Adriano Florencio Vilaçaa; Bárbara Cristina de Souza Pedrosaa; Emanuelle Rocha Tenório de Françab; Thamara Cunha Nascimento Amarala; Maria do Amparo Andradeb; Célia Maria Machado Barbosa de Castroc; Eduardo Eriko Tenório de Françad
OBJECTIVE: Respiratory muscle training has been considered one of the main strategies to alleviate sarcopenia in older adults. Therefore, the present study aimed to verify which respiratory muscle training protocols are most used in this population and their main benefits described in the literature.
METHODS: A literature search was performed in the electronic databases PubMed, Latin American and Caribbean Health Sciences Literature (LILACS) and Scientific Electronic Library Online (SciELO). For this, we used the terms: respiratory muscle training, older adults, and muscle weakness. A total of 80 articles were studied, of which only 8 met the inclusion criteria of this study, whose methodology, variables studied, and outcome were analyzed.
RESULTS: Among the 8 articles analyzed, we can observe an important diversity of the studied protocols; and all articles showed the most varied gains possible with respiratory muscle training.
CONCLUSION: The protocols used in the various studies depend directly on the objective to be achieved with respiratory muscle training; and the main outcomes were improvements in strength, lung function, physical fitness level, quality of life, inflammatory markers and glucose intake.
Keywords: breathing exercises; aged; muscle weakness.
OBJETIVO: O treinamento muscular respiratório vem sendo considerado uma das principais estratégias para amenizar a sarcopenia em idosos, portanto, o presente estudo teve por objetivo verificar quais protocolos de treinamento muscular respiratório são mais utilizados em idosos e os seus principais benefícios encontrados na literatura.
MÉTODOS: Foi realizada pesquisa bibliográfica nas bases de dados eletrônicas PubMed, Literatura Latino-Americana e do Caribe em Ciências da Saúde (LILACS) e Scientific Electronic Library Online (SciELO). Para tanto, foram utilizados os termos: treinamento muscular respiratório, idosos e fraqueza muscular. Foi estudado um total de 80 artigos, dos quais apenas 8 preencheram os critérios de inclusão deste estudo, cuja metodologia, variáveis estudadas e desfecho foram analisados.
RESULTADOS: Dos oito artigos analisados, podemos observar uma importante diversidade dos protocolos estudados; e em todos os artigos foram encontrados ganhos dos mais variados possíveis com o treinamento muscular respiratório.
CONCLUSÃO: Os protocolos utilizados nos diversos estudos dependem diretamente do objetivo a ser alcançado com o treinamento muscular respiratório; e os principais desfechos foram a melhora na força, na função pulmonar, no nível de aptidão física, na qualidade de vida, em marcadores inflamatórios e no consumo da glicose.
Palavras-chave: exercícios respiratórios; idosos; fraqueza muscular.
Sarcopenia is known to be one of the main consequences of advancing age and is related to a functional decline, increased risk of falls and morbidity and mortality, leading to reduced performance of activities of daily living and entailing high costs for the health system.1-3 Gradual and progressive loss of muscle mass and strength occurs concurrently with that of the skeletal and respiratory muscles.4 The decline in respiratory muscle strength is a factor directly related to decreased lung function, resulting in reduced thoracic mobility and consequent reduction in lung volume and capacity.2
Reduction in respiratory muscle strength can be mitigated by the regular practice of physical exercise.5 Whole-body physical training and the simple practice of activities of daily living aim at maintaining peripheral and respiratory muscle strength, besides having positive outcomes in the cardiopulmonary and musculoskeletal systems and in the mental health of older adults.6,7 However, in individuals who have some physical limitation, the practice of certain activities may be limited; and the use of specific training for respiratory muscles may be an effective alternative method, able to decrease the sensation of dyspnea, increase the ability to perform daily activities, and improve quality of life.6,8
Respiratory muscle training (RMT) can be performed with some types of spring resistance devices such as Threshold and PowerBreathe, with loads imposed by volume and flow incentive spirometry or breathing techniques.2,6,7,9-11 Regardless of the technique used, breathing exercises aim to improve pulmonary function, respiratory muscle strength and thora-coabdominal mobility in geriatric patients, and are considered efficient and safe in physical therapy.2 However, there is still no consensus on the technique to be performed nor the time and load of each device. Therefore, the aim of this study was to verify which RMT protocols are most used in older adults and their main benefits described in the literature.
The literature research was performed in the following electronic databases: PubMed, Latin American and Caribbean Health Sciences Literature (LILACS), and Scientific Electronic Library Online (SciELO). For this purpose, the terms used were: respiratory muscle training, older adults, and muscle weakness. The searches were performed restricting the date for articles published between 2008 and 2018, in English and Portuguese, including studies that addressed cases in which the intervention in older adults was exclusively by RMT. Thus, of the 80 articles studied, only eight were analyzed, as they met the inclusion criteria of this study. We excluded (n = 72) articles that met any of the following criteria: repeated articles, articles without abstract or full text, literature review articles, articles involving other non-geriatric populations submitted to RMT, articles that did not directly respect the searched descriptors, dissertations, theses and monographs.
RESULTS AND DISCUSSION
Among the 80 articles studied, only eight were controlled clinical trials using devices to perform RMT in older adults. The articles compared breathing training with placebo (n = 2),12,13 with a group without any intervention (n = 3),8,9,14 or with different devices among themselves (n = 3).2,4,15 The outcomes evaluated were: lung strength and function, quality of life, ability to perform daily activities, functional autonomy, as well as hematological and hemodynamic markers.
