Automatic Estimation of Optimal Deployment of Transcatheter Aortic Valve Implantation Using Computed Tomography

BACKGROUND

A comparison was made between the accuracy of and time saved by using novel automated software for pre-procedural computed tomography (CT) planning before transcatheter aortic valve implantation (TAVI) and manual methods. Preprocedural CT to assess aortic annulus dimensions and predict the optimal C-arm implant angle before TAVI can reduce complications related to incorrect prosthesis sizing and positioning.

METHODS

A total of 61 consecutive patients underwent TAVI using either the SAPIEN XT or CoreValve prosthesis. Pre-procedural CT scans were analysed using three methods: automatic; semi-automatic; and manual. For each method, annular dimensions were measured and the optimal implantation angle was predicted. After TAVI the actual post-deployment angle orthogonal to the prosthesis was determined using aortic fluoroscopy. The difference between the predicted angle by CT and the measured post-deployment angle was calculated for each method.

RESULTS

For all methods the mean angular difference with the actual post-deployment angle was similar at ~9 ± 7°. There was a significant difference between the SAPIEN XT (6.6 ± 5.8°) and CoreValve (11.5 ± 6.9°, p <0.001) prostheses due to a consistently greater left anterior oblique and caudal angulation for the CoreValve. Although the annular area correlated well among all methods, 'automatic' results were consistently larger than 'manual' results. Interobserver variability was low for all measures. The fully automatic method saved 98 s, and the semiautomatic method 40 s per case.

CONCLUSIONS

The use of automatic software enabled a rapid and accurate prediction of implantation angles, though results differed for specific manufacturers. Annular areas were overestimated by the automatic method, and thus required manual adjustments.

Reliability and validity of the lactate-minimum test. A revisit

AIM

The Lactate-Minimum Test (LMT) is a high-resolution, physiologically elegant test for estimating the anaerobic threshold (AnT), or the Maximal Lactate Steady-State (MLSS). Nevertheless, it has not gained the acceptance level of typical progressive lactate-response tests (PLRT). Aim of this study was to compare LMT's validity and reviewer reliability vs. a PLRT-type test and re-evaluate the justification for LMT's dismissal.

METHODS

Sixteen male distance trained runners (37.1±11.6 yrs) were included in the study. MLSS, LMT, and PLRT tests were performed in separate sessions. Two reviewers, blind to the subjects' identity, independently determined LMT and PLRT's threshold velocities (VLMT, VPLRT) twice. Additionally, VLMT was determined objectively, using best-fit polynomial regressions (VLMTP).

RESULTS

VPLRT, VLMT and VLMTP correlated well with VMLSS (r=0.92, 0.90, 0.93, resp.). VPLRT was identical to VMLSS (13.54 km·h-1), but VLMT and VLMTP were 0.33 and 0.46 km·h-1 lower, respectively. Inter-reviewer reliability was higher for VLMT than VPLRT (ICC=0.96 vs. 0.57, resp.). Intra-reviewer reliability showed a similar pattern.

CONCLUSION

LMT's underestimation of MLSS appears corrigible. The validity of corrected LMT appears comparable to that of PLRT, while its reliability, objectivity and resolution are superior. Although neither test is a perfect MLSS-substitute, the corrected LMT is not inferior to PLRT-type testing and cannot be dismissed.

Blood lactate disappearance dynamics in boys and men following exercise of similar and dissimilar peak-lactate concentrations

