Differential effects of airway anesthesia on ozone-induced pulmonary responses in human subjects.

We examined the effect of tetracaine aerosol inhalation, a local anesthetic, on lung volume decrements, rapid shallow breathing, and subjective symptoms of breathing discomfort induced by the acute inhalation of 0.30 ppm ozone for 65 min in 22 ozone-sensitive healthy human subjects. After 50 min of ozone inhalation FEV(1) was reduced 24%, breathing frequency was increased 40%, tidal volume was decreased 31%, and total subjective symptom score was increased (71.2, compared with 3.8 for filtered air exposure). Inhalation of tetracaine aerosol resulted in marked reductions in ozone-induced subjective symptoms of throat tickle and/or irritation (92.1%), cough (78.5%), shortness of breath (72.5%), and pain on deep inspiration (69.4%). In contrast, inhalation of tetracaine aerosol (mass median aerodynamic diameter of 3.52 microm with a geometric standard deviation of 1.92) resulted in only minor and inconsistent rectification of FEV(1) decrements (5.0%) and breathing frequency (-3.8%) that was not significantly different from that produced by saline aerosol alone (FEV(1), 5.1% and breathing frequency, -2.7%). Our data are consistent with afferent endings located within the large conducting airways of the tracheobronchial tree being primarily responsible for ozone-induced subjective symptoms and provides strong evidence that ozone-induced inhibition of maximal inspiratory effort is not dependent on conscious sensations of inspiratory discomfort.

Ozone dose-response effects of varied equivalent minute ventilation rates.

While it is well known that exercise minute ventilation (V(E)) results in greater pulmonary function and subjective symptoms (SS) responses upon exposure to a given ozone (O3) dose, the magnitude of V(E) increase to produce a significant forced expiratory volume in 1 s (FEV1.0) response compared to that observed at a lower exercise V(E) for the same O3 concentration and exposure time is unclear, especially in prolonged (i.e., >2 h) exposures. Further, in prolonged exposures, the relationship of body size to FEV1.0 response to a given O3 exposure dose has not been systematically examined. In the present study, 30 young adults were exposed on four occasions for 6 h (during a 6.6-h period) to constant 03 levels of zero (filtered air, FA) or 0.12 parts per million (ppm). At the latter concentration, exercise V(E) was varied in exposures to 17, 20, and 23 l min(-1) m(-2) of BSA, respectively, for each individual to achieve an equivalent ventilation rate, EVR). In the FA exposure, EVR was 23 l min(-1) m2. Percent changes in FEV1.0 for the three 0.12 ppm O3 exposures were significantly greater than that for FA, but did not differ significantly from each other. For the 6.6-h exposures, exercise EVR at or in excess of 17 l min(-1) m(-2), SS values were significantly greater than those observed for the FA protocol. Further, SS values at 6.6 h of exposure to 0.12 ppm O3 for the exercise EVR of 23 l min(-1) m(-2) protocol were significantly greater than for the 0.12 ppm O3 exercise EVR of 17 l min(-1) m(-2) protocol. To achieve a widened EVR, two 1-h exposures to 0.30 ppm O3 with continuous exercise (CE) at a level necessitating an EVR of 17 and approximately 34 l min(-1) m(-2), respectively, were completed by each subject. All postexposure pulmonary function and SS responses were significantly greater for the higher 1-h EVR protocol. In all exposures with significant O3-induced changes in FEV1.0 and SS, it was found that the smaller subjects who exercised at the lowest absolute V(E) had significantly smaller responses than did the larger subjects. These results strongly suggest that for the O3 concentrations and exposure durations used in this study, the effect of V(E) on O3-induced FEV1.0 and SS responses is not body-size-dependent.

Feasibility study of prolonged ozone inhalation exposure via face mask.

