Skeletal muscle metabolism during exercise and recovery in patients with respiratory failure.

BACKGROUND--Patients with respiratory failure have early fatiguability which may be due to limitation of oxygen supply for oxidative (mitochondrial) ATP synthesis. Skeletal muscle in exercise and recovery was studied to examine the effect of chronic hypoxia on mitochondrial activity in vivo. METHODS--The skeletal muscle of five patients with respiratory failure (PaO2 < 9 kPa) was studied by phosphorus-31 magnetic resonance spectroscopy and compared with 10 age and sex matched controls. Patients lay in a 1.9 Tesla superconducting magnet with the gastrocnemius muscle overlying a six cm surface coil. Spectra were acquired at rest, during plantar flexion exercise, and during recovery from exercise. Relative concentrations of inorganic phosphate (Pi), phosphocreatine (PCr) and ATP were measured from peak areas, and pH and free ADP concentration were calculated. For the start of exercise, the rates of PCr depletion and estimated lactic acid production were calculated. For the post exercise recovery period, the initial rate of PCr recovery (a quantitative measure of mitochondrial ATP synthesis), the apparent Vmax for mitochondrial ATP synthesis (calculated from initial PCr resynthesis and the end exercise ADP concentration which drives this process), and the recovery half times of PCr, Pi, and ADP (also measures of mitochondrial function) were determined. RESULTS--Considerably greater and faster PCr depletion and intracellular acidosis were found during exercise. This is consistent with limitation of oxygen supply to the muscle and might explain the early fatiguability of these patients. There was no abnormality in recovery from exercise, however, suggesting that mitochondria function normally after exercise. CONCLUSIONS--These results are consistent with one or more of the following: (a) decreased level of activity of these patients; (b) changes in the fibre type of the muscle; (c) decreased oxygen supply to the muscle during exercise but not during recovery. They are not consistent with an intrinsic defect of mitochondrial ATP synthesis in skeletal muscle in respiratory failure.     

Expiratory muscle training and sensation of respiratory effort during exercise in normal subjects.

BACKGROUND--The sensation of respiratory effort may increase as expiratory muscles become fatigued during expiratory loading. A study was performed to determine whether expiratory muscle training (EMT) affects the sensation of respiratory effort during exercise in healthy subjects. METHODS--Six subjects performed EMT for 15 minutes twice daily for four weeks using a pressure threshold device; another six subjects served as a control group. The expiratory threshold was set at 30% of the individual's maximum expiratory mouth pressure (PEmax). The sensation of respiratory effort was evaluated during a progressive exercise test using the Borg scale. RESULTS--After EMT PEmax increased by 25% in the training group. The Borg score increased as exercise grade increased before and after EMT, but scores for each grade were lower after EMT. Minute ventilation during exercise decreased after EMT, as did the breathing frequency during exercise, while the expiratory time increased. Although there was no difference in the relationship between Borg score and minute ventilation before or after EMT, the curve shifted to a lower Borg score after EMT. There were no changes in PEmax, Borg score, minute ventilation, or breathing pattern after the four week study period in the control group. CONCLUSION--These findings suggest that EMT increases expiratory muscle strength and reduces the sensation of respiratory effort during exercise, presumably by reducing minute ventilation.     

Effects of specific exercise instructions on abdominal muscle activity during trunk curl exercises

