The current rate of aging population will be a challenge for health systems in the coming years. In 2030, it is expected that older adults (≥60 years old) will represent 12% of the world’s population, this value will increase to 16% by 2050 (United Nations, 2019). In Spain, values above 25% are expected to be reached by 2033 (Instituto Nacional de Estadística, 2018). Physical activity (PA) plays a very important role in the prevention of chronic diseases in older adults (i.e., cardiovascular diseases, metabolic diseases, musculoskeletal disorders, and cancer) (Warburton and Bredin, 2017). Physical activity is a key part in any healthy aging lifestyle (Cartee et al., 2016). The World Health Organization (WHO) recommends that older adults should engage in 150–300 min/week of at least moderate-intensity activities and muscle strengthening activity twice weekly (Bull et al., 2020). Despite the many health benefits of regular PA, few older adults meet the recommended guidelines (Bauman et al., 2016).

Long periods of inactivity or sedentary lifestyle in older adults population lead to deconditioning which involves a main decrease in muscle mass, with the consequent decrease in strength/endurance and aerobic capacity (Kortebein, 2009). On the other hand, an age-related progressive decrease in muscle mass (Mitchell et al., 2012) and an gradual increase in body fat percentage has been observed (Imboden et al., 2017; Westerterp, 2018). This term has been named sarcopenic obesity (Choi, 2016). Older adults with sarcopenic obesity tend to a functional decline (Kohara, 2014) and this fact can lead to a lower adherence to PA programs. The good news are that regular PA and/or exercise have positive effects in older adults such as: increases muscle mass and muscle function (Beaudart et al., 2017; Westerterp, 2018), and consequently maintains or increases their physical fitness (Milanović et al., 2013) and helps to maintain functional capacity and independence (Mazzeo and Tanaka, 2001). Therefore, it is not only important to motivate older adults to start an exercise program but to make sure they maintain it. So, to understand why people dropout PA and exercise programs and the factors involved in this process, seems crucial to develop tailored interventions that are sustained over time for older adults, focused on PA and exercise.

Behavioral theories help us to understand and predict behavior change in the population (Chase, 2015; Gourlan et al., 2016). Theory-based interventions on PA behavior based on a single theory have shown to be more effective than those based on a combination of theories (Gourlan et al., 2016). One of the most widely used and successful theories/models in promoting PA behaviors is Transtheoretical Model of Change (TTM; Gourlan et al., 2016). Initially it was used in studies to tobacco cessation, but over time its use has extended to promote healthy habits including the practice of PA. A recent review (Jiménez-Zazo et al., 2020) has presented the benefits of using TTM for PA in older adults.

The TTM was proposed by Prochaska and DiClemente (1983), is composed mainly by four constructs: stages of change (SoC), processes of change, decisional balance and self-efficacy, this model assumes that behavior change is a dynamic process, which occurs through a temporal dimension in a sequence of stages and processes, by which the individual moves until reaching regular behavior (Prochaska and DiClemente, 1983). The SoC, are part of the core of this model. SoC are a descriptive construct that explain where the people are in their motivation to change and their current behavior change (Romain et al., 2018). The SoC are composed of five stages: Precontemplation, contemplation, preparation, action, and maintenance. The SoC categorize individuals from non-intentional to change (precontemplation) to the acquisition of a regular behavior after 6 months (maintenance) (Prochaska and DiClemente, 1983).

Therefore, understanding the SoC to regular PA in older adults and to relate it to their changes in body composition and physical fitness overtime can help to identify the factors that determine the drop out of regular PA in this population. Under this umbrella, the Spanish network of research in exercise and health for special populations (EXERNET), conducted the Longitudinal elderly EXERNET study, it was the first study measured functional fitness in independent non-institutionalized Spanish older adults population, from 2008–2009 to 2017–2018 (Gomez-Bruton et al., 2020) which also measured the SoC for PA. Therefore, our study aim was to study the evolution of behavior change for PA through SoC after 8 years and, to identify the associated factors related to the worsening of SoC for PA.

The evolution of the SoC between periods 2008 and 2009 up to 2017 and 2018 together with the relationship between body composition and physical fitness (at baseline) with worsening SoC, are presented in Tables 1, 2.

This article has identified the correlates of decreasing PA practice in a sample of 714 Spanish older adults (>65 years) in a 8-years follow-up period (2008–2009 to 2017–2018). A higher HC, lower fitness levels in lower body strength and aerobic endurance at the 6 min-walk test at baseline, were related to decreasing PA and becoming sedentary in Spanish older adults after 8 years.

The study has used the SoC to identify the status of active versus non-active behavior in older adults. The popularity of the SoC lays on the possibility of tailoring interventions to individuals undergoing different SoC. This study takes a former step to determine how physical fitness and anthropometric variables can predict the change from active to inactive stages after a period of 8 years. Identifying the determinants of the worsening process of SoC for PA, will help to focus on tailored intervention exercise programs with the goal of reducing older adults’ drop-outs rates.

Our results have shown as a high HC at the baseline was correlated to decreasing PA practice in Spanish older adults after a period of 8 years. Changes in body composition, such as increased body fat and losses in skeletal muscle mass represent important risk factors for the incidence of cardiometabolic diseases such as hypertension, dyslipidemia, and type II diabetes mellitus in older adults (Sillanpää et al., 2008). In Spain, EXERNET multi-center study (Gomez-Cabello et al., 2011) found that more than 84% of older adults over 65 years had problems with their body weight (46.7% overweight and 36.7% obese), the correlation between increasing fat mass and decreasing PA in the older adults, is like a snake biting its own tail. An old person who increases body fat can drop PA and dropping PA can lead to an increase in percentage of body fat. More efforts are needed to control diet (calorie ingestion control) and exercise (caloric expenditure control) interventions, that target the maintenance and improvements of older adults anthropometric and body composition.