Table 1 presents data from the studies selected for this review: author, group, methodology used, variables analyzed, and conclusion of each study.
Related articles ranged from 12 to 27 participants per group, totaling 330 participants. The number of groups participating in each study ranged from 2 in (6 studies)2,9,12-15 to 3 (in 2 studies),4,8 totaling 18 groups; and in most studies there was 1 control group without respiratory training (3 studies)6,8,9 or with RMT with placebo (2 studies).12,13 The Threshold was the most used device by the trained groups (58% among devices), but Voldyne, PowerBreathe Classic, Respiron and Powerlung were also used to strengthen the respiratory muscles.
Regarding the time used for the intervention, the studies ranged from 1 to 8 weeks of training. One study trained the muscles of older women with and without metabolic syndrome for 7 days,15 another used 12 days to perform the intervention;2 2 studies lasted 6 weeks,8,14 3 studies lasted 8 weeks,9,12,13 and a 10-week training was conducted in one of the studies.4 The frequency of RMT during the week also varied, with 1 study performing 3 workouts per week4 and 2 studies8,14 with training 5 times a week. The study by Watsford & Murphy9 conducted 6 days of training during the week, but with 2 workouts per day; and the other 4 studies,2,12,13,15 trained every day.
As for the size of the load used and the number of repetitions for each series of exercises, there was a great variation among all articles and it was observed that they were inversely proportional and depended on the objective of each author. For strength training, shorter series with higher load were prioritized, while for endurance training, smaller loads were used with a higher number of repetitions. Most studies (75%) used initial load between 30 and 50% of maximal inspiratory pressure (MIP), and 2 of them4,14 increased the load during training. The study by Pascotini et al.2 used volume and flow incentive spirometry and increased the number of repetitions every 4 days, starting with 3 sets of 8 repetitions; and at the end of 12 days, participants performed 3 sets of 12 repetitions.
Predominant variables in the studies were: respiratory muscle function and strength, functional autonomy level, and quality of life in older adults; which generally had significant improvement with the regularly performed RMT. The results by Iranzo et al.14 were different from most studies, since the Threshold was not able to improve respiratory strength and endurance parameters in older adults. The justification for these differences may be the type of population evaluated, considering that the mean age of the sample was 85 years, against 65-70 years in the other studies. Another important factor was the previous physical limitations of the population, when these individuals had inability to walk and functional limitations.
Mills et al.12 observed positive results, similar to the others, regarding strength and respiratory function parameters. In addition, they sought to analyze the effects of RMT on blood inflammatory markers in the hypothesis that increased respiratory work was directly related to systemic inflammation, with a reduction in the evoked plasma interleu-kin-6 response. However, after 8 weeks of training, no significant changes in inflammatory cytokines or DNA damage in peripheral mononuclear cells were observed. The size of the load applied and the number of repetitions performed during muscle training were questioned and possibly justify the treatment failure for these variables.
Inspiratory muscle metaboreflex is a sympathetic nervous system-mediated response in which there is vaso-constriction in skeletal muscles during an exercise, limiting physical performance by reducing blood flow to active muscles.16 Studies have associated RMT with metaboreflex attenuation in different populations, increasing oxygen supply to peripheral muscles during exercise, improving performance and tolerance.17,18 This mechanism would explain the improvement in submaximal incremental test performance in Watsford & Murphy’s research,9 although Borg’s reports on the lower limbs did not change during the exercise; as well as the improvement in most functional domains evaluated by Fonseca et al.4 and in the 6-minute walk test (6MWT), evaluated by Huang et al.8 in the group without chronic obstructive pulmonary disease (COPD).
The results presented by Mills et al.12 showed no increase in the distance covered in the 6MWT after RMT, which means that there was no performance improvement during the exercise, which is due to the profile of the evaluated patients. While Huang et al.8 trained older adults with a baseline walking test score of 90% of the predicted for their age, Mills et al.12 performed training on older adults with 102 to 103% of the predicted distance for this population. This fact may be best explained by a 2012 meta-analysis,19 which suggests that participants with a lower baseline fitness level had an increased ability to exercise after RMT, compared with those who already performed better.
Another benefit of RMT is the regulation of blood glucose levels, an important function, especially in patients with type II diabetes mellitus. This may be explained by decreased insulin resistance after exercise, where regular training can increase glucose transporter 4 (GLUT-4) mobilization and, consequently, increase blood glucose uptake.13,20,21 The results of Silva et al.13 corroborate most previous studies, when an 8-week Threshold protocol was sufficient to decrease blood glucose levels, proving to be an alternative strategy for those patients who have contraindications to perform other exercise modalities. In contrast, the 7-day RMT protocol used by Feriani et al.15 was not sufficient to achieve significant changes in blood glucose in older women with metabolic syndrome, requiring more training days for such changes.
Due to the numerous protocols used for RMT, it is clear that the number of repetitions, the size of the load, and the number of days used depend directly on the objective to be achieved. RMT in older adults has proved to improve muscle strength and lung function, and showed evidence of increased physical fitness, improved quality of life and inflammatory markers, as well as increased glucose intake. We can also observe that there was no device that was considered superior to another in relation to RMT in older people.
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December 12 2018.
Accepted em April 27 2019.