Enhanced pulmonary and active skeletal muscle gas exchange during intense exercise after sprint training in men.

1. This study investigated the effects of 7 weeks of sprint training on gas exchange across the lungs and active skeletal muscle during and following maximal cycling exercise in eight healthy males. 2. Pulmonary oxygen uptake (VO2) and carbon dioxide output (VCO2) were measured before and after training during incremental exercise (n = 8) and during and in recovery from a maximal 30 s sprint exercise bout by breath-by-breath analysis (n = 6). To determine gas exchange by the exercising leg muscles, brachial arterial and femoral venous blood O2 and CO2 contents and lactate concentration were measured at rest, during the final 10 s of exercise and during 10 min of recovery. 3. Training increased (P < 0.05) the maximal incremental exercise values of ventilation (VE, by 15.7 +/- 7.1%), VCO2 (by 9.3 +/- 2.1%) and VO2 (by 15.0 +/- 4.2%). Sprint exercise peak power (3.9 +/- 1.0% increase) and cumulative 30 s work (11.7 +/- 2.8% increase) were increased and fatigue index was reduced (by -9.2 +/- 1.5%) after training (P < 0.05). The highest VE, VCO2 and VO2 values attained during sprint exercise were not significantly changed after training, but a significant (P < 0.05) training effect indicated increased VE (by 19.2 +/- 7.9%), VCO2 (by 9.3 +/- 2.1%) and VO2 (by 12.7 +/- 6.5%), primarily reflecting elevated post-exercise values after training. 4. Arterial O2 and CO2 contents were lower after training, by respective mean differences of 3.4 and 21.9 ml l-1 (P < 0.05), whereas the arteriovenous O2 and CO2 content differences and the respiratory exchange ratio across the leg were unchanged by training. 5. Arterial whole blood lactate concentration and the net lactate release by exercising muscle were unchanged by training. 6. The greater peak pulmonary VO2 and VCO2 with sprint exercise, the increased maximal incremental values, unchanged arterial blood lactate concentration and greater sprint performance all point strongly towards enhanced gas exchange across the lungs and in active muscles after sprint training. Enhanced aerobic metabolism after sprint training may contribute to reduced fatigability during maximal exercise, whilst greater pulmonary CO2 output may improve acid-base control after training.

Role of lungs and inactive muscle in acid-base control after maximal exercise.

The pulmonary responses and changes in plasma acid-base status occurring across the inactive forearm muscle were examined after 30 s of intense exercise in six male subjects exercising on an isokinetic cycle ergometer. Arterial and deep forearm venous blood were sampled at rest and during 10 min after exercise; ventilation and pulmonary gas exchange variables were measured breath by breath during exercise and recovery. Immediately after exercise, ventilation and CO2 output increased to 124 +/- 17 1/min and 3.24 +/- 0.195 l/min, respectively. The subsequent decrease in CO2 output was slower than the decrease in O2 intake (half time of 105 +/- 15 and 47 +/- 4 s, respectively); the respiratory exchange ratio was greater than 1.0 throughout the 10 min of recovery. Arterial plasma concentrations of Na+, K+, and Ca2+ increased transiently after exercise. Arterial lactate ion concentration ([La-]) increased to 14-15 meq/l within 1.5 min and remained at this level for the rest of the study. Throughout recovery there was a positive arteriovenous [La-] difference of 4-5 meq/l, associated with an increase in the arteriovenous strong ion difference ([SID]) and by a large increase in the venous Pco2 and [HCO3-]. These findings were interpreted as indicating uptake of La- by the inactive muscle, leading to a fall in the muscle [SID] and increase in plasma [SID], associated with an increase in muscle PCO2. The venoarterial CO2 content difference was 38% greater than could be accounted for by metabolism of La- alone, suggesting liberation of CO2 stored in muscle, possibly as carbamate.(ABSTRACT TRUNCATED AT 250 WORDS)

Torque-velocity relationship in isokinetic cycling exercise.

