PSYCHO-PHYSIOLOGICAL PARAMETERS INFLUENCING HEALTHY AGING IN ELDERLY WOMEN

This thesis describes the results obtained from different studies evaluating treadmill walking in younger and older women, in order to study the influence of gait stability, evaluated through gait variability, on physical activity level maintained in daily living and the influence of energy cost of walking and health-related physical fitness qualities on gait speed and gait variability. Moreover, the manuscript describes the different effects of physical activity levels calculated as overall physical activity or accumulated in bouts of at least 10 min and physical fitness on health related quality of life in the same population. 21 young adults (YA: age 22.6±2.9 yrs; BMI 22.5±2.6 kgm-2) and 21 older adults (OA: age 68.3±3.3 yrs; BMI 26.1±3 kgm-2) were recruited. A kinematic analysis was performed with an optoelectronic system to calculate gait variability during treadmill walking at different speeds. Simultaneously, the net cost of walking was analysed with indirect calorimetry and calculated subtracting resting metabolic rate measured during standing from gross metabolic rate. To provide an accurate estimation of physical activity level during free- living activities, the subjects worn an activity monitor for almost 7 complete and consecutive days, inferring time spent in sedentary, light, moderate or vigorous physical activity. Skinfold thickness was measured to obtain body fat. Cardiorespiratory fitness was determined by indirect calorimetry using a maximal treadmill test. Isometric maximal voluntary contraction was evaluated on a horizontal leg press, and by hand-grip strength. Flexibility was assessed by V Sit & Reach test. Gait speed, defined as the preferred walking speed of the subject, was measured as the time taken to walk the middle 10m of 14m. To assess maximal isometric strength, they performed a hand-grip strength test. Health-related quality of life was measured with the Short-Form 36 Health Status Survey (v2) that provided the physical and the mental component summary score. The main findings of this study were that: (i) a good gait stability and a high preferred walking speed seem to be able to ensure elevated levels of physical activity in healthy older women; (ii) the energy cost of walking was influenced by the speed but did not influence gait speed at any of the analysed speeds; (iii) a significant association was found only between hand-grip strength and gait stability; (iv) there was a positive relationship between the level of cardiorespiratory fitness and the physical component summary of health-related quality of life; (v) there was a positive relationship between the level of physical activity (both overall physical activity and accumulated in bouts of at least 10 min) and physical functioning; (vi) there was a negative relationship between sedentary time and vitality and role-emotional; (vii) physical activity and physical fitness did not influence the mental component summary. The present results showed that in healthy elderly women, a good gait stability and a high preferred walking speed seem to be able to ensure elevated level of PA. Moreover, the net cost of walking is not affected by age allowing a high preferred walking speed and an elevated level of physical activity. Even if almost all the population met current physical activity recommendations, accumulating a minimum of 30 min of daily moderate physical activity in bouts of 10 min or more, the significant difference between MVPAall and MVPA10 has to be taken into consideration when tailored intervention for the elderly population has to be provided.