Because of the interest attendant to establishing an 8-h ozone (O(3)) federal air quality standard, acute pulmonary function responses to prolonged (6.6 to 8 h) O(3) exposure between 0.08 and 0. 24 ppm have been examined in chamber studies. Given time constraints for O(3) concentration changes in room-sized chambers and the need to simulate rapid fluctuations in O(3) levels, such as occurs when one goes from indoors to outdoors during an air pollution episode, mouthpiece or face-mask exposure systems offer potential advantages over chamber exposure systems. In a recent study in this laboratory, subjects indicated that over 2 h of continuous exposure via an obligatory mouthpiece inhalation system (with noseclip) was more than they could tolerate with this type of exposure system. The purpose of this study was to compare O(3)-induced responses observed following 2-h exposures via an obligatory mouthpiece inhalation system and a newly devised face-mask exposure system, and to determine whether the latter could be tolerated during 4-h exposures. Six young adults completed 5 experimental protocols (three 2-h and two 4-h) while exposed to O(3) concentrations ranging from 0.00 ppm (filtered air) to 0.24 ppm. Exercise and resting minute ventilation (V(E)) were measured continuously. Pulmonary function, subjective symptoms (SS) of breathing discomfort, and exercise ventilatory pattern responses were obtained. Exposure to 0.24 ppm O(3) with intermittent exercise (IE) for 2 h via a newly devised inhalation system, consisting of a nylon plastic non-rebreathing respiratory valve and a silicone rubber face mask with Teflon overlay on the inner surface, yielded pulmonary function, SS, and exercise ventilatory pattern responses nearly identical to those obtained in the same O(3) exposure effected via a Teflon-coated Hans-Rudolph respiratory valve obligatory mouthpiece inhalation system. It was concluded that the newly devised face-mask inhalation system was well tolerated by all subjects during the 4-h exposure protocols, with each subject indicating that longer 6.6-h exposures with this system would be tolerable.

Effects of physical activity, body weight and composition, and muscular strength on bone density in young women.

OBJECTIVE: The purpose of this study was to examine the relationship between body weight and composition, muscular strength, physical activity, and bone mineral density (BMD) in eumenorrheic college-aged women. METHODS: BMD and bone mineral content (BMC) of the total body, and BMD of the lumbar spine (L2-L4) and femoral neck (via dual energy x-ray absorptiometry), as well as body composition and muscular strength, were measured in 60 college-aged women. The women were divided into three groups: 1) low body weight athletes involved in weight-bearing, collegiate sports (N = 20), 2) matched low body weight and sedentary (N = 20), and 3) average body weight and sedentary (N = 20). All groups were matched for height, age, and age at menarche. RESULTS: The athletes had significantly greater (P < 0.05) (mean +/- SD) total body BMD (1.164 +/- 0.06 g x cm[-2]), L2-L4 BMD (1.240 +/- 0.13 g x cm[-2]), femoral neck BMD (1.144 +/- 0.13 g x cm[-2]) and total body BMC (2.44 +/- 0.30 kg) than the low body weight, sedentary (LWS) group, but were only greater than the average body weight sedentary group (AWS) for femoral neck BMD. Significant correlations were found between lean body mass (LBM) and all BMD variables (P < 0.001). A significant correlation (P < 0.01) was found between fat mass and all BMD variables in the sedentary subjects alone (N = 40), but with inclusion of the athletes (N = 60), none of the correlations between fat mass and BMD were significant. Arm and leg strength isometric torque values corrected for muscle + bone cross-sectional area (M + B CSA) were not significantly different between the athletes and LWS group, but the athletes were greater (P < 0.05) than the AWS group for both arm and leg strength/M + B CSA. No significant, site-specific correlations were found between strength/M + B and BMD. CONCLUSIONS: In summary, the athletes had significantly greater BMD, BMC, and LBM than the LWS group and, except for a greater femoral neck BMD, similar BMD, BMC, and LBM as the AWS group. These results suggest that LBM and weight-bearing exercise both enhance BMD in eumenorrheic young adult women.

Wet bulb globe temperature index and performance in competitive distance runners.

In 1974 two sets of heat stress guidelines, each based on the wet bulb globe temperature (WBGT) index, were designed for men's National Collegiate Athletic Association (NCAA) Championship Division I distance running competitions. One set of guidelines was established to minimize the chance of heat injury during distance running events. A second set was designed to predict heat stress related performance decrements. During the time the heat injury guidelines were used (1974-1993), no heat injuries were reported. The purpose of this study was to assess the accuracy of the performance decrement guidelines and determine whether the WBGT indices were linearly related to men's championship distance running performance. WBGT index data were collected during the 1500-, 3000-steeplechase (SC), 5000-, and 10,000-m events at men's NCAA Division I Track and Field Championships held from 1974 to 1981 (excluding 1975). These data were compared to the average running performance of the top six finishers in each event. Analysis of the accuracy of the NCAA performance decrement guidelines revealed four unexpected performances out of 28 predictions. Pearson product-moment correlation and linear regression analyses between the WBGT indices and performance revealed statistically significant linear relationships for the 3000-SC and 10,000-m events (P < 0.05). A significant linear relationship was also found when the 1500-, 3000-SC, 5000-, and 10,000-m results were pooled (P < 0.05). In conclusion, the NCAA guidelines were effective in preventing heat injury and fairly successful in predicting performance. However, a linear relationship between WBGT indices and distance running performance did not exist in all running events.

