**1. Introduction**

Postural balance is dynamic and demands constant amendments to adapt to external disturbances, by using vision, muscle activity, articular positioning and proprioception, and the vestibular system to prevent falls [1, 2]. Awareness of the body's position in space is determined by the integration of the visual, vestibular and somatosensory systems [3, 4]. The study of postural control is imperative for diagnosing balance disorders, as well as for assessing the effects of both therapeutic interventions and fall prevention programs. Postural stability is determined by mechanical factors that include both individual and environmental characteristics. This chapter focuses on various factors influencing the bipedal postural stability and provides an insight into the measures to facilitate improvement in the accuracy of diagnosis and quality of treatment and rehabilitation, thereby preventing falls and incapacities.

#### **2. Evolution of bipedal posture**

Our ancestors would have probably become extinct if they had not developed their bipedal posture including the corresponding transitional behavioral constraints. "Bipedalism evolved more as a terrestrial feeding posture than as a walking adaptation" [5]. The adapted bipedal posture brought various disadvantages like decreased velocity, increased time for social interaction, more chances of injuries from fall, more energy consumption, etc.

Advantages of bipedal posture could be many, namely freeing of hands, the visual advantage of being able to survey the surrounding, ability to acquire the skill of throwing, ability to carry infants while running, ability to reach out for food, ability for carrying food or provisioning, etc. But the most important hypothesis is that the ability to venture into shallow water made the ancestors to adapt bipedal posture.

### **3. Biomechanics of bipedal posture**

Upright postural balance describes the dynamics of body posture to prevent falling over a relatively small base of support under gravitational field. As for postural balance without stepping, the stable balancing condition can be analyzed using the following equation under assumption that a one link inverted pendulum describes human sway motions.

$$\text{Fy.x} \text{cop-Mg.x} \text{com} = \text{I } \theta \mathbf{a}. \tag{1}$$

generation showed more tendency to sway. Older adults performed the timed movement task much slower than the younger adults. Longer response times by the elderly have been attributed to slower event detection and impaired sensorimotor integration. Greve et al. [8] stated that women showed less movement on Biodex Balance System than men did, and these findings were similar to those of Rozzi et al. [9] who evaluated basketball and American football players using the same equipment. Lee and Lin [10] studied children and observed that girls presented better postural balance than boys. This could be due to anthropometric factors (greater in men), but other factors such as neuromuscular (flexibility) and neurophysiologic (processing of inferences), as well as the habit of using higher heels,

*Effect of Foot Morphology and Anthropometry on Bipedal Postural Balance*

Ledin and Odkvist [11] demonstrated that a 20% increase in body mass reduced the ability to make adjustments in response to external perturbations in the orthostatic position, with a consequent increase in postural instability. Chiari et al. [12] and Molikova et al. [13] in their respective studies conducted on individuals with normal or slightly higher than normal BMI have shown low correlations between body mass and balance. Majority of studies indicate that there was a direct relationship between obesity and increased postural instability, as evaluated by means of various tools and methods. Greve et al. [14] showed that in young adult males, the higher the BMI, the worst the postural balance, needing more postural adjustments to maintain balance in single leg stance. Greve et al. [8] proposed that the male group demonstrated stronger correlations for overall, anteroposterior and mediolateral stability index with body mass index (BMI) compared to women. They stated that there was a need for greater movements to maintain postural balance. Hue et al. [15] found that body mass was responsible for more than 50% of balance at speed and Chiari et al. [12] demonstrated a strong correlation between body mass, anteroposterior movements and the area of detachment. McGraw et al. [16] reported that greater postural adjustments are necessary to maintain an erect posture when there is a build-up of adipose tissue, thus causing a reduction in balance and an increase in injuries and falls. Due to the high degree of correlation between balance and body mass, we can safely infer that the mechanical factor of body mass inertia requires greater musculoskeletal force to balance it against the force of gravity, and therefore, to maintain balance, obese individuals require greater movement from the center of gravity to remain in the orthostatic position.

