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PubMed2001

Heterogeneity of metabolic parameters in the left ventricular myocardium and its relation to local blood flow.

It is well established that myocardial blood flow is heterogeneous on the local level. During recent years comprehensive studies have been undertaken to assess the relation between myocardial metabolism and spatial blood flow heterogeneity. Based on the type of measurements two major groups of studies have been performed: enzyme activity and tissue metabolite level assessments. Enzyme activity measurements have provided only limited insight into the coupling of local metabolism and flow. This is probably due to the fact that, in addition to estimated Vmax values, local substrate affinity (Km values) and substrate concentrations affect the metabolite fluxes. However, the latter two variables remain normally unknown. In contrast, valuable insight has been obtained concerning flow-metabolism matching from tissue metabolite measurements, especially when connected with mathematical model analyses. The latter permitted the calculation of metabolic flux rates (e.g., production of oxidation water, citric acid cycle flux, glucose uptake, fatty acid uptake) or the translation of the metabolic indexes into physiologically meaningful local metabolite concentrations (e.g., free cytosolic adenosine). The bottom line of the studies reported to date is that the broad range of myocardial flows observed under resting control conditions correlates with local metabolism possibly affected by spatial differences in adrenergic stimulation. Thus, high flow samples exhibit a higher oxidative metabolism than low flow samples. As a result the flow threshold below which local myocardial ischemia ensues is higher in control high flow samples. The importance of these findings with respect to local flow-metabolism matching is underlined by the finding that the probability of developing an infarction following ischemia/reperfusion is related to the functional state of the myocardium under control conditions, i.e., the local level of flow-metabolism matching.

Animals↗
PubMed2003

Radiofrequency treatment weakens the fatigue characteristics of rabbit anterior cruciate ligament.

OBJECTIVE: To evaluate the radiofrequency treatment applied to an intact anterior cruciate ligament, and to quantify the mechanical effects of controlled cyclic loading (simulating activities of daily living) post-treatment. DESIGN: An in vitro radiofrequency energy application to the rabbit anterior cruciate ligament and cyclic loading of the treated ligament. BACKGROUND: Effect of cyclic loading on the radiofrequency treated ligament in a controlled environment is not known. METHODS: In the treatment group radiofrequency treatment was applied to an intact ligament and then the ligament was cyclically loaded for 3000 cycles, and stretched-to-failure. Control group was similar to treatment, except that the radiofrequency treatment was not applied. The cyclic loading (approximately 6% tensile strain) was kept below the injury threshold of the rabbit anterior cruciate ligament and was designed to simulate loading post-treatment. A relaxation test (5% constant strain for 180 s) was used to compare the results at different steps in the experiment; within each group and between the two groups. RESULTS: Relaxation force increased in the treatment group (average 108% of intact, P<0.05), but decreased after the cyclic loading (average 71% of intact, P<0.05). There were significant differences in the force-deformation-failure curves between the treatment and control groups: average treated ligament failed at 59% and 57% of the control values respectively for the deformation and force (P<0.05). CONCLUSIONS: Using radiofrequency treatment makes rabbit anterior cruciate ligament weaker following cyclic loading. RELEVANCE: The radiofrequency treatment weakens the anterior cruciate ligament, and therefore, it perhaps should be protected until healing and adaptation restore its full strength.

Activities of Daily Living↗
PubMed1999

Computerized monitoring of physical activity and sleep in postoperative abdominal surgery patients.

OBJECTIVE: Assessment of early postoperative activity is important in the documentation of improvements of peri-operative care. This study was designed to validate computerized activity-based monitoring of physical activity and sleep (actigraphy) in patients after abdominal surgery. METHODS: The study included twelve hospitalized patients after major abdominal surgery studied on day 2 to 4 after operation and twelve unhospitalized healthy volunteers. Measurements were performed for 24 consecutive hours. The actigraphy measurements were compared with self-reported activity- and sleep registration. The actigraphy output was obtained by the zero-crossing mode (ZCM) and time-above-threshold mode (TATM). RESULTS: The overall results showed comparable mean agreement between actigraphy and self-reported activity registrations for patients of 80% (SD 12%) and volunteers of 84% (SD 6%) (p = 0.15). In both study groups, all correlation coefficients between actigraphy measurements and self-reported activity data were statistically significant (r, values for patients 0.4 to 0.8 and volunteers 0.6 to 0.9). A higher mean agreement between automated actigraphy sleep detection and self-reported sleep registration were found in the volunteers (85%, SD 15%) compared with the patients (77%, SD 11%) (p < 0.05). The mean activity value awake was higher in the volunteers than in the patients (p < 0.05). CONCLUSION: Computerized activity monitoring by actigraphy is a reliable and easy method for monitoring physical activity and sleep-wake cycles after major abdominal surgery.