STUDY DESIGN: A repeated-measures, counterbalanced design. OBJECTIVES: To test whether subjects could learn and retain the ability to alter the relative activity of abdominal muscle groups when performing trunk curl exercises. BACKGROUND: Although trunk curl exercises are widely prescribed, a disadvantage of trunk curls is that they primarily activate rectus abdominis, while the internal and external oblique abdominis muscles are considered to be more important contributors to lumbar stability. METHODS AND MEASURES: A convenience sample of 25 subjects performed trunk curl exercises in accordance with 3 different sets of instructions: nonspecific instructions (NS), instructions intended to emphasize rectus abdominis activity (RE), and instructions intended to emphasize oblique abdominis activity (OE). Electromyographic (EMG) activity was recorded from the upper and lower rectus and the internal and external oblique abdominis muscles while a physical target was used to insure that the trunk was raised to the same height for all conditions. Normalized root-mean-square EMG amplitude measures were used to test for instruction-dependent changes in the relative EMG activity of the rectus and oblique muscle groups. RESULTS: Following a single, brief, instruction session, subjects performing trunk curls had significantly greater normalized oblique:rectus EMG ratios when following OE instructions (mean [+/- SD] oblique-rectus ratio, 1.45 +/- 0.34) than when following RE (mean [+/- SD] oblique-rectus ratio, 0.76 +/- 0.24) or NS (mean [ISD] oblique-rectus ratio, 0.63 +/- 0.23) instructions. Retesting 1 week later indicated that subjects retained this skill. CONCLUSIONS: With minimal instruction, subjects are able to volitionally alter the relative activity of the oblique and rectus abdominis muscles when performing trunk curls. Incorporating instructions emphasizing oblique abdominis activity into lumbar stabilization programs appears promising and has potential advantages over other approaches to altering abdominal muscle activity during trunk     

Effect of salmeterol/fluticasone propionate on airway inflammation in COPD: a randomised controlled trial

BACKGROUND: Airway inflammation in chronic obstructive pulmonary disease (COPD) is characterised by infiltration of CD8+ T cells and CD68+ macrophages and an increased number of neutrophils, whereas few studies have described the presence of eosinophils. Although the anti-inflammatory effects of corticosteroids in stable COPD are unclear, recent studies suggest that combination therapy could be beneficial. A study was therefore undertaken to evaluate combined salmeterol/fluticasone propionate (SFC) and fluticasone propionate (FP) alone on inflammatory cells in the airways of patients with COPD. METHODS: Patients were treated in a randomised, double blind, parallel group, placebo-controlled trial with either a combination of 50 microg salmeterol and 500 microg FP twice daily (SFC, n = 19, 19 men, mean age 62 years), 500 microg FP twice daily (n = 20, 15 men, mean age 64 years) or placebo (n = 21, 17 men, mean age 66 years) for 3 months. At the start and end of treatment bronchoscopy with bronchial biopsies was performed and the numbers of CD8+ T lymphocytes, CD68+ macrophages, neutrophils and eosinophils were measured. RESULTS: CD8+ cells were significantly reduced by SFC compared with placebo (difference -98.05 cells/mm(2); 95% CI -143.14 to -52.9; p<0.001). Such a marked effect was not seen with FP alone (-44.67 cells/mm(2); 95% CI -90.92 to 1.57; p = 0.06). CD68+ macrophages were also reduced by SFC compared with placebo (difference -31.68 cells/mm(2); 95% CI -61.07 to -2.29; p = 0.03) but not by FP. SFC did not significantly change neutrophils and eosinophils compared with placebo. CONCLUSIONS: SFC has airway anti-inflammatory effects not seen with inhaled corticosteroids alone.     

Effect of salbutamol on lung function and chest wall volumes at rest and during exercise in COPD

BACKGROUND: Inhaled bronchodilators can increase exercise capacity in chronic obstructive pulmonary disease (COPD) by reducing dynamic hyperinflation, but treatment is not always effective. This may reflect the degree to which the abdomen allows dynamic hyperinflation to occur.Method: A double blind, randomised, crossover trial of the effect of 5 mg nebulised salbutamol or saline on endurance exercise time was conducted in 18 patients with COPD of mean (SD) age 67.1 (6.3) years and mean (SD) forced expiratory volume in 1 second (FEV1) of 40.6 (15.0)% predicted. Breathing pattern, metabolic variables, dyspnoea intensity, and total and regional chest wall volumes were measured non-invasively by optoelectronic plethysmography (OEP) at rest and during exercise. RESULTS: Salbutamol increased FEV1, forced vital capacity (FVC) and inspiratory capacity and reduced functional residual capacity (FRC) and residual volume significantly. OEP showed the change in resting FRC to be mainly in the abdominal compartment. Although the mean (SE) end expiratory chest wall volume was 541 (118) ml lower (p<0.001) at the end of exercise, the endurance time was unchanged by the bronchodilator. Changes in resting lung volumes were smaller when exercise duration did not improve, but FEV1 still rose significantly after active drug. After the bronchodilator these patients tried to reduce the end expiratory lung volume when exercising, while those exercising longer continued to allow end expiratory abdominal wall volume to rise. The change to a more euvolumic breathing pattern was associated with a lower oxygen pulse and a significant fall in endurance time with higher isotime levels of dyspnoea. CONCLUSIONS: Nebulised salbutamol improved forced expiratory flow in most patients with COPD, but less hyper-nflated patients tried to reduce the abdominal compartmental volume after active treatment and this reduced their exercise capacity. Identifying these patients has important therapeutic implications, as does an understanding of the mechanisms that control chest wall muscle recruitment.     

