Increased load on the respiratory muscles in obstructive sleep apnea

We wished to quantify, in patients with obstructive sleep apnoea (OSA), the activity of the respiratory muscles in relation to upper airway occlusion and patency in sleep. We hypothesized that particular levels of neuromuscular activation are directly associated with upper airway patency. 21 patients with previously diagnosed OSA and 21 healthy control subjects underwent respiratory muscle testing and polysomnography. Neural respiratory drive, as measured by the electromyogram of the diaphragm (EMG_di) was elevated in the obese OSA patients, awake and supine (13.1(5.6)%max), compared to normal subjects (mean (SD) 8.1(2.3)%max, p < 0.01). During unobstructed breathing in sleep (stage N2) normal subjects had an EMG_di of 7.7(3.9) compared to 22.8(19.2)%max in the OSA group (p < 0.001). Prior to airway occlusion, EMG_{submandibular} and EMG_di dropped markedly, and then, following occlusion, increased progressively to their highest levels at airflow onset. Patients with OSA require specific and increased levels of neural respiratory drive to sustain ventilation in sleep.     

Respiratory muscle function in trained and untrained adolescents during short-term high intensity exercise

Summary The breathing pattern and respiratory muscle function were investigated in ten trained and ten untrained adolescents (aged 15–16 years) while undergoing an incremental intensity exercise test on a cycle ergometer up to 80% maximal oxygen consumption ( O_2max), maintained to exhaustion. Before and after exercise, maximal inspiratory (P _{I max}) and expiratory (P _{E max}) pressures were measured at residual volume and total lung capacity, respectively. During exercise, the breathing pattern [tidal volume (V _T), respiratory frequency (f _R), ventilation] and the relative contribution of ribcage and abdomen to V _T were assessed using inductance plethysmography. Electromyographic activities of transversus abdominis (EMG_tr) and diaphragm (EMG_di) muscles were recorded and analysed during exercise. There was a difference in the change in the pattern of breathing between the trained and the untrained group; f _R increased significantly (P < 0.05) at 40% O_2maxfor the untrained group. Before exercise there was no difference in the maximal respiratory pressures. Up to 60% and 80% O_2max, transversus abdominis and diaphragm muscle activity increased significantly in the trained adolescents. However in this group, no evidence of respiratory muscle fatigue appeared: P _{I max}, P _{E max} and the frequency spectrum of EMG_tr and EMG_di were not altered by exercise up to exhaustion. In the untrained group, who had high ventilatory responses, expiratory muscle function was unchanged at the end of the exercise, but signs of inspiratory muscle fatigue appeared in that P _{I max} was significantly decreased after exercise.     

The relation of ventilation to metabolic rate during moderate exercise in man

Summary To characterize more precisely the relationship between ventilation (V _E) and CO₂ output (VCO₂) during incremental exercise, 35 healthy males were studied at rest and during upright cycle ergometry, with the work rate incremented every 4 min up to each subject's anaerobic threshold ( _an). Twenty-one subjects had arterial blood sampled at rest and in the steady state at each work rate to determine the relationship between physiological dead space ventilation (V _D) and VCO₂. At these work rates arterial PCO₂ was regulated at the resting, control value. V _E (BTPS) was linearly related to VCO₂ from rest to _an with a slope of 24.6. However, the regression had a significant positive intercept of 3.2 L·min^–1. This causes the ventilatory equivalent for CO₂ (i.e., V _E/VCO₂) to decrease with increasing work rates. V _D also increased linearly with increasing VCO₂. However, this was consequent to increased breathing frequency as V _D remained constant. Thus, the observed fall in V _E/VCO₂ with increasing work rates is due to the positive intercept but the inherent relationship between V _E and VCO₂, reflected by the linear regression slope, remains unchanged from rest through moderate exercise.This investigation was supported by National Institutes of Health Grant HL-11907     

An examination of exercise mode on ventilatory patterns during incremental exercise

