Effect of the shoes on the movement of feet and legs during gait primary report S.Yamamoto, Ph.D.l), Y.Watanabe 2), H.Usui 2),

Y.Hayakawa, RPO 3)

l)Tokyo Metropolitan Prosthetic and Orthotic Research Institute 2)Watanabe Ltd.

3)Waseda College of Medical Arts and Sciences

Summary

The purpose of this study was to investigate the effect of the of shoes on the gait. The gait of eight normal subjects were measured without any shoes, with room shoes of soft soles, and with shoes which fit each subject's feet. The gait was measured by a three dimensional motion analysis system and force plates. The angular displacement of the lower, logs and feet, floor

reaction forces, and the joint moments were calculated. 　　　　　　　

The difference of shoes influences the inversion eversion angle and the magnitude of the moment due to floor reaction forces around the ankle joint. The subjects who showed eversion at the late stance showed inversion when he/stl wore appropriate shoes.

It is supposed that the appropriate shoes substitute the insufficient activity of the intrinsic muscles of the foot during gait

Key words: Shoes, Normal gait, Inversion eversion, Joint moment

1. Introduction

It is well known that the characteristics of shoes influences the

gait of not only patients but also normal people who seem to

have no problem in their legs. The effect of shoes have been

studied by many researchers but most of them measured the

pressure distribuéion ‘during the gait1)2). Recently the

relation between the pressure distribution and perceived comfort

in casual footwear was investigatedB). Other researchers

investigated the effect of the heel height 4) 5) and the shock

waves ,during the high—heel gait6). In these studies the

measurement was limited to the partial forces represented by the

pressure distribution.

The authors have seen many people who improve the pain at

the low back and the knee joint with appropriate shoes from the

experience of/shoe making and fitting. On the contrary we also

have seen méhy people who aggravate physical troubles for

example the Hullex Valgus with inappropriate shoes. The abpropriativeness

mainly depends on the fitness of the shoe shape .to the feet.

However, it is quite important to approximate the movement of the

feet of each subject to the normal movement by shoes in these

cases. From this point of View we measured the gait of subjects

with shoes by a three dimensional motion analysis system and

investigated the effects of shoes on the gait. Subjects were 8

normal people who have no trouble in their lower legs. The gaits

without any shoes, with room shoes of soft soles, and with shoes

which fit each subject feet were measured. The movement of the

lower leg, the floor reaction forces, and the joint moments were

examined and the evaluation procedure of the gait with shoes was

investigated.

2. Method

A three dimensional motion analysis system ( Oxford Metrics, Vicon 370) and force plates ( Kyowa Dengyo, EFP386AS) were used.

The reflective markers were put on both shoulders, both hip
joints ( 1cm upper and 2cm ahead the greater trochanter), lateral and medial sides of the left knee joint ( 2cm upper the medial tibial plateau), and both tops of the maliolus and 1st and 5th metatarsal heads and the toe of the left foot as shown In Fig. 1.As for the segments distal from the knee joint only the

movement of the left leg were measured because there seemed to be no difference between left and right sides of normal subjects.

The gaits without shoes, with room shoes consisted of rubber soft sole, and with shoes appropriate to each subject, which we called the basic shoes, were measured. The range of motion of each subject's foot was examined by hand and the basic shoes by which the normal range of motion could be obtained was selected among commercial available shoes. The appearances of shoes are

shown in Fig. 2. During the measurement with shoes markers
were put on shoes, but we confirmed whether there was no gap between the shoes and the feet. Any Instructions, for example the instructions about the cadence, were not given to subjects during the measurement.

Subjects were eight healthy people, 4 males and 4 females from 19 to 44 years old, who have no pathological trouble In their legs.

At first the static rigidity of the feet was
examined by the hand. And the passive range of motion of the ankle joint, such as degrees of dorsiflexion and plantarflexion

and degrees of inversion and eversion were measured by a
goniometer. Figure 3 shows the result of the range of motion of

all subjects. The horizontal axis represents each subject arrayed in the order of the examined rigidity from left to right. There was a tendency that the the feet of male subjects were more rigid than that of female subjects, and the

flexible feet showed large range of motion in the plantarfiexion and the Inversion. For convenience of the explanation below eight subjects were divided into three groups, such as rigid foot C subject A), intermediate foot C subject B, C, D, E, F ), and flexible foot ( subject G, H ).

