Impacto del Entrenamiento Respiratorio de Hiperpnea Isocápnica Voluntaria sobre el Costo Energético asociado a la Respiración inducido por Ejercicio Físico / Impact of Voluntary Isocapnic Hyperpnea training on the cost of breathing

Introducción. Determinar el efecto de ocho semanas de entrenamiento por hiperpnea isocápnica voluntaria (HIV) sobre el costo energético asociado a la respiración (COB) reflejado en los cambios en la oxigenación de los músculos intercostales (∆SmO2-m. intercostales) inducida por ejercicio físico de intensidad incremental. Métodos. Doce participantes físicamente activos fueron entrenados durante ocho semanas de HIV 3 días x semana, 12 minutos, al 60% de ventilación voluntaria máxima (VVM). En la semana previa y posterior al entrenamiento HIV se realizó un test cardiopulmonar (CPET) de intensidad incremental en cicloergómetro, durante esta prueba se registró la ∆SmO2-m. intercostales mediante el dispositivo MOXY®. El efecto de HIV sobre la ∆SmO2-m. intercostales se analizó mediante la prueba two-way mixed ANOVA considerando los factores (fase × tarea). Resultados. ∆SmO2-m.intercostales fue significativamente menor a partir del 30% (­5,0±4,7%; p<0.01) hasta el 100% (­10,6±12,8%; p<0.01) de la tarea luego de ocho semanas de HIV. Además, se reportó un aumento de la presión inspiratoria máxima (PIM)=16,5±11,4 cmH2O (p<0.01); y de la resistencia muscular respiratoria=106,6±149,0 s (p<0.01). El tiempo total de ejercicio aumentó en 106,6±149,0 s (p=0.04), así como la carga total en 10,50± 10,12 vatios (p<0.01). Conclusión. El HIV disminuye el COB inducido por ejercicio incremental asociado a un incremento en la performance física y de los músculos respiratorios. En futuros estudios se sugiere estudiar esta estrategia de entrenamiento analítico de los músculos respiratorios en usuarios con limitación física relacionada al aumento prematuro del COB.

Background. Objetive. To determine the effect of eight weeks of voluntary isocapnic hyperpnea (VIH) training on cost of breathing (COB) as reflected by intercostales muscles deoxygenation (∆SmO2-m. intercostales) induced by incremental-intensity physical exercise. Methods. Twelve physically active participants underwent eight weeks of VIH training, three days a week, for 12 minutes each session, at 60% of maximal voluntary ventilation (MVV). In the week before and after VIH training, a cardiopulmonary test (CPET) of incremental intensity was performed on a cycloergometer. During this test, intercostal ∆SmO2-m.intercostales was recorded using the MOXY® device. The effect of VIH on ∆SmO2-m.intercostales were analyzed using a two-way mixed ANOVA test considering the factors (phase × task). Results. ∆SmO2-m.intercostales significantly decreased from 30% (­5.0±4.7%; p<0.01) to 100% (­10.6±12.8%; p<0.01) of the task after eight weeks of VIH. Additionally, an increase in maximal inspiratory pressure (MIP) of 16.5±11.4 cmH2O (p<0.01) and respiratory muscle endurance of 106.6±149.0 s (p<0.01) was reported. Total exercise time increased by 106.6±149.0 s (p=0.04), as well as total workload by 10.50±10.12 watts (p<0.01). Conclusion. VIH reduces COB induced by incremental exercise and is associated with increased physical and respiratory muscle performance. Future studies should explore this respiratory muscle training strategy for individuals with physical limitations related to a premature increase in COB.