There is a consensus that the greater the height, the worse the balance. Berger et al. [17] and Alonso et al. [3] stated that ankle displacements and the response of the gastrocnemius increased with increasing height. Allard et al. [18] and Lee and Lin [10] reported that tall individuals present greater postural sway than do short individuals, and they attributed this to the higher position of the center of mass. Kejonen et al. [19] and Hue et al. [15] have found that body stability is inversely related to the height of the center of gravity and that, for this reason, posturography

measurements are affected by individuals' anthropometric characteristics.

The architecture of the vertebral column, upper and lower appendages, and organs and tissues that attach to or are suspended from the spinal column affects

**4.4 Role of foot anthropometry in maintaining postural balance**

may also account for the differences.

*DOI: http://dx.doi.org/10.5772/intechopen.92149*

**4.2 Effect of body mass on postural balance**

**4.3 Impact of stature on postural balance**

**147**

where Fy is vertical reaction force, Mg is human total weight, xcop is the center of pressure (COP), xcom is the horizontal component of the center of mass (COM) (e.g., the center of gravity (COG)), I is the moment of inertia of the total body about the ankle joint, and θa is the ankle joint angle [6].

Two basic models for biped locomotion are walking and running. A gait of walking consists of stance and swing phases and a gait of running consists of stance and flight phases. Stance phase describes the period when a foot remains on the ground, and either swing or flight describes the period when a foot does not touch the ground. At midstance, the COM is at its highest point and gravitational potential energy is at maximal and kinetic energy at minimal. The exchange between kinetic and gravitational potential energies is cyclical over gaits. On the other hand, a running leg acts as a spring; therefore, a simple running model is a mass-spring system. At the braking phase during stance, the spring gets compressed and energies are stored as elastic energy. At midstance, the COM reaches its lowest point. The stored elastic energy recoils the spring at propulsive phase during stance to produce kinetic and gravitational potential energies. Both models principally exchange and store energies repeatedly to produce forward thrust and stability [6].

#### **4. Factors affecting postural balance**

Numerous determinants like age, gender and body characteristics like body mass, height and body mass index affect postural stability. Anthropometric parameters of ankle joint and foot also affect bipedal and unipedal postural stability.

#### **4.1 Effect of age and gender on postural balance**

Vijada Raiva et al. [6] stated that females have more postural stability than males. Hageman et al. [7] stated that compared to younger population, older

*Effect of Foot Morphology and Anthropometry on Bipedal Postural Balance DOI: http://dx.doi.org/10.5772/intechopen.92149*

generation showed more tendency to sway. Older adults performed the timed movement task much slower than the younger adults. Longer response times by the elderly have been attributed to slower event detection and impaired sensorimotor integration. Greve et al. [8] stated that women showed less movement on Biodex Balance System than men did, and these findings were similar to those of Rozzi et al. [9] who evaluated basketball and American football players using the same equipment. Lee and Lin [10] studied children and observed that girls presented better postural balance than boys. This could be due to anthropometric factors (greater in men), but other factors such as neuromuscular (flexibility) and neurophysiologic (processing of inferences), as well as the habit of using higher heels, may also account for the differences.

#### **4.2 Effect of body mass on postural balance**

**2. Evolution of bipedal posture**

*Weight Management*

from fall, more energy consumption, etc.

**3. Biomechanics of bipedal posture**

about the ankle joint, and θa is the ankle joint angle [6].

**4. Factors affecting postural balance**

**146**

**4.1 Effect of age and gender on postural balance**

describes human sway motions.

Our ancestors would have probably become extinct if they had not developed their bipedal posture including the corresponding transitional behavioral constraints. "Bipedalism evolved more as a terrestrial feeding posture than as a walking adaptation" [5]. The adapted bipedal posture brought various disadvantages like decreased velocity, increased time for social interaction, more chances of injuries

Advantages of bipedal posture could be many, namely freeing of hands, the visual

advantage of being able to survey the surrounding, ability to acquire the skill of throwing, ability to carry infants while running, ability to reach out for food, ability for carrying food or provisioning, etc. But the most important hypothesis is that the ability to venture into shallow water made the ancestors to adapt bipedal posture.

