Advs Exp. Medicine, Biology DOI 10.1007/5584_2014_20 # Springer International Publishing Switzerland 2014
Effects of Inspiratory Muscle Training on Resistance to Fatigue of Respiratory Muscles During Exhaustive Exercise M.O. Segizbaeva, N.N. Timofeev, Zh.A. Donina, E.N. Kur’yanovich, and N.P. Aleksandrova Abstract
The aim of this study was to assess the effect of inspiratory muscle training (IMT) on resistance to fatigue of the diaphragm (D), parasternal (PS), sternocleidomastoid (SCM) and scalene (SC) muscles in healthy humans during exhaustive exercise. Daily inspiratory muscle strength training was performed for 3 weeks in 10 male subjects (at a pressure threshold load of 60 % of maximal inspiratory pressure (MIP) for the first week, 70 % of MIP for the second week, and 80 % of MIP for the third week). Before and after training, subjects performed an incremental cycle test to exhaustion. Maximal inspiratory pressure and EMG-analysis served as indices of inspiratory muscle fatigue assessment. The before-to-after exercise decreases in MIP and centroid frequency (fc) of the EMG (D, PS, SCM, and SC) power spectrum (P < 0.05) were observed in all subjects before the IMT intervention. Such changes were absent after the IMT. The study found that in healthy subjects, IMT results in significant increase in MIP (+18 %), a delay of inspiratory muscle fatigue during exhaustive exercise, and a significant improvement in maximal work performance. We conclude that the IMT elicits resistance to the development of inspiratory muscles fatigue during high-intensity exercise. Keywords
Diaphragm • EMG • Inspiratory muscle fatigue • Parasternal • Scalene • Sternocleidomastoid M.O. Segizbaeva (*) Laboratory of Respiration Physiology, I.P. Pavlov Institute of Physiology, Russian Academy of Science, 6 Makarova nab., Saint Petersburg 199034, Russia e-mail: [email protected] N.N. Timofeev and E. Kur’yanovich Department of Natural Sciences, Military Sport Institute, 63, Bolshoy Sampsonievskyi Pr, Saint Petersburg 194353, Russia Z.A. Donina and N.P. Aleksandrova I.P. Pavlov Institute of Physiology, Russian Academy of Science, Saint Petersburg, Russia
1
Introduction
Inspiratory muscle fatigue develops during highintensity exercise in healthy human (Segizbaeva et al. 2013; Romer and Polkey 2008) and may limit maximal work performance (Perlovitch et al. 2007; Mador and Acevedo 1991),
M.O. Segizbaeva et al.
especially during loaded breathing (Segizbaeva and Aleksandrova 2009) or with a backpack load (Nadiv et al. 2012). Electromyographic (EMG) signs of diaphragmatic fatigue develop in normal subjects hyperventilating above 70 % of maximal voluntary ventilation as well as in chronic obstructive pulmonary disease (COPD) patients (Fitting 1991). Numerous studies have investigated the effect of specific inspiratory muscle training (IMT) on inspiratory muscle strength and endurance, respiratory function, and exercise performance in healthy subjects (Illi et al. 2012; Enright and Unnithan 2011; Verges et al. 2007), and COPD (Decramer 2009; Hill et al. 2006) and chronic heart failure (CHF) patients (Suh-Jen Lin et al. 2012). However, results have been mixed due to differences in training programs, experimental protocols, and subject selection. Controversy and debate still exist regarding the mode and intensity of training required to result in improvements in respiratory function and maximal work performance. It has been established that inspiratory muscle training intensities lower than 40 % of maximal effort do not translate into quantitative functional outcomes (Enright and Unnithan 2011). Training intensities of more than 50 % of maximal inspiratory pressure positively influence exercise capacity in healthy human, COPD, and CHF patients, but their effects on fatigue resistance of different inspiratory muscles are still unknown. In the present study we examined the benefits of a short program of incremental IMT on inspiratory muscle function and fatigue resistance of diaphragm (D), parasternal (PS), sternocleidomastoid (SCM), and scalene (SC) muscles during exhaustive exercise in healthy humans. Respiratory function and electromyography (EMG) served as markers of exerciseinduced inspiratory muscles fatigue.