Trigger point dry needling increases masseter muscle oxygenation in patients with temporomandibular disorder

Abstract Background: Temporomandibular disorder (TMD) is an umbrella term encompassing various clinical complaints involving the temporomandibular joints, masticatory muscles, and/or associated orofacial structures. Myogenous TMDs are the most frequent cause of chronic orofacial pain. Musculoskeletal pain is commonly associated with myofascial trigger points (MTPs), for which dry needling (DN) is a routine treatment. Objective: To investigate muscle oxygenation and pain immediately after DN application on an MTP in the masseter muscle of patients with myogenous TMDs. Methodology: Masseter muscle oxygen tissue saturation indices (TSI%) were assessed by near-infrared spectroscopy (NIRS) pre- and post-interventions by a randomized, controlled, double-blind, crossover DN/Sham clinical trial (primary outcome). Pain was investigated by the visual analog scale (VAS). In total, 32 individuals aged from 18 to 37 years who were diagnosed with myogenous TMD and myofascial trigger points in their masseter muscles participated in this study. Relative deltas for the studied variables were calculated. Data normality was tested using the Shapiro-Wilk test. According to their distribution, data were analyzed by two-way ANOVA and the Student's t-, and Mann-Whitney tests. Statistical analyses were performed using Prism® 5.0 (GraphPad, USA). Results: We found a significant difference (2,108% vs. 0,142%) between masseter muscle TSI% deltas after the DN and Sham interventions, respectively (n=24). We only evaluated women since men refused to follow NIRS procedures. Pain increased immediately after DN (n=32, 8 men), in comparison to Sham delta VAS. Conclusion: These findings show an increase in tissue oxygen saturation in the evaluated sample immediately after the DN intervention on the MTP of patients' masseter muscle. Pain may have increased immediately after DN due to the needling procedure.

Local muscle oxygenation during different cuff-pressures intervention: a punctual near-infrared spectroscopy measurement

Abstract Aim: To verify the response of tissue saturation index (TSI) during ischemia-reperfusion (IR) interventions with different cuff-pressures. Methods: Twenty-nine healthy men experienced in resistance training were recruited. Each one has undergone a control condition (no cuff) and one of the three IR interventions: 1) 190 mmHg (CP-190, 22.7 ± 3.0 years; 176.6 ± 3.9 cm; 77.3 ± 9.5 kg; 2) 100 mmHg (CP-100, 22.9 ± 6.3 years; 180.5 ± 4.0 cm; 85.2 ± 14.1 kg) and 3) 20 mmHg (CP-20, 20.3 ± 2.4 years; 171.8 ± 5.2 cm; 72.4 ± 6.0 kg). Cuffs were placed on the proximal region of the thighs. IR interventions consisted of three cycles of 2-min occlusion-reperfusion. TSI was measured using near-infrared spectroscopy (NIRS), positioned on the middle portion of the vastus lateralis of the dominant leg. The oxygenation was measured at the control conditions (no cuff) and during cuff interventions. Results: While TSI values of CP-20 did not change compared to control (p > 0.05), the TSI in CP-190 was lower in the ischemia (p < 0.05), and CP-100 was lower in the second and third ischemia (p < 0.05). However, the TSI value increased during reperfusion but did not return to control levels (p < 0.05). Conclusion: TSI of the CP-190 significantly decreased during ischemia. However, these values increased by about 16% in the reperfusion period. Thus, our results show that the RI intervention may have caused an increase in metabolic demand, as even with the release of blood flow, the TSI values were below those of the other interventions.

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.

Oxigenación de músculos respiratorios y locomotores durante el test cardiopulmonar en pacientes con circulación de fontan: serie de casos / Patients with fontan: oxygen consumption in respiratory and Locomotor muscles during excersie testing