Characteristically, children recover faster than adults from various types of exercise. The purpose of the present study was to explain the children's faster recovery, in part, by addressing lactate (La) removal and comparing La disappearance dynamics in the two age groups following exercise of both similar and dissimilar peak blood-lactate concentration values ([La]pk). The subjects were 14 prepubertal boys and 12 men of similar peak oxygen consumption, normalized for body mass. All subjects performed 30 s supra-maximal cycling (Wingate anaerobic test [WAnT]). [La]pk was 10.7 +/- 1.9 and 14.7 +/- 1.7 mmol x l(-1) for the boys and men, respectively (p < 0.001). The men were later retested in shortened versions of the WAnT so as to attain [La]pk values (10.5 +/- 0.7 mmol x l(-1)) comparable to those achieved by the boys. [La]pk lag time following the boys' standard WAnT was similar to that found in the men following the shortened WAnT (5.0 +/- 2.6 vs 5.7 +/- 1.3 min, respectively), but considerably shorter than that following the men's 30s-WAnT (7.6 +/- 2.1 min; p < 0.05). The La disappearance dynamics were closely matched between groups following the matched [La]pk WAnTs. [La] half-life was similar under all conditions (ca. 20 min). It is concluded that prepubertal boys are characterized by a lower [La]pk and a shorter time lag before reaching it, following 30-s supra-maximal cycling exercise. However, boys' La disappearance dynamics are not different from that of men.

Intensity effect of active recovery from glycolytic exercise on decreasing blood lactate concentration in prepubertal children

PURPOSE

Children's performance after intense exercise is known to recover faster than that of adults. However, very little is known about the physiological processes that differentiate children from adults in their recovery. The purpose of this study was to compare, in children, the decrease in blood lactate concentration ([La]) during various intensities of active recovery from highly intense exercise with that during passive recovery.

METHODS

Subjects were 15 healthy, physically active, prepubertal, 9- to 11-yr-old boys (N = 8) and girls (N = 7). Subjects performed three 40-s cycling bouts at 150% peak oxygen consumption (VO2peak), with two 50-s rest intervals, followed by 2 min of passive recovery and 23 min of one of four randomly-assigned recovery levels: passive and 40%, 50%, and 60% VO2peak (RP, R40, R50, and R60, respectively).

RESULTS

Mean values of peak [La] (by treatment) ranged between 9.9 +/- 1.5 and 10.8 +/- 2.0. Whereas HR and VO2 remained relatively higher, [La] decreased faster during all active recoveries compared with the passive mode. [La] during R60 was higher compared with [La] during R40. [La] was slightly higher in the first 10 min of R40 compared with R50, whereas from the 15th min onward, this difference was reversed. A similar pattern was seen in the boys and girls, separately. The calculated half-life of [La] was significantly higher during the passive compared with all three active recoveries, with no differences among the latter (22.0 +/- 5.0, 10.3 +/- 1.9, 10.5 +/- 2.2, and 11.5 +/- 2.1 min during RP, R40, R50, and R60, respectively).

CONCLUSIONS

In summary, similar to the case in adults, the decrease in [La] after intense exercise in children is faster during active recovery compared with the passive mode. Further research is required to determine whether performance recovery parallels that of [La] in children and adults of both genders.

Reliability of peak-lactate, heart rate, and plasma volume following the Wingate test

PURPOSE

The 30-s Wingate Anaerobic Test (WAnT) has been used to assess anaerobic performance capacity and to evaluate physiological responses to supramaximal exercise. Blood lactate concentration ([La]) following supramaximal exercise is often used in the field and in the laboratory to assess the glycolytic contribution to exercise. Although the reliability of the performance in the WAnT has been established, this has not been the case with the WAnT's [La] response. Thus, the main purpose of this research was to study the test-retest reliability of peak [La] following the WAnT. Additionally, the test-retest reliability of the heart rate (HR) and plasma volume changes (deltaPV) response was also evaluated.

METHODS

Twenty-nine subjects (15 male, 14 female) of diverse training levels as well as physical characteristics (mean +/- SD: 23.3+/-7.0 yr, 62.5+/-12.0 kg, 170.8+/-9.7 cm, and 16.3+/-6.2% fat) performed two WAnTs within 1 wk. Capillary blood was sampled from a prewarmed fingertip at rest, just before the WAnT and at 3, 5, 7, and 9 min following it. HR was also measured during these times.

