The effect of limb movements on the regulation of depth and rate of breathing

Coordination of breathing and various movement markers during pianists' performance tasks

Few investigations have analysed the relations of breathing and pianists' movements. In past studies, however, coordination of breathing with repetitive movements were examined. The current experiment explored the coordinative relations of breathing with three different finger-movement markers (pitch, meter, and thumb passage) during the performance of repetitive exercises at the piano. Eight pianists played the C major scale and arpeggio at different tempi. The Musical Instrument Digital Interface (MIDI) data were collected and the pianists' respiration was simultaneously monitored by inductive plethysmography. Analysis showed that the breathing varied between participants. Other than some exceptional cases for which movement markers coincided with the end of inspiration and the end of expiration of the breathing curve, no coordination or relation occurred between breathing and finger movement.

Passive limb movement augments ventilatory response to CO2 via sciatic inputs in anesthetized rats

Passive limb movement (PLM) in humans induces a phasic hyperpnea, but the underlying physiological mechanisms remain unclear. We asked whether PLM in anesthetized rats would produce a similar phasic hyperpnea associated with an augmented ventilatory (V(E)) response to CO(2) that is dependent on sciatic afferents. The animals underwent 5 min threshold PLM, 3 min hypercapnia (5% CO(2)), and their combination (CO(2) exposure at the end of 2nd min of 5-min PLM) before and after bilateral transection of the sciatic nerves. We found that a threshold PLM evoked a phasic hyperpnea, similar to that denoted in humans, and an augmented V(E) response to CO(2). Both responses were greatly diminished by sciatic nerve transection. Moreover, similar responses were also evoked by electrically stimulating the central end of the transected sciatic nerve. Our findings suggest an ability of the sciatic afferents to augment the V(E) response to CO(2) that likely contributes to the PLM-induced hyperpnea.

Running training and co-ordination between breathing and running rhythms during aerobic and anaerobic conditions in humans

The study was carried out on ten triathletes, six sprinters and ten subjects not trained in running (controls) to assess the effects of training history on the co-ordination between breathing and running rhythms during running on a treadmill. Three exercise intensities were used: 50%, 80% and 110% of the subject's anaerobic threshold (AT). All three intensities were performed twice: once with spontaneous breathing and once with breathing intentionally co-ordinated to the running rhythm. Heart rate, respiratory parameters and leg movements were continuously recorded. Blood lactate concentrations were measured discontinuously. The degree of co-ordination between running and breathing was quantified as the percentage of inspirations and/or expirations starting during the same phase of step. The results showed that the degree of both spontaneous and intended co-ordination at aerobic exercise intensities was in all three groups the same and increased in all groups with increasing intensity from 50% to 80% of AT; further increase of intensity to 110% of AT was associated with a significant decrease of co-ordination in controls and sprinters, whereas triathletes were able to maintain the same high degree of co-ordination as at 80% of AT. It was concluded that running training of either type at aerobic work loads had no effect on the co-ordination between running and breathing rhythms. At anaerobic intensities, however, the degree of co-ordination between running and breathing rhythms was higher in the endurance trained athletes than in the sprinters or in the untrained subjects. The degree of co-ordination increased with increasing regularity of breathing.(ABSTRACT TRUNCATED AT 250 WORDS)

Distribution of motor activity to expiratory muscles during sciatic nerve stimulation in the dog

The present study examined the effect of increasing sensory input from the lower limbs (assessed from the response to electrical stimulation of the sciatic nerve) on the distribution of electrical activity to the expiratory muscles. Expiratory muscle response to sciatic nerve stimulation (SNS) was compared to the response of the inspiratory muscles, and to their response to hypercapnia. In 16 anesthetized dogs afferent SNS increased ventilation and augmented the integrated EMG of all six expiratory muscles studied. Increases in abdominal muscle electrical activity were not uniform, being greater in the transversus abdominis and external oblique as compared to the internal oblique and the rectus abdominis. Increases in thoracic expiratory and inspiratory muscle activity during SNS were similar in magnitude. SNS performed while dogs were breathing 7% CO2, produced increased neural activity similar to those observed during O2 breathing. During CO2 rebreathing, at equal levels of minute ventilation, expiratory muscle responses to SNS and to CO2 were similar. In contrast, the rate of rise of the inspiratory muscle EMGs was greater during SNS. The present study indicates that the abdominal muscles participate in the respiratory response to afferent neural drive from skeletal muscles. The magnitude of their response is independent of their pre-stimulation level of activity and is similar to that observed during CO2 stimulated breathing.

