Patients with heart failure (HF) report a subjective feeling of tiredness and dyspnea associated with a lack of conditioning of the respiratory and peripheral muscles.¹ Current guidelines suggest incorporating exercise and physical activity as supplementary therapies alongside pharmacological treatment, including inspiratory muscle training (IMT) and neuromuscular approaches.²

For individuals affected by HF, there are several factors that contribute to the impairment of skeletal muscles, such as vascular and metabolic factors and tissue alterations,³ which, in combination, can lead to patient limitations when exercising.⁴ In view of these aspects, it is recommended to limit the intensity of exercise when it is not carried out in hospital environments, thus avoiding possible adverse events.⁵

Inadequate blood perfusion of the cardiovascular system in patients with HF leads to early fatigue of the peripheral and respiratory systems.⁶ These patients fatigue early, since they have metabolic changes and changes in the types of muscle fibers, with type II predominating in their composition, which are more fatigable.⁷ These factors cause a decrease in strength, contraction speed, and power.⁸

Based on the above, IMT is an effective cardiac rehabilitation intervention for patients with HF. In the hospital environment, IMT helps patients with HF improve their inspiratory muscle strength. This improvement can help increase walking distance and reduce dyspnea.⁹

IMT can reduce symptoms such as dyspnea and inspiratory muscle fatigue through its effects on the cardiovascular and respiratory systems. Thus, IMT reduces inspiratory muscle work and attenuates the inspiratory metaboreflex, improving exercise tolerance.¹⁰ It also shows a significant improvement in systemic vasodilation and peripheral muscle perfusion, generating beneficial effects for patients by enhancing ventilatory function and functional capacity.¹¹

There are studies that have shown the effects of IMT in patients with HF, but we did not find any studies in which peripheral muscle training (PMT) was applied alongside IMT; therefore, the aim of this study was to evaluate the effects of IMT and PMT on respiratory and peripheral muscle strength, lung function, and functional capacity in patients with HF.

Over the course of the study, 52 patients were assessed, with an average age of 56 ± 5 years and a prevalence of males with 35 participants (67%). In terms of New York Heart Association classification, 37 (71%) of the patients had class III HF. The most common comorbidity was systemic arterial hypertension, which affected 44 (85%) of the patients, and hypertension was the most dominant etiology of HF. The other characteristics are shown in Table 1.

Table 1

	Control group (n = 13)	IMT group (n = 13)	PMT group (n = 13)	IMT + PMT group (n = 13)	p
Sex					0.87
Male	9 (69%)	8 (62%)	9 (69%)	9 (69%)
Female	4 (31%)	5 (38%)	4 (31%)	4 (31%)
Age (years)	56 ± 4	57 ± 5	55 ± 5	56 ± 3	0.76
BMI (kg/m 2 )	27 ± 2	26 ± 2	26 ± 3	25 ± 2	0.61
NYHA					0.81
Class III	9 (69%)	10 (77%)	8 (62%)	10 (77%)
Class IV	4 (31%)	3 (23%)	5 (38%)	3 (23%)
LVEF (%)	25 ± 1	26 ± 2	25 ± 2	24 ± 3	0.63
Comorbidities
Atrial fibrillation	3 (23%)	4 (31%)	3 (23%)	3 (23%)	0.77
SAH	11 (85%)	12 (92%)	10 (77%)	11 (85%)	0.81
CAD	4 (31%)	4 (31%)	5 (38%)	4 (31%)	0.75
DM	3 (23%)	4 (31%)	4 (31%)	5 (38%)	0.82
Previous smoking	2 (15%)	3 (23%)	2 (15%)	2 (15%)	0.88
Previous AMI	3 (23%)	3 (23%)	4 (31%)	4 (31%)	0.79
Etiology
Ischemic	3 (23%)	3 (23%)	4 (31%)	4 (31%)	0.87
Hypertensive	7 (54%)	7 (54%)	6 (46%)	7 (54%)	0.81
Idiopathic	2 (15%)	2 (15%)	3 (23%)	1 (8%)	0.69
Chagas disease	1 (8%)	1 (8%)	0	1 (8%)	0.91
Drugs
Furosemide	11 (85%)	12 (92%)	10 (77%)	11 (85%)	0.71
Spironolactone	10 (77%)	11 (85%)	9 (69%)	10 (77%)	0.77
ACE inhibitor/ARB	9 (69%)	9 (69%)	7 (54%)	8 (62%)	0.81
β-blocker	10 (77%)	10 (77%)	7 (54%)	9 (69%)	0.73

ACE: angiotensin converting enzyme; AMI: acute myocardial infarction; ARB: angiotensin receptor blocker; BMI: body mass index; CAD: coronary artery disease; DM: diabetes mellitus; IMT: inspiratory muscle therapy; LVEF: left ventricular ejection fraction; NYHA: New York Heart Association; PMT: peripheral muscle training; SAH: systemic arterial hypertension. Values are presented as mean ± standard deviation.