Both cycle ergometry and treadmill exercise are commonly employed to examine the cardiopulmonary system under conditions of precisely controlled metabolic stress. Although both forms of exercise are effective in elucidating a maximal stress response, it is unclear whether breathing strategies or ventilator efficiency differences exist between exercise modes. The present study examines breathing strategies, ventilatory efficiency and ventilatory capacity during both incremental cycling and treadmill exercise to volitional exhaustion. Subjects (n = 9) underwent standard spirometric assessment followed by maximal cardiopulmonary exercise testing utilising cycle ergometry and treadmill exercise using a randomised cross-over design. Respiratory gases and volumes were recorded continuously using an online gas analysis system. Cycling exercise utilised a greater portion of ventilatory capacity and higher tidal volume at comparable levels of ventilation. In addition, there was an increased mean inspiratory flow rate at all levels of ventilation during cycle exercise, in the absence of any difference in inspiratory timing. Exercising [(V)\dot]_\textE / [(V)\dot]\textCO₂ {{\dot{V}_{\text{E}} }/ {\dot{V}{\text{CO}}_{2} }} slope and the lowest [(V)\dot]_\textE / [(V)\dot]\textCO₂ {{\dot{V}_{\text{E}} }/ {\dot{V}{\text{CO}}_{2} }} value, was lower during cycling exercise than during the treadmill protocol indicating greater ventilatory efficiency. The present study identifies differing breathing strategies employed during cycling and treadmill exercise in young, trained individuals. Exercise mode should be accounted for when assessing breathing patterns and/or ventilatory efficiency during incremental exercise.     

Breathing mechanics during exercise with added dead space reflect mechanisms of ventilatory control

Small increases in external dead space (V_D) augment the exercise ventilatory response via a neural mechanism known as short-term modulation (STM). We hypothesized that breathing mechanics would differ during exercise, increased V_D and STM. Men were studied at rest and during cycle exercise (10–50 W) without (Control) and with added V_D (200–600 ml). With added V_D, V_T increased via increased end-inspiratory lung volume (EILV), with no change in end-expiratory lung volume (EELV), indicating recruitment of inspiratory muscles only. With exercise, V_T increased via both decreased EELV and increased EILV, indicating recruitment of both expiratory and inspiratory muscles. A significant interaction between the effects of exercise and V_D on mean inspiratory flow indicated that the augmented exercise ventilatory response with added V_D (i.e. STM) resulted from increased drive to the inspiratory muscles. These results reveal different patterns of respiratory muscle recruitment among experimental conditions. Hence, we conclude that fundamental differences exist in the neural control of ventilatory responses during exercise, increased V_D and STM.     

Sexual and postural differences in cardioventilatory responses during and after breath holding at rest

Summary Twelve subjects (six men, six women) were studied in resting conditions for simple breath holding (BH) in either the supine or upright position. Ventilation (V _T, , f _r) heart rate (f _c) and arterial blood pressure (ABP) were recorded or measured in steady state and then transiently during BH and its recovery. Each subject performed seven BH in the supine position and two in the upright position. Several criteria were used for f _c data analysis. During BH, in either the supine or upright position, no change in heart rate was observed, but subjects taken individually may exhibit some significant cardiac responses (tachycardia or bradycardia) for all the tests. In contrast, an increase in mean ABP is always observed, with different patterns in males and females. The upright position allows the responses to be greater, more rapid and significant. As a general rule, males have larger and slower responses than females. After BH, there is a ventilatory cost of apnea which is more important in males. However the delay in repayment of the ventilatory deficit observed during BH is very short (about 40 s): ventilatory and cardiac recovery are complete within 120 s. The results support the ideas that, (1) cardiac responses during BH are dependent on pulmonary physical conditions and metabolic levels before BH, (2) cardiac changes during recovery are, at least in great part, due to the concomitant hyperventilation.     

The influence of body position on maximal performance in cycling

Summary Six healthy male subjects performed a 3-min supramaximal test in four different cycling positions: two with different trunk angles and two with different saddle-tube angles. Maximal power output and maximal oxygen uptake (VO_2max) were measured. Maximal power output was significantly higher in a standard sitting (SS, 381 W, SD 49) upright position compared to all other positions: standard racing (SR, 364 W, SD 49), recumbent backwards (RB, 355 W, SD 44) and recumbent forwards (RF, 341 W, SD 54). Although VO_2max was also highest in SS (4.31 l · min^–1, SD 0.5) upright position, the differences in VO_2max were not significant (SR, 4.21 · min^–1, SD 0.53; RB, 4.17 l · min^–1, SD 0.58; RF, 4.11 l · min^–1, SD 0.66). It is concluded that (supra)maximal tests on a cycle ergometer should be performed in a sitting upright position and not in a racing position. In some cases when cycling on the road, higher speeds can be attained when sitting upright. This is especially true when cycling uphill when high power must be generated to overcome gravity but the road speed, and hence the power required to overcome air resistance, is relatively low.     

