2.1. Selection criteria

2.2. Search strategy

The electronic databases of the Cochrane Library, PubMed, Embase, Web of Science, Google Scholar, MEDLINE, and CINAHL were searched to identify articles that met the inclusion criteria. The search period was from the establishment of the database to December 31, 2022. When searching the database, the retrieval method of combining subject words and free words was adopted. The following keywords were used in the database search: aged, aging, age-related, seniors, elderly, older, resistance band, elastic band, resistance rope, elastic rope, exercise, train, movement.

The first and second authors worked together to develop keywords and search strategies according to the requirements of each database. The first author independently reviewed the title and abstract of each study based on the inclusion and exclusion criteria. The first and second authors then read each full text independently and cross-checked it. Disagreements were resolved through discussion or through consultation with the third author. Meanwhile, the authors manually searched the references of the included studies to supplement unretrieved relevant literature.

2.3. Assessment of methodological quality

The first and second authors independently evaluated the quality of the included studies using the Mixed Methods Appraisal Tool (MMAT) [38]. After completing the evaluation, the results were cross-checked. If there was any disagreement, it was resolved through discussion. If there was still no decision, it was submitted to the third author for negotiation. There was 100% agreement between the first and second authors on the methodological quality entries of MMAT. The fourth author verified the methodological quality assessment.

2.4. Data extraction

The authors followed the JBI method of MMSR for data extraction [36, 37]. The extracted data included the author(s), year of publication, country, study methods, population, aim of the study, intervention delivery, outcome measures and key findings. The first author extracted the data independently, the second author checked the accuracy of the data extraction, and the third author randomly cross-checked the data to reduce the probability of data extraction errors. In case of disagreement, the full text was reread, and the results were discussed with the fourth author to resolve differences in the extracted data.

2.5. Data synthesis and integration

The authors followed the convergent segregated approach to synthesize and integrate the data based on the JBI methodology of MMSR [36, 37]. Although randomized controlled trials account for the majority of quantitative studies, meta-analyses cannot be conducted due to the heterogeneity of research interventions, results, and measurements. Therefore, quantitative results are reported in narrative form, and descriptive analysis is performed. The number of available qualitative studies was too few; therefore, a narrative synthesis was used to present the findings. Finally, we used a narrative synthesis approach to integrate the evidence from the quantitative and qualitative studies.

3.1. Characteristics of the included studies

Table 1 presents the key characteristics of the included studies. Most were published between 2013 and 2022, and the majority were quantitative studies, including 7 quantitative non-randomized studies [42, 46, 48, 54, 58, 65, 66], 1 quantitative descriptive study [39], and 17 quantitative randomized controlled trials [40, 41, 43–45, 47, 49–53, 59–64]. The subjects were all 60 or older; six of the studies looked specifically at older women [41, 51, 52, 60, 64, 65], and one specifically at older men [44].

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Table 1. Details of study characteristics.

https://doi.org/10.1371/journal.pone.0303372.t001

All studies involved elastic band resistance training in the elderly population. The duration of training is between one and 12 months, two to five times a week, for 30 to 80 minutes each time. The main outcomes measured in the quantitative studies were body balance, upper and lower limb muscle strength, endurance and flexibility, and mental health status. The qualitative study used semis-structured face-to-face interviews to focus on the experience and suggestions of the elderly on elastic band resistance training.

3.2. Quality evaluation of the included studies

All included studies were scored according to the MMAT. The specific evaluation results are shown in Table 2.

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Table 2. Quality assessment results according to mixed methods appraisal tool.

https://doi.org/10.1371/journal.pone.0303372.t002

3.3. Quantitative evidence

3.4. Qualitative evidence

Two qualitative studies and the qualitative portion of one study with a mixed approach explored the benefits, preferences and obstacles of elastic band resistance training in older adults.Two qualitative studies were conducted by Chen et al [55, 56]. The first study evaluated the feasibility of using a band resistance exercise regimen for older adults in wheelchairs [55]. After four weeks of elastic band resistance training, elderly people in wheelchairs were interviewed using semi-structured questionnaires to discuss the simplicity, safety, suitability, and helpfulness of the training and put forward suggestions. The second study by Chen et al [56] evaluated the feasibility of a band exercise program for older adults and determined appropriate exercise frequency and preferences for older adults. The study was divided into two stages. In the first stage, experts evaluated the simplicity, safety, suitability, and helpfulness of the program, scored each exercise, and put forward suggestions for modification. In the second stage, after a one-month group training with the elastic band for elderly individuals, participants were interviewed individually to evaluate the simplicity, safety, suitability, and helpfulness of the training and put forward suggestions. A mixed-methods study by Rathleff et al [57] investigated the feasibility and acceptability of unsupervised elastic band training for frail elderly inpatients. On day 1, the patient received 30 minutes of practice instruction, after which an unsupervised stretch band exercise was performed once daily, and the performance of the exercise was checked on days 2 and 4. Semi-structured interviews were held with patients and ward staff the day before discharge and after intervention.