RESULTS

Mean-power (MP) (+/-SE) in test 1 and test 2 was 8.4+/-0.2 and 8.3+/-0.2 W X kg(-1) body mass, respectively. Peak [La] was attained 5-7 min following the WAnTs and was not significantly different between test 1 and test 2 (9.7+/-0.3 vs 9.8+/-0.3 mM, respectively). Peak HR occurred within 5 s post-WAnT and was not different between tests (170.8+/-2.2 and 171.3+/-2.2 beats X min(-1), in test 1 and test 2, respectively). Peak deltaPV was not different between tests (-12.0+/-3.4 and -11.1+/-3.2%, in test 1 and test 2, respectively). The intraclass reliability coefficients for peak [La]. peak HR and deltaPV were 0.926, 0.941, and 0.878, respectively, whereas the corresponding value for MP was 0.982.

CONCLUSIONS

We conclude that peak [La], peak HR, and deltaPV following the WAnT are reliable measures.

Birth weight and physical ability in 5- to 8-yr-old healthy children born prematurely

Recent advances in perinatal care have resulted in increased survival rates of extremely small and immature newborns. This has resulted in some neurodevelopmental impairment. The purpose of this study was to quantitatively evaluate and compare neuromuscular performance in children born prematurely at various levels of subnormal birth weight (BW). Subjects were 5- to 8-yr-old children born prematurely at different levels of subnormal BW (535-1760 g, N = 22, PM), and age-matched controls born at full term (> 2500 g, N = 15, CON). None of the subjects had any clinically defined neuromuscular disabilities. Body mass (BM) of PM was lower than that of CON (18.3 +/- 2.7 vs 21.7 +/- 3.8 kg) with no difference in height or sum of 4 skinfolds. Peak mechanical power output determined with a 15-s modified Wingate Anaerobic Test and corrected for BM was lower (P = 0.07) in PM than in CON (5.11 +/- 1.07 vs 5.94 +/- 1.00 W.kg-1). This was especially noticeable in children born at extremely low BW (ELBW, < 1000 g, 4.49 +/- 1.04 W.kg-1, P < 0.01). Peak power, determined in a force-plate vertical jump, corrected for BM was lower in PM vs CON (25.5 +/- 5.4 vs 30.8 +/- 5.2 W.kg-1, respectively P = 0.01), especially in the ELBW group (20.0 +/- 5.5 W.kg-1). Similarly, the elapsed time between peak velocity and actual jump take-off was longer in PM than in CON (41.2 +/- 9.4 vs 35.8 +/- 5.8 ms, respectively, P = 0.04). No differences were observed in peak force. The results suggest that performance deficiencies of prematurely-born children may be a result of inferior inter-muscular coordination. The precise neuromotor factors responsible for this should be identified by future research.

A treadmill test of sprint running

Anaerobic power is characterized by a high degree of specificity regarding both the recruited muscles as well as the recruitment pattern. The popular Wingate Anaerobic Test (WAnT) is a cycling test that does not satisfy the need for a running-specific anaerobic test. We describe such a test, using a novel type of a commercially available treadmill (BRL 1800, Gymrol, France). The ergometer is equipped with a torque motor to neutralize the frictional resistance of the treadmill belt, and a hip-belt harness connected to a horizontal rod. Force applied to the harness is monitored by a strain gauge mounted on the rod, while vertical movement is monitored by a potentiometer at the posterior fixed end of the rod. These, in conjunction with the treadmill belt speed, enable the computation of horizontal and vertical power as well as the combined total output. Power is calculated both as 'peak' power (highest 2.5 s segment) and 'mean' power (20 s duration). Preliminary results of young athletes were generally consistent with the expected age-related changes in anaerobic power. Values obtained on the anaerobic treadmill were always higher than the corresponding WAnT values previously obtained in comparable age groups. The higher values were probably due to the larger muscle mass involved and the shorter peak and mean power durations (2.5 and 20 s versus 5 and 30 s in the WAnT, respectively). This test should enable not only running-specific anaerobic power monitoring but also the characterization of the relationship between the horizontal and vertical components of that power.