Central and peripheral components of diaphragmatic fatigue during inspiratory resistive load in cats

The development of fatigue was investigated in the diaphragm of anaesthetized, tracheostomized, spontaneously breathing cats during restricted air flow. Ventilation, transdiaphragmatic pressure (P_di), integrated electrical activity of diaphragm (E_di) and phrenic nerve (E_ph) were measured simultaneously and expressed as a percentage of values at unloaded breathing. Inspiratory loads were 60, 70 and 80% of P_{di max}. The P_{di max} was measured by airway occlusion at functional residual capacity. The duration of loads was 40–60 min. The diaphragmatic fatigue developed only during heavy inspiratory loading (80% P_{di max}). During the first 10 min of heavy load P_di, E_di and E_ph increased to 905 ± 60%, 248 ± 20% and 229 ± 24%, respectively (P < 0.01), and then began to fall gradually. Ventilation declined to 39 ± 3% after 60 min of heavy load (P < 0.01), resulting in acute hypercapnia and hypoxia. Initial fatigue appeared as a decrease in P_di (to 781 ± 63%) and parallel decline in E_di (to 233 ± 21%) after 30 min of load (P < 0.05). Phrenic nerve activity did not change during this stage. These data suggest a peripheral basis of diaphragmatic fatigue, related to disorders in neuromuscular transmission. After 60 min of heavy load, P_di fell to 675 ± 49%, E_di declined to 209 ± 28% and E_ph decreased to 189 ± 25%. We interpret the decrease in phrenic nerve activity as a weakening of central inspiratory drive and development of the central component of diaphragmatic fatigue in the last stage.     

Upright position mechanical ventilation: An alternative strategy for ALI/ARDS patients?

Use of body positioning to improve oxygenation in mechanically ventilated patients with acute lung injury (ALI) and acute respiratory distress syndrome (ARDS) has been well documented. However, neither prone position ventilation nor side lying ventilation has been reported to improve the survival. Whether there is a body position superior to routine supine position or other positions as therapeutic adjunct for ventilated patients with ALI and ARDS? We propose the hypothesis that upright position ventilation may be helpful to improve oxygenation and benefit patients with ALI/ARDS. According to the existing physiologic and pathophysiologic data of upright position investigation, we suppose that improvement of V/Q matching, increased functional residual capacity, alveolar recruitment, accelerated diaphragm recovery, early gastric emptying and enteric feeding may be a potential protect mechanism of upright position ventilation. Whether this can be translated into improvement in patient outcome should be further tested in clinical trial.     

Transient hypoxia: Ventilatory response after vagotomy and during artificial phasic inflation

The early ventilatory response to transient hypoxia was examined in the anaesthetized rabbit. In intact spontaneously breathing animals, an increase in tidal volume (V _T) with an accompanying slight increase in inspiratory duration (T _I) and a decrease in the expiratory duration (T _E) was observed. After vagotomy, the ventilatory response was distinguished by a greater increase inV _T and a significant decrease inT _I andT _E.In another group of artificially ventilated rabbits, an increase in inspiratory volume with a simultaneous decrease in breathing frequency was found to involve a smaller reflex increase in phrenic inspiratory discharge after onset of transient hypoxia.These observations suggest that afferents from pulmonary vagal stretch receptors inhibit those from arterial chemoreceptors.     

Ventilatory response of prepubertal boys and adults to carbon dioxide at rest and during exercise

Summary The aim of this study was to determine whether the greater ventilation in children at rest and during exercise is related to a greater CO₂ ventilatory response. The CO₂ ventilatory response was measured in nine prepubertal boys [10.3 years (SD 0.1)] and in 10 adults [24.9 years (SD 0.8)] at rest and during moderate exercise ( CO₂ = 20 ml·kg^–1·min^–1) using the CO₂-rebreathing method. Three criteria were measured in all subjects to assess the ventilatory response to CO₂: the CO₂ sensitivity threshold (Th), which was defined as the value of end titalPCO₂ (P _ETCO₂) where the ventilation increased above its steady-state level; the reactivity slope expressed per unit of body mass (SBM), which was the slope of the linear relation between minute ventilation ( _E) andP _ETCO₂ above Th; and the slope of the relationship between the quotient of tidal volume (V _T) and inspiration time (t _I) andP _ETCO₂ (V _T ·t _I ^–1 ·P _ETCO₂ ^–1) values above Th. The _E,V _T, breathing frequency (f _R), oxygen uptake ( O₂), and CO₂ production ( CO₂) were also measured before the CO₂-rebreathing test. The following results were obtained. First, children had greater ventilation per unit body weight than adults at rest (P<0.001) and during exercise (P<0.01). Second, at rest, onlyV _T ·t _I ^–1 ·P _ETCO₂ ^–1 was greater in children than in adults (P<0.001). Third, during exercise, children had a higher S_BM (P < 0.02) andV _T ·t _I ^–1 ·P _ETCO₂ ^–1 (P<0.001) while Th was lower (P<0.02). Finally, no correlation was found between _E/ CO₂ and Th while a significant correlation existed between _E/ CO₂ and S_BM (adults,r=0.79,P<0.01; children,r=0.73,P<0.05). We conclude that children have, mainly during exercise, a greater sensitivity of the respiratory centres than adult. This greater CO₂ sensitivity could partly explain their higher ventilation during exercise, though greater CO₂ production probably plays a role at rest.     

