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Biomedical subjects

O Bar-Or

Publications and source records attributed to O Bar-Or.

At least 109 records · Page 6Linked to original sources
PubMed1980

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.

Age Factors↗
PubMed1978

Pulmonary functions and responses to exercise of patients following cranio cerebral injury.

To assess the causes of excessive fatigue among patients who have recovered from cranio-cerebral injury (CCI) nineteen patients and fourteen healthy controls underwent pulmonary function testing at rest and cardiopulmonary evaluation during two submaximal exercise work-loads. Total lung capacity, vital capacity and forced expired volume were reduced by 25--40% among the patients. Functional residual capacity was normal. No improvement was elicited by inhalation of Ventolin and bronchoconstriction could thus be excluded. The above pattern may result from either decreased compliance of the chest wall or from weak (or non-coordinated) respiratory musculature. Exercise heart rate, minute ventilation and ventilatory equivalent were higher, and O2 pulse lower, among the CCI patients compared with the controls. This indicates lower circulatory and ventilatory efficiency during exercise among the patients, possibly due to habitual hypoactivity and detraining.

Adult↗
PubMed1977

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.

Adolescent↗
PubMed1975

The effects of intermittent warm-up on 7-9 year-old boys.

Twelve boys, 7-9 years old, who, by use of questionnaires, were found to be ignorant of the concept of "warm-up", performed maximal aerobic and anaerobic tasks 4 min after completing a 15 min intermittent warm-up (WU) (30 sec treadmill run, 30 sec pause). The WU required some 60% of the individual's VO2max, and raised rectal temp. by 0.52 +/- 0.19 degrees C. The aerobic criterion task (CT) was a one-stage bicycle ride at a load predetermined to exhaust the subject after 4 min. The anaerobic CT was a 30 sec all-out ride against resistance of 35 gm/kg BW. Subjects also performed both CT's without any WU. VO2max (aerobic CT), HRmax, as well as total mechanical work output achieved during the aerobic CT, were significantly higher with WU, compared with the non-WU sessions. During the anaerobic CT total revolutions, total power output, as well as peak HR, were significantly higher following WU. It is suggested that the benefits of intermittent WU, as used in this study in young children, can be attributed to physiological rather than psychological mechanisms.

Adaptation, Physiological↗
PubMed1975

Maximal oxygen consumption test during arm exercise--reliability and validity.

The reliability and validity of a continuous progressive arm test, in which maximal 02 consumption (V02 max arm) is determined, were analyzed. Forty-one men (28.2 +/- 8.8 yr) performed the test twice. Eighteen additional men (22.6 +/- 5.6 yr) performed the arm test, as well as the treadmill run, in which maximal O2 consumption VO2max leg) was determined. The validity of the VO2 max arm test was computed, using VO2 max leg as a criterion for the individual's aerobic capacity. The reliability coefficients of VO2 max arm, VEmax arm, and HRmax arm were 0.94, 0.98, and 0.76, respectively, indicating a high reliability of the testmthe validity coefficient of VO2max arm was only 0.74. The regression equation of VO2max leg on VO2max arm was y = 24.4 + 0.9 +/- 4.4 (Syx). These findings indicate that, following the suggested protocol, the individual repeatedly uses the same muscles and does reach an all-out stage. However, different individuals apparently are aided by their trunk and leg muscles to different degrees, which lowers the validity of this test as a predictor of aerobic capacity.

Adult↗
PubMed1975

Responses to exercise of paraplegics who differ in conditioning level.

The purpose of this study was to evaluate the cardiopulmonary function and body composition of sedentary and highly active paraplegics. Four age-matched groups of men (n = 41) were studied: wheelchair-bound sedentary (WS), wheelchair-bound athletes of international caliber (WA), able-bodied sedentary (NS), and able-bodied athletes of national Israeli teams (NA). Although of similar height, WS were significantly (p less than .05) heavier and more obese (skinfolds) than WA and NS. Maximal oxygen consumption (VO2max arm), as measured during arm ergometry by direct open circuit spirometry, was significantly lower in WS (19.58 plus or minus 5.53 ml/kg per min) than in WA (35.00 plus or minus 7.55). The latter had significantly higher VO2max arm than did NS (25.79 plus or minus 3.98). However, no significant difference was observed between WA and NA (38.05 plus or minus 6.25). A similar trend, favoring WA over WS, was shown for maximal minute ventilation and maximal oxygen pulse. Functional lung volumes (FVC, FEV1.0, MBC) did not differ significantly between WA and WS. Heart rates at submaximal work loads were higher in WA than in NA, but markedly lower than in WS. Clear-cut conclusions can be obtained only by a longitudinal study, but these data suggest a marked decrement in cardiopulmonary functions, related to the oxygen transport system, in men whose lower limbs have been immobilized for years. A reversed trend is shown for paraplegics who regularly activate their upper limbs and trunk muscles.

Adult↗