The effects of inspiratory muscle fatigue on subsequent high-intensity exercise performance and muscle tissue oxygenation / 体力科学

It has been suggested that inspiratory muscles fatigue impairing blood flow to the active limb muscle via respiratory muscle metaboreflex. The purpose of this study was to investigate the effects of inspiratory muscle fatigue on exercise performance and muscle tissue oxygenation in high-intensity exercise takes about 3.5~5min. Eleven healthy males subjects performed two conditions of constant-load exercise to exhaustion (TTE) on a cycle ergometer at 100% of maximal oxygen uptake. The two conditions—inspiratory muscle fatiguing (IMF) and non-fatiguing (PLA) —which had different intensity inspiratory resistance breathing (IRB) were performed before exercise. Muscle tissue oxygenations were measured by deoxyhemogrobin (HHb), oxygen saturation index (StO2) from right vastus lateralis during TTE. All data were analyzed from nine subjects whose inspiratory muscle were fatigued by IRB in IMF. Results: TTE was significantly shorter in IMF compare to PLA (244±31s vs. 268±38s, p<0.05). HHb was significantly higher and StO2 was significantly lower in IMF than in PLA (p<0.05). Conclusion: High-intensity exercise completed in 3.5~5 minutes, it was suggested that inspiratory muscle fatigue reduced the oxygen deriver to active limb muscle, resulting in decrease exercise performance. Improving function of inspiratory muscles, such as in inspiratory muscle training, may improve oxygenation of the active limb muscle and enhance exercise performance.

Fisiología respiratoria: fisiología de los músculos de la respiración / Physiology of the respiratory muscles

La respiración es un proceso continuo donde los músculos respiratorios tienen un rol central e imprescindible para la vida. Su óptimo funcionamiento involucra diversas estructuras que deben funcionar de forma armónica y coordinada, para que el gasto energético asociado a sus demandas permita aumentos considerables de carga sin afectar mayormente la función esencial de intercambio gaseoso. Comprender la fisiología muscular, desde la base anatómica hasta su comportamiento en el ejercicio y la enfermedad, es fundamental para detectar con anticipación las diversas disfunciones que se producen cuando este equilibrio se descompensa. El objetivo de esta revisión es entregar las bases fisiológicas del comportamiento de la musculatura respiratoria que permitan comprender y aplicar las mejores estrategias de evaluación y tratamiento, cuando la función normal se ve alterada, ya sea por enfermedad, desuso o altas cargas asociadas al ejercicio físico.

Breathing is a continuous process where the respiratory muscles have a central and essential role for life. Its optimal operation involves various structures that must work in a harmonious and coordinated way, so that the energy expenditure associated with their demands allows considerable increases in load without significantly affecting the essential function of gas exchange. Understanding muscle physiology, from the anatomical basis to its behavior in exercise and disease, is essential to anticipate the various dysfunctions that can occur when this balance is decompensated. The objective of this review is to provide physiological bases for the behavior of the respiratory muscles that allow understanding and applying the best evaluation and treatment strategies, when its correct functioning is altered, either due to illness, disuse or high loads associated with physical exercise.

Effect of Inspiratory Muscle Trainer on Running Performance and Respiratory Muscle Strength in Athletes

Background: Athletes are trained for specific games and for specific muscle groups. In all the games respiratory muscles with proper strength are needed so as to provide better outcome. But as the peripheral muscles are trained the Respiratory muscles are not trained specifically in any of the athlete. The less trained Respiratory muscles can directly affect the output of the Athlete by activating Metaboreflex. This reflex is activated when the Respiratory muscles gets fatigued; in which the blood is pulled towards the fatigued Respiratory muscles; due to which the peripheral muscle gets less blood and oxygen to work longer; which results in reduced output. So as to improve overall output, along with specific muscles, the Respiratory muscles should also be trained. Aim: This study was designed to evaluate the effect of Inspiratory Muscle Trainer on Running Performance and Respiratory Muscle strength in Athletes. Materials and methods: An Interventional study was conducted on Athletes studying in a Physical Education college Gujarat. The subjects were selected according to inclusion criteria. The Pre-training outcome of PImax (Inspiratory Mouth Pressure); PEmax (Expiratory Mouth Pressure) and time taken for 30m sprint was taken. And then subjects were divided into two groups’ one training and other control. Group A: Training for Respiratory muscles by Inspiratory Muscle Training Device along with other regular physical activity. Group B: Not getting any additional training for Respiratory muscle other than regular physical activity. The training was given at 50% PImax for 15 min a day for 6 weeks. At the end of 6 weeks postdata of PImax PEmax and speed were collected. Agnihotri DS, Bhise AR, Patel SM. Effect of Inspiratory Muscle Trainer on Running Performance and Respiratory Muscle Strength in Athletes. IAIM, 2016; 3(8): 159-163. Page 160 Results: Data analysis was done using SPSS20 version. In Experimental group Inspiratory Mouth Pressure, Expiratory Mouth Pressure improved significantly (p<0.05) also time taken for completion of 30msprint reduced significantly. (p<0.05) Conclusion: The Inspiratory Muscle Trainer can be used to improve Inspiratory Mouth Pressure, Expiratory Mouth Pressure and Running Performance in Athletes.