2
Methods
The study was performed in accordance with the ethical standards of the Helsinki Declaration for Human Experimentation. A local Committee on Human Research approved the protocol of the
Table 1 Baseline characteristics of the subjects Anthropometrics Age (years) Body height (cm) Body weight (kg) BMI (kg.m 2) Pulmonary function FVC (l) FVC (%pred.) FEV1 (l) FEV1 (%pred.) FEV1/FVC (%) PEF (l/s) PEF (%pred.) HbO2Sat (%)
IMT-group
Control-group
19.8 0.6 (18–23) 176.3 2.3 (162–186) 75.3 2.2 (65–86) 24.2 0.47 (21.2–26.5)
19.4 0.6 (18–22) 179.1 1.9 (169–183) 78.1 2.4 (67–88) 24.8 0.72 (21.0–27.4)
4.96 0.22 (4.0–5.64) 94.6 2.7 (85–106) 4.54 0.27 (3.14–5.56) 96.7 1.3 (80–101) 94.7 0.3 (89–107) 8.0 0.6 (5.81–12.99) 89.7 4.2 (79–123) 98.5 0.3 (97–100)
4.81 0.28 (4.2–5.7) 93.4 3.1 (81–111) 4.61 0.29 (3.34–5.66) 97.5 1.4 (78–106) 96.1 0.4 (84–111) 7.8 0.8 (5.93–12.1) 91.9 3.2 (79–112) 98.6 0.2 (98–100)
Values are means SE (range) BMI body mass index, FVC forced vital capacity, FEV1 forced expired volume in 1 s, PEF peak expiratory flow, HbO2Sat percutaneous O2 saturation of hemoglobin in arterialized blood
study. Each subject was familiarized with the experimental procedures and protocol and gave informed consent to participate in the study. Ten healthy, nonsmoking, moderately trained male subjects underwent IMT, while the other six served as a control group. The baseline characteristics of the subjects are summarized in Table 1. There were no significant differences in anthropometric data, lung function parameters, and inspiratory muscle capacity between the groups. Subjects were free of cardiorespiratory diseases. They were involved in endurance and power sports and performed lowto-moderate intensity physical activity five times a week. They were requested to keep their individual physical activity constant 2 weeks prior to, and throughout the course of the study; except
Effects of Inspiratory Muscle Training on Resistance to Fatigue of. . .
for 2 days before the tests during which they were requested to refrain from physical activity. Also, they were asked to refrain from drinking caffeinated beverages on the test day and to have last meal at least 2 h prior the test.
2.1
Design Overview
All measurements were performed before the IMT and within 1 week after its completion. After familiarization with testing procedures, subjects underwent pulmonary function testing and performed an incremental exercise test to voluntary exhaustion. The maximal inspiratory pressure (MIP) was measured before and after the exercise test. Ten subjects performed specific inspiratory muscle training on a daily basis for 3 weeks, while the other 6 subjects served as a control group.
