[Response of tidal volume to inspiratory time ratio during incremental exercise]. / Respuesta de la relación volumen corriente-tiempo inspiratorio durante un esfuerzo incremental.

OBJECTIVE: There is some debate about the participation of the Hering-Breuer reflex during exercise in human beings. This study aimed to investigate breathing pattern response during an incremental exercise test with a cycle ergometer. Participation of the Hering-Breuer reflex in the control of breathing was to be indirectly investigated by analyzing the ratio of tidal volume (VT) to inspiratory time (tI). SUBJECTS AND METHODS: The 9 active subjects who participated the study followed an incremental protocol on a cycle ergometer until peak criteria were reached. During exercise, VT/ti can be described in 2 phases, separated by activation of the Hering-Breuer reflex (inspiratory off-switch threshold). In phase 1, ventilation increases because VT increases, resulting in a slight decrease in tI, whereas, in phase 2, increased ventilation is due to both an increase in VT and a decrease in tI. RESULTS: The mean (SD) inspiratory off-switch threshold was 84.6% (6.3%) when expressed relative to peak VT (mean, 3065 [566.8] mL) and 48% (7.2%) relative to the forced vital capacity measured by resting spirometry. The inspiratory off-switch threshold correlated positively (r=0.93) with the second ventilatory threshold, or respiratory compensation point. CONCLUSIONS: The inspiratory off-switch threshold and VT/ti are directly related to one another. The inspiratory off-switch threshold was related to the second ventilatory threshold, suggesting that the Hering-Breuer reflex participates in control of the breathing pattern during exercise. Activation of the reflex could contribute by signaling the respiratory centers to change the breathing pattern.

Reproductive function in male endurance athletes: sperm analysis and hormonal profile.

The purpose of this investigation was to study the effects of endurance exercise on male reproductive function (sex hormones and seminograms). Professional cyclists [n = 12; mean age 24 +/- 2 (SD) yr], elite triathletes (n = 9; 26 +/- 3 yr), recreational marathon runners (n = 10; 32 +/- 6 yr), and sedentary subjects (control group; n = 9; 30 +/- 4 yr) were selected as subjects. for each group, the following parameters were measured three times during the sports season (training period: winter; competition period: spring; resting period: fall): percentage of body fat, hormonal profile (resting levels of follicle-stimulating hormone, luteinizing hormone, total and free testosterone, and cortisol), and seminograms (quantitative parameters sperm volume and sperm count; qualitative parameters: sperm motality and morphology). The following comparisons were made in the measured parameters: 1) within groups (longitudinal design) and 2) between groups in each of the three periods (cross-sectional design) and over time (mixed design). In addition, both the volume and the intensity of training of each subject during the season (except for the control group) were quantified. Despite significant differences in training characteristics and in body fat percent, in general no significant differences (P > 0.05) were found in hormonal profiles or in semen characteristics between or within groups. A lower sperm motility (46.2 +/- 19.5%), however, was observed in the cyclists during the competition period when compared either with the other groups during this same period (P < 0.05) or with themselves during the other two periods of study (P < 0.01). In any case, the later phenomenon was attributed to physical factors associated with cycling, such as mechanical trauma to the testis and/or increased gonadal temperature. In conclusion, our findings suggest that endurance exercise does not adversely affect the hypothalamic-pituitary-testis axis.

Platelet aggregability in relation to the anaerobic threshold.

Platelet aggregability might be increased during physical exercise. This, in turn, has been explained by the elevation of plasma catecholamines and by the state of lactic acidosis, which occur at high exercise intensities. The purpose of this investigation was to study the relationship between changes in platelet aggregability and exercise intensity, the latter being determined in reference to the anaerobic threshold (AT). Each of sixteen male subjects performed an incremental exercise test in order to determine both (a) his running velocity (VAT) corresponding to his anaerobic threshold and (b) his running velocity (V4mM) corresponding to 95% of his running velocity eliciting a blood lactate concentration of 4 mM.l-1. Three and six days after this preliminary test, respectively, each subject performed an exercise test of 30 minutes, at a constant running velocity of either VAT or V4mM. Running velocity for each day's test was randomly assigned. Both capillary and venous blood samples were collected immediately before and immediately after each test, and after 30 minutes of recovery from each test, respectively. Capillary blood samples were obtained for determination of blood lactate concentration, whereas venous blood samples were obtained for determination of platelet count, and platelet aggregation in response to ADP and collagen, respectively. Platelet count significantly increased (p < 0.001) immediately after the 30-minute-tests at either VAT and V4mM, remaining elevated (p < 0.05) after 30 minutes of recovery from the tests at V4mM. The results did not evidence any significant increase in platelet aggregability with exercise, except for aggregation response to ADP immediately after the tests performed at V4mM (p < 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)

Lactic threshold vs ventilatory threshold during a ramp test on a cycle ergometer.