Smoking effect on exercise response kinetics of oxygen uptake and related variables

The effects of smoking on the kinetics of oxygen uptake (VO2), carbon dioxide production (VCO2), ventilation (Ve) and heart rate (HR) in the transition from rest to steady-state submaximal exercise was investigated in 6 female and 4 male smokers (32 +/- 8 yrs). The subjects underwent two counter-balanced treadmill tests at 60% of their maximal VO2, lasting 10 min each: one following a 24-hr smoking abstinence, and one immediately after smoking three cigarettes without prior abstinence. Physiological variables were measured at rest and every 30 sec throughout each test. The time required for a given variable to rise from its respective resting baseline to half of its steady-state value (t1/2) was calculated for VO2, VCO2, Ve and HR. Smoking abstinence was associated with t1/2 values of 32 +/- 8, 42 +/- 12, 43 +/- 10, and 30 +/- 9 sec for VO2, VCO2, Ve, and HR, respectively. Smoking significantly (p less than 0.01) lengthened those values to 51 +/- 12, 58 +/- 11, 54 +/- 8, and 41 +/- 10 sec. Concurrently, smoking raised the baseline (resting) values of HR (p less than 0.01) and of Ve, VCO2, O2 pulse (O2P), and both systolic and diastolic blood pressures (p less than 0.05). During steady-state exercise only HR values were elevated by smoking (p less than 0.01), while O2P values were lowered (p less than 0.05). These findings indicate that smoking considerably retards physiological responses to submaximal exercise.

Effect of training load on OBLA determination

Fifteen male long-distance runners, 35.9 +/- 8.2 years of age, participated in the study. They had 5.7 +/- 2.3 years of running experience, marathon best time of 2,58:51 +/- 0,14:45 h, 10-km personal record of 37:18 +/- 2:50 min, and maximal aerobic power of 64.6 +/- 5.8 ml.kg-1.min-1. Their 4 mM.l-1 lactate threshold (OBLA) was tested twice in a randomized order: once following a week of light, pre-race-like training, and once after a week of heavy training load. The parameters measured during the OBLA tests were: rating of perceived exertion (RPE), running economy (E), heart rate (HR), respiratory exchange ratio (R), and running velocity at OBLA. Compared with the light load treatment, RPE following the heavy training week rose by 0.8 units, HR and E remained unchanged, and R decreased slightly (0.012). Running velocity at OBLA was raised 0.42 km.h-1 by the heavy training, but a negative correlation was found between this change and the baseline (light load) OBLA velocity (r = -0.57). It is suggested that in athletes the usefulness of OBLA testing, aimed at assessing current performance capacity, could be compromised by lack of control over the immediately preceding training schedules. However, it appears that the susceptibility to the lack of such standardization may be reduced or absent in higher level runners.

Effect of training on anaerobic threshold, maximal aerobic power and anaerobic performance of preadolescent boys

To evaluate the effect of a 9-week interval training program on aerobic capacity, anaerobic capacity, and indices of anaerobic threshold of preadolescent boys, 28 10.2- to 11.6-year-old boys were tested. The test included laboratory evaluation of anaerobic capacity (Wingate anaerobic test) and evaluation of VO2 max and anaerobic threshold indices from a graded exercise test and measurement of blood lactate. The tests also included a 1200-m run to investigate the relationship of laboratory fitness indices, VO2 max, anaerobic threshold indices, and indices of anaerobic capacity to the performance of the run. It was found that in 10- to 11-year-old boys, a 9-week interval training increased the indices of anaerobic capacity: mean power by 10% and peak power by 14%. No change was found in percent fatigue. The training also increased VO2 max by 7% in absolute terms and by 8%/kg body weight. A significant increase was also found in the running velocity at the anaerobic threshold (running velocity at inflection point of lactate accumulation curve), but in relative terms (percent of VO2 max), the anaerobic threshold decreased by approximately 4.4%. It is concluded that proper training may improve maximal aerobic power and anaerobic capacity of preadolescent boys. It is also concluded that anaerobic threshold measures are less sensitive to the training regimen than VO2 max and that the 1200-m running performance is strongly associated with both aerobic and anaerobic capacities and less with the anaerobic threshold, which in preadolescent boys seems to be higher than in adults.