Dynamic ultrasonographic measurement of passive coxofemoral joint laxity in puppies.

A new method of dynamic ultrasonographic evaluation of passive coxofemoral joint laxity was used to examine a total of 30 greyhound (n = 13) and nongreyhound (n = 17) puppies. Puppies were evaluated sonographically at four, six, eight, 12, 16, and 26 weeks of age. The coxofemoral joints were distracted manually, and the femoral head displacements were measured during distraction. The greyhounds had significantly smaller (p less than 0.01) maximum distraction distance (mean +/- standard deviation [SD], 0.11 +/- 0.04 cm) than nongreyhound puppies (mean +/- SD, 0.26 +/- 0.10 cm). In six- to eight-week-old puppies, the maximum distraction distance was correlated significantly (p of 0.0001, adjusted correlation coefficient [r2] of 0.27) with stress radiographic indices. Coxofemoral joints interpreted as being abnormal on hip-extended radiographs taken at one year of age were associated significantly (p of 0.0001) with higher maximum distraction distances in six- to eight-week-old puppies.

Bone density and cyclic ovarian function in trained runners and active controls.

This study was conducted to determine whether rigorous exercise training adversely affects ovarian hormone levels and bone health in cyclically menstruating trained runners. Ovarian hormones, bone mineral density (BMD), body composition, 3-d diet records, 3-d estimated energy expenditure, and menstrual histories were evaluated in 10 trained collegiate runners and 10 moderately active controls. The trained runners had lower total body calcium per kg of soft lean tissue measured by DEXA (P = 0.045). Half of the trained runners had experienced stress fractures compared with only one of the moderately active controls. The trained runners' lumbar (L2-L4) BMD (1.178 g.cm-2) was not significantly different from that of the active controls (1.283 g.cm-2) (P = 0.074) but, for all subjects combined, there wasa significant inverse relation between L2-L4 BMD and distance run per week (P = 0.036). Further, adding age, body weight, percent body fat, daily energy intake, and daily calcium intake to a stepwise multiple regression analysis did not significantly improve predictive precision. The trained runners consumed nearly twice the amount of calcium (1089 mg.d-1 vs 641 mg.d-1, respectively; P = 0.036), while intake of other nutrients did not differ significantly between groups. Urinary estrone conjugates (E1C) were lower in the trained runners during the early follicular phase (P = 0.028), while pregnanediol-3-glucuronide (PdG) was not significantly different between groups during the luteal phase (P = 0.213). Thus, it appears that lower estrogen production, especially during the early follicular phase, and not progesterone, is associated with lower whole body calcium per kg of soft lean tissue and, probably, L2-L4 BMD. Results of this study also suggest that regular menstrual cycles do not imply normal ovarian hormone function in young women who are engaged in either recreational or competitive running.

Effects of hypovolemia and posture on responses to the Valsalva maneuver.

INTRODUCTION: We tested the hypotheses that hypovolemia would result in attenuated elevation in blood pressure, greater baroreflex-mediated tachycardia, and reduced capacity for vasoconstriction during a Valsalva maneuver (VM). METHODS: Heart rate (HR) and mean arterial pressure (MAP) were measured beat-by-beat before strain, during a 15-s VM strain at 30 mmHg expiratory pressure, and post-strain. Eight subjects performed three VM trials in each of three postures (supine, sitting, and standing) under two experimental conditions (normovolemic and hypovolemic). Hypovolemia was acutely induced by a bolus injection of 30 mg furosemide. Each experimental condition was conducted on a different day, separated by one week. delta MAP was used in analyses of phase I, late phase II (an indicator of vasoconstriction) and phase III of VM. The ratio delta HR/delta MAP, an index of nonspecific baroreflex control of HR, was used in analysis of early phase II and phase IV of the VM. RESULTS: Compared to normovolemia, hypovolemia resulted in 12% lower plasma volume (p = 0.0001). delta MAP for both phase I and phase III of the VM differed between postures (p = 0.0132 and p = 0.0003, respectively) and was lower in the hypovolemic condition than in the normovolemic condition for phase I in the standing posture (-5 mmHg, p = 0.0385). CONCLUSIONS: HR and blood pressure responses to alterations in intrathoracic pressure are affected by fluid redistribution (posture change), but not by circulating blood volume. Therefore, our results did not support our hypothesis that hypovolemia would result in attenuated elevation in blood pressure, greater baroreflex-mediated tachycardia, and reduced capacity for vasoconstriction during a Valsalva maneuver. However, moderate hypovolemia can be specifically predicted by the phase I response to a VM performed in the standing posture.