OBJECTIVE: The purpose of this investigation was to study the relationship between the lactate (LT) and the ventilatory threshold (VT) during a ramp protocol in cycle ergometry. PARTICIPANTS: Thirty nine trained male subjects were selected as subjects. EXPERIMENTAL DESIGN: All the subjects performed a maximal ergometric test on a cycle ergometer consisting of a ramp protocol (increases of 25 W.min-1). The anaerobic threshold (AT) was determined using both ventilatory gas analysis (VT) and lactate measurement (LT). All the data related to the VT and LT were expressed in work rate (W), VO2 (ml.kg-1.min-1) and heart rate (bpm) and expressed as mean and standard deviation. Lactate threshold (LT) and ventilatory threshold (VT) were compared using the Student's "t"-test for paired data. Correlation coefficients between both variables were also calculated. Statistical significance was accepted at the 5% level. RESULTS: Results showed significant differences (p < 0.05) between mean values of VT and LT when both expressed either as heart rate (bpm), work rate (W), or VO2 (ml.kg-1.min-1). CONCLUSIONS: It was concluded that LT and VT occur at different exercise intensities during ramp protocol exercise on a cycle ergometer.

Monoclonal antibodies for exercise-induced fecal blood detection--comparison with Hemofec.

The purpose of this investigation was to determine the incidence of fecal occult blood in marathoners using an immunochemical technique (OC-Hemodia). Five stool specimens (2 pre- and 3 postrace) were collected from 24 male runners (mean age 41.4 +/- 9.3 yrs) and analysed for fecal occult blood using the OC-Hemodia test. The results were also compared with a qualitative test (Hemofec) in 12 subjects who were randomly selected from the overall group of 24 runners. With the immunochemical technique, the results evidenced the presence of fecal occult blood in 8 subjects in the first postrace stool specimens. Four of these 8 subjects also tested positive in the second postrace sample, whereas in the third postrace sample only one of them tested positive. With the qualitative test, fecal blood was demonstrated in 10 runners in the first postrace sample. Eight of them tested positive in the second sample, whereas only 5 tested positive in the third sample. The immunochemical technique is recommended for fecal occult blood detection in marathoners.

Saliva electrolytes as a useful tool for anaerobic threshold determination.

The purpose of the present study was to determine the anaerobic threshold by analysis of changes in saliva composition during an incremental exercise test on a cycle ergometer. Thirteen healthy males underwent a submaximal test with an initial load of 50 W and load increases of 50 W per 3 min, until capillary blood lactate exceeded 4 mmol.l-1. A maximal test for maximum O2 uptake (VO2max) determination (initial load of 100 W and load increases of 50 W per 2 min) was also performed. Saliva and blood samples were obtained only in the submaximal test. Saliva threshold (Thsa) was defined as the point at which the first increase in either Cl- or Na+ occurred. Catecholamine threshold (Thca) was defined as the point at which a nonlinear increase occurred in either adrenaline or noradrenaline. The lactate (Thla) and ventilatory (Thve) thresholds were determined according to published criteria. No significant differences were found between Thsa values and the other methods of threshold determination. A high correlation was found between Thsa and Thla (r = 0.82, P < 0.01), and Thsa and Thca (r = 0.75, P < 0.05). These results support the validity of Thsa as a new method for noninvasive determination of the anaerobic threshold.

Anaerobic threshold in children: determination from saliva analysis in field tests.

The purpose of this study was to determine the anaerobic threshold of children by the analysis of saliva collected during field tests. A group of 25 children (mean age, 10.5 years) performed an incremental exercise test on a track, consisting of 4-min stages at increasing running velocities. Before each test (at rest) and at the end of each stage, both blood (via finger pricks) and saliva samples (for measurement of salivary concentrations of Na+ and Cl-) were collected to determine lactate threshold (Thla-) and saliva threshold (Thsa), respectively. There were no significant differences between values of Thla- and Thsa when expressed either as running velocity [mean Thla-, 10.73 (SD 1.96) km.h-1; mean Thsa, 10.89 (SD 1.69) km.h-1)] or heart rate [Thla-, 182(SD 14) beats. min-1 Thsa 183 (SD 11) beats.min-1]. In addition, correlations between Thsa and Thla were high, when both values were expressed as running velocity in kilometres per hour (r = 0.89; P < 0.001), or heart rate in beats per minute (r = 0.90; p < 0.001). In conclusion, these findings suggested that saliva analysis would be a valid method for anaerobic threshold determination in field tests.

Anaerobic threshold determination with analysis of salivary amylase.

The purpose of this study was to determine the anaerobic threshold from analysis of amylase concentration in total saliva during a laboratory exercise test. Each of 20 healthy young men performed both a submaximal and a maximal test on a treadmill. During the submaximal test, capillary blood and total saliva samples were collected for determination of anaerobic threshold (AT) and saliva threshold (Tsa), respectively. Tsa was defined as the point at which the first continuous increase in amylase concentration occurred during exercise. The results showed no significant difference between values of AT and Tsa when both were expressed either as running velocity or as heart rate. In addition, there existed a high correlation between AT and Tsa (r = .93, p < .001). It was therefore concluded that the analysis of amylase concentration in total saliva during exercise might be used as a valid new method for determining AT.