BACKGROUND: Maximal inspiratory pressure (MIP) is the most commonly used measure to evaluate inspiratory muscle strength. Normative values for MIP vary significantly among studies, which may reflect differences in participant demographics and technique of MIP measurement.OBJECTIVE: To perform a systematic review with meta‐analyses to synthesize MIP values that represent healthy adults.METHODS: A systematic literature search was conducted using Medline, EMBASE, Cochrane, Cumulative Index to Nursing and Allied Health (CINAHL) and Sport Discus databases. Two reviewers identified and selected articles, and abstracted data. Methodological quality was assessed using the Quality Assessment of Diagnostic Accuracy Studies (QUADAS) tool. A random‐effects model was used to calculate overall means and 95% CIs.RESULTS: Of 22 included articles, MIP data were synthesized according to age group and sex from six reports (n=840) in the meta‐analyses. The mean QUADAS score was 3.5 of 7. The age range was between 18 and 83 years (426 men, 414 women). MIP began to decrease with age in the 40 to 60 years age range and continued to fall progressively with age. For the same age group, men tended to have higher MIPs than women. Sensitivity analysis of withdrawing studies from the meta‐analysis identified one study that contributed more to heterogeneity in some age groups.DISCUSSION: MIP was higher in men and decreased with age, which was initially apparent in middle age. Several characteristics of participants and MIP technique influence values in healthy individuals.CONCLUSIONS: The present meta‐analysis provides normative MIP values that are reflective of a large sample (n=840) and likely represents the broadest representation of participant characteristics compared with previous reports of normative data.

Aging results in a decline in the function of the respiratory muscles. Inspiratory muscle training is emerging as a possible intervention to attenuate the decline of respiratory muscles in the elderly. The aim of this study was to evaluate the efficacy of inspiratory muscle training on respiratory strength, diaphragm thickness, and diaphragmatic mobility in elderly women. This was a controlled, randomized, and double-blind clinical trial, performed on 22 elderly women distributed in two groups, training (TG) and control (CG). Over an 8-week period a moderate intensity inspiratory muscle training protocol was followed in the TG, while CG followed a sham protocol. In addition maximum expiratory and inspiratory pressure, mobility of the diaphragm and diaphragmatic thickness were evaluated by ultrasound. After training, in TG maximal inspiratory pressure, maximal expiratory pressure, diaphragm thickness, and mobility increased by 37%, 13%, 11%, and 9% respectively, and their values were significantly higher than CG (p < .005, p = .013, p = .001, and p = .001). Inspiratory muscle training of moderate intensity improves respiratory muscle strength, diaphragm thickness, and diaphragm mobility in elderly women and it should be considered to minimize changes associated with senescence.

The last systematic review about respiratory muscle training (RMT) in people with asthma was published almost 10 years ago. Since then, several works have been published. To review the effect of RMT in people with asthma. We conducted a systematic review of research included up to September 2021 in PubMed/MEDLINE, PEDro, Scopus, Web of Science, CINAHL, LILACS, Cochrane Central Register of Controlled Trials and ClinicalTrials.gov. We included randomized controlled trials and quasi-experimental studies assessing the effect of RMT on respiratory muscle function, rescue medication, asthma-related symptoms, lung function, exercise capacity, healthcare use, health-related quality of life (HRQoL) and adverse effects in people with asthma. Risk of bias and methodological quality were assessed with the Cochrane Risk of Bias assessment tool and the PEDro scale. Meta-analysis was performed whenever possible; otherwise a qualitative approach was followed. Eleven studies (270 participants) were included, 10 with only adults and were included in the meta-analysis. Inspiratory muscle training (IMT) had beneficial effects on maximal inspiratory pressure (PImax: mean difference [MD] 21.95 cmH₂O [95% confidence interval [CI] 15.05; 28.85]), with no changes in maximal expiratory pressure (MD 14.97 cmH₂O [95%CI -5.65; 35.59]), lung function (forced expiratory volume in 1 sec: MD 0.06 [95%CI -0.14; 0.26] L; force vital capacity: MD 0.39 [95%CI -0.24; 1.02] L) and exercise capacity (standard mean difference [SMD] 1.73 [95%CI -0.61; 4.08]). Subgroup analysis revealed that IMT load >50% PImax and duration >6 weeks were beneficial for exercise capacity. The qualitative analysis suggested that IMT may have benefits on respiratory muscle endurance, rescue medication and exertional dyspnoea, with no adverse effects. This systematic review and meta-analysis showed a significant increase in PImax after IMT in adults with asthma and reinforced the relevance of the dose-response principle of training. More evidence is needed to clarify the effect of IMT in respiratory muscle endurance, rescue medication, exercise capacity, healthcare use and HRQoL. PROSPERO International Prospective Register of Systematic Reviews CRD42020221939; https://www.crd.york.ac.uk/prospero/display_record.php?RecordID=221939.

Maximal inspiratory and expiratory pressures (PImax/PEmax) reference equations obtained in healthy people are needed to correctly interpret respiratory muscle strength. Currently, no clear cut-off points defining respiratory muscle weakness are available. We aimed to establish sex-specific reference equations for PImax/PEmax in a large sample of healthy adults and to objectively determine cut-off points for respiratory muscle weakness. A multicentre cross-sectional study was conducted across 14 Spanish centres. Healthy non-smoking volunteers aged 18-80 years stratified by sex and age were recruited. PImax/PEmax were assessed using uniform methodology according to international standards. Multiple linear regressions were used to obtain reference equations. Cut-off points for respiratory muscle weakness were established by using T-scores. The final sample consisted of 610 subjects (314 females; 48 [standard deviation, SD: 17] years). Reference equations for PImax/PEmax included body mass index and a squared term of the age as independent variables for both sexes (p<0.01). Cut-off points for respiratory muscle weakness based on T-scores ≥2.5 SD below the peak mean value achieved at a young age were: 62 and 83cmH₂O for PImax and 81 and 109cmH₂O for PEmax in females and males, respectively. These reference values, based on the largest dataset collected in a European population to date using uniform methodology, help identify cut-off points for respiratory muscle weakness in females and males. These data will help to better identify the presence of respiratory muscle weakness and to determine indications for interventions to improve respiratory muscle function.