Hemodynamic during a postexertional asystolia in a healthy athlete: a case study

Hemodynamic events leading to spontaneous postexertional vasovagal syncope are not completely understood because of the lack of beat-to-beat data. We report a case study of a young athlete who undergoes a syncopal episode during the recovery period following a maximal cycle-ergometer test. The episode was monitored by an impedance cardiograph which can gather noninvasively beat-to-beat the flow of heart rate (HR), stroke volume (SV), cardiac output (CO), diastolic filling rate (SV/DT), and myocardial contractility index (PEP/LVET). The most important findings of this report are the dramatic reduction of SV/DT preceding the syncope, the increment of SV together with the reduction of HR preceding and following the syncope, the prompt recovery of CO values after the syncopal episode despite the bradycardia, and the reduction of PEP/LVET after the syncope. This report confirms the importance of active recovery immediately after strenuous exercise and supports the hypothesis that the reduction of SV/DT in the presence of an inotropic stimulation can trigger the vasovagal reaction.

Field test for mechanical efficiency evaluation in matching volleyball players

Field tests were performed in 10 volleyball (VB) players (4 females and 6 males) in order to obtain an index of mechanical work efficiency (mu' = Wmec/Woxy) while athletes played a game. Wmec was the mechanical work output, obtained by means of home made video image analysis software, by summing potential, kinetic translational and kinetic rotational energies of running and jumping athletes. Woxy was the oxidative energy consumption obtained from O2 consumption (VO2) by a telemetry device (Cosmed K2) that also gave values of pulmonary ventilation (VE) and heart rate (HR). VB were studied at rest before a game (R), during attacking phases (A) and during defensive phases (D). At R were found: VE = 11 +/- 1 l x min(-1), HR = 78 +/- 7b x min(-1), VO2 = 3.71 +/- 1.1 ml x kg(-1) x min(-1), Woxy = 75.1 +/- 22.3 J x kg(-1) x min(-1). During A all variables increased: VE = 49 +/- 6l x min(-1), HR = 149 +/- 15 b x min(-1), VO2 = 23.1 +/- 3.3ml x kg(-1) x min(-1), Woxy = 482.8 +/- 69.0 J x kg(-1) x min(-1), and Wmec 275.5 +/- 57.0 J x kg(-1) x min(-1) with mu'=0.57 +/- 0.09. In D HR (-9%), VE, VO2 and Woxy (-18%) were reduced when compared to A, decreasing mu' to 0.21 +/- 0.05. On the other hand mu' was found higher than 0.25 during A indicating an anaerobic contribution to energy expenditure; in D the mu' lower than 0.25 indicated a restoration of anaerobic energy sources. It might be proposed that a greater difference in mu' values between A and D also means a higher anaerobic energy contribution to the volleyball game.

Differences in cardiovascular profiles induced by mental arithmetic and by hand-eye task

Five young, healthy male students performed two different psychophysical tests each lasting 1 min. The first test (A) consisted of mental arithmetic with digiting of results on a keyboard; the second test (G) consisted of playing an electronic game based on hand-eye coordination. Before and during each test, subjects remained seated with their thoraxes connected to an impedance cardiography monitor which gave, non invasively, beat-by-beat values of heart rate (HR), cardiac output (CO), stroke volume (SV) and left ventricle ejection time (VET). Systolic (SBP) and diastolic (DBP) arterial blood pressures were measured by means of a sphygmomanometer and total peripheral vascular resistance (TPR) and mean systolic ejection rate (MSER) were calculated. During test A, CO (A = +30%, G = +14%), HR (A = +26%, G = +2%) and SBP (A = +16%, G = +10%) increased more than during test G, while SV (A = +3%, G = +12%) and MSER (A = +11%, G = +14%) increased less and TPR (A = -13%, G = -7%) and VET (A = -7%, G = -2%) decreased more than in G. It was concluded that the analysis of a more complete cardiovascular profile may enhance distinctions among the behavioural stressors that induced different combinations in cognitive and sensory-motor responses.