Correlation between alpha rhythms and natural killer cell activity during yogic respiratory exercise

In eight yoga instructors, we examined changes in brain rhythms and natural killer cell activity (NK activity) during yoga exercises. We found that the practice of all three exercises studied resulted in increased alpha activity. There were no apparent changes in NK activity after a series of postural (asana) and meditative (mantra) exercises. During respiratory exercises (pranayama), however, changes in NK activity were observed in the eight subjects, positively correlating to increases in alpha frequencies (r = 0.83, p < 0.02). Copyright © 2001 John Wiley & Sons, Ltd.     

Yoga in Burn: Role of pranayama breathing exercise on pulmonary function,respiratory muscle activity and exercise tolerance in full-thickness circumferential burns of the chest

BackgroundCircumferential burn of chest (CBC) is a significant type of burn and considers as a major cause of restrictive lung disease (RLD). Patient who has CBC with RLD leads to respiratory symptoms such as breathing difficulty, airway obstruction, reduced exercise capacity and altered pulmonary functions. However, studies examining the role of pranayama breathing exercise on pulmonary function, respiratory muscle activity and exercise tolerance in full thickness circumferential burn of chest are lacking.ObjectiveTo find the short term effects of pranayama breathing exercise on pulmonary function, respiratory muscle activity and exercise tolerance in full thickness circumferential burns of chest.MethodsThrough simple random sampling method thirty subjects (N = 30) with RLD following CBC were allocated to pranayama breathing exercise group (PBE-G; n = 15) and conventional breathing exercise group (CBE-G; n = 15). They received pranayama breathing exercise and conventional breathing exercise for 4 weeks respectively. All the subjects received chest mobility exercise as common treatment. Primary (Numeric Pain Rating Scale - NPRS, forced expiratory volume (FEV1), forced vital capacity (FVC) and maximum voluntary ventilation (MVV) and secondary (Electromyogram of sternocleidomastoid, scalene, external intercostal and diaphragm muscle, 6 min walk test & Global Rating of Change - GRC) outcome measures were measured at baseline, after four weeks and after three months follow up.ResultsBaseline demographic and clinical variables show homogenous distribution between the groups (p > 0.05). Four weeks following different breathing exercises, PBE-G group shows more significant changes in pain intensity, pulmonary function, respiratory muscle activity, exercise tolerance and global rating of change than CBE-G group (p ≤ 0.05) at four weeks and three months follow up.ConclusionBoth groups showed improvement over time. However, differences between the groups were noticed small. Still physiotherapy management, which included pranayama breathing exercises with chest mobilization program, had an effective strategy in the treatment of restrictive lung disease following circumferential burn of chest.     

The effects of exercise type and elbow angle on vertical ground reaction force and muscle activity during a push-up plus exercise

Background

Proper alignment of the scapula during upper extremity motion is important in maintaining shoulder joint function and health. Push-up plus exercise is considered as one of the best exercise to strengthen the muscles that stabilize the scapula. The purpose of the study is to examine the effects of push-up plus variants and elbow position on vertical ground reaction force and electromyographical activity of four shoulder muscles during concentric contraction.

Methods

A total of 22 healthy subjects volunteered for the study. Each of the subjects performed both modified and traditional push-up plus. Modified push-up plus was performed with both knees and hands touching the ground while the traditional push-up plus was executed with hands and feet contacting the ground. Electromyography (EMG) of the upper trapezius (UT), lower trapezius (LT), infraspinatus (INFRA), and serratus anterior (SA), and vertical ground reaction forces (vGRF) were collected.

