The relationship between changing body height and growth related changes in maximal aerobic power.

In order to analyse the relationship between maximal aerobic power (VO2max) and height, body mass and lean body mass a multi-longitudinal survey was conducted on three different age groups of randomly selected children from a small Czech community. Beginning at the initial ages of 8, 12 and 16 years subjects were subsequently retested three times at 2-year intervals. At overlapping ages there were no differences in the various age groups between height and VO2max. By utilizing mean values for the various parameters at specific calendar ages a growth curve was constructed for each sex for the age range 8-20 years. The values were compared with longitudinal studies in various countries and no substantial differences were found. When VO2max was then compared to height, body mass and lean body mass it was apparent that the almost linear relationship with height was the most precise. In addition the children remained, generally speaking, in their same rank order for VO2max for the three different age groupings.

Working ability and exercise tolerance during treatment of a mild hypertension. I. Comparison between a beta-adreno-receptor blocking drug and a calcium antagonist.

A randomized cross-over trial was undertaken on 21 occupationally active persons who had a stable mild or moderate hypertension with the purpose of comparing the effect of a beta-adreno-receptor blocking agent (atenolol) with that of a calcium channel inhibitor (nifedipine). The doses recommended by the manufactures were used. Atenolol (100 mg) given once a day resulted in a marked hypotensive effect at rest as well as during exercise, the compliance was satisfactory, and the hemodynamic changes were not reflected in unfavourable side effects during muscular exercise or in the subjects own personal assessment of fatigue during the exercise tests which ranged in energy expenditure from about three to six times the resting level. However, unfavourable, modest side effects occurred in two subjects during atenolol medication to the extent that they wanted to terminate the study. Nifedipine therapy with doses of 10 mg, three times a day, resulted in a modest, but statistically insignificant reduction in arterial blood pressure, which contrasts with previous published results. It is suggested that the modest effect is caused or related to the poor compliance and a daily dose that was quantitatively too small. No unfavourable side effects were seen during muscular efforts when the subjects were on nifedipine medication.

Working ability and exercise tolerance during treatment of mild hypertension. II. A comparison between atenolol and prazosin medication.

The treatments of mild hypertension with atenolol and prazosin in occupationally active men and women were compared in a double blind cross-over with placebo. The hypotensive effect of the beta-adreno-receptor blocking drug, atenolol, were striking and in accordance with current knowledge, using one daily dose of 100 mg. In contrast, the hypotensive effect of taking 2 mg prazosin twice a day was modest, averaging about 3% when compared with placebo, somewhat less but still detectable during the performance of muscular exercises. Atenolol medication significantly reduced heart rate and blood pressure responses to muscular exercises, covering a range of work loads experienced during ordinary working days. No increased feeling of muscular fatigue or other discomfort during muscular work compared to that on prazosin and placebo medication could be detected. It was therefore concluded that atenolol medication was a useful treatment of mild hypertension and did not reduce the normal working ability and exercise tolerance. Prazosin medication did not significantly change working ability and exercise tolerance.

Maximal aerobic power affected by maturation and body growth during childhood and adolescence.

This paper examines the development of maximal aerobic power as a function of maturation by a longitudinal study with annual examinations of representative samples of 56 boys and 56 girls in Norway and Western Germany. The age at which occurred peak height velocity (PHV) (i.e. the age at which the greatest height velocity was observed) was used as a reference of biological age and maturation. Before the PHV the mean maximal aerobic power was the same in two cohorts of children both in absolute values as well as in values relative to total and lean body mass. At and after PHV the boys were similar in their absolute values, but the German girls decreased their exercise fitness and became inferior to the Norwegian girls during later adolescence. When related to age of PHV the maximal aerobic power increased during the prepubertal years, mainly as an effect of growth in body size with little or no additional effect of other factors and approached a ceiling level at the end of adolescence. The boys exhibited clearly superior exercise fitness during all years of childhood and adolescence, this being in contrast to the widely accepted concept that no sex difference exists in exercise fitness before puberty. The maximum level for VO2-max, reached at the end of adolescence, averaged 3.2 1/min with a coefficient of variation of about 12% for the boys, and 2.5 1/min for the Norwegian girls and a similar coefficient of variation. As these ceiling values of maximal oxygen uptake agree with published averages for normal young adults representative for the normal population in these two countries, it is suggested that they represent optimal values brought about mainly by normal growth in body size with no or little additional effects of other factors.