Reduced arterial O2 saturation during supine exercise in highly trained cyclists

Performance of intense dynamic exercise in highly trained athletes is associated with a reduced arterial haemoglobin saturation for O₂ (SaO ₂) and lower arterial PO ₂ (PaO ₂). We hypothesized that compared with upright exercise, supine exercise would be accompanied by a smaller reduction in SaO ₂ because of a lower maximal O₂ uptake (VPO _2max) and/or a more even ventilation–perfusion distribution. Eight elite bicyclists completed progressive cycle ergometry to exhaustion in both positions with concomitant determinations of ventilatory data, arterial blood gases and pH. During upright cycling VPO _2max averaged 75±1.6 mL O₂ min^-1 kg^-1 (±SEM) and it was 10.6±1.7% lower during supine cycling (P<0.001). Also the maximal pulmonary and alveolar ventilation were lower during supine cycling (by 15±2% and 21±3%, respectively; P< 0.001) which related to a 0.8±0.1 L lower tidal volume (P<0.001). In all subjects and independent of work posture PaO ₂ and SaO ₂ decreased from rest to exhaustion (from 99±3 to 82±2 Torr and 98.1±0.2 to 95.2±0.4%, respectively; P<0.001); alveolar–arterial PO ₂ difference increased from 6±2 to 37±3 Torr in both body positions. At exhaustion arterial PCO ₂ was lower in upright than in supine (33.4±0.6 vs. 35.9±0.9 Torr; P<0.01), suggesting a greater relative hyperventilation in upright. Arterial pH was similar in upright and supine at rest (both 7.41±0.01) and at exhaustion (7.31±0.01 vs. 7.32±0.01, respectively). We conclude that despite a lower VPO _2max and supposedly an improved ventilation–perfusion distribution, altering body position from upright to supine does not influence arterial O₂ desaturation during intense exercise.     

Ventilatory and occlusion pressure response to CO2 and hypoxia with resistive loads

Steady-state responses to hyperoxic hypercapnia and eucapnic hypoxia were measured both as minute ventilation (V_E) and as inspiratory mouth occlusion pressure (P_0.1) with and without 25 cm H₂O/l/s added resistance (R). Reduction in slope of the ventilatory response to CO₂ with R was highly significant in all 3 subjects whereas the response to hypoxia was barely significantly reduced in 1 subject and not significantly decreased in two. Although P_0.1 was higher with than without R under all conditions, the slope of the P_0.1 response to CO₂ with R was not increased in two subjects and only slightly increased in the third. The slope of the P_0.1 response to hypoxia was significantly greater in all subjects with R. Expiratory reserve volume was increased with R but the change was the same with hypoxia and hypercapnia. We conclude that ventilation is better maintained with resistive loading during hypoxia than during hypercapnia and that this results from a greater force output of inspiratory muscles as reflected by a higher P_0.1. This suggests a greater neural output to these muscles.     

Difference in human cardiovascular response between upright and supine recovery from upright cycle exercise