Synchronization of locomotion and respiration in trotting ponies

The aim of the present experiment was to investigate the hypothesis that there is a respiration-locomotion coupling in trotting equines. Therefore the respiratory airflow (V), the gastric pressure (Pga) and pleural pressure (Ppl) changes and the step frequency (SF) were simultaneously recorded in 5 trotting ponies (body weight: 255 +/- 15 kg; age: 3.5 +/- 0.4 years). Airflow was measured using a Fleisch pneumotachograph fixed on a face mask. Esophageal and gastric balloon catheters coupled to pressure transducers allowed the recording of Ppl and Pga. The exercise was performed on a treadmill and consisted of 1 min walking (1.5 m.s-1), 1 min slow trotting (3.0 m.s-1)(Trot 1) and 3 min fast trotting (3.5 m.s-1)(Trot 2). Data were continuously recorded before and during exercise. At walk and Trot 1, none of the ponies displayed a coupling between SF and the respiratory frequency (RF). In one pony, SF and RF were coupled at a constant ratio of 2:1 during Trot 2 while two other ponies displayed the same coupling only up to the second minute of Trot 2. In the two last ponies, a coupling occurred at the third minute of Trot 2. In all ponies, the peaks in Pga occurring during expiration occurred always simultaneously with the first and/or the second peak V, whether or not there was a relationship between SF and RF. On the other hand, when SF and RF were coupled, the first part of inspiration was always simultaneous to a decrease in Pga. It was concluded that in trotting ponies respiration and locomotion are not always independent and that the abdominal piston may act in synergy with the respiratory pump in some phases of the breathing cycle.

Ventilatory responses during varied stride and pedal frequencies

The effects of limb movement frequency during walking and running and cycling at 60 and 90 rpm on the ventilatory responses were studied in 19 male subjects. Ten of the subjects were trained runners whereas nine of the subjects were trained cyclists. The runners completed walk and run exercise trials at equal levels of CO2 excretion (VCO2) and low (approximately 60) rpm and high (approximately 90) rpm cycling trials at equal VCO2 levels. The cyclists completed low and high rpm cycling trials at equal VCO2 levels. The cyclists were not tested on the walk/run trials as they had been tested previously and had been shown to have similar ventilatory responses when walking and running at equal VCO2 levels. Minute ventilation (VE), tidal volume (VT), breathing frequency (f), end-tidal CO2 (PETCO2) and O2 (PETO2) tensions, and inspiratory (TI) and expiratory (TE) times were not found to differ significantly between the low and high pedal frequency trials for either the cyclists or the runners. No significant differences were found in estimated arterial CO2 tensions (PaCO2) or estimated alveolar ventilation (VA) between the cycling trials for either the runners or the cyclists. When comparing running to walking, the runners were found to have a greater VE and estimated VA. This was mediated by an increase in f as VT was found to decrease. The increased f was associated with a shortened TI as TE was not significantly different between the walk and run trials. End-tidal CO2 tension and estimated PaCO2 was significantly lower during the run trial as compared to the walk trial. These results suggest some form of neurogenic stimuli influencing ventilation in the runners while running. This same neurogenic influence is not present when cyclists run and when either cyclists or runners exercise on the bicycle. A possible source for the neurogenic stimuli is discussed.