Exaggerated systolic blood pressure response to exercise in a water polo team

Twenty-three top-level water polo players (WP) were examined for blood pressure (BP) response to graded and continuous cycle ergometry. Testing also included resting muscle biopsy for fiber typing, exercise ECG recording for heart rate (HR), exercise concentrations of blood lactate (LA), measured VO2max, and ratings of perceived exertion (RPE). A control group (C), whose subjects were physically active in endurance sports, but were older and less fit than the experimental subjects, was tested by an identical protocol. The BP response to exercise was significantly higher in the WP group at all comparison criteria including onset of blood lactate accumulation, absolute HR, percent of HRmax, and power loads (including loadless pedaling). To date, we are unaware of other reports on whole groups of sportsmen showing an exaggerated BP response to exercise. While it would appear from previous studies that normotensive individuals showing such a response are at a greater risk of developing hypertension, the significance of this BP response in highly-trained athletes in a specific sport remains unclear.

Load optimization for the Wingate Anaerobic Test

The purpose of the present study was to define the optimal loads (OL) for eliciting maximal power-outputs (PO) in the leg and arm modes of the 30s Wingate Anaerobic Test (WAnT). Eighteen female and seventeen male physical education students, respectively 20.6 +/- 1.6 and 24.1 +/- 2.5 years old, volunteered to participate. In each of the total five sessions, the test was administered twice on a convertible, mechanically braked cycle-ergometer, once for the legs and once for the arms. The five randomized, evenly-spaced resistance loads ranged from 2.43 to 5.39 Joule per pedal revolution per kg body weight (B. W.) for the legs, and from 1.96 to 3.92 for the arms. The measured variables were mean (MP x kg-1) and peak PO as well as absolute and relative measures of fatigue. A parabola-fitting technique was employed to define the optimal loads from the MP x kg-1 data. The resulting OL were 5.04 and 5.13 Joule x Rev-1 x kg B.W.-1 in the leg and 2.82 and 3.52 in the arm tests for the women and men, respectively. OL were shown to depend on PO magnitude. However, within a two-load span (0.98 Joule x Rev-1 x kg B.W.-1) about the OL, MP x kg-1 did not vary by more than 1.4% in the leg and 2.2% in the arm tests. It is suggested that although the WAnT is rather insensitive to moderate variation in load assignment, improved results could be obtained by using the stated OL as guidelines that may be modified according to individual body build, composition, and, particularly, anaerobic fitness level.

Lactate in human skeletal muscle after 10 and 30 s of supramaximal exercise

The purpose of this study was to evaluate the extent of anaerobic glycogenolysis, as indicated by intramuscular lactate concentration, after 10 and 30 s of supramaximal exercise and to compare male and female subjects in this regard. Fifteen males and seven females performed two cycle exercise bouts against a resistance which was standardized so that one pedal revolution resulted in 4.90 J work X kg body wt-1. A muscle biopsy was obtained after 10- and 30-s exercise bouts and analyzed for lactate concentration. The lactate concentrations averaged 36 and 61 mmol X kg dry wt-1 after the 10- and 30-s exercise bouts, respectively. The male subjects had higher (P less than 0.005) lactate concentrations and generated higher (P less than 0.001) power outputs for both exercise bouts. When the mean lactate concentrations were statistically adjusted after controlling for between-group variation in power output, no difference was evident between groups for the 10- or the 30-s lactate value. The results are evidence that pronounced lactate accumulation occurs during supramaximal exercise of a 10-s duration, suggesting that glycolysis can occur within this time frame. This is in contrast to the theory that glycolysis does not occur until endogenous phosphagen levels reach some critically low value, not thought to be obtainable within the first 10 s of supramaximal exercise.