Peak torque per unit cross-sectional area differs between strength-trained and untrained young adults.

It is unclear whether gender differences in the relative strength of the upper and lower body are due to differences in muscle mass distribution or dissimilarity of use. There is also controversy as to whether prolonged resistance training increases strength per unit cross-sectional area (CSA). To help resolve these questions, maximum isometric torque per unit muscle and bone (M+B) CSA was measured in the upper arm and thigh of 26 trained (13 males; 13 females) and 26 untrained (13 males; 13 females) young adults. Muscle and bone CSA values were calculated from limb circumferences and skinfolds. Maximal isometric torque values were recorded by a LIDO isokinetic dynamometer. There was no significant difference (P > 0.05) in mean upper arm or thigh torque per unit M+B CSA between the trained males and trained females, or between the untrained males and untrained females. However, mean torque per unit M+B CSA was significantly higher for the trained subjects of both genders compared with the untrained subjects of both genders for the upper arm (28.9%; P < 0.0001) and thigh (18.8%; P < 0.0001). These results suggest that muscle quality (peak torque/CSA) is equal between genders, and that the increase in muscle strength per unit area that occurs with resistance training is not gender-dependent.

Pulmonary function response to equivalent doses of ozone consequent to intermittent and continuous exercise.

The effects on pulmonary function of inhaling the same effective dose of ozone, as well as subjective responses during continuous exercise and intermittent exercise, were studied in 12 aerobically trained men. Each subject completed 1 h of continuous exercise at work rates that elicited a mean minute ventilation of 60 l/min, and two additional 2-h intermittent exercise exposures eliciting a mean exercise minute ventilation of 45-47 l/min (i.e., total minute ventilation for each protocol was approximately 3,600 l). Subjects were exposed in randomized sequence to 0.30 ppm ozone on three occasions and to filtered air on three occasions. Forced expiratory volume in 1 s decrements of -17.6%, -17.0%, and -17.9%, respectively, for the 1-h continuous exercise exposure and the two 2-h intermittent exercise exposures to 0.30 ppm ozone were significantly different. Exposure to ozone caused significant differences between postexposure subjective symptom responses; that is, responses associated with continuous exercise were greater than those for either intermittent exercise protocol. However, the overall symptom severity responses during the last minute of exercise for the two intermittent exercise protocols (at 90 and 105 min, respectively) were not significantly different from the continuous exercise postexposure value. The findings indicate that when the ozone effective dose is equivalent at a given ozone concentration, there is no difference between pulmonary function responses to continuous exercise or intermittent exercise exposures of 2-h duration (or less), although subjective symptoms are reduced somewhat during the last rest period of intermittent exercise.

Enhanced response to ozone exposure during the follicular phase of the menstrual cycle.

Exposure to ozone (O3), a toxic component of photochemical smog, results in significant airway inflammation, respiratory discomfort, and pulmonary function impairment. These effects can be reduced via pretreatment with anti-inflammatory agents. Progesterone, a gonadal steroid, is known to reduce general inflammation in the uterine endometrium. However, it is not known whether fluctuations in blood levels of progesterone, which are experienced during the normal female menstrual cycle, could alter O3 inflammatory-induced pulmonary responses. In this study, we tested the hypothesis that young, adult females are more responsive to O3 inhalation with respect to pulmonary function impairment during their follicular (F) menstrual phase when progesterone levels are lowest than during their mid-luteal (ML) phase when progesterone levels are highest. Nine subjects with normal ovarian function were exposed in random order for 1 hr each to filtered air and to 0.30 ppm O3 in their F and ML menstrual phases. Ozone responsiveness was measured by percent change in pulmonary function from pre- to postexposure. Significant gas concentration effects (filtered air versus O3) were observed for forced vital capacity (FVC), forced expiratory volume in 1 sec (FEV1), and forced expiratory flow between 25 and 75% of FVC (FEF25-75; p < .05). More importantly, the pulmonary function flow rates, FEV1 and FEF25-75, showed a significant menstrual phase and gas concentration interaction effect, with larger decrements observed in the F menstrual phase when progesterone concentrations were significantly lower. We conclude that young, adult females appear to be more responsive to acute O3 exposure during the F phase than during the ML phase of their menstrual cycles.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of bone density on body composition estimates in young adult black and white women.