Resumen: Antecedentes: Los pacientes con circulación de Fontan (PCF) presentan limitación cardíaca durante el esfuerzo máximo lo que repercute en menor capacidad de ejercicio (VO2-peak). La rehabilitación cardiovascular (RC) revierte este desacondicionamiento, al aumentar el gasto cardíaco y diferencia arteriovenosa de oxígeno, aspectos evaluados con monitorización invasiva y gases exhalados. La valoración no invasiva de la saturación muscular de oxígeno (SmO2) es un método de reciente aplicación para evaluar la limitación muscular al ejercicio. En PCF esta limitación puede atribuirse a la mayor acción de músculos respiratorios (cambios ventilatorios) y/o locomotores (carga periférica). Objetivo: Evaluar el trabajo de músculos respiratorios y locomotores durante el ejercicio físico máximo e incremental mediante los cambios en la SmO2. Métodos: A seis PCF (5 hombres; 13.8±2.9 años; 158±9cm; 49.8±13.3 kg) se les valoró el VO2-peak (23.0±4.5mL·kg-1·min-1) mediante ciclo-ergoespirometría sincrónicamente con SmO2 en músculos respiratorios (SmO2-m.Intercostales) y locomotores (SmO2-m.Vastus-Laterallis) mediante espectroscopía cercana al rango infrarrojo durante el test cardiopulmonar. Resultados: SmO2-m.Intercostales disminuyó desde el 60% del VO2-peak (p<0.05), mientras que SmO2-m.Vastus-Laterallis no cambió. La ventilación pulmonar (VE) aumentó progresivamente, siendo significativo a partir del 60% VO2-peak (p<0.05). La mayor desoxigenación de SmO2-m.Intercostales (∆SmO2) se asoció con los máximos cambios en ventilación pulmonar (∆VE) en ejercicio (rho=0.80; p=0.05). Conclusiones: Durante un protocolo de esfuerzo, los pacientes con circulación de Fontan presentan mayor trabajo muscular respiratorio que locomotor. Los cambios en la ventilación pulmonar se asocian a mayor extracción de oxígeno en la musculatura respiratoria, reforzando la necesidad de incorporar el entrenamiento respiratorio en la rehabilitación cardiovascular.

Abstract: Background: During a maximum incremental exercise patients with Fontan circulation (PFC) show cardiac limitation reducing aerobic exercise capacity (VO2-peak). Cardiovascular rehabilitation (CR) reverses this deconditioning by increasing cardiac output and arteriovenous oxygen difference, aspects that can be evaluated by invasive methods and analyzing the exhaled gases. Non-invasive assessment of muscle oxygen saturation (SmO2) is a novel method for recording local oxygen levels. By this technology, it is possible to evaluate the muscle limitation to exercise. In PFC, that limitation could be attributed to higher contractions of respiratory (ventilatory changes) and/ or locomotor muscles (peripheral load). Objective: To evaluate in PFC the changes at SmO2 of respiratory and locomotor muscles during a maximum and incremental exercise protocol (cardiopulmonary test, VO2-peak). Methods: Six PFC (5 men; 13.8±2.9 years; 158±9 cm; 49.8±13.3 kg) were assessed during the VO2peak test (23.0±4.5mL·kg-1·min-1) by cyclo-ergospirometry synchronously with SmO2 at respiratory (SmO2-m.Intercostales) and locomotor (SmO2-m. Vastus-Laterallis) muscles by Near-Infrared Spectroscopy (NIRS). Results: SmO2-m.Intercostales decreased from 60% of VO2-peak (p<0.05), while SmO2-m.Vastus-Laterallis did not change. Minute ventilation (VE) increased progressively, showing changes to rest at 60% of VO2-peak (p<0.05). The higher deoxygenation of SmO2-m.Intercostales (∆SmO2) correlated to maximum changes of lung ventilation (∆VE) (rho=0.80; p=0.05). Conclusions: During an incremental and maximum exercise protocol, patients with Fontan circulation have more work at respiratory than locomotor muscles. Changes in VE are direct associated with greater extraction of oxygen at respiratory muscles, reinforcing the incorporation of respiratory muscle training in cardiovascular rehabilitation.