Upright postural balance describes the dynamics of body posture to prevent falling over a relatively small base of support under gravitational field. As for postural balance without stepping, the stable balancing condition can be analyzed using the following equation under assumption that a one link inverted pendulum

where Fy is vertical reaction force, Mg is human total weight, xcop is the center of pressure (COP), xcom is the horizontal component of the center of mass (COM) (e.g., the center of gravity (COG)), I is the moment of inertia of the total body

Two basic models for biped locomotion are walking and running. A gait of walking consists of stance and swing phases and a gait of running consists of stance and flight phases. Stance phase describes the period when a foot remains on the ground, and either swing or flight describes the period when a foot does not touch the ground. At midstance, the COM is at its highest point and gravitational potential energy is at maximal and kinetic energy at minimal. The exchange between kinetic and gravitational potential energies is cyclical over gaits. On the other hand, a running leg acts as a spring; therefore, a simple running model is a mass-spring system. At the braking phase during stance, the spring gets compressed and energies are stored as elastic energy. At midstance, the COM reaches its lowest point. The stored elastic energy recoils the spring at propulsive phase during stance to produce kinetic and gravitational potential energies. Both models principally exchange and store energies repeatedly to produce forward thrust and stability [6].

Numerous determinants like age, gender and body characteristics like body mass, height and body mass index affect postural stability. Anthropometric parameters of ankle joint and foot also affect bipedal and unipedal postural stability.

Vijada Raiva et al. [6] stated that females have more postural stability than males. Hageman et al. [7] stated that compared to younger population, older

Fy*:*xcop–Mg*:*xcom ¼ I θa*:* (1)

Ledin and Odkvist [11] demonstrated that a 20% increase in body mass reduced the ability to make adjustments in response to external perturbations in the orthostatic position, with a consequent increase in postural instability. Chiari et al. [12] and Molikova et al. [13] in their respective studies conducted on individuals with normal or slightly higher than normal BMI have shown low correlations between body mass and balance. Majority of studies indicate that there was a direct relationship between obesity and increased postural instability, as evaluated by means of various tools and methods. Greve et al. [14] showed that in young adult males, the higher the BMI, the worst the postural balance, needing more postural adjustments to maintain balance in single leg stance. Greve et al. [8] proposed that the male group demonstrated stronger correlations for overall, anteroposterior and mediolateral stability index with body mass index (BMI) compared to women. They stated that there was a need for greater movements to maintain postural balance. Hue et al. [15] found that body mass was responsible for more than 50% of balance at speed and Chiari et al. [12] demonstrated a strong correlation between body mass, anteroposterior movements and the area of detachment. McGraw et al. [16] reported that greater postural adjustments are necessary to maintain an erect posture when there is a build-up of adipose tissue, thus causing a reduction in balance and an increase in injuries and falls. Due to the high degree of correlation between balance and body mass, we can safely infer that the mechanical factor of body mass inertia requires greater musculoskeletal force to balance it against the force of gravity, and therefore, to maintain balance, obese individuals require greater movement from the center of gravity to remain in the orthostatic position.

#### **4.3 Impact of stature on postural balance**

There is a consensus that the greater the height, the worse the balance. Berger et al. [17] and Alonso et al. [3] stated that ankle displacements and the response of the gastrocnemius increased with increasing height. Allard et al. [18] and Lee and Lin [10] reported that tall individuals present greater postural sway than do short individuals, and they attributed this to the higher position of the center of mass. Kejonen et al. [19] and Hue et al. [15] have found that body stability is inversely related to the height of the center of gravity and that, for this reason, posturography measurements are affected by individuals' anthropometric characteristics.

#### **4.4 Role of foot anthropometry in maintaining postural balance**

The architecture of the vertebral column, upper and lower appendages, and organs and tissues that attach to or are suspended from the spinal column affects postural stability. Very few studies are available on correlation of foot parameters with unipedal and bipedal postural balance [18].