Bone mineral content (BMC) and density (BMD) by dual x-ray absorptiometry, total body water (TBW) by the deuterium oxide (D2O) dilution technique, and body density (Bd) by hydrostatic weighing were measured in 26 black (B) and 26 white (W) young adult women. Both groups were similar in age, height, weight, and total skinfolds; however, black subjects had significantly higher BMC and BMD. Formulas to estimate percent body fat (%BF) from Bd included Siri's two-component equation for the reference man, which assumes a fat free body density (FFBd) of 1.100 g.ml-1, and an adjusted two-component formula that assumes a lower FFBd of 1.095 g.ml-1. Percent body fat was also predicted from TBW and by several multicomponent models that corrected for individual subject variation in measured BMC and TBW. The two groups did not differ significantly in %BF predictions by any of the methods. However, the difference in %BF between the groups was halved with the four-component model (B = 21.9%; W = 23.6%) as compared with that calculated from the Siri two-component densitometric model (B = 21.2%; W = 24.2%). Within each racial group, %BF was not significantly different when predicted by two-component or multicomponent models. However, %BF of individuals with the highest and lowest BMD was substantially under- and overpredicted, respectively, by Siri's equation.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of varied air velocity on sweating and evaporative rates during exercise.

This study was designed to determine the extent to which changes in the evaporative power of the environment (Emax) affect sweating and evaporative rates. Six male subjects undertook four 60-min bouts of cycle ergometer exercise at 56% maximal O2 uptake (VO2max).Emax was varied by differences in ambient temperature and airflow; two exercise bouts took place at 24 degrees C and two at 35 degrees C, with air velocity at < 0.2 and 3.0 m/s in both. Total sweat production was estimated from body weight loss, whereas whole body evaporative rate was measured continuously from a Potter beam balance. Body core temperature was measured continuously from a thermocouple in the esophagus (T(es)), with mean skin temperature (Tsk) computed each minute from thermocouples at eight sites. Total body sweat loss was significantly greater (P < 0.05) in the 0.2- than in the 3.0-m/s condition at both 24 and 35 degrees C. Tsk was higher (P < 0.05) in the still-air conditions at both temperatures, but final T(es) was significantly higher (P < 0.05) in still air only in the 35 degrees C environment. Thus the reduced Emax in still air caused a greater heat storage, thereby stimulating a greater total sweat loss. However, in part because of reduced skin wettedness, the slope of the sweat rate-to-T(es) relation at 35 degrees C in the 3.0-m/s condition was 118% that at 0.2 m/s (P < 0.005).(ABSTRACT TRUNCATED AT 250 WORDS)

Circulating hormone concentrations in hypothyroid rats with induced polycystic ovaries.

The induction of polycystic ovaries in hypothyroid rats by human chorionic gonadotropin (hCG) has been studied for many years. A complete understanding of this phenomenon requires information regarding the circulating levels of the hormones of the hypophyseal-gonadal axis. In this study, serum prolactin (PRL), luteinizing hormone (LH), estradiol, testosterone, and progesterone were measured by radioimmunoassay at intervals during the 40-day period in which large ovarian cysts were induced in hypothyroid rats by daily injections of hCG. After 20 injections, ovaries increased in weight 10-fold, and well-developed ovarian cysts were present, accompanied by lutein tissue; cyst development continued for the subsequent 20 days of hCG. Both PRL and LH rose during the first 5 days of treatment and were maintained at high levels from day 20 on. The pattern of change of gonadal steroids showed greater increases with hCG in hypothyroid than in euthyroid rats. Levels of estradiol in hypothyroid, hCG-injected rats increased in parallel to ovarian hypertrophy, whereas progesterone was high in initial stages and then declined. Testosterone increased in both euthyroid and hypothyroid animals, with no clear pattern coincident with cyst formation. The data suggest that the formation of polycystic ovaries in the hypothyroid rat is associated with high levels of PRL and LH followed by elevations of estradiol, which may serve to maintain continuous PRL, as well as LH, stimulation of the ovary.