Changes in muscle metabolites in females with 30-s exhaustive exercise

The purpose of this study was to quantify the changes in selected intramuscular metabolites associated with non-oxidative energy metabolism after performance of the Wingate Test (WT), a widely used, exhaustive, 30-s cycle test of short-time muscular power. Muscle biopsies were taken from the m. vastus lateralis of nine female physical education students at rest and immediately after performance of the WT. The concentrations of adenosine triphosphate (ATP), creatine phosphate (CP), lactate, and glycogen were determined. The ATP decreased from 20.9 to 13.8; CP decreased from 62.7 to 25.1; lactate increased from 9.0 to 60.5; and glycogen decreased from 360 to 278 (all concentrations are mmol X kg-1 dry muscle). The absolute changes in CP and lactate were not as large as those reported in other exercise studies. Based on the metabolite changes, it was concluded that the WT is a satisfactory test of the maximal muscular power that can be generated from non-oxidative metabolism, but that the 30-s duration of the test probably does not tax the maximal capacity of such energy metabolism.

Conditioning versus exercise in heat as methods for acclimatizing 8- to 10-yr-old boys to dry heat

Two heat-acclimatization protocols were studied in 8- to 10-yr-old boys: exercise in dry heat (WH, n = 9) and exercise in neutral climate (W, n = 9). Five 90-min acclimatization sessions were conducted within a 12-day period. Base-line (BL) and criterion (CT) tests sessions were held at 43 degrees C db and 24 degrees C wb, with three 20-min exercise bouts at approximately 40 Ws. With acclimatization, the WH group showed a significant reduction in heart rate (HR) (11.4 beat x min-1), mean skin temperature (0.64 degrees C), and an increase in the population density of heat-activated sweat glands (HASG) (25.2 glands x cm-2). The W group showed a significant reduction in HR (13.4 beat x min-1) and rectal temperature (0.24 C). Total sweat rate per body surface area did not increase significantly in either group. However, the sweat rate relative to rise in core temperature increased in both groups. No significant differences were found between the two acclimatization procedures in any of the variables studies except for the HASG, which showed a greater increase in the WH group. It is suggested that in 8- to 10-yr-old boys physiological changes compatible with heat acclimatization could be achieved either by exercise in heat or by mere physical conditioning (approximately 65% of VO2max), in neutral climate. It is postulated that age-related factors associated with the thermoregulatory system prevent children from deriving full effectiveness of exercise-in-heat acclimatization protocol as used in this study.

Climatic heat stress and performance in the Wingate Anaerobic Test

To determine climatic effects on performance of the Wingate Anaerobic Test, 28 children (10.2-12.2 years old) were each tested in three different climates: Neutral (22-23 degrees C, 55-60% R.H.), hot-dry (38-39 degrees C, 25-30% R.H.), and warm-humid (30 degrees C, 85-90% R.H.). The test is an all-out 30 s cycle-ergometer-pedalling in which mean as well as peak power outputs are determined. The children stayed in the climatic chamber for 45 min prior to the test. Mean power, relative to body weight, was higher in the boys after the warm-humid exposure compared with the hot-dry one (P < 0.05). No other differences were found. Inter-climate correlations of weight-relative power outputs were 0.83-0.92 and 0.82-0.86 for mean power in the girl and boy groups, respectively, and 0.33-0.72 and 0.49-0.75 for peak power, in the same order. The corresponding values for absolute power outputs were always higher. Reasons why the single detected inter-climate difference is likely to have been a happenstance are discussed, and it is suggested that comparable environmental exposures do not appreciably affect performance of the Wingate Anaerobic Test by children and young adolescents. The practicality and reliability of this test is, therefore, well maintained in "field situations" where climate cannot be strictly controlled.

