**1. Introduction**

360 Health Management – Different Approaches and Solutions

Vincent, J.L. & Moreno, R. (2010). Clinical Review: Scoring Systems in the Critically Ill.

Zhou, X.H.; Li, S.M. & Gatsonis, C.A. (2008). Wilcoxon-Based Group Sequential Designs for

Comparison of Areas Under Two Correlated ROC Curves. *Statistics in Medicine,*

*Critical Care,* Vol.14, No.2 (207), pp. 1-9, ISSN 1364-8535

Vol.27, No.2, pp. 213-223, ISSN 0277-6715

Gait analysis is the systematic study of human walking. It is helpful in the medical management of those diseases which affect the locomotion systems. Recently, the gait motion capture systems are becoming widely used by doctors and physical therapists for kinematics analysis and biomechanics and motion capture research, sports medicine and physical therapy, including human gait analysis and injury rehabilitation. This chapter describes some new progress on human walking analysis that our group made in the past few years based on motion capture system.

Generally, ageing causes many changes to neuromuscular system of a human being, for an example, his walking capabilities degenerate by ageing. Because these changes sometimes result in an increase the number of falls during daily walking, especially after the age of 75, it is very important to study the age related changes in the walking gait of elderly subjects. Many researchers studied stability of human walking gait and it was quoted that human walking gait stability decreases with age increasing the risk of falls in elderly people.

Many studies have been reported about the change in the kinematics parameters with age (Arif et al., 2004). This paper only focuses on the progress of walking modeling and walking stability. Especially, in order to simplify the method of data acquisition, this paper suggests process of reduction on dynamic stability features through feature selection. That will help us analyze stability in a more clear way.

#### **1.1 Background of walking model**

Various methods are used to overcome the difficulties imposed by the extraction of human gait features. Two approaches are being used for human gait analysis: model-based and non-model-based methods.

The non-model-based method is applied in image-based gait analysis (marker-less analysis). Feature correspondence between successive frames is based upon prediction, velocity, shape, texture and colour. Small motion between consecutive frames is the main assumption, whereby feature correspondence is conducted using various geometric constraints.

For the first one, a priori shape model is established to match real data to this predefined model, and thereby extracting the corresponding features once the best match is obtained. Stick models and volumetric models are the most commonly used methods. The model-

Human Walking Analysis, Evaluation and Classification Based on Motion Capture System 363

The maximum Floquet multipliers (FM) are used to measure orbital stability of upper body in difference walking speed (Marin et al., 2006). Orbital stability changed very little with speed. The general purpose of (Kavanagh, 2006) is to examine factors that may influence

Balance in quiet upright stance, which was studied by (Stirling & Zakynthinaki, 2004), does not imply motionless stability, in fact a ML and AP body sway occurs. Almost 95% of the

Sutherland et al investigated the development of mature walking in children of age from one to seven years old (Sutherland et al., 1980). The objective of literature (PH. Chou, 2003) was to investigate the gait maturation of Taiwan children. Elderly subjects exhibits gait pattern characterized by reduced velocity, shorter step length and increased step timing variability (Hylton et al., 2003). It is mentioned that elderly people reduce their walking

While many walking stability indices have been proposed, there is still no commonly

The concept of gait symmetry itself is no acceptable unified definition, more often many people's research assumes that the normal gait is symmetric, which is to simplify data collection and analysis of gait. In fact gait symmetry was only evaluated with a small number of biomechanical studies that used quantitative data of the two lower limbs. In addition, the gait symmetry was not actually carried out enough exploration. It is because there is no participation of a considerable more number of test objects. One hand, the gait parameter of information provided is the effects of the movement not the reasons of the movement. This may also affect explaining the behaviour of the lower limbs. The other hand, the gait symmetry is not clearly defined, and the use only single gait parameters or a simple statistical

Maybe it stands to reason that a healthy man or woman has left leg and right leg symmetrically, and normal gait seems symmetric with ones right-side and left-side. What about the walking stability or dynamic balance if there is not so symmetric? Can we get

Gait symmetry is multifaceted. Normal walking seems right-left symmetry because normal people walk with their right foot and left foot. The ability of maintaining balance is essential to keep normal walking. Poor balance is an independent risk factor for falling, so anything that improves balance can have a positive effect on safety and function after stroke. Balance is described as the ability to maintain or move within a weight-bearing posture without falling. We have not found any trends study relating to walking stability and symmetry of

Yang in his doctoral thesis paper (Yang, 2001) proposed the symmetry indicators of step length and stride length, to describe the step in the role of gait symmetry. But phase symmetry and the step length symmetry are not fully reflects the characteristics of gait,

Walking is a complex dynamic activity. A good human model for gait analysis should be

method to compare which has made study of gait symmetry been more limited.

acceleration features of the upper body during walking.

speed to improve their walking stability in the literature.

some quantity or relationship of symmetry and balance?

human gait. And the trends indicated what meanings.