Abdomen↗
PubMed2005

Physiological control of diving behaviour in the Weddell seal Leptonychotes weddelli: a model based on cardiorespiratory control theory.

Despite being obligate air breathers, many species of marine mammal are capable of spending most of their lives submerged in water. How they do this has been a subject of intense interest to physiologists for over a century, yet we still do not have a detailed understanding of the physiological mechanisms underlying this behaviour. What are the proximate mechanisms that trigger the 'decisions' to submerge and return to the surface? The present study proposes a model intended to address this question, based on fundamental concepts of cardiorespiratory control. Two basic hypotheses are examined by computer simulation, using a mathematical model of the mammalian cardiorespiratory control system with parameter values for an adult Weddell seal: (1) that the control of diving can be considered to be a respiratory control problem, and (2) that dives are initiated and maintained by disfacilitation of respiratory drive, not inhibition. Computer simulations confirmed the plausibility of these hypotheses. Simulated diving behaviour and physiological responses (ventilation, cardiac output, blood and tissue gas tensions) were consistent with published data from freely diving Weddell seals. Dives up to the estimated aerobic dive limit (ADL, 18-25 min) could be simulated without the need for active inhibition of breathing in this model. This theoretical analysis suggests that the most important physiological adjustments occur during the surface interval phase of the dive cycle and include hyperventilation accompanied by high cardiac output, appropriate regulation of cerebral blood flow and central chemoreceptor threshold shifts. During dives, cardiac output, distribution of peripheral blood flow, splenic contraction and peripheral chemoreflex drives were found to modulate physiological and behavioural responses, but were not essential for simulated dives to occur. The main conclusion from this study is that the central chemoreceptor may be an important mechanism involved in the regulation of diving behaviour, implying that CO2, not O2, is the key regulatory variable in this model. This model includes and extends the ADL concept and suggests an explicit mechanism by which the respiratory control system may play a central role in the regulation of diving behaviour. It is likely that respiratory mechanisms are an important component of a hierarchical behavioural control system and further studies are required to test the qualitative and quantitative validity of the model.

Animals↗
PubMed1999

Pollen recovery in atmospheric samples collected with the Rotorod Sampler over multiple-day periods such as weekends.

BACKGROUND: Conventional wisdom holds that multiple-day samples should not be obtained with the Rotorod Sampler because sampling efficiency declines over long sampling periods such as weekends. OBJECTIVE: The purpose of this present investigation was to test this position under experimental conditions. METHODS: Atmospheric pollen samples were collected over 24-hour, 48-hour, and 72-hour periods by five Rotorod Samplers operated in a compact sampling array. Pollen counts obtained from the latter two sampling periods were compared with corresponding values computed from 24-hour samples. Differences in pollen recovery were assessed using Pearson's correlation coefficient and paired comparisons t-tests. RESULTS: Two hundred seventeen atmospheric samples were obtained between March 30 and October 8, 1998. Differences between the 48-hour and 72-hour samples and their computed counterparts were not statistically significant when the atmospheric pollen concentration was less than 100 pollen grains per cubic meter of air (p/m3). At higher pollen concentrations large quantitative and statistically significant differences were noted. CONCLUSIONS: These data suggest that particle loading on Rotorod collector rods caused sample quality to deteriorate when atmospheric pollen concentrations exceed 100 p/m3. Multiple-day sampling periods appear to be justified when the atmospheric pollen concentration is less than this threshold. Adjusting the Rotorod Sampler's duty cycle may offer a means to collect samples over periods longer than 24 hours during times of the year when pollen shed is heavy.

Air Pollution↗
PubMed1994

Cardiopulmonary exercise testing in the evaluation of patients with ventilatory vs circulatory causes of reduced exercise tolerance.