EFFECT OF PEDAL RATE AND TORQUE ON MUSCLE OXYGENATION AND ENERGY METABOLISM / 体力科学

The purpose of this study was to investigate the effect of constant endurance cycling exercise below Ventilatory Threshold (VT), under different pedal rate/torque regulations (PTR), on muscle oxygenation, as well as cardio-respiratory function and energy metabolism. Eight healthy male adults participated in the study for three tests. The first test was to examine the maximum oxygen uptake (VO₂max) using a ramp loading measurement of 60 rpm, 20 watt/min ; and an individual 80%VT load was obtained. The second and third tests (random) were to measure heart rate (HR), blood pressure (MAP), expired gas and NIRS data before, during and after 30 min 80%VT constant cycling exercise with low pedal rate/high torque (LPHT : 32 rpm, 23.3±6.0Nm) or high pedal rate/low torque (HPLT : 79rpm, 9.4±2.4Nm). As a result, HPLT showed higher values in HR (p<0.001), MAP (p<0.001), VO₂ (p<0.001), VCO₂ (p<0.001) and RER (p<0.05), than LPHT ; but LPHT showed a higher fat consumption rate than HPLT (p<0.05). Significant PTR effect were recognized for the parameters of the tissue hemoglobin index (THI) (p<0.001) and oxygenation hemoglobin (ΔO₂Hb) (p<0.01) ; and both indicated higher values for HPLT than LPHT ; but LPHT showed insignificantly (p=0.066) higher de-oxygenation hemoglobin (ΔHHb) than HPLT. Moreover, the significant time effects of THI and ΔO₂Hb were also recognized. In conclusion, this study indicated that during constant cycling exercise below VT, HPLT might result in greater muscle blood volume, higher muscle oxygenation concentration and higher HR and VO₂ compared with LPHT. These results suggest that, HPLT might be effective in alleviating the working load on lower limbs, as well as promoting muscle oxygenation, cardiorespiratory function (systemic oxygen supply) and energy metabolism. Therefore, HPLT constant cycling exercise below VT could be used in a rehabilitation program as a beneficial exercise for elderly people with decreasing muscle strength in their lower limbs.

A COMPARISON OF CYCLISTS AND NON-CYCLISTS' THIGH MUSCLE OXYGENATION STATE DURING PEDALING / 体力科学

The purpose of this study was to compare the thigh muscle oxygenation state of competitive road cyclists and non-cyclists during varied pedaling frequency cycling. Six male college road cyclists (CY group) and five male students (NC group) performed four sets of cycling bouts, consisting of 2 minutes of warm up (60 rpm, 50 watts) followed by 5 minutes of pedaling (150 watts) using an electro-magnetic braked cycle ergometer at 40, 60, 90, and 120 rpm. Oxygenated hemoglobin and/or myoglobin (Oxy-Hb/Mb) and deoxygenated Hb/Mb (Deoxy-Hb/Mb) concentrations in the vastus lateralis were measured by near infrared spatially resolved spectroscopy. The Oxy-Hb/Mb level was significantly higher in the CY group than the NC group. But there was no significant intraction effect of the group and pedaling rate on the Oxy-Hb/Mb level. These results suggest that the changes in muscle oxygenation state according to pedaling cadence do not differ between cyclists and non-cyclists. And though the whole body work efficiency decreased according to increasing pedaling cadence, Oxy-Hb/Mb and Deoxy-Hb/Mb levels in the vastus lateralis remained unchanged up to 90 rpm. However, at 120 rpm, the Oxy-Hb/Mb level decreased remarkably and the Deoxy-Hb/Mb level increased. These results suggest that deoxygenation in the vastus lateralis at 120 rpm was higher than that for lower frequencies. And, conversely, oxygen uptake in the vastus lateralis might have increased steeply at 120 rpm. It may be that the maximum pedaling cadence that would not reduce work efficiency in the vastus lateralis is around 90 rpm.

Relationship between the intensity of muscle contraction and muscie oxygenation of the m. rectus femoris during dynamic knee extension / 体力科学