In regard to physical fitness, lower body strength and aerobic endurance, have been identified as determinant for decrease PA practice in older adults. It has been reported that the process of aging dramatically impacts functional abilities, such as sit-to-stand, gait, and stair climbing abilities (Reid and Fielding, 2012; Müller et al., 2021), mainly related to muscle power declines observed during the aging process (Izquierdo et al., 1999; Müller et al., 2021). Our results have identified older adults’ lower results in the chair-stand test and lower distance in the aerobic endurance 6-min walk test, as predictors to a decrease in their PA practice over a period of 8 years. Lower limb muscle power decreased progressively with age in both men and women (Alcazar et al., 2020), which leads to a decrease in muscle function, affecting to physical function and gait speed (Suetta et al., 2019). Resistance training can increase range of motion of a number of joints of inactive older individuals possibly due to an improvement in muscle strength (Fatouros et al., 2002). Our results show that there are no differences in upper body flexibility and right lower flexibility between older adults who worsened their SoC for PA and the ones who did not. Future exercise programs should focus on improving functional capacity by promoting lower limb strength work with the aim of achieving maintenance and independence in basic activities of daily living in older adults.

Older adults exercise programs that focus on lower limb and all body strength training in general, are important to promote adherence to PA (Kathleen and Adrienne, 2001). Moreover, a benefit in muscle mass will make older adults more efficient metabolically during given activities of daily living and therefore improving endurance capacity to the same given effort, i.e., walking faster.

Currently, there are many exercise programs for the older adults (Cadore et al., 2013), recently the VIVIFRAIL Project¹ as a multicomponent individualized exercise program recognized by the Ministry of Health in Spain, includes progressive cardiovascular, resistance exercise and balance with the aim of improving the functional capacity of older people, i.e., improvement of the rate of falls, gait ability, balance, and strength performance (Izquierdo, 2019). It seems necessary to implement these kinds of programs in society to diminish PA practice decline, although it could be a much interesting option the supervised and individualized exercise programs as Eelder-fit to maximize training benefits in pre- and frail older adults (Moradell et al., 2020).

Older adults group (>65 years) is a very heterogeneous group, so it may have specific characteristics that require different strategies from other age groups. Within our research we have been able to identify the most relevant and predictive aspects related to the worsening of behavior change referred to the practice of regular PA in this group. Exercise programs that are focused on favorable changes in anthropometric and body composition, increasing fitness levels in lower body strength and aerobic endurance are encouraged.

Our study has different limitations, the sample only includes independent non-institutionalized older adults, generally from civic and sports centers, so the results must be interpreted with caution, since it may be a bias for the extrapolation of these results to other groups of older population. This study did not take into account other factors which could lead to a dropout from PA in older adults as age, race (Caucasian), poorer level of physical function, being physically less active, lack of time, family reconciliation, health problems, low levels of motivation and self-efficacy, perceived barriers, lack of knowledge about the benefits of PA, lack of social support, weather, as well as the environment and the possibilities it generates to be physically active (Resnick and Spellbring, 2000; Schutzer and Graves, 2004; O’Shea et al., 2007; Gillette et al., 2015; Kassavou et al., 2015; Geirsdottir et al., 2017). However, we have several strengths, firstly, this is a prospective 8-year follow-up study with a good sample size (n = 714), the age of the participants (>65 years), and the variability of the tests carried out within the study.

In a 8-year follow-up (2008–2009 to 2017–2018) study of 714 independent non-institutionalized older adults, the worsening of SoC for PA was associated with high HC, low body strength and low aerobic endurance at baseline. This study highlights that we need to identify adults with high HC, lower body strength and lower aerobic endurance to design a tailored PA program. Identifying the determinants of losing adherence to PA will help in the creation, design, and evaluation of exercise programs with the goal of reducing older adults’ drop-outs rates. Exercise programs that are focused on favorable changes in anthropometric and body composition, increasing fitness levels in lower body strength and aerobic endurance are encouraged.

The raw data supporting the conclusions of this article will be made available by the authors, without undue reservation.

The studies involving human participants were reviewed and approved by the Research Ethics Committees of Aragón (Spain) (18/2008). The patients/participants provided their written informed consent to participate in this study.

FJ-Z and SA: conceptualization and writing – original draft preparation. JP-G, IA, JC, GV-R, MG-G, and SA: methodology and project administration. FJ-Z, AH-M, and SA: formal analysis and statistical analysis. FJ-Z, CR-B, EC, JP-G, IA, JC, GV-R, EG, MG-G, and SA: investigation and data curation. FJ-Z, CR-B, EC, JP-G, IA, JC, GV-R, MG-G, and SA: resources. FJ-Z, AH-M, CR-B, EC, JP-G, IA, JC, GV-R, EG, MG-G, and SA: writing – review and editing, visualization, and supervision. FJ-Z, JP-G, IA, JC, GV-R, MG-G, and SA: funding acquisition. All authors have read and approved the final version of the manuscript, and agreed with the order of presentation of the authors.

The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

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