Stroke volume response to progressive exercise in athletes engaged in different types of training

Using the impedance cardiography method, heart rate (fc) matched changes on indexed stroke volume (SI) and cardiac output (CI) were compared in subjects engaged in different types of training. The subjects consisted of untrained controls (C), volleyball players (VB) who spent about half of their training time (360 min.week-1) doing anaerobic conditioning exercises and who had a maximal oxygen uptake (VO2max) 41% higher than the controls, and distance runners (D) who spent all their training time (366 min.week-1) doing aerobic conditioning exercises and who had a VO2max 26% higher than VB. The subjects performed progressive submaximal cycle ergometer exercise (10 W.min-1) up to fc of 150 beats.min-1. In group C, SI had increased significantly (P < 0.05) at fc of 90 beats.min-1 (+32%) and maintained this difference up to 110 beats.min-1, only to return to resting values on reaching 130 beats.min-1 with no further changes. In group VB, SI peaked (+54%) at fc of 110 beats.min-1, reaching a value significantly higher than that of group C, but decreased progressively to 22% of the resting value on reaching 150 beats.min-1. In group D, SI peaked at fc of 130 beats.min-1 (+54%), reaching a value significantly higher than that of group VB, and showed no significant reduction with respect to this peak value on reaching 150 beats.min-1. As a consequence, the mean CI increase per fc unit was progressively higher in VB than in C (+46%) and in D than in VB (+105%).(ABSTRACT TRUNCATED AT 250 WORDS)

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.

Respiratory and cardiac effects of passive limb movements in man

The purpose of these experiments is to see if reflex nervous hyperventilation obtained by passive limb movements in man is a consequence of the activation of a direct ascending nervous pathway from mechanoreceptors of moving limbs to respiratory centres, or if it is the consequence of a primary enhanced cardiodynamic activity. Contemporaneous measurements of pulmonary ventilation and cardiac output (the latter with the trasthoracic bioimpedance method) were carried out in subjects whose ankles were passively moved at an angle of 10 degrees and a frequency of 1 Hz, each test lasting three breaths. Results showed a fast increase in pulmonary ventilation in all test breaths (+27% from control) mainly depending on respiratory frequency increases and accompanied by a tendency to reduce end tidal PCO2. Cardiac output did not change during tests because of a lack of changes in heart rate and stroke volume. The lack of cardiac output increases during this reflex hyperventilation supports the existence of a direct neural pathway from limb proprioreceptor afferents to respiratory structures.

Effects of long-lasting stimulation of extensor muscle nerves on pulmonary ventilation in cats

Increments in pulmonary ventilation were shown to occur in anaesthetized cats during long-lasting stimulation of a peripherally cut extensor muscle nerve at maximal intensity for group I afferent fibers. However, these increments tended to gradually adapt to a lower value when stimuli were delivered at high frequency and constant rate whereas a tendency to potentiation, up to a steady state, occurred when stimulation was intermittent. End-tidal PCO2 initially decreased with a tendency to adaptation in the case of continuous stimulation, and decreased progressively in the case of intermittent stimulation. It is concluded that the nervous mechanisms producing hyperpnoea exhibit fatigue during their constant excitation while their effects sum up during intermittent stimulation.

Respiratory responses to stimulation of large fibers afferent from muscle receptors in cats

Experiments were carried out on cats to re-examine the respiratory effects of the stimulation of the large afferent fibers originating in the receptors of the hindlimb muscles. During the contraction of the triceps surae induced by stimulating the ventral roots, pulmonary ventilation increased due to an increase in tidal volume and, usually, in respiratory frequency. An increase in ventilation occurred also during stimulation at group I strength of the central end of the previously cut nerves to the triceps surae (LGS + MG) and to the posterior biceps plus the semitendinosus (PBST) muscles. Appreciable increase in ventilation was seen for stimuli near threshold for group I (Ia + Ib) afferent fibers of the LGS + MG nerves, while stimuli at group Ib strength were needed to produce the same effects when using the PBST nerves. It is concluded that group Ib fibers afferent from muscle receptors play a role in the reflex control of respiration.