INTRODUCTION: Cardiopulmonary exercise testing (CPX) is considered a useful procedure in the evaluation of circulatory, ventilatory, or mixed origin of reduced exercise tolerance. Our study was designed to compare CPX and a standard clinical-instrumental approach in the evaluation of patients with cardiopulmonary disorders. METHODS: Fifty-seven patients (31 male, 26 female; mean [+/- SE] age, 60 +/- 2 years) were studied. Each patient was evaluated by two different observers: one used standard clinical criteria, the other used gas exchange indexes, monitored during a maximal incremental CPX, performed on a cycle ergometer. Cardiac output (CO), at rest and at submaximal work level, was also obtained. RESULTS: In 46 patients (80.7 percent), a concordant evaluation was reached by the two observers (24 were found to have a predominant ventilatory disorder, 22 to have a circulatory disorder); among these, in subjects considered to have circulatory impairment, the maximal CO/maximal workload ratio was significantly lower than in the ventilatory group; in those with ventilatory impairment, the reduced exercise tolerance correlated with the resting spirometric values. In the remaining 11 patients (19.3 percent), CPX better defined the underlying pathophysiology of exercise limitation: in 10 of them, clinically classified as having a mixed or predominantly ventilatory disorder, a greater importance of the circulatory component was detected; 4 had evidence of pulmonary vascular impairment (high VE/VCO2 at anaerobic threshold). CONCLUSIONS: Our study confirmed the sensitivity of CPX in the evaluation of a reduced exercise tolerance in dyspneic patients with cardiopulmonary conditions; when compared with a clinical-laboratory approach, in some patients it allowed the detection of an underestimated circulatory component causing exercise limitation.

Aged↗
PubMed1992

Optimal diaphragmatic blood perfusion.

The intrabreath time course of phrenic artery blood perfusion (Qpha) was studied in five anesthetized dogs. The diaphragm was paced with submaximal levels of stimulation at various duty cycles (DC) to achieve tension-time index below and above the fatigue threshold (0.03-0.60). Left Qpha was measured via Doppler technique during control (inactive diaphragm) and during two submaximal levels of bilateral phrenic nerve stimulation sustained for 1 min. Measurements were done when Qpha reached steady state in each run. The frequency of pacing of each run was 10/min, and the DC ranged from 0.1 to 0.9 in 0.1 increments. Shortening of costal and crural segments was measured by sonomicrometry. It was found that Qpha during the diaphragmatic contraction phase (QphaC) was a sigmoidal function of DC and was not affected by the levels of transdiaphragmatic pressure (Pdi) explored (34-64% of maximal Pdi). Qpha during the diaphragmatic relaxation phase (QphaR) was a parabolic function of the DC, reaching an optimal value at DC of approximately 0.3 at any given Pdi. QphaR increased significantly with the preceding level of Pdi. QphaT (the sum of QphaC and QphaR) was a parabolic function of DC, reaching peak values at DC of 0.4-0.6 and then decreasing. This function was similar at two levels of Pdi. Post-pacing hyperemia was directly related to tension-time index greater than 0.20.

Animals↗
PubMed1992

Sensitivity and specificity of bronchial provocation testing. An evaluation of four techniques in exercise-induced bronchospasm.

The thresholds used to define a positive result for bronchial provocation challenges (BPC) are arbitrary. Requiring smaller decrements in expired flow to define a positive study would capture more cases of reactive airways (increased sensitivity) but would include some "normal" responses (decreased specificity). To examine the relationship between threshold definition and the ability to correctly classify subjects as either normal or as having airways hyperresponsiveness (AHR), four different BPC tests were administered on different days to 20 patients with a clinical diagnosis of exercise-induced bronchospasm (EIB) and 20 control subjects. The four BPC tests were indoor exercise on a cycle ergometer, methacholine inhalation challenge (MIC), eucapnic voluntary hyperventilation (EVH) with dry gas, and EVH with cold gas. Our results indicate that the thresholds which best separate the two groups are different for each of the four BPC techniques. For methacholine inhalation (MIC), a fall in FEV1 (d%FEV1) of 15 percent or greater at 188 cumulative breath units was 100 percent specific for AHR but had a sensitivity of only 55 percent. Eucapnic voluntary hyperventilation (EVH) with room temperature dry gas was 100 percent specific at a d%FEV1 of 11 percent, but, at that threshold, sensitivity was only 50 percent. EVH with cold air was 100 percent specific at a d%FEV1 of 12 percent but sensitivity was only 35 percent. The bicycle ergometer challenge was far too insensitive to be of value in evaluating AHR. Based on their respective receiver operating characteristic curves, the best separation of the two subject groups occurred at a d%FEV1 of 5 percent and 12 percent for the two EVH techniques and MIC, respectively. An individual's response to one test was highly correlated with the response to either of the other two (r = 0.66, p less than 0.001 for dry vs cold gas EVH; r = 0.56, p less than 0.001 for dry gas EVH vs methacholine; and r = 0.69, p less than 0.001 for cold gas EVH vs methacholine). Thus, MIC and EVH techniques are equally useful in defining AHR and each has its optimal threshold for a positive test result.