Cardiovascular responses were examined in seven healthy male subjects during 10 min of recovery in the upright or supine position following 5 min of upright cycle exercise at 80% peak oxygen uptake. An initial rapid decrease in heart rate (f _c) during the early phase of recovery followed by much slower decrease was observed for both the upright and supine positions. The average f _c at the 10th min of recovery was significantly lower (P < 0.05) in the supine position than in the upright position, while they were both significantly greater than the corresponding pre-exercise levels (each P < 0.05). Accordingly, the amplitude of the high frequency (HF) component of R-R interval variability (by spectrum analysis) in both positions was reduced with a decrease in mean R-R interval, the relationship being expressed by a regression line – mean R-R interval = 0.006 × HF amplitude + 0.570 (r = 0.905, n = 28, P < 0.001). These results would suggest that the slower reduction in f _c following the initial rapid reduction in both positions is partly attributable to a retardation in the restoration of the activity of the cardiac parasympathetic nervous system. Post-exercise upright stroke volume (SV, by impedance cardiography) decreased gradually to just below the pre-exercise level, whereas post-exercise supine SV increased markedly to a level similar to that at rest before exercise. The resultant cardiac output (Q˙ _c) and the total peripheral vascular resistance (TPR) in the upright and supine positions returned gradually to their respective pre-exercise levels in the corresponding positions. At the 10th min of recovery, both average SV and Q˙ _c were significantly greater (each P < 0.005) in the supine than in the upright position, while average TPR was significantly lower (P < 0.05) in the supine than in the upright position. In contrast, immediately after exercise, mean blood pressure dropped markedly in both the supine and upright positions, and their levels at the 10th min of recovery were similar. Therefore we concluded that arterial blood pressure is maintained relatively constant through various compensatory mechanisms associated with f _c, SV, Q˙ _c, and TPR during rest and recovery in different body positions. Accepted: 4 September 1999     

The effect of postural changes on body temperatures and heat balance

Early studies have demonstrated that rectal temperature (T _re) decreases and mean skin temperature (T _sk) increases in subjects changing their posture from standing to supine, and vice versa. Such changes have important implications insofar as thermal stress experiments are conducted and interpreted. However, the extent of these changes between steady-state conditions is not known. In addition, it is not known whether thermal balance is also affected by postural changes. To examine these questions, 11 healthy males were exposed to a thermoneutral air environment (28.2–28.5°C and 40% relative humidity) in various postures at rest. Body temperatures, heat losses, and metabolic rate were measured. Subjects wore shorts only and began in an upright posture (standing or sitting at an inclination of 7.5°) on a customized tilt-table. They were tilted twice, once into a supine position and then back to the original upright position. Each tilt occurred after steady state was satisfied based on the subject's circadian variation of T _re determined previously in a 4.25 h control supine trial. Times to supine steady state following the first tilt were [mean (SE)] 92.6 (6.4) and 116.6 (5.1) min for the standing and sitting trials, respectively. Times to upright steady state following the second tilt were 107.9 (11.4) and 124.1 (9.0) min. Mean steady-state T _re and T _sk were 36.87 (0.07) and 34.04 (0.14), 37.47 (0.09) and 33.48 (0.14), and 37.26 (0.05) and 33.49 (0.10) °C for supine, standing, and sitting, respectively. Thermal balance was attained in all steady-state conditions, and allowing for a decrease in the weighting factor of T _re for mean body temperature in the upright postures, it also appears that thermal balance was preserved between changes in posture. These results are consistent with no perceived changes by the subjects in their thermal comfort and skin wetness.     

Pathophysiological adaptations to walking and cycling in primary pulmonary hypertension

Exercise tolerance inversely correlates with the severity of the disease in patients with idiopathic pulmonary arterial hypertension (IPAH). Cycling and walking protocols are commonly utilized in the evaluation of exercise intolerance in IPAH, but little information exists on possible differences in ventilatory and gas exchange adaptations to these exercise modalities. In a group of patients with moderate to severe IPAH (n = 13), we studied the ventilatory, cardiovascular and gas exchange adaptations to maximal incremental walking (W) and maximal incremental cycling (C). During W, compared to C, the ventilatory equivalents for CO₂ output (V′_E/V′CO₂) were significantly higher either expressed as the rate of increment (56 ± 5 vs. 45 ± 3; P < 0.0001) or as the absolute values at anaerobic threshold (AT) and at peak exercise. At AT, the increase in V′_E/V′CO₂ during W was associated with a significant lower value of end-tidal carbon dioxide. At peak W, compared to peak C, dyspnea sensation was higher and arterial oxygen saturation (SpO₂) was lower (87 ± 2 vs. 91 ± 2, P < 0.001). In patients with IPAH the physiologic information obtained with W are different from those obtained with C. Tolerance to W exercise is limited by high ventilatory response and dyspnea sensation. W should be used to assess the degree of lung gas exchange inefficiency and arterial O₂ desaturation during exercise.     

