
elderly
versus
young
adults.
n elderly
between the groups. As mentioned previously, the elderly participants exhibited a lower peak pressure (89.50 kPa) than the young adults (26.90 kPa) when examining the adjusted means for the MF region. The time that this region of the foot was in contact with the ground was significantly less for the elderly participants, F(l,67) = 13.10, P = 0.001. The adjusted means for the elderly participants were 63.46 ms and the young adults were 71.95 ms of contact time. The elderly participants had a significantly lower pressure time impulse than the young adults, F(l,67) = 7.62, P = 0.007. The pressure-time integral adjusted means were 22.20 kPa*s for the elderly participants and 64.50 kPa*s for the young adults. There was a significantly lower force time integral on the MF region of the elderly participants when compared the young adults, F(l,67) = 6.93, P = 0.003 (see Figure 3). The adjusted means for the elderly participants were 4.04%BW*s compared to 7.73%BW*s for the young adults. The peak pressure and peak forces occurred significantly earlier in MF region of the foot for the elderly participants when compared to the young adults, F(l,67) = 17.44, P = 0.000 and F(l,67) = 4.32, P = 0.042 respectively. The adjusted means for the elderly group for time of peak pressure and time of peak force were
0 young
adults;
*PC 0.05.
190.42 ms and 232.01 ms respectively. The adjusted means for time to peak pressure and time of peak force were 335.37 ms and 280.05 ms for the young adults. These results indicate a higher rate of loading for the elderly participants when compared to the young adults. Medial forefoot region (MFF). The MFF region underneath the first metatarsal head yielded one significant difference in the loading variables between the two groups. The instant of peak force for the elderly participants was significantly earlier when compared to the young adults, F(l,67) = 4.08, P = 0.47. The adjusted means were 448.44 ms for the elderly participants and 501.78 ms for the young adults. This earlier occurrence contributed to a greater loading rate across the region of the first metatarsal for the elderly participants. The peak force for the elderly participants occurred 217.15 ms prior to the foot leaving the floor as opposed to 162.50 ms for the young adults. The MFF region of the foot was the area of greatest pressure in the elderly participants. Central forefoot region (CFF). When examining the CFF region of the foot underneath metatarsal heads two and three there were no significant differences between the elderly participants and the young adults
Kernozek
FORCE TIME
INTEGRAL
and LaMott:
Plantar
pressures
in the elderly
and young
147
(%BW’s) --
I4 12 10 8 6 4 2 -
0 HL
MF
MFF
PLANTAR m Figure
3.
Force time
integrals:
CFF
versus
MT
LT
REGIONS OF THE FOOT
ELDERLY elderly
LFF
young
m adults
for any of the loading variables. As a result similar loading characteristics were exhibited for the central forefoot region of the foot between groups. Lateral forefoot region (LFF). When examining the LFF region of the forefoot underneath the fourth and fifth metatarsal heads there were two significant differences in the loading variables between the elderly participants and the young adults. The elderly participants had significantly greater contact area relative to the maximum pressure picture than the young adults, F(1,67) = 25.56, P = 0.000. The adjusted means were 13.69 cm2 for the elderly participants and 9.66 cm* for the young adults. This greater contact area may be due to the splaying of the foot and the build up of callus tissue often seen in the geriatric patient. The elderly participants did spend significantly less time in the LFF region of the foot compared to the young adults, F(1,67) = 4.22, P = 0.044. The adjusted means for the elderly participants was 562.99 ms and 604.68 ms for the young adults. Medial toe region (MT). When examining the MT region of the forefoot underneath the hallux there were two significant differences in the loading variables between the elderly participants and the young adults.
YOUNG
ADULTS
*f c 0.05
The elderly participants exhibited significantly lower total force than the young adults, F(1,67) = 4.64, P = 0.035. The adjusted means were 20.82%BW for the elderly and 26.14%BW for the young adults. The elderly participants produced a significantly smaller force time integral than the young adults. The elderly produced a force time integral of 4.38%BW*s when compared to 5.85%BW*s for young adults (see Figure 3). These results may indicate poor propulsion from the hallux during the gait of the elderly in comparison to the young adults. Lateral toe region (LT). There were no significant differences in the LT region underneath the lesser toes in any of the loading variables between groups. Thus similar loading characteristics were seen between the elderly participants and the young adults. Conclusions The present study compared the free gait pressure patterns under the feet of 35 elderly participants and 35 young adults. Pressure was measured at 70 Hz with a capacitive platform with a resolution of two sensors
148
Gair & Posrure
1995; 3: No 3
per square centimetre. The foot was divided into seven plantar regions for analysis. Similar loading characteristics were found in the HL region of the foot when comparing the elderly participants to the young adults. Greater plantar loading was exhibited across the MF region for the young adults. The young adults yielded greater contact times, greater forces, greater force and pressure time integrals, and greater time to peak pressure and force. The loading rate on the MFF was greater for the elderly participants than the young adults, with no significant differences in force or localized pressures. However, the elderly participants did exhibit the greatest plantar pressures across the MFF region of the foot. No differences in plantar loading were found between groups relative to the CFF. The elderly participants exhibited greater contact area and less contact time in the LFF region compared to the young adults. Less force was produced relative to the MT region in the elderly participants. There were no differences between the loading characteristics of the LT region between the two groups. Acknowledgements We would like to thank the All University Council on Aging at the University of Minnesota for their support in this research project. References 1 Schneider EL, Guralink JM. The aging of America impact on health care costs. JAMA 1990; 263: 2335-2340 2 Schultz AB. Mobility impairment in the elderly: chal-
lenges for biomechanics research. J Biomech 1992; 25: 5 19-528
3 Olshansky SJ, Ault AB. The fourth stage of the epidemiological transition: the age of degenerative diseases. Milbunk
Q 1986; 64: 355-391
4 Edelstein JE. Foot care for the aging. Phys Ther 1988; 68: 82-86 5 Jahss MH. Geriatric aspects of the foot and ankle. In: Rossman I, ed. Clinical Geriatrics, 3rd edn. Philadelphia,
JB Lippincott 1986 6 Walker JM, Sue D, Miles-Elkousky N, Ford G, Trevelyan H. Active mobility of the extremities in older subjects. Phys Ther 1984; 64: 919-923 7 Hughes J, Pratt L, Linge K, Clark P, Klenerman L. Reliability of pressure measurements: the EMED F system. Clin Biomech 1991; 6: 14-18 8 Hennig EM, Rosenbaum D. Pressure distribution patterns under the feet of children in comparison with adults. Foot Ankle 1991; 11: 306-311 9 Hennig EM, Staats A, Rosenbaum D. Plantar pressure distribution pattern of young school children in comparison to adults. Foot Ankle 1994; 15: 3540 10 Clarke TE. The pressure distribution under the foot during burejoot wulking. [Doctoral dissertation]. The Pennsylvania State University, 1980 I Bassey EJ, MacDonald IA, Patrick JM. Factors affecting heart rate in self paced walking. Eur J Appl Physiol 1982; 48: 105-115 2 Himann JE, Cunningham DA, Rechnitzer PA, Paterson DH. Age related changes in speed of walking. A4ed Sci Sports Exert 1988; 20: 161-166
3 Hageman PA, Blanke DJ. Comparison of gait of young women and elderly women. Whys Ther 1986; 66: 1382-1387 14 Blanke DJ, Hageman PA. Comparison of gait of young men and elderly men. Whys Ther 1989; 69: 144148 15 Evanski PM. The geriatric foot. In: Jahss MH, ed. Disorders of the Foot. JB Lippincott, Philadelphia, 1982