Participants in all three studies reported physical and mental benefits of band resistance training [55–57]. After the intervention, participants felt that their muscles were more powerful in both their hands and legs, that they had increased body flexibility and joint range of motion, and they were more energetic and willing to continue participating in the stretch band exercises.

Participants also reported some preferences and barriers to training. In the first study by Chen et al [55], most participants tended to be placed in groups with 15 to 20 other participants, who engaged three times per week in 40 minutes of training. In the second study, most participants preferred to exercise in groups of 20 to 29 people for 1 hour 3 times a week. In addition, more than half of the participants preferred female coaches to lead them in the exercises [56]. Patients in the study of Rathleff et al [57] reported no difficulty in understanding and performing these exercises,the training time was unlimited, and the elastic band was easy to use and store. The motivation for training was mainly because they thought the exercises would help them return to their previous level of functioning. In addition to the physical benefits, the staff found that the exercises encouraged patients to take greater responsibility for their lives, and through active communication with the patients, they could learn which daily activities the patients needed help with and which ones they could perform independently. They also found that patients needed a certain level of cognitive ability to carry out the exercises independently. Statements about the amount of training indicated that patients did not truly care about the number of repetitions of the training movements but were more interested in whether they had been training at all times. If the training process was disturbed, the training amount was greatly affected.

3.5. Integration of quantitative and qualitative evidence

The quantitative and qualitative evidence was integrated based on five questions used to integrate evidence in the JBI methodology of MMSR [36, 37]. The independent syntheses of the quantitative and qualitative studies partially supported each other.

Evidence from integrated quantitative studies showed that elastic band resistance training helped to improve mental health, upper and lower limb flexibility, endurance, upper strength, and enhanced physical balance and cardiopulmonary function in older people, which has also been partially empirically verified in qualitative studies. Qualitative studies indicate that band resistance training could improve mental health, hand and leg muscle strength, and physical flexibility in older adults. However, there is no evidence from qualitative studies that training improved physical balance and cardiorespiratory function in older adults. One reason may be that relevant questions were not included in semi-structured interviews for qualitative research. Therefore, these two aspects should be discussed in future qualitative research on resistance training with an elastic band.

In the integrated quantitative study, the frequency of intervention was approximately 2–5 times per week, 30 to 80 minutes each time, which is consistent with the exercise preference of the elderly determined in the qualitative study (it was 40 to 60 minutes three times per week).

The number of exercise groups, repetitions, and mean and total muscle activation times were monitored in the study by Rathleff et al [57]. The results suggest that the current form of intervention was not feasible because few patients reached the standard training dose. However, qualitative evidence implies that patients and staff had a positive attitude toward the campaign. Future studies should adjust and refine interventions to improve patient adherence to exercise.

4.1. Effects on physical fitness and mental health

This mixed-methods systematic review pooled evidence from the quantitative and qualitative studies on the effects of elastic band resistance training on physical and mental health in older adults. The quantitative studies support the idea that training interventions in the elastic band group are effective in improving upper and lower limb flexibility, upper and lower limb endurance, upper strength, balance, and cardiopulmonary function in elderly individuals. The results are similar to studies of other types of resistance training such as with soft weights, ankle weights, and medicine balls, which indicate that resistance training improved balance and physical activity by increasing muscle mass, muscle strength, and bone density [67, 68]. Other studies used resistance training to achieve lipid reduction, and to improve blood sugar, blood pressure, blood lipids, lung capacity, muscle flexibility, and joint mobility function [69, 70]. Data from qualitative and quantitative studies are combined using established methods to increase the richness and robustness of the synthesis. In addition, by changing the thickness and length of the elastic band, the level of resistance training could be increased or decreased flexibly, expanding the range of application of elastic band resistance training, such as in frail elderly people, obese elderly people, and elderly people in wheelchairs [40, 41, 47].