Adult↗
PubMed1986

Changes in plasma progesterone, estradiol, follicle-stimulating hormone and luteinizing hormone during diestrus and ovulation in rats with 5-day estrous cycles: effect of antibody against progesterone.

Progesterone secretion remained significantly higher during diestrus in the 5-day cyclic rat than in the 4-day cyclic animal. Injection of a sufficient amount of antiprogesterone serum (APS) at 2300 h on metestrus in a 5-day cycle advances ovulation and completion of the cycle by 1 day in the majority of animals (75 and 80%, respectively). Progesterone (250 micrograms) administered with APS eliminated the effect of the antiserum. Within 2 h after administration of APS, levels of both follicle-stimulating hormone (FSH) and luteinizing hormone (LH) elevated significantly, while a significant elevation of plasma estradiol above the control value followed as late as 36 h after the treatment. None of the 5-day cyclic rats treated with APS showed ovulatory increases of FSH and LH at 1700 h on the second day of diestrus, although 3 of the 4 animals receiving the same treatment ovulated by 1100 h on the following day. The onset of ovulatory release of gonadotropins might have been delayed for several hours in these animals. These results indicate that recurrence of the 5-day cycle is due to an elevated progesterone secretion on the morning of diestrus, and suggest that a prolongation of luteal progesterone secretion in an estrous cycle suppresses gonadotropin secretion. Rather than directly blocking the estrogen triggering of ovulatory LH surge, the prolonged secretion of luteal progesterone may delay the estrogen secretion itself, which decreases the threshold of the neural and/or hypophyseal structures for ovulatory LH release.

Animals↗
PubMed1998

Cardiopulmonary responses to exercise in patients with hypertrophic cardiomyopathy.

OBJECTIVE: To examine the submaximal and maximal indices of the exercise response of patients with hypertrophic cardiomyopathy. DESIGN AND SETTING: Prospective examination of cardiopulmonary responses to ramp exercise test of a consecutive group of patients with hypertrophic cardiomyopathy attending a cardiomyopathy outpatient clinic. METHODS: 50 patients aged 12 to 76 years (mean (SD) 35 (14)) with diagnosis of hypertrophic cardiomyopathy performed incremental cycle ergometry; 22 sedentary volunteers (seven female, 15 male) aged 14 to 58 years (mean (SD) 31 (12)) served as controls. Respiratory gas was continuously sampled from the mouth-piece, and its concentration profile phase aligned to the respired air flow signals. Following analogue to digital conversion, gas exchange variables were computed breath by breath and the data were averaged every 30 seconds for graphic display. A 12 lead ECG was monitored continuously and recorded every three minutes during the exercise. RESULTS: Both the peak oxygen uptake attained on the test (VO2 peak) and anaerobic threshold were reduced in patients with hypertrophic cardiomyopathy compared with the control group (p < 0.0001). In 29 patients (59%) the VO2 peak was less than 60% and only two patients achieved a peak above 80% of their predicted values. The anaerobic threshold was below 60% of the predicted value in 31 patients and above 80% in only three patients. The slope of oxygen uptake/work rate relation (delta VO2/delta WR) was decreased in 16 patients (32%). The maximum oxygen pulse (VO2/HR) was reduced as a percentage of the predicted value, and became flat at high work rates in 32 patients. There was a significant correlation between anaerobic threshold and VO2 peak (p < 0.0001), work efficiency (p < 0.0001), and maximum oxygen pulse (p < 0.0001). The slope of change in ventilation against change in carbon dioxide output (delta VE/delta VCO2) for the subanaerobic threshold range was increased in 36 patients (72%) and was inversely correlated with anaerobic threshold (p < 0.0002). CONCLUSIONS: There were severe abnormalities in maximal and submaximal indices of pulmonary gas exchange in a cohort of hypertrophic cardiomyopathy patients attending a referral cardiovascular clinic. The pattern of the abnormalities suggests that a reduced stroke volume response, ventilation/perfusion mismatch, and abnormal peripheral oxygen utilisation are the possible mechanisms of exercise intolerance.

