The effect of dual-task walking on intra-organ harmony in young and elderly people with and without a history of falling

Doctoral Dissertation

To obtain a specialized doctorate degree in the field of physiotherapy

Abstract

The purpose of this study was to investigate the effect of cognitive load and walking speed on the variability and dynamics of intra-organ synchrony phase in young and elderly people with and without a history of falling. 30 young people and 32 elderly people (20 elderly people with a history of falling and 12 elderly people without a history of falling) participated in this study. They were asked to perform nine tasks of walking on a treadmill including walking at slow, arbitrary and slow speeds individually or together with one of the cognitive tasks of counting backwards or subtracting three from a random three-digit number. The values ??of the deviation phase and the absolute mean of the relative phase were calculated for each of these conditions, which respectively expressed the variability and dynamics of the intra-organ harmony phase. Three-way analysis of variance test was used to investigate the effect of the mentioned factors on walking parameters. The results showed that the main effect of group and walking speed on the phase of synchronous deviation between hip-thigh, thigh-leg and leg-foot segments was significant (p<0.01), while the effect of cognitive load was significant only on the phase of synchronous deviation between leg-foot segments. Also, the main effect of the group on the absolute average of the relative phase on the relations between the hip-thigh, thigh-leg and leg-foot segments was significant (p<0.01), while the walking speed had a significant effect on the absolute average of the relative phase on the relationships between the hip-thigh and thigh-leg segments (p<0.01). Our results showed that old age can increase intra-organ synchrony variability while falling, adding cognitive load and increasing walking speed reduce this variability. In addition, falls and difficult walking conditions drive the synchronization dynamics to become more out of phase, which is thought to be a mechanism to reduce the control effort by the controller system. style="direction: rtl;">

1-1 Aging

Aging is a part of the biological process that includes all living beings, including humans. From the point of view of biology, aging is the biological changes that appear in the way of life of a living organism over time. This change is accompanied by a decrease in the capacity of the person to adapt to sudden conditions and the inability to re-establish balance, and it gradually causes changes in the structure and function of various organs of the person's body (1-2). Demographers determine the beginning of old age and old age based on age groups. This division is usually done in two ways. First, the age groups of 0-9, 10-59, and 60 years and above; Second age groups 0-14, 16-64, and 65 years and above. According to the aforementioned groupings, the ages of 60 and 65 are considered the beginning of old age. Although in advanced countries, due to the increase in life expectancy, the second criterion, 65 years old, has been set as the starting age of old age, but since the World Health Organization has a general view of all countries, it considers old age to be 60 years and above (3-5). Population aging is a process known as the consequence of the "demographic transition" in which fertility and mortality decline from high levels to low levels. The most important factors affecting the aging of the population are the decrease in mortality, the fundamental and continuous decrease in fertility, and consequently the decrease in population growth, the increase in life expectancy and the level of health and treatment, which has caused fundamental changes in the age structure of the population of most societies, including Iran (2-3, 5). The next year will significantly advance towards old age. Every year, the world population increases by 1.7%, but this increase is 2.5% for the population of 65 years and older. This distance leads the age composition of the world's population towards aging and it is predicted that the elderly population will grow from 16 to 28 percent of the total population by 2050. Our country, Iran, has not been spared from this demographic change.Along with the growth of the world's elderly population, Iran's population is also moving towards old age in such a way that it is predicted that by 1405, Iran's elderly will make up about 11% of the country's total population (8). Statistical indicators show that the process of population aging has started in our country, and it is predicted that the average age of the country's population will increase by 10 years in the 20-year period from 1340 to 1405. The statistics and figures obtained from the general housing population census show that the number of elderly people in Iran has been increasing in recent decades, and the ratio of the country's elderly population between 1335 and 1385 has not been uniform. Iran's elderly population (aged 60 and over) increased from 1,173,679 people in 1335 to 5,121,038 people in 1385. In other words, the elderly population of the country increased by 4.4 times during the 50-year period, while the total population of the country increased by 3.7 times during the same period. It is obvious that one of the effective factors in the increase of the elderly population in 2015 was the increase in life expectancy and the decrease in the fertility level in the last two decades. It is predicted that between 1375 and 1404, the elderly population in Iran will increase from 67.6% of the total population to about 11% (1, 5).

According to the documents of the World Health Organization, the elderly are divided into three age groups: 60 to 69 years old, 70 to 79 years old, and Over 80 years old are divided into "elderly elderly" (3). The ratio of the percentage of the elderly, elderly elderly and older elderly to the total elderly in 1335 was equal to 62, 26.5 and 11.5 percent, respectively, in 1345 equal to 62.27 and 11 percent, in 1355 equal to 53, 33 and 14 percent, in 1365 equal to 65.5, 20.5 and 14 percent, in the year 1375 was equal to 62, 30 and 8 percent, and in 1385 it was equal to 52, 35.5 and 12.5 percent.  In the 10-year period from 1375 to 1385, the population of 60 years and older grew by 2.5% per year, while the age group of 70 years and older grew by 5% and the age group of 80 years and older grew by 8%. Also, due to the increase in life expectancy during 1375-85, the growth of the population of the elderly 70 years and older compared to the elderly 60 years and older, and the growth of the population of the elderly 80 years and older compared to the elderly 70 years and older has been higher. As can be seen, a significant point in this process is the aging of the elderly population. For most countries, especially Iran, regardless of the geographical location or development stage, the age group of 80 years and older has a higher growth rate than the younger age groups of the elderly. Figure 1-2 shows the age pyramid of Iran's population in the years 1995, 2000, and the forecast for 2025 and 2050, respectively, comparing these images well shows the aging process in our country (1, 5). rtl;"> 

Abstract:

Knowledge about Intra-limb coordination (ILC) during challenging walking conditions provides insight into the adaptability of central nervous system (CNS) for controlling human gait. We assessed the effects of cognitive load and speed on the variability and phase dynamics of ILC in young people and faller and non-faller older adults during walking. Thirty healthy young, twenty non-faller and 12 faller people participated in this study. They were asked to perform 9 walking trials on a treadmill, including walking at three paces (preferred, slower and faster) either without a cognitive task (single-task walking) or while counting backwards or subtracting 3's from a random three-digit number (simple and complex dual-task walking, respectively). Deviation phase (DP) and mean absolute relative phase (MARP) values ??-indicators of variability and dynamic phase of ILC, respectively- were calculated using the data collected by a motion capture system. We used a three-way analysis of variances for statistical analysis. The results showed that the main effects of group and walking speed were significant on pelvis-thigh, thigh-shank and shank-foot DPs, while the main effect of cognitive load was only significant on shank-foot DP (p<0.01).