Benefits of Pilates in the Elderly Population: A Systematic Review and Meta-Analysis

The aim of this systematic review is to collect and summarize the benefits of Pilates in the elderly population (>60 years old), within the current scientific production, assessing its contribution to Healthy Ageing (HA). We used PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-analysis) to select, collect, and analyse this thematic. The methodological procedures were registered in the PROSPERO database. The main results of the studies analysed (n = 30) point to significant differences between the intervention and the control groups in dynamic balance, strength, mobility, functional capacity, risk of falling reduction, and mental and psychological health. Thus, the results showed that Pilates may be beneficial for the health of the elderly. The meta-analysis found statistical differences between means on the dynamic balance (mean difference (MD) = −0.0, 95% CI [−0.71, −0.50]; I2: 0%) and the aerobic capacity and aerobic resistance [(MD) = 38.29, 95% CI [6.82, 69.77]; I2: 0%). Thus, it is concluded that the efficacy of Pilates has been shown in various areas of HA and has proven to be affordable and safe for the majority of people, using just a mat on the floor. Future studies should focus on the analysis of the relationship between the cost and the benefit of a Pilates intervention in the elderly population, to better understand how health costs can be minimized and to contribute to a multidisciplinary and generalized HA. Pilates has practical application for the clinicians, therapists, and health professionals that work with the elderly population.


Introduction
The number of people aged 80 years or more will triple and reach 434 million by 2050. On a world scale, the number of people aged over 60 is increasing at a yearly rate of 3%, far higher than the younger age groups. The prediction is that in 2050 the elderly will represent 22% of the population [1]. This demographic evolution has a strong social, political, and economic impact and is an indicator of the social transformation of the 21st century.
Ageing results in molecular and cellular decline, with a progressive influence on all body systems and, inherently, on the person's psychosocial condition [2,3]. Physical activity may help reduce the speed of this decline, raising or maintaining the elder person's intrinsic and functional capacity by improving physical capacities (e.g., strength, balance, and flexibility) [4]. Therefore, physical activity represents one of the factors that may The selection process was conducted according to the following stages: (i) research that used the descriptors in the aforementioned databases; (ii) exclusion of duplicate articles; (iii) reading of abstracts; and (iv) critical reading and assessment of the articles (cf. Figure 1). The selection and extraction of the data from the articles was conducted in two stages. Firstly, two authors (MP, RM) made an independent selection and data collection from the eligible articles. After gathering both selections, the resolution of tie situations was solved in a meeting between both authors. If needed, a third author was called to decide (MC). After this process and the reaching of a consensus higher than 85%, one of the authors (MP) completed the process for the remaining eligible articles. For a review of this nature, the most reliable source is the Random Clinical Experimental Trials (RCTs) [19]. Regardless, evidence from observational or non-randomized trials was equally included, broadening the span of the collection that could guide the intervention of the technicians using the Pilates methods in HA. To keep data quality control and the methodological requisites for this review, we chose to analyse and treat these two categories separately. Finally, the definition of an exclusion criteria of articles written in other idioms is justified by two reasons: the first is due to the fact the difficulty in assessing articles without consulting the full text would skew the data that would result from non-

Eligibility Criteria
The inclusion criteria were the following: (i) published works between 1 January 2016 and 21 April 2021; (ii) works written in English, Portuguese, Spanish, or French; (iii) studies that used the work "Pilates" in the title or in the keywords, with a sample over 60 years of age; (iv) random clinical trials; and (v) studies where Pilates was one of the dependent variables in the experiment. The following criteria were used for exclusion: (i) publications prior to 2016; (ii) publications without full text; (iii) academic theses, books, or non-scientific articles; and (iv) studies where the Pilates method was used along with other interventions or techniques (see Figure 1).
The selection process was conducted according to the following stages: (i) research that used the descriptors in the aforementioned databases; (ii) exclusion of duplicate articles; (iii) reading of abstracts; and (iv) critical reading and assessment of the articles (cf. Figure 1). The selection and extraction of the data from the articles was conducted in two stages. Firstly, two authors (MP, RM) made an independent selection and data collection from the eligible articles. After gathering both selections, the resolution of tie situations was solved in a meeting between both authors. If needed, a third author was called to decide (MC). After this process and the reaching of a consensus higher than 85%, one of the authors (MP) completed the process for the remaining eligible articles. For a review of this nature, the most reliable source is the Random Clinical Experimental Trials (RCTs) [19]. Regardless, evidence from observational or non-randomized trials was equally included, broadening the span of the collection that could guide the intervention of the technicians using the Pilates methods in HA. To keep data quality control and the methodological requisites for this review, we chose to analyse and treat these two categories separately. Finally, the definition of an exclusion criteria of articles written in other idioms is justified by two reasons: the first is due to the fact the difficulty in assessing articles without consulting the full text would skew the data that would result from non-technical translations. The second is due to the fact that this idiom limitation has not changed the conclusions of the systematic reviews made [20].