**2. Modeling assumptions and theoretical framework** 

simple, but extensive enough to capture the dynamics of most walkers.

especially the joint angle in the role of symmetry.

**1.3 Background of walking symmetry** 

accepted way to define, much less quantify, locomotors stability.

anterior-posterior sway happens around the ankle and the hip axis.

based approach is the most popular method being used for human motion analysis due to its advantages. It can extract detailed and accurate motion data.

Nash (Nash et al., 1998) proposed a parametric gait model consisting of a pair of articulated lines, jointed at the hip to extract moving articulated objects from a temporal sequence of images. Pendulum model was used to extract and describes human gait for recognition automatically (Cunado et al., 2003). The human leg was modelled as two pendulums joined in series. Zhang (Zhang et al., 2004) proposed a model-based approach to gait recognition by employing a 5-link biped locomotion human model. Akita (Akita, 1984) proposed a model consisting of six segments comprising of two arms, two legs, the torso and the head. Lee (Lee, 2003) suggested a 7-ellipse model, to describe a representation of gait appearance for the purpose of person identification and classification. A 2D stick figure model, which composed of 7 segments, was used to represent the human body, and joint angles and angular velocities are calculated to describe the gait motion (Yoo et la., 2002). Guo (Guo et al., 1994) represented the human body structure in the silhouette by a stick figure model which had 10 sticks articulated with six joints. Cheng (Cheng & Moura, 1998) represented the human body as a stick figure which was considered to be composed of 12 rigid parts. Dockstader (Dockstader et al, 2002) suggested the use of a hierarchical, structural model of the human body which had 15 points. Rohr (Rohr, 1994) proposed a volumetric model for the analysis of human motion, using 14 elliptical cylinders to model the human body. Karaulova (Karaulova et al., 2000) have used the stick figure model to build a novel hierarchical model of human dynamics represented using hidden Markov models.

#### **1.2 Background of walking stability**

Theoretically, human walking has rigid periodicity so the next step should repeat the first step strictly. That is to say, all steps must be consistent completely and have no any deference at all. In fact, there is no normal walking pattern and the walking pattern varies from person to person. These walking patterns are considered to be stable until and unless there is an evidence of fall of the person. During walking, human tries to generate periodic series of motions. But due to the physiological limitations, these motions do not re-main exactly periodic but contains some variability or randomness in it. He/she does not try to correct this variability or randomness of these motions if it remains within stability limits. This variability present in the walking patterns is due to not only internal perturbation but also due to external perturbations. The amount of variability present in the walking pattern reflects the quality of neuromuscular control of the human being.

There are many researches which are related to human walking stability. Corriveau et al compare the postural stability of elderly stroke patients with those of healthy elderly people using the distance between the centre of pressure (COP) and the centre of mass (COM) in terms of root mean square. Statistical significance of the COP-COM variable was larger in the stroke group than in healthy subjects, in both the anteroposterior (AP) and mediolateral (ML) directions (Corriveau et al., 2004).

Effect of age on the variability or irregularity of the acceleration of COM in ML, vertical and AP directions is analyzed by Arif et al, using approximate entropy technique for young and elderly subjects of subjects (Arif et al., 2004).

Literature (Hylton et al., 2003) tried to evaluate acceleration patterns at the head and pelvis in young and older subjects when walking on a level and an irregular walking surface. The subjects are two groups, 30 young people aged 22–39 years (mean 29.0, SD 4.3), and 30 older people with a low risk of falling aged 75–85 years (mean 79.0, SD 3.0).

The maximum Floquet multipliers (FM) are used to measure orbital stability of upper body in difference walking speed (Marin et al., 2006). Orbital stability changed very little with speed. The general purpose of (Kavanagh, 2006) is to examine factors that may influence acceleration features of the upper body during walking.

Balance in quiet upright stance, which was studied by (Stirling & Zakynthinaki, 2004), does not imply motionless stability, in fact a ML and AP body sway occurs. Almost 95% of the anterior-posterior sway happens around the ankle and the hip axis.

Sutherland et al investigated the development of mature walking in children of age from one to seven years old (Sutherland et al., 1980). The objective of literature (PH. Chou, 2003) was to investigate the gait maturation of Taiwan children. Elderly subjects exhibits gait pattern characterized by reduced velocity, shorter step length and increased step timing variability (Hylton et al., 2003). It is mentioned that elderly people reduce their walking speed to improve their walking stability in the literature.

While many walking stability indices have been proposed, there is still no commonly accepted way to define, much less quantify, locomotors stability.