2.2
Pulmonary Function and Incremental Exercise Test
Pulmonary function test was performed with an ergospirometry-computerized device using a calibrated turbine for volume measurement (Schiller AG, Baar, Switzerland) in a sitting position. The forced expiratory volume in 1 s (FEV1), forced vital capacity (FVC), and peak expiratory flow (PEF) were recorded according to the recommendations of the ATS/ERS Statement (2002). Exercise test was performed on an electronically braked cycle ergometer (Schiller AG, Baar, Switzerland) using a standard (2-min) incremental cycle exercise protocol. After 5 min of breathing at rest while seated on the bicycle, subjects started with a 2-min period of pedaling with a workload 1 W/kg at 60–70 cycles/min. Then, workload was automatically increased by 0.5 W/kg every 2 min until the subject was no longer able to maintain the pedaling frequency at a constant level (not
Effects of Inspiratory Muscle Training on Resistance to Fatigue of Respiratory Muscles During Exhaustive Exercise M.O. Segizbaeva, N.N. Timofeev, Zh.A. Donina, E.N. Kur’yanovich, and N.P. Aleksandrova Abstract
The aim of this study was to assess the effect of inspiratory muscle training (IMT) on resistance to fatigue of the diaphragm (D), parasternal (PS), sternocleidomastoid (SCM) and scalene (SC) muscles in healthy humans during exhaustive exercise. Daily inspiratory muscle strength training was performed for 3 weeks in 10 male subjects (at a pressure threshold load of 60 % of maximal inspiratory pressure (MIP) for the first week, 70 % of MIP for the second week, and 80 % of MIP for the third week). Before and after training, subjects performed an incremental cycle test to exhaustion. Maximal inspiratory pressure and EMG-analysis served as indices of inspiratory muscle fatigue assessment. The before-to-after exercise decreases in MIP and centroid frequency (fc) of the EMG (D, PS, SCM, and SC) power spectrum (P < 0.05) were observed in all subjects before the IMT intervention. Such changes were absent after the IMT. The study found that in healthy subjects, IMT results in significant increase in MIP (+18 %), a delay of inspiratory muscle fatigue during exhaustive exercise, and a significant improvement in maximal work performance. We conclude that the IMT elicits resistance to the development of inspiratory muscles fatigue during high-intensity exercise. Keywords
Diaphragm • EMG • Inspiratory muscle fatigue • Parasternal • Scalene • Sternocleidomastoid M.O. Segizbaeva (*) Laboratory of Respiration Physiology, I.P. Pavlov Institute of Physiology, Russian Academy of Science, 6 Makarova nab., Saint Petersburg 199034, Russia e-mail: [email protected] N.N. Timofeev and E. Kur’yanovich Department of Natural Sciences, Military Sport Institute, 63, Bolshoy Sampsonievskyi Pr, Saint Petersburg 194353, Russia Z.A. Donina and N.P. Aleksandrova I.P. Pavlov Institute of Physiology, Russian Academy of Science, Saint Petersburg, Russia
1
Introduction
Inspiratory muscle fatigue develops during highintensity exercise in healthy human (Segizbaeva et al. 2013; Romer and Polkey 2008) and may limit maximal work performance (Perlovitch et al. 2007; Mador and Acevedo 1991),
M.O. Segizbaeva et al.
especially during loaded breathing (Segizbaeva and Aleksandrova 2009) or with a backpack load (Nadiv et al. 2012). Electromyographic (EMG) signs of diaphragmatic fatigue develop in normal subjects hyperventilating above 70 % of maximal voluntary ventilation as well as in chronic obstructive pulmonary disease (COPD) patients (Fitting 1991). Numerous studies have investigated the effect of specific inspiratory muscle training (IMT) on inspiratory muscle strength and endurance, respiratory function, and exercise performance in healthy subjects (Illi et al. 2012; Enright and Unnithan 2011; Verges et al. 2007), and COPD (Decramer 2009; Hill et al. 2006) and chronic heart failure (CHF) patients (Suh-Jen Lin et al. 2012). However, results have been mixed due to differences in training programs, experimental protocols, and subject selection. Controversy and debate still exist regarding the mode and intensity of training required to result in improvements in respiratory function and maximal work performance. It has been established that inspiratory muscle training intensities lower than 40 % of maximal effort do not translate into quantitative functional outcomes (Enright and Unnithan 2011). Training intensities of more than 50 % of maximal inspiratory pressure positively influence exercise capacity in healthy human, COPD, and CHF patients, but their effects on fatigue resistance of different inspiratory muscles are still unknown. In the present study we examined the benefits of a short program of incremental IMT on inspiratory muscle function and fatigue resistance of diaphragm (D), parasternal (PS), sternocleidomastoid (SCM), and scalene (SC) muscles during exhaustive exercise in healthy humans. Respiratory function and electromyography (EMG) served as markers of exerciseinduced inspiratory muscles fatigue.