Quality Assessement
PEDro (Physiotherapy Evidence Database) was used by two authors (M.J.P., R.M.) to independently register the included studies. The PEDro scale can be used in the assessment of the publication bias of the clinical trials [21]. It assesses two aspects of the quality of a clinical trial: (i) credibility, that is, internal validity and (ii) whether the article contains enough statistical information to be interpreted. The first item of the scale assesses the external validity and does not encompass the quantification of the final score. To assess the internal validity, eight criteria were used: (i) random distribution, (ii) secret allocation, (iii) comparison of groups in the beginning, (iv) blind subject, (v) therapist, (vi) evaluators, (vii) analysis by treatment intention, and (viii) complete following period (items 2-9 of the PEDro scale). To assess interpretability, statistical comparisons between the groups were used and, as reported, the (x) precision measurements and the (XI) variability (items 10 and 11 of the PEDro scale). The final score higher than 7 is attributed to a study with "high quality". Between 5 and 6, "moderate quality" is considered. Scores lower than 4 are of "low quality".

Statistical Analysis
This meta-analysis was conducted using the mean and standard deviation of the following variables: static balance, dynamic balance, balance confidence, strength and aerobic capacity, and resistance. All the data were analysed with Review Manager (RevMan, Version 5.4, the Cochrane collaboration, 2020). The data were grouped by random effects, with a confidence interval of 95% (MD95%). Heterogeneity was assessed with an I-squared test. In the case that this value was above 50%, it would be classified as high, and the data would be relativized in the subsequent analysis. No publication bias study was conducted as we did not find more than 10 studies for any specific physical capacity [20].

Results
Of the five databases analysed, a total of 354 entries were considered eligible, according to the following distribution: SportDiscus (n = 31), PEDro (n = 21), PUBMED (n = 68), Web of Science Core Collection (n = 68), and B-ON (n = 166).
For this systematic review, 30 RCT studies were analysed. The remaining ones were non-randomized, and observational studies were included in the qualitative analysis in order to frame the practice and use of Pilates as a means of enhancing HA.

RCT Studies
The PEDro Scale assessment of the 30 studies resulted in 9 of low methodological quality, 14 of moderate quality, and 7 high-quality studies.
Tables 1-5 present the details of the studies analysed in this systematic review.   There was no significant difference in the joint variability of the ankle, knee, and hip joints between the groups, both before training and after training. There was a significant increase in the hip-knee deviation phase value in the MP and this increase was also significant when compared with that in the control group.
The 8-week modified Pilates exercise program can have a positive impact on the gait of elderly participants, potentially by enhancing neuromuscular adjustment, which may have positive implications for reducing their fall risk. These results support use of both Pilates and PNF methods to enhance lower limb muscle strength in older groups, which is very important for gait, postural stability, and performance of daily life activities.  The results of trunk swinging during the "Two-Leg Tandem Stance" with eyes closed, reduction on CoP displacement during the "One leg Stance" and the increase in trunk oscilation in the trunk swinging test for both intervention groups.

5/10
Both programs had a positive effect in the static and dynamic balance-related variables. LD appears to be better for people with rhythm perception and sensorimotor control. On the other hand, Pilates appears to be more effective for people with trunk control problems, as it improves core stability. Pilates combined with technological equipment that allows the analysis, treatment, and training of the pulmonar function showed efficacy in this type of application.  Pilates is effective in the improvement of expiratory muscle strength and presents a positive effect on the increase in the inspiratory muscle strength.    There was a significant increase for the MP and TR groups in the forearm flexion test preand post-intervention. The TR group also showed an increasing the handgrip test, particularly between week 12 and 24.

5/10
Pilates and resistance training contributed to a significant increase in the strength of elderly.