Seven healthy female subjects performed brief (less than 10 s) periods of maximal exercise on a constant-velocity cycle ergometer, over the functional range of pedaling velocities, and an isometric contraction with each leg. There was an inverse relationship between peak torque and pedal crank velocity in all subjects; isometric torque was (mean +/- SE) 19.8 +/- 8.3% greater than the torque recorded at the slowest velocity of 11 rpm. The torque-velocity relationship was described best by a single exponential equation: y = 189.6 X e-0.0834x, where y is peak torque in Newton . meters and x is crank velocity in revolutions per minute. Peak power was a parabolic function of crank velocity; the data were fitted suitably by a second-order polynomial equation: y = -0.0589x2 + 14.504x + 47.092, where y is peak power in watts and x is crank velocity in revolutions per minute. Maximal peak power occurred at crank velocities ranging from 120 to 160 rpm, when the torque was 0.36 +/- 0.06 of the maximal isometric tension. These results demonstrate the importance of recording velocity in measurements of dynamic maximal power.

Acute exposure of symptomatic steelworkers to sulphur dioxide and carbon dust: effects on mucociliary transport, pulmonary function, and bronchial reactivity.

Nine steel workers participated in controlled exposures to sulphur dioxide alone and sulphur dioxide plus carbon dust (5 ppm and 10 mg/m3, respectively). All were experiencing work related respiratory difficulties. Bronchial clearance was measured using radioaerosol inhalations and external detection. Results were variable and no statistically significant changes were observed. One asthmatic showed a complete cessation of clearance during exposure to sulphur dioxide and carbon dust. Bronchial reactivity was found to be significantly raised after exposure to sulphur dioxide but equivocal results were found after exposure to sulphur dioxide and carbon dust. Pronounced changes in pulmonary function were seen only in the two asthmatic subjects. They could not tolerate the levels, indicating that these threshold limit values are too high, at least for these individuals who showed much greater sensitivity to the pollutants than the others.

Standardization of inhalation provocation tests: influence of nebulizer output, particle size, and method of inhalation.

Standardization of inhalation tests requires a knowledge of factors that will affect the response. We measured the output and particle size of six types of nebulizers used for inhalation tests. Output varied considerably between nebulizers of different types (0.12 to 1.59 ml/min) and to a lesser extent between nebulizers of the same type. Particle size varied between 0.8 and 5.2 micrometer aerodynamic mass median diameter (AMMD). The influence of these two properties on bronchial response to inhaled methacholine was examined. Nebulizer output but not particle size (between 1.3 and 3.6 micrometer AMMD) altered the response. We also examined the effect of change in inspiratory time during inhalation from residual volume to total lung capacity on lung deposition of radiolabeled aerosol and on the provocative concentration of histamine required to reduce the 1-sec forced expiratory volume (FEV1) by 20% (PC20). A reduction in inspiratory time from 8 to 2 sec resulted in a lower total lung dose, relatively more aerosol deposited in central airways, and a higher PC20. The results emphasize the importance of keeping nebulizer output and pattern of breathing constant when performing inhalation provocation tests if consistent results are to be obtained.

Aerosol salbutamol administration by IPPB: lowest effective dose.

This study was conducted to determine whether small doses of salbutamol solution, aerosolised and delivered by intermittent positive-pressure breathing (IPPB), would be as effective as the 5 to 10 mg dose usually recommended for inhalational use. In nine asthmatic subjects we found that there was no significant difference between the peak bronchodilator effect of 1.0, 2.5, and 5.0 mg of salbutamol solution as assessed by FEV1 (P greater than 0.05). The 5 mg dose of salbutamol solution caused a significantly longer duration of effect than the 1.0 mg and smaller doses of salbutamol, but it also caused four of the nine subjects to complain of unwanted effects. In addition, a radiotracer technique in four normal subjects showed that an inverse relationship exists between the amount of aerosol deposited in the lungs and the tidal folume of IPPB. The maximum dose deposited in the lungs was about 10% of that initially present in the nebuliser.

