Efectos del entrenamiento de la musculatura inspiratoria en la función pulmonar, oxigenación muscular y rendimiento en sujetos físicamente activos

Résumé

Introduction Currently, technological development has allowed a deeper analysis of muscle metabolism and adaptations induced by physical training. In this context, the development of the near-infrared spectroscopy (NIRS) emerges as a non-invasive and easily applied strategy that allows the analysis of muscle oxygenation at a relatively modest cost. In recent years, NIRS has been used in both clinical and sports settings for muscle metabolism analysis, its applications are diverse, as well as its assessment protocols. Concurrent with scientific progress, numerous methods, complementary to traditional training, are being employed to improve sports performance and health. One of the methods that has been used in recent years is inspiratory muscle training (IMT), which is a tool that allows to apply training loads on respiratory muscles, thereby bolstering the power and endurance of these muscles at a relatively manageable cost and simplicity in application of these muscles. While the effects of IMT on health and improvement of physical performance are acknowledged, there is little evidence of its impact on resting muscle oxygenation and how it relates to physical performance. NIRS has been used to identify the effects of physical exercise and evaluations have been performed during the incremental physical exercise to analyze the kinetics of muscle oxygenation and arterial occlusions have also been used to determine the consumption of muscle oxygen (VO2) at rest, among other aspects. Although there is evidence on the effects of exercise on muscle oxygenation, there is little evidence on the effects of IMT in mVO2, particularly when analyzed employing a vascular occlusion test. For this reason, the analysis of the vascular occlusion at rest allows an analysis of the muscle metabolism without physical exercise, minimizing risk and enabling its applicability to both athletes and individuals with specific clinical conditions. In this sense, the present thesis heralds three pivotal contributions: a) the introduction of a novel evaluation instrument for analysis and monitoring, catering to physical activity and sports science professionals; b) reference values of muscle oxygenation at rest in physically active subjects; and, c) the analysis of muscular oxygenation, analyzed with NIRS, allows to relate the physical performance with the pulmonary function and the peripheral vascular response at rest. Objectives This doctoral thesis aimed to discern the effects of inspiratory muscle training on pulmonary function, maximum inspiratory strength, muscular oxygenation and physical performance in healthy active men. To achieve this objective, the following specific objectives were developed: 1) evaluate lung function, maximum inspiratory strength, muscle oxygenation and physical performance; 2) correlate lung function, maximum inspiratory strength, muscle oxygenation and physical performance; 3) analyze the effects of inspiratory muscle training on cardiorespiratory fitness and physical performance; and, 4) study the effects of the inspiratory muscle training program on lung function, maximum inspiratory strength, and muscle oxygenation. Methods Three studies were developed to carry out the development of the thesis. First, a systematic review was conducted, aiming to highlight the use of muscle oxygenation, in clinical trials with physical exercise interventions, presenting the technological characteristics related to the equipment used in these studies. Subsequently, an experimental study was developed that aimed to identify the effects of inspiratory muscle training on lung function, maximum inspiratory strength and physical performance in swimming events, in active healthy men. To conclude, a second experimental study was conducted, aiming to determine the effects of inspiratory muscle training on muscle vascular and metabolic changes, as well as its relation to changes in cardiorespiratory fitness, during running exercise in active healthy men. In the experimental studies, young, healthy, and physically active adults, participated. The participants were randomly divided into an inspiratory muscle training group and another group of placebo inspiratory muscle training. Both experimental studies involved the measurement of pulmonary function, the maximum inspiratory dynamic force and the physical performance. In addition, in the second experimental study, the muscle oxygenation at rest was analyzed during a vascular occlusion test (POV), utilizing an Artinis Portamon ® NIRS device positioned on the vast lateral of the quadriceps muscle. Results The systematic review demonstrated that NIRS is a technological tool, enabling muscle oxygenation analysis in clinical trials involving physical exercise interventions, which bases its applicability in the present doctoral thesis and future research endeavors. In the first experimental study, a correlation was found between dynamic inspiratory strength and swimming performance, in 50-and 100-meter free-style tests (R = -0.72; p = 0.003 and R = -0.65; p = 0.008). Additionally, a correlation was observed between maximum inspiratory flow and yield, in the identical swimming tests (r = -0.70; p = 0.003 and r = -0.60; p = 0.010). This study also highlighted the positive effect of inspiratory muscle training on swimming performance, where only the participants of the IMT group reduced swimming times by 50 m (p = 0.0001), 100 m (p = 0.0001) and 200 m (p = 0.0001). In terms of pulmonary function and maximum inspiratory strength, an increase of S-Index (p = 0.0003), inspiratory flow (p = 0.000), VEF1 (p = 0.007), FVC (p = 0.000), PEF p = 0.010), FEF25-75% (p = 0.030) and MVV (p = 0.000) were found in the IMT group alone. In the second experimental study a moderate positive correlation was found between the ΔS-Index (r = 0.619; p = 0.009) and the MIF (r = 0.583; p = 0.014) and the ΔVO2MAX, there was also a moderate positive correlation between the ΔTSIMB with the AUC of ΔHHb (r = 0.516; p = 0.031) and with the race time of Δ1.5 miles (r = 0.669; p = 0.004). Conversely, ΔTSIMP had moderate positive correlations with ΔHHbAUC (r = 0.596; p = 0.014) and with the race time of Δ1.5 miles (r = 0.686; p = 0.003). In addition, an increase in cardiorespiratory and functional capacity was observed for the inspiratory muscle training (IMTG) group with significant difference from the placebo inspiratory muscle training group (IMTPG), represented by an increase in VO2MAX (4.48 ± 1.1 versus Δ: 1.51 ± 2.5 ml/kg/min), and a decrease in test time of 1.5 miles (Δ: -0.81 ± 0.2 versus -0.27 ± 0.4 s), with p < 0.05. There was a higher increase in IMTG relative to IMTPG for S-Index (Δ: 28.23 ± 26.6 versus -13.83 ± 4.0 cmH2O) and MIF (Δ: 0.91 ± 0.6 versus -0.60 ± 0.1 l/s), with p < 0.05. Regarding muscle oxygenation at rest, significant decreases were observed in TSIMB and TSIMP for IMTG (Δ: 3.38 ± 3.1 and 0.83 ± 2.3 s) with respect to IMTPG (Δ: 5.88 ± 3.7 and 3.50 ± 6.4 s) with p < 0.05. In addition, HHb AUC had a significant decrease between baseline and post-intervention in IMTG alone (Δ: -1336.1 ± 1462.5 au), with p < 0.05. However, it did not differ with the decrease in IMTPG; therefore, only one trend was observed (Δ: IMTG: -1336.1 ± 1462,5au versus IMTPG: -32.3 ± 259.3ua; p = 0.054). Conclusions The current thesis demosntrates that NIRS is a tool that enables the analysis of resting muscle metabolism following the implementation of inspiratory muscle training programs, finding applicability in both sports and clinical settings. The parameters obtained from NIRS during resting vascular occlusion are a factor to consider for their relationship with lung functionality and physical performance. NIRS is positioned as a technique that allows real-time, low-risk, cost-effective, and straightforward monitoring of the effects of exercise programs on metabolism and microvascular responses at the muscular level, which provides a new tool to be considered by professionals of physical exercise and sports. As a general conclusion of this work, inspiratory muscle training produces positive effects on lung function, maximum inspiratory strength, muscular oxygenation and physical performance, in healthy active individuals. This doctoral thesis unveils new ways to utilize NIRS in inspiratory muscle training programs.