Results

The traditional push-up plus exhibited higher EMG activity in all muscles tested (P < .05) and vertical ground reaction force (P < .001) compared to modified push-up plus. The highest difference in EMG activity between the two exercises was observed with the Serratus Anterior muscle (22%). Additionally, the traditional push-up plus presented a higher vGRF compared to the modified push-up plus (P < .001) by 17%. The SA had the greatest EMG activity compared to the other muscles tested during the concentric phase of the traditional push-up plus, and this did not occur during the plus phase of the exercise.

Conclusion

The highest activity of the serratus anterior occurred at 55° of elbow extension during the concentric phase of the traditional PUP and not at the plus phase of the exercise. This suggests that when prescribing an exercise to target the serratus anterior, a traditional push-up is adequate and the plus-phase is not necessary. However, for patients that cannot perform a traditional push-up, the modified push-up plus would be a great alternative to strengthen their serratus anterior.     

Pressure in the erector spinae muscle during exercise

The microcapillary infusion method was evaluated in recording intramuscular pressure during isometric and concentric exercise of the erector spinae muscle. Intramuscular pressure at rest was 6.1 (SD = 1.4) mm Hg without infusion and 8.3 with an infusion rate of 1.5 ml/hour. When the subject experienced muscle fatigue during exercise, the muscle relaxation pressure had increased to 14 mm Hg. The erector spinae muscle was found to be heavily loaded during exercise with an average muscle contraction pressure of 175 mm Hg. Recording of intramuscular pressure in the erector spinae muscle during exercise tests can be an additional method in the study of ergonomics and biomechanics of the spine as well as in the diagnosis of chronic compartment syndrome in this muscle.     

Effect of parathyroidectomy on respiratory muscle strength in uremic myopathy

We report the case of a uremic dialysis patient with severe secondary hyperparathyroidism, proximal muscle weakness and impaired respiratory muscle strength, the latter being assessed by maximal inspiratory pressure. After subtotal parathyroidectomy, we observed a marked improvement in respiratory muscle strength (27 vs. 87 cm H2O) and disappearance of proximal muscle weakness.     

Supplemental oxygen during pulmonary rehabilitation in patients with COPD with exercise hypoxaemia

BACKGROUND: Supplemental oxygen in patients with chronic obstructive pulmonary disease (COPD) and exercise hypoxaemia improves exercise capacity and dyspnoea. However, the benefit of oxygen during pulmonary rehabilitation in these patients is still unknown. METHODS: Twenty five patients with stable COPD (mean (SD) forced expiratory volume in one second (FEV(1)) 0.76 (0.29) l and 30.0 (9.89)% predicted, arterial oxygen tension (PaO(2)) 8.46 (1.22) kPa, arterial carbon dioxide tension (PaCO(2)) 6.32 (1.01) kPa) and significant arterial desaturation on exercise (82.0 (10.4)%) were entered onto a pulmonary rehabilitation programme. Patients were randomised to train whilst breathing oxygen (OT) (n = 13) or air (AT) (n = 12), both at 4 l/min. Assessments included exercise tolerance and associated dyspnoea using the shuttle walk test (SWT) and Borg dyspnoea score, health status, mood state, and performance during daily activities. RESULTS: The OT group showed a significant reduction in dyspnoea after rehabilitation compared with the AT group (Borg mean difference -1.46 (95% CI -2.72 to -0.19)) but there were no differences in other outcome measures: SWT difference -23.6 m (95% CI -70.7 to 23.5), Chronic Respiratory Disease Questionnaire 3.67 (95% CI -7.70 to 15.1), Hospital Anxiety and Depression Scale 1. 73 (95% CI -2.32 to 5.78), and London Chest Activity of Daily Living Scale -2.18 (95% CI -7.15 to 2.79). At baseline oxygen significantly improved SWT (mean difference 27.3 m (95% CI 14.7 to 39.8) and dyspnoea (-0.68 (95% CI -1.05 to -0.31)) compared with placebo air. CONCLUSIONS: This study suggests that supplemental oxygen during training does little to enhance exercise tolerance although there is a small benefit in terms of dyspnoea. Patients with severe disabling dyspnoea may find symptomatic relief with supplemental oxygen.     