Contribution of central and reflex nervous activity to the rapid increase in pulmonary ventilation at the start of muscular exercise in man

To investigate the relative contributions of the central and peripheral neural drive to hyperventilation at the onset of muscular exercise, five volunteers were tested during the first ten breaths while performing both voluntary (VM) and passive (PM) ankle rotations with a frequency of 1 Hz and through an angle of 10 degrees. Resulting breathing patterns for the two movements were compared. Hypocapnic hyperventilation, found in both PM and VM, indicated its neural origin. Respiratory changes were higher in VM than in PM. In both experimental conditions, increases in ventilation (VE) depended more on respiratory frequency (f) than on tidal volume (VT). Moreover, increases in VT adapted, breath-by-breath, to values lower than the initial ones, while increases in f rose progressively. Expiratory time was reduced more than inspiratory time (TI); increases in inspiratory flow (VT/TI) depended to the same extent on changes in both TI and VT. Increases in expiratory tidal volume were initially higher than in inspiratory tidal volume, thereby producing a reduction in functional residual capacity. Because PM respiratory changes could be considered to be of nervous reflex origin only, the identical breathing patterns in PM and VM indicated that the hyperventilation found also in VM was mainly of reflex origin. The increase in VE was considered to be dependent on a greater stimulus from muscle proprioreceptors.

Reflex modulation of phrenic activity through hindlimb passive motion in decorticate and spinal rabbit preparation

The neurogenic effect of passive hindlimb movement on phrenic nerve discharge was compared in decorticate unanaesthetized and curarized rabbit preparations prior to and after spinal transection. The question of how and where sensory information has access to the central respiratory network was addressed in each case. All passive motions, performed using a mechanical device, were of constant amplitude in a given preparation. The results clearly differed in decorticate and spinal preparations. In the decorticate vagotomized preparation, periodic passive motions led to an immediate shortening of the respiratory period which lasted throughout the periodic stimulation and stopped with its cessation; it did not depend on the frequency of the natural stimulation and was entirely due to a 20% shortening of the expiration time. Maintained full flexion or full extension both induced the same expiration time shortening, but limited to the first two to three respiratory cycles after onset and interruption of stimulation. After spinal transection at the C2 level, and moderate activation with DOPA, no phrenic activity developed in the absence of proprioceptive stimulation. Periodic hindlimb movements evoked simultaneous large bursts in both phrenic nerves during each extension; a 1:1 coordination of phrenic activity with the external imposed period (P) was observed for various P values. A strong phrenic activation could also be elicited through maintained full hindlimb extension but not through full flexion: this activation appeared as rhythmic discharge as long as extension was maintained. It is concluded that proprioceptive inputs act upon the medullary respiration generator and reset its own rhythm whereas, at the spinal level, they elicit an amplitude modulation at phrenic motoneuronal level without acting upon the rate of the spinal "respiration" generator itself; on the same phrenic motoneurons, a subthreshold central activation added to a subthreshold proprioceptive activation probably accounts for the phrenic bursting during maintained extension. Finally, the proprioceptive control from the hindlimb on phrenic activity is processed at different sites of the central respiratory network at medullary and at spinal level, and may depend on different input signals.

Effects of pedal rate on respiratory responses to incremental bicycle work

1. The influence of pedal rate on ventilatory response and breathing pattern during cycle exercise was studied in twelve untrained female subjects performing 15 W/min incremental work on a bicycle at 30 and 60 r.p.m. Comparisons were made within the range of aerobic work rate to avoid additional influences of a developing lactic acidosis. 2. At each pedal rate, CO2 excretion (VCO2) increased progressively to a level of 1.2 1/min with incrementally loaded cycling. With increasing VCO2, minute ventilation (VE), respiratory frequency (f), tidal volume (VT) and end-tidal PCO2 progressively increased. The inspiratory (TI) and expiratory (TE) durations decreased sharply on the transition from rest to unloaded cycling; further decreases occurred during incrementally loaded cycling. 3. Compared to 30 r.p.m., cycle exercise at 60 r.p.m. resulted in greater increases in VE and lower levels of end-tidal PCO2 at any given levels of VCO2. The greater ventilatory responses were due mostly to greater increases in f, which were in turn due to greater decreases in TE. The decrease in TI during cycling was little affected by changes in pedal rate. 4. The different magnitudes of ventilatory and PCO2 responses under the two pedal rate conditions suggest that neurogenic stimuli, central and/or peripheral in origin, participate in the control of exercise hyperpnoea in the non-steady-state phase. The possibility that the ventilatory response to cycle exercise is affected by the way that pedal rate is changed is discussed.