5/10
Of the six studies presented in Table 1, half did not report advantages of the Pilates method per se or in combination with other techniques and interventions [22,27]. The first did not find any evident benefit for trunk strength and balance, whereas the second did not find Pilates to be the most effective method in strength gains or in the transfer of these gains to the functional autonomy of the elderly. In contrast, one study shows a beneficial effect of Pilates in the functional autonomy of the elderly [24]. The remaining studies showed gains in flexibility [23], emotional health [25], balance, and reduction in the risk of falling [26].
The study of Gabizon et al. [28] is the third without evidence of a positive influence of Pilates. To the authors, this may be due to the fact that Pilates is not a specific method for the development of balance. On the other hand, there is the advantage of Pilates in reducing waist perimeter and BMI [30]. In the remaining studies, balance and confidence in balance [32] and improvements in walking ability and in fear of falling, with the corresponding reduction in the risk of falling, were highlighted by some authors [29,31]. Lower limb strength and functional autonomy were also reported as having benefited from Pilates [33].
Regarding this set of studies, lower limb strength improvements were reported [35,36,38]. Balance is also improved with Pilates, particularly for those with deficits in trunk control and trunk stability [37]. Jurakic et al. (2017) showed that Pilates is beneficial for elderly people with short-term memory deficits [34]. Finally, pulmonary function also improves [39].
Balance improvements, reduction in the risk of falling, increase in functional mobility, and postural stability are reported in this set of studies [42,44]. Additionally, improvements in pulmonary function are also reported [43]. Improvements in quality of life, satisfaction with life, and perception of health status were also reported [40,41,45], as well as improvements in functional autonomy [40] and sleep quality [41].
The studies presented a set of results considering the advantages of Pilates in balance [2,3,47] and strength [3,5,47]. One study revealed improvements in functional capacity, walking, and mobility [8]. The same authors also found beneficial effects of Pilates interventions in the cognitive dimension. Advantages in cardiorespiratory fitness were also reported [46].
In summary, 27 of the 30 studies analysed reported advantages of Pilates for the elderly. The areas where more advantages were reported were in static or dynamic balance [3,5,33,35,36,38,39,43,47]. Four studies showed benefits in total strength, three in lower limb strength, and two studies reported benefits in respiratory strength. Functional capacity and functional autonomy also tend to improve with Pilates, according to four studies [8,33,40,42]. The psychological and mental-health-related variables (e.g., perception of health, quality of life, satisfaction with life, emotional health, and sleep quality) also improved significantly with Pilates [25,40,41,45]. In two experimental studies, flexibility was improved [23,42], and two other studies showed improvement in aerobic resistance [38,46]. A decrease in BMI and waist perimeter was also reported [30]. Finally, gains in short-term memory were also reported in cognitively disabled people [34]. Table 6 presents the details of the observational or non-randomized studies included in this review. Pilates helped improve the well-being of the elderly. There was a significant improvement of the functional capacity of the elderly women after the intervention. A short term Mat Pilates protocol, may be an efficient alternative to reduce fall risk in the elderly population. Both protocols appear to be safe and efficient for normotensive elderly women.  Pilates exercise is beneficial exercise to improve gait, muscle strength, and mobility in communitydwelling older women. This section included 14 studies with similar benefits being reported, despite different methodologies used. Two studies show that Pilates is not the most effective intervention to control blood pressure, glycaemia [57], and the sensory regulation of static or dynamic balance [58]. The remaining studies, however, report gains in strength [48,53,59] and improvements in the functional capacity and mobility of the elderly [52,59,60]. Psychological variables, such as self-resilience [49], well-being [50], quality of life [54], or health-related psychological variables [9], benefited with Pilates interventions. Additionally, improvements in walking ability [59], haemodynamic behaviour [56], fall-risk reduction [55], and salivary S-IgA [51] were mentioned once.
Eur. J. Investig. Health Psychol. Educ. 2022, 12, x FOR PEER REVIEW 21 The results of the meta-analysis calculated for the OLS show a mean difference of 3.33 s between groups, without statistical significance (95% CI: [−0.27, 6.94]; I 2 : 0%) (Figure 2). For the global analysis of dynamic balance capacity, a significant difference in the mean difference was found between the Pilates and the control groups, with a value of −0.60 s (95% CI: [−0.71, −0.50]; I 2 : 0%) with an advantage for the first group ( Figure 3).  For the global analysis of dynamic balance capacity, a significant difference in the mean difference was found between the Pilates and the control groups, with a value of −0.60 s (95% CI: [−0.71, −0.50]; I 2 : 0%) with an advantage for the first group ( Figure 3).
The three studies that assessed confidence in balance using the ABC Scale [8,29,42]  For the global analysis of dynamic balance capacity, a significant difference in the mean difference was found between the Pilates and the control groups, with a value of −0.60 s (95% CI: [−0.71, −0.50]; I 2 : 0%) with an advantage for the first group (Figure 3). The three studies that assessed confidence in balance using the ABC Scale [8,29,42] point to the absence of a significant mean difference between the groups (3.65; 95% CI: [−1. 50,8.79]; I 2 : 0%) (Figure 4).

