Questionnaires that are used to measure the effect of an intervention often consist of different sets of items, each set possibly measuring another concept. Mixed models with set-specific random effects are a flexible tool to model the different sets of items jointly. However, computational problems typically arise as the number of sets increases. This is especially true when the random-effects distribution cannot be integrated out analytically, as with mixed models for binary data. A pairwise modelling strategy, in which all possible bivariate mixed models are fitted and where inference follows from pseudolikelihood theory, has been proposed as a solution. This approach has been applied to assess the effect of physical activity on psychocognitive functioning, the latter measured by a battery of questionnaires. Copyright 2006 Royal Statistical Society.

The aim of this study was to examine the physical characteristics and somatotype of junior and senior athletes in relation to sprint start and acceleration performance. Nineteen female junior, 23 male junior, 9 female senior, and 16 male senior sprint athletes performed three maximal 20-m sprints. The starting blocks were instrumented to measure forward propulsion forces. Running velocity was measured by a laser positioned behind the athlete at 1 m height. Anthropometric measures were used to calculate somatotype and skeletal muscle mass. Body composition was estimated by underwater weighing densitometry. Junior and senior athletes were of similar height in both sexes. Male seniors were heavier, had larger limb circumferences, and a higher skeletal muscle mass than male juniors. Only the limb circumferences of the female seniors were larger than those of the female juniors. Female juniors were balanced ectomorphs, while female seniors were situated centrally on the somatochart (2.7Á2.2Á3.9 vs. 2.6Á3.1Á3.1; P 00.772, 0.047, and 0.066 respectively). Male juniors were mesomorphic ectomorphs, while male seniors were ectomorphic mesomorphs (1.8Á3.3Á3.6 vs. 1.6Á4.2Á2.8; P 00.148, 0.002, and 0.002 respectively). All sprint starts were similar for the junior and senior athletes of both sexes. Senior athletes accelerated more than the junior athletes, which resulted in higher running velocities after 5 m (senior vs. junior: females, 5.5190.32 vs. 6.0190.27 m × s Á1 , P 00.001; males, 5.8590.38 vs. 6.1390.44 m × s Á1 , P 00.043). The greater muscularity of senior compared with junior athletes did not result in better sprint start dynamics, but they did accelerate more and ran faster. These results show that late-adolescent boys in particular are still developing their muscularity. The technical complexity of the sprint start and the negative influence of a higher body mass may partly explain the comparable sprint start dynamics of the junior and senior athletes. We suggest that strength training should be combined with sufficient attention to technical skills to allow a positive transfer.

Background Maximum muscle power (P max ) is a biomarker of physical performance in all ages. No longitudinal studies have assessed the effects of aging on P max obtained from the torque-velocity (T-V) relationship, which should be considered the 'gold standard'. This study evaluated the longitudinal changes in the T-V relationship and P max of the knee-extensor muscles in young, middle-aged, and older adults after 10 years of follow-up. Methods Four hundred eighty-nine subjects (311 men and 178 women; aged 19-68 years) were tested at baseline and after a 10-year follow-up. Anthropometric data, daily protein intake, physical activity level (PAL), and knee-extension muscle function (isometric, isokinetic, and isotonic) were evaluated. A novel hybrid equation combining a linear and a hyperbolic (Hill-type) region was used to obtain the T-V relationship and P max of the participants, who were grouped by sex and age (young: 20-40 years; middle-aged: 40-60 years; and old: ≥60 years). Linear mixed-effect models were used to assess effects of time, sex, and age on T-V parameters, P max , and body mass index (BMI). Additional analyses were performed to adjust for changes in daily protein intake and PAL. Results P max decreased in young men (À0.6% per year; P < 0.001), middle-aged men and women (À1.1% to À1.4% per year; P < 0.001), and older men and women (À2.2% to À2.4% per year; P ≤ 0.053). These changes were mainly related to decrements in torque at P max at early age and to decrements in both torque and velocity at P max at older age. BMI increased among young and middle-aged adults (0.2% to 0.5% per year; P < 0.001), which led to greater declines in relative P max in those groups. S/T 0 , that is, the linear slope of the T-V relationship relative to maximal torque, exhibited a significant decline over time (À0.10%T 0 •rad•s À1 per year; P < 0.001), which was significant among middle-aged men and old men and women (all P < 0.05). Annual changes in PAL index were significantly associated to annual changes in P max (P = 0.017), so the overall decline in P max was slightly attenuated in the adjusted model (À5.26 vs. À5.05 W per year; both P < 0.001). Conclusions P max decreased in young, middle-aged, and older adults after a 10-year follow-up. The early declines in P max seemed to coincide with declines in force, whereas the progressive decline at later age was associated with declines in both force and velocity. A progressively blunted ability to produce force, especially at moderate to high movement velocities, should be considered a specific hallmark of aging.

Background Good sit-to-stand (STS) performance is an important factor in maintaining functional independence. This study investigated whether free-living STS transition volume and intensity, assessed by a thigh-worn accelerometer, is associated with characteristics related to functional independence. Methods Free-living thigh-worn accelerometry was recorded continuously for 3–7 days in a population-based sample of 75-, 80-, and 85-year-old community-dwelling people (479 participants; women n = 287, men n = 192). The records were used to evaluate the number and intensity (angular velocity of the STS phase) of STS transitions. Associations with short physical performance battery (SPPB), 5-times-sit-to-stand test (5×STS), isometric knee extension force, self-reported fear of falls, and self-reported difficulty in negotiating stairs were also assessed. Results The number of STS transitions, mean and maximal angular velocity were lower in older age groups (p &lt; .05). All variables were higher in men than in women (p &lt; .001) and were positively associated with SPPB total points, knee extension force (r ranged from 0.18 to 0.39, all p &lt; .001) and negatively associated with 5×STS (r = −0.13 – −0.24, all p &lt; .05), lower extremity functional limitations (p &lt; .01), fear of falls (p &lt; .01), and stair negotiation difficulties (p &lt; .01). Conclusions Free-living STS characteristics were related to lower-extremity performance, lower extremity functional limitations, self-reported fear of falls, and stair negotiation difficulties, which can be a sensitive indicator of impending functional decline. Moreover, STS transitions may provide an indicator of adequacy of lower-limb muscle strength among older individuals.

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