Effect of coupling the breathing- and cycling rhythms on oxygen uptake during bicycle ergometry

The influence of the degree of coupling between the breathing and cycling rhythms (K) on oxygen uptake (Vo2) was examined in 30 volunteers. They cycled on an ergometer with a load equal to 50% of their work capacity 170 in two experimental runs with spontaneous breathing rhythm, and in a further two runs with acoustically triggered breathing. K was continuously ascertained. Vo2 and other respiratory parameters were measured by an automatic "breath-by-breath analysis" system. In 16 subjects, Vo2-differences between runs were correlated with the differences in K. In the majority of these subjects (12), Vo2 decreased significantly with increasing K. In 14 subjects, Vo2-and K-variations within individual runs were analyzed. Phases with higher K were regularly accompanied by a decrease in Vo2. It is concluded that coupling the breathing and cycling rhythms reduces Vo2 for a given moderate work load, although the magnitude of the Vo2-reduction varies considerably between individuals.

High frequency oscillation of the lungs alone lengthens expiration in dogs

High frequency (15 Hz), low volume (approximately 40 ml) oscillation of the respiratory system lengthens expiration in anesthetized dogs even in the absence of changes in mean expiratory lung volume or blood gases (Banzett et al., 1983). Although vagotomy abolishes this response, we felt it might mask the reflex rather than interrupt the afferent pathway. To ascertain whether pulmonary and airway afferents alone are capable of evoking this reflex, we confined the oscillatory stimulus to the lung by widely opening the chest. The dogs were paralyzed but breathed 'spontaneously' by means of a solenoid valve opened and closed by the phrenic neurogram. End-expiratory lung volume and PCO2 were held constant. All eight dogs that were tested after thoracotomy lengthened expiration during oscillation. Although quantitative comparisons of responses before and after thoracotomy are not entirely reliable, we could see no consistent change in the strength of response with paralysis or with thoracotomy. We conclude that the principal afferent limb of the ventilatory reflex response to oscillation arises in the lungs and intrathoracic airways.

Effects of body temperature, passive limb motion and level of anesthesia on the activity of the inspiratory muscles

The relationships between relative tidal activity (moving average EMG) of the diaphragm (AdiT) and of the external intercostal or parasternal muscles (AicT) and between the rate of rise of these activities (Adi and Aic) were assessed during rebreathing in rabbits with various body temperatures (BT: 34-41 degrees C) before and after vagotomy (VGT), at rest and during passive limb motion (PLM), and in vagotomized rabbits with or without thoracic dorsal rhizotomy (TDR) under light (LBA) or deep barbiturate anesthesia (DBA). Both relationships had the form AicT = a AdiTb and Aic = a' Adib'. In intact normothermic animals under LBA mean values for b and b' were 1.47 and 1.37, a and a' being unity by definition. No changes in b or b' occurred even with TDR: this suggests that the relation between the central command to phrenic and to inspiratory intercostal alpha-motoneurones was the same under all conditions. Neither BT nor PLM modified a', but a changed owing to BT and PLM dependence of the relation between central inspiratory drive and off-switch threshold. Both VGT, independently of BT, and DBA decreased a and a' before but not after TDR, when a and a' reached the lowest values (0.12 and 0.22). Hence VGT and DBA, but not BT and PLM, change the relation between the central command to inspiratory intercostal alpha- and gamma-motoneurones, the multiplicative effect of alpha-gamma linkage on AicT and Aic being prevented by TDR.