2
Methods
The study was performed in accordance with the ethical standards of the Helsinki Declaration for Human Experimentation. A local Committee on Human Research approved the protocol of the
Table 1 Baseline characteristics of the subjects Anthropometrics Age (years) Body height (cm) Body weight (kg) BMI (kg.m 2) Pulmonary function FVC (l) FVC (%pred.) FEV1 (l) FEV1 (%pred.) FEV1/FVC (%) PEF (l/s) PEF (%pred.) HbO2Sat (%)
IMT-group
Control-group
19.8 0.6 (18–23) 176.3 2.3 (162–186) 75.3 2.2 (65–86) 24.2 0.47 (21.2–26.5)
19.4 0.6 (18–22) 179.1 1.9 (169–183) 78.1 2.4 (67–88) 24.8 0.72 (21.0–27.4)
4.96 0.22 (4.0–5.64) 94.6 2.7 (85–106) 4.54 0.27 (3.14–5.56) 96.7 1.3 (80–101) 94.7 0.3 (89–107) 8.0 0.6 (5.81–12.99) 89.7 4.2 (79–123) 98.5 0.3 (97–100)
4.81 0.28 (4.2–5.7) 93.4 3.1 (81–111) 4.61 0.29 (3.34–5.66) 97.5 1.4 (78–106) 96.1 0.4 (84–111) 7.8 0.8 (5.93–12.1) 91.9 3.2 (79–112) 98.6 0.2 (98–100)
Values are means SE (range) BMI body mass index, FVC forced vital capacity, FEV1 forced expired volume in 1 s, PEF peak expiratory flow, HbO2Sat percutaneous O2 saturation of hemoglobin in arterialized blood
study. Each subject was familiarized with the experimental procedures and protocol and gave informed consent to participate in the study. Ten healthy, nonsmoking, moderately trained male subjects underwent IMT, while the other six served as a control group. The baseline characteristics of the subjects are summarized in Table 1. There were no significant differences in anthropometric data, lung function parameters, and inspiratory muscle capacity between the groups. Subjects were free of cardiorespiratory diseases. They were involved in endurance and power sports and performed lowto-moderate intensity physical activity five times a week. They were requested to keep their individual physical activity constant 2 weeks prior to, and throughout the course of the study; except
Effects of Inspiratory Muscle Training on Resistance to Fatigue of. . .
for 2 days before the tests during which they were requested to refrain from physical activity. Also, they were asked to refrain from drinking caffeinated beverages on the test day and to have last meal at least 2 h prior the test.
2.1
Design Overview
All measurements were performed before the IMT and within 1 week after its completion. After familiarization with testing procedures, subjects underwent pulmonary function testing and performed an incremental exercise test to voluntary exhaustion. The maximal inspiratory pressure (MIP) was measured before and after the exercise test. Ten subjects performed specific inspiratory muscle training on a daily basis for 3 weeks, while the other 6 subjects served as a control group.
2.2
Pulmonary Function and Incremental Exercise Test
Pulmonary function test was performed with an ergospirometry-computerized device using a calibrated turbine for volume measurement (Schiller AG, Baar, Switzerland) in a sitting position. The forced expiratory volume in 1 s (FEV1), forced vital capacity (FVC), and peak expiratory flow (PEF) were recorded according to the recommendations of the ATS/ERS Statement (2002). Exercise test was performed on an electronically braked cycle ergometer (Schiller AG, Baar, Switzerland) using a standard (2-min) incremental cycle exercise protocol. After 5 min of breathing at rest while seated on the bicycle, subjects started with a 2-min period of pedaling with a workload 1 W/kg at 60–70 cycles/min. Then, workload was automatically increased by 0.5 W/kg every 2 min until the subject was no longer able to maintain the pedaling frequency at a constant level (not