Aerobic Capacity and Aerobic Resistance
The 6 min walk test allows the assessment of aerobic capacity and aerobic resistance. From the studies analysed [3,5,24,27], statistically significant differences were found in the mean difference to complete the test: 38,29 m plus to the Pilates group (95% CI: [6.82, 69.77]; I 2 : 0%). The data from Lima et al., 2021, were not included in the metaanalysis due to their heterogeneity ( Figure 6).

Aerobic Capacity and Aerobic Resistance
The 6 min walk test allows the assessment of aerobic capacity and aerobic resistance. From the studies analysed [3,5,24,27], statistically significant differences were found in the mean difference to complete the test: 38,29 m plus to the Pilates group (95% CI: [6.82, 69.77]; I 2 : 0%). The data from Lima et al., 2021, were not included in the metaanalysis due to their heterogeneity ( Figure 6).

Aerobic Capacity and Aerobic Resistance
The 6 min walk test allows the assessment of aerobic capacity and aerobic resistance. From the studies analysed [3,5,24,27], statistically significant differences were found in the mean difference to complete the test: 38,29 m plus to the Pilates group (95% CI: [6.82, 69.77]; I 2 : 0%). The data from Lima et al., 2021, were not included in the meta-analysis due to their heterogeneity ( Figure 6).

Aerobic Capacity and Aerobic Resistance
The 6 min walk test allows the assessment of aerobic capacity and aerobic resistance. From the studies analysed [3,5,24,27], statistically significant differences were found in the mean difference to complete the test: 38,29 m plus to the Pilates group (95% CI: [6.82, 69.77]; I 2 : 0%). The data from Lima et al., 2021, were not included in the metaanalysis due to their heterogeneity ( Figure 6).

Discussion
The aim of this systematic revision is to collect and summarize the benefits of Pilates in the elderly population, within the current scientific production, assessing its contribution to Healthy Ageing (HA). In the first place, due to the state of the art and our findings, we could verify that the Pilates method has gained adepts over the last years. The increase in the elderly population is a fact and with it is the need to find processes that enable HA. Therefore, it is important to confirm the benefits of Pilates and scientifically validate them. The multiplication of the adaptations of this method, according to the current know-how or in order to meet the goals of the practice, has diversified the