Breathing dry or humid air and exercise-induced asthma during swimming

Recent studies have shown the relevance of air humidity to the provocation of bronchoconstriction by running. The present study was undertaken to ascertain whether the humid air breathed during swimming could explain the protective effect of swimming on the asthmatic. Nine asthmatic children 9--15 years old swam while inspiring dry (15--35% R.H.) or humid (80--90% R.H.) air administered in a random order, a week separating the two sessions. The exercise challenge was an 8-min tethered swim at a metabolic rate (VO2) of 29 ml.kg-1.min-1, minute ventilation (VE) of 34 L.min-1, and a heart rate (HR) of 161 beats.min-1. Ambient air and water temperature were 28 +/- 2 degrees C and 27 +/- 2 degrees C, respectively. Pulmonary functions were tested pre and post swimming. Exercise VE, VO2 and HR were similar under the two conditions. No reduction in any of the pulmonary functions (FVC,FEV1.0,MMEFR,MBC) was found after 5 and 10 minutes following the swimming exercise in either of the conditions. In contrast, a treadmill run of similar metabolic and ventilatory intensity induced bronchoconstriction when room air was dried to 25--30% R.H. It is suggested that, unlike running, swimming is of low asthmogenicity even when inspired air is dried to 25--30% at neutral temperatures.

Voluntary hypohydration in 10- to 12-year-old boys

This study was performed to determine whether a) children voluntarily dehydrate while exercising in hot climate; b) such dehydration affects their well-being and thermoregulation. Eleven 10p to 12-yr old, partially acclimatized boys underwent two work-in-the-heat protocols (cycle rides, 45% aerobic capacity at 39 degrees C, 45% rh). During one session they drank only voluntarily when thirsty (VD). In the other, drinking was forced (FD) to replenish fluid losses. VD induced a progressively increasing fluid loss (0.3% of body wt.h-1) due to insufficient drinking (72% of intake in FD). URinary output was lower (55.7 vs. 81.6 ml.h-1) and its osmolality higher (880 vs. 523 meq.1-1) than during FD. Sweat rate, rectal (Tre) and mean skin (T-sk) temperatures, heart rate, rate of perceived exertion, sweat gland counts, blood hemoglobin, hematocrit (Hct), serum electrolytes, and total proteins did not differ between sessions. However, the rise of Tre, Hct, and proteins positively correlated with hypohydration level. It is concluded that exercising children progressively dehydrate when not forced to drink. At equal levels of % weight loss they have greater Tre rise than do lean adults.

Effects of dry and humid climates on exercise-induced asthma in children and preadolescents

Among factors which possibly influence the responses of asthmatic children to exercise, climate has received little attention. This study was performed to determine whether the level of air humidity is a factor to be considered. Twenty asthmatic (extrinsic perennial) girls and boys, 6 to 14 yr of age, with unverified history of exercise-induced asthma (EIA) took part. They rested and exercised in a climatic chamber in dry (25% relative humidity) and humid (90%) sessions at 25 degrees to 26 degrees C. One to three weeks separated the sessions, the order of which was counterbalanced. No changes in pulmonary functions (FVC, FEV 1.0, MMEF, MBC) were found following a sitting period of 60 min in either climate. Five and ten minutes following the treadmill run, however, bronchoconstriction was distinctly more pronounced in the dry than in the humid climate. Exercise heart rate and the subjective rating of effort were not affected by climate. It was concluded that, under the above experimental conditions, EIA is more likely in dry air than in humid air, possibly due to heat loss at the airway mucosa caused by evaporation. High humidity of inspired air could be the reason why EIA is less prevalent in swimming, as compared with other modes of exercise.