Background
Aging is a natural process that includes a dynamic and irreversible decline in physiological function, usually associated with an increase in the manifestation of chronic degenerative diseases [
1]. Pain can be characterized as an unpleasant, sensitive, and emotional experience, associated or not with actual or potential tissue damage [
2]. With aging, the global prevalence of chronic pain increases, and in 50 to 75% of cases, it may be underdiagnosed or undertreated [
3].
Musculoskeletal pain is one of the main types of chronic pain in older adults [
4], affecting approximately 50% of community-dwelling older adults [
5]. Chronic musculoskeletal pain is one of the main causes of disability in older adults and is associated with difficulties with mobility and daily activities. It affects more women than men and generates high socioeconomic costs [
4,
6,
7]. A systematic review indicated that older adults with chronic musculoskeletal pain are less active and may present with disability combined with poor mobility, frailty, depression, cognitive impairment, falls, and poor quality of sleep [
4]. Changes in the pain signal associated with aging include a decrease in the integrity and density of cellular elements in the peripheral nervous system, leading to loss of nociceptive function [
8,
9]. In the central nervous system, there is a reduction in the neurotransmission paths, affecting the adequate transmission of the pain signal and its neuromodulation [
9,
10]. In addition, a systematic review with meta-analysis suggests that older adults tend to have greater intolerance to pain and an increased perception of pain [
11].
The treatment of chronic musculoskeletal pain in older adults involves pharmacological and non-pharmacological interventions [
12]. Due to the short- and long-term side effects of medication, the non-pharmacological approach has been gaining prominence [
9]. Among non-pharmacological interventions, physical exercise is an option, with the objective of preserving the functional independence and quality of life of older adults [
9]. Exercise interventions for older adults with chronic musculoskeletal pain should meet the needs of each patient, and should consider their preferences for type and mode of exercise [
13].
Regular physical exercise has a protective effect on cardiovascular changes, depressive symptoms, and physical disuse in older adults [
14,
15]. In addition, it may limit the development and progression of disabling conditions [
15], such as chronic musculoskeletal pain. In the USA, the Centers for Disease Control and Prevention recommend that older adults perform strengthening exercises and aerobic activities to reduce the risk of mortality [
16]. Aerobic exercise for 30 to 40 min stimulates the production of endorphins, which bind to opioid receptors in the pain control system of the brain and spinal cord to decrease the perception of pain [
17]. To date, only one systematic review has been published [
18] with the objective of verifying the effects of walking in patients with chronic musculoskeletal pain. Improvements in pain and short-term function were observed; however, this systematic review did not include other modalities of aerobic exercise and the results are not specific for older adults [
18]. Thus, no systematic review has verified the effects of different types of aerobic exercise in the treatment of older adults with chronic musculoskeletal pain. Therefore, the objective of this study is to assess the effect of aerobic exercise on pain and function in older adults with chronic pain caused by different musculoskeletal conditions.
Discussion
This systematic review aims to summarize the available evidence on the studies that verified the effects of aerobic exercise in improving chronic musculoskeletal pain in older adults. So far, we are unaware of any similar published systematic review. To obtain a high-quality study, we will follow all the recommendations of the Cochrane Handbook of Systematic Reviews. Primary outcomes were chosen taking into account their importance in the assessment of chronic musculoskeletal pain in older adults, so that the results of this review can easily be compared or combined with those of other systematic reviews on the treatment of chronic musculoskeletal pain. The results of this systematic review will inform physical therapists and other health professionals, as well as patients, about the value of an intervention based on aerobic exercise, given that it is an affordable, low-cost intervention commonly used by the general population. In addition, this study can identify gaps in the literature and guide future studies.
Ethics and dissemination
This study was registered prospectively, and the results will form part of a doctoral thesis and will be published in a peer-reviewed international journal and presented at international conferences.
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