Discussion
The aim of this systematic revision is to collect and summarize the benefits of Pilates in the elderly population, within the current scientific production, assessing its contribution to Healthy Ageing (HA). In the first place, due to the state of the art and our findings, we could verify that the Pilates method has gained adepts over the last years. The increase in the elderly population is a fact and with it is the need to find processes that enable HA. Therefore, it is important to confirm the benefits of Pilates and scientifically validate them. The multiplication of the adaptations of this method, according to the current know-how or in order to meet the goals of the practice, has diversified the exercises and the reach of this method. A great example of this is the use of Pilates apparatuses that appear to point to differences between mat and apparatuses [61,62].
The use of springs and the consequent external load that they impose, along with the number of exercises made in an orthostatic position in these apparatuses may influence the results obtained. Similarly, the systematization difficulties and lack of consensus around the techniques and assessment instruments for the physical capabilities, among others, has resulted in a variability that creates difficulties in extrapolating and comparing the results and conclusions [63].
The results appear to show a robust tendency towards the benefits of Pilates for the elderly population. The analysis also points to a total absence of risks or contraindications of this method. Additionally, the benefits of this method are reinforced by the broad cultural and ethnic scope of the studies analysed, reducing any eventual contextual influence in the benefits presented.
Nevertheless, it is not clear that the Pilates method alone or in combination with other techniques and interventions [22,27] points to a robust tendency of the benefits of Pilates for the elder population. Still, it is important to emphasise the benefits of Pilates in the functional autonomy of the elderly [24], namely in flexibility [23], emotional health [25], and reduction in the risk of falling [26]. Moreover, there is an advantage of Pilates in reducing waist perimeter and BMI [30] and in improvements in walking ability [29,31,32]. Furthermore, the results also indicate that lower limb strength and functional autonomy were also reported as having benefited from Pilates [33].
Similarly, Jurakic et al. (2017) consider that Pilates has benefits for the elderly with short-term memory deficits [34] and that pulmonary function also improves [39]. In this context, improvements in quality of life, satisfaction with life, and perception of health status were also reported [40,41,45], as well as improvements in functional autonomy [40] and sleep quality [41]. Additionally, the results also showed the advantages of Pilates in balance [2,3,47], strength [3,5,47], improvements in functional capacity, walking and mobility [8], and in the cognitive dimension and cardiorespiratory function [46].
In a broader perspective, we emphasise that 27 of the 30 studies analysed reported the advantages of Pilates for the elderly. Standing out are the advantages in total strength, lower limb strength, functional capacity and functional autonomy [8,33,40,42]. Verified too are significant gains in psychological and mental health-related variables, in particular: perception of health, quality of life, satisfaction with life, emotional health [25,40,41,45], flexibility [23,42], aerobic resistance [38,46], waist perimeter [30]. Finally, advantages were also found for people with cognitive impairment [34].
Although the results point out that Pilates is not the most effective intervention to control blood pressure, glycaemia [57], and the sensory regulation of static or dynamic balance [58], we could not, however, fail to highlight the positive effects of Pilates on strength [48,53,59], improvements in the functional capacity and mobility of the elderly [52,59,60], and in psychological variables such as self-resilience [49] and wellbeing [50]. Furthermore, improvements in haemodynamic behaviour [56] and salivary S-IgA [51] were also mentioned in the systematic review of the studies.
Moreover, the meta-analysis shows some results that are consistent with the previous systematic reviews and meta-analysis regarding the benefits of Pilates for the elderly [10,15,16,63]. All the demonstrated advantages of this practice for the development of static and dynamic balance show some consistency and robustness in the results. Regarding aerobic capacity and resistance, the results are consistent with the meta-analysis of Bueno et al. (2018).
The main limitations of this review were the time limitation and the exclusion of information regarding other studies (e.g., books, magazines, or theses). Regarding the studies included in our analysis, the limitations are related to the clinical and methodological variability. Additionally, the high number of studies in which the control group did not suffer any type of intervention may condition the results, namely when calculating a more robust meta-analysis. Most of the studies had a sample composed mainly of women, which may also limit the analysis and interpretation of the results. Therefore, it is important to increase the research in this field, particularly with greater and more gender-balanced samples. Moreover, the protocols should be more standardized in order to better compare the results obtained. Future studies should focus on the analysis of the relationship between the cost and benefit of a Pilates intervention in the elderly population, to better understand how health costs can be minimized and to contribute to a multidisciplinary and generalized HA. Moreover, future systematic reviews may analyse which type of psychomotor responses are associated with the eventual neuromuscular benefits that may come from a Pilates intervention in the elderly population.

Conclusions
This review of studies shows a robust tendency towards the benefits of Pilates in physical capacity and in dynamic balance. The results also show that Pilates may be beneficial for the health of the elderly, contributing to HA that may slow down and fight the degenerative processes associated with senescence. It is also concluded that the efficacy of Pilates has been studied in various areas of HA and has proven to be affordable and safe for the majority of people, using just a mat on the floor. This way, clinicians, therapists, and exercise professionals that work with the elderly population may find in Pilates a viable strategy towards healthy ageing. The well-being improvements in the elderly are enabled by an association between the social and the physical components of practising Pilates, thus contributing to a healthier and more active ageing. Funding: This work is funded by FCT/MCTES through national funds and when applicable cofunded EU funds under the project UIDB/50008/2020.

Institutional Review Board Statement:
The study was conducted according to the guidelines of the Declaration of Helsinki and approved by the Ethics Committee of Polytechnic Institute of Coimbra (Approval number: 82_CEPC2/2021).

Data Availability Statement:
The data presented in this study are available on request by the corresponding author.