Respiratory responses to running and walking at the same metabolic rate

The ventilatory responses of ten subjects were evaluated during walking and running on a motor driven treadmill. The treadmill grade was adjusted so that the oxygen uptake was the same walking as running at 0% grade. Ventilation (gasometer) and PETCO2 (infrared CO2 analyzer) were monitored breath-by-breath. It was found that running, compared to uphill walking, significantly increased ventilation by an average of 7.80 1 X min-1 BTPS. Respiratory frequency increased by approximately 27% while tidal volume was reduced by an average of 7.2%. The R value of running was 0.88, significantly greater than the 0.81 calculated for uphill walking. Walking resulted in a mean PETCO2 of 46.9 +/- 0.8 Torr, while running significantly reduced the PETCO2 by 4.3 +/- 0.4 Torr. The time components of the breathing cycle were also different for walking and running. These results suggest that by changing gait, at a constant metabolic cost, a dissociation VCO2 and VO2 may occur. These results also suggest a variation in the control of respiration when comparing walking and running.

Relation between pedalling- and breathing rhythm

The relationship between pedalling- and breathing rhythm was studied in 34 medical students (non-cyclists") and 10 racing cyclists on an electromagnetic bicycle-ergometer, the effective work load of which (50 W, 100 W, 150 W, 200 W) was independent of the pedalling rate. The criteria used were integer p/b ratios (pedalling rate being a multiple of breathing frequency) and phase coupling (the breathing phases starting preferentially at a certain angle of the pedalling cycle). Unconsciously occurring coordination of pedalling and breathing rhythm was found in the majority of the test persons; 70%-100% of the racing cyclists, 50%-63% of the regularly breathing and 25%-33% of the decreased with increasing work load. Phase coupling was even more frequent than integer p/b ratios and was not affected by increasing work load. The majority of racing cyclists (unlike the non-cyclists) coupled the inspiration-onset with the onset of either the left or the right leg movement. Expiratory phase coupling, however, was analogous in all groups; expiration began preferentially at mid-contraction of either leg. The results are discussed in terms of relative (nervous) coordination. It is concluded that the tendency to coordination between pedalling- and breathing rhythm increases with pedalling training and with regularity of breathing.

Entrainment of breathing rate to movement frequency during work at two intensities

Ten males and six females exercised on an electrically braked cycle ergometer. Three conditions were tested: preferred pedal frequency with no cues; preferred frequency established by listening to a metronome and preferred frequency maintained by watching a digital display. Each condition was performed at a low workload and a high workload, and this set of tests was repeated once. During each test, computer sampling of pedal and breath information occurred, and the relationship of breath signal occurrences to pedal signals was plotted by a post stimulus histogram program. Fourier analysis of psh data (Time Series Spectrum Estimation) decomposed each histogram into it's frequency components. The magnitude of the frequency at the fundamental of the pedal period (F1), and it's first harmonic (F2), were assessed using F ratios. For retest results, preferred condition, 100% of subjects were entrained for both low and high workloads. With the metronome, 87% were entrained at the low workload and 94% at the high workload. For both workloads, 94% were entrained when watching a digital printout of pedal frequency. For preferred pedal rate, at the two workloads tested, the results of this study strongly support the existence of entrainment, and provide evidence for neurogenic input to ventilatory control during steady state work.

Central and direct vagal dependent control of expiratory duration in anaesthetized rabbits

In anaesthetized rabbits, total or partial (only inflation reflex nearly abolished) DC current vagal block was performed during inspiration (ITB and IPB), or expiration (ETB and EPB), or throughout the breathing cycle (CTB and CPB). During CTB inspiratory (Ti) and expiratory duration (Te) increased as after vagotomy. With ITB Ti equally Tivag; Te increased, but remained shorter than Tevag. During ETB, Ti was unchanged, Te increased, but remained shorter than Tevag. The sum of deltaTe during ITB and ETB equalled deltaTevag. During CPB and IPB, Ti and Te behaved as during ITB. With EPB, Ti was unchanged and Te shortened. Preferential stimulation of large myelinated fibers in the central vagal stumps during expiration lengthened Te. Inspiratory stimulation shortened both Ti and Te, restored breath timing of ETB, but not that of pre-vagotomy control. Hence, Te of eupneic breaths should depend on a central mechanism relating Te to preceding Ti and on expiratory vagal discharge, having both a small lengthening (from stretch receptors) and a variable shortening effect (from irritant receptors). Both central and peripheral mechanisms are affected by CO2 breathing.