Table 2

	Control group (n = 13)		IMT group (n = 13)		PMT group (n = 13)		IMT + PMT group (n = 13)
	Baseline	Discharge	Baseline	Discharge	Baseline	Discharge	Baseline	Discharge
Respiratory strength
MIP (cmH2O)	75 ± 15	74 ± 16	73 ± 14	81 ± 15	75 ± 13	78 ± 15	74 ± 15	91 ± 16*§
MEP (cmH2O)	90 ± 19	86 ± 15	92 ± 17	97 ± 15	94 ± 20	99 ± 17	92 ± 19	102 ± 18§
Pulmonary function
VC (ml/kg)	45 ± 9	45 ± 6	47 ± 8	58 ± 9*§	43 ± 5	52 ± 8*§	45 ± 7	59 ± 5*§
PEF (l/min)	423 ± 69	420 ± 71	432 ± 77	450 ± 69	429 ± 57	443 ± 71	430 ± 71	456 ± 67
Peripheral strength
MRC scale	50 ± 3	51 ± 3	49 ± 4	52 ± 3	50 ± 3	55 ± 1	50 ± 4	55 ± 3
Distance covered
6MWT (meters)	419 ± 51	430 ± 42	425 ± 43	455 ± 39	422 ± 44	440 ± 39	438 ± 47	471 ± 51*§

IMT: inspiratory muscle therapy; MEP: maximum expiratory pressure; MIP: maximum inspiratory pressure; MRC: Medical Research Council; PEF: peak expiratory flow; PMT: peripheral muscle training; 6MWT: six-minute walk test; VC: vital capacity. *p < 0.05 versus baseline; § p < 0.05 versus control at the same time point.

Regarding muscle strength, we observed that the group receiving IMT along with PMT experienced a significant increase in both MIP (74 ± 15 at baseline versus 91 ± 16 at hospital discharge, p < 0.01) and MEP (92 ± 19 at baseline versus 102 ± 18 at hospital discharge, p < 0.01). With regard to lung function, the groups that underwent IMT, IMT, or IMT with PMT showed an improvement in VC when comparing baseline with discharge (p < 0.01). With regard to peripheral muscle strength, there was no statistically significant difference between any group and the first assessment. However, in terms of distance traveled, we observed that the group undergoing IMT combined with PMT experienced a significant improvement in the 6MWT (Central Illustration).

The aim of this study was to analyze the effects of IMT associated with PMT in patients with HF. There was an improvement in respiratory strength, pulmonary function, and peripheral strength, as well as an increase in the distance covered in the 6MWT. However, the group that performed IMT combined with PMT showed a statistically significant improvement.

Currently, the 6MWT can assess the progression of functional loss or the positive effect of therapeutic interventions.¹⁶Studies have shown that IMT attenuates the metaboreflex,¹⁷ which can limit exercise performance, especially in patients with HF and inspiratory muscle weakness.¹⁸ We found that IMT and PMT improved inspiratory muscle strength. The increased load on these muscles generates this increase in strength, optimizing greater vascularization in the lower limbs and, consequently, functional capacity.

IMT is known to contribute to better exercise tolerance and positive cardiorespiratory responses in patients with HF.⁷ Therefore, inspiratory muscle conditioning is beneficial for patients with HF, attenuating the inspiratory metaboreflex.¹⁷

The group that performed IMT combined with PMT showed significant results compared to the control group. IMT with an emphasis on MIP in patients with HF reduces the loss of respiratory muscle strength¹⁹ and reduces dyspnea when performing physical exercise.¹⁰

In patients with muscle weakness, the most frequent change in pulmonary volume is a reduction in VC.²⁰At the end of the protocol, there was a more marked increase in VC in the IMT + PMT group. In this context, the use of IMT helps to gain resistance in the inspiratory muscles, since patients with HF are predisposed to respiratory muscle weakness.¹

In relation to peripheral muscle strength, PMT increases muscle strength and the metabolism of creatine phosphate, which is a considerable energy store in the muscle. It also improves cardiovascular conditioning, corroborating an improvement in exercise tolerance and a reduced sensation of dyspnea.²¹ In this study, it is clear that the patients who underwent PMT and IMT + PMT had greater benefits, showing an improvement in quality of life when compared to the control group.

In terms of PEF, the results showed that the protocols combining IMT and PMT were significant, perhaps due to IMT, which helps patients gain muscle strength and improve respiratory biomechanics.²² In the control group, PEF decreased, since the disuse of these muscles causes a decrease in quality of life and respiratory muscle strength.

In this study, an important limitation was the absence of a scale to assess patients’ pain levels when carrying out the protocols. The scale is used to measure a patient’s pain threshold during treatment and therapeutic interventions, helping to manage this individual for better adherence and treatment comfort.

Based on the above, it can be concluded that combining IMT with PMT positively impacts patients with HF. This includes improvements in peripheral and respiratory muscle strength, reductions in dyspnea and fatigue, and better physical exercise tolerance.