Adolescent↗
PubMed1997

24 h rhythm of the ventricular fibrillation threshold during normal and hypoventilation in female Wistar rats.

A 24 h rhythm of the ventricular fibrillation threshold (VFT) was investigated in female Wistar rats under conditions of normal ventilation (NV) (17 animals) and hypoventilation (HV) (10 animals). The animals were adapted to a daily 12:12 h light-dark cycle with the dark period from 18:00 to 06:00 under constant temperature conditions. The experiments were performed in pentobarbital anesthesia (40 mg/kg ip, open chest experiments) during the whole year, and the obtained results were averaged independently of the seasons. During NV, the VFT in female rats showed a significant 24 h rhythm (p < 0.01) with the mesor 2.59 +/- 0.53 mA, amplitude 0.33 +/- 0.11 mA, and acrophase -338 degrees (at 22:53 h) and the confidence intervals from -288 degrees to -7 degrees (from 19:12 to 00:28 h) using the population mean cosinor test. The maximal values of the VFT were measured in the active phase between 24:00 and 03:00 h. During HV, the rhythmicity of the VFT showed a more pronounced biphasic character with a smaller peak between 15:00 h and 18:00 h hours and a higher peak between 24:00 h and 03:00 h of the daily regime. Hypoventilation significantly decreased the VFT (p < 0.001) at each interval of the measurement. It is concluded that the electrical stability of the heart measured by the VFT shows a significant 24 h rhythm in female Wistar rats and that HV decreased the VFT during the whole 24 h period.

Animals↗
PubMed1991

Effects of strength training on lactate threshold and endurance performance.

To determine the effects of 12 wk of strength training on lactate threshold (LT) and endurance performance, 18 healthy untrained males between 25 and 34 yr of age were randomly assigned to either strength training (N = 10) or control (N = 8) groups. Despite no changes in treadmill VO2max or cycle peak VO2, a 33 +/- 5% increase (P less than 0.001) in cycling time to exhaustion at 75% of peak VO2 was observed following training. No significant changes in cycling time were observed in the control group. There were significant reductions in plasma lactate concentration at all relative exercise intensities ranging between 55 and 75% of peak VO2 training. The improved endurance performance was associated with a 12% increase in LT (r = 0.78, P less than 0.001). The strength training program resulted in significant improvements (P less than 0.001) of 31 +/- 5% and 35 +/- 7% in isokinetic peak torque values for leg extension and flexion, respectively, at a velocity of 30 degrees.s-1. There were also significant increases in 1-RM values of 30 +/- 4% (P less than 0.001) for leg extension, 52 +/- 6% (P less than 0.001) for leg flexion, and 20 +/- 4% (P less than 0.001) for the bench press. These findings indicate that strength training improves cycle endurance performance independently of changes in VO2max. This improved performance appears to be related to increases in LT and leg strength.

Adult↗
PubMedDate not supplied

Secular trend in peak oxygen consumption among United States youth in the 20th century.