3. Results

The rotation of the trunk and the pelvis and the angular

displacement of the axis of the knee, the ankle, and the
metatarsal joints In the sagittal, the coronal, and the transverse planes were calculated from the positions of reflective markers which were put on the both sides of each segment. The rotation angle around the longitudinal axes of the shank and the foot were also calculated. The moment around the knee and the ankle joints due to floor reaction forces were calculated by the position data and floor reaction force data. All data was normalized by the gait cycle which started at the time of heel contact.

Figure 4 shows the superimposed angular displacement of the ankle axis, which was defined by the line between both markers at the maliolus, in the coronal plane during the gait of two subjects without any shoes. Although four steps shown here were not obtained by the continuous measurement, the reproducabillty of data is remarkable. Therefore all gait data in the following are averaged data of 4 to 8 steps.

For all gait data described above the rotation of the foot showed the largest deviation among subjects. The axes of the ankle and the metatarsal joints were defined by the positions of markers attached at the both sides of each joint as shown in

Fig. 5a, and the relative angle of two axes was calculated.

The　foot consists of so cnany joints that it is difficult to represent the movement of the foot by a rotation around a single axis. The

angle calculated here is an approximate value of the inversion
eversion of the ankle joint. The inversion eversion rotation occurs at the subtalar joint. It is necessary to put many markers on each segment of the foot to calculate the accurate inversion eversion7). However, it was difficult to put markers

exactly on the surface of shoes, so the simple rotation described above was adopted. The zero value of the rotation represents the

value during standing and the plus value indicates the eversion.

Figure 6 shows the result of the inversion eversion of a subject with rigid foot, a subject with intermediate foot, and a subject with flexible foot. The result of barefoot, with room shoes , and the basic shoes are shown by the dotted line, broken line, and the solid line, respectively. The rigid foot rotates into inversion direction during the mid to late stance phase in any conditions as shown in Fig. Ba. The rotation angle of the intermediate foot during the mid stance shows a constant value in the case of barefoot and the room shoes, but inversion occurs when he wore basic shoes. This phenomena was observed among other subjects who have intermediate feet. The rotation of the

flexible foot is extremely large when she walked without any shoes, but it is restricted by shoes as shown in Fig. 6c.

Figure 7 shows the result of the rotational moment around the longitudinal axis of the foot due to floor reaction forces.

All shown in Fig. 5b the longitudinal axis of the foot was defined by the line connecting the midpoints of lateral and medial markers at the ankle and the metatarsal joints. The rotational moment due to floor reaction forces was calculated around this axis. The p

lus value indicates the direction which the floor reaction

forces　act to evert the foot. The result of the rigid foot
shows the large eversion moment during the mid to the late stance as shown in Fig. 7a., It is caused by the lateral location of the　center of pressure at the late stance.

The result of the　intermediate foot shows relatively small magnitude and it reduces

in the case of wearing shoes. This phenomena was observed among
other subjects who have intermediate feet. The magnitude of the moment of the flexible foot is small through the stance phase, and it shows that the center of pressure locates under the longitudinal axis of the foot.

4. Discussions

The results obtained here is shown schematically in Fig. 8. The effect of shoes is not evident in the case of rigid foot.

However, the magnitude of the moment which the floor reaction forces act to evert the foot reduces remarkably when subjects

with intermediate and flexible foot wore basic shoes.
The main reason of this reduction is the movement of the center of pressure toward the longitudinal axis of the foot during mid to late stance The role of the foot during the stance phase is to absorb the shock at the initial stance and to transmit the muscle forces of the plantarflexors to the floor at the time of push off. Therefore the foot is required two conflict characteristics, such as flexible at the initial stance and rigid at the late stance.

To obtain such characteristics the activity of intrinsic muscles during the mid to late stance stabilizes the foot so that the

foot acts as a lever to facilitate the smooth push off8). In
this study the activity of intrinsic muscles of subjects who have the intermediate and the flexible feet seems to be insufficient to make a rigid lever. In other words the Internal forces are insufficient to resist the external floor reaction forces which act to evert the foot. The eversion at the late stance causes　excessive load at the 1st metatarsal joint.

It might cause excessive distortion of the foot and the legs and subsequently aggravate the frambles of the whole body. On tne contrary tne' inversion occurs
during tne mid to late stance wnen the subjects wear basic snoes because tne moment to evert the foot reduces. it is said that the basic shoes substitutes the role o,f intrinsic muscles which makes the foot rigid.

From results obtained here it was clarified that the inversion eversion movement of the foot during mid to late stance was influenced by the characteristics of shoes. It might be useful to evaluate the gait" with shoes. We intend to measure the gait of other subject and investigate the effect of the characteristics of the shoes on the movement of upper body, such as the pelvis and the' trunk In the future.

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