This study investigated the relationship between the intensity of muscle contraction and muscle oxygenation during dynamic knee extension. Six healthy male subjects (age 24.6±1.2 years) performed knee extension (concentric : 1 s/eccentric : 1 s) to exhaustion at 3 different intensities, 30%, 20% and 10% of maximum voluntary contractile strength (MVC) . A near-infrared spectroscopy (NIRS) probe and surface electrodes of the electromyogram were fixed on the m. rectus femoris. The muscle oxygenation and integral electromyogram (IEMG) were recorded both during and after dynamic knee extension.<BR>The summary of the results was as follows.<BR>1) Continuous time of knee extension decreased with increasing intensity of muscle contraction. There were significant differences between 10%MVC and 20%MVC (p<0.001), and 10%MVC and 30%MVC (p<0.001) .<BR>2) The oxy-hemoglobin level during knee extension decreased with increasing intensity of muscle contraction. There were significant differences between 10%MVC and 30%MVC (p<0.001), 20%MVC and 30%MVC (p<0.001), and 10%MVC and 20%MVC (p<0.05) .<BR>3) Recovery time after knee extension increased with increasing intensity of muscle contraction. There were significant differences between 10%MVC and 30%MVC (p<0.01), and 20%MVC and 30%MVC (p<0.01) .<BR>4) The IEMG increased with increasing time of knee extension. The maximum value was observed just before completing the knee extension on the IEMG. The rate of increase in the IEMG increased with decreasing intensity of muscle contraction.<BR>These results suggest that muscle oxygenation during dynamic knee extension decreases with increasing intensity of muscle contraction, and influences continuous time of muscle contraction.

Pattern of deoxygenation in vastus lateralis and rectus femoris muscles during a ramp-loaded cycling / 体力科学

The purpose of this study was to compare changes in oxygenation in the Vastus Lateralis (VL) and Rectus Femoris (RF) muscles during a ramp-loaded bicycle exercise. Twelve healthy males participated in the experiment. The test consisted of a leg arterial occlusion at rest and a ramp-loaded exercise (20 watts/min) using a bicycle ergometer until exhaustion. The changes in deoxygenation in each muscle was measured by near infrared spectrometer (NIRS) . The probes of NIRS were placed on VL and RF approximately 12 cm above the right knee. Oxy-Hb/Mb signals from NIRS were calculated as 100% at rest, with 0 % being the lowest value during the leg arterial occlusion. Pulmonary gas exchanges (VE, VO<SUB>2</SUB>, VCO<SUB>2</SUB>) were measured with an expiratory gas analyzer. In 10 subjects, muscle oxygenation level in VL decreased linearly until the deoxygenation limiting point (DOLP) -the point in exercise at which the deoxygenation rate decreases noticeably. However, in 2 subjects, the DOLP was not detected, and the muscle oxygenation level decreased linearly until exhaustion. The muscle oxygenation level in RF also decreased linearly until 70%VO<SUB>2</SUB>max, although the deoxygenation rate was smaller than that in VL. Thereafter, the muscle oxygenation level in RF continued to decrease until exhaustion. No DOLP was found in any subjects in RF. Compared with the muscle oxygenation level in RF at any points during the exercise, those in VL were lower until 90%VO<SUB>2</SUB>max (P<0.001) . However, the difference in muscle oxygenation levels between VL and RF at exhaustion was not noted. This study indicated that the patterns of deoxygenation in VL and RF during a ramploaded bicycle exercise were different.

Characteristics of muscle oxygenation in elderly men determined by near infrared spectroscopy / 体力科学

We used near-infrared spectroscopy (NIRS) to study noninvasively the effects of aging on changes in muscle oxygenation during steady bicycle exercise. For the study, 6 healthy young males and 13 healthy elderly male volunteers were recruited. To evaluate the physical fitness level and to determine exercise intensity, the ventilatory threshold (VT) was first measured. As a result, elderly subjects were divided into two groups according to O<SUB>2</SUB> uptake at VT (Elderly-H ; 936.0±26.4, Elderly-L ; 695.3±29.9, Young ; 790.0±51.19 ml) . Secondly we measured muscle oxygenation by NIRS at rest and during exercise at relative work intensities of VT ; 20%, 40%, 60%, 80% and 100%. In all cases muscle oxygenation at rest and during exercise was expressed as a relative value from 100% oxygenation (oxygen capacity) established by thigh occlusion (ischemia) . All subjects showed progressive deoxygenation with increasing intensity. There were no differences between the three groups in muscle oxygenation during exercise at relative work intensity of VT. These data suggest that aging and physical fitness level have no effect on muscle oxygenation below relative work intensity of VT.