The purpose of this study was to examine secular change in peak oxygen consumption (Vo(2)) in U.S. boys and girls using available data from the 20th century. Studies were primarily identified from review articles and a Medline search. To be included in the analysis, studies must have included direct measurement of peak Vo(2) on healthy (free from overt disease) United States children and youth from the general population separated by sex. Data (mean values) were divided by decade and separated into three age groups: 6-12, 13-15, and 16-18 years for boys, and 6-11, 12-14, and 15-18 years for girls. Peak Vo(2) values were expressed as related to bipedal locomotion; therefore, cycle ergometry values were corrected by a factor of 1.075. Mean values were fit by least squares, goodness-of-fit regression lines. Results indicate that absolute (L x min(-1)) and relative (ml x kg(-1) x min(-1)) peak Vo(2) have remained relatively stable among boys and young girls. In adolescent girls, particularly those 15 years of age and older, peak Vo(2) has decreased by approximately 20% over the past few decades. The available data indicate that aerobic fitness has not decreased in United States youth except in adolescent girls over the past few decades.

Adolescent↗
PubMed1993

What limits endurance in normal children?

We have compared the results of a standard progressive maximal exercise test to those of an endurance exercise test in 22 healthy school children (13 girls, 9 boys, mean age 14.8 years) in order to examine whether it is possible to extrapolate results from a maximal test to predict their endurance capacity. All children performed a standard progressive maximal exercise test (15 W increments every minute until exhaustion) and an endurance test (individually calculated loads to mimic cycling at 20 km/h against a windforce 5 of Beaufort for 30 minutes) on 2 separate days. In both tests metabolic [oxygen uptake (VO2), CO2 production, blood lactate accumulation], ventilatory [minute ventilation (VE)], and circulatory variables were measured. From the maximal test the threshold of lactate accumulation (LT) was determined. Thirteen children were capable of enduring the 30 minute exercise (Group 1), and 9 could not complete the endurance test (Group 2). These two groups were comparable with respect to age, height, and baseline lung function. Children in Group 2 had a higher mean weight (P < 0.005) than those in Group 1. Eight of the 9 children in Group 2 were girls, whereas Group 1 consisted of 5 girls and 8 boys. There was no significant difference between Group 1 and 2 in the mean values of VO2 max, maximal respiratory exchange ratio (R max), VEmax, LT, oxygen pulse, and other variables obtained during the maximal exercise tests. Lactate accumulation during the endurance test in Group 2 was larger than in Group 1 (P < 0.005).(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1981

Influence of diet on CO2 production and ventilation in constant-load exercise.

The coupling between ventilation (VE) and oxygen uptake (VO2) or carbon dioxide production (VCO2) was tested during constant-load cycle ergometry in five healthy, young female volunteers. The ratio of VCO2/VO2 (respiratory quotient, RQ) was altered during exercise by prior dietary manipulation involving three diets: (a) low carbohydrate (L), (b) high carbohydrate (H) and (c) normal, mixed (M) diet. The constant power output selected for a 10-min exercise period approximated 80% of the power output at the anaerobic threshold. At rest and during exercise, the RQ and blood lactate concentration were lower following the L diet than either the H or M diets. All measurements for the H and M diets were similar. In exercise, the VO2 was higher in the L diet (1428 ml/min) than the H diet (1293 ml/min) (P less than 0.05). Although the VCO2 tended to be lower and the VE higher during exercise in the L diet, these values were not significantly different from the H dit. The ratio of VE/VO2 was not different fro the two diets. In the L diet, VE/VCO2 was greater than the H diet (P less than 0.05). A kinetic analysis showed no differences as a consequence of the diets in the rate of adaptation of VO2, VCO2 or VE to the plateau levels. This study has demonstrated an uncoupling of the constant relationship between VE and VCO2 by prior dietary manipulation; however, the relationship between VE and VO2 remained constant in spite of a change in the metabolic RQ which altered VO2 and VCO2 at a constant power output.

Adult↗
PubMed2000

The effects of hyperoxia on performance during simulated firefighting work.

This study evaluated the effects of hyperoxia (inspired oxygen fraction = 40%) on performance during a simulated firefighting work circuit (SFWC) consisting of five events. On separate days, 17 subjects completed at least three orientation trials followed by two experimental trials while breathing either normoxic (NOX) and hyperoxic (HOX) gas mixtures that were randomly assigned in double-blind, cross-over design. Previously, ventilatory threshold (Tvent) and VO2max had been determined during graded exercise (GXT) on a cycle ergometer. Lactate concentration in venous blood was assessed at exactly 5 min after both the experimental trials and after the GXT. Total time to complete the SFWC was decreased by 4% (p < 0.05) with HOX. No differences were observed in individual event times early in the circuit, however HOX resulted in a 12% improvement (p < 0.05) on the final event. A significantly decreased rating of perceived exertion (RPE) was also recorded immediately prior to the final event. No differences were observed in mean heart rate or post-exercise blood lactate when comparing NOX to HOX. Heart rates during the SFWC (both conditions) were higher than HR at Tvent, but lower than HR at VO2max (p<0.05). Post-SFWC lactate values were higher (p<0.05) than post-VO2max. These results demonstrate that hyperoxia provided a small but significant increase in performance during short duration, high intensity simulated firefighting work.

