A B S T R AC TAll too often young people are excluded in practice from the general policy and professional consensus that partnership and participation should underpin work with children, young people and their families. If working with troubled and troublesome young people is to be based on family support, it will require not only the clear statement of that policy but also demonstration that it can be applied in practice. Achieving that involves setting out a plausible theory of change that can be rigorously evaluated. This paper suggests a conceptual model that draws on social support theory to harness the ideas of social capital and resilience in a way that can link formal family support interventions to adolescent coping. Research with young people attending three community-based projects for marginalized youth is used to illustrate how validated tools can be used to measure and document the detail of support, resilience, social capital and coping in young people's lives. It is also suggested that there is sufficient fit between the findings emerging from the study and the model to justify the model being more rigorously tested.

We measured the metabolic cost (C) and mechanical work of riding historic bicycles at di¡erent speeds: these bicycles included the Hobby Horse (1820s), the Boneshaker (1860s), the High Wheeler (1870s), the Rover (1880s), the Safety (1890s) and a modern bicycle (1980s) as a mean of comparison. The rolling resistance and air resistance of each vehicle were assessed. The mechanical internal work (W INT ) was measured from three-dimensional motion analysis of the Hobby Horse and modern bicycle moving on a treadmill at di¡erent speeds. The equation obtained from the modern bicycle data was applied to the other vehicles. We found the following results. (i) Apart from the Rover, which was introduced for safety reasons, every newly invented bicycle improved metabolic economy. (ii) The rolling resistance decreased with subsequent designs while the frontal area and, hence, aerodynamic drag was fairly constant (except for the High Wheeler). (iii) The saddle-assisted body weight relief (which was inaugurated by the Hobby Horse) was responsible for most of the reduction in metabolic cost compared with walking or running. Further reductions in C were due to decreases in stride/pedalling frequency and, hence, W INT at the same speeds. (iv) The introduction of gear ratios allowed the use of pedalling frequencies that optimize the power/contraction velocity properties of the propulsive muscles. As a consequence, net mechanical e¤-ciency (the ratio between the total mechanical work and C) was almost constant (0.273 AE 0.015 s.d.) for all bicycle designs, despite the increase in cruising speed. In the period from 1820 to 1890, improved design of bicycles increased the metabolically equivalent speed by threefold compared with walking at an average pace of ca. + 0.5 m s 71. The speed gain was the result of concurrent technological advancements in wheeled, human-powered vehicles and of`smart' adaptation of the same actuator (the muscle) to di¡erent operational conditions.

Standardized radiological pelvimetry was used to examine 242 male and 314 female adults attending the out-patient departments of the Royal Victoria Hospital, Belfast, Seven indices of pelvic size and shape were measured from X-rays on each individual together with social and biological factors including age, height and year of birth. The aims were to quantify any differences in pelvic anatomy between the sexes and to measure correlations between these pelvic indices and selected biosocial factors. Pelvic indices for men and women of similar stature were significantly different, with the exception of the brim index, and these anatomical changes were correlated with year of birth. The similarity of the findings in both sexes suggests common environmental factors such as nutrition are the most likely causes, rather than factors specifically associated with pregnancy and childbirth.

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A prospective randomized controlled trial designed to investigate selective planned delivery is reported: 264 obstetrically normal women in the 38th week of pregnancy were admitted to this trial and 184 completed it. The infants of mothers in the planned delivery group had higher serum bilirubin levels on the fifth day post partum than control infants but no baby required treatment for hyperbilirubinaemia. Mothers in the planned delivery group required significantly greater amounts ot' pethidine while control mothers had a significantly higher incidence of meconium staining of the amniotic fluid. However, the infants in the two groups had similar Apgar scores at birth. There was one stillbirth in the control group; this was due to unrecognized fetal hypoxia during labour induced at 42 weeks for postmaturity. I N selective planned delivery the initiation of labour is achieved by artificial means for other than medical reasons. We previously reported a pilot study (Pinkerton et al, 1975) carried out at the Royal Maternity Hospital, Belfast, which showed that, provided strict criteria were used, selective planned delivery appeared safe for both mother and fetus. We now describe further work based on a prospective randomized trial comparing spontaneous and selective planned delivery in a sample of 264 obstetrically normal patients.