Effect of TLV levels of SO2 and H2 SO4 on bronchial clearance in exercising man.

Pulmonary mucociliary function was assessed following exposure to industrial threshold limit values (TLV) of sulfur dioxide (5 ppm) SO2) and sulphuric acid mist (1 mg/m3 H2SO4). Bronchial clearance was measured in two sets of ten healthy exercising non-smoking adults under control and exposure conditions. A 99mTc-albumen saline aerosol (MMD 3 micrometer) was inhaled as a bolus in late inspiration under controlled conditions to produce reproducible deposition in large airways. Lung retention of radioactivity was quantified using a gamma camera and computer analysis. Clearance was significantly faster (P less than .05) on exposure to both SO2 and H2SO4 compared to control values. Maximum mid-expiratory flow rates (MMFR) were significantly reduced (P less than .01) on exposure to SO2 (mean decrease 8.5%), but only slightly reduced for H2SO4 (1.4%). The speeding in clearance was probably an irritant response in both cases. For SO2 the response appeared predominantly reflex, while H2SO4 showed evidence of a direct effect.

Effects of exercise and eucapnic hyperventilation on bronchial clearance in man.

The effects of exercise and eucapnic hyperventilation on bronchial clearance were assessed in 10 healthy nonsmoking adults. A 99mTc-albumin aerosol was inhaled as a bolus in late inspiration under controlled conditions to produce deposition primarily in large airways. Lung retention of radioactivity was quantified using a gamma camera and subsequent computer analysis. Compared with quiet breathing (control), exercise significantly speeded clearance (P less than 0.05). Resting eucapnic hyperventilation at levels similar to those achieved during exercise produced less speeding. Compared to control conditions these changes may be brought about by a) mechanical effect of increased lung movement, and b) effects on the autonomic nervous system, mediated via the parasympathetic pathway producing stimulation of airway mucus glands and/or sympathetic stimulation of cilia due to exercise-induced catecholamine release.

Pulmonary aerosol deposition in chronic bronchitis: intermittent positive pressure breathing versus quiet breathing.

Quiet breathing by mouth of a 3-mum aerosol was compared with intermittent positive pressure delivery of the same aerosol to the lung in a group of bronchitics. The pattern of lung deposition and the total dose delivered to the lung were measured. The differences between quiet breathing and intermittent positive pressure breathing were found not to be significant (P greater than 0.5). In addition, during similar or greater total ventilation, intermittent positive pressure breathing delivered a mean of 32% less aerosol to the lung than did quiet breathing. These findings suggest that intermittent positive pressure breathing as currently used for aerosol delivery cannot be expected to enhance peripheral deposition of inhaled aerosols in patients with airway obstruction.

Effect of sulphur dioxide on tracheobronchial clearance at rest and during exercise.

Exposure to pollutants may cause injurious effects by impairing mucociliary transport, one of the lung's most important defences. We have studied the effect of sulphur dioxide (SO2) on tracheobronchial clearance (a) at rest and (b) while exercising, by monitoring lung retention of an inhaled radio-aerosol. Clearance was measured in two sets of conditions. 99mTc-albumen aerosol was inhaled as a bolus in late inspiration under controlled conditions to achieve reproducible deposition in large airways. The studies showed: (1) Clearance was highly reproducible in individuals in repeat control studies. (2) Acute exposure to 5 ppm SO2 showed a small transient speeding of mucociliary clearance at rest. (3) (i) Exercise alone speeded clearance significantly (P less than 0.05). (ii) Exercising in 5 ppm SO2 showed a significant speeding of clearance (P less than 0.05) beyond that found in air breathing exercise controls. (4) Pulmonary function tests showed no significant change except a decrease in flow rate (MMEF) in both (a) and (b) studies (P less than 0.01).