The variability of fiber type distributions between different regions of the same human muscle is believed to be small, based on the sampling of between two and four sites. The objective of the present investigation was to determine the variability of slow-twitch (ST) and fast-twitch (FT) fiber distributions using a more extensive sampling technique than those previously employed. The soleus, biceps, triceps, and vastus lateralis muscles were excised from each of four young men who had died suddenly. Between 13 and 17 sites were sampled from each of the muscles; 3 transverse areas were then examined within each sample. Fiber type distributions were determined from photographs of sections stained for myofibrillar adenosine triphosphatase at pH 10.3, 10.0, or 4.3. The numbers of fibers counted in the four muscles ranged between a mean of 13,660 and a mean of 21,601. The variability in fiber type distributions observed between sites and areas within a site were statistically greater (P less than 0.01) than could be expected from muscles whose fiber type distributions are equally distributed throughout the muscle. It was concluded that sampling between 3 and 5 sites in the different muscles was necessary to reduce the between-site standard deviation to 5%.

More than 40 years ago, the effects of exertional dyspnoea and the associated fear of an asthma attack usually lead to an avoidance of physical activity amongst asthmatic children. This issue still exists today, particularly in children with severe asthma. This article presents a comprehensive review of published information concerning the effects of training programmes on children and adolescents with asthma. The primary focus of these investigations was to examine the effects of physical conditioning on aerobic fitness, the severity and incidence of exercise-induced asthma (EIA) and asthma symptoms. The large majority of training studies of asthmatic children and adolescents demonstrate significant increases in aerobic fitness post-training or the achievement of normal levels of aerobic fitness. While there are a few reports of a reduced severity in EIA symptoms post-training, the majority of studies demonstrate no change in the occurrence or degree of EIA. However, a number of these studies have reported some reductions in hospitalisations, wheeze frequency, school absenteeism, doctor consultations and medication usage. It is, therefore, recommended that children and adolescents with asthma should participate in regular physical activity. This may improve asthma management and associated general health benefits, whilst minimising inactivity-related health risks.

Asthma remains the most common chronic disease in childhood, reportedly affecting up to 25% of children in Western urban environmental settings. There seems to be a common perception that asthmatic children have a reduced capacity for exercise. Surprisingly, there is conflicting evidence in the literature in relation to this position. In this review, we present an overview of the literature in which habitual physical activity and fitness levels, including aerobic fitness, of asthmatic and non-asthmatic children are compared. There is contradictory evidence regarding the aerobic fitness levels of asthmatic children and adolescents, and it remains unclear whether significant differences exist between asthmatic children and their non-asthmatic counterparts. There is limited information concerning the relative anaerobic fitness of asthmatic children and adolescents; however, this is also conflicting. During childhood and adolescence, asthmatic individuals seem to have physical activity levels comparable with those of the normal paediatric population. However, differences in physical activity levels may develop during the time of maturation from adolescence into adulthood. Accordingly, it is not possible to establish a definitive conclusion about the issue in either children or adults. Further research with well designed methodologies is needed in order to determine whether asthmatic children and adolescents have different aerobic fitness, anaerobic fitness and physical activity levels when compared with the normal paediatric population.

C Ca ap ps sa ai ic ci in n c co ou ug gh h r re ec ce ep pt to or r s se en ns si it ti iv vi it ty y t te es st t i in n c ch hi il ld dr re en n A.B. Chang*, P.D. Phelan**, R.G.D. Roberts*, C.F. Robertson* Capsaicin cough receptor sensitivity test in children. A.B. Chang, P.D. Phelan, R.G.D. Roberts, C.F. Robertson. ERS Journals Ltd 1996. ABSTRACT: Capsaicin has been used as a tussive agent in studies in adults to determine cough receptor sensitivity. The aim of this study was to determine the tolerance, repeatability and influence of inspiratory flow on the capsaicin cough receptor sensitivity test in children.Thirty children (mean age 11 yrs; range 6-16 yrs) were tested on two different days, to determine the lowest concentration of capsaicin required to stimulate two or more coughs (cough threshold (Cth)), 2-4 coughs (C2), and five or more coughs (C5). Capsaicin was nebulized through a dosimeter, with an arrangement that allowed the subjects to visualize and regulate their inspiratory flow.Using a constant inspiratory flow of 20 L·min -1 , tests were reproducible for C2, C5 and Cth (doubling dose changes of 1.13, 1.03 and 1.08, respectively). An increase in the inspiratory flow from 20 to 60 L·min -1 significantly increased C2 (19.5 to 46.8 µM; p=0.016) and C5 (46.8 to 128.8 µM; p=0.008).We conclude that in children, the capsaicin cough challenge test: 1) is well-tolerated; 2) is highly repeatable; and that 3) the inspiratory flow significantly influences cough receptor sensitivity and repeatability of the test and should, thus, be regulated.