Intercostal and forearm muscle deoxygenation during respiratory fatigue in patients with heart failure: potential role of a respiratory muscle metaboreflex

The purpose of this study was to determine the effect of respiratory muscle fatigue on intercostal and forearm muscle perfusion and oxygenation in patients with heart failure. Five clinically stable heart failure patients with respiratory muscle weakness (age, 66±12 years; left ventricle ejection fraction, 34±3%) and nine matched healthy controls underwent a respiratory muscle fatigue protocol, breathing against a fixed resistance at 60% of their maximal inspiratory pressure for as long as they could sustain the predetermined inspiratory pressure. Intercostal and forearm muscle blood volume and oxygenation were continuously monitored by near-infrared spectroscopy with transducers placed on the seventh left intercostal space and the left forearm. Data were compared by two-way ANOVA and Bonferroni correction. Respiratory fatigue occurred at 5.1±1.3 min in heart failure patients and at 9.3±1.4 min in controls (P<0.05), but perceived effort, changes in heart rate, and in systolic blood pressure were similar between groups (P>0.05). Respiratory fatigue in heart failure reduced intercostal and forearm muscle blood volume (P<0.05) along with decreased tissue oxygenation both in intercostal (heart failure, -2.6±1.6%; controls, +1.6±0.5%; P<0.05) and in forearm muscles (heart failure, -4.5±0.5%; controls, +0.5±0.8%; P<0.05). These results suggest that respiratory fatigue in patients with heart failure causes an oxygen demand/delivery mismatch in respiratory muscles, probably leading to a reflex reduction in peripheral limb muscle perfusion, featuring a respiratory metaboreflex.

The contribution of inspiratory muscles function to exercise limitation in heart failure: pathophysiological mechanisms / Contribuição da musculatura inspiratória na limitação ao exercício na insuficiência cardíaca: mecanismos fisiopatológicos

BACKGROUND: Heart failure induces histological, metabolic and functional adaptations in the inspiratory muscles. This inspiratory muscle weakness, which occurs in 30% to 50% of the heart failure patients, is associated with reduction in the functional capacity, reduction in the quality of life and with a poor prognosis in these individuals. OBJECTIVES: The objective of this review was to discuss the pathophysiological mechanisms that may explain the role of the inspiratory muscles in the exercise limitation with focus in the reflexes that control the ventilation and the circulation during the exercise. METHOD: We performed searches in the PUBMED database using the terms "inspiratory muscles", "inspiratory muscle training", "metaboreflex" and chemoreflex" and including studies published since 1980. RESULTS: Inspiratory muscle weakness is associated with exercise intolerance and with an exaggerated inspiratory chemoreflex and metaboreflex in heart failure. The inspiratory metaboreflex may be attenuated by the inspiratory muscle training or by the aerobic exercise training improving the exercise performance. CONCLUSIONS: Patients with heart failure may present changes in the inspiratory muscle function associated with inspiratory chemoreflex and metaboreflex hyperactivity, which exacerbate the exercise intolerance.

CONTEXTUALIZAÇÃO: A insuficiência cardíaca (IC) acarreta alterações histológicas, metabólicas e funcionais dos músculos inspiratórios. A fraqueza dos músculos inspiratórios, que ocorre em 30% a 50% dos pacientes com IC, associa-se com a redução da capacidade funcional, prejuízos para a qualidade de vida e piora no prognóstico desses indivíduos. OBJETIVOS: Discutir os mecanismos fisiopatológicos que potencialmente explicam o papel da musculatura inspiratória na limitação ao exercício, abordando-se os reflexos que controlam a ventilação e a circulação durante o exercício. MÉTODO: Foram realizadas pesquisas na base de dados PUBMED, utilizando os termos inspiratory muscles, inspiratory muscle training, metaborreflex e chemoreflex e incluindo estudos publicados desde 1980. RESULTADOS: A fraqueza muscular inspiratória está relacionada com intolerância ao exercício e com exacerbação do quimiorreflexo e do metaborreflexo inspiratório na IC. O metaborreflexo inspiratório pode ser atenuado pelo treinamento muscular inspiratório ou pelo treinamento aeróbico, melhorando o desempenho ao exercício. CONCLUSÕES: Os pacientes com IC podem apresentar alterações da função muscular inspiratória associadas com hiperatividade quimiorreflexa e metaborreflexa inspiratória, as quais podem agravar a intolerância ao exercício.

Cardiovascular and Muscle Sympathetic Nerve Response During Repeated Static Grip Exercise / 体力科学

The aim of this study was to reveal the mechanism of exaggerated blood pressure rise during resistance exercise. Muscle sympathetic nerve activity (MSNA), heart rate (HR), blood pressure (BP) and grip force were measured during static handgrip exercise. After a 3-minute control period, intermittent static handgrip exercises (10 30-sec contractions with a 30-sec pause between contractions) at 30% of maximum voluntary contraction (HG 30) or with maximum voluntary effort (HGMX) were performed in nine healthy volunteers who gave their consent in advance to participate in this study. In the HG 30 study, MSNA did not increase compared with the control value until the fifth grip exercise, and BP rose during the third HG exercise. HR was elevated in the first grip exercise and remained elevated up to the 10th grip exercise. During HGMX, MSNA, HR and BP increased significantly during the first grip exercise compared to the control rest, and MSNA and BP rose even further as the contractions accumulated; while HR response remained almost constant throughout the contractions. Mean handgrip force decreased progressively with the increasing number of grip exercises.<BR>These results indicate that exaggerated BP rise during static muscle contraction dose not seem to be muscle reflex, at least, during the first several contractions; but rather other factors such as central command or mechanical compression of vessels. However, muscle reflex, for instance metaboor mechanoreflex may contribute to elevated BP when the number of contractions accumulate or muscle fatigue develops.