Effect of exercise intensity on skeletal muscle AMPK signaling in humans

The effect of exercise intensity on skeletal muscle AMP-activated protein kinase (AMPK) signaling and substrate metabolism was examined in eight men cycling for 20 min at each of three sequential intensities: low (40 +/- 2% VO(2) peak), medium (59 +/- 1% VO(2) peak), and high (79 +/- 1% VO(2) peak). Muscle free AMP/ATP ratio only increased at the two higher exercise intensities (P < 0.05). AMPK alpha 1 (1.5-fold) and AMPK alpha 2 (5-fold) activities increased from low to medium intensity, with AMPK alpha 2 activity increasing further from medium to high intensity. The upstream AMPK kinase activity was substantial at rest and only increased 50% with exercise, indicating that, initially, signaling through AMPK did not require AMPK kinase posttranslational modification. Acetyl-CoA carboxylase (ACC)-beta phosphorylation was sensitive to exercise, increasing threefold from rest to low intensity, whereas neuronal NO synthase (nNOS) micro phosphorylation was only observed at the higher exercise intensities. Glucose disappearance (tracer) did not increase from rest to low intensity, but increased sequentially from low to medium to high intensity. Calculated fat oxidation increased from rest to low intensity in parallel with ACC beta phosphorylation, then declined during high intensity. These results indicate that ACC beta phosphorylation is especially sensitive to exercise and tightly coupled to AMPK signaling and that AMPK activation does not depend on AMPK kinase activation during exercise.     

Optimization of respiratory muscle relaxation during mechanical ventilation

The authors calculated the active work of inspiration (Wp) and the inspiratory muscle pressure-time product (integral of Pmus.dt) in seven patients undergoing mechanical ventilation (MV). This was done by comparing the areas under the inflation pressure-volume and inflation pressure-time curves generated when the patient was contributing to the work of ventilation with those following sedation, when inspiratory muscle activity was absent (defined as absence of diaphragmatic EMG activity and of palpable accessory muscle contraction). Inspiratory muscle inactivity could be predicted by the observation of a smooth rise in inflation pressure that was highly reproducible from breath to breath. Relaxation was present without sedation during MV in the control mode with inspiratory flow rates above 65 1/min. In the assist mode (AMV), both Wp and integral of Pmus.dt were significantly (P less than 0.05) greater than in the control (CMV) mode. Reducing trigger sensitivity during AMV further increased Wp and integral of Pmus.dt (P less than 0.05). During AMV and CMV Wp and integral of Pmus.dt decreased with increasing rate of inspiratory flow delivered by the ventilator. With AMV at low trigger sensitivity and low flow rates, Wp approached 65% of the total inspiratory work. The authors conclude that inspiratory muscle activity can be substantial during MV, particularly during AMV at low trigger sensitivity and flow. Monitoring of inflation pressure is a simple means of determining the degree of inspiratory muscle rest during MV.     

Uraemic muscle metabolism at rest and during exercise

The effect of chronic renal failure and the accompanying hyperphosphataemiaon muscle metabolism at rest and during exercise was examinedin a group of undialysed patients suffering from chronic renalfailure. ³¹P magnetic resonance spectroscopy was used to measureintracellular high-energy phosphates in resting muscle as wellas changes in the concentrations of these metabolites duringexercise and recovery from exercise. In resting muscle, cell[Pi] rose with plasma [Pi], and free [ADP] changed such thatthe phosphorylation potential ([ATP]/([ADP]x[Pi])), which probablycontrols mitochondrial oxidation in resting muscle, was preserveddespite a wide variation in cell [Pi]. The maximal oxidativecapacity of the muscle was calculated from the kinetics of phosphocreatinerecovery after exercise. There was no reduction in uraemic muscleoxidative capacity compared to control muscle. This contrastswith our finding of a reduction in the mitochondrial oxidativecapacity in the muscle of patients established on dialysis,suggesting that a substance crucial for mitochondrial functionor substrate supply to mitochondria is removed by dialysis.