Of the five quantitative studies, three showed positive effects on the mental health of older adults, and two showed no difference. In the qualitative studies, participants had a positive attitude toward resistance training with elastic bands and reported feeling more energetic in their daily activities after the intervention. Combined with the results of qualitative research, elastic band resistance training was an effective, safe and economical measure that was beneficial to the mental health of elderly individuals. The reason might be related to the improvement of physical function or social interaction of the elderly through exercise [50]. Active exercise not only played an important role in reducing the onset of disease and increasing the independence of older people but also enhanced their self-esteem and body image, encouraged them to adopt a healthier lifestyle, and was an effective way of coping with stress. In addition, from a physiological point of view, the slow and gradual increase in the intensity of resistance training with elastic bands led to decreased sympathetic nerve output and increased happiness [51]. However, due to the small number of studies on the improvement of mental health by resistance training with elastic bands, these results should be interpreted with caution.

4.2. Training preferences and obstacles

The quantitative part of Rathleff et al [57] found that few patients reached the standard training dose with unsupervised training, while the qualitative part found that patients did not truly care about the number of repetitions of training movements but were more interested in whether they were training all the time. Similar to previous findings, Liaghat et al [71] found that supervised training had potential benefits regarding quality of life, dropout, and training adherence. Dalager et al [72] found that supervision was not a significant predictor of compliance, but compared with the control group, the intervention effect of the supervision group was more significant. It is suggested that in the future resistance training, the support and supervision equipment of mobile technology should be applied, combined with remote sensing technology, remote control technology and information processing technology. In this way, individual elderly people can carry out personalized exercise guidance, functional training, evaluation and supervision, timely correction of irregular training movements, enhance training compliance, and improve exercise effects. In the first study by Chen et al [55], the majority of participants tended to take part in a group of 15 to 20 participants at a frequency of three times for 40 minutes per week. In the second study [56], it was found that most participants preferred the frequency of exercise for an hour three times a week in groups of 20 to 29 people. Some studies maintained that group intervention was an effective way to promote healthy behavior [73, 74]. The intervention process was conducive to peer support and communication, meeting the needs of interpersonal communication among elderly individuals, reducing loneliness, and promoting mental health. Group training can create cohesion, provide fun, and promote behavioral change, also known as a sense of belonging in a group [40]. In addition, more than half of the participants preferred a female trainer to lead their workouts. They believed that a coach must be patient with the learner, and it would be better if it was someone they knew well. One reason might be that a familiar coach made participants less nervous, made it easier to establish a trusting relationship, and helped them feel more confident about the task, thus allowing them to engage in the exercise environment. At the same time, group training at a time convenient for participants could also improve the effect of the intervention.

4.3. Included study quality

This review used MMAT to assess the quality of the included studies, which varied from study to study. All studies had clear research questions, and the collected data could also answer the research questions.

For quantitative studies, the problems of randomized controlled studies focused on the random allocation method and blind implementation of outcome index evaluators. Ten randomized controlled studies did not introduce how to implement the random allocation method in detail but only mentioned randomness [43, 44, 49–52, 60–62, 64]. Ten studies did not report on whether the outcome indicator evaluators were blinded [44, 45, 49–51, 59–61, 63, 64], and two studies mentioned that the outcome indicator evaluators were not blinded [40, 53]. In future studies, the random assignment method should be reported on in detail, and the outcome index evaluators should be blinded to improve study quality. In the inclusion of non-randomized controlled studies, 4 studies did not take into account confounding factors that might affect the interpretation of the results, which could be improved in future research [42, 48, 58, 66]. For qualitative research, all quality evaluation criteria are satisfied [55, 56].

4.4. Limitations

This review has some limitations. First, resistance training had many benefits for elderly individuals, not only in terms of mental health and physical fitness but also in terms of sleep quality, blood pressure, bone density, blood sugar in serum, total cholesterol, high-density lipoprotein, low-density lipoprotein, and other levels. However, integration failed due to the small number of relevant studies. Second, there were only two qualitative studies and one mixed-methods study, which limited the integration and analysis of the qualitative studies, thus requiring careful interpretation of the results from the qualitative evidence. Third, the number of quantitative studies assessing mental health was limited, the assessment tools were not targeted, and the results need to be interpreted with caution. Future studies should pay attention to the impact of elastic band resistance training on the mental health of elderly individuals. Fourth, due to the majority of quantitative studies in this systematic review, which also caused limitations for the integration of quantitative and qualitative evidence. It was suggested that qualitative research on elastic band resistance training should be strengthened in the future to supplement the views and suggestions of older people regarding this intervention.