# Sleep Quality in Older Women: Effects of a Vibration Training Program
## 1 Introduction  
Sleep is a state of physiological rest characterised by its periodicity and reversibility. It is considered an important phenomenon to restore the body both physically and emotionally [1], providing balance in the person. The sleep pattern of each individual differs enormously from that of others, either by duration or structure, throughout the day; in addition, other factors can decisively influence its quality, such as level of economic status, place of residence, nutrition, and sedentary lifestyle [2]. Researchshows that a healthy diet rich in fruits, vegetables, and olive oil improves the quality of sleep in older adults [3; 4; 5]. Other factors, such as stress or psychosocial factors, can also have a great influence on sleep [6; 7; 8]. With ageing, this pattern changes in a special way, not affecting the total sleep time, but by being interrupted and more distributed throughout the day [1]. It has been proven that adequate sleep at night is one of the main requirements of the elderly to maintain an active and healthy lifestyle [9]. [PERSON] et al. [10] found that there is a 54% prevalence of poor sleep quality in those over 65 years of age, indicating that more than a third of older people have sleep problems and up to a quarter have serious difficulties. According to the American Psychiatric Association [11], chronic sleep disturbance is a risk factor for the subsequent onset of anxiety and mood disorders. Additionally, a recent study by [PERSON] et al. [12] associated anxiety, coupled with poor sleep quality, with the risk of falls and joint problems in women over 60 years of age. Few people seek help with their sleeping difficulties and those who do often seek help after years of experiencing discomfort from this situation [13]. In this sense, there has been a complex debate since the same authors indicate that there are people without real impairment who complain of sleep problems and another group of people with true signs and symptoms who do not report their rest-related disorders. Physical exercise, as a nonpharmacological intervention, can be an effective strategy with which to improve the quality of sleep. Specifically, it has been shown that replacing a sedentary lifestyle with light-intensity exercise could have long-term benefits on the quality of sleep in older people [14; 15]. The benefits of different forms of physical exercise on the quality of sleep have been demonstrated [16; 17; 18]. Likewise, the regular practice of exercise seems to be a protective factor of cognitive function, with the quality of sleep being a decisive factor in reducing the symptoms of depression [19]. Similarly, physical exercise and quality of sleep have consistently been associated with quality of life in clinical and nonclinical populations. However, the mechanisms underlying this relationship are not well understood. What is known is that sleep quality directly influences the quality of life through physical, mental and social wellbeing and that physical exercise also indirectly predicts quality of life and quality of sleep [20]. An option that, for some years, has been introduced with the aim of improving the physical performance of both athletes and sensitive populations is vibration training, also called whole body vibration (WBV). The mechanical stimulus that this vibration transmits, through oscillatory movements, increases the gravitational load to which the neuromuscular system is subjected. Although parameters such as duration of application, frequency, and wave amplitude are important, they must be taken into account according to the functional capacity of each person [21]. [PERSON] et al. [22] indicated that the vibration increases the feeling of relaxation after its performance. Various studies have indicated that WBV can produce positive effects in different age groups.