#### **1.3 Background of walking symmetry**

362 Health Management – Different Approaches and Solutions

based approach is the most popular method being used for human motion analysis due to

Nash (Nash et al., 1998) proposed a parametric gait model consisting of a pair of articulated lines, jointed at the hip to extract moving articulated objects from a temporal sequence of images. Pendulum model was used to extract and describes human gait for recognition automatically (Cunado et al., 2003). The human leg was modelled as two pendulums joined in series. Zhang (Zhang et al., 2004) proposed a model-based approach to gait recognition by employing a 5-link biped locomotion human model. Akita (Akita, 1984) proposed a model consisting of six segments comprising of two arms, two legs, the torso and the head. Lee (Lee, 2003) suggested a 7-ellipse model, to describe a representation of gait appearance for the purpose of person identification and classification. A 2D stick figure model, which composed of 7 segments, was used to represent the human body, and joint angles and angular velocities are calculated to describe the gait motion (Yoo et la., 2002). Guo (Guo et al., 1994) represented the human body structure in the silhouette by a stick figure model which had 10 sticks articulated with six joints. Cheng (Cheng & Moura, 1998) represented the human body as a stick figure which was considered to be composed of 12 rigid parts. Dockstader (Dockstader et al, 2002) suggested the use of a hierarchical, structural model of the human body which had 15 points. Rohr (Rohr, 1994) proposed a volumetric model for the analysis of human motion, using 14 elliptical cylinders to model the human body. Karaulova (Karaulova et al., 2000) have used the stick figure model to build a novel

hierarchical model of human dynamics represented using hidden Markov models.

reflects the quality of neuromuscular control of the human being.

people with a low risk of falling aged 75–85 years (mean 79.0, SD 3.0).

Theoretically, human walking has rigid periodicity so the next step should repeat the first step strictly. That is to say, all steps must be consistent completely and have no any deference at all. In fact, there is no normal walking pattern and the walking pattern varies from person to person. These walking patterns are considered to be stable until and unless there is an evidence of fall of the person. During walking, human tries to generate periodic series of motions. But due to the physiological limitations, these motions do not re-main exactly periodic but contains some variability or randomness in it. He/she does not try to correct this variability or randomness of these motions if it remains within stability limits. This variability present in the walking patterns is due to not only internal perturbation but also due to external perturbations. The amount of variability present in the walking pattern

There are many researches which are related to human walking stability. Corriveau et al compare the postural stability of elderly stroke patients with those of healthy elderly people using the distance between the centre of pressure (COP) and the centre of mass (COM) in terms of root mean square. Statistical significance of the COP-COM variable was larger in the stroke group than in healthy subjects, in both the anteroposterior (AP) and mediolateral

Effect of age on the variability or irregularity of the acceleration of COM in ML, vertical and AP directions is analyzed by Arif et al, using approximate entropy technique for young and

Literature (Hylton et al., 2003) tried to evaluate acceleration patterns at the head and pelvis in young and older subjects when walking on a level and an irregular walking surface. The subjects are two groups, 30 young people aged 22–39 years (mean 29.0, SD 4.3), and 30 older

**1.2 Background of walking stability** 

(ML) directions (Corriveau et al., 2004).

elderly subjects of subjects (Arif et al., 2004).

its advantages. It can extract detailed and accurate motion data.

The concept of gait symmetry itself is no acceptable unified definition, more often many people's research assumes that the normal gait is symmetric, which is to simplify data collection and analysis of gait. In fact gait symmetry was only evaluated with a small number of biomechanical studies that used quantitative data of the two lower limbs. In addition, the gait symmetry was not actually carried out enough exploration. It is because there is no participation of a considerable more number of test objects. One hand, the gait parameter of information provided is the effects of the movement not the reasons of the movement. This may also affect explaining the behaviour of the lower limbs. The other hand, the gait symmetry is not clearly defined, and the use only single gait parameters or a simple statistical method to compare which has made study of gait symmetry been more limited.

Maybe it stands to reason that a healthy man or woman has left leg and right leg symmetrically, and normal gait seems symmetric with ones right-side and left-side. What about the walking stability or dynamic balance if there is not so symmetric? Can we get some quantity or relationship of symmetry and balance?

Gait symmetry is multifaceted. Normal walking seems right-left symmetry because normal people walk with their right foot and left foot. The ability of maintaining balance is essential to keep normal walking. Poor balance is an independent risk factor for falling, so anything that improves balance can have a positive effect on safety and function after stroke. Balance is described as the ability to maintain or move within a weight-bearing posture without falling. We have not found any trends study relating to walking stability and symmetry of human gait. And the trends indicated what meanings.

Yang in his doctoral thesis paper (Yang, 2001) proposed the symmetry indicators of step length and stride length, to describe the step in the role of gait symmetry. But phase symmetry and the step length symmetry are not fully reflects the characteristics of gait, especially the joint angle in the role of symmetry.
