SummaryTwo theories of how energy metabolism should be associated with longevity, both mediated via free-radical production, make completely contrary predictions. . We sought associations between longevity and individual variations in energy metabolism in a cohort of outbred mice. We found a positive association between metabolic intensity (kJ daily food assimilation expressed as g/body mass) and lifespan, but no relationships of lifespan to body mass, fat mass or lean body mass. Mice in the upper quartile of metabolic intensities had greater resting oxygen consumption by 17% and lived 36% longer than mice in the lowest intensity quartile. Mitochondria isolated from the skeletal muscle of mice in the upper quartile had higher proton conductance than mitochondria from mice from the lowest quartile. The higher conductance was caused by higher levels of endogenous activators of proton leak through the adenine nucleotide translocase and uncoupling protein-3. Individuals with high metabolism were therefore more uncoupled, had greater resting and total daily energy expenditures and survived longestsupporting the 'uncoupling to survive' hypothesis.

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HSP requires co-ordinated multidisciplinary management to minimize interference with rehabilitation and optimize outcome. Further research is needed to determine effective prophylaxis and document the therapeutic effect of different modalities in the various presentations. Development of an integrated care pathway provides a reasoned approach to management of this complex condition, thus providing a sound basis for prospective evaluation of different interventions in the future.

. Objectively measured physical activity in a representative sample of 3-to 4-year-old children. Obes Res. 2003;11:420-425. Objective: This study aimed to describe levels of physical activity in a representative sample of preschool children and to quantify tracking of activity over 1 year. Research Methods and Procedures: Physical activity (mean accelerometry counts/minute) was assessed over 3 days using the Computer Science and Applications accelerometer in 3-to 4-year-old children (n ϭ 104; 52 boys; mean age, 3.7 Ϯ 0.4 years). In 60 children (30 boys), measurements were repeated 1 year later. Results: Mean total activity at baseline was 777 Ϯ 207 counts/minute in boys and 657 Ϯ 172 counts/minute for girls; this gender difference was significant (p Ͻ 0.001). In the cross-sectional analysis, total activity was significantly positively related to age (r ϭ 0.37, p ϭ 0.007). In the sample followed up for 1 year, mean total activity was 849 Ϯ 252. The longitudinal analysis confirmed that total physical activity increased over the 1-year period (paired Student's t test, p Ͻ 0.001). The tracking rank order correlation coefficient of total activity count over 1 year was r ϭ 0.40 (p Ͻ 0.001). Discussion: This study suggests that total activity increases during the preschool period in Scottish children and that gender differences in total activity are present early in life.Tracking of total activity was only modest, but adequate assessment of tracking requires methodological research aimed at elucidating the biological meaning of accelerometer output.