Effects of physical training on ventilatory equivalent and respiratory exchange ratio during weight supported,steady-state exercise

Thirty-three college men participated in a 9-week endurance training program. An equal number of subjects served as controls. Pre- and post-test metabolic measurements were made during 10 min of submaximal exercise (1080 kpm/min at 60 rpm) and 15 min of recovery. Measurements included oxygen consumption, CO₂ production, ventilatory equivalent (V _E/VO₂ ratio) and respiratory exchange ratio (R). A three factor design variance analysis was used to analyze the effects of training on min-by-min exercise and recoveryV _E/VO₂ ratio andR. For the experimental group training resulted in a significant improvement in ventilatory efficiency during exercise, as well as a significant decrease inR. During recovery,V _E/VO₂ andR decreased significantly for both groups although the magnitude of change was greater for the group that trained. Apparently, there was a significant habituation effect due to test procedures for the control group. The results are discussed in terms of lactate production and substrate utilization during exercise.     

Use of a modified Swan-Ganz pacing catheter for measuringP di and diaphragmatic EMG

Measurements of pressures across the diaphragm (P _di) and diaphragmatic electromyogram (EMG) have become an integral tool to study respiratory muscle fatigue. To measureP _di and diaphragmatic EMG, three balloon catheter systems have to be swallowed two of these measure esophageal and gastric pressures and the third one, usually a Swan-Ganz catheter records diaphragmatic EMG. In the present study we describe how a thermodilution Swan-Ganz pacing catheter can be very simply modified to measure bothP _di and diaphragm EMG. Because only one catheter has to be swallowed, subject's acceptability improves, particularly for repeated measurements in the same subject. We have used such a catheter system for more than 18 months to study respiratory muscle fatigue in man. The measurements ofP _di by the modified Swan-Ganz catheter compare well with those recorded simultaneously with conventional balloons, and in vitro frequency response measurements showed that amplitude responses differed by 2% at 2 1/2 Hz. Phase responses to the esophageal and gastric balloons were linear over the range of frequencies tested.Supported by grants from Veterans Administration Medical Center     

A metabolic cart for measurement of oxygen uptake during human exercise using inspiratory flow rate

This study evaluated an ergo-spirometry system based on mixed expired gas for gas analyses and an inspiratory based determination of flow. There were 74 paired samples of oxygen uptake (VO₂) and related variables including pulmonary ventilation (V_E), fractional concentrations of expired CO₂ and O₂ (F _ECO₂ and F _EO₂, respectively), as well as CO₂ output (VCO₂) which were obtained from the metabolic cart and a Douglas bag system during 22 min submaximal and 5–8 min maximal running on a treadmill. For F _ECO₂ and VCO₂ the metabolic cart gave readings that were 2.6% and 1.8% higher and for F _EO₂ 0.2% lower than the Douglas bag method (P<0.05). For the metabolic cart and the Douglas bag method the coefficient of variation (CV) for repeated determinations of VO₂ was 1.9% and 1.8%, respectively. For VO₂ and V_E, there were no significant differences between the two methods and the 95% confidence interval of the difference in VO₂ was within –30 and +20 ml min^–1. The CV of the differences in VO₂ between the two systems was 2.4% and it is concluded that a metabolic cart method based on inspiratory flow rate is suitable for measurement of VO₂ and V_E during both submaximal and maximal exercise. Electronic Publication     

Ventilatory muscle strength, diaphragm thickness and pulmonary function in world-class powerlifters

Purpose

Resistance training activates the ventilatory muscles providing a stimulus similar to ventilatory muscle training. We examined the effects of elite powerlifting training upon ventilatory muscle strength, pulmonary function and diaphragm thickness in world-class powerlifters (POWER) and a control group (CON) with no history of endurance or resistance training, matched for age, height and body mass.

Methods

Body composition was assessed using single-frequency bioelectrical impedance. Maximal static volitional inspiratory (P _I,max) and expiratory (P _E,max) mouth pressures, diaphragm thickness (T _di) derived from ultrasound measurements and pulmonary function from maximal flow volume loops were measured.

Results

There were no differences in physical characteristics or pulmonary function between groups. P _I,max (22 %, P < 0.05, effect size d = 1.13), P _E,max (16 %, P = 0.07, effect size d = 0.86) and T _di (27 %, P < 0.01, effect size d = 1.59) were greater in POWER than CON. Correlations were observed between both T _di and P _I,max (r = 0.518, P < 0.05), T _di and P _E,max (r = 0.671, P < 0.01) and T _di and body mass (r = 0.502, P < 0.05).

Conclusions

We conclude that manoeuvres performed by world-class powerlifters improve ventilatory muscle strength and increases diaphragm size. Whole-body resistance training may be an appropriate training mode to attenuate the effects of ventilatory muscle weakness experienced with ageing and some disease states.