Enhanced vagal baroreflex response during 24 h after acute exercise.

We evaluated carotid-cardiac baroreflex responses in eight normotensive men (25-41 yr) on two different test days, each separated by at least 1 wk. On one day, baroreflex response was tested before and at 3, 6, 12, 18, and 24 h after graded supine cycle exercise to volitional exhaustion. On another day, this 24-h protocol was repeated with no exercise (control). Beat-to-beat R-R intervals were measured during external application of graded pressures to the carotid sinuses from 40 to -65 mmHg; changes of R-R intervals were plotted against carotid pressure (systolic pressure minus neck chamber pressure). The maximum slope of the response relationship increased (P less than 0.05) from preexercise to 12 h (3.7 +/- 0.4 to 7.1 +/- 0.7 ms/mmHg) and remained significantly elevated through 24 h. The range of the R-R response was also increased from 217 +/- 24 to 274 +/- 32 ms (P less than 0.05). No significant differences were observed during the control 24-h period. An acute bout of graded exercise designed to elicit exhaustion increases the sensitivity and range of the carotid-cardiac baroreflex response for 24 h and enhances its capacity to buffer against hypotension by increasing heart rate. These results may represent an underlying mechanism that contributes to blood pressure stability after intense exercise.

Impairment of carotid-cardiac vagal baroreflex in wheelchair-dependent quadriplegics.

The incidence of orthostatic hypotension can increase after prolonged exposure to chair rest and bedrest and is associated with post-bed rest impairment of the carotid-cardiac baroreflex response. We therefore hypothesized that the hypotension observed in humans confined to wheelchairs may be manifested by a reduced baroreflex sensitivity. We compared baroreflex responses of 16 wheelchair-dependent (WCD) quadriplegics with those of 15 able-bodied subjects (ABS) matched for age, height, and weight. Beat-to-beat R-R intervals were measured during application of graded pressures from 40 to -65 mmHg using a neck chamber for noninvasive stimulation of the carotid baroreceptors. Changes of R-R intervals were plotted against carotid distending pressures. The maximum slope of the stimulus-response relationship was greater (P less than 0.0001) in ABS (6.1 +/- 0.6 ms/mmHg) than in WCD (2.6 +/- 0.4 ms/mmHg). The range of the R-R interval response, i.e., the capacity to buffer blood pressure changes, was only 138 +/- 19 ms in WCD compared with 253 +/- 19 ms in ABS (P less than 0.001). Mean sitting systolic-to-diastolic blood pressures in WCD (92/60 mmHg) were less (P less than 0.0001) than in ABS (120/77 mmHg), although there were no significant differences between groups in supine resting blood pressures. Chronic loss of stimulation to carotid baroreceptors by routine standing posture is associated with attenuated sensitivity and reduced buffer capacity of the arterial baroreflex and hypotension during sitting in WCD patients.

Ozone inhalation effects in females varying widely in lung size: comparison with males.

It has been suggested that lung size accounts for observed gender differences in responsiveness to the same total inhaled dose of O3. To test the hypothesis that lung size is a determinant of magnitude of response within a gender, two groups of 14 healthy young adult females differing significantly in forced vital capacity [FVC; i.e., small-lung group mean = 3.74 liters (range 3.2-4.0) and large-lung group mean = 5.11 liters (range 4.5-6.2] were exposed for 1 h to filtered air (FA) and to 0.18 and 0.30 ppm O3. On each occasion, subjects exercised continuously on a cycle ergometer at a work rate that elicited a mean minute ventilation of approximately 47 l/min. For the small-lung group [mean total lung capacity (TLC) = 4.52 liters] exercise O2 uptake was 67% of maximal O2 uptake (VO2max), and that for the large-lung group (TLC 6.37 liters) was 61% of VO2max. Statistical analysis revealed significant decrements for both groups in FVC, forced expiratory volume in 1 s (FEV1.0), and forced expiratory flow rate in the middle half of FVC on exposure to 0.18 and 0.30 ppm O3. Exercise respiratory frequency increased, and tidal volume decreased significantly in both groups in response to 0.18 and 0.30 ppm O3 exposure. On exposure to 0.30 ppm O3, the number of individual subjective symptoms reported and their severity were significantly greater for both groups than those reported for the FA and 0.18 ppm O3 exposures. Both groups evidenced similar percent changes in pulmonary function and exercise ventilation response, and in subjective symptom response.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of run-training and swim-training at similar absolute intensities on treadmill VO2max.