Adult↗
PubMed1984

Physiologic and anthropometric factors underlying endurance performance in children.

This study investigated the relationship between endurance performance and several measures of aerobic, anaerobic, and morphological fitness in 30 girls and 28 boys, 10 to 14 years of age. A multistage treadmill test was used for assessment of VO2 max (ml X kg-1 X min-1) and anaerobic threshold (AT) expressed both in absolute (AT-VO2) and relative (% VO2 max) terms. Anaerobic capacity (AC) was measured in a 30-s cycling task and expressed as kpm . kg of body weight-1 X min-1. Percent fat was estimated from skinfolds. The correlations between these measures and 2-km run time were: -0.73, -0.73, -0.50, -0.77, and 0.55 for VO2 max, AT-VO2, AT-%VO2 max, AC, and percent fat, respectively. When entered into a forward selection multiple regression with run time as the dependent variable, AC accounted for 59.5% of the variance and VO2 max accounted for an additional 6.9%, with AT and percent fat making no significant additional contribution. When the girls and boys were compared, no reliable differences were found for run time and AC. The boys exhibited reliably higher values for VO2 max and AT-VO2. No reliable difference in percent fat was found for the younger boys and girls, but the older girls were significantly fatter than the older boys. Thus, in children 10 to 14 there is a substantial relation between measures of anaerobic and aerobic function, although to some extent they provide independent information about endurance performance.(ABSTRACT TRUNCATED AT 250 WORDS)

Adipose Tissue↗
PubMed2004

Prediction of pregnancy by intrauterine insemination using CASA estimates and strict criteria in patients with male factor infertility.

This study was performed to predict pregnancy by intrauterine insemination (IUI) using computer-aided sperm analysis (CASA) estimates and strict criteria in patients with male factor infertility. IUI was performed in 682 cycles on 160 male factor infertile patients. Semen examinations were carried out by CASA and strict criteria before and after sperm preparation using continuous-step density gradient centrifugation. Receiver operating characteristics (ROC) curves were constructed for assessment of the effectiveness of each individual parameter in predicting pregnancy by IUI. A clinically acceptable threshold was calculated when sensitivity plus specificity were maximum. The average cycle of IUI performed was 4.3 +/- 2.4. Pregnancy rate per cycle and per patient were 7.2% (49/682) and 28.1% (45/160), respectively. Using ROC curve, it was shown that normal sperm morphology assessed by the strict criteria before sperm separation and five parameters after sperm separation including rapid, progressive motility, average path velocity (VAP), curvilinear velocity (VCL), and straight line velocity (VSL) were able to predict pregnancy by IUI. Correlation between sperm parameters and pregnancy outcome was examined by the logistic regression model. In a multivariate analysis normal morphology before sperm separation >or=15.5% [odds ratio (OR) = 2.2, p = 0.02], rapid after sperm separation >or=25.5% [OR = 3.9, p = 0.029], and VCL after sperm separation >or=102.65 microm/sec [OR = 3.2, p = 0.002] were the parameters of predictive value for pregnancy outcome. Adjustment of the model for female age, female infertility factors, and the methods of ovulation induction did not change this finding, and the final model still had the same covariates. Pregnancy rates per cycle according to the number (0, 1, 2 and 3) of variables satisfied with the three parameters were 0% (0/110), 1.6% (3/183), 9.7% (21/217) and 15.1% (23/151), respectively. Three semen parameters including normal morphology before sperm separation, rapid and VCL after sperm separation were identified as predictors of pregnancy by IUI. These variables would be helpful when counselling patients before they make the decision to proceed with in vitro fertilization (IVF)/intracytoplasmic sperm injection (ICSI)-ET.

Adult↗