[Auditory evoked potential in normal rats and after para-chlorophenylalanine (PCPA) treatment]

We have studied the latency behaviour of an early component of the cortical acoustic evoked potentials (EAEP) in albino rats after administration of p-chlorophenylalanine (PCPA), a rather selective tryptophan-hydroxylase inhibitor, at a dose of 100 mg/kg daily for 3 days. The rats were implanted with 3 chronic electrodes: one in the bregma, one in the nasion and 3rd inserted in the periauricular skin. Series of clicks originating from a square pulse of 0.12 msec duration were administrated. Brain responses were amplified by an EEG and averaged by a computer with different post-stimuli analysis times. A first group of 4 rats was tested with clicks of 100 dB (HTL) intensity and brain responses were analysed at 5,10,25,50,100 msec post-stimuli times. Results demonstrate that after PCPA administration there is a latency reduction of EAEP components that have a latency higher than 20 msec. In a second group of 4 rats we have analysed those EAEP components with an intensity of clicks ranging from 60 to 110 dB and results demonstrate that, when PCPA was administered, Latencies of those components were significatively lower than the controls at each stimuli intensity tested. We concluded that 5-HT may influence the acoustic pathways activity and this is according to remarks of other A.A. that found a correlation between acoustic stress and brain 5-HT levels.

[Behavior of the discharge of the Golgi tendon organs during subtetanic muscular contraction]

In a series of isotonic muscle contractions induced by repetitive stimulation at frequencies higher than 0.1 Hz the pause in the afferent discharge of the muscle spindles tends to decrease as a function of time and as a function of frequency, while the afferent discharge of the Golgi tendon organs, as measured in the same experimental conditions, remains constant. The results support the hypothesis that the changes in the spindle are due to changes in the visco-elastic properties of the intrafusal muscle fibers (1). Since no muscolar tissue is present within the Golgi tendon organs (4) their afferent discharge and the pause, which occurs during the relaxation phase (3) do not change as seen in the spindles.

Respiratory ventilation during muscular contraction in man

Brief contraction of arm muscles affects respiratory ventilation either by increasing respiratory frequency or by increasing the instantaneous flow. Both these changes occur at a time subsequent to muscle contraction and can be attributed to a reflex mechanism originating from the muscles.

Intranigral kainic acid: evidence for nigral non-dopaminergic neurons controlling posture and behavior in a manner opposite to the dopaminergic ones

The unilateral, intranigral administration of kainic acid (k.a.) produced a syndrome characterized by early sequelae of contra- and ipsilateral circling and by a chronic contralateral turning associated with moderate loss of neurons in the pars reticulata. The acute contralateral circling seems to be related to dopaminergic nigro-neostriatal neuron stimulation, since it was prevented by previous intranigral injections of 6-OHDA. The acute ipsilateral circling and the chronic contralateral turning, on the other hand, seem to be independent of the integrity of the dopaminergic system and may be due to an initial stimulation, followed by destruction, of a nigral neuronal system which mediates turning behavior in a manner opposite to that of nigro-striatal dopamine. Treatment with D-amphetamine or apomorphine changed the contralateral into ipsilateral turning, while haloperidol potentiated the contralateral turning. Bilateral injection of k.a. into the nigra resulted in chronic stereotyped sniffing and gnawing, which were not inhibited by haloperidol. Moreover, haloperidol did not produce catalepsy in these animals. It is suggested that the intranigral k.a. injection destroyed a neuronal system antagonistic to dopamine and resulted in a reduction of the response to DA-receptor stimulation of the c. striatum.

Evidence for a correlation between the latency of an early component of auditory evoked potentials and the brain levels of serotonin in albino rats

Changes in brain serotonin levels are correlated with the latency of an early component of auditory evoked potentials (EAEP) in rats. In fact 5-hidroxytryptophan provokes an increase both in serotonin brain synthesis and in the latency of EAEP. On the other hand, PCPA provokes an opposite effect.

[Study on the absorption and utilization of D-galactose and D-glucose by liver and muscular tissue in the albino rat]

In order to compare the disposition of D-galactose and D-glucose in various organs of the rat, we have measured the amount of 14C-galactose and 14C-glucose present in the enteric canal, blood, muscle and liver, 2h. after the oral administration of the labelled esoses. Our results show that the two esoses are ebsorbed almost completely and to the same extent by two hours after their administration, Galactose has a longer half-life than glucose, being more slowly utilized in the synthesis of glycogen in liver and muscle.