Thirty-seven sedentary males, aged 28-35 yr, were either run-trained, swim-trained, or served as controls in an 11 1/2-wk training study. Runners and swimmers exercised once a d, 3 d.wk, at a heart rate (HR) intensity equivalent to 75% of their treadmill VO2max. Treadmill maximal oxygen consumption (VO2max), submaximal cardiorespiratory response, and body composition parameters were measured before and following the training period. Runners, swimmers, and controls experienced a significant increase in treadmill VO2max over the 11 1/2-wk study period. The 28 and 25% increases observed for the runners and swimmers, respectively, were significantly greater than the 5% increase observed for the controls (P less than 0.0001). Runners and swimmers did not differ significantly from each other with respect to this increase in VO2max; nor did they demonstrate significant changes in respiratory exchange ratio (RER) at VO2max between tests. The run-trained and swim-trained groups both experienced a decrease in HR at a standard submaximal walking workload but did not differ significantly from each other. Controls showed no significant change in submaximal exercise response. A significant difference was observed among groups (P less than 0.01) for change in percent body fat. Changes in lean and fat weight over the training period were significant for both the runners (P less than 0.002) and swimmers (P less than 0.03) but not for the controls.(ABSTRACT TRUNCATED AT 250 WORDS)

Oral and oronasal breathing during continuous exercise produce similar responses to ozone inhalation.

Breathing route has a profound effect on sulfur dioxide-induced pulmonary function response in human subjects. There is comparatively little evidence of the effects of oral, nasal, and oronasal breathing on ozone (O3)-induced responses in humans. In this study, six young adult males were exposed on five occasions to 0.40 parts per million (ppm) O3 while exercising continuously at one of two workloads (minute ventilation, VE, of approximately 30 and 75 l/min). The VE exposure time product was similar for all protocols. Four exposures were delivered randomly with a Hans-Rudolph respiratory valve attached to a silicone facemask, with breathing route effected with and without noseclip. A 2 x 2 analysis of variance revealed no statistically significant differences (p less than .05) across conditions in pulmonary function, exercise ventilatory pattern, or subjective symptoms responses. The fifth exposure, delivered via the same respiratory valve with mouthpiece, but without facemask, revealed significantly greater forced expiratory volume in 1 s (FEV1.0) impairment than that observed for the respiratory valve, facemask with noseclip exposure (-20.4% and -15.9%, respectively). The latter suggests partial O3 reactivity to the facemask and clean shaven facial surface of the subjects, although reduced oral scrubbing by mouthpiece-induced bypassing of the oral vestibule might account, in part, for this difference. Recent O3 uptake evidence from another laboratory, however, supports our conclusion that breathing route during moderate and heavy continuous exercise does not affect acute physiologic responses to 0.40 ppm O3.

Duration of enhanced responsiveness upon re-exposure to ozone.

It has been repeatedly observed that ozone (O3) re-exposure within 24 h elicits enhanced pulmonary function responses. However, there are only limited observations concerning re-exposure to O3 at intervals between 24 h and several days. The present study was designed to assess the effects of re-exposure to 0.35 ppm O3 at intervals of 24, 48, 72, and 120 h. Forty young adult male subjects were assigned randomly to one of four groups in ascending order of time to re-exposure (groups 1-4). Each exercised on a bicycle ergometer for 60 min at a workload that elicited a mean ventilation of 60 l/min on three occasions: protocol 1 (P1), filtered air (FA); protocol 2 (P2), 0.35 ppm O3; and protocol 3 (P3), 0.35 ppm O3. In addition to standard pulmonary function measures, specific airway resistance (SRaw); exercise ventilatory pattern, i.e., respiratory frequency (fR) and tidal volume (VT); and subjective symptoms (SS) were assessed. Statistical analysis revealed significant differences (p less than .05) for all groups between the FA (P1) responses and those for the two O3 exposures (P2, P3) for forced vital capacity (FVC), forced expiratory volume in 1 s (FEV1.0), SRaw, fR, VT, and SS. When the two O3 exposures (P2 and P3) were compared, only group 1 (24 h) responses were statistically significant upon re-exposure: FEV1.0, -16.1 vs. -30.4% (p less than .003); SRaw, 20.5 vs. 34.5% (p less than .05); fR, 44.2 vs. 65.3% (p less than .001); and SS (p less than .015).(ABSTRACT TRUNCATED AT 250 WORDS)